Effect of silicon and heat-treatment temperature on the morphology and mechanical properties of silicon - substituted hydroxyapatite

The precipitation method was used to synthesize silicon-substituted hydroxyapatite with different Si contents of 0.4, 0.8 and 1.6 wt.% (0.4, 0.8 and 1.6Si-HA) using silicon acetate [Si(OCOCH₃)₄] as a Si source. As-synthesized hydroxyapatite (HA) and Si-HA powders/bulks were heat-treated at different temperatures of 1150, 1200 and 1250 °C for 1 h. Pure 0.4Si-HA and 1.6Si-HA were obtained after heat-treatment at all temperatures, whilst α-TCP phase was formed in the 0.8Si-HA sample after heat-treatment at 1250 °C. SEM observation clearly showed that the substitution of Si in HA inhibited the grain growth of Si-HA even at high heat-treatment temperatures (1200 or 1250 °C). The highest diametral tensile strength (DTS) of 15.93 MPa was obtained in the 1.6Si-HA sample after heat-treatment at 1250 °C.     

Carbothermal nitridation process of mechanically milled silica sand using Taguchi's method

This paper reported on the work performed to study the formation of silicon nitride and silicon carbide whiskers using the carbothermal nitridation process. A distinctive aspect of the present study lies in the use of the mechanical milling method to alter the regularity of the crystalline network of the silica sand. In order to optimise the processing parameters for the synthesis of silicon carbide, the concept of Taguchi's Design of Experiments was considered, the analysis being based on Taguchi's signal to noise ratio and variance techniques to obtain optimum combination of process parameters. Important factors influencing the formation of silicon carbide were the duration of the mechanical milling, followed by temperature, time and heating rate.     

A Multi-objective Optimization for Sizing and Placement of Voltage-controlled Distributed Generation Using Supervised Big Bang–Big Crunch Method

Abstract—This article presents an efficient multi-objective optimization approach based on the supervised big bang–big crunch method for optimal planning of dispatchable distributed generator. The proposed approach aims to enhance the system performance indices by optimal sizing and placement of distributed generators connected to balanced/unbalanced distribution networks. The distributed generation units in the proposed algorithms are modeled as a voltage-controlled node with the flexibility to be converted to a constant power node in the case of reactive power limit violation. The proposed algorithm is implemented in the MATLAB (The MathWorks, Natick, Massachusetts, USA) environment, and the simulation studies are performed on IEEE 69-bus and IEEE 123-node distribution test systems. Validation of the proposed method is done by comparing the results with published results obtained from other competing methods, and the consequent discussions prove the effectiveness of the proposed approach.     

Investigation on the effect of spinning conditions on the properties of hollow fiber membrane for hemodialysis application

Polyethersulfone (PES) hollow fiber membranes were fabricated via the dry‐wet phase inversion spinning technique, aiming to produce an asymmetric, micro porous ultrafiltration hollow‐fiber specifically for hemodialysis membrane. The objective of this study is to investigate the effect of spinning conditions on the morphological and permeation properties of the fabricated membrane. Among the parameters that were studied in this work are air gap distance, dope extrusion rate, bore fluid flow rate, and the take‐up speed. The contact angle was measured to determine the hydrophilicity of the fibers. Membrane with sufficient hydrophilicity properties is desired for hemodialysis application to avoid fouling and increase its biocompatibility. The influences of the hollow fiber's morphology (i.e., diameter and wall thickness) on the performance of the membranes were evaluated by pure water flux and BSA rejection. The experimental results showed that the dope extrusion rate to bore fluid flow rate ratio should be maintained at 1:1 ratio to produce a perfectly rounded asymmetric hollow fiber membrane. Moreover, the flux of the hollow fiber spun at higher air gap distance had better flux than the one spun at lower air gap distance. Furthermore, spinning asymmetric hollow fiber membranes at high air gap distance helps to produce a thin and porous skin layer, leading to a better flux but a relatively low percentage of rejection for BSA separation. Findings from this study would serve as primary data which will be a useful guide for fabricating a high performance hemodialysis hollow fiber membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43633.     

Synthesis of Co3O4 @ Organo/Polymeric Bentonite Structures as Environmental Photocatalysts and Antibacterial Agents for Enhanced Removal of Methyl Parathion and Pathogenic Bacteria

Two green nanocomposites of Co₃O₄ decorated CTAB/bentonite (Co@CT/BE) and chitosan/bentonite (Co@CH/BE) were synthesized as enhanced and environmental photocatalysts and antibacterial agents. As photocatalysts, the products were applied in the effective oxidation of toxic methyl parathion pesticide (MP) in wastewater under a visible light source. The application of Co@CH/BE (0.02 g) resulted in the complete oxidation of MP (50 mg/L) after 40 min and complete mineralization after 60 min. while the complete oxidation and mineralization of MP (50 mg/L) by Co@CT/BE was recognized after 75 min and 100 min, respectively. The Co@CH/BE composite is of higher activity than Co@CT/BE and can cause complete oxidation for MP at high concentrations up to 100 mg/L after 75 min. The oxidation pathway was illustrated considering the existence of the hydroxyl radicals as the active oxidizing species and the identified secondary organic compounds during the oxidation tests. The detected intermediate converted into end products of CO₂ and inorganic anions of SO₄^?2, NO₃^?, and PO₄^?3 at the final stages of the oxidation processes. As antibacterial agents, the two composites exhibit considerable inhabitation zones of about 20 mm against both the Gram-positive Staphylococcus aureus and Gram-negative bacterium Vibrio Sp. The synthetic Co@CH/BE showed the best antibacterial properties with 200 μg/mL as minimum inhibitory against Staphylococcus aureus.

     

Structural Control of NiO–YSZ/LSCF–YSZ Dual‐Layer Hollow Fiber Membrane for Potential Syngas Production

The objective of this study was to fabricate dual‐layer hollow fiber as a microreactor for potential syngas production via phase inversion‐based co‐extrusion/cosintering process. As the main challenge of phase inversion is the difficulty to obtain defect‐free fiber, this work focuses on the effect of the fabrication parameters, that is, nonsolvent content, sintering temperature and outer‐layer extrusion rate, on the macrostructure of the produced hollow fiber. SEM images confirm that the addition of nonsolvent has successfully minimized the finger‐like formation. At high sintering temperature, more dense hollow fiber was formed while outer‐layer extrusion rate affects the outer layer thickness.     

Correction to: Synthesis of Co3O4 @ Organo/Polymeric Bentonite Structures as Environmental Photocatalysts and Antibacterial Agents for Enhanced Removal of Methyl Parathion and Pathogenic Bacteria

Journal of Inorganic and Organometallic Polymers and Materials -     

Resolution of a Five-Component Mixture of Quaternary Ammonium Surfactants on Silica Gel 60 <Emphasis Type="Italic">F</Emphasis><Subscript>254</Subscript> High Performance Thin Layer Chromatographic Plates

The mutual separation of a mixture of cetyltrimethyl ammonium chloride (CTAC), methyl trioctyl ammonium bromide (MTOB), dodecyltrimethyl ammonium chloride (DTAC), benzyltrimethyl ammonium chloride (BTAC) and tetrabutyl ammonium bromide (TBAB), was achieved on silica high performance thin layer chromatographic plates using dimethyl sulfoxide with aqueous sodium-l-tartrate dibasic dihydrate as the solvent system. The effect of concentration of sodium-l-tartrate dibasic dihydrate on the mobility of all the five quaternaries was examined. The limit of detection of CTAC, MTOB, DTAC, BTAC and TBAB was estimated as 0.6, 0.6, 0.3, 0.6 and 0.3 μg/zone, respectively. The method developed was utilized to identify these surfactants in different spiked water samples after their preliminary separation.     

Estimation of optimum binder content of recycled asphalt incorporating a wax warm additive using response surface method

This paper presents a new approach to estimate the optimum binder content (OBC) of recycled asphalts (RAs) incorporating a warm mix additive based on the interaction effects of compaction temperature, RA content and binder content using volumetric and strength characterisation. The experimental design was developed using response surface method (RSM) based on central composite design for various compaction temperatures (130–160 °C), RA contents (30–50%) and binder contents (4.9–6.0%). Laboratory tests were performed and analysed to meet the desired volumetric and strength properties according to the Malaysian specifications for the design of dense asphalt mixtures. Statistical analysis and mathematical models proposed by RSM were used to determine the OBC. The results showed that compaction temperature is the most significant factor in determining the OBC. There are minimum differences in the OBC variation of samples incorporating different dosage of RA. The developed model can be used for quick estimation of OBC for various levels of compaction temperature and RA content.