Pub Date : 2004-02-01DOI: 10.1179/096797804225012710
S. Šorli, M. A. Tena, J. Badenes, M. Llusar, G. Monrós
Abstract NixTi1 - 3xM2xO2 (M = Sb, Nb; 0·05 ≤ x ≤ 0·10) samples have been synthesised from mixtures of NiO, Nb2O5, Sb2O3, and TiO2. From characterisation of these samples, x = 0·05 was chosen to compare results with different nickel precursors. Thus samples of Ni0·05Ti0·85M0·10O2 (M = Sb, Nb) were also prepared from NiCO3.3Ni(OH)2.4H2O, NiCl2.6H2O, Ni(NO3)2.6H2O, NiSO4.6H2O, and Ni(CH3COO)2.4H2O. A eutectic mixture of alkaline halides (NaF:2NaCl) was used as fluxing agent. Optimal yellow colour was found in the mixture of NiSO4.6H2O, Sb2O5, and TiO2 fired at 1100°C for 2 h.
{"title":"Study of nickel precursors in (Ni,M,Ti)O2 (M = Sb, Nb) yellow ceramic pigments","authors":"S. Šorli, M. A. Tena, J. Badenes, M. Llusar, G. Monrós","doi":"10.1179/096797804225012710","DOIUrl":"https://doi.org/10.1179/096797804225012710","url":null,"abstract":"Abstract NixTi1 - 3xM2xO2 (M = Sb, Nb; 0·05 ≤ x ≤ 0·10) samples have been synthesised from mixtures of NiO, Nb2O5, Sb2O3, and TiO2. From characterisation of these samples, x = 0·05 was chosen to compare results with different nickel precursors. Thus samples of Ni0·05Ti0·85M0·10O2 (M = Sb, Nb) were also prepared from NiCO3.3Ni(OH)2.4H2O, NiCl2.6H2O, Ni(NO3)2.6H2O, NiSO4.6H2O, and Ni(CH3COO)2.4H2O. A eutectic mixture of alkaline halides (NaF:2NaCl) was used as fluxing agent. Optimal yellow colour was found in the mixture of NiSO4.6H2O, Sb2O5, and TiO2 fired at 1100°C for 2 h.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123743482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2004-02-01DOI: 10.1179/096797804225012684
B. Han, N. Li
Abstract Pellets pressed from WO3, Al, and fused Al2O3 powder mixes according to the stoichiometry 3Al + WO3 + xAl2O3 = (x + 1)Al2O3 + W (x = 0·1-0·5) were heated at 1473, 1623, and 1773 K for 3 h under coke granules. The composition and microstructure of samples were examined by X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-ray analysis. The products of the Al-WO3 reaction were found to consist of tungsten, corundum, and tungsten carbides. For x ≤ 0·3, temperature had little effect on the X-ray intensity ratios (IWC(101) + IW2C(101)) / IW(101) and IWC(101) / IW2C(101), whereas at x = 0·5 the influence of temperature was significant. Tungsten was converted to tungsten carbides in the samples heated at 1773 K. High temperature improved diffusion in the tungsten carbide layer and promoted the transformations from W to WC and from W2C to WC. Sintering of the corundum and tungsten resulted in cracks that provided rapid diffusion pathways for CO to penetrate and react with W.
{"title":"Composition of Al2O3-W-WC composite prepared by WO3-Al reaction under coke","authors":"B. Han, N. Li","doi":"10.1179/096797804225012684","DOIUrl":"https://doi.org/10.1179/096797804225012684","url":null,"abstract":"Abstract Pellets pressed from WO3, Al, and fused Al2O3 powder mixes according to the stoichiometry 3Al + WO3 + xAl2O3 = (x + 1)Al2O3 + W (x = 0·1-0·5) were heated at 1473, 1623, and 1773 K for 3 h under coke granules. The composition and microstructure of samples were examined by X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-ray analysis. The products of the Al-WO3 reaction were found to consist of tungsten, corundum, and tungsten carbides. For x ≤ 0·3, temperature had little effect on the X-ray intensity ratios (IWC(101) + IW2C(101)) / IW(101) and IWC(101) / IW2C(101), whereas at x = 0·5 the influence of temperature was significant. Tungsten was converted to tungsten carbides in the samples heated at 1773 K. High temperature improved diffusion in the tungsten carbide layer and promoted the transformations from W to WC and from W2C to WC. Sintering of the corundum and tungsten resulted in cracks that provided rapid diffusion pathways for CO to penetrate and react with W.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128885546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225009300
A. Escardino, S. Mestre, A. Barba, C. Feliu, A. Blasco, V. Beltrán
Abstract The influence of initial Fe2O3-Cr2O3 mixture particle size and composition on the black (Fe,Cr)2O3 pigment synthesis reaction has been studied. An empirical equation is proposed, based on a mathematical expression derived in a previous study,which relates these variables to resulting pigment mass fraction, synthesis time, and temperature in the studied range of operating conditions.
{"title":"Kinetic study of black (Fe,Cr)2O3 pigment synthesis reaction: influence of composition and particle size","authors":"A. Escardino, S. Mestre, A. Barba, C. Feliu, A. Blasco, V. Beltrán","doi":"10.1179/096797803225009300","DOIUrl":"https://doi.org/10.1179/096797803225009300","url":null,"abstract":"Abstract The influence of initial Fe2O3-Cr2O3 mixture particle size and composition on the black (Fe,Cr)2O3 pigment synthesis reaction has been studied. An empirical equation is proposed, based on a mathematical expression derived in a previous study,which relates these variables to resulting pigment mass fraction, synthesis time, and temperature in the studied range of operating conditions.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117253219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225009292
A. Escardino, S. Mestre, A. Barba, M. Monzó, A. Blasco, V. Beltrán
Abstract Samples of black (Fe,Cr)2O3 pigment were prepared from a starting mixture of Fe2O3 and Cr2O3 (50:50 by weight) at five temperatures between 1273 and 1423 K, using synthesis times ranging from 0 to 9 h. The influence of synthesis temperature and time on the chromatic coordinates of the pigment samples was established, and their chromatic coordinates were determined. On the basis of the experimental results, a single empirical correlation was obtained between each of the chromatic coordinates and the mass fraction in solid solution of the same composition as the starting oxide mixture present in each pigment sample.
{"title":"Colorimetric study of black (Fe,Cr)2O3 pigment synthesis reaction: relation between chromatic coordinates and synthesis conditions","authors":"A. Escardino, S. Mestre, A. Barba, M. Monzó, A. Blasco, V. Beltrán","doi":"10.1179/096797803225009292","DOIUrl":"https://doi.org/10.1179/096797803225009292","url":null,"abstract":"Abstract Samples of black (Fe,Cr)2O3 pigment were prepared from a starting mixture of Fe2O3 and Cr2O3 (50:50 by weight) at five temperatures between 1273 and 1423 K, using synthesis times ranging from 0 to 9 h. The influence of synthesis temperature and time on the chromatic coordinates of the pigment samples was established, and their chromatic coordinates were determined. On the basis of the experimental results, a single empirical correlation was obtained between each of the chromatic coordinates and the mass fraction in solid solution of the same composition as the starting oxide mixture present in each pigment sample.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127424069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225009319
H. B. Lee, S. Kim, S. Kang, Y. Han
Abstract The microstructure and mechanical properties of TiB2/Al nanocomposites based on the Ti-Al-B system, consolidated by spark plasma sintering of mechanically alloyed activated nanopowders, have been characterised. Mechanical alloying was carried out in a planetary ball mill for 120-180 min at 350 rev min-1. The powders were pressed in vacuum at a pressure of 60 MPa; a dc current of 1800 A was applied for 4 min, generating a maximum temperature in the graphite mould of 1400° C. Analysis of the synthesised nanocomposites by SEM, XRD, and TEM showed them to consist of TiB2 second phase particles, 10-30 nm in size, in a near amorphous Al phase, with unreacted Ti and B on grain boundaries as a ternary phase. Composites consolidated from powders mechanically alloyed from an initial elemental powder mix of 0·3 mol Al, 0·7 mol Ti, and 2·0 mol B achieved the best relative density (98%) and bending strength (847 MPa); the highest Vickers hardness of 19·6 GPa was achieved for the 0·1:0·9:2·0 mol starting composition.
{"title":"Characterisation of mechanically alloyed Ti–Al–B nanocomposite consolidated by spark plasma sintering","authors":"H. B. Lee, S. Kim, S. Kang, Y. Han","doi":"10.1179/096797803225009319","DOIUrl":"https://doi.org/10.1179/096797803225009319","url":null,"abstract":"Abstract The microstructure and mechanical properties of TiB2/Al nanocomposites based on the Ti-Al-B system, consolidated by spark plasma sintering of mechanically alloyed activated nanopowders, have been characterised. Mechanical alloying was carried out in a planetary ball mill for 120-180 min at 350 rev min-1. The powders were pressed in vacuum at a pressure of 60 MPa; a dc current of 1800 A was applied for 4 min, generating a maximum temperature in the graphite mould of 1400° C. Analysis of the synthesised nanocomposites by SEM, XRD, and TEM showed them to consist of TiB2 second phase particles, 10-30 nm in size, in a near amorphous Al phase, with unreacted Ti and B on grain boundaries as a ternary phase. Composites consolidated from powders mechanically alloyed from an initial elemental powder mix of 0·3 mol Al, 0·7 mol Ti, and 2·0 mol B achieved the best relative density (98%) and bending strength (847 MPa); the highest Vickers hardness of 19·6 GPa was achieved for the 0·1:0·9:2·0 mol starting composition.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134324539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225009337
E. El-Meliegy
Abstract Low fusion leucite containing dental porcelain was prepared from Egyptian feldspar and talc raw materials by firing for 6 min at 800-950° C. Porcelain frit was first made through fusion of the respective formulations at temperatures between 1100 and 1300° C and then poured into a cold stream of water. The frit was milled to pass a 75 μm sieve. Thermal expansion was followed using a dilatometer. The crystallisation of leucite was regulated by adjusting the rate of heating and by addition of nucleating agents. The main mineral phase developed is the tetragonal leucite form. The amount of crystallised leucite was monitored to control the translucency of the porcelain. Thermal expansion coefficient was in the range 10·0-14·5 × 10-6 K-1 (20-500° C). Microstructure was investigated using SEM.
{"title":"Preparation and characterisation of low fusion leucite dental porcelain","authors":"E. El-Meliegy","doi":"10.1179/096797803225009337","DOIUrl":"https://doi.org/10.1179/096797803225009337","url":null,"abstract":"Abstract Low fusion leucite containing dental porcelain was prepared from Egyptian feldspar and talc raw materials by firing for 6 min at 800-950° C. Porcelain frit was first made through fusion of the respective formulations at temperatures between 1100 and 1300° C and then poured into a cold stream of water. The frit was milled to pass a 75 μm sieve. Thermal expansion was followed using a dilatometer. The crystallisation of leucite was regulated by adjusting the rate of heating and by addition of nucleating agents. The main mineral phase developed is the tetragonal leucite form. The amount of crystallised leucite was monitored to control the translucency of the porcelain. Thermal expansion coefficient was in the range 10·0-14·5 × 10-6 K-1 (20-500° C). Microstructure was investigated using SEM.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116877860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225009346
M. Jackson, G. Robinson, N. Dahotre, A. Khangar, R. Moss
Abstract Grinding is a manufacturing process that produces engineering components to a desired surface finish. In continuous grinding operations, the grinding efficiency of vitrified grinding wheels deteriorates as the sharp cutting edges become blunt as a result of the formation of wear flats. Dressing is essentially a sharpening operation which addresses this problem by generating a specific topography on the cutting face of the grinding wheel. High power lasers are being explored as a non-contact dressing technique. In the present study, a high power laser was used to produce a resolidified layer on the surface of vitrified aluminium grinding wheels. The high heat flux intensity produced both solid-solid and solid-liquid phase transformations. Microstructural analysis of the dressed wheel surface showed extensive grain refinement. Microcutting edges are produced on the individual grinding grains. Though a wide grain size distribution was observed, grain shape was more regular (equiaxed), with well defined vertices and edges on each grain. The vertices and edges provide cutting edges for improved grinding at the microscale. Area analysis of surfaces using energy dispersive area analysis (EDAX) revealed the presence of Al, Cr, O, Si, K, and Na. However, X-ray diffractometry on the surface indicated the presence of Al2O3 phase only. The upper resolidified layer contained Si, Na, K, and P, whereas the material below was primarily Al, Cr, and O. This suggests that a glassy phase (with Al, O, Na, K, P, and Si) is formed on the surface. Subsequent laser treatment modified the morphological structure of the vitrified grinding wheel surface, thus creating a dressing effect with locally sculpted microscale cutting edges on each grinding grain. The experimental results indicate that laser modified grinding wheels are comparable in performance to diamond dressed grinding wheels.
磨削是一种制造过程，使工程部件达到所需的表面光洁度。在连续磨削作业中，玻璃化砂轮的磨削效率下降，锋利的切削刃由于形成磨平而变钝。修整本质上是一种锐化操作，它通过在砂轮的切割面上产生特定的地形来解决这个问题。高功率激光作为一种非接触式敷料技术正在被探索。本研究采用高功率激光在玻璃化铝砂轮表面形成再凝固层。高热流密度同时产生固-固相变和固-液相变。修整后的车轮表面的显微组织分析显示出广泛的晶粒细化。在单个磨粒上产生微切削刃。虽然晶粒尺寸分布较宽，但晶粒形状更为规则(等轴)，每个晶粒上都有明确的顶点和边缘。顶点和边缘为改善微尺度磨削提供切削刃。使用能量色散面积分析(EDAX)对表面进行面积分析，发现存在Al, Cr, O, Si, K和Na。然而，表面的x射线衍射显示仅存在Al2O3相。上层的再凝固层含有Si、Na、K和P，而下层主要是Al、Cr和O。这表明在表面形成了一个玻璃相(Al、O、Na、K、P和Si)。随后的激光处理改变了玻璃化砂轮表面的形态结构，从而在每个磨粒上产生局部雕刻的微尺度切割边缘的修整效果。实验结果表明，激光修饰砂轮的磨削性能与金刚石修饰砂轮相当。
{"title":"Laser dressing of vitrified aluminium oxide grinding wheels","authors":"M. Jackson, G. Robinson, N. Dahotre, A. Khangar, R. Moss","doi":"10.1179/096797803225009346","DOIUrl":"https://doi.org/10.1179/096797803225009346","url":null,"abstract":"Abstract Grinding is a manufacturing process that produces engineering components to a desired surface finish. In continuous grinding operations, the grinding efficiency of vitrified grinding wheels deteriorates as the sharp cutting edges become blunt as a result of the formation of wear flats. Dressing is essentially a sharpening operation which addresses this problem by generating a specific topography on the cutting face of the grinding wheel. High power lasers are being explored as a non-contact dressing technique. In the present study, a high power laser was used to produce a resolidified layer on the surface of vitrified aluminium grinding wheels. The high heat flux intensity produced both solid-solid and solid-liquid phase transformations. Microstructural analysis of the dressed wheel surface showed extensive grain refinement. Microcutting edges are produced on the individual grinding grains. Though a wide grain size distribution was observed, grain shape was more regular (equiaxed), with well defined vertices and edges on each grain. The vertices and edges provide cutting edges for improved grinding at the microscale. Area analysis of surfaces using energy dispersive area analysis (EDAX) revealed the presence of Al, Cr, O, Si, K, and Na. However, X-ray diffractometry on the surface indicated the presence of Al2O3 phase only. The upper resolidified layer contained Si, Na, K, and P, whereas the material below was primarily Al, Cr, and O. This suggests that a glassy phase (with Al, O, Na, K, P, and Si) is formed on the surface. Subsequent laser treatment modified the morphological structure of the vitrified grinding wheel surface, thus creating a dressing effect with locally sculpted microscale cutting edges on each grinding grain. The experimental results indicate that laser modified grinding wheels are comparable in performance to diamond dressed grinding wheels.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128598895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225005025
D. Phillips
Abstract This paper reports on a series of efflorescence tests and instrumental techniques that have been used to determine the nature and mechanism of vanadium staining, and the effects of additions of magnesite, calcite, and fluorspar to the brick mix to eliminate the problem. Scanning electron microscopy, electron probe microanalysis, inductively coupled mass spectrometry (with laser ablation attachment), and X-ray photon spectrometry have been used to more fully understand the elemental composition, oxidation states, and formation of vanadium stains in fired clay bricks. It was found that the stains consist of V, K, Na, Mo, S, and O. Vanadium +4 compounds form initially within the brick and are slowly oxidised to vanadium +5 compounds as the water transports the potassium and sodium salts to the brick surface. X-ray diffraction led to a reasonably successful search match for a KVO(SO4)2 phase for the stains. Evolved gas analysis showed loss of vanadium compounds between 700 and 900° C which are most likely VF3 and VCl4. Inductively coupled plasma spectrometry laser ablation studies on thin sections of brick showed areas of glassy phases corresponding to the agglomeration of Mg/V/Al/Si and Mg/Al/Si. The increased alkalinity of magnesia and the comparable sizes of V4+ and Mgions are driving forces for locking vanadium into what is otherwise an acidic glassy phase. The addition of 1 wt-% magnesite to the brick mix led to fired products on a commercial scale that are free from vanadium staining.
{"title":"Vanadium staining in fired clay bricks","authors":"D. Phillips","doi":"10.1179/096797803225005025","DOIUrl":"https://doi.org/10.1179/096797803225005025","url":null,"abstract":"Abstract This paper reports on a series of efflorescence tests and instrumental techniques that have been used to determine the nature and mechanism of vanadium staining, and the effects of additions of magnesite, calcite, and fluorspar to the brick mix to eliminate the problem. Scanning electron microscopy, electron probe microanalysis, inductively coupled mass spectrometry (with laser ablation attachment), and X-ray photon spectrometry have been used to more fully understand the elemental composition, oxidation states, and formation of vanadium stains in fired clay bricks. It was found that the stains consist of V, K, Na, Mo, S, and O. Vanadium +4 compounds form initially within the brick and are slowly oxidised to vanadium +5 compounds as the water transports the potassium and sodium salts to the brick surface. X-ray diffraction led to a reasonably successful search match for a KVO(SO4)2 phase for the stains. Evolved gas analysis showed loss of vanadium compounds between 700 and 900° C which are most likely VF3 and VCl4. Inductively coupled plasma spectrometry laser ablation studies on thin sections of brick showed areas of glassy phases corresponding to the agglomeration of Mg/V/Al/Si and Mg/Al/Si. The increased alkalinity of magnesia and the comparable sizes of V4+ and Mgions are driving forces for locking vanadium into what is otherwise an acidic glassy phase. The addition of 1 wt-% magnesite to the brick mix led to fired products on a commercial scale that are free from vanadium staining.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129187049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-12-01DOI: 10.1179/096797803225009391
A. Othman
Abstract Refractories produced from mixes of Egyptian dolomitic magnesite with talc and low cost Chinese bauxite have been assessed as potential substitutes for the high temperature basic refractory bricks currently used in steelmaking and other industries. Fifteen batches of different compositions were prepared by firing for 2 h up to 1580° C. Six samples were selected for further investigation on the basis of their phase composition and densification parameters. The mineralogical composition and microstructure, pore size distribution, and mechanical and refractory properties of these samples were investigated. All six samples consisted mainly of MgO and MA spinel refractory phases, plus some calcium silicates and aluminoferrite phases. The latter phases contribute to densification during firing by promoting liquid phase formation. Most samples showed high refractoriness under load, good spalling resistance, better mechanical properties than current refractories, and compact microstructure. It is concluded that these new refractories are good candidate materials for the production of shaped linings for industrial kilns and furnaces.
{"title":"Effect of talc and bauxite on sintering, microstructure, and refractory properties of Egyptian dolomitic magnesite","authors":"A. Othman","doi":"10.1179/096797803225009391","DOIUrl":"https://doi.org/10.1179/096797803225009391","url":null,"abstract":"Abstract Refractories produced from mixes of Egyptian dolomitic magnesite with talc and low cost Chinese bauxite have been assessed as potential substitutes for the high temperature basic refractory bricks currently used in steelmaking and other industries. Fifteen batches of different compositions were prepared by firing for 2 h up to 1580° C. Six samples were selected for further investigation on the basis of their phase composition and densification parameters. The mineralogical composition and microstructure, pore size distribution, and mechanical and refractory properties of these samples were investigated. All six samples consisted mainly of MgO and MA spinel refractory phases, plus some calcium silicates and aluminoferrite phases. The latter phases contribute to densification during firing by promoting liquid phase formation. Most samples showed high refractoriness under load, good spalling resistance, better mechanical properties than current refractories, and compact microstructure. It is concluded that these new refractories are good candidate materials for the production of shaped linings for industrial kilns and furnaces.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125751456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-10-01DOI: 10.1179/174327613X13789816848661
D. Thompson
Abstract The 1950s saw the emergence of the group of materials originally referred to as 'special ceramics'. These then became 'engineering ceramics', and more recently have been further subdivided into bioceramics, functional ceramics, and structural ceramics. These materials demonstrate excellent properties for the application areas indicated, and share the common feature of not using clay as a starting material. In the early 1960s, it could not have been foreseen that electrical ceramics (including superconductors) would develop much more rapidly than the rest; of course this move was stimulated by concurrent developments in computing and electronic devices. In contrast, the more diverse, scientifically challenging structural ceramics have struggled to find niches in a very competitive marketplace, showing only modest growth over the last 30 years. Silicon carbide has been perhaps the least dramatic in its progress, whereas zirconia, stimulated by the toughening revolution, generated an explosion of interest in the early 1980s, though this has since moderated. In contrast, silicon nitride, with the associated family of sialon ceramics, has maintained an overall upward curve for some 40 years, punctuated by occasional spurts due either to new market opportunities or to materials developments, a good current example of the latter being the recent appearance of a group of ultrahard high pressure derivatives.
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