Preparation of ultra-fine copper powder and its lead-free conductive thick film

In this paper, non-agglomerated monodispersed ultra-fine copper metallic powders have been synthesized with chemical reduction method. Fine lead-free glass powders were also prepared by solid synthesis process. Thick film paste prepared by above-mentioned copper metallic powders and lead-free glass powders was applied as conductive paste of MLCC. Mixture of glass and zinc oxide give the thick film a high adhesion strength which is attributed to the rough interface from interfacial reaction between glass and chip, and a good densification. Diffusion of metal between copper thick film and nickel thick film is clear. Ni-Cu solid solution appears under high temperature firing.     

深过冷Fe76B12Si12超细晶材料的凝固组织与软磁性能

首次采用深过冷加水淬的方法,成功地制备了直径为16 mm的样品,高为15 mm,组织中颗粒平均尺寸约为120nm左右的Fe76B12Si12合金超细晶材料.其磁损耗P1T400和P1T1000分别为普通硅钢片的40%和65%.系统研究了组织类型及Fe2B(Si)相尺度对该合金软磁性能的影响,发现该合金的最佳软磁性能位于Fe2B(Si)相完全粒化的非规则共晶组织区,并且当Fe2B(Si)相尺寸细化至0.36～0.50μm时,其软磁性能随着相尺寸的减小而大幅度改善.对以上结果产生的原因进行了讨论.     

某硅钙质胶磷矿正反浮选实验研究

这是一篇矿物加工工程领域的论文。采用超细粉磨技术处理磷矿,可改变磷矿中含磷矿物的物理化学性质,从而提高磷矿中磷的溶解与释放,使其可作为磷肥使用。搅拌磨机作为超细粉磨设备,用其处理磷矿的可行性与工艺参数对磨矿效果影响的研究尚不完善。本文采用立式搅拌磨机对河北某磷矿进行湿法磨矿实验,粉磨产品的粒度分布通过NKT6100-D型激光粒度仪进行检测,探究磨矿工艺参数对产品粒度组成以及新生成粒级含量的影响,并通过R-R方程将产品粒度参数化分析,确定较适宜的工艺参数。结果表明,在搅拌器转速550 r/min、磨矿浓度65%、充填率60%、料球比0.5和磨矿时间30 min的条件下,获得有效磷含量和枸溶率分别为8.75%和74.03%,颗粒特征参数b为0.371、均匀性系数n为1.426的粉磨产品,可见用搅拌磨机对磷矿进行超细粉磨处理是可行的。     

ECAP+旋锻变形制备超细晶纯锆的低周疲劳行为研究

采用等径弯曲通道（ECAP）+旋锻（RS）复合变形技术制备了超细晶工业纯锆,通过轴向对称应变控制方法对超细晶纯锆的低周疲劳性能进行研究,讨论了超细晶纯锆的循环应力-应变响应及滞后回线,并分析了超细晶纯锆的软硬化特性、累积滞后规律并预测其疲劳寿命。结果表明：超细晶纯锆的循环软硬化特性依赖于外加总应变幅的大小,而且总应变幅大于1.0%时软化比达到峰值,循环软化特性最为显著。滞后回线面积随着总应变幅的增大而增大,当应变幅较小时出现“棘齿现象”。回归分析表明超细晶纯锆疲劳寿命满足Coffin-Manson经验关系式。     

Enhanced performance of direct peroxide/peroxide fuel cell by using ultrafine Nickel Ferric Ferrocyanide nanoparticles as the cathode catalyst

Direct peroxide-peroxide fuel cell (DPPFC) employing with H₂O₂ both as the fuel and oxidant is an attractive fuel cell due to its no intermediates, easy handling, low toxicity and expense. However, the major gap of DPPFC is the cathode performance as a result of the slow reaction kinetics of H₂O₂ electro-reduction and thus the target issue is to design cathode catalysts with high performance and low cost. Herein, different with using noble metal of state-of-the-art, we have successfully synthesized ultra-fine NiFe ferrocyanide (NiFeHCF) nanoparticles (the mean particles size is 2.5 nm) through a co-precipitation method, which is used as the cathode catalyst towards H₂O₂ reduction in acidic medium. The current density of H₂O₂ reduction on the resultant NiFeHCF electrode after the 1800 s test period at ?0.1, 0 and 0.1 V are 121, 93 and 76 mA cm², respectively. Meanwhile, a single two-compartment DPPFC cell with NiFeHCF nanoparticles as the cathode and Ni/Ni foam as the anode is assembled and displayed a stable OCP of 1.09 V and a peak power density of 36 mW cm^?2 at 20 °C, which is much higher than that of a DPPFC employed with Pd nano-catalyst as cathode.     

Release characteristics of four model drugs from drug-loaded electrospun cellulose acetate fiber mats

Ultra-fine fiber mats of cellulose acetate (CA; M_w ≈ 30?000 Da; degree of acetyl substitution ≈ 2.4) containing four different types of model drugs, i.e., naproxen (NAP), indomethacin (IND), ibuprofen (IBU), and sulindac (SUL), were successfully prepared by electrospinning from 16% w/v CA solutions in 2:1 v/v acetone/N,N-dimethylacetamide (DMAc). The amount of the drugs in the solutions was fixed at 20 wt.% based on the weight of CA powder. The morphology of the drug-loaded electrospun (e-spun) CA fiber mats was smooth, with the average diameters of these fibers ranging between 263 and 297 nm. No presence of the drug aggregates of any kind was observed on the surfaces of these fibers, suggesting that the drugs were encapsulated well within the fibers. After submersion in the acetate buffer solution at 37 °C for 24 h, the drug-loaded e-spun CA fiber mats swelled particularly well (i.e., 570-630%), while the corresponding solvent-cast film counterparts did not. The release characteristics of the model drugs from both the drug-loaded CA fiber mats and the drug-loaded as-cast CA films were carried out by the total immersion method in the acetate buffer solution at 37 °C. At any given immersion time point, the release of the drugs from the drug-loaded e-spun CA fiber mats was greater than that from the corresponding as-cast films. The maximum release of the drugs from both the drug-loaded fiber mats and films could be ranked as follows: NAP > IBU > IND > SUL.     

一种低温早强低密度水泥浆

低温下,常规低密度水泥浆体系早期强度发展缓慢,水泥石胶结能力差,影响了水泥环封固质量,浅层易漏井固井质量问题日益突出,为此,进行低温早强低密度水泥浆体系研究。根据紧密堆积理论及综合室内实验研究,研制了密度为1.30~1.50 g/cm3的低温早强低密度水泥浆体系,主要优选了超细胶凝材料和锂盐复合早强剂,增加了低密度水泥石的致密性,提高了低密度水泥石的早期强度,25℃凝结时间为13 h,24 h抗压强度为10.2 MPa。该体系具有低温早期强度高,凝结时间短,稳定性好等优点。在大庆油田现场成功应用2口井,固井质量合格率100%,取得良好的应用效果。      

井壁强化与堵漏双作用可钻水泥实验研究

针对常规复合堵漏材料之间无胶结、易被钻井液冲刷、使用油井水泥堵漏会造成新井眼的问题,研究开发了井壁强化与堵漏双作用可钻水泥。将超细碳酸钙粉体加入新型胶凝材料硫铝酸盐水泥中,调节胶凝材料的可钻性,研究表明,当超细碳酸钙粉体的加入量不大于7%时,水泥凝胶材料的强度随粉体加入量的增加而增加,而当粉体的加入量大于7%时,水泥凝胶材料的强度随粉体加入量的增加而减小,即可钻性变好;在硫铝酸盐中加入0.4%减水剂、0.3%提黏剂、0.6%缓凝剂时,其稠化时间达到155 min,为安全施工提供了条件;在可钻水泥中加入12%鳞片状云母、1%纤维、1.5%石灰岩颗粒作为堵漏剂,较好地增强了体系堵漏性能,能够较好地封堵3 mm和5 mm缝板裂缝。可钻水泥的研发为实现钻井过程中井壁强化与堵漏双作用提供了技术保障。      

Microstructural and mechanical properties of commercially pure aluminum subjected to Dual Equal Channel Lateral Extrusion

This paper aims to provide an introductory insight about “Dual Equal Channel Lateral Extrusion”, a counterpart of “Equal Channel Angular Extrusion”. The process is implemented to severely refine the microstructure of aluminum slabs. Comparisons of macroscopic parameters as average straining and large scale distribution of strain, as well as process loads reveal the supremacies and short comings of DECLE with respect to ECAE. DECLE shares a relatively similar geometry of deformation with that of ECAE. The advantages of this process with respect to ECAE are: (i) more intensive strains attainable per pass, and (ii) less extruding power needed for a given sample size. Nonetheless, less homogeneous strain per pass is seen in case of DECLE. TEM inspections revealed remarkable refinement of the microstructure through out the process and also some recrystallization at the final passes. Hardness tends to increase through successive passes to a limiting value beyond which there appeared a decline associated with intense recovery and the recrystallization observed. Compression tests exhibit the same trend, viz. a general rise in strength followed by a decrease in work hardening with increasing number of passes, leading to uniform microstructure and hardness after 9 passes.     

The mechanism study of ultra-fine fly ash sintered material performance

Abstract

In view of production of fly ash and coal gangue is very large, much attention has been paid to the problem of its resource utilization. Using ultra-fine fly ash, coal gangue and clay to roast into lamellose brick at different temperatures by certain proportion, at the same time, using fly ash to replace ultra-fine fly ash as the contrast group. In addition, we have been further studied it by using XRD, SEM, TG-DTA and other means. This article studies the superiority of using ultra-fine fly ash and coal gangue instead of clay to roast into brick and the mechanism of ultra-fine fly ash sintered material. Research shows that: the brick mixed with ultra-fine fly ash than an equal amount of fly ash has better physical properties after roasting 100?min in 100?°C. Bibulous rate can reach 10%; compressive strength reaches MU30 high-class level; Thermal coefficient of conduction is 0.41 W/(m·K).There are significant characteristics peaks of quartz and mullite on the XRD diffraction pattern of bricks. SEM photos shows that quartz cover a small amount of mullite and sintered sample is the dense; TG-DTA thermal mechanism shows that the best sinterning temperature of the sample is 1150?°C.The study shows the necessity of ultra-fine fly ash processing.