氧化锌/环氧纳米复合材料的制备及其光学性能研究

采用均相沉淀法制备了氧化锌(ZnO)前驱体,通过煅烧前驱体制备了不同粒径的ZnO纳米颗粒,并在此基础上制备了ZnO/环氧纳米复合材料.借助TG、XRD和TEM等手段对纳米ZnO进行了表征,采用UV-VIS研究了ZnO含量、颗粒粒径等因素对复合材料光学性能的影响.研究结果表明:在紫外光区,提高ZnO的含量和选择ZnO最佳粒径,可以改善对紫外光的屏蔽效果;随着ZnO粒径的减小,ZnO对紫外光的屏蔽存在明显的蓝移现象,因此选择合适的粒径尤为重要.在可见光区,ZnO含量和颗粒粒径的影响相似,当ZnO含量低于0.07wt%、粒径小于27nm时复合材料的透过率几乎没有变化,增加含量或增大粒径透过率则随之下降.当ZnO的粒径为27nm时,添加0.07wt%的ZnO所制备的ZnO/环氧纳米复合材料具有优异的光学性能:在保持可见光区高透明性的同时又能够对紫外光区有良好的屏蔽效果,能够满足LED封装等光学器件的需要.     

ZnO/石墨烯纳米复合材料一步水热法制备及电化学性能研究

通过一步水热法成功制得氧化锌(ZnO)/石墨烯(GN)纳米复合材料。测试表明,ZnO/GN复合材料中纤锌矿结构的ZnO纳米棒直径100~200nm,均匀担载在GN网状结构中。ZnO/GN复合材料展现出了优异的电化学性能:在0.1A/g电流密度下的可逆放电比容量达1171mAh/g;0.4A/g充放电循环测试100次后,放电容量仍然维持在305mAh/g。     

ZnO粒径对MC尼龙/纳米ZnO复合材料力学性能的影响

用三种粒径范围的纳米ZnO合成MC尼龙/ZnO复合材料。考察了纳米ZnO的粒径对复合材料力学性能和在复合材料中的分散状况的影响。研究表明,平均粒径为30nm的ZnO合成的MC尼龙/纳米ZnO复合材料中ZnO粒子达到纳米级分散,粒子分布均匀,ZnO对MC尼龙的力学性能提高幅度最大,增强增韧作用非常明显;平均粒径为200nm的纳米ZnO在复合材料中,虽然粒径较大,但分散较均匀,无明显团聚,ZnO对MC尼龙的力学性能也有一定的提高,但提高幅度不大;平均粒径为60nm的ZnO分散难度大,ZnO在复合材料中既有小颗粒的分散,也有大颗粒的团聚体,使材料的力学性能明显不如前两种复合材料。     

针状纳米ZnO制备EP/ZnO复合材料及其力学性能的研究

研究了用热镀锌渣作原料制得的针状纳米ZnO对EP/ZnO复合材料力学性能的影响.结果表明:使用具有空间结构的针状纳米ZnO所制备的环氧树脂复合材料,与普通ZnO所制备的环氧树脂复合材料相比力学性能得到了较大的提高和改善.当纳米ZnO的含量为4％(质量分数)时,材料的力学性能得到了明显改善,其冲击强度提高46.9％,抗拉...     

络合剂对溶胶凝胶制备纳米铜及其催化性能影响

为研究络合剂对纳米铜粉体的制备及其催化性能的影响,分别以柠檬酸、葡萄糖为络合剂,采用溶胶-凝胶法制备纳米铜.考察了两种络合剂对制备过程以及产物结构的影响,通过催化苯氧化合成苯酚的反应考察制得的纳米铜粉的催化性能.研究表明:葡萄糖为络合剂制得的纳米铜(G-Cu)平均粒径较小(30 nm),比表面积为5.203 m2/g,在催化苯制苯酚反应时,具有较高的苯转化率(50.30%),但对苯酚的选择性较差;而柠檬酸为络合剂制得的纳米铜(C-Cu)平均粒径为55 nm,比表面积19.517 m2/g,催化苯转化率为21.95%,选择性为38.46%.此外,通过对溶胶凝胶法制备机理分析可知,在形成的胶体结构中,柠檬酸和葡萄糖中的羧基和羟基分别与铜离子进行配位.     

抗菌天然橡胶纳米复合材料的研制

研究了自制ZnO/Ag纳米复合抗菌剂的亲油改性,利用改性后的ZnO/Ag纳米复合抗菌剂制备天然橡胶(NR)纳米复合材料,探讨了抗菌NR纳米复合材料的抗菌、抗藻性能.结果表明:ZnO/Ag纳米复合抗菌剂经磷酸三丁酯(TBP)改性后,沉降率从接近1减小到0.2以下,亲油性和稳定性大大提高,将TBP改性后的抗菌剂加入到油性介质正己烷中,抗菌剂分散均匀,粒径在100nm以内;在NR纳米复合材料的制备中,随着ZnO/Ag纳米复合抗菌剂添加量的增加,正硫化时间减小;经检测,抗菌NR纳米复合材料对大肠埃希氏菌的抗菌率达98%以上,且抗菌率随抗菌剂添加量的增加而增大,抗藻性能达到最优零级标准.     

ZnO/C复合材料的制备及其光催化性能

以乙酸锌为原料,无水乙醇为溶剂,二乙醇胺为络合剂,采用溶胶-凝胶法制得ZnO溶胶,并经静置、干燥制得凝胶,随后在氧化气氛及N2保护气氛中分别煅烧得到白色ZnO和黑色ZnO/C材料。采用X射线衍射分析仪(XRD)测定试样物相,用化学元素分析仪测定试样中的碳含量,用扫描电镜(SEM)观察试样的显微形貌、用BET氮吸附容量法测定试样的比表面积,用紫外可见漫反射光谱法测定试样在不同光波长范围的吸收,进而计算出ZnO/C的禁带宽度;用亚甲基蓝(MB)溶液为目标物,测定了试样的光催化降解性能。结果表明,在600℃N2气氛下保温5h制得的ZnO/C中的ZnO为六方纤锌矿结构,呈棒状;ZnO/C复合材料含碳量占总质量的8%;比表面积达到24.5m~2/g;该复合材料在模拟太阳光下照射70min可以使MB溶液的脱色率高达98%以上,而ZnO在相同条件下对MB的降解率只有42%。分析表明,ZnO/C材料光催化效果好的主要原因是由于它在还原气氛下煅烧后的能隙为2.96eV,而白色ZnO的能隙为3.35eV。     

模板法制备氧化锌片状晶体

介绍一种制备在001轴方向高度取向生长的纳米片状氧化锌(ZnO)晶体的方法.在一定量的模板剂PEG600存在下,用氢氧化钠溶液调节硫酸锌溶液至一定pH值制得溶胶,然后在180℃下处理此溶胶7h,即可得结晶形态完好的纳米六方片状ZnO.同时讨论了低温近中性水溶液中ZnO晶体在有模板剂存在下的生长习性.     

纳米碳纤维的制备及其表面结构分析

用电场纺丝方法制得了PAN原丝,经碳化制备纳米碳纤维;并用因子设计方法研究PAN原丝平均直径的影响因素;用扫描电镜(SEM)、扫描隧道显微镜(STM)研究了纳米碳纤维的表面形貌及结构.结果表明溶液的浓度是PAN原丝平均直径的主要影响因子,电压对原丝的平均直径没有明显的影响;用电场纺丝方法可以制得直径在80～500nm之间的纳米碳纤维;电场纺丝制得的纳米碳纤维表面有长度约为10nm左右,宽度约为5nm沿纤维方向取向的凹坑,该结构有利于进一步增加纤维的比表面积和吸附性能,该类纤维在复合材料领域有潜在的应用前景.     

核壳纳米复合材料的光催化和抑菌性能研究

通过溶胶-凝胶法制备了银(Ag)@氧化锌(ZnO)纳米复合材料(Ag@ZnO),并采用激光粒度分布仪(DLS)、透射电子显微镜(TEM)、X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis)和热重分析仪(TGA)等仪器设备对制得的样品的形貌、晶型、热稳定性等进行了测试。结果表明:Ag@ZnO纳米复合材料呈现出良好的复合结构,粒径约50nm,具有良好的热稳定性能。研究了Ag@ZnO纳米复合材料对亚甲基蓝的光催化性能和对大肠杆菌等生物细菌的抑制性能。Ag@ZnO纳米复合微粒对亚甲基蓝溶液具有良好的光催化降解性能,降解率达到85%;对大肠杆菌具有很好的抑制性能。     

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 ...