顶杆法热膨胀系数测试在材料性能研究中的应用

通过测试材料热膨胀系数随温度的变化情况,可以了解材料的热物理性能和温度变化过程中材料内部发生的化学反应。综述了利用顶杆法测试材料热膨胀系数在材料热物理性能测试、研究及工艺制定等方面的应用,详细介绍了各种应用的背景和测试要点,并指出了热膨胀测试设备未来的发展趋势。     

碳/环氧管件的低温热膨胀系数测试研究

介绍了采用千分表测量碳/环氧复合材料管件低温热膨胀系数的测试方法,对于管件轴向和径向等不同方向的热膨胀系数测试,采用了不同的测试装置。叙述了测试过程及注意事项,指出了对管件进行热膨胀测试时,不应该采用传统的从管件取出小件试样进行测试的方法,两者数据存在较大差别。另外还讨论了管件低温热膨胀测试数据的规律、影响因素,分析了测量误差影响因素如顶杆带来的误差等,提出了解决方法。对于多次测量的碳纤维复合材料低温热膨胀测试数据逐渐减小问题,进行了初步探讨和分析。给出了某种工艺的碳纤维复合材料管件热膨胀系数与温度曲线。     

低温缓冲层对金刚石衬底上GaN的沉积作用

采用电子回旋共振等离子体增强金属有机物化学气相沉积技术,以自支撑金刚石厚膜作为衬底,改变缓冲层参数条件,低温沉积氮化镓(Ga N)薄膜材料。实验结束之后,利用反射高能电子衍射、X射线衍射和原子力显微镜系统性对实验制备的薄膜样品进行测试分析,探究引入低温缓冲层与无缓冲层以及改变缓冲层沉积温度对Ga N薄膜质量的影响。结果表明,低温缓冲层的制备,对后续的薄膜样品沉积制备起到减小晶格失配的作用,而且低温缓冲层沉积温度在100℃时,沉积制备的薄膜样品呈高度c轴择优取向,结晶性较好;薄膜表面平整。     

采用低温辐射加热源的有机半导体薄膜真空蒸发设备的研制

针对有机半导体材料的蒸发温度低的特点,设计并制作了低温辐射式加热器和衬底加热器.低温辐射式加热器能有效的克服传统加热源在制备有机半导体薄膜过程中的缺点.衬底加热器也能明显的改善有机半导体薄膜的表面形貌.采用低温辐射式加热器和衬底加热器对有机半导体材料进行蒸发或溅射镀膜能够取得良好效果.其制作成本低,加热效率高,同时又能提高原有设备功效,在教学和科研生产中有着广泛的应用前景.     

超导线圈的等效热膨胀系数的理论与实验研究

给出了计算超导线圈等效热膨胀率的理论模型和计算方法,对比了各种测量材料线膨胀系数的实验方法,并且给出了低温应变片测量热膨胀系数的技术原理.采用低温应变片法测量了矩形截面导线缠绕成型的超导线圈由77 K到300 K的线膨胀系数,并将实验测试结果与理论计算结果进行了对比分析.     

火灾下平行钢丝束温度膨胀及高温蠕变试验研究

采用非接触式应变视频测量系统,对常用于实际工程的1670级平行钢丝束进行了15个温度水平下的温度膨胀试验以及多应力水平下的高温蠕变试验,并对历经2 h高温蠕变试验后冷却至室温的平行钢丝束试件进行了抗拉强度测试,获取了平行钢丝束热膨胀应变历程及高温蠕变应变历程曲线。试验结果表明:平行钢丝束热膨胀应变随着温度升高呈非线性增长,且在750 ℃附近材料微结构发生相变;温度和应力水平对高温蠕变历程均会产生显著影响;蠕变试验温度愈高,应力水平对历经高温后平行钢丝束的剩余抗拉强度的影响愈显著;与1860级预应力钢绞线相比,1670级平行钢丝束具有较小的高温蠕变应变。基于试验数据,建议了平行钢丝束热膨胀系数关于温度的函数式及高温蠕变模型。该文所建议的平行钢丝束热膨胀系数及高温蠕变模型有利于预应力钢结构火灾高温下的力学响应分析。     

典型红外光学薄膜材料折射率温度特性研究

红外光学薄膜材料在红外光学系统中的应用非常广泛,其折射率是光学薄膜设计的重要参量,鉴于空间应用的特殊需求,红外光学薄膜通常工作在低温条件下,红外光学薄膜材料的折射率会随温度改变而发生变化,对于红外光学薄膜的研制有很大影响。论文研究了红外光学薄膜材料折射率的温度特性,总结了红外光学薄膜材料折射率色散模型,并对红外光学薄膜材料折射率温度特性研究发展趋势进行了展望。     

钢丝绳低温热膨胀系数试验方法研究

介绍了一种钢丝绳低温热膨胀系数试验方法.针对钢丝绳使用条件下的模拟熟膨胀试验,采用低热膨胀系数材料制成部件与钢丝绳连接,用砝码对钢丝绳施加预紧力,设置恒温区间,研制了一台低温热膨胀系数测量设备.采用无氧铜标准试样进行了标定和校准,经过修正的测量数据与标准试样数据比较,偏差小于5％.在- 100-+ 25℃温区内,对3种...     

用热弯实验方法决定导电薄膜的热膨胀系数

研究了热-力载荷下薄膜/基板复合梁的弯曲问题,导出了薄膜的热膨胀系数与试样表面的温度和变形之间的关系式;提出一种测量导电薄膜的热膨胀系数的方法,并用热弯实验测SnO₂膜的热膨胀系数。      

电子束蒸发沉积重掺硅薄膜及其在低辐射玻璃上的应用

采用电子束蒸发法以普通玻璃为基板制备了重掺硅薄膜,通过SEM、EDS、透射光谱对其形貌、成分以及透射率进行了测试表征.进一步采用铝诱导低温晶化法在玻璃基板上沉积Al薄膜,对重掺硅薄膜进行铝诱导晶化.XRD测试、电学性能测试以及可见-红外光谱透射率测试结果表明,硅薄膜在温度为300℃以上出现了Si(111)的衍射峰,薄膜的导电性得到了提高,且具有较强的红外反射能力,表明在低辐射玻璃上具有一定的应用价值.同时采用电子束蒸发法制备了结构为glass/Si/Ag/Si的Ag基低辐射玻璃,通过光学性质测试和腐蚀情况观察结果表明硅薄膜具有保护低辐射薄膜的作用.     

The effect of grain size and film thickness on the thermal expansion coefficient of copper thin films

Cu thin films underwent thermal cycling to determine their coefficient of thermal expansion (CTE). The thermal stress of the Cu thin films with various microstructures (different grain size and film thickness) was measured using a curvature measurement system. The thermal expansion coefficients of the films were obtained from the slope of the stress-temperature curve with the knowledge of the Young's modulus and Poisson's ratio. The change in thermal stress with temperature of the Cu thin films tended to decrease with increasing grain size, resulting in an increase in the CTE. The thickness of Cu thin film had little effect on the thermal stress or the CTE.     

A structural comparison of electroless and electroplated nickel

Nickel that has been electrolessly deposited from a low temperature hypophosphite bath undergoes severe cracking when heat treated. The cracks, which are of two different types, can weaken the nickel deposit and can lead to leak paths in composite structures. In the study reported here the characteristics of thin nickel films were studied by several methods, all of which can be applied to any crystalline thin film: an X-ray method for stress and precipitation sequences; electron microscopy; cross-sectional analysis; kinetic studies. The electroless nickel was compared with a low stress electroplated nickel which does not crack with heat treatment. The electroplated nickel was found not only to have lower stress than the electroless nickel but also to have no significant secondary phase precipitation.     

Stress stability and thermo-mechanical properties of reactively sputtered alumina films

The stability of residual stress inherent on deposition in reactively sputtered alumina films is studied during thermal cycling and annealing, simulating temperature excursions experienced by the films during device fabrication and subsequent operation. Increasing the magnitude of substrate bias applied during deposition acts to reduce the amount of argon incorporated in the films; more incorporated argon corresponds to smaller values of modulus and hardness and a larger coefficient of thermal expansion (CTE). Large, irreversible changes in film stress develop on heating, acting to decrease the compressive residual stress of films deposited on silicon substrates to a smaller, equilibrium value, whereas films deposited on Al₂O₃-TiC substrates behave differently. Thermal cycling and annealing have little effect on the modulus and CTE, but the hardness increases significantly and the threshold load for indentation crack initiation decreases precipitously during heat treatment. Possible mechanisms of irreversible stress development and mechanical property modifications are discussed.     

3D针刺C/SiC-TaC复合材料的热膨胀性能

采用液相加压浸渗法将TaC渗入到三维针刺毡中, 并结合反应熔体渗透法(RMI)制得C/SiC-TaC复合材料。采用热膨胀仪测量了热处理前后复合材料从室温到1400 ℃温度范围内的热膨胀系数(CTE), 发现C/SiC-TaC的CTE数值较C/SiC的高。从材料内部热应力的变化、 制备方法及添加物和基体的性能方面定性地分析了CTE的变化机制。研究表明, C/SiC-TaC复合材料的膨胀性能在各个温度段的变化机制不同, 低温段(1100 ℃以下)CTE的不断上升主要由90°无纬布、 TaC和SiC基体贡献, 该阶段的起伏波动主要由复合材料的结构应力和孔隙分布不均及残余Si产生; 高温段(1100 ℃以上)的热膨胀性能主要由0°无纬布和界面热应力决定。热处理降低了复合材料在1100 ℃以下的CTE, 也改变了高温段的变化规律。      

泡沫塑料材料的低温线膨胀系数测定

采用自行研制的高精度低温位移传感器测量出泡沫塑料材料从室温到液氢温度的微应变情况,对试验结果的可靠性进行分析.实验结果表明:低温位移传感器可准确、稳定地得出泡沫塑料材料的线膨胀系数,是一种简单实用的线膨胀系数测试方法.     

Residual stresses of sputtering titanium thin films at various substrate temperatures

This work seeks to characterize the residual stresses of titanium thin films as they are affected by various substrate temperatures during the sputtering process. The titanium thin films are deposited on silicon wafers by a RF magnetron sputter while different substrate temperatures are considered. The residual stresses are measured by both X-ray diffraction and a substrate curvature method, and consistent results are obtained by both methods. The results show that the residual stress decreases as the substrate temperature increases, in which the stress changes from tensile to compressive when the substrate temperature increases from 25 to 50 degrees C. Furthermore, the elastic modulus and hardness of the titanium thin films are tested with a nanoindenter using a standard Berkovich probe. Correlations between the residual stresses and mechanical properties measured by nanoindentation are also discussed.     

交替频率PECVD方法沉积低应力氮化硅薄膜及其性质研究

用ＰＥＣＶＤ方法制备氮化硅薄膜,研究了射频频率对氮化硅薄膜的沉积和性质的影响。结果表明,在低频下（１００ＫＨｚ）制备的氮化硅薄膜密度较大,具有８ｘ１０９Ｐａ左右的压应力和较小的刻蚀速率;而高频（１３．５６ＭＨｚ）沉积的氮化硅薄膜密度较小,具体约２ｘ１０９Ｐａ的张应力,刻蚀速率较大。红外光谱表明,薄膜性质同薄膜中的氢原子成键情况有关。实验中利用高、低频交替沉积的方法,成功地制备了低应力（１０７Ｐａ）氮化硅薄膜。当加热到５００Ｃ时,应力较大的氮化硅薄膜会发生开裂（张应力）或拱起（压应力）。低应力的氮化硅薄膜能够承受７００Ｃ的温度,温度更高时,薄膜的完整性因氢溢出而破坏。     

Design and control of porosity in oxide thin films grown by PECVD

This work presents a series of results about the synthesis and characterization of porous oxide thin films (thicknesses ∼ ∼300 nm) prepared at low temperature by PECVD. Two different experimental strategies are described. A first one, used for the preparation of porous SiO₂ thin films, consists of the use of a polymeric sacrificial layer that is removed during deposition of the oxide thin film. A second one, used for the preparation of TiO₂ thin films, relies on the modification of some critical deposition parameters (i.e., temperature, Ar/O₂ ratio in the plasma mixture, etc.). Thin films with a large variation of pore structures as evidenced by Scanning Electron Microscopy (SEM) have been prepared by the two methodologies. The thin films have been characterised by different techniques and some of their properties related with their microstructure assessed by ellipsometry (optical behaviour) or water contact angle measurements (hydrophobic/hydrophilic character). A quartz crystal monitor has been used to measure water vapour adsorption/desorption isotherms in the films. From the shape of these isotherms it is possible to estimate the type of pores existing in the different thin films. Examples of the potential use of these porous thin films as humidity sensors or hydrophilic surfaces are reported.     

Optical and mechanical characteristics of zinc sulphide-thorium fluoride mixed composition thin films for use in the near infrared region (1–10µm)

Mixed composition thin films of zinc sulphide-thorium fluoride have been deposited on glass and silicon substrates by thermal evaporation of mixtures of these materials in different proportions, from a single resistively heated source. The films are characterized for their optical properties (refractive index and extinction coefficient), mechanical properties (intrinsic stress), surface morphology and chemical composition. It is found that these films have tailorable refractive indices and low losses, and that films with certain compositions have low intrinsic stress and smooth surface morphology, making them suitable for incorporation in thin film multilayers for use in the near infrared region up to at least 10μm.     

溶胶-凝胶法制备SiO_2-TiO_2纳米复合薄膜紫外光处理的研究

采用溶胶－凝胶技术,结合二步水解法分别在单晶硅片、石英玻璃和Ｋｇ玻璃上制备ＳiＯ2、ＴiＯ2纳米复合薄膜,采用高压汞灯对其进行紫外光处理,分别用ＡＦＭ、椭偏仪、ＦＴＩＲ、ＵＶ－Ｖis分光光度计以及ＸＲＤ对凝胶膜紫外光处理前后的光学性能和结构进行研究,并与传统的热处理进行比较与分析．研究表明,紫外光处理是实现凝胶膜低温致密化的有效方法之一,其致密化的机理不同于传统的热处理,主要是通过紫外高能光子诱导复合薄膜网络结构的原子中的电子激发,导致原子化学键的断裂,进而产生结构重组而致密化．