The effect of nano-size additives on the electrical conductivity of matrix suspension and properties of self-flowing low-cement high alumina refractory castables

Influence of two nano-size additives on electrical properties of suspension matrix of self-flowing low-cement high alumina refractory castable is investigated. For this purpose, castament FS 10 and FS 20 on the basis of polycarboxylate ether were considered. The self-flow value, workability and mechanical strength of the castable are evaluated and their relations with electrical conductivity are determined. Using these relations, the type and optimum amount of proper additive for these refractory castables are determined. It was shown that if the electrical conductivity of matrix suspension is less than 0.71 mS/cm, high alumina low-cement self-flowing refractory castable can be obtained. The best self-flow, sufficient working time and adequate mechanical strength in the castables are obtained with 0.08 wt.% FS 20.     

纳米结构Ni-Al_2O_3梯度涂层的制备及结构表征（英文）

将微米级的Ni和Al_2O_3粉末通过行星式球磨机沉积在固定于球磨罐内顶端的铝板上,制备纳米结构的Ni-Al_2O_3复合涂层。共采用五组不同Ni与Al_2O_3质量比(1:1~16:1)的混合粉末,并制备一组纯Ni涂层。用XRD、SEM和TEM技术对涂层的相组成和微观结构进行表征。结果表明,初始混合粉末的成分对涂层中Al_2O_3颗粒的含量和微观结构有很大影响。Al_2O_3含量高的初始混合粉沉积的涂层中,Al_2O_3颗粒所占体积分数大。虽然通过本研究的方法可沉积出含有50%Al_2O_3颗粒的Ni-Al_2O_3复合涂层,但其性能差,制备出的致密度高、无裂纹和/或孔洞的涂层中Al_2O_3颗粒的含量小于20%,且需用Ni和Al_2O_3质量比≥4:1的初始混合粉制备。研究还发现,机械和冶金结合是涂层和铝基体结合的主要机理。通过在同一制备条件下沉积两种独立的涂料层可以成功制备出具有较好的致密度和完整性的功能梯度复合涂层。     

The synergistic effect of seawater's parameters on the corrosion rate of the austenitic stainless steel 304

In this article the corrosion rate of the austenitic stainless steel type 304, under the synergistic effect of environmental factors has been assessed via potentiodynamic polarization scan. Salinity, velocity, pH and temperature are the factors which induce effects on the corrosion rate of the considered metal. Quantitative analysis is applied using the full two-level factorial experimental design method, which results in the contribution value of each parameter in changing the quantity of average corrosion rate in both individual and synergistic cases. Besides this quantitative analysis, qualitative analysis has been used to predict the variation direction. These two analyses show the important role of the synergistic action, which changes the variation direction of corrosion rate and the contribution percentage of each parameter in varying the value of corrosion rate. Applying both these analyses can show the magnitude and quality of each parameter’s effect, which is remarkably valuable in marine applications.     

Passive Behavior of Ultra-Fine-Grained 1050 Aluminum Alloy Produced by Accumulative Roll Bonding in a Borate Buffer Solution

In this study, the effect of the ARB process on the passive behavior of ultra-fine-grained 1050 aluminum alloy in a borate buffer solution(p H 6.0) has been investigated. The result of the microhardness tests revealed that the microhardness values increase with an increasing number of ARB cycles. The potentiodynamic polarization plots revealed that the higher number of cycles for the specimens proceeds with the ARB process rather than annealing yield to lower corrosion and passive current densities and more noble corrosion potential values. Moreover, electrochemical impedance spectroscopy measurements showed that increasing the number of ARB cycles offers better conditions for forming the passive films.     

Hydrodynamics characterization of the Maxblend impeller

The hydrodynamic characteristics of the Maxblend^TM impeller have been investigated in the case of viscous Newtonian fluids. Both laboratory experiments and 3D finite element based computational fluid dynamics (CFD) simulations have been carried out. The power consumption, the mixing evolution yielding the mixing time, and the effect of baffles in the laminar and transition flow regimes have been determined. It was found that the limit Reynolds number between the laminar and transition regimes is approximately 25 and 38 for the unbaffled and baffled configurations, respectively. Based on the range of Reynolds numbers studied in this work, the best window performance of the Maxblend^TM mixer where fast and homogenous mixing is achieved is the end of the laminar regime and the early transition regime with baffles.     

Study of a novel and simple method of generating binary mask for microprism fabrication

A new and simple method for generating binary masks for fabrication of gray scale micro-optical elements is proposed and examined. In this technique the main idea is superimposing two or more gratings with slightly different pitches that depend on the considered gray tone level. This causes generation of a chirped binary mask in which the openings widths are changed from a maximum to minimum through considered steps. Furthermore, to show its capability, it was applied to fabricate some microprisms. In addition, influence of proximity gap, and designation parameters on the surface quality were studied. It is shown that surface deterioration is effectively modified by optimizing the designation parameters. In comparison to other techniques, one of the advantages of this method is to have an assortment of pulse modulated masks that are able to create a variety of gray tone levels. Other advantages are ease in designation and implementation, and the fact that surface roughness could be smoothed effectively by aptly optimized parameters. Theoretical approach, simulation works, and experimental results are presented.