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二氧化钒(VO_2)纳米颗粒具有多种晶型结构,其单斜型半导体M相(VO_2(M))在接近室温时具有完全可逆的相转变性质,相变为四方金红石金属R相,从而引起光学性能的急剧变化,因而VO_2(M)可作为良好的阻热材料应用于控温包装薄膜领域。综述了VO_2(M)纳米颗粒和控温包装薄膜的制备方法,展望了VO_2(M)控温包装薄膜的研究方向。VO_2(M)纳米颗粒的传统制备方法有一步水热法和热分解法等,近年来也出现了新型制备方法,如籽晶诱导法和火焰燃烧法等;控温包装薄膜主要的制备方法为气相法和液相法。根据不同产品的温度需求,通过改变原料种类、温度及掺杂元素等工艺参数调节VO_2(M)纳米颗粒的相变温度,可制备出不同相变温度的VO_2控温包装薄膜。VO_2(M)控温包装薄膜作为一种高新科技产物,可以有效调控商品运输和储藏过程中包装内氛围,具有广阔的应用前景。 相似文献
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VO_2薄膜在中红外激光防护领域有着重要意义。为研究中红外激光辐照VO_2薄膜的温升累积效应及克服中红外激光器功率过小的困难,设计了一种外加热激励源的实验方法。首先利用ANSYS软件对中红外纳秒脉冲激光在不同激励源温度和不同功率密度下辐照VO_2薄膜的温升累积进行仿真,并做了实际验证。研究发现,随着外加激励温度的升高,可在一定时间(100s)内达到VO_2相变温度的激光功率密度逐渐减小,通过增加功率密度,也可以进一步降低相变所需的激励源温度。两者均提高了VO_2薄膜的温升速率。然后在激励源温度为40℃、中红外激光功率密度为1 W/mm~2的条件下研究了中红外纳秒脉冲激光参数对VO_2薄膜的温升累积效应,结果表明,增加激光脉宽、增加重频或光斑半径均能有效增加VO_2薄膜的温升速率。 相似文献
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二氧化钒具有良好的半导体-金属相变特性,在常温下,二氧化钒的晶体结构为单斜晶系结构(M相),随着温度的升高达到相变温度,二氧化钒的晶型变成四方晶红石结构(R相),当温度降低到相变温度时,二氧化钒的晶型又变回单斜晶系结构(M相)。这种典型可逆热色特征,使二氧化钒成为当前建筑用智能窗材料的最佳选择。综述了近些年来制备VO_2薄膜的几种常用方法,并针对VO_2薄膜在热色智能窗应用方面存在的主要问题,从掺杂和复合薄膜结构两方面总结了提高VO_2薄膜性能的改进工艺,为推进VO_2薄膜智能窗的进一步研究提供了依据。 相似文献
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《无机材料学报》2015,(11)
采用等离子体辉光监控系统(PEM)反馈控制反应溅射过程,在石英基底上制备出单斜相VO_2薄膜,并研究了反馈控制下反应溅射的等离子体相对辉光强度与氧气流量的关系。实验结果表明:在不同的反应压强(0.8 Pa、0.5 Pa、0.2 Pa)下,通过调整相对辉光强度值(REI)均可稳定获得单斜相VO_2薄膜,对应的REI值分别为0.6~0.65、0.65、0.6。XRD测试结果表明VO_2薄膜具有明显的(011)晶面取向,XPS测试结果表明薄膜的化学计量比为VO_(2.02)。VO_2薄膜在2.5μm处的变温透过率测试结果显示薄膜在相变前后的透过率变化达到65%,相变温度确定为66℃。 相似文献
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《材料导报》2020,(6)
采用高功率脉冲磁控溅射在石英玻璃基片上成功制备了具有明显金属-绝缘体转变特性的多晶VO_2薄膜,其最低相变温度仅为32℃。X射线衍射结果表明沉积薄膜的晶体结构均为存在明显晶格畸变的VO_2(M),且薄膜(011)晶面间距越接近相变后VO_2(R)(110)晶面的晶面间距,相变温度越低。根据试验结果,利用从头算分子动力学分别对VO_2金属-绝缘体相变过程的晶体结构与态密度演化规律进行了研究。结果表明:随计算温度升高,不同(011)晶面间距绝缘态超胞的晶体结构均逐渐由VO_2(M)向VO_2(R)转变,同时伴随着禁带宽度的逐渐降低,最终转变为费米能级完全被电子占据的金属态;初始VO_2(M)超胞(011)面的晶面间距与相变后VO_2(R)(110)面的晶面间距之差越小,费米能级附近的禁带宽度也越小,这可能是导致VO_2金属-绝缘体转变温度降低的本质物理原因。 相似文献
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为获得具有良好相变特性的M相VO_2粉体,本文以V_2O_5为原料、甲醇作还原剂,采用微波辅热制备M相VO_2粉体.探讨了微波辅热功率、填充度、反应温度、反应时间、甲醇用量因素对制备VO_2的影响,采用X射线衍射(XRD)、差示扫描量热法(DSC)和扫描电子显微镜(SEM),对产物进行了物相、相变和形貌特征的表征.结果表明:在微波辅热功率为1 000 kW,填充度为0.7,反应温度为250℃时,反应时间为60 min,V_2O_5质量与甲醇体积比为5∶3时,得到B相的VO_2粉体;B相的VO_2再经过800℃高温热处理后完全转化为具有相变功能的M相,M相VO_2粉体纯度为99.20%,产率为92.30%,相变点温度为68.6℃,晶体形貌呈现较匀称的棒状结构,长度为1~2μm. 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
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. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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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. 相似文献
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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.…… 相似文献
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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. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
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. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
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 ... 相似文献
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《中国标准化(英文版)》2014,(4)
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 相似文献
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《中国标准化(英文版)》2014,(5)
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. 相似文献