Microstructures and properties of nickel-titanium carbide composites fabricated by laser cladding

In this work, Ni/TiC composites were synthesized by the laser cladding technique (LCT). A scanning electron microscope (SEM), X-ray diffractometer (XRD), microhardness meter, electrochemical workstation, and friction and wear tester examined the microstructure, surface morphology, phase structure, microhardness, wear, and corrosion resistances of the Ni/TiC composites. These results indicated the Ni/40TiC composite contained finer equiaxed crystals than the Ni and Ni/20TiC composites. In addition, numerous TiC particles in the Ni/40TiC composite impeded growth of the nickel crystals, which resulted in the fine microstructure of the Ni/40TiC composite. The Ni, Ni/20TiC, and Ni/40TiC composites exhibited face-centered cubic (f c c) lattices. The average microhardness values of the Ni/20TiC and Ni/40TiC composites were approximately 748 HV and 851 HV, respectively. The Ni/40TiC composite had the lowest friction coefficient (0.43) among all three coatings, and only some shallow scratches appeared on the surface of the Ni/40TiC composite. The corrosion potential (E) of Ni/40TiC exceeded the Ni/20TiC composite, and both were larger than the Ni composite, which indicated the Ni/40TiC composite had outstanding corrosion resistance and the Ni composite had poor corrosion resistance. The corrosion current densities (i) of Ni, Ni/20TiC, and Ni/40TiC composites were 5.912, 4.405, and 3.248 μA/cm², respectively.     

"毛虫"建筑--一次装配建筑的实验

文章详细介绍了瑞士霍夫·威施巴德餐厅因苛刻的条件而采用的特殊的设计建造的方法和过程——在基地外的一次预制装配的预演实验,同时也分析了该项目在设计上由于考虑适合装配生产特点而形成的空间效果。     

离子注入浅结制备技术

根据近年来的文献资料总结报道几种离子注入浅结制备技术，即：大角度偏转注入、分子离子注入、双离子注入，通过介质掩膜注入，注入固体源驱入扩散再分布、等离子体浸没离子注入（ＰＩＩＩ）和反冲离子注入等。     

同步辐射X射线光刻掩模镀金工艺的研究

介绍了利用北京正负对撞机(BEPC)同步辐射X射线光刻装置,进行LIGA工艺技术深结构光刻实验研究,详细论述了X射线光刻使用的掩模制备过程及掩模镀金工艺,在国内最早曝光出直径为400μm、厚为27～45μm的三维立体齿轮胶图形。     

超细晶超高碳钢研究现状及展望

超细晶超高碳钢是国外近年来发展起来的一类新型的、并具有重要发展前景的高性能钢铁材料.在系统总结大量文献资料的基础上,综述国内外近年来超细晶超高碳钢的研究进展,包括制备工艺,微观组织及其影响因素,室温力学性能,超塑性,层状超高碳钢复合材料等,指出今后超细晶超高碳钢研究的发展方向.     

Fabrication uncertainties and yield optimization in MEMS tunable capacitors

Intrinsic uncertainties of MEMS fabrication processes can severely affect the performance of devices because the tolerance ranges of these processes are relatively large and improvement of process accuracy is very expensive. Therefore, the analysis of fabrication uncertainties and their outcome on a device performance is a vital task before finalizing the design. In this paper, the effects of process inaccuracy on the performance of MEMS tunable capacitors are studied. Design parameters such as dimensions of electrodes and the initial gap between them and the stiffness of supporting beams are considered as random variables. The variation of these parameters within tolerance ranges drastically alters the capacitor's actual response from the desired one and results in low yield. Hence, design optimization with the objective of maximizing yield in early steps becomes very important. An effective method for yield optimization of MEMS capacitors under given fabrication uncertainties is introduced. The method utilizes aspects of the advanced first-order second-moment (AFOSM) reliability method to find a linearized feasible region to estimate the yield. The yield is calculated directly using the joint cumulative distribution function (CDF) over the tolerance box requiring no numerical integration and avoiding computational complexity. The optimal design verified by Monte-Carlo (M-C) simulation exhibits a significant increase in the yield. The main advantage of this method comparing to other design optimization methods is that the proposed method does not change the design topology or fabrication accuracy. It increases the yield by finding the optimum design variables as demonstrated in this paper.     

Microstructure characterization and compressive performance of 3D needle-punched C/C–SiC composites fabricated by gaseous silicon infiltration

3D needle-punched C/C-SiC composites were fabricated from carbon fiber reinforced carbon (C/C) preforms, with densities of 1.05?g/cm³ and 1.28?g/cm³, by the gaseous silicon infiltration (GSI) method at fabrication temperatures from 1500?°C to 1800?°C. The compressive strengths and elastic moduli in transverse direction are larger than those measured under longitudinal compression except that samples fabricated from 1.28?g/cm³ density exhibit lower elastic moduli in transverse direction than in longitudinal direction. The compressive strength and modulus increase with fabrication temperature at 1500?°C and 1600?°C, and then decrease with higher fabrication temperature. Samples fabricated from the lower density C/C preforms have greater compressive strength and modulus. X-ray tomography was applied before and after the mechanical tests to characterize the microstructure and damage patterns, and the results indicated that for C/C-SiC composites fabricated at 1700?°C from 1.28?g/cm³ density C/C preform the matrix has a volume fraction (vol%) of 36.9%, and the initial intra-bundle cracks (0.6?vol%) display a space crossing structure while the inter-bundle pores (6.0?vol%) are special irregularly distributed.     

Microbial efficacy and impact on the population of Escherichia coli of a routine sanitation process for the fabrication facility of a beef packing plant

The aim of this study was to assess the microbiological effect of a sanitation process used at a beef fabrication facility. On each of three fabrication days and the following mornings, samples were collected from meat contacting surface (CS) and non-contacting surface of two conveyor belts and from surfaces of cuttings tables before cleaning and before work, respectively, for recovery of total aerobes, coliforms and Escherichia coli. Selected presumptive E. coli isolates from belt 2 were purified and the confirmed isolates were genotyped using multiple-locus variable-number tandem-repeat analysis (MLVA). The numbers of aerobes before cleaning were mostly 6 log cfu/1000 cm² and were not significantly (p > 0.05) different from those before work. The log total numbers of coliforms and E. coli before cleaning and before work were largely similar. However, the numbers of samples from which no coliforms or E. coli were recovered were fewer before cleaning than before work. Of the presumptive E. coli isolates from CS and NCS before cleaning and before work, 88 (95%) and 1 (5%), and 134 (84%) and 78 (65%), respectively, were confirmed. MLVA of 89 (CS) and 212 (NCS) E. coli isolates revealed 18 and 16 distinct genotypes, respectively. Of the E. coli from CS, 98% were found at one sampling time. Of the E. coli from NCS, however, >90% were found more than once, and both before cleaning and before work. The findings show that the sanitation process did not have significant impact on the numbers of aerobes or coliforms, but was effective for removing E. coli from CS and to a lesser degree from NCS of conveyor belt.     

Upgrading Computational Design

Shajay Bhooshan heads up the computation and design ZHACODE group at Zaha Hadid Architects (ZHA) and is a course master at the Architectural Association Design Research Laboratory (AADRL). Here he argues that Parametricism 2.0 has a vital role to play in the progressing of computational design. Assimilating the exploratory developments of the last 15 years, he asserts how the next phase of Parametricism will enable a further consolidation and evolution of digital practices.