Micro fabrication of stainless steel micro components using soft moulding and aqueous slurry

Presented is a fabrication process of stainless steel micro components. The fabrication process is divided into two main parts. In the first part, high quality SU-8 master moulds and their negative replicas from soft moulds are produced using photolithography and soft moulding techniques, respectively. The second part includes preparation of stainless steel slurry, filling the soft mould, obtaining the green parts, de-binding and sintering to the finial parts. The metallic slurry is investigated in details and the optimum dispersant and binder are obtained. Two different sintering conditions are investigated, vacuum and forming gas atmospheres. The effect of sintering atmospheres and temperatures on both density and linear shrinkage of the micro components are studied in details. The results show high quality micro components the same quality as the master moulds. The maximum sintered density and linear shrinkage are obtained when the samples are sintered in vacuum at 1350 °C and found to be 98.1% and 17.97%, respectively. The surface roughness of the sintered micro components is also investigated.     

从石棉尾矿中回收磁铁矿新工艺

青海某大型石棉矿尾矿含铁量较高,经过一次干式粗粒抛废,可以获得含铁量为27.62%的粉矿。该有害杂质含量较低的磁铁粉矿,经重磁联合选矿工艺、单一弱磁选工艺及加分散剂的弱磁选工艺流程试验研究,可以看出,富含石棉纤维的该试样,只有在石棉纤维得到很好分散的情况下才能取得理想的工艺技术指标,最终精矿铁品位为63.19%、回收率为74.58%,经济和社会效益显著。     

Rheology of pyrite slurry and its dispersant for the biooxidation process

Rheology of slurry significantly influenced the grindability, fine grinding performance and energy consumption of industrial minerals in wet grinding. The solid concentration, particle size, temperature and the dispersant, which affected the rheological characteristics of pyrite slurry and the biooxidation process were investigated in this study. This research aimed at the wet grinding process improved by the control of slurry rheology and getting a biocompatible dispersant.The results revealed that the viscosity increased with the solid concentration, which was in agreement with the Chong model. There was a critical concentration (40 wt.%) that led to the flow behavior of slurry transformed from Newtonian fluids to shear-thinning non-Newtonian fluids which fitted to the Casson model. It was also found that the apparent viscosity of slurry increased with the decrease of the particle size and the temperature at high solid concentration.Sodium Hexametaphosphate (SH) was selected experimentally as an effective dispersant for the mineral slurry. The appropriate concentration of SH was also determined at the range from 0.005 wt.% to 0.05 wt.%. The addition of dispersants could reduce the viscosity and yield stress, increase the zeta potential (ζ) of suspension pronouncedly. No negative effects on the growth rate of microorganisms and the pyrite biooxidation were observed. Therefore, dispersant separation and recovery process could be avoided.     

Dispersion behaviour of laser-synthesized nanometric SiC powders in aqueous medium with ammonium polyacrylate

The dispersion behaviour of laser-synthesized nanometric SiC powders in water using ammonium polyacrylate (molecular WEIGHT=10,000) as dispersant was investigated. The influence of oxidation, presoaking time, ammonium polyacrylate (NH₄PA) concentration, and pH on suspension stability and coagulation rate of aggregates was determined. The stabilization mechanism is discussed. Excellent dispersion stability was obtained for oxidized (500 °C) powders containing 2.45 wt.% NH₄PA at pH 9.25 after a lengthy aging treatment.     

Accelerating dissipative particle dynamics with multiple GPUs

Dissipative particle dynamics (DPD) simulation is implemented on multiple GPUs by using NVIDIA’s Compute Unified Device Architecture (CUDA) in this paper. Data communication between each GPU is executed based on the POSIX thread. Compared with the single-GPU implementation, this implementation can provide faster computation speed and more storage space to perform simulations on a significant larger system. In benchmark, the performance of GPUs is compared with that of Material Studio running on a single CPU core. We can achieve more than 90x speedup by using three C2050 GPUs to perform simulations on an 80∗80∗80 system. This implementation is applied to the study on the dispersancy of lubricant succinimide dispersants. A series of simulations are performed on lubricant–soot–dispersant systems to study the impact factors including concentration and interaction with lubricant on the dispersancy, and the simulation results are agreed with the study in our present work.     

Efficiency of Dodecenylsuccinic Amide of n-Phenyl-p-Phenylenediammine as Novel Multifunctional Lubricant Additive for Deposit Control and Lubricity

A novel multifunctional amide additive N-phenyl-p-phenylenediamine-dodecenylsuccinic anhydride (PPA-DDSA) was synthesized by the reaction of DDSA and N-phenyl-p-phenylenediamine. The successful synthesis of amide additive was confirmed by various analytical techniques like Fourier Transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. Performance of prepared additive was evaluated as multifunctional additive for anti-oxidant, detergent dispersant, anti-corrosion, and lubricity properties. The MAK-500® mineral base oil and synthetic polyol base oil were used as a reference. The antioxidant property was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl method, which revealed that PPA-DDSA was better antioxidant than PPA and gallic acid but less effective than butylated hydroxytoluene. PPA-DDSA was found to be excellent detergent dispersant in polyol in comparison to the MAK-500. At 4000 ppm additive concentration, the coking value is reduced to 0.0205 g from the value of 0.0840 g for blank polyol while the % dispersancy increased to 40.67 from 20.00 for polyol base oil. The anti-wear property was observed to be better in the MAK-500 while the antifriction potential was found to be better in polyol base oil. The average wear scar is reduced from 881 to 550 μM at 2000 ppm concentration in MAK-500 base oil, while at 3000 ppm PPA-DDSA concentration, the average friction coefficient reduces to 0.0826 from 0.1276 for blank polyol.     

Electrochemical Deposition of Composites Using Deoxycholic Acid Dispersant

A biomimetic method has been used for the electrodeposition of carbon nanotubes (NTs) and composite films using a commercial bile acid. Thin films of deoxycholic acid (DCH) were prepared potentiodynamically and galvanostatically from deoxycholic acid sodium salt (DCNa) solutions. The anodic deposition yield has been investigated at different DCNa concentrations. The electrodeposition mechanism involved electromigration of anionic DC^? species, local pH reduction at the anode, and precipitation of DCH. It was found that DCNa allowed excellent dispersion of NTs in water. The use of DCNa as a multifunctional agent for NTs dispersion, charging, and binding allowed electrodeposition of NTs and composite MnO₂–NTs films. The MnO₂–NTs composites were used for charge storage applications in supercapacitors. The MnO₂–NTs electrodes showed good capacitive behavior. DCNa is a promising charging dispersant for NTs dispersion and manufacturing of other composites by electrochemical methods.     

分散剂在BaTiO3浆料中的分散机理

分散剂能降低分散体系中物质的聚集。在制备BaTiO3陶瓷浆料时加入分散剂,有利于形成分散液和悬浮液。本文分析了分散剂对浆料颗粒形状的影响机理,它是使颗粒间形成双电层的厚度增加,导致了颗粒间静电斥力变大,浆料悬浮并相对稳定。     

超支化分散剂对PP/CaCO3复合材料性能的影响

以丙烯酸甲酯和二亚乙基三胺为原料,通过缩聚反应制备了一种水溶性端氨基超支化聚合物(HBP-NH2),以其与硬脂酸酯化反应制备而得超支化分散剂(HBPR),采用傅立叶红外光谱(FTIR)对其结构进行表征.将该超支化分散剂作为碳酸钙(CaCO3)/聚丙烯(PP)复合材料的界面相容剂,研究其对复合材料的力学性能、热性能和微观结构的影响,提出复合材料界面增容的机理.实验结果表明:该超支化分散剂处理后的PP/CaCO<,3>复合材料,其界面相容性得到很大的提高,其力学性能提高显著,冲击强度比未处理的复合材料提高了53.6%.