Author
Ashok Mohan
Bio: Ashok Mohan is an academic researcher. The author has contributed to research in topics: Sintering & Solid solution. The author has an hindex of 2, co-authored 8 publications receiving 31 citations.
Papers
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TL;DR: In this paper, the sintering behavior of ammonium diuranate prepared by different methods, was studied in an atmosphere of hydrogen and significant differences in the Sintering (densification) behaviour of the powders were noted under identical sinterings (firing) treatments.
Abstract: It was shown earlier that uranium dioxide derived from different compounds exhibited variations in the sintering behaviour and to attain maximum densification, the sintering should be carried out within a temperature range, specific for each of the powders.In the present work, the sintering behaviour of uranium dioxide derived from ammonium diuranate prepared by different methods, was studied in an atmosphere of hydrogen. Significant differences in the sintering (densification) behaviour of the powders was noted under identical sintering (firing) treatments. The influence of variations in sintering treatment, such as rates of heating or soaking periods, on the densification of the samples of different origins was studied. It was found that the sintering behaviour depended on both the powder characteristics and the sintering treatment. Attempts were made to relate the origin and thermal history of the UO2 with its powder characteristics; and its sintering behaviour to its powder characteristics and the fir...
26 citations
TL;DR: In this paper, a computer program has been used which can accommodate a large number of variables and mechanisms simultaneously, and a modification in the method of constructing sintering mechanism diagrams has also been suggested to yield additional important information.
Abstract: The classical approach to determining the sintering mechanism by exponent method, as proposed by Kuczynski, has become increasingly reliable with modifications and refinements suggested subsequently. However, it still has some limitations in clearly defining mechanisms, especially when more than one mechanism is operative. Ashby has suggested a method of constructing sintering mechanism diagrams and has effectively overcome some of these limitations. In addition, his method is potentially able to contend with a large number of sintering variables and mechanisms simultaneously.In the present work, a computer programme has been used which can accommodate a large number of variables. A modification in the method of constructing sintering mechanism diagrams has also been suggested to yield additional important information.
3 citations
TL;DR: In this paper, three sets of UO2-ThO2 mixtures, varying in their powder characteristics, were sintered between 1250°c and 1550°C for different soaking periods.
Abstract: The literature survey on sintering of binary oxide systems like UO2-ThO2 shows a vast difference of opinion on the effect of composition on sintering of mixtures. Three sets of UO2-ThO2 mixtures, varying in their powder characteristics, were sintered between 1250°C and 1550°C for different soaking periods.The results are explained on the basis of a proposed concept of sintering. This concept, seems to adequately explain the large variations in the sintering behaviour of such oxides., reported in this work as well as in the work of earlier authors.
1 citations
TL;DR: In this paper, the formation of solid solution during sintering treatment has a significant effect on the densification behavior of the oxide mixtures and the influence of temperature and composition on the solid solution formation was studied.
Abstract: UO2 and ThO2 are known to form a continuous series of solid solutions over the entire range of composition. The formation of solid solution during the sintering treatment has a significant effect on the densification behaviour of the oxide mixtures. Attempts were made to study the solid solution formation in this system by X-ray diffraction technique.The influence of temperature and composition on the solid solution formation was studied. An indication of the role of diffusion in material movement was obtained by tracing the progress of solid solution formation with change in the heat treatment. Lattice parameters of UO2-ThO2 solid solutions were also determined.
1 citations
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TL;DR: The physical characteristics of thorium oxalate powders are dependent upon the precursor material and the calcining temperature, and the physical properties of the resulting oxides determined as mentioned in this paper.
40 citations
TL;DR: In this paper, the crystallinity in UO2 powders prepared by the ADU route at different calcination temperatures (600°-1600°C) and its influence on their sintering behavior (sintering temperature 1000° -1600°c) in hydrogen were studied by X-ray difiraction techniques.
Abstract: The crystallinity in UO2 powders prepared by the ADU route at different calcination temperatures (600°-1600°C) and its influence on their sintering behaviour (sintering temperature 1000°-1600°C) in hydrogen were studied by X-ray difiraction techniques. Powder patterns were made for the loose powders and back reflection for the sintered pellets. It was noticed that higher the calcination temperature, the greater was the degree of crystallinity developed in the powders and poorer was their sinterability. The crystallinity of the sintered pellets was mainly dependent on the sintering temperature and crystallinity of the original powder and is not directly related to the sintered density. By sintering pellets of poorly crystalline powders at low temperatures (about 1200°C) sintered pellets of near theoretical density but with poorly developed crystallinity could be obtained.
24 citations
TL;DR: Ceramics are widely accepted as nuclear reactor fuel materials, for both metal-clad ceramic and all-ceramic fuel designs as mentioned in this paper, and are used commercially in large tonnages in five different power reactor designs.
15 citations
TL;DR: In this article, it has been shown that the sinterability of oxides depends on the origin and thermal history of the powders and that the crystallinity of the oxides can be assessed on a comparative basis by determination of the streaming potentials.
Abstract: It has been shown that the sintering behaviour of oxides depends on the origin and thermal history of the powders. Physical characteristics of the powder such as, surface area, particle size etc were not found to be adequate to explain the sintering behaviour. It is also shown that the sinterability is directly related to the crystallinity in the powders. The crystallinity of the powders can be assessed on a comparative basis by determination of the streaming potentials. An apparatus has been set up to determine the streaming potentials of urania powders. It was found that the slope of the streaming potentials vs. velocity of flow plots was a direct indication of the comparative sinterability of the urania powders.
9 citations
TL;DR: In this paper, a study was made on the kinetics of sintering of UO2powders derived from ADU at different calcination temperatures, where the powders were calcined between 500° and 1500°C and the densification characteristics of the pellets made from these were evaluated for different soaking times.
Abstract: A study has been made on the kinetics of sintering of pellets prepared from UO2powders derived from ADU at different calcination temperatures. The powders were calcined between 500° and 1500°C and the densification characteristics of the pellets made from these were evaluated for different soaking times from 10 to 1000 mts at sintering temperatures between 1000° and 1500°C. Data were analysed using the empirical equation where D is the density, C and K are constants and t denotes time.It was found that (i) the progress of sintering, (ii) attainment of limiting densities and (iii) variation in rates of densification at different temperatures and time can be explained on the assumption that material movement (hence densification) is governed by the number, nature and energy of crystalline defects (flaws) in the original powders.
7 citations