文石型碳酸钙晶须的制备研究

采用碳酸化法在MgCl2-Ca(OH)2-CO2体系中合成了文石型碳酸钙晶须,研究了碳酸钙晶须的成型原因,分析了pH值、氢氧化钙的纯度对晶须生长的影响,运用SEM和XRD对晶须的形貌和组成进行了表征.结果表明:Mg(OH)2沉淀促使文石相碳酸钙异相成核,取向生长成针状;控制pH值不超过8.5,可以连续添加精制石灰水合成碳酸钙晶须.     

NaAl(OH)2CO3阻燃晶须的水热合成及其阻燃性能

以异丙醇铝和NaHCO3为原料,采用水热法制备了片钠铝石(NaAl(OH)2CO3)晶须,通过XRD、SEM对不同水热条件下合成产物的物相和形貌进行了表征.结果表明,制备的NaAl(OH)2CO3晶须长度为10～20μm,长径比为20～40;初始反应体系的pH值、反应物Na/Al摩尔比、反应温度和反应时间对产物的生长、形貌及尺寸分布有显著影响.添加40%(质量分数)NaAl(OH)2CO3晶须的阻燃EVA,极限氧指数为33.5,垂直燃烧达FV-1,说明NaAl(OH)2CO3晶须具有良好的阻燃性能.     

碱式硫酸镁晶须的制备表征及应用研究

首先以制盐母液和氨水为原料制备出氢氧化镁滤饼,再以硫酸镁和自制的氢氧化镁为原料,通过水热合成法制备出碱式硫酸镁晶须。实验确定了制备碱式硫酸镁晶须的适宜条件∶n(Mg(OH)2)∶n(MgSO4)=1:4,反应时间为4h,反应温度为190℃,硫酸镁溶液的浓度为0.3mol/L。对碱式硫酸镁晶须进行组成分析、SEM、XRD及TG-DTG分析,制备的晶须为扇状,直径为1～2μm,长度为200～300μm.长径比为150～250。合成的碱式硫酸镁晶须组成为MgSO4.5Mg(OH)2.2H2O。在聚丙烯中加入碱式硫酸镁晶须后,有明显的阻燃性能。     

氨沉淀法一步水热合成碱式硫酸镁晶须研究

采用氨作为沉淀剂一步法水热合成碱式硫酸镁(MHSH)晶须,利用扫描电子显微镜(SEM)、X射线衍射分析仪(XRD)、差热-热重分析仪(TG-DTG)对产品进行了表征。在硫酸镁溶液浓度2mol/L、NMgSO4∶NNH3=1∶0.5、反应温度为120℃、反应时间2h、搅拌强度200r/min的条件下合成的碱式硫酸镁晶须化学式为MgSO4·5Mg(OH)2·2H2O,平均直径为0.2~0.3μm,长径比30以上,晶须表面光滑,纤细均匀且无弯曲。     

水热法制备菜花状氧化锌

以Zn(NO3)2.6H2O和N2H4.H2O为原料,采用水热法在180℃制备了菜花状的氧化锌(ZnO)纳米棒束、不规则的长短棒晶须体以及柱状晶须束。用XRD、SEM、FE-SEM及HR-TEM对样品进行了表征。具有六方纤维锌矿结构的ZnO棒或柱的直径分别在100、200nm和1μm左右。以负离子配位多面体生长基元理论讨论了ZnO晶体的生长过程及N2H4.H2O浓度对ZnO形貌的影响。     

PMMA包覆纳米氢氧化镁晶须的制备及研究

初步探索了甲基丙烯酸甲脂(MMA)与AA-Mg(OH)2的聚合反应过程,研究了AA-Mg(OH)2、MMA的用量对乳液聚合反应中单体转化率的影响。运用红外光谱、扫描电镜、透射电镜对AA-Mg(OH)2和PMMA/AA-Mg(OH)2进行了表征,结果表明:MMA与AA-Mg(OH)2晶须表面发生了化学反应,形成了具有核壳结构的聚甲基丙烯酸甲酯包覆纳米氢氧化镁晶须复合材料,产物的粒径为100~500nm,聚合反应后复合粒子的形貌为球状。     

ZnO晶须增强树脂基复合材料研究

对ZnO晶须／NR复合材料的实验研究表明,表面改性后的ZnO晶须对NR具有显著的增强和抗老化作用,其增强效果沿橡胶混炼剪切方向与垂直剪切方向几乎相同。对ZnO晶须／PPS复合体系的研究结果表明,偶联剂表面处理后的ZnO晶须对PPS有显著的增强作用。研究发现,经典的预测复合材料强度的理论公式可以较好地预测ZnO晶须／NR体系,但对ZnO晶须／PPS复合材料的预测则与实测值存在较大差异。分析认为其主要原因是该晶须特殊的空间四针状结构能有效地传递受力．尖端作用避免了端口应力集中引起的破坏。     

氧化锌晶须／聚苯胺核壳结构复合物的制备与性能研究

对氧化锌晶须(ZnOw)进行正硅酸乙酯(TEOS)和γ-氨丙基三乙氧基硅烷(APTES)改性后得到共改性氧化锌晶须(TA-ZnOw),在其表面进行聚苯胺(PANi)接枝聚合,制备了TA-ZnOw/PANi复合物.将其与只经APTES改性的氧化锌晶须(A-ZnOw)和聚苯胺复合而成的A-ZnOw/PANi复合物,及未经任何改性的氧化锌晶须(N-ZnOw)和聚苯胺合成的N-ZnOw/PANi复合物进行形貌、结构及性能比较.结果表明,TA-ZnOw/PANi复合物中的聚苯胺接枝效果最好,而且接枝在TA-ZnOw表面的聚苯胺结构与纯聚苯胺结构相同.且TA-ZnOw/PANi核壳结构复合物表现出最好的介电性能和热稳定性能,介电常数虚部最大值为6.86,壳层聚苯胺热分解温度为350℃.TEOS作为保护层,APTES作为自组装层,在制备TA-ZnOw/PANi核壳结构复合物过程中起了重要作用.     

乙醇/水混合溶剂中一维ZnO晶须的制备与表征

以乙醇/水作溶剂,氯化锌(ZnCl2)和氢氧化钠(NaOH)为原料,采用简单的低温陈化法制备出不同长径比的一维(1-D)ZnO晶须.用X射线衍射仪(XRD),扫描电子显微镜(SEM)及高分辨透射电镜(HRTEM)等分别对晶须的形貌和结构进行表征.考察了乙醇与水的体积比对晶须粒径及长径比的影响,结果表明,随混合溶剂中乙醇含量升高,晶须粒径逐渐减小.同时,从晶体生长的角度对乙醇影响氧化锌晶体生长的作用机理进行了初步探讨,认为乙醇通过"表面-溶剂作用"吸附在ZnO晶体表面,使其各晶面的生长速率受到不同程度的抑制,从而达到减小晶须粒径的目的.     

氧化锌晶须(ZnOW)水泥基复合材料微波吸收特性研究

研究了氧化锌晶须(ZnOw)水泥基复合材料的材料制备,测试了试件在微波3mm,8mm,3cm等波段的微波吸收特性.研究结果表明,氧化锌晶须(ZnOw)能够有效调整水泥基复合材料的介电常数,改变反射及透射特性,但本身对微波的吸收并不明显,甚至还降低了常规混凝土的透射衰减性能.该结论对澄清氧化锌晶须(ZnOw)的微波吸收应用前景猜测有实际意义.     

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.……     

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.     

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...     

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.……     

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.     

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.     

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 ...