碳管长径比对MWNTs/PI复合薄膜介电性能的影响

采用混酸氧化法处理多壁碳纳米管(MWNTs),在不同处理时间下得到不同长径比的碳纳米管,并通过扫描电镜(SEM)对碳纳米管的形貌进行观察。以不同长径比的碳纳米管掺杂改性MWNTs/PI复合薄膜。运用体积排斥理论和渗滤理论预测分析了碳纳米管长径比对MWNTs/PI复合薄膜渗流阈值和介电常数的影响,并实测了MWNTs/PI复合薄膜的渗流阈值和介电常数,分析了理论预测与实测结果差异的原因。     

碳纳米管/石墨烯杂化材料改性环氧树脂力学性能研究

通过超声离心将酸化石墨烯和羟基化的多壁碳纳米管按照不同比例成功合成碳纳米管/石墨烯杂化材料。将杂化材料分散在环氧树脂体系中制备环氧树脂复合材料样条,研究杂化材料对环氧树脂力学性能的影响。通过扫描电镜(SEM)、透射电镜(TEM)和拉伸力学性能测试分析了杂化材料的分散性等微观结构以及环氧树脂复合材料的力学性能及断面形貌。碳纳米管/石墨烯杂化材料对环氧树脂有增强增韧的效果,其中石墨烯与碳纳米管之比为2∶1的杂化材料对环氧树脂的增强增韧效果最好。     

PVA/LDH-aCNTs杂化薄膜的制备及其性能研究

采用恒定p H共沉淀法合成了层状双羟基氢氧化物(LDHs)和酸化碳纳米管(aCNTs)杂化材料,并将其作为填料应用到聚乙烯醇(PVA)薄膜中制备了PVA杂化薄膜。采用X射线衍射仪、拉曼光谱仪、扫描电子显微镜等对合成的LDH-aCNTs杂化材料进行了表征,并对PVA杂化薄膜进行了微观结构和力学性能测试。力学性能测试结果表明:当LDH-aCNTs的添加质量分数为3%时,PVA杂化薄膜的拉伸强度达到最大值,相比于纯PVA,拉伸强度约提高了41%。LDHs的存在有效地改善了aCNTs和PVA之间的相容性,使得PVA/LDH-aCNTs杂化薄膜具有较优异的力学性能。吸水性能测试结果表明:相比于纯PVA(吸水率为649%),添加质量分数为5%的PVA/LDH-aCNTs杂化薄膜的吸水率约下降了58%。LDH-aCNTs杂化纳米粒子中的含氧官能团能与PVA链中的羟基形成氢键,使裸露的亲水基团减少,吸水率下降。PVA/LDH-aCNTs杂化薄膜的力学性能和耐水性能的提高,有望拓宽PVA基复合薄膜的应用范围。     

多壁碳纳米管-还原氧化石墨烯杂化薄膜导电性能的调控

以氧化石墨烯(Graphene oxide,GO)水溶胶作溶剂和表面活性剂,将不同质量分数的多壁碳纳米管(Multi-walled carbon nanotubes,MWCNTs),通过超声空化作用分散于其中得到稳定均质的多壁纳米管/氧化石墨烯(MWCNT-GO)悬浮液。采用微滤自组装法制备MWCNT-GO杂化薄膜,然后将其置于真空干燥箱中进行低温(200℃)热处理1 h以脱除GO中的大部分含氧官能团,即得部分还原的多壁碳纳米管-还原石墨烯(MWCNT-RGO)杂化薄膜。结果表明:MWCNT-GO杂化薄膜呈现均质层状的"三明治"式结构,MWCNTs与GO形成3D交联导电网络,通过控制MWCNTs的添加量和低温热处理,可实现氧化石墨烯导电性的恢复和有效调控。随着MWCNTs含量的增加,所得MWCNT-GO杂化薄膜的导电率增加。掺杂质量分数50%的MWCNTs所制MWC-NT-GO-50杂化薄膜的导电率为1 120 S/m,经200℃热处理后,导电率高达5 380 S/m。     

碳纳米杂化材料的制备及其对环氧树脂性能的影响

通过超声处理和离心酸化石墨烯与多壁碳纳米管制备出碳纳米管/石墨烯杂化材料。通过紫外光谱表征杂化材料结构的变化。通过将不同填料(杂化材料、石墨烯、碳纳米管)加入环氧树脂体系制备复合材料样条,对样条进行拉伸测试,并通过扫描电镜观察样条断面的微观形态。结果表明:当杂化材料的添加量为0.3%(质量分数)时,复合材料的力学性能最好。根据结果可初步推断出杂化材料增强增韧环氧树脂的可能机理:(1)杂化材料为纳米粒子,纳米粒子在界面上与环氧基团形成远大于范德华力的作用力,构成非常理想的界面;(2)杂化材料中石墨烯与碳纳米管通过π-π作用嵌插在一起形成三维立体结构,这种"胡须"状结构可分散和缓冲样条受到的外力作用,外力作用过程中产生微裂纹吸收能量,实现对环氧树脂强度和韧性的改性。     

氧化石墨烯纳米带与氧化石墨烯增强热塑性聚氨酯薄膜的制备及性能

利用纵向裂解多壁碳纳米管制备了氧化石墨烯纳米带,并采用溶液成型的方法制得氧化石墨烯纳米带-氧化石墨烯(GONRs-GO)/热塑性聚氨酯(TPU)复合材料薄膜。场发射扫描电镜和X射线衍射分析结果显示,GONRs与GO间相互剥离并均匀地分散在TPU基体中;氧气透过率(OTR)和力学性能测试表明,GONRs和GO具有协同增强TPU复合材料薄膜的阻隔和力学性能的作用。当GONRs和GO在TPU中添加量均为1.5%(质量分数)时,GONRs-GO/TPU复合材料薄膜的阻隔和力学性能达到最佳。相比于纯TPU薄膜,该GONRs-GO/TPU复合材料薄膜的OTR降低了83.94%,拉伸断裂强度、屈服强度、扯断伸长率则分别提高了59.28%,59.54%和15.0%。     

抗静电碳系/聚酰亚胺复合薄膜的制备及表征

采用氧化石墨烯还原法制备了石墨烯(GR),同时采用混酸酸化法处理多壁碳纳米管(MWCNTs),以1%(wt,质量分数,下同)的GR和不同含量的酸化MWCNTs作为填料,通过超声搅拌分散-原位聚合法制得抗静电碳系/聚酰亚胺(GR-MWCNTs/PI)复合薄膜,并对复合薄膜的抗静电性能、热稳定性和力学性能进行表征。结果表明,2种碳系材料的添加可明显提高薄膜的导电性、机械性能和抗静电的效果,导电填料的添加对薄膜的热稳定性影响不大,在GR含量为1%,MWCNTs含量为2%时,在560℃时失重率约35%,电阻率为4.44×107Ω·cm,拉伸强度达到88.0MPa,断裂伸长率达到16.23%,拉伸强度和断裂伸长率分别比纯聚酰亚胺提高了122.4%和128.6%。     

改性碳纳米管处理碳纤维的效果表征

采用浓硫酸/浓硝酸氧化处理多壁碳纳米管(MWCNTs),再将氧化后的碳纳米管与硅烷偶联剂(KH560)进行接枝,制备了硅烷偶联剂表面化学修饰的MWCNTs。在此基础上,将改性前后的碳纳米管分散在环氧树脂体系中,涂覆处理碳纤维。研究处理前后碳纤维力学性能和界面性能的变化。通过红外光谱(FTIR)和透射电镜(TEM)分析,表明KH560已成功接枝到多壁碳纳米管上;通过分散性实验证明了改性后的碳纳米管分散性提高;对处理后的碳纤维进行力学性能测试,并用扫描电镜(SEM)观察分析断面形态变化,结果表明,当碳纳米管的含量为0.5%时,改性碳纳米管处理的碳纤维拉伸强度和拉伸模量分别提高23.83%和7.11%,界面性能增强。     

PP/碳纳米管复合材料的结构与性能

采用原子转移自由基(ATRP)活性聚合方法在多壁碳纳米管(MWNT)表面接枝丙烯酸丁酯聚合物(PBA),并以此对聚丙烯(PP)进行改性。红外光谱(FT-IR)及透射电子显微镜(TEM)测试结果表明,采用ATRP法成功地将PBA接枝到多壁碳纳米管(MWNT)表面。采用熔融共混法制备了PP/MWNT复合材料,对其力学性能和耐热性能进行了研究,结果表明,接枝聚合物的碳纳米管提高了复合材料的拉伸强度和冲击强度,提高了PP的耐热性。MWNT-PBA和MWNT-COOH加入PP都能提高材料的性能,而MWNT-PBA比MWNT-COOH的作用更加明显。     

碳纳米管改性水泥基注浆材料的制备及性能研究

碳纳米管具有大的比表面积和优异的力学性能,是水泥基注浆材料的优异填料。以普通硅酸盐水泥P.O 42.5为基体材料,多壁碳纳米管为填料,制备了不同碳纳米管掺杂量(0,0.3%,0.6%和0.9%(质量分数))的改性水泥基注浆材料,研究了注浆材料的晶体结构、微观形貌、力学性能和碳化性能。结果表明,掺入碳纳米管后,加速了水化反应,但没有新物质产生,碳纳米管呈短杆状与长杆状均匀分布于水泥基体间,形成“桥联作用”,提高了水泥基体之间的结合力,改善了注浆材料的强度和韧性;随着碳纳米管掺杂量的增加,注浆材料的抗压强度和抗折强度均表现出先升高后轻微降低的趋势,而碳化深度呈现出先降低后升高的趋势;当碳纳米管掺杂量为0.6%(质量分数)时,注浆材料7和28 d的抗压强度达到最大值89.95和97.42 MPa,抗折强度也达到最大值10.92和15.82 MPa,而碳化深度则达到了最低值14.54和26.47 mm。综合分析可知,碳纳米管的最佳掺杂量为0.6%(质量分数)。     

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.