What causes differences of C-S-H gel grey levels in backscattered electron images?

Backscattered electron (BSE) images of heat-cured concretes show alite grains surrounded by inner C-S-H gel of two distinct grey levels (referred to as two-tone inner C-S-H gel). The lighter rim forms at elevated temperature whereas the darker rim develops during subsequent exposure to moisture at 20 °C. This microstructural feature can potentially be used as an indicator to assess the curing history of a concrete. However, microstructural examinations of room-temperature concretes containing silica fume or which have been exposed to severe conditions (external sulfate, carbonation) also show distinct rims of two-tone inner C-S-H gel.The chemical compositions of the rims were determined by EDX microanalysis in the scanning electron microscope (SEM). Our results show that for heat-cured samples, the different grey levels of the two-tone inner C-S-H are caused by relative differences in microporosity and water content and not by ones in chemical composition. However, in silica-fume blended concrete, sulfate attacked or carbonated specimens the different grey levels of the two-tone inner C-S-H gel were associated with significant differences in chemical composition. This difference allows two-tone inner C-S-H gel arising from heat curing to be distinguished from that arising from these other causes.     

Stickiness, Functionality, and Microstructure of Food Powders

Three major aspects of food powder are described and discussed. Stickiness is one issue that can cause production and product handling difficulties. Stickiness has been interpreted in a number of ways and thus measured differently. Functionality of the primary (single) particles or agglomerated powders is of practical interest to the consumers. The desired quality will have to be matched or exceeded by the powder manufacturers. Finally, microstructure provides a key linkage between the production and the functionality. Its formation has impacts on both the stickiness and functionality.     

混合稀土对AZ91镁合金在NaCl溶液中的腐蚀行为影响

通过静态失重法、极化曲线和交流阻抗测试研究了混合稀土 (Re)对AZ91镁合金腐蚀行为的影响。结果表明 :Re的加入使AZ91微观组织得到改善 ,减缓了AZ91镁合金在NaCl溶液中的腐蚀     

掺杂对低压ZnO压敏陶瓷材料显微结构及性能的影响

本文探讨了多种金属氧化物对ＺｎＯ－Ｂｉ＿２Ｏ＿３－ＴｉＯ＿２系材料的改性作用和对其微结构的影响，为得到预定性能的材料提供了掺杂方面的实验依据。     

Optimizing the Vacuum Heat-Treatment of Hot-Work Tool Steels by Linear Elastic Fracture Mechanics

Linear elastic fracture mechanics was used to optimize the vacuum heat-treatment procedures for conventional hot-work AISI H11 tool steel. The fracture toughness was determined with non-standard, circumferentially notched and fatigue-precracked tensile-test specimens. The fracture-testing method is sensitive to changes caused by variations in the microstructure resulting from the austenitizing and tempering temperatures as well as the homogeneity of the material itself. The combined tempering diagram- Rockwell-C hardness, Fracture toughness K_Ic, Tempering temperature was used for the choice of the vacuum heat-treatment parameters necessary to obtain the best properties for a given application with respect to the investigated steel.     

(Nb,Ti)C的制备方法对(Nb,Ti)C-35Ni金属陶瓷的微观结构及性能的影响

用自蔓燃高温合成（SHS）技术及电弧熔融法制备的（Nb，Ti）C固溶体作基体，制备（Nb，Ti）C－35Ni金属陶瓷。结果表明用电弧熔融法制备的（Nb，Ti）C为基的试样具较优的室温力学性能（σ＝1630MPa，KIC＝18．0MPa），其陶瓷颗粒均匀分行粘结相之中并是包裹结构；而用SHS法制备的（Nb，Ti）C为基的试样其力学性能相对较差，其陶瓷颗粒无包裹结构．     

Preparation of flat-polished specimens for SEM-backscattered electron imaging and X-ray microanalysis—importance of epoxy impregnation

Representative and quantitative microstructural information of cement-based materials can be obtained in the backscattered electron and X-ray modes of the scanning electron microscope (SEM). One prerequisite, of several, is to use flat specimens. Microstructures that are minimally affected by the grinding and polishing necessary to produce the flat surface can be obtained. It is essential to fill the pores of the specimen with epoxy resin prior to grinding and polishing. After hardening, the epoxy stabilizes the microstructure and enables it to withstand the stresses of grinding and polishing without alteration. In the present paper, we describe a preparation technique that we consider to have produced excellent polished specimens. The importance of epoxy impregnation is demonstrated.     

Creation of Ultra-precision Microstructures with High Aspect Ratios

In recent years, ultra-precision micromachining technology has been used in a variety of fields such as optical instruments, electronic devices, medical equipments, etc. At present, it is essential to meet the requirement of producing various shapes, one of which is a structure with a high aspect ratio. Such structures are applied, for example, to a shaft of micro robot, a long part of microactuator and micromachine, a microneedle for syringe, etc. However, due to its fragile nature, it is extremely difficult to fabricate the structure with a high aspect ratio since it is easily damaged during cutting. It is intended to produce micro towers with high aspect ratios by applying the ultra-precision milling technology using a single crystal diamond cutting tool. The method enables accurate creation of a variety of microstructures with high aspect ratios. In addition, the study also proposes a new machining method to create microneedle arrays, avoiding the contact of cutting edge with already machined parts again. As a result, it is concluded that the proposed method has the potential of producing a variety of microstructures with high aspect ratios.     

Issues in modelling of advanced heterogeneous ceramics

Summary The conceptual and computational issues regarding the development of models to predict microstructure/mechanical-property relationships in advanced ceramics are discussed. Advanced ceramics provide a particular challenge because their higher toughness or reliability, relative to monolithic ceramics, is a result of stable, distributed damage evolution. Capturing the details of distributed damage at atomistic and microstructural length scales is computationally prohibitive, but only in certain systems does it appear plausible to neglect atomistic and crack-tip details in favor of larger-scale damage propagation and interaction. Examples, mainly from the author's own work, are briefly presented to indicate the range of problems that have been addressed and the relative successes and failures.