铝电解工须知(4)

现在介绍电解槽中氧化铝加入量过少或过多时的后果。正常生产槽加入氧化铝过少时的后果: 1.电流效率下降理论和实践都证明,当电解质中氧化铝含量为5.0～5.5％时电解槽     

液-液萃取法分离铂族金属

从矿石提取铂族金属,将其精制到所要求的很高纯度,以应多方面的使用,需要大量复杂的操作过程。现在,从铂族混合液中,产出单一铂族金属的最终精制过程,是用选择沉淀来实现,然而,就分离程度而论,其效率是低的。一种改进的方法——液—液萃取法,已发展到中间工场阶段。本文在此法分离的基础上,着重谈某些化学及操作的原理。     

在流态床中渗碳

作者解释了在间接加热的流态床炉中渗碳的机理及用计算机模拟和控制渗碳过程的某些独有的特性,并对氮——甲醇气氛的使用进行了分析。     

用真空电弧蒸发的PVD工艺

PVD 工艺在机械应用中,产生等离子体的有商业价值的方法有三种,它们是离子轰击溅射,熔池蒸发和电弧放电蒸发。这篇文章介绍了 PVD 电弧蒸发技术,讨论了用电弧形成金属蒸气相的主要机理,描述了产生 TiN 和其他合金或硬覆层的工业应用工艺过程。PVD/电弧系统是在真空中进行的工艺。等离子源来自位于真空室边侧和顶部的几个电弧蒸发器。每一个蒸发器产生等离子体,从许多电弧点来的物质造行沉积。这样,高度集中的电弧放电导致阴极材料的瞬时蒸发,这许多弧点形成一个自维持弧,产生很高能量和浓聚的等离子体。试验表明,在覆层之前特定的基体侵蚀和蒸气中金属离子的高密度,是有助于获得致密的坚硬的而且结合非常牢固的覆层的主要因素。本文最后要探讨这个工业生产工艺的进一步发展。或许我们将看到,在结构和成分上适合用于解决某些特殊问题的多元覆层。这种覆层可使用多源特性的电弧蒸发进行沉积。电弧蒸发源工艺将在以下几个方面继续发展;生产控制、自动化、蒸发源设计的改善、系统规格的加大,以及涂覆长达3m 的大件。在机械制造领域,TiN 和其他硬覆层的使用仅仅是开始。未来年代,这类覆层的应用几乎是无限的,今后电弧蒸发源沉积工艺将发挥显著的作用。     

Experimental Study of Microstructure Evolution during Tempering of Quenched Steel and Its Application

LARGE-SIZED FORGINGS are usually intensivelyquenched to obtain the desired microstructuredistribution,high strength and hardness.Becauseresidual stresses are high in quenched large-sizedforgings,tempering processes follow quenchingprocesses to reduce the residual stress and obtain goodmechanical properties.Several differentmicrostructures are generated in quenched steelforgings,such as martensite,bainite and retainedaustenite.Modeling of microstructure evolution inquenched steel during …     

鋁电解工艺的现状

历史資料在第二次世界大战之前,彼施涅公司的鋁厂装备的是3～5万安培的預焙阳极电解槽和2～3万安培的側部导电自焙阳极电解槽。电解槽的技术指标列于表1。     

W-Ni-Cr系高比重合金

研究了W-Ni-Cr系高比重合金的硬度和机械性能。这些合金的硬度较一般合金高得多(Hv值高达600,而W-Ni-Fe合金的Hv值为310)。该合金系的机械性能,按合金成分可分为截然不同的二类:一类是铬镍比(Cr:Ni)低的——塑性较好,硬度略高;另一类是铬镍比高的——硬度高,抗张强度低,几乎没有塑性。为了解释W-Ni-Cr系合金的这种性质,本文确定了该合金系相图的1250℃截面图,证明了三元σ脆性相的存在。延性-脆性转变界限与有σ相的相区边界相对应。对σ相稳定性的研究表明,不可能用简单的热处理消除σ相。在高硬度的合金中,添加第四组元不能阻止σ相生成。     

Matrix expression and vaccination control for epidemic dynamics over dynamic networks

This paper investigates epidemic dynamics over dynamic networks via the approach of semi-tensor product of matrices. First, a formal susceptible-infected-susceptible epidemic dynamic model over dynamic networks (SISED-DN) is given. Second, based on a class of determinate co-evolutionary rule, the matrix expressions are established for the dynamics of individual states and network topologies, respectively. Then, all possible final spreading equilibria are obtained for any given initial epidemic state and network topology by the matrix expression. Third, a sufficient and necessary condition of the existence of state feedback vaccination control is presented to make every individual susceptible. The study of illustrative examples shows the effectiveness of our new results.     

Computer-aided methods in bespoke breast prosthesis design and fabrication

This case study presents a method of utilizing computer-aided design technologies to provide bespoke, external breast prostheses. The technique is illustrated through a case study of a mastectomy patient. Photogrammetry methods were used to capture the breast form when supported by a brassiere and the unsupported breast and defect side. Computer-aided design techniques were used to generate a digital prosthesis based upon the supported breast shape and with a fitting surface that matched the defect side. Furthermore, a two-part mould was designed and fabricated using rapid prototyping methods. A colour-matched prosthesis was then fabricated in a gel-based, platinum-cured silicone.     

Synthesis and structure-activity study of quaternary ammonium functionalized beta-cyclodextrin-carboxymethylcellulose polymers

Carboxymethylcellulose (CMC) and beta-cyclodextrin (beta-CD)-based polymers functionalized with two types of quaternary ammonium compounds (QACs), the alkaquat DMB-451 (N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride) (DMD-451) named polymer DMB-451, and FMB 1210-8 (a blend of 32 w% N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride and 48 w% of didecyldimethylammonium chloride) named polymer FMB 1210-8, were synthethized and characterized by Fourier transform infrared spectroscopy. The antimicrobial activities of these polymers against Eschericia coli were also evaluated at 25 degrees C in wastewater. The results have indicated that the polymer FMB 1210-8 possesses a high-affinity binding with bacterial cells that induces a rapid disinfection process. Moreover, in the same experimental conditions of disinfection (mixture of 1.0 g of polymer and 100 mL of wastewater), the polymer FMB 1210-8 has a higher antimicrobial efficiency (99.90%) than polymer DMB-451 (92.8%). This phenomenon might be associated to a stronger interaction with bacterial cells due to stronger binding affinity for E. coli cells and greater killing efficiency of the C10 alkyl chains QAC of polymer FMB 1210-8 to disrupt the bacterial cell membrane as compared to N-alkyl (50% C14, 40% C12, 10% C10) dimethylbenzylammonium chloride. Together, these results suggest that the polymer FMB 1210-8 could constitute a good disinfectant against Escherichia coli, which could be advantageously used in wastewater treatments due to the low toxicity of beta-CD and CMC, and moderated toxicity of FMB 1210-8 to human and environment.