This study investigates the mechanical reinforcement of chitosan with TiO2 and Ag nanoparticles, as well as their water vapour transmission rates and water resistance behaviour. The mechanical properties of chitosan were improved by addition of TiO2 or Ag, with significant increases in Young’s modulus (from 25 MPa to ~300 MPa), tensile strength (from 6 MPa to 18–35 MPa) and toughness (from 1.3 J g−1 to 7–8 J g−1). The water vapour transmission rates (368–413 g m−2 d−1) were found to be similar for both materials. Inclusion of Ag reduced the water resistance (from 823% to 1,000%), while inclusion of TiO2 yielded significant improvement in water resistance (from 823% to 100%)
Development of rare earth doped silica fibre fabrication using MCVD furnace chelate vapor phase delivery is presented. In this study, erbium and aluminium is used as the dopant with precursor erbium (III) tris (2,2,6,6-tetramethyl-3,5-heptanedionate) and aluminium chloride respectively. The preform was designed for 10 layers of SiO2-P2O3doped silica (clad structure) and 5 layers of SiO2-Al2O3-Er2O3(core structure). Preform is analysed for the properties of layer structure i.e. refractive index profile using preform index profiler and EPMA (SEM-EDX) for dopant distribution. Results show good longitudinal uniformity despite condensation of metal organic precursor during the fabrication process. Maximum incorporation of Er2O3is about 0.1 mole % with 1.5 mole% of Al2O3in the core.
Solar assisted heat pump (SAHP) system integrates a solar thermal energy source with a heat pump. This technique is a very fundamental concept, especially for drying applications. By combining a solar thermal energy source such as solar thermal collectors and a heat pump dryer will assist in reducing the operation cost of drying and producing products with high quality. Many review papers in the literature evaluated the R&D aspects of solar-assisted heat pump dryers (SAHPD). This critical review paper studies some of the researches conducted in this field to understand and provides an update on recent developments in SAHPD. Also, a detailed explanation of principles and operation for SAHPD and its applications are presented. The used types of solar thermal collectors, as well as various heat pump dryers, are all discussed in this article. Finally, it is concluded that there is a clear lack of research in the techno-economic and environmental evaluation, while most of SAHPD studies focused on the performance study of the system. Keywords heat pump, collector, two phases, refrigerant, compression index. Nomenclature Volumetric efficiency Mass flow rate Mass refrigerant flow Ts Wetted surface temperature P Pressure Uwi Combined coefficient of heat transfer for tube wall, refrigerant and water film V Velocity k Compression index absolute humidity ratio
This work is part of a study of solution doping in Modified Chemical Vapor Deposition (MCVD) used for silica optical fiber fabrication. This paper will concentrate on soot characterstics and the effect of different aluminum solution concentration. The effect of three different concentration of aluminum (0.3M,0.7M and 1.2M) with heat treatment are studied while the other parameters of MCVD and solution doping are fixed such as deposition temperature, SiCl4 flow, and soaking time. The porous core layer is deposited at 1800°C and the porosity of the deposited porous layer is analyzed using gas adsorption method. Refractive index profile of the doped preform is measured using preform analyzer. The aluminum distribution across the sintered glass layer is also examined by EDX.
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