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Liu, Y., Cai, X., Sun, Z., Jiao, X., Akhtar, F., Wang, J. & Feng, P. (2018). A novel fabrication strategy for highly porous FeAl/Al2O3 composite by thermal explosion in vacuum. Vacuum, 149, 225-230
Open this publication in new window or tab >>A novel fabrication strategy for highly porous FeAl/Al2O3 composite by thermal explosion in vacuum
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2018 (English)In: Vacuum, ISSN 0042-207X, Vol. 149, p. 225-230Article in journal (Refereed) Published
Abstract [en]

The high porosity of FeAl/Al2O3 composites was successfully prepared via a low-energy consumption method of thermal explosion (TE) in vacuum from reactant mixtures of Fe, Al and Fe2O3. The temperature profiles, phase compositions, microstructure, porosity and pore size of the products were investigated. The TE reactions were ignited between 639 and 648 °C and maximum combustion temperatures reached to 1196–1867 °C. XRD patterns showed that FeAl, Fe2Al5 and Al2O3 were formed via TE reaction, and FeAl and Al2O3 were evolved as dominant phase after the final sintering at 1100 °C. The FeAl/Al2O3 composites exhibited an interconnected pore structure with porosities and pore size of 52–61% and 27–32 μm, respectively.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-67230 (URN)10.1016/j.vacuum.2017.12.043 (DOI)000425576100038 ()2-s2.0-85039993183 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-01-11 (andbra)

Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2018-03-15Bibliographically approved
Cai, X., Liu, Y., Wang, X., Jiao, X., Feng, P. & Akhtar, F. (2018). Fabrication of Highly Porous CuAl Intermetallic by Thermal Explosion Using NaCl Space Holder. JOM: The Member Journal of TMS, 70(10), 2173-2178
Open this publication in new window or tab >>Fabrication of Highly Porous CuAl Intermetallic by Thermal Explosion Using NaCl Space Holder
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2018 (English)In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, no 10, p. 2173-2178Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
The Minerals, Metals, and Materials Society, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-70257 (URN)10.1007/s11837-018-3035-5 (DOI)000445161500036 ()2-s2.0-85050195385 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-09 (inah)

Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2018-10-09Bibliographically approved
Alvi, S. & Akhtar, F. (2018). High temperature tribology of polymer derived ceramic composite coatings. Scientific Reports, 8, Article ID 15105.
Open this publication in new window or tab >>High temperature tribology of polymer derived ceramic composite coatings
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 15105Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71176 (URN)10.1038/s41598-018-33441-8 (DOI)000446856000052 ()30305660 (PubMedID)2-s2.0-85054667754 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-12 (johcin)

Available from: 2018-10-12 Created: 2018-10-12 Last updated: 2018-12-07Bibliographically approved
Jiang, Z., Zhu, G., Feng, P. & Akhtar, F. (2018). In Situ Fabrication and Properties of 0.4MoB-0.1SiC-xMoSi2 Composites by Self-propagating Synthesis and Hot-press sintering. Ceramics International, 44(1), 51-56
Open this publication in new window or tab >>In Situ Fabrication and Properties of 0.4MoB-0.1SiC-xMoSi2 Composites by Self-propagating Synthesis and Hot-press sintering
2018 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, no 1, p. 51-56Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-66006 (URN)10.1016/j.ceramint.2017.08.207 (DOI)000416877900007 ()
Note

Validerad;2017;Nivå 2;2017-11-09 (andbra)

Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2017-12-21Bibliographically approved
Nikjoo, D., Perrot, V. & Akhtar, F. (2018). Laminated Porous Diatomite Monoliths for Adsorption of Dyes From Water. Environmental Progress & Sustainable Energy
Open this publication in new window or tab >>Laminated Porous Diatomite Monoliths for Adsorption of Dyes From Water
2018 (English)In: Environmental Progress & Sustainable Energy, ISSN 1944-7442, E-ISSN 1944-7450Article in journal (Refereed) Epub ahead of print
Abstract [en]

Structured laminated diatomite monoliths with superior mechanical properties were prepared by controlled freeze-casting of the aqueous suspensions of diatomite powders for wastewater treatment. The directional freezing of suspensions with solids loading of 25, 30, and 37 wt % at cooling from 0.5 to 5 K/min resulted in the formation of lamellar pores and solid walls with the thickness of 12–30 and 14–39 μm, respectively. The increase in solid loading and freezing rate resulted in refinement of the porous structure. Durable monoliths with the mechanical strength of 5.3 MPa were obtained by thermal treatment of the freeze-dried green bodies at 1,373 K. Diatomite monoliths with a pore size of 29.6 μm showed the removal of model dye pollutant Rhodamine B from water by adsorption and long-term water stability. The dye uptake capacity of monolith changed from 1.38 to 17.04 mg/g for the initial dye concentrations between 1.0 and 12.5 mg/L at 298 K and pH = 6, respectively. The adsorption data analysis using Lagergren's pseudo-first-order, pseudo-second-order, and intra-particle diffusion models revealed that diatomite monoliths offered efficient mass transfer in the porous laminated scaffold and to the adsorption sites and bulk diffusion of dye molecules in water was the rate-limiting mechanism for dye removal. © 2018 American Institute of Chemical Engineers Environ Prog, 2018.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71352 (URN)10.1002/ep.13064 (DOI)
Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2018-10-26
Jiao, X., Wang, X., Feng, P., Liu, Y., Zhang, L. & Akhtar, F. (2018). Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering. Acta Metallurgica Sinica (English Letters), 31(4), 440-448
Open this publication in new window or tab >>Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering
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2018 (English)In: Acta Metallurgica Sinica (English Letters), ISSN 1006-7191, E-ISSN 2194-1289, Vol. 31, no 4, p. 440-448Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Intermetallics, Porous materials, Powder metallurgy, Reaction synthesis, Thermal explosion synthesis
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-66364 (URN)10.1007/s40195-017-0663-7 (DOI)000429386300011 ()
Note

Validerad;2018;Nivå 2;2018-03-14 (rokbeg)

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-04-26Bibliographically approved
Narang, K., Fodor, K., Kaiser, A. & Akhtar, F. (2018). Optimized cesium and potassium ion-exchanged zeolites A and X granules for biogas upgrading. RSC Advances, 8(65), 37277-37285
Open this publication in new window or tab >>Optimized cesium and potassium ion-exchanged zeolites A and X granules for biogas upgrading
2018 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 8, no 65, p. 37277-37285Article in journal (Refereed) Published
Abstract [en]

Partially ion-exchanged zeolites A and X binderless granules were evaluated for CO2 separation from CH4. The CO2 adsorption capacity and CO2-over-CH4 selectivity of binderless zeolites A and X granules were optimized by partial exchange of cations with K+ and Cs+, while retaining the mechanical strength of 1.3 MPa and 2 MPa, respectively. Single gas CO2 and CH4 adsorption isotherms were recorded on zeolites A and X granules and used to estimate the co-adsorption of CO2–CH4 using ideal adsorbed solution theory (IAST). The IAST co-adsorption analysis showed that the partially ion-exchanged binderless zeolites A and X granules had a high CO2-over-CH4 selectivity of 1775 and 525 respectively, at 100 kPa and 298 K. Optimally ion-exchanged zeolite X granules retained 97% of CO2 uptake capacity, 3.8 mmol g−1, after 5 breakthrough adsorption–desorption cycles while for zeolite A ion-exchanged granules the reduction in CO2 uptake capacity was found to be 18%; CO2uptake capacity of 3.4 mmol g−1. The mass transfer analysis of breakthrough experimental data showed that the ion-exchanged zeolite X had offered a higher mass transfer coefficient, (κ) through the adsorption column compared to zeolite A; 0.41 and 0.13 m s−1 for NaK4.5Cs0.3X and CaK2.5Cs0.2A, respectively

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71679 (URN)10.1039/C8RA08004F (DOI)2-s2.0-85056892674 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-20 (johcin) 

Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2018-12-03Bibliographically approved
Cai, X., Liu, Y., Wang, X., Jiao, X., Wang, J., Akhtar, F. & Feng, P. (2018). Oxidation Resistance of Highly Porous Fe-Al Foams Prepared by Thermal Explosion. Metallurgical and Materials Transactions. A, 49A(8), 3683-3691
Open this publication in new window or tab >>Oxidation Resistance of Highly Porous Fe-Al Foams Prepared by Thermal Explosion
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2018 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 8, p. 3683-3691Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-69047 (URN)10.1007/s11661-018-4680-6 (DOI)000436905100049 ()2-s2.0-85047921551 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-06 (rokbeg)

Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-08-06Bibliographically approved
Ciurans Oset, M., Nordin, J. & Akhtar, F. (2018). Processing of Macroporous Alumina Ceramics Using Pre-Expanded Polymer Microspheres as Sacrificial Template. Ceramics, 1(2), 329-342
Open this publication in new window or tab >>Processing of Macroporous Alumina Ceramics Using Pre-Expanded Polymer Microspheres as Sacrificial Template
2018 (English)In: Ceramics, ISSN 2571-6131, Vol. 1, no 2, p. 329-342Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
gel-casting, sacrificial templating, macroporous alumina, pre-expanded polymeric microspheres
National Category
Ceramics Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71773 (URN)10.3390/ceramics1020026 (DOI)
Note

Validerad;2018;Nivå 1;2018-12-07 (johcin)

Available from: 2018-11-27 Created: 2018-11-27 Last updated: 2018-12-10Bibliographically approved
Saeidi, K., Neikter, M., Olsen, J., Shen, Z. J. & Akhtar, F. (2017). 316L stainless steel designed to withstand intermediate temperature. Materials & design, 135, 1-8
Open this publication in new window or tab >>316L stainless steel designed to withstand intermediate temperature
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2017 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 135, p. 1-8Article in journal (Refereed) Published
Abstract [en]

Austenitic stainless steel 316L was fabricated for withstanding elevated temperature by selective laser melting (SLM). Tensile tests at 800 °C were carried out on laser melted 316L with two different strain rates of 0.05 S− 1 and 0.25 S− 1. The laser melted 316L showed tensile strength of approximately 400 MPa at 800 °C, which was superior to conventional 316L. Analysis of fracture surface showed that the 316L fractured in mixed mode, ductile and brittle fracture, with an elongation of 18% at 800 °C. In order to understand the mechanical response, laser melted 316L was thermally treated at 800 °C for microstructure and phase stability. X-ray diffraction (XRD) and Electron back scattered diffraction (EBSD) of 316L treated at 800 °C disclosed a textured material with single austenitic phase. SEM and EBSD showed that the characteristic and inherent microstructure of laser melted 316L, consisting of elongated grains with high angle grain boundaries containing subgrains with a smaller misorientation, remained similar to as-built SLM 316L during hot tensile test at 800 °C. The stable austenite phase and its stable hierarchical microstructure at 800 °C led to the superior mechanical response of laser melted 316L.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-65565 (URN)10.1016/j.matdes.2017.08.072 (DOI)000413236300001 ()2-s2.0-85028815416 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-09-11 (andbra)

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2018-03-05Bibliographically approved
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