Showing papers in "Transactions of The Indian Ceramic Society in 1970"
TL;DR: In this paper, the influence of various fabrication parameters viz., calcination temperature, grinding period, sintering temperature and soaking time, on the initial a.c. permeability and Q-factor of Nickel-Zinc-Ferrite (Ni0.3Zn0.7 Fe2O4 samples, were made with a view to develop ferrite cores, for use at high frequencies.
Abstract: Studies on the influence of various fabrication parameters viz., calcination temperature, grinding period, sintering temperature and soaking time, on the initial a.c. permeability and Q-factor of Nickel-Zinc-Ferrite (Ni0.3Zn0.7 Fe2O4 samples, were made with a view to develop ferrite cores, for use at high frequencies. A higher calcination temperature, a lower sintering temperature and a shorter soaking period have been found desirable to attain reasonably high density coupled with a low initial permeability and high Q. Repeated calcinations interspaced with wet grinding resulted in further improvement of the properties.
5 citations
TL;DR: Using Orissa chrome ore, Almora magnetite and Salem magnetite, several chrome-magnesite and magnesite-chrome compositions were prepared and fired to temperatures between 1400°C-1700°C.
Abstract: Using Orissa chrome ore, Almora magnesite and Salem magnesite several chrome-magnesite and magnesite-chrome compositions were prepared and fired to temperatures between 1400°C-1700°C. Physical and refractory properties of the fired specimens were studied. The microstructure was examined in detail. Good direct bonding between chromite and periclase grains developed at 1700°C. The extent of direct bonding was more pronounced in compositions containing larger amount of monticellite in the matrix.
4 citations
TL;DR: In this paper, the influence of origin on the crystallinity and morphology of beryllia powders was studied, and the changes taking place in the morphology and crystallinity during calcinations/sintering of the loose powders and the pressed compacts of the powders derived from sulphate, hydroxide and oxalate have been studied.
Abstract: It has been established that the sinterability of pure oxide powders depends to a large extent on the characteristics of powder particles. It is known that the degree of crystallinity in the powders influences their sinterability. In the present investigations the influence of origin on the crystallinity and morphology of beryllia powders was studied. The changes taking place in the crystallinity and morphology during calcinations/sintering of the loose powders and the pressed compacts of beryllia powders derived from sulphate, hydroxide and oxalate have been studied. Attempts were made to relate the sintering behaviour and the changes in morphology and crystallinity of the powders.
4 citations
TL;DR: In this paper, the role of tin in large-scale production of copper ruby glass was investigated and its role has been described and described in this communication, which suggests that instead of Cu+, Sn++ might be getting preferentially reduced when tin is present, which would appear that Sn++ retards the reduction of Cu+ to Cuo in the melt.
Abstract: Tin has so far been believed to reduce cuprous copper during the striking of copper ruby colour. The new view advanced recently on production of copper ruby colour does not involve tin in the striking mechanism. As tin is essential in large-scale production of copper ruby glass, its role has been investigated and is described in this communication. Copper ruby glasses of soda-lime-silica type, with and without tin were melted. The ‘critical’ melting stage was found to be almost absent in glasses without tin whereas it lasted for a considerable period in glasses containing tin. The glasses melted without tin were grey yellow to yellow brown even on heat-treatment, indicating the presence of metallic copper. It suggests that Cu+ got reduced to Cuo in the melt. This does not happen when copper ruby glass is melted with tin. The findings indicate that instead of Cu+, Sn++ might be getting preferentially reduced when tin is present. It would appear that Sn++ retards the reduction of Cu+ to Cuo in the melt. Thu...
3 citations
TL;DR: In this article, the influence of 1% addition of minor constituents such as MgO, TiO2, Fe2O3 on the sintering behavior of beryllium oxide, both in air and in vacuum, has been studied at different sinterings temperatures from 1100°-1500°C and for soaking periods of 2, 4, and 16 hrs.
Abstract: Influence of 1% addition of minor constituents such as MgO, TiO2, Fe2O3 on the sintering behaviour of beryllium oxide, both in air and in vacuum, has been studied at different sintering temperatures from 1100°-1500°C and for soaking periods of 2, 4, and 16 hrs It was noticed that additions promote densification, more so, in air sintering and at lower temperatures (1100°-1300°C) At higher temperatures (over 1300° C) the influence was not significantly noticeable as the density of the pellets of pure BeO was fairly high—especially so in vacuum sintering A typical value of the density attained by BeO with iron oxide addition is 284 gm/cc at temperatures above 1200°C in air or in vacuum The samples with magnesia additions tend to be translucent and those with titania and iron oxide additions coloured, the colour depending on the atmosphere An attempt has been made to explain the role of the additions in promoting the sinter ability
2 citations
2 citations
TL;DR: In this paper, it was found that holes of the checkers were clogged due to dust accumulation and the chocking of the holes caused failure of refractories of the stove.
Abstract: Investigations were made on premature failure of refractories of Blast Furnace Stove. It was found that holes of the checkers were clogged due to dust accumulation. Brick surface became glazed and top few courses of t bricks were completely vitrified and deformed.Samples were collected from different zones of the stove and laboratory investigations were made. The chemical analysis and the fusion point of dust and glazed portion of brick, indicated that high dust content of blast furnace gas and prolonged dome temperature of 1250°C and the chocking of the holes were the factors that caused failure of refractories of the stove. It is suggested that for longer life of refractories the gas should be cleaner. If the temperature of the stove is required to be raised in order to increase the temperature of hot blast, the top few feet of checkers, combustion chamber walls and dome should be relined with high alumina refractories.
2 citations
TL;DR: In this article, the hydraulicity of slags was estimated from the compressive strengths of 1:3 mortars, the cements being prepared from 1.8 parts slag and 1 part hydrated lime by volume.
Abstract: Slags having three different SiO2: Al2O3 ratios (1.2,1.9 and 2.6) and three different CaO contents (44%, 39% and 34%) were prepared. These slags were classified into nine series, in each of which Al2O3 and SiO2 were kept constant and CaO was replaced by MgO in molecular proportion. The hydraulicity of these slags was estimated from the compressive strengths of 1:3 mortars, the cements being prepared from 1.8 parts slag and 1 part hydrated lime by volume. The soundness of the cements produced from some of these slags and portland cement was also measured. Hydraulicity of slag had a tendency to decrease when CaO was molecularly replaced by MgO and it practically did not change when CaO of slag was replaced by MgO on weight basis. Compressive strength increased with the increase of CaO and Al2O3 content of slag and decreased with increase of SiO2 content. The cements produced from high-magnesia slags were perfectly sound and did not show any dimensional instability.
1 citations
1 citations
TL;DR: In this article, X-ray diffraction studies and densification measurements were carried out on three compositions, TZ, TA and T respectively, heated under oxidizing and reducing atmospheres between 1200°C and 1400°C.
Abstract: X-ray diffraction studies and densification measurements were carried out on three compositions, 75% TiO2+25% ZrO2, 75% TiO2+25% Al2O3, and 100% TiO2, designated as TZ, TA and T respectively, heated under oxidizing and reducing atmospheres between 1200°C and 1400°C. The densification was always higher and the formation of the new phases took place with greater ease when the specimens were fired under reducing conditions. This was possible due to the formation of anionic vacancies in the TiO2 structure, which would enhance diffusion.
1 citations
TL;DR: In this article, a scheme for rapid accurate and complete analysis of chrome bearing materials is described for rapid and accurate analysis of chromium bearing materials, where the sample after fusion with Na2O2 in a Ni crucible was taken in H2SO4 and diluted to volume.
Abstract: A scheme has been described for rapid, accurate and complete analysis of chrome bearing materials. The sample after fusion with Na2O2 in a Ni crucible was taken in H2SO4 and diluted to volume. Separate aliquots were used for determination of SiO2 by a modified K2SiF6 method, total Fe2O3 by titration with Hg2(NO3)2 and Cr2O3 by ferrous ammonium sulphate-dichromate titration. Another aliquot was electrolysed in a mercury cathode apparatus, diluted to volume and aliquots of the solution were taken for determination of Al2O3, CaO and MgO by EDTA titration and TiO2 by spectrophotometry as yellow peroxy complex. From separate openings alkalies and MnO were estimated by flame and spectrophotometry respectively. Most of the methods are independent and selective.
TL;DR: In this paper, the electrical conductivity of sintered compacts of urania powders was investigated at temperatures between 1100°C to 1700°C by using electron microscopy.
Abstract: In an earlier investigation, it was reported that the electrical conductivity of sintered compacts of urania powders depended on the calcination temperature and the sintering treatments. In the present study, the conductivity of the samples sintered at temperatures between 1100°C to 1700°C were studied. Attempts were made to correlate the changes in the conductivity with the microstructure of the samples. The details of the microstructure were studied by electron microscopy.
TL;DR: In this article, the effect of MgO in increasing resistance against water attack was strong only in glasses having 20 mole per cent or more of Na2O. The results were interpreted in relation to the oxygen activity of the glass.
Abstract: Glasses in the system Na2O—MgO—SiO2 containing various amounts of Na2O and MgO were subjected to the action of water and the amounts of the constituents extracted were analysed chemically. The effect of MgO in increasing the resistance towards water attack was strong only in glasses having 20 mole per cent or more of Na2O.The molar ratio SiO2: Na2O in the extract was not the same as in the glass. Generally it increased with an increase of the SiO2: Na2O ratio in the glass composition. The molar ratio of MgO to SiO2 in the extract decreased with increasing value of the same in the glass and was nil at about 20 to 31 mole per cent of alkali in the glass.Values of the equilibrium pH were determined for all the glasses. At a constant Na2O content, the pH values passed through a minimum with the replacement of SiO2 by MgO. The results were interpreted in relation to the oxygen activity of the glass. Equilibrium pH also appeared to have linear relationship with logarithm of alkali extractions, with slopes varyi...
TL;DR: In this article, Li2O-Al2O3-SiO2 and PbO-al2O 3.6SiO3.2SiO 2 were analyzed for varying heat treatment schedules, in order to observe their crystallisation behavior.
Abstract: Four glass compositions corresponding to Li2O.Al2O3.4SiO2, Li2O.Al2O3.6SiO2, PbO.Al2O3.2SiO2, and PbO.Al2O3.6SiO2, in the systems Li2O-Al2O3-SiO2 and PbO-Al2O3-SiO2 respectively were melted, and were subjected to DTA and X-ray analysis for varying heat treatment schedules, in order to observe their crystallisation behaviour.For glass compositions corresponding to PbO.Al2O3.2SiO2 and PbO.Al2O3.6SiO2, lead aluminium silicate (PbO.Al2O3.2SiO2)was the first phase to crystallise in all cases. Whereas for the glass corresponding to Li2O.Al2O3.6SiO2 composition, keatite was the only predominant phase crystallised. In the case of glass composition corresponding to Li2O. Al2O3.4SiO2, however, keatite solid solution with possible traces of Silica-O was present.
TL;DR: In this paper, the constitution and mineralogy of Indian blast furnace slags were investigated using chemical, petrographic and X-ray diffraction methods, and Melilite was the most predominant mineral constituent in all the slags.
Abstract: The constitution and mineralogy of Indian blast furnace slags were investigated. Chemical, petrographic and X-ray diffraction methods were followed. All the slags were high in alumina. Melilite was the most predominant mineral constituent in all the slags. Other minerals identified were diopside, spinel, oldhamite, enstatite, forsterite and monticellite. Varying proportions of glass were present in all the slags.
TL;DR: The effect of forming pressure on the physical properties and high temperature load bearing characteristics of Magnesite, chrome-magnesite and magnesite-chrome bricks prepared under industrial conditions has been discussed in this article.
Abstract: The effect of forming pressure on the physical properties and high temperature load bearing characteristics of magnesite, chrome-magnesite and magnesite-chrome bricks prepared under industrial conditions has been discussed. It has been suggested that the physical properties of these refractories and their resistance to creep under compressional load at high temperature in particular, showed considerable improvement when the forming pressure exceeded 800 kg/cm2.
TL;DR: In this article, the effect of raw materials used in the synthesis of manganese-zinc ferrites on the magnetic parameters were studied and the influence of sintering atmospheres on magnetic permeability and temperature dependence of permeability, loss, disaccommodation and induction were examined.
Abstract: The electromagnetic properties of manganese-zinc ferrites are strongly affected by the synthesis parameters. The influence of sintering atmospheres on magnetic permeability, temperature dependence of permeability, loss, disaccommodation and induction were examined. The effect of the types of raw materials used in the synthesis on the magnetic parameters were studied.Based on these studies, commercially important ferrites suitable for various practical applications have been synthesised.
TL;DR: In this article, samples of seven alumino-silicate refractory compositions were subjected to thermal-shocks of increasing severity and their spalling characteristics were studied in relation to their strength and porosity, as well as development of cracks in them.
Abstract: Samples of seven alumino-silicate refractory compositions prepared from china clay, quartz and calcined alumina had been subjected to thermal-shocks of increasing severity and their spalling characteristics were studied in relation to their strength and porosity, as well as development of cracks in them.
TL;DR: In this article, the authors describe various steps involved in the manufacture of barium ferrite magnets and different items of machinery required at each step. Importance of proper mixing, ball milling, compacting and sintering to obtain optimum properties is also discussed.
Abstract: Due to uncertain availability of nickel at reasonable prices in the world market for the manufacture of alnico magnets for diverse uses in the light electrical industry, there is an urgent need for their replacement by the barium ferrite magnets which can easily be made at low cost from the indigenously occurring raw materials. The ferrite magnets are made from principal ingredients barium carbonate and iron oxide by conventional powder metallurgy techniques employed for the fabrication of metal and ceramic components. The paper describes in some detail various steps involved in the manufacture of these magnets and different items of machinery required at each step. Importance of proper mixing, ball milling, compacting and sintering to obtain optimum properties is also discussed.
TL;DR: Bloating type of refractories including ladle bricks, stopper heads and nozzles are reported to behave in a better way than the conventional non-bloating types of similar refractors as mentioned in this paper.
Abstract: Bloating type of refractories including ladle bricks, stopper heads and nozzles are reported to behave in a better way than the conventional non-bloating type of similar refractories To develop this type of refractories preliminary investigations have been carried out and results indicate the possibility of producing such refractories from the compositions having ordinary ferruginous clays containing about 6–7% Fe2O3 along with some alkalies and CaO Bloating was found to be due to the evolution of SO2 at about 1250°C Gypsum and salt-cake may be used advantageously Compositions have been developed with 10–15% linear expansion at 1400°C
TL;DR: In this paper, the requirements of the orthopœdic plaster specified by the Indian Standard specification can be satisfied only with high purity mineral gypsum or selenite.
Abstract: The requirements of the orthopœdic plaster specified by the Indian Standard specification can be satisfied only with high purity mineral gypsum or selenite. These quality minerals are not available in abundance. To meet the demands for the product, beneficiation studies were carried out with a substandard gypsum mineral from Jammu. The method developed has shown the possibility of upgrading the mineral, otherwise unsuitable for the purpose, to the desired degree so as to conform to the specification. The plaster so prepared was found to have a better strength.
TL;DR: In this paper, the amount of thixotropy was rheologically characterised in terms of the thixotropic coefficient as calculated from "breakdown with time curve" and some properties have also been correlated through this coefficient.
Abstract: Electrolytes containing cations of different valencies were interacted with Na-Bentonite suspension and the corresponding thixotropic concentrations were determined. The amount of thixotropy was rheologically characterised in terms of “thixotropic coefficient” as calculated from “breakdown with time curve”. Some of the properties have also been correlated through this coefficient.