Showing papers in "Transactions of The Indian Ceramic Society in 1990"
TL;DR: In this article, the incorporation of ZrO2 in Al2O3 matrix was performed by conventional mechanical mixing and co-precipitation methods, and the densification behavior on sintering up to 1800°C and the resulting microstructural features of these ceramics have been studied.
Abstract: The incorporation of ZrO2 in Al2O3 matrix was performed by conventional mechanical mixing and co-precipitation methods. The densification behaviour on sintering up to 1800°C and the resulting microstructural features of these ceramics have been studied. In either case no appreciable densification was noticed up to 1600°C. The co-precipitated powder compacts containing 20% ZrO2 after sintering at 1700°C achieved the density of 4.14 gm.cm−3 and open porosity about 3.0%. Microstructural features showed a pronounced grain growth inhibition effect with increasing concentration of ZrO2. Vacuum hot-pressing was found to be beneficial from the point of view of densification and mechanical properties of these compacts.
6 citations
TL;DR: In this paper, the underlying principles, operation and design of two types of established oxygen sensors based on zirconia and titania are reviewed, with special emphasis on sensors utilising oxygen pumping and thin film technology for operation at lean air/fuel ratios.
Abstract: Oxygen sensors are used to improve fuel efficiency and to control exhaust emissions in automobiles. The underlying principles, operation and design of two types of established oxygen sensors based on zirconia and titania are reviewed. Recent advances in sensor concepts to overcome the limitations of the zirconia and titania sensors are examined with special emphasis on sensors utilising oxygen pumping and thin film technology for operation at lean air/fuel ratios.
3 citations
TL;DR: In this article, the powder metallurgical aspects of thoria-10 mole % yttria system have been carried out, by decomposition and calcination of mixed nitrates and co-precipitated oxalates.
Abstract: A systematic study oil the powder metallurgical aspects of thoria—10 mole % yttria system has been carried out. Powders of ThOa—10 mole % Y2O3 compositions were derived by decomposition and calcination of mixed nitrates and co-precipitated oxalates. They were evaluated for their powder characteristics including crystallite size and morphology, compaction and sintering behaviour. The microstructure and oxide ion transference number of the various sintered specimens have been evaluated.
3 citations
TL;DR: In this paper, reaction bonded silicon carbide (RBSC) infiltrated with vanadium carbide, boron carbide and molybdenum disili-cide (5 wt% each) for 300 minutes.
Abstract: Oxidation studies of reaction bonded silicon carbide (RBSC) infiltrated with vanadium carbide, boron carbide and molybdenum disili- cide (5 wt% each) have been carried out at 1350°, 1400° and 1450°C for 300 minutes. Oxidation resistance of RBSC decreases with addition of the above infiltrants. However, weight gain per unit area is the lowest at higher temperatures (1400°, 1450°C) in case of RBSC infiltrated with vanadium carbide.
2 citations
TL;DR: In this paper, new fluoride glasses in the PbF2CdF2-AIF3-LiF have been synthesized and the present glasses were found to be 85-90% transparent to IR radiation up to 7 μm.
Abstract: New fluoride glasses in the PbF2-CdF2-AIF3-LiF have been synthesized. Stability against crystallization has been studied by thermal analysis of the glasses. The present glasses were found to be 85–90% transparent to IR radiation up to 7 μm. The absorption at 2.9 μm was due to HF2-species and not due to OH-species. A static dissolution test showed very low solubility for these glasses in water at room temperature. Results on refractive index and microhardness measurements have been discussed.
2 citations
TL;DR: In this paper, the mineralogical compositions of five plastic fire clays, viz. Mohuamilan, Chittorpur, Barachatarma, Neyveli and Badampahar, have been determined by chemical analysis and X-ray diffraction studies on active clay components.
Abstract: Mineralogical compositions of five plastic fire clays, viz. Mohuamilan, Chittorpur, Barachatarma, Neyveli and Badampahar, have been determined by chemical analysis and X-ray diffraction studies on active clay components (< 1 μ e.s.d.). X-ray examination was done before and after heat-treatment of clays at 600° and 1025°C. The results indicated that the dominant mineral present in all the clays belonged to the Kandite group. Mohuamilan and Chittorpur clays were well crystallized kaolinite. Illite was found to be present in small amount in Neyveli and Badampahar clays. Non-clay minerals of varying nature in varying proportions were present in all the clays.
2 citations
TL;DR: In this paper, a spectrophotometric method for the determination of calcium and magnesium in pure alumina has been developed, which involves extraction of aluminium with tri-n-butyl phosphate (TBP) at pH ∼ 4.3.
Abstract: A spectrophotometric method for the determination of calcium and magnesium in pure alumina has been developed. The method involves extraction of aluminium with tri-n-butyl phosphate (TBP) at pH ∼ 4.3. Magnesium and calcium are then determined in aqueous solution at pH ∼ 7.80 and at pH ∼ 12 using eriochrome black T (EBT) and P&R as metallochromic indicators at 540 and 560 nm respectively. The method obeys Beer's law from 0.2 to 3.0 μg MgO/ml and 0.2 to 4.0 μg CaO/ml respectively. Traces of titanium (if present) are effectively masked with triethanol amine (TEA), but traces of iron (if present) are extracted with aluminium. The interferences of Co, Ni, Cu and Mn can be avoided by masking with KCN. The method has been applied to synthetic and various pure alumina samples.
1 citations
TL;DR: The effect of incorporating ZrO2 and TiC on different mechanical properties as well as the performance of alumina based ceramic cutting tools has been studied in this paper, where it was observed that these tools were useable successfully even at a cutting speed of 350 m/min and up to that limit, the increase in cutting speed had a slightly negative effect on their performances while the wear rate was more sensitive to the variation of depth of cut.
Abstract: The effect of incorporating ZrO2 and TiC on different mechanical properties as well as the performance of alumina based ceramic cutting tools has been studied. Along with the mechanical properties of the tool materials, the importance of tool geometry and the effect of different cutting parameters, viz. cutting speed, feed and depth of cut, on the tool life have also been discussed. It was observed that these tools were useable successfully even at a cutting speed of 350 m/min and up to that limit, the increase in cutting speed had a slightly negative effect on their performances while the wear rate was found to be more sensitive to the variation of depth of cut. Addition of TiC and ZrO2 improved their performances for the applications requiring very high speed and high depth of cut respectively.
1 citations
TL;DR: In this article, the densification behavior of powder compacts of technical grade alumina in relation to variations in powder treatments and fabrication methods was studied and it was shown that it was necessary to obtain green specimens with density higher than a critical value in order to sinter these to high densities at a specified temperature.
Abstract: The densification behaviour of powder compacts of technical grade alumina in relation to variations in powder treatments and fabrication methods was studied. Breaking down the agglomerates in the raw material by ball milling helped achieving high density. The results obtained in this investigation showed that it was necessary to obtain “green” specimens with density higher than a critical value in order to sinter these to high densities at a specified temperature.
1 citations
TL;DR: In this article, a spectrophotometric method for the determination of traces of aluminium in titanium oxide has been described based on selective extraction of titanium as TiCl4.2TBP (TBP = tri-n-butyl phosphate) with TBP in CCI4 in 11N HCI medium.
Abstract: A spectrophotometric method for the determination of traces of aluminium in titanium oxide has been described. The method was based on selective extraction of titanium as TiCl4.2TBP (TBP = tri-n-butyl phosphate) with TBP in CCI4 in 11N HCI medium. Aluminium was then determined at pH 5.3 with xylenol orange in presence of tartaric acid in aqueous medium by measuring the extinction at 530 nm. The deleterious effect of traces of titanium left unextracted in the aqueous medium has been taken care of and removed by masking with H2O2. The method obeyed Beer's Law up to 2 μg Al2O3/ml and yielded satisfactory results in its application to different titania samples.
1 citations
TL;DR: In this article, the various parameters affecting plasticity, namely pH, base exchange capacity (bec), humic acid content and mineralogical composition of the Padappakkara area in Quilon District of Kerala have been investigated.
Abstract: There is a reserve of 1.3 million tons of ball clay in the Padappakkara area in Quilon District of Kerala. This is a potential plastic clay deposit of south India. The various parameters affecting plasticity, namely pH, base exchange capacity (bec), humic acid content and mineralogical composition of this clay have been investigated in the present work. The properties of this clay have also been compared with those of the plastic clays from Payyangadi (Kerala), Bikaner (Rajasthan), Bimadole (Andhra Pradesh), Than (Gujarat), Westerwald (West Germany) and Inagaki-kibushi (Japan). A regression analysis was also done to correlate the properties of clays with plasticity.
TL;DR: An integrated scheme for chemical analysis of soda-lime-silica glass and a few other silicate raw materials, having the following significant features, has been developed as mentioned in this paper, where nickel and teflon wares have been introduced in the place of costly platinum articles, interferences due to nickel as contaminant during fusion and silica from the matrix have been overcome by external addition of Al3+ as collector and O-phenanthroline as masking agent.
Abstract: An integrated scheme for chemical analysis of soda-lime-silica glass and a few other silicate raw materials, having the following significant features, has been developed.(a) Nickel and teflon wares have been introduced in the place of costly platinum articles; (b) interferences due to nickel as contaminant during fusion and silica from the matrix have been overcome by external addition of Al3+ as collector and O-phenanthroline as the masking agent; (c) use of toxic KCN which is invariably used in the common analytical processes has been done away with; and (d) the time and cost of an analysis have been drastically reduced.Following the developed scheme, samples of soda-lime glasses, clays etc have been analysed. The results show a satisfactory conformity with those obtained by standard methods.
TL;DR: In this article, four samples of sillimanite rocks of Chippilangso, Karbi Anglong, selected on the basis of their colours, were investigated by X-ray powder diffraction and IR absorption spectra.
Abstract: Four samples of sillimanite rocks of Chippilangso, Karbi Anglong, selected on the basis of their colours, were investigated by X-ray powder diffraction and IR absorption spectra. A variety of sillimanite was found in the pink (PV) as well as in the silky white (QS) coloured rocks, while another variety of the same mineral was found in the white coloured massive rock (MS). Besides these, α-quartz and kaolinite were found to be the other major constituents of the rocks. Also, the rocks were found to contain muscovite, magnetite, and hematite as minor constituents. The yellow coloured rocks (WV) were found to consist of only α-quartz. Unit cell dimensions and densities of the sillimanite form, occurring in MS, are: a1 = 7.459 A, b1 = 7.649 A, c1 = 5.739 A, α1 = β1 = γ1 = 90°, Dm = 3.25 gm.cm−3, Dx = 3.27 gm.cm−3, and of the sillimanite, occurring in PV and QS rocks, are: a2 = 7.445 A, b2 = 7.636 A, c2 = 5.762 A, α2 = beta;2 = γ2 = 90°, Dm = 3·26 gm.cm−3, Dx = 3.28 gm.cm−3.Both the varieties of the sillimanit...
TL;DR: The effect of starting material purity and reactive atmosphere on six fluorozirconate glass compositions was examined in this article, and the results showed that there appeared to be no correlation between material purity with the value of glass formability index (Tx-Tg).
Abstract: The effect of starting material purity and reactive atmosphere on six fluorozirconate glass compositions was examined Compositions made with low purity starting materials showed a high degree of surface crystallization with absorption bands, tails, or shoulders present in the UV-Vis spectra A shoulder located off the IR cutoff was also present in all low purity glass compositions The high purity compositions exhibited sharp UV and IR cutoffs at ∼ 210 nm (47,600 cm−1) and 7575 nm (1320 cm-1), respectively Tg and Tx values were determined for each composition using a DSC There appeared to be no correlation between material purity and the value of glass formability index (Tx–Tg)
TL;DR: In this paper, the application of infrared and thermal analysis methods for identification of clay minerals in petroleum reservoir rocks of Naharkatia oil field has been investigated and the results were confirmed by X-ray powder diffraction method.
Abstract: The application of infrared and thermal analysis methods for identification of clay minerals in petroleum reservoir rocks of Naharkatia oil field has been investigated. Thermal analysis provided little information regarding the nature of clay minerals unless most of the heavier non-clay materials of the reservoir rocks were separated. Clay minerals in the reservoir rocks without separation of the non-clay materials could however be identified by the infrared technique. Both thermal and infrared analysis revealed presence of illite and chlorite type clay minerals in Barail reservoir rocks of Naharkatia oil field. The findings were confirmed by X-ray powder diffraction method.
TL;DR: In this paper, electron paramagnetic resonance (EMR) was used to study the oxidation-reduction reactions of vermiculite mineral in the interlayer space, and it was shown that oxidation took place during evacuation while reduction occurred in course of H2 treatment.
Abstract: The oxidation-reduction reactions Fe2+⇌Fe3+ in vermiculite mineral have been studied by the electron paramagnetic resonance technique. The results obtained in a mineral containing essentially Mg2+ and Mg-vermiculite replaced with 0.18% of Pt ion in the interlayer space were compared. It has been shown that oxidation took place during evacuation while reduction occurred in course of H2 treatment.
TL;DR: In this paper, the results of a series of experiments carried out with a view to assessing the extent of such changes within certain permissible limits even on repeated firing were presented, and the results showed that 5 to 10 per cent variations were within normal limits.
Abstract: In an integrated circuit the substrate on which various passive devices are printed and fired, a resistor or resistors are quite often required to be retired at different periods of time. It has been observed that such firing either results in large increase or decrease in the resistivity which are usually not desirable. Variations of 5 to 10 per cent are however considered to be within normal limits.
The present paper contains the results of a series of experiments carried out with a view to assessing the extent of such changes within certain permissible limits even on repeated firing.
TL;DR: In this article, the reflections of Ni- and Cu-montmorillonite after dehydration at 200° to 600°C in vacuum are presented, and the results have been interpreted in terms of Hofmann-Klemen effect and sluggish swelling of the mineral.
Abstract: The (001) reflections of Ni- and Cu-montmorillonite after dehydration at 200° to 600°C in vacuum are presented. d001 values of both the vacuum treated samples were measured after exposing them to water and ethylene glycol for 3, 5, 15 and 25 days. The vacuum-treated samples were further subjected to H2 atmosphere at the same temperatures (200°–340°C) and exposed to the two liquids and then the XRD study was carried out. The results have been interpreted in terms of Hofmann-Klemen effect and sluggish swelling of the mineral.
TL;DR: In this paper, a new chemical bond on magnesia refractories was proposed, which was evaluated by compressive creep experiments with a compressive load of 3 kg.cm−2 up to 1500°C for 30 hrs and showed a maximum strain rate of 0.2% per hour without failure.
Abstract: The present paper is the third of a series of papers on a new chemical bond on magnesia refractories. Results of the compressive creep testing of the chemically bonded samples at elevated temperature up to 1500°C, prepared from sea-water magnesia (Japan) and natural magnesite (Salem, India), cured at 110°C for 24 hrs, have been presented in this part. Samples prepared with the bond (0.25 wt%) evaluated by creep experiments with a compressive load of 3 kg.cm−2 up to 1500°C for 30 hrs showed a maximum strain rate of 0.2% per hour without failure. This makes it an acceptable chemical bond of the future for magnesia refractories. The deformation mechanism suggested a diffusion controlled Nabarro-Herring creep, while a grain-boundary diffusion process might also be a possibility.
TL;DR: Ipomoea carnea stems were dried and graphitized in a resistance furnace in two phases, and the surface of graphitized carnea was observed by using a scanning electron microscope as mentioned in this paper.
Abstract: Ipomoea carnea stems were dried and graphitized in a resistance furnace in two phases. The surface of graphitized ipomoea carnea was observed by using a scanning electron microscope. Crystallinity of the material was examined by X-ray diffractometry. A low grade graphitization of ipomoea carnea was observed.
TL;DR: In this article, the early stages of sintering in alumina powder compacts have been studied, and two different alumina materials having medium particle sizes of 0.8 and 3.5 microns have been used.
Abstract: The fundamental characteristics of the early stages of sintering in alumina powder compacts have been studied. Two different alumina materials having medium particle sizes of 0.8 and 3.5 microns have been used. In conjunction with densification data, the techniques of BET surface area analysis and mercury porosimetry have been used to analyse the progress of sintering process in alumina between 1050° and 1350°C.Reduction in surface area with increasing temperature was more rapid in compacts of fine particles than in the other. The particle packing was inhomogeneous in the fine powder specimens; it was homogeneous in the coarse powder samples and pore size distribution was sharp. Non-uniform sintering in the compacts of fine powders occurred as a consequence of broad and multi-modal porosity distribution in the ‘green’ specimens. Pore growth was observed, which possibly occurred as a result of coalescence of small pores.
TL;DR: In this article, powder X-ray diffraction (XRD) and Mossbauer spectroscopic methods have been used for the characterization of aluminium in intergranular and institutional minerals.
Abstract: Aluminium occurs both as substitution of iron within the structures of iron ore minerals, viz. hematite, goethite etc and in intergranular minerals, occurring as gangue minerals like iron silicates. The characterization (substitutional or intergranular) of aluminium is necessary to optimize the cost of beneflciation and is successfully done by powder X-ray diffraction (XRD) and Mossbauer spectroscopic methods. The results of these methods as used for this purpose have been discussed here with the effect of aluminium substitution for each parameter.
TL;DR: In this paper, the effect of boron, B4C, Al2O3, C, and alumina with carbon additions on the sintering behavior of silicon carbide powders obtained by silicon-carbon reaction and silica carbon reaction was investigated.
Abstract: The effect of boron, boron carbide and alumina, all with carbon additions, on the sintering behaviour of silicon carbide powders obtained by silicon-carbon reaction and silica-carbon reaction was investigated. The concentrations of these additives—B, B4C, Al2O3, C—were varied up to 5 wt%. Sintering investigations were carried out at 2000°C in argon atmosphere. The effectiveness of the additive as a sintering aid decreased from boron to boron carbide to alumina. In all these cases, presence of carbon up to 5 wt% was essential. X-ray diffraction and scanning electron microscopic studies have shown that the sintered samples with boron and boron carbide additives existed in the beta phase, while the alumina incorporated specimens underwent transformation into the 4H-alpha polytype.
TL;DR: In this article, the effect of granulation on the tap density, green density and compaction ratio of the thoria-10 mole% yttria powder has been studied.
Abstract: One end closed thoria—10 mole% yttria tubes have been fabricated by isostatic pressing. The effect of granulation on the tap density, green density and compaction ratio of the thoria—10 mole% yttria powder has been studied. The bodies have been obtained from—44 mesh sized granules by isostatically compacting at a pressure of 1750 kg.cm”−2 and sintering at 2000°C. The bodies were found to possess a density of 98% T.D. with uniformly sized grain structure.
TL;DR: In this article, two ZrF4-BaF2-LaF3-AIF3 (ZBLA) glasses were immersed in a buffered base at 25°C for several days.
Abstract: Two ZrF4—BaF2—LaF3—AIF3 (ZBLA) and four ZrF4—BaF2—YF3—AIF3 (ZBYA) glasses were immersed in a buffered base at 25°C for several days. They were then examined using an IR spectrophotometer in order to determine the effect on the optical properties, and a microhardness tester for surface degradation. The ZrF4 content in these compositions ranged from 44 mol% to 57 mol%. IR analysis showed that the amount of hydroxyl and H2O penetration was dependent upon the concentration of ZrF4 in the glass. The IR characteristics of ZBYA—1, which contained 44 mol% ZrF4, did not appear to be affected by the aqueous environment, while ZBLA—20, which contained 57 mol% ZrF4, showed the presence of a large amount of hydroxyl and H2O. The base immersion did not appear to strongly affect the microhardness of the compositions.