Materials Science and Nanotechnology I

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Authors: Xiao Fang Cheng, Hong Wu Feng, Yan Qin Wang
Abstract: WO3 and Fe-doped WO3 thin films were prepared on Indium-Tin Oxide (ITO) glass substrates by a dip-coating. The samples were characterized by photoelectrochemistry, scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-Vis absorption spectroscopy, respectively. The result shows that the doping of Fe influenced absorption performance, and then influenced the catalytic performance. Compared with pure WO3, Fe-doped WO3 exhibited enhanced higher photoelectrochemical(PEC) performance and photocatalytic activity. The effect of doping concentration on the photocurrent was studied. It was found that the photocurrent under visible light displayed the highest values for 2% Fe-WO3 films annealed at 400 °C. The photocatalytic activity of the Fe-doped WO3 was evaluated in the methylene blue(MB) degradation under visible light illumination. The experiments demonstrated that MB could be efficiently degraded using the doped WO3 electrode as the photoanode which showed a higher activity than pure WO3. This provides a novel method for increasing the photon electric conversion efficiency of WO3 thin film electrodes.
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Authors: Rui Huang, Jie Song, Yan Qing Guo, Chao Song, Xiang Wang
Abstract: The N-rich a-SiNx:H films were deposited on Si substrates by very high frequency plasma enhanced chemical vapor deposition technique at a low temperature of 250 °C. Strong blue photoluminescence (PL), which originates from nitrogen dangling bond, can be observed in the as-deposited samples. The dependence of defect PL on annealing temperature was systematically investigated. The PL spectra reveal that the PL peak is almost independent of the annealing temperatures while the luminescence intensity rapidly decreases with the annealing temperature increasing from 400°C to 600°C. However, higher annealing temperatures over 700 °C results in an enhancement of luminescence intensity. Based on the relationship between PL spectra and bonding configurations of the samples, the evolution of defect PL with annealing temperatures was briefly discussed.
234
Authors: Kui Huang, Jin San Chen, Yang Liu
Abstract: Marine mussels secrete remarkable mussel adhesive proteins (MAPs) for adherence to the substrates upon which they reside. Inspired by the intermolecular cross-linking characteristics of MAPs, we report the synthesis of thermosensitive dopamine modified Pluronic copolymer (PluF127-Dopa) with high coupling efficiency. Under certain temperature and concentration, PluF127-Dopa copolymers in aqueous solution self-assemble into micelles and are able to rapidly form a more stable hydrogels upon addition of oxidizing reagents such as NaIO4, resulting from oxidative cross-linking of dopamine. UV-vis spectroscopy was utilized to identify the reaction intermediates. The sol-gel transition curves of cross-linked PluF127-Dopa hydrogels (CL-PluF127-Dopa) were determined by a vial inversion method. The critical gelation concentration of CL-PluF127-Dopa hydrogels was significantly lower than those for PluF127-Dopa and unmodified Pluronic F127. The apparent mechanical strength of CL-PluF127-Dopa hydrogels was dramatically enhanced compared to those unmodified Pluronic copolymer hydrogels, suitable for sustained drug delivery. These new biomimetic materials are expected to have potential uses in biomedical applications.
238
Authors: Mazhyn Skakov, Lyaila Bayatanova, Michael Sheffler
Abstract: We investigated 18CrNi3MoA-SH steel, hardened by electrolyte-plasma processing method. Scanning analysis of transient surface demonstrated that in the course of details’ electrolyte-plasma heating chemical surface modification takes place along with tempering. Unit value of micro hardness on the crosscut is estimated. Micro hardness twofold increase concerning initial condition testifies to material hardness after electrolyte-plasma processing. This method advantages are minor energy expenditure in the time of tempering high speeds, possibility of local surface processing especially of large size details with complicated shape. 18CrNi3MoA-SH steel hardening by electrolyte-plasma method is performed on semi-industrial installation constructed at D.Serikbayev EKSTU in collaboration with «TehnoAnalyt» Ltd., Ust-Kamenogorsk. The detail heating temperature is 930 - 9400С, overall time of processing is approximately 5 minutes, hardening is produced at 860 - 8700C then cooled in electrolyte flux. Electrolyte composition is 10 %-s' Na2CO3 and C3H8O3. The metallographic analysis was realized on «NEOPHOT 21» microscope. The qualitative and quantitative phase analysis of steel structure was carried out on PANanalytical" X-Ray diffractometer involving Cu-K radiation. Microhardness determination was measured on PMT-3 device with diamond cutting point; by indentation load 1 N according to State Standard 9450-76.
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Authors: Jing Wang, Rui Wang
Abstract: A new liquid redox method for low sulfur containing gas treatment, with H2S concentration less than 1000mg/m3, was developed employing the heteropoly compounds of molybdenum and phosphorus by the present authors. The desulfurization characteristics of the absorbent system of vanadium substituted heteropoly acid, viz. H4PVMo11O40, were investigated by dynamic outlet-gas H2S concentration detection method. Like the aqueous solution of the parent compound, namely H3PMo12O40 or its sodium salt, H4PVMo11O40 solution can also be used as efficient absorbent for H2S removal. The absorbent system of H4PVMo11O40 solution was found to have fairly good absorption-regeneration performance, with a H2S removal rate of up to 100% in the presence of CuS as additive, hence it is promising in pollution control and resource reclamation.
246
Authors: Hong Quan Zhang, Ming Zhang, Lu Wei Fu, Yu Ning Cheng
Abstract: Zn or Mg ions doped hydroxyapatite (HA) particles were successfully developed by introducing various concentration of Zn or Mg in the starting solution using wet chemical precipitation method and followed a hydrothermal treatment. The products were identified as HA by XRD and FTIR, and the precipitated particles had a rod-like morphology. All the products for Mg and Zn ions concentration in the preparation solution less than 40 mol% were identified as HA. Substitution of Mg and Zn in HA crystal would impair the crystallization of HA and significantly reduce the length of a, c values of HA unit cell, which clearly demonstrated that Mg or Zn ions were structurally incorporated into the apatite crystals, they were not just absorbed on the surface of crystals.
250
Authors: Sharifah Adzila, Iis Sopyan, Siti Farius, Nurfahana Wahab, Singh Ramesh
Abstract: This work presents the wet mechanochemical synthesis of hydroxyapatite (HA) powder through two different milling mediums. The effect of milling mediums on powder properties was investigated. Two types of medium: water and ethanol were chosen with 370 rpm milling speed for 15 hours time. Characterization of synthesized powders was accomplished by X-ray diffraction (XRD) analysis. The green compacts were prepared and sintered in atmosphere condition at various temperatures ranging from 900oC - 1300oC. The mechanical and physical properties were evaluated under Vickers microhardness test and density measurement. Both of synthesis mediums yielded HA phases in the synthesized powders as detected by the peaks obtained in XRD analysis. Compacts synthesized in water medium (M1) showed a maximum density, 99% sintered at 1000oC and 1300oC. However, the hardness in water medium is closely similar to the ethanol medium as a function of sintering temperature where the maximum hardness was found in compacts synthesized in ethanol medium (M2) sintered at 1300oC (5.8GPa). The microstructure observed from SEM analysis was in line with the density obtained as the surface of sintered compacts synthesized in water medium (M1) contained less pores with large grain growth.
254
Authors: Gunawan, Iis Sopyan, S. Nurfaezah, M. ‘Ammar
Abstract: Triphasic calcium phosphate, composed of a more stable phase hydroxyapatite (HA) and highly soluble tricalcium phosphates (α- and β-TCP) has been synthesized through hydrothermal method. In the present work, an in-situ method to disperse 1wt% multiwall carbon nanotubes (MWCNTs) within HA/TCP powder has been used in order to develop HA/TCP-CNTs composite. XRD results confirmed the formation of HA, α-TCP and β-TCP in both as-prepared powder and composite samples. The graphite peaks appeared in the composite samples as well. FTIR analysis of sintered compacted powder showed the formation of weak bands of PO43- as the temperature was increased. The sintered compacts were mechanically tested by Vickers microhardness indentation method. HA/TCP-CNTs composite was found to have a significant of Vickers Hardness of 1.98 GPa after 1100°C sintering. The morphology analysis showed that in-situ deposition technique provides homogeneous dispersion of CNTs in the calcium phosphate matrix.
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Authors: Fan Jiang, Jian Hua Xiang, Zhong Wei Liang, Chun Liang Zhang
Abstract: This paper introduced Extension optimization theory into the parameters optimization of lapping process, the five process parameters of the lapping load pressure, the platen speed, the abrasive particle size, slurry flow, lapping fluid concentration are considered, the target extension decision models and integrated decision-making correlation function are established. According to the selection criteria, the optimum solution is obtained. The results showed that: as the lapping speed of 35rpm, the pressure of 11 MPa, the abrasive particle size of W7.95, the slurry flow rate of 228.75ml/min, the slurry concentration of 25%, the surface removal rate increased, the surface roughness decreases, flatness decreases.
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Authors: Xiao Qing Xu, Peng Gao, Tie Tao Zhou
Abstract: Ceramic cores are playing a more and more important role in the modern precision casting industry system; it could influence the internal structure and performance of the castings. Especially in the precision casting field, the internal structure directly influenced the ultimate properties. This paper investigated the calcium oxide ceramic cores used in titanium precision casting fields through changing the ratio of aggregate sizes and sintering process. The main properties as bend strength, sintering shrinkage, casting reaction layer and microstructure are performed using SEM, XRD and other measurement method. Results of this research showed that the calcium oxide ceramic cores could be used in titanium precision casting, provide a stable casting property and nearly without reaction pollution to the titanium castings.
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