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  • 1.
    Antti, Marta-Lena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kero, Ida
    Cheng, Y-B
    Monash University, Melbourne, VIC.
    Tegman, Ragnar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Phase reactions in a hot pressed TiC/Si powder mixture2012Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 38, nr 3, s. 1999-2003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work investigated the possibility of producing dense Ti3SiC2 by hot pressing TiC/Si powders. A hot press with graphite heating elements was used for densification and the phase reactions of some hot pressed samples were further evaluated by pressureless heating in a dilatometer. The density and phase composition of the heat treated samples were evaluated using Archimedes principle and by x-ray diffractometry respectively. Hot pressing resulted in a low Ti3SiC2 yield; the main phases were TiC and TiSi2 regardless of starting powder composition, temperature, holding time or pressure. A second heating without pressure resulted in Ti3SiC2 formation, but only in samples initially hot pressed at 1300 °C or lower. At higher hot pressing temperatures, thin oxide layers on particle surfaces were locked into the structure. Acting as diffusion barriers, they prevented the Ti3SiC2 forming reaction. In hot pressed samples the density was significantly higher than in samples sintered without pressure

  • 2.
    Elbadawi, Mohammed
    Luleå tekniska universitet, Institutionen för hälsovetenskap.
    Guar Gum: A Novel Binder for Ceramic ExtrusionIngår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956Artikel i tidskrift (Refereegranskat)
  • 3.
    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.

  • 4.
    Kero, Ida
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Tegman, Ragnar
    Luleå tekniska universitet.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Carbon atmosphere effect on on Ti3SiC2 based composites made from TiC/Si powders2010Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 36, nr 4, s. 1259-1263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The previous termeffect of carbonnext term activity and CO pressure in the furnace previous termatmospherenext term is investigated with respect to the phase reactions during heat treatment of TiC/Si powders. Special attention is given to the production and decomposition of Ti3SiC2. Samples were heated in graphite and alumina furnaces, connected to a dilatometer which enabled the in-situ analysis of the phase reactions. The phase compositions of the heat treated samples were determined by x-ray diffraction. The reducing previous termatmospherenext term of the graphite furnace enhanced the reactivity of the starting powder and enabled phase reactions to take place at a lower temperature than in the alumina furnace. TiSi2 and SiC phases formed at temperatures below the melting point of Si and were continuously consumed at higher temperatures. Ti3SiC2 formed at the melting point of Si regardless of furnace previous termatmosphere.next term No decomposition of the Ti3SiC2 was observed in either furnace.

  • 5. Kero, Ida
    et al.
    Tegman, Ragnar
    Luleå tekniska universitet.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Effect of the amounts of silicon on the in situ synthesis of Ti3SiC2 based composites made from TiC/Si powder mixtures2010Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 36, nr 1, s. 375-379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes how variations in silicon content and heat treatment influence on the phase composition of TiC/Si powder mixtures during heat treatment. The sintering procedure is investigated with respect to the phases produced with a particular emphasis on maximisation of the Ti3SiC2 content. The heat treated products have been analysed using scanning electron microscopy, energy dispersive spectroscopy and x-ray diffractometry. In the heat treated products Ti3SiC2 and TiC are the dominant phases and SiC and TiSi2 are found in smaller (0-30vol%) amounts. The composition was found to depend on both Si content and heat treatment temperature and time. The silicon content can be optimised with respect to maximum Ti3SiC2 production, but its value changes with different temperature programs. The highest amount (56 vol%) of Ti3SiC2 is achieved by heat treating powder mixtures of initial composition 3TiC/2.2Si at 1350° for 1 h. Heat treatment at lower temperatures (1250-1300 °C) results in an incomplete reaction and production of TiSi2.

  • 6. Kero, Ida
    et al.
    Tegman, Ragnar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Phase reactions associated with the formation of Ti3SiC2 from TiC/Si powders2011Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 37, nr 7, s. 2615-2619Artikel i tidskrift (Refereegranskat)
  • 7.
    Melk, Latifa
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Anglada, Marc
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona, Universitat Politècnica de Catalunya, Universidad de Extremadura.
    Material removal mechanisms by EDM of zirconia reinforced MWCNT nanocomposites2016Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, nr 5, s. 5792-5801Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several composites of tetragonal zirconia polycrystals doped with 3 mol% yttria (3Y-TZP) and multiwalled carbon nanotubes (MWCNT) with concentrations from 0.5 to 4 wt% CNT were processed, spark plasma sintered, and characterised for a wide range of mechanical, electrical and thermal properties. In particular, a strong increase in electrical conductivity at room temperature was found with only 0.5 wt% CNT. However, the thermal conductivity was decreasing with increasing CNT content. Electrical discharge machining (EDM) using die sinking was carried out using the composites of 1 and 2 wt% CNT as workpieces. It was shown that both compositions could be successfully machined by EDM. The surface integrity and the subsurface were studied by SEM/FIB in order to determine the material removal mechanisms, which were found to be associated to spalling and melting/evaporation. Raman Spectroscopy was used to evaluate the damage of CNTs after EDM.

  • 8.
    Melk, Latifa
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mouzon, Johanne
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Turon-Vinas, Miquel
    CIEFMA—Department of Materials Science and Metallurgical Engineering, ETSEIB, Universitat Politècnica de Catalunya.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Anglada, Marc
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona, Universitat Politècnica de Catalunya, Universidad de Extremadura.
    Surface microstructural changes of Spark Plasma Sintered Zirconia after grinding and annealing2016Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, nr 14, s. 15610-15617Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140 nm 372 nm and 753 nm grain sizes by sintering at 1250 C, 1450 C and 1600 C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60 µm, under a pressure of 0.9 MPa. The influence of grinding and annealing on the grain size has been analysed. It was shown that thermal etching after of ruff grinding of specimens at 1100 C for one hour induced an irregular surface layer of about a few hundred nanometres in thickness of recrystallized nano-grains, independently of the initial grain size. However, if the ground specimens were exposed to higher temperature, e.g. annealing at 1575 °C for one hour, the nano-grain layer was not observed and the final grain size was similar to that achieved by the same heat treatments on carefully polished specimens. Therefore, by appropriate grinding and thermal etching treatments, nanograined surface layer can be obtained which increases the resistance to low temperature degradation.

  • 9.
    Melk, Latifa
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Rovira, Joan Josep Roa
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Anglada, Marc
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona.
    Coefficient of friction and wear resistance of zirconia-MWCNTs composites2015Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, nr 1 Part A, s. 459-468Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Composites of 3 mol.% yttria-doped tetragonal zirconia (3Y-TZP) reinforced with multiwalled carbon nanotubes (MWCNT) up to 2 wt. % content have been produced using spark plasma sintering (SPS). The theoretical densities of the studied composites were found to be between 99.4 and 97.4%. The addition of MWCNT content resulted in reduction of 3Y-TZP grain size from 174 to 148 nm. The effect of MWCNT on the friction coefficient (COF) was studied by performing nano- and macro-scratches using diamond Berkovich and Rockwell indenters, respectively. Moreover, the COF and the wear rate were also investigated in reciprocating sliding against a zirconia ball under a load of 5 N. The results showed that the COF decreased upon the increase in MWCNT content. However, in macro-scratch testing, there was a critical load over which brittle fracture sets in and its value decreases as the MWCNT content increases. The wear resistance was found to be decreasing very slightly for less than 1 wt. % MWCNT, while it increases strongly for the addition of 2 wt. % MWCNT under the conditions studied. The results were discussed in terms of material properties, scanning electron microscopy observations of the wear track and nanoindentation tests.

  • 10.
    Melk, Latifa
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Rovira, Joan Josep Roa
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Garcia-Marro, Fernando
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona.
    Milsom, Ben
    Department of Materials, Queen Mary College, University of London.
    Reece, Michael J.
    Department of Materials, Queen Mary College, University of London.
    Anglada, Marc
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona.
    Nanoindentation and fracture toughness of nanostructured zirconia/multi-walled carbon nanotube composites2015Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, nr 2, s. 2453-2461Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multi-walled carbon nanotubes (MWCNTs)/3 mol% yttria-doped tetragonal zirconia (3Y-TZP) composites were produced using spark plasma sintering (SPS) with MWCNT content ranging within 0-2 wt%. In the present paper, it was shown that the addition of MWCNTs results in a refinement of the composites microstructure. Moreover, nanoindentation tests were performed in order to monitor the change in elastic modulus and hardness with MWCNT content and it was found that both properties decrease with the addition of MWCNT content. A novel method was used to measure the true fracture toughness of the composites by producing a shallow surface sharp notch machined by ultra-short pulsed laser ablation on the surface of beam specimens. The true fracture toughness obtained on this laser machined single edge V-notch beam (SEVNB) specimens tested in four point bending was compared to the indentation fracture toughness measured using a Vickers indenter. It was found that the indentation fracture toughness increases with increasing MWCNT content, while the true fracture toughness determined with SEVNB was practically independent of the composition. Finally, it was concluded that the increase in the resistance to indentation cracking of the composites with respect to 3Y-TZP matrix cannot be associated to higher true fracture toughness. The results were discussed in terms of transformation toughening, damage induced in front of the notch tip, microstructure of the composites, and fracture toughness of 3Y-TZP.

  • 11.
    Mukerji, Joydeb
    et al.
    Central Glass and Ceramic Research Institute (CGCRI), Calcutta.
    Prakash, Braham
    Wear of Nitrogen Ceramics and Composites in contact with Bearing Steel under Oscillating Sliding Conditions1998Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 24, nr 1, s. 19-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The wear of nitrogen based ceramics in contact with bearing steel balls (SAE 52100) was investigated under reciprocating sliding conditions at a velocity of 0.1 m/s, and 20 N, 40 N and 100 N load. Three types of ceramics were studied: viz. hot pressed silicon nitride (HPSN) sintered with selected liquid in the system yttria-aluminium nitride-silica and composites of HPSN with BN and TiC; SiAlON formulated with different amounts of alumina and silica; and aluminatitanium nitride composite having 60 mol% TiN. Among the HPSN composites, HPSN 15vol% TiC had the lowest average wear factor (K) of 2.0 × 10- 5mm3/m/ N. The SiAlONs, in general, had the highest K and this increased with increasing O concentration. The lowest K value for SiAlON ceramic was 6.9 × 10-5mm3/m/N. The high K value of SiAlON is attributed to O substitution, which promotes adhesive wear resulting in mutual material transfer. The lowest wear of all the ceramics tested was found for the alumina-titanium nitride composite, the wear factor being of the order of 4.4 × 10-7mm3/m/N, which is one order of magnitude lower than the other nitrogen ceramics. In the case of HPSN and alumina-titanium nitride composites, abrasive wear and wear due to microfracture were the main wear mechanisms. Wear of the steel ball was lowest when in contact with HPSN---TiC composites, being almost equal to that of the ceramic, whereas the alumina-titanium nitride composite wore away the steel almost 20 times faster than the ceramic and will thus be unsuitable as a counterface material for 52100 steel.

  • 12.
    Stjernberg, Jesper
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lindblom, B.
    LKAB.
    Wikström, J.
    LKAB.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Odén, Magnus
    Microstructural characterization of alkali metal mediated high temperature reactions in mullite based refractories2010Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 36, nr 2, s. 733-740Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two types of refractory bricks were used in reaction tests with slag from a production kiln for iron ore pellet production. Electron microscopy was used to characterize morphological changes at the slag/brick interface and active chemical reactions. Phases such as kalsilite, nepheline and potassium β-alumina form, in a layered structure, as a consequence of alkali metals migration in the brick. Larger hematite grains (50-100 μm) in the slag remain at the original slag/brick interface, while smaller grains dissolve and move through the partly dissolved brick bulk, and forms micrometer sized needle shaped crystals deeper in the lining material. Thermodynamic simulations predict the formation of a solid solution between hematite and corundum which is also observed in the reaction zone after extended time periods.

  • 13.
    Stjernberg, Jesper
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. LKAB.
    Olivas-Ogaz, M.A.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Antti, Marta-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ion, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lindblom, B.
    LKAB.
    Laboratory scale study of the degradation of mullite/corundum refractories by reaction with alkali-doped deposit materials2013Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 39, nr 1, s. 791-800Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Refractory bricks based on mullite and corundum, commonly used in rotary kilns for iron ore pellet production, and depositmaterial from an iron ore pellet production kiln, were used in laboratoryscale tests to investigate refractory/depositreactions and the infiltration of deposit components into the refractory bricks. The materials tested were in both monolithic form and in the form of powder. Alkali metal carbonates (containing sodium and potassium) were used as corrosive agents, to increase reaction kinetics. The morphological changes and active chemical reactions at the refractory/deposit interface in the samples were characterized by scanning electron microscopy. X-ray diffraction showed that alkali metals react with the mullite in the bricks, this being more pronounced in the case of sodium than potassium. Phases such as nepheline (Na2O·Al2O3·2SiO2), kalsilite and kaliophilite (both K2O·Al2O3·2SiO2), and leucite (K2O·Al2O3·4SiO2) were formed as a consequence of reactions between alkali metals and the refractory bricks. The formation of these phases causes volume expansions of between 20% and 25% in the brick materials, which accelerate degradation.

  • 14.
    Wang, Jiandong
    et al.
    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.
    Niu, Jinan
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Guo, Ruixia
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Liu, Zhangsheng
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Synthesis, microstructure and properties of MoSi2-5vol.%Al2O3 composites2014Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 40, nr 10 Part B, s. 16381-16387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    MoSi2-5vol.%Al2O3 composites were prepared in situ by self-propagating combustion synthesis from Mo, Si, Al and MoO3 powders. The combustion mode and temperature of the self-propagating reaction and phase composition of the product were investigated. The results showed that the combustion mode was a steady-state self-propagating process and the composite product was composed of MoSi2 and Al2O3. MoSi2-5vol.%Al2O3 composites were consolidated by vacuum hot-pressed sintering from 1300 to 1600 °C to produce composites with high density. MoSi2-5vol.%Al2O3 composites sintered at 1400 °C exhibited a fine microstructure and excellent mechanical properties: grain size ∼5 μm, Vicker’s hardness 11.14 GPa, bending strength 435 MPa, and fracture toughness 4.53 MPa.m1/2.

  • 15.
    Wang, Xiangjian
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China.
    Gao, Hongcheng
    Inner Mongolia Key Laboratory of Ferroelectric-related New Energy Materials and Devices, School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, China.
    Hao, Xihong
    Inner Mongolia Key Laboratory of Ferroelectric-related New Energy Materials and Devices, School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, China.
    Lou, Xiaojie
    Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China.
    Enhanced piezoelectric, electrocaloric and energy storage properties at high temperature in lead-free Bi0.5(Na1-xKx)0.5TiO3ceramics2019Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 45, nr 4, s. 4274-4282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The piezoelectric, electrocaloric and energy storage properties were systemically investigated in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics from room temperature to high temperature region. These ceramics can be poled completely to obtain large piezoelectric coefficient (104–153 pC/N) at low electric field of ~30 kV/cm. The piezoelectric propertyshows good thermal stability due to high depolarization temperature (Td). For BNKT20, a large low electric field-induced strain of 0.36% is obtained at 120 °C under 50 kV/cm, the corresponding normalized strain coefficient is up to 720 pm/V, which is larger than other BNT-based ceramics at high temperature region. The electrocaloric properties of these ceramics are studied via indirect and direct methods. Large EC value (~1.08 K) in BNKT20ceramic is obtained at 50 kV/cm using indirect calculation. Above 100 °C, the dielectricenergy storage density and efficiency of BNKT20 is still up to ~0.85 J/cm3 and 0.75, respectively. The BNKTx ceramics may become promising candidates in the fields of actuators, electrocaloric cooling and energy storage at high temperature region.

  • 16.
    Wang, Zhang
    et al.
    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.
    Wang, Xiaohong
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Geng, Peng
    School of Materials Science and Engineering, China University of Mining and Technology, Xuzhou.
    Akhtar, Farid
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Zhang, Haifei
    Department of Chemistry, University of Liverpool.
    Fabrication and properties of freeze-cast mullite foams derived from coal-series kaolin2016Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, nr 10, s. 12414-12421Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hierarchically porous mullite foams were fabricated from coal-series kaolin and Al2O3 slurries by freeze-casting using tert-butyl alcohol (TBA) and water as templates. TBA developed unidirectionally aligned pore channels along the freezing direction and water developed lamellar pores. The total porosity (60.2–83.4%), density (0.49–1.23 g/cm3) and macro-pore size (10–50 µm) of mullite foams were tailored by controlling the solid content of the slurries. The mullitization reaction was completed at the sintering temperature of 1500 °C. The compressive strength of mullite foams along the freezing direction was 3.8–49.4 MPa. Lower porosity and higher compressive strength of sintered mullite foams were obtained using TBA as solvent compared to water. The thermal conductivity of low density and mechanically stable TBA templated porous mullite with 80.2% porosity was 0.18 W/m K, indicting that the freeze-cast porous mullite was a promising refractory material for applications in thermal insulation

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