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  • 51.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Keshavarzi, Neda
    Department of Materials and Environmental Chemistry, Stockholm University.
    Shakarova, Dilshod
    Department of Materials and Environmental Chemistry, Stockholm University.
    Cheung, Ocean
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, L.M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Aluminophosphate monoliths with high CO2-over-N2 selectivity and CO2 capture capacity2014Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, nr 99, s. 55877-55883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Monoliths of microporous aluminophosphates (AlPO4-17 and AlPO4-53) were structured by binder-free pulsed current processing. Such monoliths could be important for carbon capture from flue gas. The AlPO4-17 and AlPO4-53 monoliths exhibited a tensile strength of 1.0 MPa and a CO2 adsorption capacity of 2.5 mmol g-1 and 1.6 mmol g-1, respectively at 101 kPa and 0°C. Analyses of single component CO2 and N2 adsorption data indicated that the AlPO4-53 monoliths had an extraordinarily high CO2-over-N2 selectivity from a binary gas mixture of 15 mol% CO2 and 85 mol% N2. The estimated CO2 capture capacity of AlPO4-17 and AlPO4-53 monoliths in a typical pressure swing adsorption (PSA) process at 20°C was higher than that of the commonly used zeolite 13X granules. Under cyclic sorption conditions, AlPO4-17 and AlPO4-53 monoliths were regenerated by lowering the pressure of CO2. Regeneration was done without application of heat, which would regenerate them to their full capacity for CO2 adsorption.

  • 52.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kocjan, Andraz
    The hydrolysis of AlN powder: powerful tool in advanced materials engineering2014Konferensbidrag (Refereegranskat)
  • 53.
    Akhtar, Farid
    et al.
    School of Material Science and Engineering, University of Science and Technology, Bejing.
    Lian, Yudong D.
    School of Material Science and Engineering, University of Science and Technology, Bejing.
    Islam, Syed Humail
    School of Material Science and Engineering, University of Science and Technology, Bejing.
    Guo, Shiju
    School of Material Science and Engineering, University of Science and Technology, Bejing.
    A new kind of age hardenable martensitic stainless steel with high strength and toughness2007Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 34, nr 4, s. 285-289Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Following analysis of typical age hardenable martensitic stainless steels, a new kind of maragingstainless was developed. The new maraging stainless steel showed high strength, ultimate tensilestrength (UTS) 5 1670 MPa, high toughness, K IC 5 83·9 MPa m1/2 and hardness as high as 478 HVin the age hardened condition. Microstructural study with an optical and transmission electron microscope revealed the typical microstructure of age hardenable stainless steel containing lathmartensite and precipitates. TixNi precipitates were identified by transmission electron microscopy, which were responsible for the increase in mechanical properties after age hardening. The results of natural salt spray test showed that the corrosion resistance of new maraging stainless steel approached to the corrosion resistance of 304L stainless steel.

  • 54.
    Akhtar, Farid
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Liu, Qingling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergstroem, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Erratum: Strong and binder free structured zeolite sorbents with very high CO2-over-N-2 selectivities and high capacities to adsorb CO2 rapidly (vol 5, pg 7664, 2012)2012Ingår i: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 5, nr 12, s. 9947-Artikel i tidskrift (Refereegranskat)
  • 55.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Liu, Qingling
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Strong and binder free structured zeolite sorbents with very high CO 2-over-N 2 selectivities and high capacities to adsorb CO 2 rapidly2012Ingår i: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 5, nr 6, s. 7664-7673Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mechanically strong monoliths of zeolite NaKA with a hierarchy of pores displayed very high CO2-over-N2 selectivity. The zeolite monoliths were produced by pulsed current processing (PCP) without the use of added binders and with a preserved microporous crystal structure. Adsorption isotherms of CO2 and N2 were determined and used to predict the co-adsorption of CO2 and N2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic adsorbents of NaKA could reach an extraordinarily high CO2-over-N2 selectivity in a binary mixture with a composition similar to flue gas (15 mol% CO2 and 85 mol% N2 at 25 °C and 101 kPa). Structured NaKA monoliths with a K+ content of 9.9 at% combined a CO2-over-N2 selectivity of >1100 with a high CO2 adsorption capacity (4 mmol g−1) and a fast adsorption kinetics (on the order of one minute). Estimates of a figure of merit (F) based on IAST CO2-over-N2 selectivity, and time-dependent CO2 uptake capacity, suggest that PCP-produced structured NaKA with a K+ content of 9.9 at% offers a performance far superior to 13X adsorbents, in particular at short cycle times.

  • 56.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Liu, Qingling
    Hedin, Niklas
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Structured zeolite adsorbents with very high CO2-over-N2 selectivity and high capacity.2012Konferensbidrag (Refereegranskat)
  • 57.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials and Environmental Chemistry, Stockholm University.
    Ogunwumi, Steven
    Crystalline Materials Research, Corning Incorporated, Corning, New York, USA..
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
    Thin zeolite laminates for rapid and energy-efficient carbon capture2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikel-id 10988Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin, binder-less zeolite NaX laminates, with thicknesses ranging between 310 to 750 μm and widths exceeding 50 mm and biaxial tensile strength in excess of 3 MPa, were produced by pulsed current processing. The NaX laminates displayed a high CO2 adsorption capacity and high binary CO2-over-N2 and CO2-over-CH4 selectivity, suitable for CO2 capture from flue gas and upgrading of raw biogas. The thin laminates displayed a rapid CO2 uptake; NaX laminates with a thickness of 310 μm were saturated to 40% of their CO2 capacity within 24 seconds. The structured laminates of 310 μm thickness and 50 mm thickness would offer low pressure drop and efficient carbon capture performance in a laminate-based swing adsorption technology.

  • 58.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    All-Zeolite Membranes2010Konferensbidrag (Refereegranskat)
  • 59.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Wirawan, Kompiang
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    PCP procesing of Zeolite supports for all-zeolite membranes2011Konferensbidrag (Refereegranskat)
  • 60.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Rehman, Yaser
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    A study of the sintering of diatomaceous earth to produce porous ceramic monoliths with bimodal porosity and high strength2010Ingår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 201, nr 3, s. 253-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diatomite powder, a naturally occurring porous raw material, was used to fabricate ceramic materials with bimodal porosity and high strength. The effect of the sintering temperature on the density and porosity of dry pressed diatomite green bodies was evaluated using mercury porosimetry and water immersion measurements. It was found that the intrinsic porosity of the diatomite particles with a pore size around 0.2 µm was lost at sintering temperatures above 1200 °C. Maintaining the sintering temperature at around 1000 °C resulted in highly porous materials that also displayed a high compressive strength. Microstructural studies by scanning electron microscopy and energy-dispersive X-ray analysis suggested that the pore collapse was facilitated by the presence of low melting impurities like Na2O and K2O.

  • 61.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Shakarova, Dilshod
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Department of Materials and Environmental Chemistry, Stockholm University.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Department of Materials and Environmental Chemistry, Stockholm University.
    Structuring of AlPOs and zeolite powders into hierarchically porous CO2 adsorbents2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The use of porous materials in industrially important gas separation and purification applications, e.g. CO2 separation from flue gas and purification of biogas require that the porous material is assembled into mechanically strong and hierarchically porous macroscopic structures. Hierarchically porous structured monoliths[1-2] and laminates[3] have been reported with high performance for CO2 separation from N2. Such structured monoliths and laminates with tailored porosity at various length scales combined high volumetric efficiency, good mass and heat transfer, rapid adsorption/desorption kinetics and structural integrity[1-3]. Here, we demonstrate a binder-less approach[4,5] to consolidate 8-ring window zeolite and aluminophosphate (AlPO4’s) powders into mechanically strong monoliths with a high CO2 uptake capacity and CO2-over-N2 selectivity, and a rapid adsorption and release kinetics. Adsorption isotherms of CO2 and N2 were used to predict the co-adsorption of CO2 and N2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic zeolite adsorbents of partially K exchanged NaA could reach an extraordinarily high CO2-over-N2 selectivity in a binary mixture with a composition similar to flue gas[1]. Furthermore, zeolite monoliths showed high tensile strength of 2.2 MPa. AlPO-17 and AlPO-53 monoliths were consolidated by the binder-less process with a tensile strength over 1 MPa. AlPO-17 monoliths showed high CO2 adsorption capacity while AlPO-53 exhibited high CO2-over-N2 selectivity. Cyclic CO2 adsorption tests showed that AlPO4 monoliths required less energy for regeneration compared to zeolite and could be regenerated to their full capacity at low pressures

  • 62.
    Akhtar, Farid
    et al.
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Shiju, Guo
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Effect of microstructure on the properties of pulse current sintered bimodal hardmetals2008Ingår i: Proceedings of the 7th International Conference on Tungsten, Refractory and Hardmaterials, 2008, s. 41-48Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study deals with the pulse current processing, microstructure and mechanical properties of WC-20wt%(W,Ti,Ta)C-6wt%Co cemented carbides. The conventional WC particles of 4μm size and ultrafine particles of 200nm were introduced in the system with varying ratio to synthesize bimodal hardmetals. Pulse current processing effectively controlled the grain size of WC particles in the presence of (W,Ti,Ta)C phase to synthesize fine microstructure. The microstructure of pulse current consolidated hardmetals was sensitive to the ratio of conventional WC particles to ultrafine WC particles. The ratio of conventional WC particles to ultrafine WC particles was very effective to enhance the mechanical properties of bimodal hardmetals. Hardness of bimodal hardmetals increased with decrease in the ratio of conventional WC particles to ultrafine WC carbide particles. The bending strength showed the similar trend of the hardness. The fracture behavior showed transgranular fracture mode as a dominant fracture mechanism in bimodal hardmetals with varying ratio of conventional WC particles to ultrafine WC particles.

  • 63.
    Akhtar, Farid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sjöberg, Erik
    Korelskiy, Danil
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015Ingår i: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, s. 206-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    raded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H2 separation factor of 12 at 0 °C and a CO2 permeance of 21.3×10-7 mol m-2 s-1 Pa-1 for an equimolar CO2/H2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 64.
    Akhtar, Farid
    et al.
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Vasiliev, Petr
    Stockholm University, Department of Materials and Environmental Chemistry, Arrhenius Lab.
    Bergström, Lennart
    A novel method to produce hierarchically porous monoliths from nanoporous powders2008Konferensbidrag (Refereegranskat)
  • 65.
    Akhtar, Farid
    et al.
    Materials Chemistry Research Group, Arrhenius Laboratory, Department of Physical, Inorganic and Structural Chemistry, Stockholm University.
    Vasiliev, Petr O
    Materials Chemistry Research Group, Arrhenius Laboratory, Department of Physical, Inorganic and Structural Chemistry, Stockholm University.
    Bergström, Lennart
    Materials Chemistry Research Group, Arrhenius Laboratory, Department of Physical, Inorganic and Structural Chemistry, Stockholm University.
    Hierarchically porous ceramics from diatomite powders by pulsed current processing2009Ingår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 92, nr 2, s. 338-343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hierarchically porous ceramic monoliths have been fabricated by pulsed current processing (PCP) of diatomite powders. The partial sintering behavior of the porous diatomite powders during PCP or spark plasma sintering was evaluated at temperatures between 600° and 850°C. Scanning electron microscopy and mercury porosimetry measurements showed that the PCP method was able to bond the diatomite powder together into relatively strong monoliths without significantly destroying the internal pores of the diatomite powder at a temperature range of 700°–750°C. Little fusion at the particle contact points occurred at temperatures below 650°C while the powder showed partial melting and collapse of both the interparticle pores and the internal structure at temperatures above 800°C.

  • 66.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High temperature tribology of CuMoTaWV high entropy alloy2019Ingår i: Wear of Materials, 2019, Vol. 426-427, s. 412-419Konferensbidrag (Refereegranskat)
    Abstract [en]

    An equiatomic high entropy alloy (HEA) CuMoTaWV was designed for room temperature to high temperature wear applications using spark plasma sintering of elemental powder mixture at 1400 °C. The sintered solid solution showed uniform distribution of elements in a BCC high entropy alloy phase along with V rich solid solution phase with an average hardness of 600 Hv and 900 Hv, respectively. Room temperature (RT) dry sliding wear tests, against alloy steel (700–880 Hv) for 200 m sliding distance at 5 N normal load, showed negligible wear of 5 × 10−7 mm/N m and a coefficient of friction (COF) of 0.5. Sliding wear characterization of sintered CuMoTaWV alloy against Si3N4 (1550 Hv) counter body from RT to 600 °C showed an increasing average COF of 0.45–0.67 from RT to 400 °C and then reducing to 0.54 at 600 °C. The wear rate was found to be lower at RT (4 × 10−3 mm3/N m) and 400 °C (5 × 10−3 mm3/N m), and slightly higher at 200 °C (2.3 × 10−2 mm3/N m) and 600 °C (4.5 × 10−2 mm3/N m). The CuMoTaWV alloy showed wear mechanisms specific to the test temperatures. The wear of CuMoTaWV alloy was governed by adhesive wear at RT and 200 °C and oxidative wear at 400 °C and 600 °C. The analyses of wear surfaces showed that the low wear rate at RT was due to the high hardness of the HEA, presence of V rich zones and formation of W and Ta tribofilm. At 400 °C, the formation of CuO tribolayer reduced the wear and hindered oxidation of wear track. At 600 °C, the wear rate increased due to oxidation of Cu, Ta and W. Moreover, the formation of lubricating elongated magneli phase V2O5 in V rich regions of CuMoTaWV alloy reduced the COF to 0.54.

  • 67.
    Alvi, Sajid
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    High temperature tribology of polymer derived ceramic composite coatings2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 15105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polymer derived ceramic (PDC) composite coatings were deposited on AISI 304 substrates using siloxane based preceramic polymer polymethlysilsquioxane (PMS) and ZrSi2 as active filler or Ag as passive filler. The tribological performance of the composite coatings was evaluated at room temperature and moderately high temperatures (150 °C, 200 °C, 300 °C and 400 °C). The composite coatings showed low coefficient of friction (COF), µ, from 0.08 to 0.2 for SiOC-ZrSi2 composite coatings, and from 0.02 to 0.3 for SiOC-Ag composite coatings, at room temperature with increasing normal load from 1 to 5 N. High temperature tribology tests showed high COF values from 0.4 to 1 but low wear for SiOC-ZrSi2 coating, and low COF from 0.2 to 0.3 for SiOC-Ag coatings at lower temperature ranges. Low load friction tests at room temperature showed negligible wear in SiOC-ZrSi2 coatings, suggesting good wear resistant and lubricating properties due to formation of t-ZrO2 and carbon. Low COF and high amount of wear was observed in SiOC-Ag composite coatings at room temperature due to high ductility of Ag and smearing of wear debris in the wear track. The coatings and wear tracks were characterized to evaluate the lubrication and wear behavior.

  • 68.
    Alvi, Sajid Ali
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ghamgosar, Pedram
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Rigoni, Federica
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Vomiero, Alberto
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Adaptive nanolaminate coating by atomic layer deposition2019Ingår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atomic layer deposition (ALD) was used to deposit ZnO/Al2O3/V2O5 nanolaminate coatings to demonstrate a coating system with temperature adaptive frictional behaviour. The nanolaminate coating exhibited excellent conformity and crack-free coating of thickness 110 nm over Inconel 718 substrate. The ALD trilayer coating showed a hardness and elastic modulus of 12 GPa and 193 GPa, respectively. High-temperature tribology of the nanolaminate trilayer was tested against steel ball in dry sliding condition at 25 °C (room temperature, RT), 200 °C, 300 °C, and 400 °C. It was found that the nanolaminate coating showed a low coefficient of friction (COF) and wear rate at RT and 300 °C. The trilayer coating was found intact and stable at all temperatures during the friction tests. The adaptability of nanolaminate coating with the temperature was verified by performing the cyclic friction test at 300 °C and RT. The low COF and wear rate had been attributed to the (100) and (002) basal plane sliding of ZnO top layer, and the interlayer sliding of weakly bonded planes parallel to (001) plane in V2O5 bottom layer. Furthermore, even after the removal of ZnO coating during the tribotest, the bottom V2O5 layer coating stabilized the COF and wear rate at RT and 300 °C.

  • 69. Andersson, Linnéa
    et al.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Jones, C.
    Knackstedt, M.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Tuning the permeability to fluid flow in macroporous Al2O3: A 3D study with X-ray micro-computed tomography.2010Konferensbidrag (Refereegranskat)
  • 70. Andersson, Linnéa
    et al.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Jones, C.
    Knackstedt, M.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Zeolite coated alumina foam for CO2 capture2011Konferensbidrag (Refereegranskat)
  • 71.
    Andersson, Linnéa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Akhtar, Farid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Ojuva, Arto
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Colloidal processing and CO2-capture performance of hierarchically porous Al2O3-zeolite 13X composites2012Ingår i: Journal of Ceramic Science and Technology, ISSN 2190-9385, Vol. 3, nr 1, s. 9-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hierarchically porous composites for CO2-capture have been produced by coating the inner walls of foam-like macroporous alumina monoliths, produced by templated synthesis, with microporous zeolite 13X particles. Homogeneous and dense coatings of the particulate adsorbent were obtained when the impregnation process was performed at a pH above 9. At this pH-level the colloidally stable suspensions of the negatively charged zeolite 13X particles could fill all the voids of the highly connected pore space of the alumina supports and attach to the monolith walls, which had been pre-coated with poly(ethylene imine). A CO2-uptake as high as 5 mmol CO2/g zeolite 13X was achieved for alumina-zeolite 13X composites through minimisation of the added inorganic binder, kaolin, to only 3.0 wt% with respect to zeolite content, and through optimisation of the thermal treatment.

  • 72.
    Askari, SJ
    et al.
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Akhtar, Farid
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Chen, GC
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    He, Q
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Wang, FY
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Meng, XM
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Lu, FX
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Synthesis and characterization of nano-crystalline CVD diamond film on pure titanium using Ar/CH 4/H 2 gas mixture2007Ingår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 61, nr 11-12, s. 2139-2142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Titanium and Ti alloys have poor tribological properties and deposition of a well adherent diamond coating is a promising way to solve this problem. But diamond film deposition on pure titanium and Ti alloys is always difficult due to the high diffusion coefficient of carbon in Ti, the large mismatch in their thermal expansion coefficients, the complex nature of the interlayer formed during diamond deposition, and the difficulty of achieving very high nucleation density. A nano-crystalline diamond (NCD) film can resolve Ti and Ti alloys weak tribological performance due to its smooth surface. A well-adhered NCD film was successfully deposited on pure Ti substrate by using a microwave plasma assisted chemical vapor deposition (MWPCVD) system in the environment of Ar, CH4 and H2 gases at a moderate temperature. Detailed experimental results on the preparation, characterization and successful deposition of the NCD film on pure Ti are discussed

  • 73.
    Askari, SJ
    et al.
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Akhtar, Farid
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Islam, S.H.
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Qi, H
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Tang, WZ
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Lu, FX
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Two-step growth of high-quality nano-diamond films using CH 4/H 2 gas mixture2007Ingår i: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 81, nr 5, s. 713-717Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diamond films with fine grain size and good quality were successfully deposited on pure titanium substrate using a novel two-step growth technique in microwave plasma-assisted chemical vapor deposition (MWPCVD) system. The films were grown with varying the methane (CH4) concentration at the stage of bias-enhanced nucleation (BEN) and nano-diamond film deposition. It was found that nano-diamond nuclei were formed at a relatively high methane concentration, causing a secondary nucleation at the accompanying growth step. Nano-diamond film deposition on pure titanium was always very hard due to the high diffusion coefficient of carbon in Ti, the big difference between thermal expansion coefficients of diamond and Ti, the complex nature of the interlayer created during diamond deposition, and the difficulty in achieving very high nucleation density. A smooth and well-adhered nano-diamond film was successfully obtained on pure Ti substrate. Detailed experimental results on the synthesis, characterization and successful deposition of the nano-diamond film on pure Ti are discussed

  • 74.
    Askari, SJ
    et al.
    Institute of Manufacturing Engineering, PNEC, National University of Sciences and Technology (NUST), Karachi.
    Chen, GC
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Akhtar, Farid
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Lu, FX
    Department of High Tech Thin Films, School of Materials Science and Engineering, University of Science and Technology Beijing.
    Adherent and low friction nano-crystalline diamond film grown on titanium using microwave CVD plasma2008Ingår i: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 17, nr 3, s. 294-299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of titanium alloys for aerospace and biomedical applications could increase if their tribological behavior was improved. The deposition of an adherent diamond coating can resolve this issue. However, due to the different thermal expansion coefficients of the two materials, it is difficult to grow adherent thin diamond layers on Ti and its metallic alloys. In the present work microwave plasma chemical vapor deposition (MWPCVD) was used to deposit smooth nano-crystalline diamond (NCD) film on pure titanium substrate using Ar, CH4 and H2 gases at moderate deposition temperatures. Of particular interest in this study was the exceptional adhesion of approximately 2 μm-thick diamond film to the metal substrate as observed by indentation testing up to 150 kg load. The friction coefficient, which was measured with a cemented carbide ball of 10 mm diameter with 20 N load, was estimated to be around 0.04 in dry air. Morphology, surface roughness, diamond crystal orientation and quality were obtained by characterizing the sample with field emission electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy, respectively.

  • 75.
    Askari, Syed Jawid
    et al.
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Lv, Fanxiu
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Akhtar, Farid
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Wang, Fengying
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    He, Qi
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Zhou, Zuyuan
    University of Science and Technology Beijing, School of Materials Science and Engineering.
    Nanodiamond films deposited at moderate temperature on pure titanium substrate pretreated by ultrasonic scratching in diamond powder suspension2006Ingår i: Journal of University of Science and Technology Beijing, Mineral, Metallurgy, Material, Vol. 13, nr 6, s. 542-545Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanocrystalline diamond (NCD) film deposition on pure titanium and Ti alloys is extraordinarily difficult because of the high diffusion coefficient of carbon in Ti, the large mismatch in their thermal expansion coefficients, the complex nature of the interlayer formed during diamond deposition, and the difficulty to achieve very high nucleation density. In this investigation, NCD films were successfully deposited on pure Ti substrate by using a novel substrate pretreatment of ultrasonic scratching in a diamond powder-ethanol suspension and by a two-step process at moderate temperature. It was shown that by scratching with a 30-μm diamond suspension for 1 h, followed by a 10-h diamond deposition, a continuous NCD film was obtained with an average grain size of about 200 nm. Detailed experimental results on the preparation, characterization, and successful deposition of the NCD films on Ti were discussed

  • 76.
    Avila, Marta
    et al.
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Burks, Terrance
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Göthelid, Mats
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Lansåker, Pia C
    Department of Engineering Sciences, The Ångström Laboratory, Uppsala University.
    Toprak, Muhammet S
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Muhammed, Mamoun
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Uheida, Abdusalam
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Surface functionalized nanofibers for the removal of chromium (VI) from aqueous solutions2014Ingår i: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, s. 201-209Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (>90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.

  • 77.
    Binbin, Song
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Peizhonga, Feng
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Jianzhong, Feng
    State Key Laboratory of Porous Metal Materials, Northwest Institute for Non-ferrous Metal Research, Xi’an.
    Yuan, Ge
    State Key Laboratory of Porous Metal Materials, Northwest Institute for Non-ferrous Metal Research, Xi’an.
    Guangzhi, Wu
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Xiaohong, Wang
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Oxidation properties of self-propagating high temperature synthesized niobium disilicide2014Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 85, s. 311-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    NbSi2 monoliths were prepared by self-propagating high temperature synthesis (SHS) and hot pressing (HP) and their oxidation behavior was investigated at various temperatures (823 K to 1123 K) in air. The combustion mode of SHS reaction was steady state combustion, and the combustion product was single-phase NbSi2. Oxidation studies show that the highest mass gain was 0.95675 kg m-2 at 1023 K. In cyclic oxidation, the oxidation rate was reduced and the mass gain was only 0.15507 kg m-2. A dense protective amorphous SiO2 scale formed at 823 K and 923 K whereas a porous multilayer SiO2 and α/β-Nb2O5 oxide scales formed at and above 1023 K and spalled off. Pest oxidation of NbSi2 monoliths was not observed in hot pressed NbSi2 monoliths

  • 78.
    Bladek, Kamila J
    et al.
    Department of Chemistry, University of Calgary, Calgary, Canada.
    Reid, Margaret E
    Department of Chemistry, University of Calgary, Calgary, Canada.
    Nishihara, Hirotomo
    Department of Chemistry, University of Calgary, Calgary, Canada. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gelfand, Benjamin S.
    Department of Chemistry, University of Calgary, Calgary, Canada.
    Shimizu, George K. H.
    Department of Chemistry, University of Calgary, Calgary, Canada.
    Microsphere Assemblies via Phosphonate Monoester Coordination Chemistry2018Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, nr 7, s. 1533-1538Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By complexing a bent phosphonate monoester ligand with cobalt(II), coupled with in situ ester hydrolysis, coordination microspheres (CALS=CALgary Sphere) are formed whereas the use of the phosphonic acid directly resulted in a sheet-like structure. Manipulation of the synthetic conditions gave spheres with different sizes, mechanical stabilities, and porosities. Time-dependent studies determined that the sphere formation likely occurred through the formation of a Co2+ and ligand chain that propagates in three dimensions through different sets of interactions. The relative rates of these assembly processes versus annealing by ester hydrolysis and metal dehydration determine the growth of the microspheres. Hardness testing by nanoindentation is carried out on the spheres and sheets. Notably, no templates or capping agents are employed, the growth of the spheres is intrinsic to the ligand geometry and the coordination chemistry of cobalt(II) and the phosphonate monoester.

  • 79.
    Burks, T
    et al.
    Department of Chemical Engineering and Technology, Royal Institute of Technology.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Saleemi, M.
    Division of Functional Materials, Royal Institute of Technology (KTH).
    Kiros, Y.
    Department of Chemical Engineering and Technology, Royal Institute of Technology.
    ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)2015Ingår i: Journal of Environmental and Public health, ISSN 1687-9805, E-ISSN 1687-9813, Vol. 2015, artikel-id 687094Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI) as a prime step for the purification of water. The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developed architecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-L-lactide nanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV) in aqueous solution under a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps. The adsorption of Cr(VI) species in solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofiber nanocomposite. The adsorption and desorption of Cr(VI) species were more likely due to the electrostatic interaction between ZnO and Cr(VI) ions as a function of pH. The adsorption and desorption experiments utilizing the ZnO-PLLA nanofiber nanocomposite have appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI) species.

  • 80.
    Burks, Terrance
    et al.
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Avila, Marta
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Göthelid, Mats
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Lansåker, Pia C
    Department of Engineering Sciences, The Ångström Laboratory, Uppsala University.
    Toprak, Muhammet S
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Muhammed, Mamoun
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Uheida, Abdusalam
    Department of Materials and NanoPhysics, Royal Institute of Technology (KTH).
    Studies on the adsorption of chromium (VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles2014Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 425, s. 36-43Artikel i tidskrift (Refereegranskat)
  • 81.
    Cai, Xiaoping
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou .
    Liu, Yanan
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, .
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Jiao, Xinyang
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Fabrication of Highly Porous CuAl Intermetallic by Thermal Explosion Using NaCl Space Holder2018Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, nr 10, s. 2173-2178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high-porosity CuAl-based intermetallic compound with composition Cu-50 at.% Al has been successfully prepared by thermal explosion (TE) using NaCl as space holder. The results showed that the NaCl particles were completely removed from the green compact by water leaching. The temperature of the specimen during the TE and the evolution of the porous microstructure were investigated. The TE was ignited at 560°C, and the specimen temperature increased to 775°C in 3 s, resulting in formation of intermetallic CuAl and CuAl2 phases in the final product. A porous CuAl-based intermetallic compound with up to 62 vol.% open porosity was produced when adding 60 vol.% NaCl. The compound exhibited a bimodal pore size structure, including large pores (200 μm to 300 μm) that replicated the NaCl particles and small pores (5 μm to 10 μm) interspersed in the pore walls. Moreover, the large pores were interconnected by channels and formed an open CuAl-based intermetallic cellular structure, having great potential for use in heat exchange and filtration applications.

  • 82.
    Cai, Xiaoping
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, P.R. China.
    Liu, Yanan
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, P.R. China.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, P.R. China.
    Jiao, Xinyang
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, P.R. China.
    Wang, Jianzhong
    State Key Laboratory of Porous Metal Materials, Northwest Institute for Non-Ferrous Metal Research, Xi’an, P.R. China.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, P.R. China.
    Oxidation Resistance of Highly Porous Fe-Al Foams Prepared by Thermal Explosion2018Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, nr 8, s. 3683-3691Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Open-cell Fe-Al intermetallic foams were successfully prepared by a simple and energy-saving thermal explosion (TE) process. The effects of the Fe/Al molar ratio (Fe-(40–50) at. pct Al) and thermal treatment temperature on the TE temperature profile, phase composition, pore characteristics, and oxidation resistance of the prepared foams were investigated. The results showed that the Al content significantly influenced the ignition (Tig) and combustion (Tc) temperatures of the TE process; in particular, as the Al content decreased, Tig increased gradually from 623 °C to 636 °C and Tc decreased from 1059 °C to 981 °C. FeAl was identified as the dominant phase in the thermally treated foams. The Fe-Al intermetallic foams displayed an open porosity of 60 vol pct, with pores connected with each other to form an open pore structure. The formation of the pores was attributed to the expansion of interparticle pores in the pressed body during the TE reaction. X-ray photoelectron spectroscopy analysis of the Fe-50Al foam showed that the Al 2p and O 1s binding energies were 74.5 eV and at 531.4 eV, respectively. The formation of a surface alumina layer in the early stages of the oxidation process resulted in the parabolic oxidation rate law, and the Fe-50Al foams exhibited an excellent resistance to oxidation at 650 °C in air. These results suggest that the synthesized Fe-Al foams represent promising materials for applications involving an oxidizing environment and high temperatures.

  • 83.
    Ciurans Oset, Marina
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nordin, Jan
    Akzo Nobel Pulp and Performance Chemicals AB.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Processing of Macroporous Alumina Ceramics Using Pre-Expanded Polymer Microspheres as Sacrificial Template2018Ingår i: Ceramics, ISSN 2571-6131, Vol. 1, nr 2, s. 329-342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shaped porous ceramics have proven to be the most adapted materials for several industrial applications, both at low and high temperatures. Recent research has been focused on developing shaping techniques, allowing for a better control over the total porosity and the pores characteristics. In this study, macroporous alumina foams were fabricated by gel-casting using pre-expanded polymeric microspheres with average sizes of 40 μm, 20 μm, and 12 μm as sacrificial templates. The gel-casting method, as well as the drying, debinding, and presintering conditions were investigated and optimized to process mechanically strong and highly porous alumina scaffolds. Furthermore, a reliable model relating the amount of pre-expanded polymeric microspheres and the total porosity of the presintered foams was developed and validated by mercury intrusion porosimetry measurements. The electron microscopy investigation of the presintered foams revealed that the size distribution and the shape of the pores could be tailored by controlling the particle size distribution and the shape of the wet pre-expanded microspheres. Highly uniform and mechanically stable alumina foams with bimodal porosity ranging from 65.7 to 80.2 vol. % were processed, achieving compressive strengths from 3.3 MPa to 43.6 MPa. Given the relatively open pore structure, the pore size distribution, the presintered mechanical strength, and the high porosity achieved, the produced alumina foams could potentially be used as support structures for separation, catalytic, and filtration applications.

  • 84.
    Du, Xueli
    et al.
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Qin, Mingli
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Akhtar, Farid
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Humail, Islam S
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Qu, Xuanhui
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Study of rare-earth oxide sintering aid systems for AlN ceramics2007Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 460-461, s. 471-474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, effects of Y2O3 and Dy2O3 sintering aid systems on density and thermal conductivity of AlN ceramics sintered at low temperature were investigated. The AlN powder synthesized by self-propagating high-temperature synthesis (SHS) was mixed individually with six different sintering aids, which were Y2O3, Dy2O3, CaF2–Y2O3, CaF2–Dy2O3, CaF2–Li2CO3–Y2O3 and CaF2–Li2CO3–Dy2O3, and then fabricated by employing press forming technique. The specimens were sintered at 1650 °C in nitrogen atmosphere at atmospheric pressure for 4 h. X-ray diffraction (XRD) was used to identify the secondary phases. The microstructure of the specimen was observed by scanning electron microscopy (SEM). The thermal diffusivity at room temperature was measured by a laser flash technique. Density of sintered specimen was measured by Archimedes displacement method. The result reveals that the density and thermal conductivity of AlN ceramics sintered with one component sintering aids were lower than those of sintered with multiple components sintering aids. The thermal conductivity of AlN ceramics sintered with CaF2–Li2CO3–Y2O3 and CaF2–Dy2O3 were 141 W m−1 K−1 and 142 W m−1 K−1, which were higher than that of any others.

  • 85.
    Feng, Pei Zhong
    et al.
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Qu, Xuan Hui
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Wang, Xiao Hong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Study on Oxidation Behavior of (W, Mo) Si2 Powders in Air at 400, 500 and 600textordmasculineC2007Ingår i: Progress in powder metallurgy: proceedings of the 2006 Powder Metallurgy World Congress & Exhibition (PM 2006), held in Busan Exhibition & Convention Center (BEXCO), Busan, Korea, September 24 - 28, 2006 / [ed] Duk Yong Yoon; Suk-Joong L. Kang; Kwang Yong Eun; Yong-Seog Kim, Uetikon-Zürich: Trans Tech Publications Inc., 2007, s. 1289-1292Konferensbidrag (Refereegranskat)
    Abstract [en]

    The oxidation of (W,Mo)Si2 powders has been examined at 400, 500 and 600°C for 12.0 hours in air. It was shown that the low temperature oxidation resistance of (W,Mo)Si2 was worse than that of MoSi 2, and they showed great changes in mass, volume and colour. At 500°C, the amount of volume expansion of (W,Mo)Si2 was as high as about 7-8 times and color changed from black to yellow after 4.0h with MoO 3, WO3, (W,Mo)O3 and amorphous SiO2 as main reaction products. It took about 8.0h to obtain the same results for MoSi2. The mass gain and oxidation rate were relatively slower at 400°C and 600°C than that at 500°C These were probably due to the lower oxidation rate at 400°C and the protective silica glass on surface of powders formed from the volatilization of MoO3, WO3 and (W,Mo)O3 at 600°C, which would restrain the diffusion of molybdenum from matrix to exterior and oxygen from outside to inside and the further accelerated oxidation.

  • 86.
    Feng, Peizhong
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Humail, Islam S
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Qu, Xuanhui
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Mechanically activated reactive synthesis of refractory molybdenum and tungsten silicides2008Ingår i: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 26, nr 3, s. 173-178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, processing of elemental powders mixtures was carried out by mechanical alloying (MA) and heat treatment in vacuum at 700–1000 °C for 1 h. The phase transformation of the powders was investigated by X-ray diffractometer (XRD). The results showed that mechanical alloying promoted the formation of a solid solution of elemental powders. The energy stored in the powders was increased as a result of exterior energy and the barrier energy of the formation of the compound could be exceeded easily. Intermetallics of MoSi2, WSi2, Mo5Si3, Mo3Si and SiC/MoSi2 composite powders were synthesized by mechanically activated reactive synthesis (MARS). The mechanically induced self-sustaining reaction was observed in MoSi2 and MoSi2 + 10 wt%SiC stoichiometry system. It has concluded that mechanically activated reactive synthesis is an effective method for the preparation of high melting-point refractory compounds.

  • 87.
    Feng, Peizhong
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology, Lahore.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Liu, Weisheng
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Wu, Jie
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Zhang, Shuai
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Qiang, Yinghuai
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Effect of diluent on the synthesis of molybdenum disilicide by mechanically-induced self-propagating reaction2010Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 494, nr 1-2, s. 301-304Artikel i tidskrift (Refereegranskat)
  • 88.
    Feng, Peizhong
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Liu, Weisheng
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Department of Materials and Environmental Chemistry, Stockholm University.
    Wu, Jie
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Niu, Jinan
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Qiang, Yinghuai
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Combustion synthesis of (Mo 1- xCrx) Si 2 (x= 0.00--0.30) alloys in SHS mode2012Ingår i: Advanced Powder Technology, ISSN 0921-8831, E-ISSN 1568-5527, Vol. 23, nr 2, s. 133-138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Combustion synthesis was adopted to successfully synthesize molybdenum–silicon–chromium (Mo−Si−Cr) alloys by the mode of self-propagating high-temperature synthesis (SHS). The experimental study of combustion synthesis of Mo−Si−Cr alloys was conducted on elemental powder compacts. Powder compacts with nominal compositions including MoSi2, (Mo0.95Cr0.05)Si2, (Mo0.90Cr0.10)Si2, (Mo0.85Cr0.15)Si2, (Mo0.80Cr0.20)Si2, (Mo0.75Cr0.25)Si2 and (Mo0.70Cr0.30)Si2 were employed in combustion synthesis experiments. The combustion mode, combustion temperature, flame-front propagation velocity and product structure were investigated. The results showed that Mo−Si−Cr alloys were synthesized by an unsteady state combustion mode with a spiral-trajectory reaction front. The peak combustion temperature reduced with the addition of Cr to Mo–Si system. The flame-front propagation velocity decreased with an increase in Cr content of the powder compact. The X-ray diffraction (XRD) results showed that the crystal structure of the combustion product changed from Cllb-type structure (Mo0.90Cr0.10)Si2 to C40-type structure (Mo0.85Cr0.15)Si2 with increase in Cr content of Mo–Cr–Si alloys. The intensities of diffraction peaks of the C40-type phase gradually increased with increase in Cr content.

  • 89.
    Feng, Peizhong
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Qu, Xuanhui
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Akhtar, Farid
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Du, Xueli
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Islam, Humail S
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Jia, Chengchang
    Institute of Powder Metallurgy, School of Materials Science and Engineering, University of Science and Technology, Beijing.
    Effect of the composition of starting materials of Mo--Si on the mechanically induced self-propagating reaction2008Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 456, nr 1-2, s. 304-307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of the raw materials composition of Mo–Si powders mixture on mechanical alloying has been investigated using a high-energy vibratory type ball-milling machine. The phase transformation of powders mixture is characterized by means of X-ray diffractometer. The results show that the molybdenum silicide is formed by the mechanically induced self-propagating reaction in relatively broad composition range from the molar ratio of Mo:1.5Si to Mo:2.5Si. As the content of silicon increases, the amount of critical stored energy for mechanically induced self-propagating reaction is increased, whereas the favorable Mo–Si reactive interface is decreased, and the difficulty of formation of Mo(Si) supersaturated solid solution is enhanced. These factors prolong the incubation period of mechanically induced self-propagating reaction from 60 to 130 min. Compared to stoichiometry of MoSi2, the excess amount of Mo acts as accelerant, and the redundant Si acts as diluting agent.

  • 90.
    Feng, Peizhong
    et al.
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Qu, Xuanhui
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Akhtar, Farid
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Islam, SH
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Self-propagating high temperature synthesis of MoSi 2 matrix composites2006Ingår i: Xiyou jinshu, ISSN 1001-0521, E-ISSN 1867-7185, Vol. 25, nr 3, s. 225-230Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis (SHS). Pure MoSi2 was obtained and a compound of MoSi2 and WSi2 was synthesized in the form of predominant solid solution (Mo, W)Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal CIIb MoSi2 and hexagonal C40 Mo(Si, Al)2. The (Mo, W)Si2-Mo(Si, Al)2-W(Si, Al)2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites.

  • 91.
    Gai, Fangyuan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Zhou, Tianlei
    Chemical & Materials Engineering Department, University of Nevada at Reno.
    Chu, Guang
    State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun.
    Li, Ye
    Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, Sichuan.
    Liu, Yunling
    State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun.
    Huo, Qisheng
    State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mixed anionic surfactant-templated mesoporous silica nanoparticles for fluorescence detection of Fe3+2016Ingår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, s. 508-514Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work demonstrates a novel method for the synthesis of large pore mesoporous silica nanoparticles (MSNs) with a pore diameter of 10.3 nm and a particle diameter of ∼50 nm based on the incorporation of mixed anionic surfactants sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulphate (SDS) as the template in the synthesis process. The dispersity, morphology, pore structure and size of mesoporous nanoparticles were adjusted by changing the molar ratio of two anionic surfactants, the concentration of the co-structure-directing agent (3-aminopropyltrimethoxysilane) and the reaction temperature. The results of synthesis experiments suggested that the formation of large pore MSNs involved a nucleation and growth process. MSNs were post-grafted with a Schiff base moiety for fluorescence sensing of Fe3+ in water. The applicability of functionalized MSNs was demonstrated by selective fluorescence detection of Fe3+ in aqueous media.

  • 92.
    Hooshmand, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nordin, Jan
    Luleå tekniska universitet, Extern.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Development of Ceramic Foams Containing Platinum Nanoparticles as the Catalyst2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The exhaust gases contribute significantly to global warming, but without a catalytic converter, exhaust gases would be even more polluting. Therefore, having a catalytic metal such as platinum nanoparticles on the surface of the pore walls in ceramic foams is a practical way to remove particulate matters and to have an effective catalytic converter in one. The porous structure of the foam filters the particulate matters and the high specific surface area of the Pt nanoparticles in the pores speed up the reactions. The role of platinum is to oxidize carbon monoxide (CO) and hydrocarbons (HC) to form carbon dioxide (CO2) and water vapor (H2O). In this study, The Pt nanoparticles were coated on the surface of the thermally expandable microspheres (Expancel). The Energy-dispersive X-ray spectroscopy (EDS) and Ultraviolet-visible spectroscopy (UV-Vis) confirmed the successful adsorption of Pt on the Expancel surface. In the next step, alumina foams prepared by the gel-casting technique using Pt-coated Expancels as the sacrificial template. The EDS confirmed the successful transfer of the Pt nanoparticles to the pore walls of the foam. The morphology and the porosity of the foams were studied using SEM and X-ray microtomography. Moreover, the compressive strength of the prepared sample in form of the green body, debinded and sintered was measured.  The results showed a promising way to design ceramic-based bi-functional foams for eliminating dust and converting harmful gases to nontoxic gases simultaneously.

  • 93.
    Hooshmand, Saleh
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nordin, Jan
    Akzo Nobel Pulp and Performance Chemicals AB, Expancel, Sundsvall, Sweden.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Porous alumina ceramics by gel casting: Effect of type of sacrificial template on the properties2019Ingår i: International Journal of Ceramic Engineering & Science, ISSN 2578-3270Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of type of sacrificial template on the processing and properties of porous alumina ceramics was investigated. Two templates, (a) hollow pre‐expanded polymer spheres (Expancel) and (b) dense glassy carbon, were used to prepare porous alumina ceramics by gel casting. The results showed that the burnout of sacrificial expandable polymer microspheres from alumina ceramics was 10 times faster than glassy carbon without compromising the compressive strength. Moreover, the effect of the size of the porous ceramic component during the burnout showed that the template decomposition and the escape of the formed gases took a longer time for the thicker specimens than the thinner one and it was significant in case of glassy carbon. It was found that the burnout of expandable microspheres could happen at a faster rate, and the time of the burnout cycle could be reduced significantly to save energy while keeping the mechanical strength twice as high than porous alumina ceramics after burnout of glassy carbon. Furthermore, the CO2 emissions during the burnout of sacrificial templates and the microstructure of the prepared porous alumina were compared for these two types of sacrificial templates. The prepared foams with pre‐expanded microspheres showed potential for being used in industrial applications, where the decreasing of the released gases is critical for saving time and energy for the fabrication of large ceramic parts.

  • 94.
    Humail, Islam S
    et al.
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Akhtar, Farid
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Askari, Syed Jawaid
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Tufail, M
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Qu, Xuanhui
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Tensile behavior change depending on the varying tungsten content of W--Ni--Fe alloys2007Ingår i: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 25, nr 5-6, s. 380-385Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tungsten heavy alloys (WHAs) are metal–metal composites consisting of nearly pure spherical tungsten particles embedded in a Ni–Fe–W or Ni–Co–W or Ni–Cu–W ductile matrix. In this dual phase alloy, there are several complicated relations between the ductile matrix and hard tungsten particles. The aim of this research was to examine the effect of varying tungsten content on the microstructure and mechanical properties of tungsten heavy alloys. The microstructural parameters (grain size, connectivity, contiguity and solid volume fraction) were measured and were found to have a significant effect on the mechanical properties of tungsten-based heavy alloys. The result shows that the binding strength between the W and the matrix phase has a major influence on the ductility of tungsten-based alloys. The larger this binding force is, the better the ductility is.

  • 95.
    Islam, Syed Humail
    et al.
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Qu, Xuan Hui
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Akhtar, Farid
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Feng, Pei Zhong
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    He, Xin Bo
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Microstructure and tensile properties of tungsten heavy alloys2007Ingår i: Progress in powder metallurgy: proceedings of the 2006 Powder Metallurgy World Congress & Exhibition (PM 2006), held in Busan Exhibition & Convention Center (BEXCO), Busan, Korea, September 24 - 28, 2006 / [ed] Duk Yong Yoon; Suk-Joong L. Kang; Kwang Yong Eun; Yong-Seog Kim, Uetikon-Zürich: Trans Tech Publications Inc., 2007, s. 561-564Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mechanical properties of tungsten heavy alloys are dependent on many factors including the purity of the raw materials, their tungsten content, manufacturing parameters and the microstructure of the final compact. The main object of this research was to examine the effect of sintering conditions (temperature and time) on the microstructure of tungsten heavy alloys and how the resulting modification of the microstructure can be used to optimize their mechanical properties. Alloys composed of 88%, 93% and 95% wt. of tungsten with the balance of Ni: Fe in the ratio of 7:3 were consolidated into green compacts. Samples of each of the three resulting alloys were sintered at different temperatures (1350°C,1450°C and 1500 0C) for different sintering holding times (3 and 30 minutes) in hydrogen atmosphere. Standard metallographic procedures were used to obtain SEM micrographs. The mechanical properties of tungsten heavy alloys were found to be dependent on the microstructural parameters such as W particle size, solid volume fraction, connectivity and w-w contiguity. It was shown that the mechanical properties of the alloys, and especially their ductility, are harmed when tungsten grains are contiguous.

  • 96.
    Jiang, Zhiwu
    et al.
    School of Materials Science and Engineering, China University of Mining & Technology, Xuzhou .
    Zhu, Gaoming
    School of Materials Science and Engineering, China University of Mining & Technology, Xuzhou .
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    In Situ Fabrication and Properties of 0.4MoB-0.1SiC-xMoSi2 Composites by Self-propagating Synthesis and Hot-press sintering2018Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, nr 1, s. 51-56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mo, Si and B4C powders were used to fabricate 0.4MoB-0.1SiC-xMoSi2 composites by self-propagating high-temperature synthesis (SHS) and hot pressing (HP). The effects of MoSi2 content (x=1, 0.75, 0.5 and 0.25) on phase composition, microstructure and properties of the composites were investigated. The results showed that the 0.4MoB-0.1SiC-xMoSi2 composite exhibited Vickers hardness of 10.7–15.2 GPa, bending strength of 337–827 MPa and fracture toughness of 4.9–7.0 MPa∙m1/2. The fracture toughness increased with the increasing volume fraction of MoB and SiC particles which were promoted by the toughening mechanisms, such as crack bridging, cracks deflection and crack branching. Moreover, the electrical resistivity showed an increasing trend with decreasing volume fraction of MoSi2.

  • 97.
    Jiao, Xinjang
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Kang, Xueqin
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Zhang, Laiqi
    School of Materials Science and Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Wang, Jianzhong
    State Key Laboratory of Porous Metal Materials, Northwest Institute for Non-ferrous Metal Research, Xi’an.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hierarchical porous TiAl3 intermetallics synthesized by thermal explosion with a leachable space-holder material2016Ingår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 181, s. 261-264Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Porous TiAl3 intermetallics were synthesized by thermal explosion (TE) reaction with NaCl as space holder material, from Ti-75Al at.% elemental powders. Results showed that the actual temperature of specimen climbed rapidly from 667 °C to 1106 °C. As a consequence, porous TiAl3 intermetallics with high open porosity (>80%) can be easily achieved when adding NaCl particles above 50 vol%. XRD patterns showed that only single-phase TiAl3 compound was synthesized via TE. Hierarchical porous TiAl3 materials displayed three pore structures, including large pores replicating from original NaCl particles, small pores among the skeletons, and tiny pores precipitated from particle skeletons. Moreover, porous TiAl3 intermetallics exhibited a uniform pore size distribution and formed an open-cellular structures allowing for the liquid-gas separation and filtration applications

  • 98.
    Jiao, Xinyang
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, China. School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, China.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, China.
    Wang, Jianzhong
    State Key Laboratory of Porous Metal Materials, Northwest Institute for Non-ferrous Metal Research, Xi'an, China.
    Ren, Xuanru
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, China.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Exothermic behavior and thermodynamic analysis for the formation of porous TiAl3 intermetallics sintering with different heating rates2019Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 811, artikel-id 152056Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Porous TiAl3 intermetallcis are of great interest due to its excellent properties and widely applied in filtering apparatus, separation material and catalyst carrier. In this study, interconnected pore-structures have been synthesized by diffusion or thermal explosion (TE) reaction sintering with different heating rates. The thermal characteristics such as temperature-time curves, exothermic change and visual images indicate that the sample experienced a significant TE reaction at higher heating rates. Results shown that the sample was ignited at 672 °C and then rapidly increased to combustion temperature of 1169, 1110 and 933 °C in tens of seconds with the heating rate of 15, 10 and 5 °C∙min−1 respectively. Meanwhile, TE represented the uniformity of volume combustion, instantaneous reaction and rapid cooling to furnace temperature, the amount of heat released during TE reaction dropped from 1303 to 963 J g−1. This indicates that the entire sintering process was controlled by TE and the pre-diffusion reaction before the melting temperature of Al atom, which would affect the subsequent combustion reaction. Thermodynamic data explained that the reaction mechanism is mainly step-controlled diffusion reaction at a low heating rate (1 °C∙min−1), while the energy gradually accumulated and thermal explosion (TE) reaction become obvious with the increasing of heating rate (from 2 to 15 °C∙min−1).

  • 99.
    Jiao, Xinyang
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou. School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, China.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, China.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, China.
    Liu, Yanan
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou. School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, China.
    Zhang, Laiqi
    State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, China.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering2018Ingår i: Acta Metallurgica Sinica (English Letters), ISSN 1006-7191, E-ISSN 2194-1289, Vol. 31, nr 4, s. 440-448Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Porous TiAl3 intermetallics were fabricated through vacuum reactive sintering from Ti–75Al at.% elemental powder mixture. The phase compositions, expansion behaviors, pore characteristics and microstructure evolution of TiAl3 intermetallics were investigated, and the pore formation mechanism was also proposed. It was found that the actual temperature of compacts showed an acute climb from 668 to 1244 °C in 166s, while the furnace temperature maintained the linear growth of 5 °C/min, which indicated that an obvious thermal explosion (TE) reaction occurred during sintering, and only single-phase TiAl3 intermetallic was synthesized in TE products. The open porosity increased from 22.2 (green compact) to 32.8% after reactive diffusion sintering at 600 °C and rised to 58.7% after TE, then decreased to 51.2% after high-temperature homogenization at 1100 °C. Therefore, TE reaction is the dominated pore formation mechanism of porous TiAl3 intermetallics. The pore evolution in porous TiAl3 intermetallics occurred by the following mechanisms: certain intergranular pores remained among powder particles of green compact, then low-temperature sintering resulted in a further increase in porosity due to the Kirkendall effect. Moreover, TE reaction gave rise to a dramatic volume expansion because of the rapid increase in temperature, and high-temperature sintering caused densification and a slight shrinkage.

  • 100.
    Jiao, Xinyang
    et al.
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Kang, Xueqin
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Feng, Peizhong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Zhang, Laiqi
    State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Effect of heating rate on porous TiAl-based intermetallics synthesized by thermal explosion2017Ingår i: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 32, nr 5, s. 489-494Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    TiAl-based porous materials were synthesized by a novel process of thermal explosion (TE) reaction. The effect of heating rate on expansion behavior of powder assemblies, phase compositions and pore structures were investigated. Results showed that the actual temperature of specimen increased rapidly from 655-661 °C (furnace temperature) to 1018–1136 °C (combustion temperature) in a short time interval of 25–55 s, indicating that an obvious TE reaction occurred at different heating rates (1, 2, 5 and 10°C · min−1). TE reaction in Ti/Al powder assemblies resulted in formation of open-celled TiAl-based intermetallics. When the heating rate was set at 5 °C · min−1, the maximum open porosity of 59% was obtained in Ti-Al bodies, which experienced the highest combustion temperature (1136°C) and underwent maximum volume expansion (48%). The pore size distribution was uniform and pores were interconnected in TE products.

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