Effect of Alumina on the Structure and Mechanical Properties of Spark Plasma Sintered Boron Carbide

Uniform densification of relatively thick (~7 mm) consolidated boron carbide plates at relatively low temperatures (e.g. 1800°C) and low facture toughness are two of the primary challenges for further development of boron carbide applications. This work reports that these two challenges can be overcome simultaneously by adding 5 wt% alumina as a sintering aid. Nearly fully dense (97%), fine grained boron carbide (B₄C) samples were produced using spark plasma sintering at 1700°C and above in the B₄C‐5 wt% Al₂O₃ system. The alumina and boron carbide matrix reacted to form an Al₅O₆BO₃ (a mullite‐like phase) during sintering. The Al₅O₆BO₃ phase facilitated uniform densification via liquid phase sintering. This secondary phase is dispersed throughout the intergranular pores, providing obstacles for crack propagation and resulting in tougher boron carbide ceramics.     

FT-IR Microspectrometry Reveals the Variation of Membrane Polarizability due to Epigenomic Effect on Epithelial Ovarian Cancer

Ovarian cancer, as well as other cancers, is primarily caused by methylation at cytosines in CpG islands, but the current marker for ovarian cancer is low in sensitivity and failed in early-stage detection. Fourier transform infrared (FT-IR) spectroscopy is powerful in analysis of functional groups within molecules, and infrared microscopy illustrates the location of specific groups within single cells. In this study, we applied HPLC and FT-IR microspectrometry to study normal epithelial ovarian cell line immortalized ovarian surface epithelium (IOSE), two epithelial ovarian cell lines (A2780 and CP70) with distinct properties, and the effect of a cancer drug 5-aza-2''-deoxycytidine (5-aza) without labeling. Our results reveal that inhibition of methylation on cytosine with 5-aza initiates the protein expression. Furthermore, paraffin-adsorption kinetic study allows us to distinguish hypermethylated and hypomethyated cells, and this assay can be a potential diagnosis method for cancer screening.     

表面分析仪器在超疏水表面研究中的应用

超疏水表面制备与研究是近年来材料科学的重要研究方向,超疏水表面的研究离不开表面分析测试仪器。本文简要介绍了超疏水材料的表面特性、理论模型及其制备方法,重点介绍了扫描电子显微镜、X射线光电子能谱、原子力显微镜和表面接触角测试等几种常用表面分析方法的基本原理及其在超疏水表面研究中的具体应用。     

Three‐dimensional visualization of termite (Apicotermitinae) enteric valve using confocal laser scanning microscopy

Humivorous termites are dominant members of tropical rainforest soil communities. In the soil‐feeding subfamily Apicotermitinae (Termitidae), the enteric valve connecting the first section of the hindgut to the paunch often displays a complex sclerotized armature everted towards the lumen of the paunch. This structure is central in termite taxonomy but its function remains hypothetical. Here, we evaluate the potential of confocal laser scanning microscopy to provide detailed imaging of the valve of Anoplotermes parvus, by comparison with bright‐field microscopy and scanning electron microscopy. We detected a strong far‐red emission of the enteric valve armature that sharply contrasted with the surrounding tissues, providing a convenient method to highlight minute structural elements of the valve and its three‐dimensional structure. The method is easy to use and is applicable to standard archival material as demonstrated by images of enteric valves of four other Apicotermitinae species. It may represent a valuable asset for the study of termite enteric valves, for the purpose of taxonomy or functional morphology.     

Mechanical and tribological properties of nanostructured TiN/TiBN multilayer films

Nanostructured multilayer films of TiN/TiBN with different bilayer thicknesses (Λ) were deposited onto Si(1 0 0) wafers (for mechanical analyses) and AISI M42 tool steels (for tribological measurements) at room temperature by reactive unbalanced magnetron sputtering in an Ar–N₂ gas mixture. The effects of different Λ values on mechanical and tribological properties were studied by atomic force microscope (AFM), scanning electron microscope (SEM), microindentation measurements, Rockwell-C tester, nano- and micro-scratch tester, impact tester, pin-on-disc tribometer, and Fourier-transform infrared spectroscopy (FTIR). It was found that the mechanical and tribological properties of multilayer films (typically 1.4 ± 0.1 μm in thickness) were closely related to Λ (varied from 1.4 to 9.7 nm). For the best multilayer film with Λ = 1.8 nm, a maximum hardness of 29.5 GPa was achieved and the best cohesive and adhesive strength was evidenced in terms of critical load values of L_C1 (37 N), L_C2 (>80 N) and the highest adhesion strength (HF1). Moreover, by the dynamic impact testing this multilayer film could endure impact cycles up to 4 × 10⁵ without adhesive failure. It was also found that the nano-scratch test under single-pass and constant-load conditions showed that the frictional coefficients decreased with Λ and increased with normal load due to the ploughing effect. The enhanced hardness in the multilayer films with small Λ values improved the wear resistance and lowered the frictional coefficients. The frictional coefficients obtained at 5 N were kept at 0.5 and increased from 0.52 to 0.65 when Λ increased from 1.8 to 9.7 nm at 2 N. By FTIR analyses, the multilayer films with Λ = 1.8 and 2.2 nm showed the presence of h-BN which provided a lubricating function resulted in lower frictional coefficients and wear rates. The tribological properties of the TiN/TiBN multilayer films with different Λ values are also explained in terms of mechanical properties and wear mechanisms.     

Automated visual inspection for surface appearance defects of varistors using an adaptive neuro-fuzzy inference system

The purpose of this study is to develop an automated visual inspection system for analysis of the surface appearance of ring varistors based on an adaptive neuro-fuzzy inference system (ANFIS). Known image patterns of the six types of ring varistors are used in a training process to establish Sugeno FIS rules, and the input-output data are then set to train the ANFIS to tune the membership function. Feature extraction reduces image complexity using two-dimensional edge detection, calculated within divided rectangular region. The ANFIS combines the neural network adaptive capabilities and fuzzy logic qualitative to train a classification system for six different types of components. The performance of the ANFIS is evaluated in terms of training performance and classification accuracy. The results confirm that the proposed ANFIS is capable of classifying the six types of ring varistors with an accuracy of 98.67%. This paper has not been published elsewhere nor has it been submitted for publication elsewhere.     

A New Phenomenon Observed in Determining the Wear-Corrosion Synergy During a Corrosive Sliding Wear Test

Corrosive wear of materials is a complex surface failure process, which involves both the wear-accelerated corrosion and the corrosion-accelerated wear. Separating contributions of these two processes to the total material loss is of significance for gaining better understanding of the wear-corrosion synergy. Previous studies have generated an electrochemical scratch technique for measuring the wear-accelerated corrosion, based on which other components involved in the wear-corrosion synergy can be determined. In this article, a new phenomenon in measuring the wear-accelerated corrosion is reported. It was observed that for non-passivation materials there existed a stirring effect (by pin), which significantly affected the measurement. The resultant mistake was serious. The previous technique was modified accordingly and applied to determine the corrosion-wear synergy of AISI 1045 steel in comparison with that of AISI 304 stainless steel.