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  • 1.
    Adamopoulos, Othon
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Björkman, Eva
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Zhang, Yu
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Muhammed, Mamoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Bog, Tassilo
    Mussmann, Lothar
    Lox, Egbert
    A nanophase oxygen storage material: Alumina-coated metal-based ceria2009Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 29, nr 4, s. 677-689Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanoparticles of Ce1-xMxO2-delta (M = Ca or Zr) coated with Al2O3 with average crystallite size of 10 nm have been synthesised via solution chemistry approach under controlled chemical and hydrodynamic conditions. Their synthesis has been accomplished in three major steps: (1) simultaneous co-precipitation of cations, (2) sequential precipitation of Al(OH)(3) over the former particles and (3) calcination of the precipitated precursors to the corresponding oxides. Several compositions have been synthesised and their physicochemical properties are compared with commercial state-of-the-art material. The Al2O3-coating hinders the particles growth at high temperatures, resulting in materials with a large specific surface area and a restrain in the decrease of their oxygen storage capacity.

  • 2. Ahlen, N.
    et al.
    Johnsson, M.
    Larsson, A. K.
    Sundman, Bo
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    On the carbothermal vapour-liquid-solid (VLS) mechanism for TaC, TiC, and TaxTi1-xC whisker growth2000Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 20, nr 14-15, s. 2607-2618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growth of TaC, TiC and TaxTi1-xC whiskers has been studied in some detail. The whiskers were synthesised via a vapour-liquid-solid (VLS) growth mechanism in the temperature range 1220-1400 degreesC. The starting materials were Ta2O5, TiO2, C, NaCl, and a catalyst metal (Ni, Co, Fe, and Cu were tested). The main reaction during synthesis was a carbothermal reduction of Ta2O5 and TiO2, and NaCl was added to form the oxochlorides and chlorides of Ta and Ti that account for the transport to the catalyst metal. The syntheses were made in a protecting Ar atmosphere. From experiments interrupted after different times at the synthesis temperature it is clear that sodium tantalates form as intermediate products, whereas sodium titanates cannot be identified. Only metals that are able to dissolve the elements building up the whiskers work as catalysts. Whisker growth starts either from a catalyst droplet in contact with carbon or from an oxide particle in contact with both catalyst metal and carbon. For TaC and TaxTi1-xC the only growth direction observed is [100], while TiC may grow either along [100] or along [111].

  • 3. Buscaglia, V.
    et al.
    Buscaglia, M. T.
    Viviani, M.
    Ostapchuk, T.
    Gregora, I.
    Petzelt, J.
    Mitoseriu, L.
    Nanni, P.
    Testino, A.
    Calderone, R.
    Harnagea, C.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Nygren, M.
    Raman and AFM piezoresponse study of dense BaTiO3 nanocrystalline ceramics2005Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 25, nr 12, s. 3059-3062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dense nanocrystalline BaTiO3 (BT) ceramics with grain sizes (GSs) below 100 nm obtained by spark plasma sintering (SPS), were investigated by micro-Raman spectroscopy in order to obtain information about the changes in the local order induced by size effects. The obtained spectra in the range 80-700 K showed the presence of all the crystalline phases of BaTiO3, even in the finest structure (50 nm grain size ceramic), with particularities attributed to the high density of non-ferroelectric grain boundaries. The AFM piezoresponse study incontestably proved the ferroelectric switching at local scale in nanocrystalline BaTiO3 ceramics at room temperature.

  • 4. Kese, K. O.
    et al.
    Li, Z. C.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Contact residual stress relaxation in soda-lime glass Part II. Aspects relating to strength recovery2006Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 26, nr 6, s. 1013-1022Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Strength recovery of Vickers indented soda lime glass was measured and compared after annealing at two temperatures: one below and one above T, The atomic force microscope was used to study the cracks. At 540 degrees C, no changes were observed in crack morphology either below the surface or on the surface relative to the pre-anneal state. At 630 degrees C, both sub-surface and surface crack morphology changes were observed. The trends in strength recovery were compared with residual stress relaxation as measured by a new method of stress estimation based on nanoindentation elastic response. At short hold times at 630 degrees C, and regardless of the length of hold time at 540 degrees C, strength recovery of only similar to 30% was measured while at moderately long hold times at 630 similar to C, strong recovery of fracture strength, similar to 132% was measured. Trends in strength recovery above T. are shown to match those of crack tip radius instead of trends in stress relaxation across the residual stress field.

  • 5. Kese, K.
    et al.
    Tehler, M.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Contact residual stress relaxation in soda-lime glass Part I. Measurement using nanoindentation2006Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 26, nr 6, s. 1003-1011Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The contact residual stress field created by a Vickers indentation is a micro-size region of high and varying stresses. Stress relaxation studies in such a micro-region may not be accessible to the conventional methods of investigation. In this paper the elastic response during nanoindentation has been used to study the isothermal stress relaxation of a Vickers residual stress field in soda-lime glass at 540 and 630 degrees C. At each temperature, the stress relaxation profile varied from one location of the stress field to the other suggesting non-linear response to stress. Also, the relaxation profiles at identical positions were different for the two temperatures suggesting that the Vickers residual stress field is not a thermorheologically simple region of material.

  • 6.
    Lapina, Alberto
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Li, Shuai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Synthesis of La 0.9Sr 0.1Ga 0.8Mg 0.2O 2.85 powder by gel combustion route with two-step doping strategy2012Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 32, nr 10, s. 2325-2331Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A two-step doping strategy was applied to the synthesis of La 0.9Sr 0.1Ga 0.8Mg 0.2O 2.85 (LSGM1020) powder by a gel combustion method. The Mg-doped LaGaO 3 powder was prepared in the first step, and Sr incorporation in the Mg-doped LaGaO 3 powder was done in the second step to obtain the final LSGM1020 powder. The two-step procedure is effective in preparing higher purity powders than the traditional one-step procedure. Rietveld refinement of X-ray powder diffraction (XRD) patterns shows that incorporation of Mg in LaGaO 3 in the first step enlarges the LaGaO 3 lattice: this facilitates the incorporation of Sr in the second doping step and thus high purity powder is obtained. Relatively phase pure LSGM1020 powder with only 3.1% of LaSrGaO 4 was obtained after calcination at 1300°C for 5h. Therefore, the two-step doping strategy is an effective procedure for the preparation of LSGM powders with high Sr- and Mg-doping levels.

  • 7. Li, Peng
    et al.
    Zhang, Mei
    Wang, Zhenbo
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    BF slag resistance of beta-Si3Al3O3N5 material derived from Al salt cake2015Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 35, nr 4, s. 1307-1315Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the process of recycling of salt cake from secondary aluminium smelting, it was shown that a significant value addition can be made as beta-Si3Al3O3N5 could be successfully synthesized from the rest product after water-leaching by silicothermal reduction method. In order to evaluate its refractory application, the corrosion behavior in blast furnace slag was investigated under static condition at 1400-1480 degrees C in the present work. The results show that the beta-Si3Al3O3N5 material has good slag resistance. The apparent activation energy obtained for corrosion process is -388.7 kJ/mol, revealing a more complicated dissolution mechanism. The corrosion process is started with the dissolution of intergranular phase including the iron silicides and glassy phases in the specimens, which is aided by the softening at high temperature and the continuous attack from slag, then followed by the dissolution of beta-Si3Al3O3N5 grains in the slag.

  • 8.
    Li, Shuai
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Doping effect on secondary phases, microstructure and electrical conductivities of LaGaO3 based perovskites2009Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 29, nr 6, s. 1139-1146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The intermediate temperature electrolytes La1-xSrxGa1-yMgyO3-delta (LSGM, where delta=(x+y)/2) with perovskite structure were prepared using a poly(vinyl alcohol) (PVA) solution polymerization method. Three secondary phases were identified by X-ray diffraction, LaSrGaO4, LaSrGa3O7 and La4Ga2O9. The relative amount of these secondary phases depended on the doping compositions. Sr doping produced more Sr rich secondary phases with increasing content, while enhanced solid solubility was observed with Mg addition. Sintered samples showed dense microstructures with well-developed equiaxed grains, and the secondary phases were mainly in the grain boundaries. LaSrGaO4 could not be detected by SEM for the sintered pellets. The oxygen ionic conductivity was enhanced by doping with Sr and Mg. Mg doping showed the increased conductivity activation energy. La0.8Sr0.2Ga0.9Mg0.1O2.85 had the highest ionic conductivity sigma = 0.128 S/cm at 800 degrees C in this work.

  • 9.
    Li, Shuai
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    Synthesis of La0.9Sr0.1Al0.85Mg0.1Co0.05O2.875 using a polymeric method2009Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, ISSN 0955-2219, Vol. 29, nr 6, s. 1133-1138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocrystalline La0.9Sr0.1Al0.85Mg0.1Co0.05O2.875 (LSAMC) powders were synthesized via a polymeric method using poly(vinyl alcohol) (PVA). The effect of PVA content on the synthesized powders was studied. When the ratio of positively charged valences (Mn+) to hydroxyl groups (-OH) is 1.5:1, crystalline LaAlO3 could be obtained at such a low calcination temperature as 700 degrees C. While at 900 degrees C the ratio is of less importance, since pure LaAlO3 perovskite could be formed for all powders after calcination at 900 degrees C. Thermal analysis (TG/DTA) was utilized to characterize the thermal decomposition behaviour of precursor powders. The chemical structure of the calcined powder was studied by Fourier transform infrared (FTIR) spectroscopy. The powder morphology and microstructure were examined by SEM. Dense pellets with well-developed submicron microstructures could be formed after sintering at 1450 degrees C for 5 h. Compared with the solid-state reaction method, the sintering temperature is substantially lower for powder prepared by the PVA method. This is due to the ultrafine and highly reactive powder produced.

  • 10. Li, Z. C.
    et al.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Electrical properties and ageing characteristics of BaTiO3 ceramics doped by single dopants2005Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 25, nr 4, s. 441-445Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BaTiO3 ceramics doped by single dopants Of SM2O3, Ho2O3, Bi2O3, La2O3, CeO2 and Ta2O5, respectively, were prepared and aged in air. The room-temperature resistivity was measured and the relationship between resistivity change versus ageing time was determined. The electrical resistivity of Bi- and Ta-doped samples decreases at the early ageing stage, and then increases with the ageing time; the other doped ceramics display a monotonous increase of the resistivity with ageing time. The electrical properties and ageing characteristics are analyzed by considering interior oxidation and reduction reactions and the electronegativity of the doping elements.

  • 11. Li, Z. C.
    et al.
    Zhang, H.
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Zou, X.
    Synthesis and characterization of La0.85Sr0.15Ga0.85Mg0.15O3-delta electrolyte by steric entrapment synthesis method2006Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 26, nr 12, s. 2357-2364Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Strontium and magnesium doped lanthanum gallate La0.85Sr0.15Ga0.85Mg0.15O3-delta (LSGM) oxygen ionic conducting ceramics were prepared by a steric entrapment synthesis (SES) method, which is a polymeric precursor synthesis method by using polyvinyl alcohol in aqueous solution. The perovskite LSGM phase formed essentially at a calcination temperature of 900 degrees C. Pure and single perovskite LSGM phase with high relative density of 97.1% was obtained after sintering at 1450 degrees C, while the relative density of the LSGM sample sintered at the same temperature by solid state reaction (SSR) method was 80.6% in present experiment. Comparing with SSR synthesis method, the sintering temperature by SES can be reduced at least 100 degrees C. Impedance spectra revealed that the grain-boundary resistivity of LSGM synthesized by SES was smaller than that by SSR method. and the conductivities of the samples by SES were higher than those by SSR method at all measuring temperatures.

  • 12.
    Stuer, Michael
    et al.
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Aschauer, Ulrich
    EPFL.
    Bowen, Paul
    EPFL.
    Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping2010Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 30, nr 6, s. 1335-1343Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transparent polycrystalline alumina (PCA) is a promising replacement for sapphire. Its optical properties however are highly dependent on the grain size and residual porosity which need to be controlled for real inline transmittances (RIT), that are high enough for possible applications. To achieve high RITs, doping as well as pressure assisted sintering is often used. In this study spark plasma sintering (SPS) and doping are investigated. A systematic experimental design is used to study the influence of Mg, Y and La single or co-doping (75-450 ppm) as well as the SPS sintering pressure and temperature on the RIT and grain size of PCA. Using optimized sintering parameters, RITs of >50% were attained in the visible wavelength (640 nm) for 0.8 mm thick samples for almost all doping strategies. The best RIT of 57% was for triple-doped samples at a total dopant level of 450 ppm. These results are significantly better than previously published SPS studies and illustrate that SPS sintered alumina can attain high and reproducible optical transmittances under various doping and sintering conditions.

  • 13.
    Suarez, M.
    et al.
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Fernandez, A.
    ITMA, Spain.
    Menendez, J. L.
    CSIC-CINN, Spain.
    Nygren, M.
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Torrecillas, R.
    CSIC-CINN, Spain.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Hot isostatic pressing of optically active Nd:YAG powders doped by a colloidal processing route2010Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 30, nr 6, s. 1489-1494Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, 1 at.% Nd doped Yttrium Aluminum Garnet Y(3)Al(5)O(12) (YAG) nano-sized powder prepared by colloidal route was investigated thoroughly concerning agglomeration control and preparation of transparent ceramic by post-HIP. Electrostatic and mechanical deagglomeration process followed by freeze-drying turned out to be an effective method to alleviate agglomeration, yielding a powder with a homogeneous particle size distribution around 100 nm. Transparent Nd:YAG ceramic samples have been successfully prepared by post-HIP without the aid of sintering additives. The optical properties varied markedly with the sintering and hot isostatic pressing conditions used. In-fine transmittance values of 56% at 680 nm and close to 80% in the infrared region were recorded.

  • 14.
    Tomé Torquemada, Silvia
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Glaser, Björn
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Experimental study of the phase relationships in the SrO-SiO2 system2018Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, nr 9, s. 3354-3360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phase relationships in the SiO2-SrO system were determined experimentally using the quenching technique in the temperature range between 1573 K (1300 °C) and 1898 K (1625 °C). The phases in the quenched samples were examined and identified using light optical microscopy (LOM), scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). The presence of solid phases and their nature were further confirmed using X-ray Diffraction (XRD). Based on the experimental results, the phase diagram was constructed. The phase diagram shows a congruent melting of the SrSiO3 at 1840 K (1567 °C). The eutectic between the SrSiO3, SiO2 and liquid happens at 1608 K (1335 °C) and 67 mol% SiO2 and the eutectic between the SrSiO3.

  • 15.
    Wang, Cao
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Wang, Xin
    School of Science, Hangzhou Dianzi University, China.
    Zhao, Zhe
    Department of Materials and Environmental Chemistry.
    Microstructure homogeneity control in spark plasma sintering of Al2O3 ceramics2011Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 31, nr 1-2, s. 231-235Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Homogeneous microstructure control in the SPS (spark plasma sintering) sintered big size Al2O3 ceramic was realized by the synergy effect of grain boundary tailoring and proper pressure profile design Two-step pressure profile itself did not show any efficient densification enhancement if no grain boundary modifier MgO added The two-step pressure profile can effectively reduce average grain size and grain size difference over the sintered specimen, while MgO doping can reduce the average grain size in the whole sintered samples Finally a general strategy to overcome the intrinsic temperature gradient in SPS is suggested

  • 16.
    Wang, Huijun
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Caballero, Roberto
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Dissolution of MgO based refractories in CaO-Al2O3-MgO-SiO2 slag2018Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, nr 2, s. 789-797Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dissolution of different types of MgO based refractories into molten CaO-Al2O3-MgO-SiO2 slag was studied. Formation of micro spinel particles by addition of either colloidal alumina or micro alumina powder in the MgO matrix efficiently reduced the dissolution. The dissolution of MgO was found to be controlled by the slag penetration into the MgO matrix. In the case of stagnant slag, the slag-penetration would lead to the final dissociation of the decarbonized commercial MgO-carbon cube in less than 6 min. The major dissolution took place between the MgO grains and the liquid in this penetrated layer. The increase of the thickness slowed down the dissolution. In the case of stagnant slag and slag stirred at low speed, the internal mass transfer in the slag penetrated layer is the controlling step. At higher stirring speeds, the slag-penetrated layer was removed. The removal of the penetrated layer would enhance the dissolution process.

  • 17.
    Wang, Huijun
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Caballero, Roberto
    Department of R&D, INSERTEC.
    Dissolution of MgO Based Refractories in CaO-Al2O3-MgO-SiO2 SlagInngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619XArtikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Dissolution of different types of MgO based refractories into molten CaO-Al2O3-MgO-SiOslag was studied at 1873 K. The prepared refractory cubes were dissolved in both stagnant slagand slag stirred with different speeds. Even in a stagnant slag, the decarbonized commercial MgO-carbon refractory dissolved very fast. Formation of micro spinel particles by addition of either colloidal alumina or micro alumina powder in the MgO matrix efficiently reduced the dissolution. The dissolution of MgO refractories into slag was found to be controlled by the slag penetration into the MgO matrix. In the case of stagnant slag, the slag penetration would lead to the final dissociation of the decarbonized commercial MgO-carbon cube in less than 6 minutes. A slag penetrated layer was formed in the cubes with spinel particles formed in situ.The major dissolution took place between the MgO grains and the liquid in this penetrated layer. The increase of the thickness would slow down the dissolution process. In the case of forced convection, the slag penetrated layer was removed at high stirring speeds and partially removed at lower stirring speeds. The removal of the penetrated layer would enhance the dissolution process.

  • 18.
    Xuan, Changji
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wettability and corrosion of spark plasma sintered (SPS) ZrN by liquid iron and steel2016Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 36, nr 10, s. 2435-2442Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Full dense ZrN substrates with a relative density of 96% were prepared by using the Spark Plasma Sintering (SPS) method. Thereafter, the wettability and corrosion behavior of ZrN by liquid iron and steel were studied using a sessile drop technique. The nitrogen diffusion from the ZrN substrate into pure Fe/steel was identified. A strong wetting behavior of the liquid iron and steel in contact with the ZrN substrate was found. This is due to the nitrogen diffusion into the melt. The mechanism of the nitrogen diffusion is mainly due to the ZrN substrate oxidation rather than due to a ZrN dissolution.

  • 19.
    Zhang, Zuotai
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Teng, Li-Dong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Li, Wenchao
    Mechanical Properties and Microstructures of hot-pressed MgAlON-BN Composites2007Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 27, nr 1, s. 319-326Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between the mechanical properties and microstructure of hot-pressed MgAlON-BN composite materials was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution electron microscopy (HREM) and X-ray diffraction (XRD) techniques. The phase compositions of hot-pressed samples prepared from starting mixtures of Al2O3, AlN, MgO and h-BN consisted of MgAlON phases as a matrix and BN phases as the second phase. The density, bending strength at room temperature, fracture toughness and Vickers hardness were measured. The results indicated that the density, strength and Vickers hardness decrease with increasing h-BN content due to the non-reactive nature and layered structure of h-BN. The fracture toughness, however increased with increasing h-BN addition, reaching a maximum of 3.64 MPa m(0.5); it decreased with further increase of BN content. The increase of fracture toughness was attributed to the presence of microcracks and the decrease was considered to be the discontinuous microstructure of the MgAlON phases. Temperature dependence of bending strength remained constant at low temperature, followed by an increase at 800 degrees C and then, dropped quickly. The increase in the bending strength of the composite was attributed to the decrease of residual stress and to the interwoven microstructure of the composites which prevented grain boundary slip and reduced the attenuation rate of high temperature strength. The machinability of the composites was examined. The results indicate that the composite materials with BN content more than 15 vol.% exhibit excellent machinability and could be drilled using conventional hard metal alloy drills

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