Accelerated thermal cycling test of microencapsulated paraffin wax/polyaniline made by simple preparation method for solar thermal energy storage

Microencapsulated paraffin wax/polyaniline was prepared using a simple in situ polymerization technique, and its performance characteristics were investigated. Weight losses of samples were determined by Thermal Gravimetry Analysis (TGA). The microencapsulated samples with 23% and 49% paraffin showed less decomposition after 330 °C than with higher percentage of paraffin. These samples were then subjected to a thermal cycling test. Thermal properties of microencapsulated paraffin wax were evaluated by Differential Scanning Calorimeter (DSC). Structure stability and compatibility of core and coating materials were also tested by Fourier transform infrared spectrophotometer (FTIR), and the surface morphology of the samples are shown by Field Emission Scanning Electron Microscopy (FESEM). It has been found that the microencapsulated paraffin waxes show little change in the latent heat of fusion and melting temperature after one thousand thermal recycles. Besides, the chemical characteristics and structural profile remained constant after one thousand thermal cycling tests. Therefore, microencapsulated paraffin wax/polyaniline is a stable material that can be used for thermal energy storage systems.Mahyar Silakhori, Mohammad Sajad Naghavi, Hendrik Simon Cornelis Metselaar, Teuku Meurah Indra Mahlia, Hadi Fauzi, and Mohammad Mehral

Adsorption capability of heavy metals by chitosan/poly(ethylene oxide)/activated carbon electrospun nanofibrous membrane

In this study, activated carbon (AC) was synthesized by chemical activation process from rice husk, with the BET surface area of 2180 m2/g. Chitosan/poly(ethylene oxide) (PEO)/AC nanofibrous membrane (CPANM) was synthesized by electrospinning process. The average fiber diameter was found to be 83 ± 12.5 nm. Incorporation of AC lead to increase in the surface area of CPANM than chitosan/PEO fiber (CPF) by 371 m2/g. X‐ray photoelectron spectroscopy survey and narrow scan analysis further proved the presence of AC in the membrane. CPANM showed higher adsorption capability than CPF. Analysis of the mechanism of heavy metals adsorption by CPANM and CPF hypothesized that, (NH2) is the only active group in CPF, whereas both (NH2) and (COOH) contributed in adsorption for CPANM. Maximum adsorption capacity of CPANM for Cr(VI), Fe(III), Cu(II), Zn(II), and Pb(II) ion was found to be 261.1, 217.4, 195.3, 186.2, and 176.9 mg g−1 respectively

Incorporation of Human-Platelet-Derived Growth Factor-BB Encapsulated Poly(lactic-co-glycolic acid) Microspheres into 3D CORAGRAF Enhances Osteogenic Differentiation of Mesenchymal Stromal Cells

Tissue engineering aims to generate or facilitate regrowth or healing of damaged tissues by applying a combination of biomaterials, cells, and bioactive signaling molecules. In this regard, growth factors clearly play important roles in regulating cellular fate. However, uncontrolled release of growth factors has been demonstrated to produce severe side effects on the surrounding tissues. In this study, poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) incorporated three-dimensional (3D) CORAGRAF scaffolds were engineered to achieve controlled release of platelet-derived growth factor-BB (PDGF-BB) for the differentiation of stem cells within the 3D polymer network. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and microtomography were applied to characterize the fabricated scaffolds. In vitro study revealed that the CORAGRAF-PLGA-PDGF-BB scaffold system enhanced the release of PDGF-BB for the regulation of cell behavior. Stromal cell attachment, viability, release of osteogenic differentiation markers such as osteocalcin, and upregulation of osteogenic gene expression exhibited positive response. Overall, the developed scaffold system was noted to support rapid cell expansion and differentiation of stromal cells into osteogenic cells in vitro for bone tissue engineering applications

An experimental and numerical investigation of heat transfer enhancement for graphene nanoplatelets nanofluids in turbulent flow conditions

In this paper, both experimental and numerical studies have been performed on the turbulent heat transfer of the graphene nanoplatelets nanofluids in a horizontal stainless steel tube that was subjected to a uniform heat flux at its outer surface. An experimental investigation was done to evaluate the heat transfer characteristics and the pressure drop of a graphene nanoplatelet (GNP) nanofluid and in numerical study, the finite volume method with standard k-epsilon turbulence model is employed to solve the continuity, momentum, energy and turbulence equations in three dimensional domains. The thermal conductivity and viscosity of the GNP nanofluids at concentrations of 0.025, 0.05, 0.075, and 0.1 wt were measured prior to the heat transfer experiments. The heat transfer and the pressure drop within the flowing base fluid (distilled water) were measured and compared with the corresponding data from the correlations and numerical study. The data were satisfied within a 5 error and 2 error for the numerical work. The effects of the nanoparticle concentration and the heat flux on the enhancement of the heat transfer turbulent flow condition are presented. The Nusselt number (Nu) of the GNP nanofluid was higher than the base fluid by approximately 3-83 and increased as the flow rate and the heat flux increased. However, the increase in the pressure drop ranged from 0.4 to 14.6. Finally, the results reveals that the GNP nanofluids could function as a good and alternative conventional working fluid in heat transfer applications. (C) 2014 Elsevier Ltd. All rights reserved