表面分散剂对电化学制备纳米铜粉的影响

为探讨表面分散剂对电化学制备铜粉的影响,以十二烷基硫酸钠、吐温20、吐温40和吐温80单独或复配作为表面分散剂,采用电化学法制备出不同形状、不同尺寸的纳米铜粉.利用XRD、TEM及FT-IR等手段对所制备的纳米铜粉的物相、形貌及粒径大小进行了分析.研究结果表明:不同的表面分散剂对采用电化学所制备的纳米铜粉的作用是不同的...     

酸性蚀刻废液制备纳米铜粉及其稳定性研究

以酸性蚀刻废液为铜源,水合肼为还原剂,采用液相还原法制备纳米铜粉.研究发现,在氯离子的存在下,直接还原难以得到高纯度的铜粉.介绍了络合还原和除氯后还原两种铜粉制备方法,用铜粉导电率表征其抗氧化性能,并对两种方法制备的铜粉的稳定性进行了比较分析.     

纳米铜粉研制进展

本文综述了国内外纳米铜粉的研究状况 ,采用KBH4 液相还原法试制了一种纳米铜粉     

纳米铜润滑油添加剂的制备及其摩擦学性能

为了研究纳米铜粉的制备与其摩擦学性能,利用高能球磨机采用干湿磨相结合的方法制备了纳米铜粉,再将其加入500SN齿轮油中制成润滑油添加剂,用透射电镜(TEM)及万能磨擦磨损试验机研究了纳米铜粉的微观形貌及其润滑油添加剂的摩擦学性能。结果表明:纳米铜粉粒径为10～40 nm,在修饰剂中分散较好,颗粒表面有明显包覆层;纳米铜润滑油添加剂可提高基础油的减摩抗磨性能;纳米铜粉含量0.05%的纳米铜润滑油样的摩擦学性能最好且摩擦系数最低;低载荷下纳米铜润滑油样的摩擦学性能优于高载荷下的。     

纳米铜及稀土铜合金粉的研究进展

综述了目前纳米铜粉制备过程中解决纳米颗粒容易团聚及防止纳米铜粉氧化的方法，重点介绍纳米稀土对纳米铜粉颗粒团聚的抑制作用。研究中发现稀土元素对铜的性能有极大的促进作用，在此基础上，展望了稀土铜合金粉这种高效产品的应用前景。     

纳米铜粉研制进展

本文综述了国内外纳米铜粉的研究状况,采用了KBH4液相还原法试制了一种纳米铜粉。     

纳米铜在润滑油基础油中的制备及性能表征

本文以自制甲酸铜为原料,在润滑油基础油的保护下,采用热分解方法成功制备出用作润滑油添加剂的纳米铜粉。本文还通过正交试验法研究了Cu2+的初始浓度、球磨时间、热分解温度以及搅拌速度对铜粉粒径的影响,并用XRD和TEM对纳米铜粉进行了粒径计算和形貌观察;本文采用四球摩擦磨损机对添加了纳米铜粉润滑油添加剂的甲基硅油进行了极压性能PB值的测试,测试结果表明:当制备工艺参数Cu2+的初始浓度0.33mol/L、球磨时间12h、热分解温度200℃、搅拌速度30rad/min时,所制纳米铜粉粒径分布均匀,呈球形,表面未氧化,平均粒径为42nm;添加了纳米铜粉的甲基硅油的极压性能显著提高。     

纳米铜粉的制备及其分散性研究

采用液相还原法制备纳米铜粉和纳米铜胶体,选用十六烷基三甲基溴化铵(CTAB)或聚乙烯吡咯烷酮(PVP)为分散剂,通过X射线衍射仪、扫描电镜对纳米铜粉进行表征,通过重力沉降法测试纳米铜胶体的稳定性。结果表明:液相还原法能够制备纯度较高的纳米铜粉;CTAB浓度为0.12 mol/L时,铜粉平均粒径最小,为20 nm,CTAB浓度为0.14 mol/L且超声粉碎20 min时,纳米铜胶体最稳定;PVP浓度为6×10^-4 mol/L时,铜粉平均粒径最小,为20 nm,PVP浓度为7×10^-4 mol/L且超声粉碎20 min时,纳米铜胶体最稳定。     

水合肼还原铜氨废液制取纳米铜粉

以铜氨废液为原料,水合肼为还原剂制备纳米铜粉。在水合肼浓度为3mol/L、pH值为10.0、温度为75℃的条件下,铜离子沉淀率可达98.66%。采用X射线衍射仪对铜粉进行了表征,并讨论了制备条件对纳米铜粉的影响。     

真空冷冻干燥法制备纳米铜粉的实验研究

为了提高纳米铜粉的分散性,以五水硫酸铜和次亚磷酸钠为原料,采用三种不同的冻结方式:-55℃直接冷冻、抽真空快速冷冻、液氮急速冷冻,用真空冷冻干燥法制备了纳米铜粉。通过透射电子显微镜、X射线衍射仪对产物的粒径、纯度进行了检测。结果表明,冻干法制备的粉体纯度较高、颗粒细小、形状规则、无硬团聚;三种冻结方式制备的样品粒径分别为8~45 nm,4~25 nm,3~20 nm。采用表面修饰法对粉体进行表面改性,相比市售纳米铜粉,冻干纳米铜粉改性后作为润滑油添加剂的分散稳定性较好,采用抽真空冻结的纳米铜粉最好,其油样在18 h后能稳定分散,9天后仅有10%的沉降、分层现象。     

Gender differences in publication productivity in psychology in India

An analysis of gender differences in psychology in India provides quantitative and qualitative assessment of R&D output contributed by psychologists with the indication of the trend of growth, skewness, relatedness, co-authorship pattern of productivity.     

Metrology in Chemistry in Germany

The system for Metrology in Chemistry in Germany is described. At the national standards level, a network of high-level chemistry institutes coordinated by the national metrology institute, PTB, provides the primary references for chemical measurements. A dissemination mechanism employs chemical calibration laboratories accredited within the framework of the German Calibration Service (DKD). They act as “multipliers” between the national standards level and the user level by providing the user with calibration means which are traceable to the SI via national standards. Traceability structures in clinical chemistry, electrochemistry, elemental analysis and gas analysis are described     

Natural radioactivity in drinking water in private wells in Finland

Natural radioactivity in drinking water was determined in population-based random study of 472 private wells. The mean concentrations of (222)Rn, (226)Ra, (234)U, (238)U, (210)Pb and (210)Po in drilled wells were 460, 0.05, 0.35, 0.26, 0.04 and 0.05 Bq l(-1), and in wells dug in the soil were 50, 0.016, 0.02, 0.015, 0.013 and 0.007 Bq l(-1), respectively. Approximately 10% of the drilled wells exceeded a radon concentration of 1000 Bq l(-1) and 18% a uranium concentration of 15 microg l(-1). The mean annual effective dose from natural radionuclides for a drilled well user was 0.4 mSv and 0.05 mSv for a user of a well dug in the soil. The effective dose arising from (222)Rn was 75% of the total of all natural radionuclides for drilled well users. As regards long-lived radionuclides, (210)Po and (210)Pb caused the largest portion of the effective dose. The dose arising from (238)U, (234)U and (226)Ra was only 8% of the total of all natural radionuclides.     

Natural radioactivity in drinking water in private wells in Finland

Radiation Protection Dosimetry     

Optische in situ Schichtdickenmessung in Bedampfungsanlagen. Optical in situ film thickness monitoring in coating systems

Optical film thickness monitoring is more precise than crystal monitoring. The optical measurement makes use of the fact that the intensity of a monochromatic light beam which is reflected on a film will change periodically with increasing film thickness. The measurement is performed at an exchangeable test glass that is positioned beside the substrates and is therefore coated in the same way as the substrates. The accuracy of cut‐off is achieved by a “fit” of a theoretical curve shape to the measured values. Order filters are used to ensure that, at a certain wavelength, higher deflection orders do not influence the measurement when a monochromator grating is used.     

Differences in coagulation in clotting of vascular access in hemodialysis patients

Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F₁₊₂) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F₁₊₂ levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis.     

Spanish experience in education and training in radiation protection in medicine

In most of its publications, the International Commission on Radiological Protection has highlighted the importance of education and training in radiation protection (RP) for medical exposures. Spain, like other Member States of the European Union, has implemented the Directive and the Guidelines in the medical area. The purpose of this paper is to present the Spanish experience in RP education and training in medicine, the different objectives established according to professional levels, existing regulations and feedback obtained from various RP actions.