镁合金表面钼酸盐转化膜的制备及其耐蚀性能

钼酸盐毒性低,有良好的缓蚀性能,可代替有毒的铬酸盐用于镁合金表面的耐蚀处理。采用正交试验优选了钼酸盐转化工艺中的Na2MoO4.2H2O浓度、NaH2PO4.2H2O浓度、pH值、成膜温度和时间,考察了压铸AZ91D镁合金在优化工艺条件下所得钼酸盐转化膜的耐蚀性能,利用扫描电子显微镜(SEM)、能谱仪(EDS)和中性盐雾腐蚀试验(NSS)等手段研究了转化膜的组成和形貌。结果显示:钼酸盐转化膜主要由Mg,A l,Mo,P和O等元素构成,膜层较为平整、均匀、致密,并存在一些不规则的微裂纹;钼酸盐转化膜有效地提高了AZ91D镁合金的耐蚀能力。     

AZ91D镁合金表面植酸转化处理

为了进一步优化镬合金表面植酸转化膜的性能,通过正交试验获得了最优工艺,制备了耐蚀性优良的转化膜.采用扫描电子显微镜和能谱仪对转化膜的微观形貌和成分进行了分析,通过点滴试验、极化曲线和电阻抗谱对植酸转化膜的耐腐蚀性能进行了研究.结果表明:植酸转化膜主要由Mg,AJ,O,P,C和Na元素组成;膜层可显著改善镁合金基体的耐蚀...     

AZ31B镁合金铈基-植酸复合转化膜研究

为了进一步提高镁合金转化膜防腐性能的影响,将铈基转化复合于在AZ31B镁合金植酸转化膜表面,制备了一种铈基一植酸复合转化膜,应用析氢实验、Tafel分析方法及SEM、EDS对AZ31B镁合金不同转化膜的防腐性能及表面微观结构及成份进行了研究。结果表明复合转化膜表面主要由C、O、P、Ce、Mg及Al元素所组成,复合转化膜相比于植酸转化膜及铈基转化膜具有更好的致密性,从而复合转化膜相比于植酸转化膜及铈基转化膜具有更好的防腐性能。     

不同添加剂对聚偏氟乙烯膜结构和性能的影响

利用非溶剂相转化法(NIPS),以N,N-二甲基乙酰胺(DMAc)为溶剂,聚乙烯吡咯烷酮(PVPK30)和一水合氯化锂(LiCl·H2O)为混合添加剂,改变PVPK30-LiCl·H2O配比得到不同性能和结构的聚偏氟乙烯(PVDF)膜。考察了不同种类添加剂(PVP、LiCl·H2O、H2O和PEG200)及不同配比的PVPK30-LiCl·H2O添加剂对PVDF成膜分相延时时间、分相速率的影响。实验结果表明,采用PVPK30为添加剂,铸膜液呈瞬时分相行为,膜通量很大;增大混合添加剂中PVPK30/LiCl·H2O的比例,会增加液液分相速率,使膜结构中的大孔贯通整个膜结构。     

镁合金化学转化膜的耐腐蚀性研究

在50g/L KMnO4和100g/L Na3PO4组成的基础化学转化溶液中添加6 g/L缓蚀剂,在AZ31镁合金上获得了化学转化膜.用植酸作为转化处理液,分析了pH值、温度、转化时间及植酸用量(质量分数)对AZ31合金成膜及耐蚀性的影响,SEM观察表明,植酸膜经3.5%的NaCl溶液浸蚀后有一定的自愈合能力.这两种方法获得的转化膜均比铬酸膜光滑、致密均匀.     

镁合金微弧氧化添加剂的优选

为了获得耐蚀性更优的微弧氧化膜,以NaAlO2-NaOH体系为基础氧化液,考察了EDTA、蒙脱石、阿拉伯树胶等添加剂对AZ91D镁合金微弧氧化膜层耐蚀性能的影响.在3.5%的NaCl水溶液中测定了微弧氧化处理前后镁合金样品的动电位极化曲线,利用腐蚀电阻等参数来判定膜的耐蚀性能.确定了铝酸盐体系中添加剂的最优用量为:3 g/L蒙脱石,0 g/L EDTA,50 mL/L 5%阿拉伯树胶.利用SEM,EDS和XRD等初步研究了陶瓷膜表面的微观结构及成分.结果表明:在该体系中添加最佳用量的添加剂可以得到致密的微弧氧化膜,膜层主要由MgO以及MgAl2O4组成;微弧氧化处理后的镁合金比处理前具有更好的耐蚀性能.     

AZ31镁合金钕基转化膜工艺与耐蚀性能研究

研究了AZ31镁合金钕基转化膜的制备工艺,并对膜层形貌、化学组成和耐腐蚀性能进行了分析。通过正交优化得到了钕基转化膜的4个工艺条件的最佳水平组合为Nd(NO3)3浓度为5g/L,H2O2浓度为5mL/L,成膜时间9min,成膜温度40℃。结果表明,采用最佳工艺得到的钕基转化膜层均匀且致密,其主要成分是Nd2O3和少量MgO。通过动电位极化曲线和析氢实验研究了钕基转化膜层对AZ31镁合金在3.5%(质量分数)NaCl溶液中耐蚀性能的影响,结果表明,钕基转化膜可以大大降低AZ31镁合金的腐蚀速率,当Nd(NO3)3浓度为5g/L时,钕基转化膜的腐蚀电流密度最小,耐腐蚀性能最好。     

镁合金汽车轮毂表面转化膜的致密化与耐蚀性能研究

为了在镁合金汽车轮毂表面制备成本低、环保和耐腐蚀的转化膜,以提升其耐蚀性能,采用扫描电镜、能谱分析仪和电化学工作站等研究了后续致密化处理温度和时间对Mg-5.2Al-0.5Mn-1.8Ca合金表面铈转化膜形貌和电化学性能的影响.结果 表明:转化膜经磷酸盐致密化处理后其腐蚀电位正移、腐蚀电流密度减小、极化电阻增大,转化膜的耐腐蚀性能得到增强,且致密化温度为85℃时转化膜的耐腐蚀性能最好;随着致密化时间的延长,转化膜的腐蚀电位呈现先正向移动后负向移动特征,腐蚀电流密度先减小后增大,极化电阻先增大后减小,在致密化时间为60s时,转化膜的腐蚀电位最正、腐蚀电流密度最小、极化电阻最大,具有最佳的耐蚀性能.致密化处理前的原始转化膜的耐腐蚀性能主要与表面裂纹和转化膜结构有关,致密化处理后其耐腐蚀性能主要与新形成的致密CePO4膜层有关;在致密化温度为85℃、致密化时间60 s时,镁合金表面转化膜具有最佳的耐蚀性能.     

高锰酸盐转化处理对医用AZ31B镁合金体外耐蚀性能的影响

现有的医用镁及镁合金在植入人体后耐蚀性能较差。采用高锰酸盐在医用AZ31B镁合金表面制备氧化锰转化膜,并采用SEM、XRD、电化学测试及浸泡试验研究其性能,对膜的形貌、组分、电化学性能和耐体液腐蚀性能进行了探讨。结果表明:氧化锰转化膜均匀分布在AZ31B镁合金表面,无规则分布有微裂纹,膜厚约52~165μm;转化膜的主要成分包括MgO,MnO,MnO2,Mn2O3和Mn3O4;转化膜能够有效改善AZ31B镁合金的体外耐蚀性能。     

环保型AZ31镁合金微弧阳极氧化工艺的研究

为了提高AZ31镁合金的耐蚀性,采用微弧阳极氧化技术并通过正交试验法开发出一种环保型的镁合金微弧氧化工艺.电解液最佳配方为:50.0g/L NaOH,20.0g/L H3BO3,10.0tg/L Na2B4O7·10H2O和10.0 g/L C6H5O7Na3,处理工艺为50 Hz、120 V交流电压氧化5 min.结果表明,经本工艺处理的镁合金表面覆盖一层主要由MgO组成的氧化膜,其自腐蚀电位和自腐蚀电流密度都有较大改善,能为AZ31镁合金基体提供更有效的保护.     

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.