水合肼化学还原硫酸铜制备纳米铜粉的研究

为了制备颗粒尺寸在纳米级、大小分布均匀的纳米铜粉,采用水合肼化学还原硫酸铜的方法,并利用扫描电镜(SEM),Image-Pro Plus软件、铜离子浓度测定仪等测方法测量纳米铜粉的颗粒尺寸和铜离子的转化率。结果表明,碱性条件下,水合肼化学还原硫酸铜制备纳米铜粉满足化学反应的热力学和动力性条件;制备纳米铜粉最佳的实验参数,水合肼浓度为1.5 mol/L、CuSO_4·5H_2O的浓度为0.5 mol/L、EDTA和PVP质量比为3∶2(EDTA浓度为30 g/L、PVP浓度为20 g/L)、反应溶液的pH值为12、反应温度为60℃、反应时间为30 min;在此条件下,获得颗粒大小均匀、颗粒尺寸为50.2 nm的纳米铜粉,Cu~(2+)的转化率达到98.2%。     

铜纳米粒子的可控制备及其抗菌性能研究

以氯化铜为铜源,水合肼为还原剂,十六烷基三甲基溴化铵(CTAB)为稳定剂,氨水为络合剂,通过液相还原法合成了纳米铜粉。通过改变还原剂浓度制备了4组不同粒径纳米铜粉末,FESEM等表征发现,随着水合肼浓度的降低,纳米铜粉粒径增加。通过肉汤稀释振荡培养法测试纳米铜的最小抑菌浓度,结果表明,随着纳米铜粒径的增加,抗菌性能降低,所合成纳米铜的最小抑菌浓度在750～3000mg/L;初步分析认为铜纳米粒子主要是通过水解或电离出铜离子而发挥抗菌作用。     

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.     

两步还原法制备MLCC电极用超细铜粉

为了制备MLCC电极用超细铜粉,克服CuSO4直接水合肼还原法制备的铜粉存在粒度分布不均匀、振实密度小的问题,提出了两步液相还原新工艺,即以CuSO4溶液为原料,首先采用NaOH沉淀-葡萄糖预还原制备Cu2O,然后用水合肼还原Cu2O制备超细铜粉.针对实现铜晶体的成核与长大过程的分离,研究了水合肼加入方式对铜粉性能的影响,发现较慢的水合肼滴加速度和将水合肼还原Cu2O阶段分为升温均匀成核与水合肼连续滴加长大两个过程有利于得到粒度均匀的铜粉.在最佳试验条件下制得的铜粉呈类球形,粒度分布均匀,分散性好,平均粒径为1.8μm,振实密度达4.2g/ml.     

超声波辅助液相还原铜氨废液制备纳米铜粉

在超声波场条件下,以电子工业产生的铜氨废液为原料、水合肼为还原剂、聚乙烯吡咯烷酮为表面活性剂还原制备纳米铜粉。研究了该体系下温度、pH值、表面活性剂添加量和超声波场等因素对制备纳米铜粉的形貌和粒径的影响。通过试验探索得到最佳反应温度为:72℃;pH值:9.0~10.0;表面活性剂添加量为:0.2mol·L~(-1)。此外,在超声波场条件下制备的产物粒径小于无超声波场条件下的产物。制备的产物通过X射线衍射(XRD)、扫描电镜(SEM)表征,结果表明产物为纯度很高的铜粉,粒径达到纳米级别,形貌呈球形。在最佳工艺条件下,废液中铜离子的转化率达到97%以上,试验反应产物为氮气,没有引入新的金属离子,反应前后体系成份未变,可以浓缩后返回车间做铜板碱性蚀刻液使用,实现了绿色环保要求。     

微波辅助液相还原法制备超细铜粉

以硫酸铜为原料,水合肼为还原剂,采用微波辅助液相还原法制备了超细铜粉,研究了微波的引入对超细粉体制备的影响,通过XRD、激光粒度分析和TEM表征了粉体的结晶性能、粒度度以及粉体的形貌,研究表明,微波的引入可以明显加速晶化反应的进行,在较短时间内制得的铜纳米晶发育好于传统热处理方式制得的铜纳米晶。     

导电涂料中纳米铜粉抗氧化性的研究

为了提高纳米铜粉的抗氧化能力及其在聚合物基体中的分散性,在钠米铜粉表面包覆一层导电性和抗氧化性均佳的银.以水合肼为还原剂、PVP(聚乙稀吡咯烷酮)和硅烷偶联剂(KH-550)为分散剂,采用二月桂酸二丁基锡对纳米铜颗粒表面进行活化处理,然后采用置换反应法制备得到了与原纳米铜粉粒径和形貌大致相同的核壳型铜-银双金属粉末.采用X射线衍射(XRD)、XRF、TGA等手段分析了核壳铜-银双金属粉的抗氧化性能,并用透射电子显微镜(TEM)对粉末形貌进行表征.结果表明,经表面活化处理后得到的核壳铜-银双金属粉,在镀银质量分数较低(37.68%)时也能形成完全包覆型结构.包覆后的铜纳米颗粒在700℃以下没有任何氧化现象.     

葡萄糖预还原-水合肼液相法制备纳米铜粉

通过单因素条件试验,找出了用葡萄糖预还原-水合肼液相还原法制备纳米铜粉的条件,再通过正交法得到最佳还原条件。试验表明：还原法得到的铜粉纯度高,结构成分更好控制,原料成本低廉,制备出的产品粒度分布窄且粒径小,还原彻底,不易产生CuO和Cu2O等杂质。     

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。     

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。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...