Crystallite

We investigate the characteristics of polycrystalline Silicon (poly-Si) thin films for solar cells produced by very high frequency (VHF) plasma enhanced chemical vapor deposition using a conductive scanning probe microscope (SPM). We measure the surface morphology and local current images are simultaneously of the poly-Si layers with a thickness, d=2 mm, formed on textured Ag/SnO2/glass in the range of RMS based-textured substrate (a) s=85nm, (b) s=42nm and (c) s=2nm respectively. Influences of the substrate texture on the crystal growth as well as the local current flow are discussed. Where we found that the average of local current proportional with crystallinity, where the poly-Si layer that has rich crystallinity indicated low conductivity that yield high local current.

Synthesis, optical, mechanical, and structural characterization of organic–inorganic nanocomposite thin films based on polyethylene oxide and poly(vinyl alcohol) (PVA) polymers incorporated with (1:0), (0.75:0.25), (0.5:0.5), (0.25:0.75), and (0:1) content percentage ratios of ZnO-NPs: Al2O3-NPs nanoparticles are reported. The optical properties, including the absorption coefficient, refractive index, extinction coefficient, dielectric function, and optical band gap for the films, are investigated from the measured transmittance and reflectance using a newly derived mathematical model. The as-grown PVA-PEO polymeric thin films exhibit transmittance of 87% while it decreases down to 75% with ZnO-NPs and decreases in between by the addition of Al2O3-NPs. However, the refractive index increases from 2.0 with ZnO-NPs to 2.7 with Al2O3-NPs. The band gap energy is from 3.98 to 3.89 eV accordingly. The dislocation density,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$,$$\end{document} crystallite size, and average internal strain obtained from the X-ray diffraction patterns exhibit abnormal behavior for equal ratio (0.5:0.5) of the two types of NPs compared with other ratios. Fourier transform infrared (FTIR) spectroscopy measurements to elucidate the major vibrational modes and bonding in the nanocomposite thin films. A redshift of the major peaks has been observed for all investigated compositional ratios indicating a shift of the absorption edge confirming the band gap reduction. The SEM micrographs show a clear form of nanocomposites with PVA-PEO/ZnO-NPs compared to those when Al2O3-NPs or a combination of the two kinds of NPs are introduced to the complex matrix. Our detailed analysis of the physical properties of PVA-PEO/ZnO-Al2O3 indicates their potential to be candidate materials for modern optical and optoelectronic devices.

Glycine-Montmorillonite (Gly-MMT) composite has been synthesized through intercalation process using Na-Montmorillonite (Na- MMT) and glycine ethylester hydrochloride. Gly-MMT was employed for the synthesis of dipeptide (Gly-Gly-MMT). Microstructural parameters such as crystallite size, r.m.s. strain (<e2>1/2) and layer disorder parameters such as variation of interlayer spacing (g) and proportion of planes affected by such defects (?) of the samples have been calculated by X-ray line profile analysis. In comparison to Na-MMT the basal spacings (d001) of Gly-MMT and Gly-Gly-MMT were reduced by 2.4Å and 1.8Å respectively. The value of d001 of Gly-Gly-MMT (13.3 Å) suggests the monolayer orientation of dipeptide into interlayer spaces. It is also suggested that more homogeneity in the stacking of silicate layers is attained in Gly-Gly-MMT due to the increased chain length of the dipeptide and orientation in monolayer style.DOI: http://dx.doi.org/10.3329/dujs.v60i1.10331Dhaka Univ...

Abstract: In this work, untreated bovine cortical bones (BCBs) were exposed to a range of heat treatments in order to determine at which temperature the apatite develops an optimum morphology comprising porous nano hydroxyapatite (nanoHAp) crystals. Rectangular specimens (10 mm × 10 mm × 3–5 mm) of BCB were prepared, being excised in normal to longitudinal and transverse directions. Specimens were sintered at up to 900 °C under ambient pressure in order to produce apatites by two steps sintering. The samples were characterized by thermogravimetric analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) attached to an energy-dispersive X-ray spectroscopy detector. For the first time, morphology of the HAp particles was predicted by XRD, and it was verified by SEM. The results show that an equiaxed polycrystalline HAp particle with uniform porosity was produced at 900 °C. It indicates that a porous nanoHAp achieved by sintering at 900 °C can be an ideal candidate as ...