碳纳米管表面包覆研究进展

由于碳纳米管特殊的微观结构,使其具有优异的力学、电学和热学性能,是制备高性能CNTs/金属复合材料的理想增强体。然而,CNTs在金属基体中的分散性和润湿性问题严重阻碍了CNTs的应用,但CNTs作为增强体的潜力仍是巨大的。系统的阐述了CNTs表面包覆方法的分类和现状,主要有化学镀、复合电镀、化学气相沉积(CVD)和羰基热分解,并对各种方法利弊作了简要的分析。     

化学镀镍碳纳米管的制备及其电磁学和吸波性能研究

首先对碳纳米管(CNTs)进行纯化、敏化、活化预处理,然后利用化学镀方法在其表面沉积金属镍而制备出镀镍碳纳米管(M-CNTs)。SEM、TEM、EDS、XRD和DSC等综合表征结果表明,通过化学镀工艺,在CNTs表面均匀连续的镀覆了一层厚度约为20nm的非晶态镍镀层,且碳纳米管的分散性得到了改善,更有利于用于复合材料领域。原料碳纳米管和镀镍碳纳米管的电磁学性能的对比研究结果表明,M-CNTs的电导率较CNTs有所降低,这也间接反映了镍镀层在CNTs表面的形成;在4～18GHz内,M-CNTs的ε′、ε″、μ和μ″4个电磁参数均较CNTs均有所增加。在此基础上,进一步以M-CNTs为吸波剂,聚氨酯(PU)为粘结剂,制备了PU/M-CNTs吸波涂料,对其吸波性能的研究结果表明,PU/M-CNTs吸波涂料的吸波效果明显受涂层厚度影响,在1.0～2.0mm的范围内,随着涂层厚度的逐渐增大,其吸收峰逐渐向低频移动,且低频段的吸波效果得以加强,高频段的吸波效果有所减弱。     

等离子喷涂CNTs/Al2O3复合涂层力学性能研究

通过等离子喷涂工艺制备了不同碳纳米管含量的CNTs/Al2O3复合涂层,系统研究了碳纳米管含量对涂层孔隙率、洛氏硬度和断裂韧性的影响规律。实验结果表明:采用喷雾干燥工艺制备的CNTs/Al2O3颗粒为球形,CNTs均匀分布在团聚颗粒的表面;部分CNTs经等离子喷涂后保留在沉积涂层内部并且与Al2O3基体形成冶金结合,起到一定桥接作用。涂层孔隙率和洛氏硬度值均随CNTs含量的增加呈现降低的趋势。随CNTs含量从6%(质量分数)增加到12%(质量分数),CNTs增韧效果的增强和涂层孔隙率的降低导致涂层断裂韧性值从48MPa增加到90MPa。     

电泳沉积制备BG／BG—FHA复合涂层

采用电泳沉积在Ti6A14V钛合金表面制备了以生物玻璃（BG）为中间层,BG与氟取代磷灰石（FHA）复合粉末为表层的BG／BG—FHA涂层。通过XRD、SEM、EDS和电子万能力学试验机对BG／BG—FHA复合涂层的物相结构、微观形貌和涂层结合力进行了分析,优化了涂层的热处理制度,并通过模拟体液浸泡实验研究了涂层的体外...     

电沉积法制备碳纳米管/黑镍复合涂层的光学与结构特性

利用复合电沉积的方法在钛合金基体上成功制备出具有优异光学性能的碳纳米管／黑镍复合涂层, 并研究了复合涂层的微观形貌、光学性能以及镀液中碳纳米管浓度和电镀电流密度对光学性能的影响。实验结果表明: 相较于传统电镀方法获得的单一黑镍涂层, 复合涂层的晶粒尺寸明显减小, 形成多孔结构, 表面粗糙程度明显增加。复合涂层对300~2300 nm范围内的入射光吸收率达到98%左右, 在2.5~20 μm范围内的红外吸收率达到94%, 远远高于传统单一黑镍涂层。复合涂层的太阳吸收比会随着镀液中碳纳米管浓度与电镀电流密度的增加呈先增大后减小的变化规律。     

碳纳米管化学镀镍及镍层形貌控制研究

利用胶体钯溶液对碳纳米管(CNTs)进行活化处理,再采用化学镀的方法在碳纳米管表面沉积金属镍镀层,得到镀镍碳纳米管(Ni/CNTs)。通过场发射扫描电子显微镜(FESEM)、能量色散谱(EDS)、X射线衍射(XRD)和分光光度法对Ni/CNTs和镀液进行表征,分析了镍镀层形成的热力学条件与过程。结果表明:CNTs化学镀镍层为非晶态；CNTs浓度及反应温度对Ni²⁺沉积速率无明显影响；NaOH和NaH₂PO₂浓度与Ni²⁺沉积速率呈线性关系；镍镀层生长符合球形融合模型,通过改变CNTs浓度,可对镀层形貌进行有效调控。     

氧化铁含量对石墨烯/CNTs增强陶瓷涂层性能的影响

为了得到一种性能优异的低温固化复合陶瓷涂层,以石墨烯和多壁碳纳米管(CNTs)为增强相,与氧化铝、氧化锌、氧化锆和氧化铬按一定比例制成骨料,加入催化剂氧化铁,与粘接剂混合充分,手工涂覆于304不锈钢表面制得一种低温固化复合陶瓷涂层.通过示差扫描量热法(DSC)、红外光谱技术(FTIR)、扫描电子显微镜(SEM)以及能谱仪(EDS)对复合陶瓷涂层的热力学参数、表面形貌以及纳米颗粒的分散性进行了表征,研究了不同含量氧化铁对涂层的显微硬度、断裂韧性以及摩擦学性能的影响.结果表明:复合陶瓷涂层制备工艺简单,结构紧密,纳米颗粒的分散性较好;涂层的显微硬度和断裂韧性随着氧化铁含量的增加先增加后减少,当氧化铁含量为3％时,达到最佳;涂层的摩擦系数随着氧化铁含量的增加先增加后减少然后保持不变,当氧化铁含量为4％时涂层摩擦系数最小,摩擦学性能达到最好.     

微弧等离子喷涂碳纳米管/纳米Al2O3-TiO2复合涂层高温性能研究

采用等离子喷涂技术制备了5wt%CNTs/Al2O3-TiO2复合涂层,借助SEM、热红联仪和RAM反射率测试系统对CNTs/Al2O3-TiO2复合涂层的组织结构、高温氧化性能、电磁特性进行了分析.结果表明:CNTs/Al2O3-TiO2复合涂层的组织结构致密、孔隙率低,CNTs分散均匀,碳纳米管与Al2O3-TiO2陶瓷粘结剂之间具有良好的界面相容性.在20～700℃高温氧化过程中,CNTs起始失重温度为471.29℃,CNTs/Al2O3-TiO2复合涂层的高温氧化性能有一定提高,起始失重温度从471.29℃提高到507.8℃,而碳纳米管的失重率从100%下降到33.68%.CNTs/Al2O3-TiO2复合涂层具有较好的高温吸波性能,25℃时复合涂层的反射率峰值为-7.86dB.随温度的升高,CNTs/Al2O3-TiO2复合涂层的反射率峰值不断减小,谐振频率向低频移动,300℃时复合涂层的反射率峰值为-12.88dB,小于-5dB频带宽为4.48GHz.     

水溶液中组装碳纳米管/硫化锌纳米晶复合膜

半导体材料ZnS在光催化领域具有重要的应用前景，如何提高其光催化能力仍是目前关键问题之一。应用碳纳米管的独特结构和性能有望调变和改善ZnS的催化功能。采用一种简便的方法在水溶液中成功组装了硫化锌／碳纳米管纳米晶颗粒（ZnS／CNTs）复合膜。TEM显示纳米复合膜以CNTs组装成席状骨架，ZnS纳米晶填充在CNTs间的缝隙或者包裹在CNTs的表面，二者之间存在良好的接触和相互作用。生成的ZnS纳米颗粒尺寸均匀、大小约为5nm。用EDS、SAED和XRD分析了复合膜的元素组成以及ZnS的晶相结构。结果显示ZnS纳米晶为闪锌矿结构。     

Fe3O4包覆碳纳米管软磁性纳米复合微粒的制备及性能

用水解沉淀法在碳纳米管（CNTs）外包覆Fe3O4，制备了CNTs／Fe3O4纳米复合磁性微粒，借助透射电镜、振动探针式磁强计和外加磁场黏度计对其微观形貌、静态磁性能、沉降稳定性和磁流变性能进行了研究。结果表明：Fe3O4在碳纳米管（直径约20nm）表面形成了紧密的包覆层，微粒呈一维纳米管状结构，平均管径约60nm，平均表观密度为1．8g／cm^3，为传统磁流变液中所用铁粉等软磁性颗粒密度的四分之一。复合微粒的磁滞回线与Fe3O4纳米颗粒较为相似，具有较好的软磁性，其饱和磁感应强度（Bs）为0．21T，矫顽力（以）为7．67kA／m，用该软磁性复合微粒配制的磁流变液具有良好的沉降稳定性和磁流变特性。     

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 ...     

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     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.