Volume 1, Issue 1
May 1979, pages 1-79
pp 1-14 May 1979
This paper reviews briefly many aspects concerning the processing of materials in space. Under micro-gravity conditions many phenomena like convection, liquid flow, etc., are profoundly affected and surface tension forces may take over in some of the heat transfer processes. There are many advantages in studying the various materials processing techniques like electrophoresis, crystal growth, liquid phase miscibility gap and in preparing eutectic alloys, magnetic materials and composites under space conditions. Some of the recent results of such space experiments are presented. The physics of the molecular shield used for reducing the pressures at altitudes of 200 or 300 km by 5 orders of magnitude is discussed. The article concludes with a description of the space shuttle facility and some possible experiments that may be done on it.
pp 15-34 May 1979
Crystallography of alpha-quartz is discussed with special reference to the existing ambiguities regarding handedness of its enantiomorphic forms and a mnemonic has been suggested. Previous x-ray diffraction topographic studies of synthetic quartz are critically reviewed and analysed to understand the origin, nature and location of dislocations. It is suggested that dislocations associated with cell boundaries, characteristic of the Z-zone grown portions of synthetic quartz, are pure a-type edge dislocations but possibly with an alternating non-conservative climb component associated with the predominating glide component.
pp 35-41 May 1979
Research and development on glass fibres was started at the Indian Institute of Technology (IIT), Kanpur, about three years ago. The two main directions in which efforts have been concentrated are (i) development of indigenous technology for producing glass fibres, (ii) development of new glass compositions for drawing fibres having novel physical properties. In this note, we briefly describe the activities of this group and some of the salient results obtained so far.
pp 43-47 May 1979
A programme jointly launched by Bhabha Atomic Research Centre, Trombay and Reactor Research Centre, Kalpakkam to develop indigenously, niobium titanium alloys for superconducting magnets is described. Results of short sample tests on specimens with different treatment are presented. Future plans are also outlined.
pp 49-57 May 1979 Research Communications
A detailed study of permeability spectra of polycrystalline pure and Aland Gd-Substituted garnets has been carried out for different values of grain diameter and magnetisation. The spectra are of three types—resonance, relaxed and mixed. It has been shown that the resonance spectra occur when the closure demains are absent and the domain wall is anchored at the grain boundary. The relaxed spectrum is found for domains having closure flux while the mixed spectrum is an indication of simulataneous presence of grains with and without closure domains.
pp 59-62 May 1979 Research Communications
pp 63-66 May 1979 Research Communications
La1−xSr−xFeO3 (0·1⩽x⩽0·4) samples exhibit nearly the same low resistivity value around the Neél temperatures. AboveTN, electrons seem to become itinerant as suggested by Mōssbauer data.
pp 67-69 May 1979 Research Communications
Thermo Gravimetric Analyis (TGA) shows that incorporation of Co3+ considerably reduces the oxygen loss at high temperatures in LaNiO3. Electrical resistivity of LaNi1−xCoxO3 (x⩽0·2) is essentially independent of oxygen partial pressure in the 600–1000 K range.
pp 71-75 May 1979 Research Communications
The dielectric behaviour of K2SO4-ZnSO4 glasses have been investigated. These glasses exhibit subglassy relaxations close to glass transition temperature. The relative dielectric permittivities exhibit sharp rise nearTg which may be due to loosening of glass constituents leading to ionic dipolar or electrode polarisation contributions.
pp 77-78 May 1979
pp 79-79 May 1979
Volume 42 | Issue 6
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