Key Engineering Materials Vol. 521

Abstract: This article describes the in-situ synthesis and immobilization of iron nanoparticles on several substrates at room temperature using NaBH₄ as a reducing agent and ascorbic acid as capping agent. The method is very effective in protecting iron nanoparticles from air oxidation for more than 30 days. Substrates used to immobilize iron nanoparticles are spherical polymer resins (size of 100–200 mesh) and novel carbon substrates prepared from high temperature carbonization of e-spun nylon and polyacrylonitrile fabrics. Iron nanoparticles (40–100nm) immobilized sample showed higher activity for the reductive removal of hazardous hexavalent Cr (VI) compared to free floating iron nanoparticles at ambient temperature. Iron immobilized substrates has a great potential to be used not only for the removal of Cr (VI) in waste stream but also for oxygen scavenger for food packaging.

Abstract: We report an eco-friendly synthesis of well–controlled, nano-to-micron-size, spherical SiO₂ particles using non-hazardous solvent and a byproducts-producing system. It was found that the morphology and size of spherical SiO₂ particles are controlled by adjusting the concentration of PEG and oleylamine, ethanol solvent selection, and reaction temperature. The SEM images show spherical-shaped silica particles with homogeneous particle-size distribution. Structural and optical properties of the silica particles were investigated by FT-IR absorption spectroscopy and photoluminescence. The resultant SiO₂ particles from the synthesis system were easily dispersed in both water and organic solvent.

Abstract: A green process to prepare the hydrophobic and transparent CNT-based surface was developed without using any toxic chemicals, solvents or gases. CNT brush (CNT-b) powder, which was prepared by the repeated CVD, was the main material to prepare the desired surface. An adhesive layer of ethyl cellulose (EC) was spin coated on the glass substrate, where EC formed a networked porous microstructure. A low concentration CNT-b suspension was obtained by sonication of the mixture of CNT-b powders, sodium dodecylbenzenesulfonate (SDBS) and deionized water. To obtain the stabilized CNT-b suspension, it was found that 40 min of sonication time and SDBS/CNT-b weight ratio being 0.1 were required. The target surface was then prepared by spin coating CNT-b suspension on the EC coated glass. The contact angle of the prepared surface was around 120o and the optical transmittance was around 93% for the visible light. Either increasing the number of spin coatings or increasing the concentration of CNT-b suspension could slightly increase the contact angle to around 130o but the optical transmittance significantly reduce to about 75%, leading to a semi-transparent sample.

Abstract: With wood being a versatile material, man has made several innovations from time to time, for maximum utilization of the same, singly or jointly with other materials. Such innovation has been a continuous process along with advances in other fields of material science and engineering. Earlier information is reviewed and updates are discussed.

Abstract: Waste materials can have negative environmental impact and cost implications associated with their safe disposal given the increasing awareness and stringent environmental standards. Several options for utilization of waste have been explored in the lab scale and pilot scale. In this article high value materials obtained from waste are reviewed. This includes industrial waste, food industry waste and combustion residues, to obtain transition metal based catalysts, biomaterials and zeolites respectively. The different approaches to the processing and the properties of the product are discussed.

Abstract: Silver containing diamond like carbon films were coated on the surface of polyethylene film (PET) using novel hybrid sputtering method. Polymeric substrates can create soft, flexible, highly absorbent and cost-effective materials by selecting or controlling their molecular structures. The material silver is known to be a potential antibacterial material. The silver containing coating has been potentially recommended for synthesis biomedical materials. In the present work, we discussed the antibacterial activity of the silver containing DLC film coated PET film surfaces which was coated as a function of deposition power level. The surface morphology of the Ag-DLC was analysed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The atomic concentration and structure of the Ag-DLC was measured by energy dispersive X-ray (EDX) and Raman spectroscopy. The hydrophilicity of the films was measured by contact angle analysis. The antibacterial activity of Ag–DLC films were evaluated by bacterial eradication tests with Escherichia coli at incubation time of one day. In addition, blood compatibility of the Ag-DLC films were studied by In Vitro blood compatibility tests. It was found that the surface of the obtained Ag-DLC decreases with increasing the deposition power level. The antibacterial and hemocompatibility of the silver containing DLC film increase gradually with increase of deposition power level. Our results revealed that the Ag-incorporated DLC films are potentially useful as biomedical devices having good antibacterial and hemocompatibility.

Abstract: From the history of commercial anode materials, Sn/C-based material is the focus to enhance the cycling performance. A chemical solution method is used to synthesize the Sn compounds / graphite composite anodes. At the first part of this study, the cycle life was enhanced by adjusting various pH values. The multi-phase Sn compound containing Sn₆O₄(OH)₄, SnO₂, Sn₃(PO₄)₂ were deposited on slices of graphite of sample pH6. They were expected to provide a higher spectator to Sn ratio for improved cycleability. These phases could be reduced to metallic Sn, resulting in buffer matrix during 1^st cycle. Therefore, the sample pH6 exhibited the best of electrochemical performance. For the cell cycled between 0.001V and 1.5V, the 1^st charge capacity was 758 mAhg-1. Even after 50 cycles, the capacity remained higher than 460 mAhg-¹. Synthesizing Sn compounds / graphite composite anodes at pH6 with different initial Sn concentrations improved the cycling performance in the second part of this study. When the Sn concentration reached 0.12M, multi-phases of Sn compounds were deposited on the slices of graphite and the amount of Sn was the maximum. The agglomeration of Sn clusters was suppressed by buffering agent generated by the multi-phase of Sn compounds containing Sn₆O₄(OH)₄, SnO₂, Sn₃(PO₄)2_{. Therefore, the sample Sn0.12 M exhibited}the best cycling behavior among all. During cycling between 0.001 V and 1.5 V, the 1^st charge capacity was around 734 mAhg^-1. The capacity remained as high as 440 mAhg-1 even after 50 cycles.

Abstract: This chapter covers the series of machinability evaluation test result and discussions of Zr_52.5Ti₅Cu_17.9Ni_14.6Al₁₀ bulk metallic glass (BMG). These tests are lathe turning, drilling, milling and preliminary level grinding tests. In the continuous machining methods such as turning, drilling and grinding of BMG, above a threshold cutting speed, the low thermal conductivity of BMG leads to chip temperatures high enough to cause the chip oxidation and associated light emission. The high temperature produced by this exothermic chemical reaction causes crystallization within the chips. Chips morphology suggests that increasing amounts of viscous flow control the chip-removal process. Moreover, viscous flow and crystallization can occur during the machining of the bulk metallic glass, even under the high temperature gradient and strain rate. High cutting speed significantly reduced the forces for BMG machining due to thermal softening. However, in intermittent cutting process which is milling, there is no high temperature problem, special burr formations the rollover and the top burr were observed along the slot and achieved good surface roughness, R_a = 0.113 μm, using conventional WC-Co cutting tool. In each method, tests repeated for the conventional materials for comparison purpose. This study concludes the precision machining of BMG is possible with the selection of feasible tools and process parameters for each method.

Abstract: This overview highlights very recent application of electron backscatter diffraction (EBSD) to shape memory alloys, as main investigation technique but also as ancillary technique for other characterization methods. Over the last two decades EBSD in the scanning electron microscope has become a powerful tool for the characterization of many materials and transformation. In the mean time, shape memory alloys (SMA) are continuously studied: from a theoretical point of view, in order to clarify unsolved fundamentals of their phase transformations and characterize or develop new SMA systems, and from an engineering point of view, to solve design and processing problems related to the continuously growing examples of applications. Application of EBSD to SMA, even if hindered by limitations generally found also in other metallic system when phase transformation and martensitic phases are involved, provided useful information for both research areas.