共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
3.
在氨基乙酸和分散剂CTAB存在的情况下,以柠檬酸-水合肼溶液还原前驱体氧化亚铜制备片状结晶铜粉。本文着重考察了还原溶液pH值、CTAB/Cu、氨基乙酸/Cu以及反应温度对片状铜粉的影响。结果表明,分散剂CTAB的加入以及合适的pH值是形成片状铜粉的关键因素;当pH在6、5—9.0,所获得的铜粉中片状颗粒含量随pH升高而降低;获得高含量的片状铜粉的条件为:pH值为6.5,nCTAB/Ca=0.05,n氨基乙酸/Ca=0.1,反应温度控制在55℃~65℃时,所制得的铜粉为发育良好的结晶粉体,表面平整,呈三角、六边形薄片状,其最大投射面的长度为1.0—6.31μm、厚度为0.1~0.3μm。 相似文献
4.
5.
6.
为优化钯纳米颗粒的化学还原法制备工艺,本文以氯钯酸(H2PdCl4)为前驱体,抗坏血酸(C6H8O6)为还原剂,聚丙烯酸钠(PAAS)为表面活性剂制备钯纳米颗粒。采用正交实验探究不同工艺参数对钯纳米颗粒粒径和形貌的影响。通过 X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)及电化学工作站对制备产物的结构、物相、形貌、电催化性能进行了表征。结果表明:在相同的工艺体系下,通过温度的改变,40 ℃条件下可以得到粒径大小为64.5 nm,球形度较好,分散性高的钯纳米颗粒;90 ℃条件下可以得到粒径大小为45.9 nm的立方体钯纳米颗粒。所制备的球形和立方体钯纳米颗粒对甲酸的电氧化催化活性分别为商业钯黑的1.57倍和1.49倍,在催化剂制备领域有广泛的应用前景。 相似文献
7.
硫酸铵低温焙烧中低品位氧化锌矿 总被引:2,自引:0,他引:2
以中低品位氧化锌矿为原料、硫酸铵为反应介质,通过低温焙烧得到热料,研究了焙烧温度对Zn提取率的影响。结果表明,培烧温度为450℃时锌的提取率最高,为91.8%。焙烧温度低反应不充分;焙烧温度过高H2SO4分解挥发,降低反应率。将熟料溶出过滤得到硫酸锌溶液,经净化除杂得到洁净的硫酸锌溶液。以硫酸锌溶液为原料、碳酸铵为沉淀剂,采用沉淀法制备出碱式碳酸锌前驱体,将其煅烧制备了微细氧化锌粉体。采用XRD、SEM及化学成分分析等手段对前驱体和氧化锌粉体进行了表征。结果表明,溶液中OH-、HCO3-与Zn2+共同作用得到前驱体,前驱体受热脱水、分解得到ZnO粉体。碱式碳酸锌前驱体为Zn4(CO3)(OH)6·H2O,呈类球形颗粒团聚体,氧化锌粉体为六方铅锌矿结构,颗粒呈球形,分散性良好。 相似文献
8.
以氨水为络合剂,NaOH为沉淀剂,通过共沉淀制备了高致密、粒度均匀的球形前驱体Ni0.8Co0.1Mn0.1(OH)2.通过焙烧该前驱体和LiOH.H2O的混合物制备出球形锂离子电池正极材料LiNi0.8Co0.1Mn0.1O2.采用XRD、SEM、TEM、TGA/DSC以及恒流充放电测试对材料的结构、形貌和电化学性能进行表征.结果表明,球形前驱体是由纳米级一次颗粒团聚形成,而不是晶粒的长大,且反应时间对前驱体的形貌、粒径分布及振实密度有显著影响.750℃焙烧16 h后的正极材料,保持了完好的球形形貌,具有最佳的层状结构和电化学性能,振实密度最大(2.98 g/cm3),首次放电容量为202.4 mAh/g,倍率性能佳,在3C的放电电流下容量为174.1 mAh/g,且循环性能优良,在40次循环以后,放电容量保持率为92.3%. 相似文献
9.
10.
喷雾干燥-高温热处理两步法制备YAG∶Ce~(3+)荧光粉 总被引:1,自引:0,他引:1
以喷雾干燥-高温热处理两步法,由含聚合铝阳离子的前驱体悬浊液,制得了YAG∶Ce3+荧光粉。用XRD、SEM、荧光光谱等研究了热处理温度、前驱体悬浊液浓度对YAG晶相的形成、粉末颗粒形貌及发光性能的影响。发现前驱体悬浊液浓度由0.03mol/L提高到0.09mol/L时,热处理后所得荧光粉颗粒尺寸增大,并趋近球形;前驱体悬浊液浓度为0.09mol/L,热处理温度从1300℃提高到1500℃时,荧光粉相对亮度提高。YAG∶Ce3+粉末900℃热处理2h可获YAG相;所制备的YAG∶Ce3+荧光粉颗粒无空心,团聚程度低。 相似文献
11.
《International journal for numerical methods in engineering》2018,113(9):1488-1506
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. 相似文献
12.
13.
Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
14.
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. 相似文献
15.
Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
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... 相似文献
16.
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.…… 相似文献
17.
Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe 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. 相似文献
18.
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. 相似文献
19.
C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
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. 相似文献
20.
Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
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 ... 相似文献