S. Bhattacherjee

Mechanical and dielectric properties of pineapple fibres

Pineapple fibres are well known for their commercial uses in making fabrics especially in northeastern India. Although other natural cellulose fibres like cotton, jute, ramie, hemp, etc., have been widely studied for their various properties [1-4], no work appears to have been reported on these industrially potential fibres. Hence a study of the structure and various mechanical and dielectric properties of the fibres was undertaken to help the users to better utilize this commercially cheaper variety of fibres. For this purpose a specimen of pineapple fibres from Manipur, India was selected. The fibres were first purified from fat, wax and lignin by successively treating them with an alcohol-benzene mixture and sodium chlorite solutions, respectively. The purified sample was then first subjected to thermal and X-ray analyses. The differential thermal analysis (DTA) curve showed two endothermal peaks at 150 and 250°C, respectively, indicating a two stage dehydration of the fibres and an exothermal peak at 500 ° C which is due to the burning of the organic matter and possible emergence of some new phase. X-ray diffraction patterns were recorded with the help of a Philips X-ray diffractometer adopting the procedures as described by Mukherjee and Mitra [5]. The values of the lattice parameters obtained from the X-ray diffraction pattern after due correction are a = 8.32A.U., b = 10.3A.U., c = 7.93A.U. and ~ = 82.6 ° . These data conform well with the structure of cellulose type-I [4]. An estimation of the degree of crystallinity [Icryst/Ito~] was made from the X-ray diffractogram by applying the technique

Thermal transformation in a chrysotile asbestos

Structural changes accompanying thermal transformation in a chrysotile asbestos sample of Indian origin upto a temperature of 900°C have been investigated by x-ray method. The changes in lattice parameters have been systematically measured by applying a least square refinement technique and the crystallite size and strain defects at different stages have been estimated by line profile analysis of the diffraction peaks. The present study also confirms the earlier results on stepwise transformation of chrysotile fibres. This sequence of transformation has been explained assuming two different types of crystallites as reported in kaolinite.

Electrical properties of ramie fibres

We make a in-depth systematic study of the electrical properties of powdered ramie fibre samples instead of a bundle of fibres, under different conditions, to achieve a better understanding of the structure property relation in this cellulosic fiber

Study of Dehydration Transformation in Kaolinite by RDF Analysis

Structural changes in kaolinite during dehydration have been studied by calculating the radial distribution function from the X-ray diffraction intensities. An estimate of the inter-atomic distances, relative strength of the couplings and the coordination numbers has been obtained for the samples at room temperature and heated at higher temperatures. The results show high stability of the silicon tetrahedral layer compared to the Al-O-(OH) octahedral one.

Dehydration and phase transformation in chrysotile asbestos—A radial distribution analysis study

Radial distribution analysis of x-ray intensities diffracted by chrysotile samples untreated and treated at different temperatures upto 900°C has been carried out. Interatomic distances, coordination numbers, mean square displacements and the interatomic coupling constants for different pairs of atoms have been calculated from the radial distribution curves. The interatomic distances and octahedral co-ordination number is found to decrease marginally upto 640°C and thereafter decrease steadily upto 800°C. The hydroxyl water is completely expelled from the structure and the original chrysotile structure breaks down. The entire process of dehydration has been interpreted in terms of RDF data.

Dielectric Properties of a Di-trioctahedral Chlorite: Cookeite

Temperature and frequency variations of the dielectric constant (K), loss (tan δ) and conductivity of a di-trioctahedral chlorite (cookeite) were measured in the temperature range 30°—400°C and frequency range 102—107 kHz. The variational patterns of these parameters of cookeite have been compared with those of ripidolite, a tri-trioctahedral chlorite and some interesting results have been obtained. The sample was also characterized by X-ray diffraction, chemical and differential thermal analyses.