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Authors: Han Zhou, Tong Xiang Fan, Di Zhang
Abstract: Bacterium have evolved a large variety of stunning morphologies controlled at the microor even nanoscopic level such as cocci, bacillus, vibrios and spirillum acting as templates can lead to the formation of corresponding hollow inorganic replicas. Here, cocci Streptococcus thermophilus has been used as a natural biotemplate to synthesize ZnO hollow spheres via a simple hydrothermal method, followed by calcination. The as-obtained products are characterized by techniques of TG, XRD, FESEM, TEM and N2 adsorption. A possible formation mechanism is proposed which has an effect on the bimodal pore structure of the products with pores in the mesoporous range. It has introduced a new concept to synthesize porous hollow spheres by using bacteria as a biotemplate and has opened up a new pathway to synthesize hollow nanospheres, nanotubes and other kinds of 3D hollow nanostructures with bacteria of different morphologies, dimensionalities and sizes as templates.
Authors: Qun Dong, Hui Lan Su, Di Zhang, Wei Cao, Jie Han
Abstract: Biogenic technique for the synthesis of composites with nanopatterns is evolving into an important branch of nanobiotechnology and materials science. In this work, the biomaterials eggshell membrane fibers (ESMF) and silk fibroin fibers (SFF) were infused into palladium chloride and silver nitrate solution at room temperature to actualize the extracellular nucleation of noble metal nanocrystallites and in situ assembly into composites with hierarchical nanostructures on the biofibers. The present biofibers not only served as the reacting substrates but also functioned as the surfactants, so that small-sized but well-crystallized nanocrystallites could be organized into subtle hierarchy to form inorganic-organic nanocomposites under the direction of the biomacromolecules.
Authors: Harun Mindivan, S. Kayali, Huseyin Cimenoglu
Abstract: This study has been conducted to investigate the mechanical properties of aluminum matrix 50 vol.% SiC particle (SiCp) reinforced composites produced by a squeeze casting technique. Commercial 2618, 6082, and 7012 aluminum alloys were utilized as the matrix material. Composites were tested in as-cast and T6-tempered states. Mechanical properties of the composites were determined by hardness measurements and impact tests. As-cast composites exhibited lower hardness along with a better impact resistance than their T6-tempered states. After T6-tempering the hardness of 7012 matrix composite reached to a value of 324 HV2, which is comparable with the hardness of quenched and tempered steels.
Authors: W.Q. Song, Syed H. Masood
Abstract: This paper introduces an entirely new metal based composite material for direct rapid tooling application using Fused Deposition Modelling rapid prototyping system with desired mechanical and thermal properties and characteristics. The paper specifically describes the results of the dynamic mechanical thermal analysis (DMTA) of this new metal/polymer composite material, consisting of iron particles in nylon type matrix, for use in FDM process and with the aim of application to direct rapid tooling for injection moulding. The work represents a major development in the direction of direct rapid tooling for reducing the cost and time in tooling manufacture for injection moulding.
Authors: A.A. Shaikh, S.A. Channiwala
Abstract: The composites are very useful in present era due to weight saving and economy of construction by tailoring material to structural application. In order to save the crop from extinction and to ensure a reasonable return to the farmers, non-traditional outlets have to be explored for the jute fiber. Jute fiber due to its adequate tensile strength and good specific modulus enjoys the right potential for usage in composites. In the present work the experimentations were conducted for the strength of composite by varying volume fraction of fiber in the range of 12 % to 42 %. The tensile strengths of specimen were measured as per ASTM D 3039-76, and the amount of voids fraction is measured to evaluate actual contributing volume fraction of fiber and volume fraction of matrix. The prediction of strength is proposed by considering efficiency terms f η and m η representing effective contribution of fiber and matrix and an additional efficiencies t1 η and t 2 η representing effectiveness from fiber and matrix for transverse reinforcement case. The results are also compared with FEM results obtained using standard package ANSYS and IDEAS. The results obtained by experiments are observed to be within 0.9 % with developed model and 2.85 % and 3.21 % with ANSYS and IDEAS simulated results. The deviation of proposed model is observed under predictive for experimental data available in literature while the experimental results obtained in present work is also found to be on lower side to that of available predictive models from literature.
Authors: L.G. Guo, He Yang
Abstract: During cold ring rolling process, the accurate prediction and analysis of force and power parameters, including roll force (RF) and roll moment (RM), is important in selecting, designing and developing the forming rolls and cold ring rolling mills. In this paper, a three-dimensional elastic-plastic dynamic explicit FE model of cold ring rolling process has been presented and validated in terms of roll force and geometry development. Based on the model, the variation laws of force and power parameters under different sizes of forming rolls (including driver roll and idle roll) and forming parameters (including the rotational speed of driver roll 1 n and the feed rate of idle roll v ) have been revealed by comprehensive numerical simulations.
Authors: Feng Wang, Bai Qing Xiong, Yon Gan Zhang, Bao Hong Zhu, Hong Wei Liu, Xu Jun Mi, Xiao Qing He
Abstract: In this paper, Al-10.8Zn-2.8Mg-1.9Cu alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray deposited alloy at various aging conditions (T6, T73 and RRA treatment) were studied using high-resolution electron microscopy, selected area diffraction, and tensile tests. The results indicate that the two types of GP zones, GPI and GPII zones are major precipitates for the alloy under peak-aged condition. The peak UTS and YS values achieved at an ageing temperature of 120 °C was 818 MPa and 793 MPa. Under two-step aging condition, the GP zones and η’ are major precipitates for the alloy, the discontinuous grain boundary precipitates are favorable to SCC resistance in over-aged condition, which reduces its strength 58 MPa(about 7%) comparing to the peak-aged condition. RRA treatment decreased ultimate tensile strength 25 MPa (about 3%) in values compared with the alloy at T6 condition.
Authors: Ivan Saxl, Vàclav Sklenička, L. Ilucová, Milan Svoboda, Petr Král
Abstract: The effect of ECAP technology on the subgrain structure of coarse-grained pure aluminium is described by means of the orientation imaging microscopy (the selected lower bounds of misorientation (disclination) are  = 2o, 5o, 10o and 15o). Standard profile and intercept counts carried out in three suitably oriented and mutually perpendicular section planes and along 18 systematically oriented directions, resp., are used to examine the subgrain and grain structures after the number of passes N = 2, 4, 8, 12 as well the effect of subsequent annealing (several hours at 473K). The local and overall non-homogeneity and anisotropy of boundary structures have also been evaluated.
Authors: B.Y. Stevinson, D.L. Bourell, J.J. Beaman
Abstract: Silicon infiltrated silicon carbide parts have been manufactured using selective laser sintering (SLS). The processing route has been defined, including post-processing steps: formation of a green part from silicon carbide powder using a phenolic binder, infiltration with a transient epoxy binder, dissociation of the binders thermally to create a brown part, heating the brown part to the infiltration temperature and infiltrating with molten silicon. A dimensional analysis study was performed. Cubes 25.4 mm on each side were selective laser sintered and measured after each processing step. The largest dilatation (volume strain), 7.3%, was associated with creation of the green part relative to the computer solid model. The smallest dilatation, -6%, was associated with binder dissociation shrinkage. These volume strains nominally offset, resulting in creation of nonmetallic parts with small dimensional errors relative to the computer solid model. This research was funded by the National Science Foundation under grant award DMI-0522176.
Authors: Khershed P. Cooper
Abstract: New manufacturing methods involving direct fabrication processes seem ideal for mass customization or “just-in-time” production. The use of tool-less means of production ensures reduced lead-time and lower cost. Besides, they provide flexibility in design and fabrication, which are essential for small lot sizes. However, part quality and production reliability are challenges that must be met. When adapted to the micro-factory paradigm, direct manufacturing can be made portable and capable of remote manufacturing. The benefits of miniaturization are savings in materials and energy consumption, but the increased surface area to volume ratio has implications for material behavior, especially mechanical strength. The newest incarnation of direct manufacturing is direct digital manufacturing or DDM, which involves localized deposition of material or energy and the creation of heterogeneous objects with digital means of control. DDM seeks spatial control of macrostructure, composition, texture and properties with the possibility of producing materials with unusual behavior, functionally gradient structures and integrated component devices. For DDM, multi-material design, precision in deposition, shaping and removal and understanding of heterogeneous material behavior are challenges.

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