离子交换树脂法制备高纯超细氢氧化镁

以强碱性阴离子树脂作为沉淀剂,采用离子交换法制备了高纯超细的氢氧化镁粉体,就离子交换反应过程中的反应温度、反应时间、MgCl2浓度等条件对Mg（OH）2粒径的影响进行了探讨,并利用扫描电镜、微机差热天平、X射线衍射仪对产物进行了表征,实验结果表明,在氯化镁溶液浓度为0．1mol／l,反应温度为60℃,反应时间为16h的条件下可制备出形貌规则、分散性较好的六方片状氢氧化镁,平均粒径可达到100nm左右。     

纳米氢氧化镁粉体的制备及热分解动力学研究

以氯化镁和尿素为原料,采用均匀沉淀法制备出厚度约为20 nm的片状纳米氢氧化镁粉体。利用热重分析法对片状纳米氢氧化镁粉体在不同升温速率下的热分解动力学进行研究,以期深入认识由纳米氢氧化镁粉体热分解得到纳米氧化镁粉体过程的物理化学本质。分别采用Coats-Redfern方程和Dolye方程,对热重分析数据进行了处理和拟合,得到了片状纳米氢氧化镁粉体热分解反应属于Avrami-Erofeev(n=1)的成核和生长为控制步骤的反应机理,其表观活化能E=131 kJ/mol,指前因子A=1.56×1010。     

氢氧化铝镁复合材料的研制

本文研究了两种制备氢氧化铝镁复合材料的方法：一种是采用氯化镁溶液与氢氧化钠溶液进行中和反应,制取氢氧化镁,然后以氢氧化镁料浆为种子,加入铝酸钠溶液中进行晶种分解得到产品;另一种是将硝酸铝和氯化镁按一定比例配制成混合溶液,再缓慢加入氢氧化钠溶液作为沉淀剂制取产品。经过检测,两种方法均可制备得到纯相的氢氧化铝镁复合材料。     

MgCl_2添加方式对Mg(OH)_2形貌及粒度分布的影响

氢氧化镁作为一种无卤阻燃剂,在聚合物阻燃领域具有重要的前景。采用反向沉淀法制得纳米级氢氧化镁粉体,研究了氯化镁添加方式对氢氧化镁粒度分布及团聚状态的影响,并通过热红外联用技术对其热解规律进行了分析。实验结果表明,氯化镁添加方式对氢氧化镁粒度分布及团聚状态有显著的影响;分4次加入氯化镁溶液所得氢氧化镁的粒度分布最均匀,小粒子所占的比例最大,不容易发生团聚现象。     

片状纳米级氢氧化镁粉的制备工艺与分散机理研究

氢氧化镁粉的超细化和高分散性是充分发挥其在聚合物材料中的阻燃性的前提。对片状纳米氢氧化镁粉的制备工艺以及几种表面活性剂的种类、用量对纳米氢氧化镁粉的分散性的影响进行了研究，并通过扫描电子显微镜（SEM）、红外光谱（FTIR）对其进行了表征。研究结果表明，制备片状纳米氢氧化镁的最优工艺条件是：镁液中Mg^2＋的初始浓度为22．75g／L，沉淀剂用20％的NaOH溶液，反应温度为50℃，反应时间为5min。SEM分析表明：在此条件下制得的片状纳米级氢氧化镁粉片径100nm左右，厚10nm左右，但是颗粒之间团聚严重，团聚颗粒达到微米级。使用硅烷FR-693、钛酸酯YB-502和聚乙二醇对氢氧化镁进行原位改性可以提高其分散性。硅烷FR-693、钛酸酯YB-502和聚乙二醇的最佳用量分别为氢氧化镁质量的1．5％，1．5％，0．75％。FTIR分析表明，3种改性剂都可以吸附在氢氧化镁颗粒表面并形成化学吸附。其中硅烷FR-693与粉体表面形成Si-O-Mg化学键合，钛酸酯YB-502与粉体表面形成Ti-O-Mg键合。     

针状纳米氢氧化镁的形貌控制

以氯化镁和氢氧化钠为反应物，添加表面活性剂十二烷基苯磺酸钠（SDBS），在水溶液中利用反向沉淀法制备针状纳米氢氧化镁粉体，其直径为9～12nm，长度为40～110nm。并应用X射线粉末衍射仪（XRD）、场发射扫描电子显微镜（FESEM）、高分辨透射电子显微镜（HRTEM）对所制备粉体的晶型结构、粒度、形貌进行表征。同时讨论了表面活性剂／分散剂对纳米氢氧化镁粉体形貌的影响。     

丙烯酸改性氢氧化镁晶须的制备及研究

以MgCl2·6H2O为原料,氨水和氢氧化钠为混合沉淀剂,丙烯酸为表面改性剂,制备了高纯度的纤维状纳米氢氧化镁晶须.研究了丙烯酸的加入量,反应温度及氢氧化钠溶液的浓度对产物分散性、结晶及产率的影响,同时对产物进行SEM,TEM以及XRD分析.结果表明:控制氯化镁浓度为2mol/L,氢氧化钠溶液的浓度为2.2mol/L,丙烯酸的添加量为3%(质量分数),反应温度为10℃,在此条件下,制备出了长度在50～150nm,直径在8～15nm的高纯纳米氢氧化镁晶须.     

变温结晶法制备高分散性纳米氢氧化镁

以轻烧粉与氯化铵反应得到的精制氯化镁溶液为原料,氨气为沉淀剂,通过改变反应温度控制反应体系过饱和度,变温反应制备出高分散纳米氢氧化镁,并利用扫描电镜(SEM)、X射线衍射(XRD)和激光粒度分布仪对产品进行了表征。实验研究了变温反应与恒温反应产品形貌和粒径的区别,结合液相体系中OH-浓度随反应温度的变化过程,分析讨论了变温法制备高分散纳米氢氧化镁的机理。     

立方纳米氧化镁的制备及形貌表征

利用直接沉淀法得到片状氢氧化镁前驱体,再结合煅烧法得到立方纳米氧化镁;为优化实验条件,讨论氢氧化镁前驱体及氧化镁的形貌影响因素。实验结果表明:当氢氧化钠的物质的量浓度为0. 5 mol/L、镁盐物质的量浓度为0. 4 mol/L时,可得到分散性较好的片状氢氧化镁前驱体;当氯化镁的纯度较高时,氢氧化镁结晶度进一步提高,呈现出分散均匀的花瓣状薄片形貌;煅烧温度控制在1 150℃时,所得到的立方纳米氧化镁分散性较好。     

球形氢氧化镁的制备及其晶体生长动力学

制备花状球形氢氧化镁粉体,研究了几种关键因素对镁回收率的影响和氢氧化镁的晶体生长动力学.结果表明,随着反应溶液中Mg~(2 )初始浓度和pH值的提高,镁的回收率提高;提高反应温度使镁的回收率提高,但当温度超过60℃后,反应溶液中氨的大量挥发使其pH值迅速降低,因而镁回收率下降;陈化可以提高镁的回收率,当陈化时间超过60 min后因镁已完全沉淀,回收率不再提高.在最佳工艺条件下用氨法制备的氢氧化镁颗粒为花状球形,形状规则,分散性好,粒度均匀,粒径约2μm,单片厚度约30 nm.晶体生长动力学研究表明,析出Mg(OH)_2晶体的质量和Mg(OH)_2晶粒平均粒径随着时间呈指数增长.     

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.     

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.     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from