Showing papers in "Transactions of The Indian Ceramic Society in 2001"
TL;DR: In this article, fly ash, a waste material generated from thermal power stations, was used as a replacement of sandstone and to some extent feldspar in the earthenware type glazed wall tile body composition.
Abstract: This Investigation was carried out to incorporate fly ash, a waste material generated from thermal power stations, as a replacement of sandstone and to some extent feldspar in the earthenware type glazed wall tile body composition. Test specimens of eight different body compositions incorporating fly ash were prepared and fired at five different test temperatures, viz., 1000°, 1050°, 1100°, 1150° and 1200°C in an electrical furnace. Dry and fired properties like dry MOR, fired shrinkage, fired MOR, apparent porosity, water absorption, bulk density, thermal expansion of the optimized body and glaze etc were determined and compared with those of the specimens of a traditional earthenware tile body used as a standard composition. It was observed that the incorporation of fly ash in the tune of 30 wt% was the optimum In achieving the requisite thermo-mechanical properties In wall tile body.
12 citations
TL;DR: In this paper, the performance of alumina sol, prepared from a cheaper precursor and used as a bonding agent in no-cement refractory castables fabricated by simple tapping technique, was investigated.
Abstract: This paper deals with the performance of alumina sol, prepared from a cheaper precursor and used as a bonding agent in no-cement refractory castables fabricated by simple tapping technique. The physical properties of sol-bonded-castables indicate a significant improvement at elevated temperatures. The beneficial role of sol was confirmed by XRD and SEM studies when compared with similar compositions of castables cast with cement and water. It was also observed that complete rejection of cement in sol-bonded castables degrades the green strength of the materials.
7 citations
TL;DR: In this article, a new method based on sol-gel technique of internal gelation has been described for the production of porous alumina microspheres of controlled size in the range 200 to 1000 μm.
Abstract: A new method based on sol-gel technique of internal gelation has been described for the production of porous alumina microspheres of controlled size in the range 200 to 1000 μm. Good quality alumina gel spheres were prepared directly from aluminium nitrate solution, avoiding the sol preparation step, by adding urea and hexamethylene tetramine as the gelling agents. The process parameters were optimized to get the product of desired morphology. The quality of the spheres was examined by X-ray diffraction (XRD), thermogravlmetry-differential thermal analysis (TG-DTA), fourier transform infrared spectroscopy (FTIR), surface area and pore-size distribution.
6 citations
TL;DR: The ASTM standard C1422-99 classifies chemically strengthened flat glass products on the basis of the surface compression magnitude and the case depth as mentioned in this paper, based on the modulus of rupture (MOR), surface compression and case depth.
Abstract: The exchange of small alkali ions in glass with larger ions from a molten salt bath below Tg produces surface compression in the glass surface, which results in glass strengthening. Two competing processes occur: (1) generation of stress due to “ion stuffing” and (2) relaxation of the same stress due to viscous flow and network ductility. The economics of superior protection of glass products under common challenging environments, generally require a compromise between obtaining greater depths of compression (“case depth”) versus aiming for higher compression magnitudes. Control of process parameters such as bath temperature and composition is essential. Methods of quality control include measuring the modulus of rupture (MOR), surface compression and case depth. The newly instituted ASTM standard C1422–99 classifies chemically strengthened flat glass products on the basis of the surface compression magnitude and the case depth. Aircraft windshields, watch covers, auto- injector glass syringes and...
6 citations
TL;DR: In this paper, the effects of progressive incorporation of talcum powder in conventional refractory body mix having 60% china clay and 40% grog have been studied and the results revealed that the fired strength of the developed body increased from 169.40 kg.cm−2 to 288.5 kg. cm−2.
Abstract: The effects of progressive incorporation of talcum powder in conventional refractory body mix having 60% china clay and 40% grog have been studied. The specimens were fired at different test temperatures ranging from 1200° to 1400°C with 2 h dwelling time at the respective peak temperatures. The addition of talc reduced the percent thermal expansion significantly as well as enhanced the thermo-mechanical strength. The results also revealed that the fired strength of the developed body increased from 169.40 kg.cm−2 to 288.5 kg.cm'−2. The gradual reduction in the percent thermal expansion values of the talc containing bodies was attributed to the presence of cordierite and mullite phases in the compositions. The thermal shock resistance of the body mix containing 20 wt% talc was found to be about 2.5 times higher than that of the standard body mix fired at 1400°C. The developed refractory kiln furniture also provided useful service life at a working temperature of 1250°C in a bone china factory.
3 citations
TL;DR: The feasibility of utilizing fly ash, a waste inorganic product obtained by the combustion of coal in boilers of thermal power plant, was studied for the development of value added glazed ceramic materials like crockery and novelty wares as discussed by the authors.
Abstract: The feasibility of utilizing fly ash, a waste inorganic product obtained by the combustion of coal in boilers of thermal power plant, was studied for the development of value added glazed ceramic materials like crockery and novelty wares. Progressive incorporation of fly ash in replacement of silica and potash feldspar in the standard crockeryware body compositions resulted in an increase in unfired and fired strengths coupled with vitrification at 1250°C up to the addition of 30% fly ash. Further incorporation of fly ash, up to 50%, showed a decrease in fired strength and increase in water absorption at the same temperature. Improved stoneware crockery body utilizing 30% fly ash in the standard body composition was sucessfully produced.
3 citations
TL;DR: In this paper, the effect of processing methods on the purity and structure of MoSi2 grain boundaries and interfaces and their elevated temperature mechanical properties have been investigated, and it was shown that reaction-hot-pressed MoSi 2 based materials possess atomically abrupt grain boundaries (matrix) and interfaces (MoSi2-SiC composites), which are free of amorphous layers.
Abstract: The effect of processing methods on the purity and structure of MoSi2 grain boundaries and MoSi2-SiC interfaces and their elevated temperature mechanical properties have been investigated. The processing techniques involve formation of MoSi2 by in-situ reaction, hot pressing of elemental Mo and Si powders and conventional hot pressing of commercial grade Starck MoSi2 powders. The SiO2 contents of the hot pressed products have been found to be sharply different, depending on the processing methods and the composition of the raw materials used. Transmission electron microscopy (TEM) examination has shown that reaction-hot-pressed MoSi2 based materials possess atomically abrupt grain boundaries (matrix) and interfaces (MoSi2-SiC composites), which are free of amorphous layers, while Starck MoSi2 contains globular SiO2 particles. Compression tests in the range of 1100°-1300°C have shown that the reaction-hot-pressed MoSi2 and MoSi2-SiC composite have superior properties. The mechanisms of high temperature def...
2 citations
TL;DR: In this article, a review has been presented on the preparations, properties and different applications of pillared clays, and the intercalation of poly-nuclear hydroxy metal cations and metal cluster cations in smectite affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolites.
Abstract: New classes of clay based materials mainly for the use as catalysts and molecular sieves have been developed recently by the intercalation of metal complex cations with smectite clay minerals. By controlling the surface chemical equilibrium, interlamellar swelling or reactant pair proximity in the interlayer regions, the selectivity of both the metal catalyzed and proton catalyzed chemical conversions in clay intercalates can often be regulated. The intercalation of poly-nuclear hydroxy metal cations and metal cluster cations in smectite affords new pillared clay catalysts with pore sizes that can be made larger than those of conventional zeolites. In the present paper, a review has been presented on the preparations, properties and different applications of pillared clays.
2 citations
TL;DR: In this article, 40 wt% sea sand sillimanite was substituted for china clay and fireclay grog in a standard cordierite body mix containing 60% china clays, 20% fireclays grog (IS-6 grade) and 20% talc.
Abstract: Beach sand sillimanite was substituted for china clay and fireclay grog in a standard cordierite body mix containing 60% china clay, 20% fireclay grog (IS-6 grade) and 20% talc. The specimens were fired at different temperatures ranged from 1200 to 1340°C with 2 h dwelling time at respective peak temperatures. The addition of 40 wt% sillimanite in the standard composition was found to improve the mechanical properties and to reduce the coefficient of thermal expansion from 25.7 × 10−7 to 20.43 × 10−7 at 500°C and 25.20 × 10−7 to 21.34 × 10−7 at 1000 C. The reduction in the coefficient of thermal expansion value of the body mix containing 40 wt% sillimanite was due to the presence of cordierite and mullite and/or sillimanite phases in the composition. The final body also showed enhanced fired strength from 147.67 kg.cm−2 to 241.90 kg.cm−2 after firing at 1340 C. The thermal shock resistance of the developed body mix containing 40 wt% sillimanite. measured in terms of percent loss of MOE after repeated thermal shock at gradually enhanced temperatures in water quenching, was found to be more than two times higher than that of the standard cordierite composition.
2 citations
TL;DR: In this article, a series of (Y) ZrO2-Al2O3 composites of varying compositions were prepared using a semi-wet process and the slurry of attrited alumina powder with a composite nitrate solution of yttrium- zirconium was spray dried.
Abstract: A series of (Y) ZrO2-Al2O3 composites of varying compositions were prepared using a semiwet process. The slurry of attrited alumina powder with a composite nitrate solution of yttrium- zirconium was spray dried. The powders were decomposed and calcined at 500°C, compacted and sintered at 1550°C for 2 h. The bulk density of the sintered ceramics was> 99% of theoretical density with retention of 100% tetragonal phase in zirconia. The mechanical properties of sintered ceramics were evaluated and ceramics with 20 wt% (Y) ZrO2 (2.8 mol% yttria in zirconia) exhibited highest values of flexural strength (450 MPa) and fracture toughness (7.8 MPa.m½). The results have been explained on the basis of microstructure of sintered ceramics and crystallite size of zirconia particles and compared with those of the earlier studies. Microstructural analysis of the sintered compacts revealed the uniform distribution of zirconia grains in alumina matrix.
2 citations
TL;DR: In this article, the aim of the present investigation was to prepare chemically, mechanically and thermally stable porous Cr2O3 microspheres, which finds large applications as a catalyst base.
Abstract: Chromia finds large applications as a catalyst base. The aim of the present investigation was to prepare chemically, mechanically and thermally stable porous Cr2O3 microspheres. Chromia microsphere...
TL;DR: In this paper, the characteristics of raw materials sourced from Gulf countries (viz., Saudi Arabia and Turkey) used in formulation of fast single fired wall tile body (monoporosa) have been described.
Abstract: The characteristics of raw materials sourced from Gulf countries (viz., Saudi Arabia and Turkey) used in formulation of fast single fired wall tile body (monoporosa) have been described. The results of pilot level investigation on five different bodies have been given. The test results with glaze have also been included. Based on the properties of material produced, the final composition was selected for semi-industrial tests. After obtaining satisfactory results, commercial production was taken up.
TL;DR: In this article, the formation of carbon containing amorphous silica from rice husks has been studied in detail and three parameters, viz., purity, temperature of calcination and rate of heating have been found to affect the formation.
Abstract: The formation of black (carbon containing) amorphous silica from rice husks has been studied In detail. Three parameters, viz., (i) purity, (II) temperature of calcination and (iii) rate of heating have been found to affect the formation of black silica. The formation of black silica is higher in untreated rice husks than that in acid treated rice husks. The tendency to form black silica increases with the increase In the heating rate and the temperature of calcination of untreated rice husks. By treating with 3N HCI acid the formation of black silica can be avoided. Using a dopant/ catalyst, black amorphous silica stable in air up to 1000°C was prepared from acid treated rice husks.
TL;DR: In this article, the formation of mullite and zirconia by reaction sintering is monitored by X-ray diffraction and the reaction behavior is represented graphically, where the ratio of I p /ΣI p (Ip is the relative intensity of the strongest peak) for each phase is plotted as a function of temperature.
Abstract: Alumina and zircon are mixed in a proportion which gives mullite and zirconia phases after sintering. The formation of mullite and zirconia by reaction sintering is monitored by X-ray diffraction. The phases are identified from the X-ray diffraction patterns and the reaction behaviour is represented graphically, where the ratio of I p /ΣI p (Ip is the relative intensity of the strongest peak) for each phase is plotted as a function of temperature. As the reaction proceeds, the amounts of alumina and zircon decrease, whereas the amounts of mullite and zirconia increase. It is observed that the reaction starts at some temperature between 1400° and 1450°C and is complete within 2-4 h between 1500° and 1550°C. The isothermal sintering behaviour is studied by noting the variation of density, linear shrinkage and apparent porosity. At 1350°C, there is no reaction between alumina and zircon. At 1450°C the reaction is very slow while at 1550°C it is complete within 4 h. At 1650°C, complete reaction occurs by the time the sample is just heated up to the temperature. The effect of CaO is also investigated.
TL;DR: Microwave dielectric ceramics based on Sr(RE 1/2 Nb 1 / 2 )O 3 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Yb, Ga] have been prepared by the solid state ceramic route as discussed by the authors.
Abstract: Microwave dielectric ceramics based on Sr(RE 1 / 2 Nb 1 / 2 )O 3 (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Yb, Ga] have been prepared by the solid state ceramic route. The samples are characterized by XRD, SEM and microwave methods. The ceramics have high dielectric constants in the range of 22-30, low dielectric losses and a small temperature variation of the resonant frequency.
TL;DR: In this article, the feasibility of making good quality building bricks from widely distributed ferruginous and/or acidic clays of north eastern region has been examined, and it was revealed that bricks possessing compressive strength in the range of 75 to 300 kg.cm - 2 and water absorption 12-16 percent can be produced from alluvial and yellowish red mountain clays.
Abstract: Technical feasibility of making good quality building bricks from widely distributed ferruginous and/or acidic clays of north eastern region has been examined. Traditionally, the clay materials available in the region yield low strength porous bricks. The present study revealed that bricks possessing compressive strength in the range of 75 to 300 kg.cm - 2 and water absorption 12-16 percent can be produced from alluvial and yellowish red mountain clays. Judicious control of the mix composition for safe drying and firing of the bricks at optimum temperatures was found as a major prerequisite for the production of bricks conforming to BIS Specifications.
TL;DR: In this article, the authors summarized information about various aspects of bone china manufacturing, viz., raw materials, body preparation, slip control, automation, microstructure etc based on literature survey and industrial experience.
Abstract: This article summarizes information about various aspects of bone china manufacturing, viz., raw materials, body preparation, slip control, automation, microstructure etc based on literature survey and industrial experience. Various problems related to poor body characteristics, experienced by manufacturers in the small scale sector are discussed.
TL;DR: In this article, a graphite furnace at 1650°C in argon atmosphere at a positive pressure of 0.15 MPa was used for carbothermal reduction of natural silicates (e.g., zircon, sillimanite and kaolin).
Abstract: ZrO 2 -Al 2 O 3 -SiC W composite powder mixtures were prepared by carbothermal reduction of natural silicates (e.g., zircon, sillimanite and kaolin). Activated charcoal was used as the reducing agent. The reactions were carried out in a graphite furnace at 1650°C in argon atmosphere at a positive pressure of 0.15 MPa. XRD investigation of the product phases confirms the completion of the reaction and the phases were identified as monoclinic zirconia, tetragonal zirconia, α-alumina and β3-silicon carbide. SEM investigation of the powders reveals the whisker morphology of β-silicon carbide. It was observed that a small amount of zirconia was present in tetragonal form in addition to monoclinic form which could be due to fine particle size of the starting powder.
TL;DR: In this paper, a Boehmite sol was prepared by hot water hydrolysis of aluminium iso-propoxide using nitric acid as a catalyst and the results showed that there was an increase in fracture toughness of alumina ceramics with increasing silver oxide content.
Abstract: Boehmite sol was prepared by hot water hydrolysis of aluminium iso-propoxide using nitric acid as a catalyst. Hydrolysis was carried out at 80°C, magnesium nitrate and silver nitrate were added so that peptization was complete at 80°C for 1 h. The sol was precipitated in ammonia, the precipitate was centrifuged at 9000 rpm for 20 min, dried at 120°C and calcined at 600°C for three hours. The amount of magnesium oxide was kept constant at 0.5 wt% and that of silver oxide was varied from 0.5 to 10 wt%. The powder was compacted into cylindrical pellets using uniaxial press at 180 MPa and sintered at 1400°C for 3 h. 94 % T.D. was achieved for 1.0 wt% silver oxide content. Mechanical properties such as hardness, fracture toughness for compacts containing various concentrations of silver oxide were studied. The results showed that there was an increase in fracture toughness of alumina ceramics with increasing silver oxide content.
TL;DR: In this paper, the effects of different concentrations of Mn2O3 doping on the microstructure, dielectric constant, loss tangent and Curie temperature of PFN are reported.
Abstract: Lead Iron Niobate (PFN) powder, prepared by semi-wet-hydroxide route, was doped with different concentrations of Mn2O3. The powders were compacted into pellets and these were then sintered at 1000°C in PbO atmosphere. The dielectric constant and loss tangent of these ceramics were measured in the temperature range, 25°-130°C. The effects of different concentrations of Mn2O3 doping on the microstructure, dielectric constant, loss tangent and Curie temperature of PFN are reported in this study.
TL;DR: In this article, the preparation of PZT powder from a mixed nitrate solution by adding hexamine, followed by heat treatment of the gel was described by XRD, TG, DTA and specific specific attributes.
Abstract: The paper describes the preparation of PZT powder from a mixed nitrate solution by adding hexamine, followed by heat treatment of the gel. The powder was characterized by XRD, TG, DTA and specific ...
TL;DR: In this paper, six different size fractions of kaolinite from Rajmahal origin were prepared by gravity sedimentation technique and the different fractions were characterized by chemical analyses, particle sizes, surface areas, FTIR spectra, DTA and XRD studies.
Abstract: Six different size fractions of kaolinite from Rajmahal origin were prepared by gravity sedimentation technique. The different fractions were characterized by chemical analyses, particle sizes, surface areas, FTIR spectra, DTA and XRD studies. Cation exchange capacity and zeta potential of the different fractions were measured and pH titrations of the fractions were carried out to study the role of particle size on the electro-kinetic properties.
TL;DR: In this article, a high temperature oil fired semi-automatic down draught chamber kiln has been designed and commissioned in the Institute and the loading volume of the kiln is 2.0 m3.
Abstract: A high temperature oil fired semi-automatic down draught chamber kiln has been designed and commissioned in the Institute. The loading volume of the kiln is 2.0 m3. The design criteria considered the reduction of thermal mass, heat loss and incorporation of a recuperation system to achieve higher fuel efficiency. The kiln is automatically operated by a microprocessor based programmable temperature controller and a PID pressure controller. The kiln is running successfully with almost 46% fuel savings with respect to conventional kilns.
TL;DR: In this article, chemical reaction bonding has been tried for the production of building materials in the presence of 10-12 wt% moisture in separate batches, and the homogeneously mixed mass is compacted into blocks which are dried at room temperature and 373 K for 1 h and subsequently reaction bonded at 573, 673, 773 and 873 K for oneh in air.
Abstract: In recent years, chemical reaction bonding has been tried for the production of building materials. Sodium hydroxide and orthophosphoric acid were used as chemical binders in this investigation. These chemical binders are uniformly dispersed in earth mud at a concentration level of 1.0 and 2.0 wt% NaOH, and 0.2, 0.5 and 1.0 wt% H3PO4 in presence of 10–12 wt% moisture in separate batches. The homogeneously mixed mass is compacted into blocks which are dried at room temperature and 373 K for 1 h and subsequently reaction bonded at 573, 673, 773 and 873 K for 1h in air. The earth mud building block consisting of 1 % (by weight) NaOH + 0.2% H3PO4 and reaction bonded at 673 K for 1 h shows CCS of 8.0 MPa. Hand compacted earth mud building block consisting of 1% NaOH and 0.5% H3PO4, which is fired at 673 K for 1 h in air, shows CCS of 6.0 MPa. The above mentioned building blocks show good resistance to water swelling and fluctuations in environmental conditions.
TL;DR: The dispersion behavior of Si + SiC (3:1 by weight, 3Si) mixtures in deionised water was examined as a function of pH by studying their sedimentation and rheological behaviour.
Abstract: The dispersion behaviour of Si + SiC (3:1 by weight, 3Si. SiC) mixtures in deionised water was examined as a function of pH by studying their sedimentation and rheological behaviour. An aqueous sli...
TL;DR: In this article, a microwave dielectric ceramics with the general formula A5NbxTa4-xO15 (A = Ba, Sr, Mg for x = 0, 1, 2, 3, 4) were prepared by the conventional solid-state ceramic route.
Abstract: Microwave dielectric ceramics with the-general formula A5NbxTa4-xO15 (A = Ba, Sr, Mg for x = 0,1, 2, 3, 4) were prepared by the conventional solid-state ceramic route. The dielectric properties wer...
TL;DR: In this paper, the room temperature corrosion behavior of Mo2FeB2 based cermet sintered in hydrogen and vacuum was investigated in H2SO4 (0.1-3N) and 0.6N NaCI solutions by potentiodynamic polarization technique.
Abstract: The room temperature corrosion behaviour of Mo2FeB2 based cermet sintered in hydrogen and vacuum was investigated in H2SO4 (0.1–3N) and 0.6N NaCI solutions by potentiodynamic polarization technique. The study also includes X-ray diffraction, optical microscopy, and scanning electron microscopy of the as-sintered and corroded surfaces. High level of porosity present in the cermet sintered in hydrogen is responsible for poor corrosion resistance in both H2SO4 and NaCI media as compared to that sintered in vacuum.
TL;DR: In this article, the microhardness of the fired composite gels was also determined by X-ray powder diffraction and differential thermal analysis, which revealed that low temperature sintering is influenced by the addition of alumina sol in doped zirconia sol matrix to improve monolithicity.
Abstract: Polymeric monolithic doped zirconia and zirconia-alumina stiff gels (via stable zirconia and zirconia-alumina sols respectively), derived from Zr-n-propoxide, acetyl acetone, aluminium chloride, di-methyl formamide etc with judicious time-temperature-pH selection, have been prepared by controlled hydrolysis and polycondepsation, and subsequently subjected to heat treatment at 1300°C. The crystallization behaviour of the gels was studied by X-ray powder diffraction and differential thermal analysis. For the dried (25°C) composite gels pore size distributions were estimated. FTIR spectra (at 25° and 200°C) and scanning electron microscopy (at 25° and 1300°C) of both types of gels revealed that low temperature sintering is influenced by the addition of alumina sol in doped zirconia sol matrix to result in a better monolithicity. The microhardness of the fired composite gel was also determined.