Volume 21, Issue 1
February 1998, pages 1-105
pp 1- February 1998
pp 1-70 February 1998 Review Article
A broad-spectrum review of the applications of electron spin resonance to advanced materials is presented. Starting with basic concepts the reader is taken through a quick tour of techniques including continuous-wave and pulse ESR, microscopy and imaging, as well as a few emerging techniques. Applications of spin identification, spin counting, spin mapping and spin imaging of a variety of advanced solid state materials including metals and alloys, semiconductors, inorganics, electroceramics, catalysts, intercalates, polymers, glasses, and organic charge-transfer complexes besides superionic conductors and high-temperature superconductors are included. It is thus demonstrated that the technique is at once specific, sensitive to composition, phase and texture yet accurate enough to be a quantitative but non-invasive tool that promises to be useful in the study of newer and newer materials including multilayers, ferrofluids and nanomaterials.
pp 71-75 February 1998 Research Articles
X-ray and electron diffraction data from the Al-Cu-Fe icosahedral phase are compared and analysed on the basis of the microcrystalline and multi-domain model developed by the author. It is shown that a crystallographic explanation is now possible for both the enigmatic five-fold symmetry and non-periodicity of reflections observed in electron diffraction patterns of icosahedral phases.
pp 77-80 February 1998 Research Articles
Fine samples with nominal composition of Bi1·6Pb0·4Sr2Ca2Cu3Ox have been produced by solid state method using various purity grades of starting copper oxide powder. Studies onTc and high-Tc volume fraction measurements of these samples revealed that the samples produced using CuO powders obtained in laboratory after double purification of the commercially available copper salts have higherTc (104·46 K) and increased percentage of highTc volume fraction (58%) compared to even the samples prepared from Aldrich grade (99·99%) CuO. A simple and cost-effective chemical route for the purification of CuO from commercially available copper salts has been outlined.
pp 81-86 February 1998 Research Articles
Powders of tetragonal (t)ZrO2 have been prepared by a solid state reaction between sodium metazirconate and sodium metaphosphate. The reaction temperatures and times have been varied between 450 and 550°C and 5 and 75 h, respectively. Zirconia powder, mostly in thet andt′ phases, is obtained. The yield of ZrO2 powder increases monotonically with time at all reaction temperatures according to a phase boundary controlled kinetics. The fraction oft phase also increases with time at 450°C and 500°C but goes through a maximum at 550°C, the highest temperature employed. A maximum of 55% of the precursor monoclinic zirconia (used to prepare sodium meta zirconate) is converted tot phase at 500°C/75 h. The ZrO2 powder consists of crystallites of size 9–25 nm agglomerated into particles having average size between 2 and 4µm. The agglomerates have a breaking strength of 100 MPa. A hydrothermal treatment is found to break the agglomerates into smaller sizes. Grinding the powder in a mortar and pestle converts only 12% of thet phase into monoclinic, indicating that substantial fraction of the tetragonal phase is the non transformable varietyt′. Heating experiments also confirm this.
pp 87-92 February 1998 Research Articles
We report here on the optical and structural characteristics carried out on strontium doped calcium tartrate tetrahedral single crystalline materials obtained by diffusing calcium and strontium ions through silica gel impregnated with optically active tartaric acid. Linear optical properties of this material such as refractive index, birefringence and transmission characteristics were measured in the wavelength range 200 nm <λ<1500 nm. No dispersion of the birefringence was observed within the experimental accuracy. The packing of tartrate molecules remained unaltered with 12% of the strontium doping.
pp 93-97 February 1998 Research Articles
In recent years, there has been a wide interest in fillers which improve the quality and performance of fibre composites when mixed in a small quantity in the matrix. In the present work the effect of addition of mica and graphite powders in cross ply glass fibre reinforced plastic (GRP) composites has been studied by using acousto ultrasonic (AU) technique. The mechanical strengths of these composites were correlated with fibre volume fraction (Vf). The stress wave factor (SWF) was evaluated and correlated with tensile/flexural strengths of these composite specimens. The observations show a linear relationship between the SWF values and strength of unfilled and filled GRP composites.
pp 99-103 February 1998 Rapid Communication
The composition of Pt-Rh alloys that co-exist with Rh2O3 in air have been identified by experiment at 1273 K. The isothermal sections of the phase diagram for the ternary system Pt-Rh-O at 973 K and 1273 K have been computed based on experimentally determined phase relations and recent thermodynamic measurements on Pt1−XRhX alloys and Rh2O3. The composition dependence of the oxygen partial pressure for the oxidation of Pt1−XRhX alloys at different temperatures, and temperature for the oxidation of the alloys in air are computed. The diagrams provide quantitative information for optimization of the composition of Pt1−XRhX alloys for high temperature application in oxidizing atmospheres.
pp 105-105 February 1998 Book Review
Volume 42 | Issue 5
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