离子束外延制备GaAs:Gd薄膜

　室温条件下,用低能离子束外延制备了GaAs∶Gd薄膜,X射线衍射(XRD)结果表明除了GaAs衬底峰没有发现其它新相的衍射峰,并借助于高分辨X射线衍射(HR XRD)进一步分析了晶格常数的变化特点。俄歇电子能谱(AES)分析了样品表面的成分,及元素随深度的分布规律,在60nm深处元素的相对含量发生明显改变,运用原子力显微镜(AFM)揭示了样品表面的形貌特点。

低能离子束方法制备磁性Fe-Si合金薄膜

　利用质量分离的低能离子束技术,获得了磁性Fe Si合金薄膜。利用俄歇电子能谱法(AES)、X射线衍射法(XRD)以及交变梯度样品磁强计(AGM)测试了样品的组分、结构以及磁特性。测试结果表明在室温下制备的Fe Si合金是Fe组分渐变的非晶薄膜,具有室温铁磁性。当衬底温度为300℃时制备的非晶Fe Si薄膜中有Fe硅化物FeSi相产生,样品的铁磁性被抑制。

微重力落管法制备Nd_(60)Al_(10)Fe_(20)Co_(10)非晶薄片的磁性能研究

采用微重力落管法制得了Nd6 0 Al1 0 Fe2 0 Co1 0 非晶薄片 .利用X衍射 (XRD)分析了Nd6 0 Al1 0 Fe2 0 Co1 0 非晶薄片的结构特征 .用振动样品磁强计 (VSM)研究了其磁性能 .结果表明微重力落管法制得的非晶薄片具有硬磁性 ,与快速非平衡凝固(如甩带法 )试样的XRD相比 ,尽管其曲线还是较为典型的非晶相漫散衍射峰 ,但已有少量的不规则的类似晶化的突起小峰 ,表明该非晶片中已经有微量晶态合金或者细小晶粒析出 ,初步分析可能是生成了类似于亚稳A1 相的短程有序原子团簇或者是较大尺寸的纳米晶 ,这种短程有序原子团簇或纳米晶是Nd6 0 Al1 0 Fe2 0 Co1 0 非晶薄片显示硬磁性的主要原因

低能离子束方法制备Fe组分渐变的Fe-Si薄膜

利用质量分离的低能离子束技术 ,获得了Fe组分渐变的Fe Si薄膜。利用俄歇电子能谱法 (AES)、X射线衍射法 (XRD)以及X射线光电子能谱法 (XPS)测试了薄膜的组分、结构特性。测试结果表明 ,在室温下制备的Fe Si薄膜呈非晶态。非晶薄膜在 40 0℃下退火 2 0min后晶化 ,没有Fe的硅化物相形成。退火后Fe Si薄膜的Fe组分从表面向内部逐渐降低。

Thermal Residual Stresses in SiCw/Al Composite

<正> The SiCw/6061Al composites were fabricated by squeeze casting method. Varia-tions of thermal residual stresses with quenching temperature, cooling manner, aging time and thethermal-cold cycle process in thin specimens,and the distributions of thermal residual stresses alongthe distances from the surface and changes with heating temperatnres in thick specimens were stud-ied by means of X-ray diffraction (XRD). The effects of residual stresses on the mierostructure, di-mensional stability and age-hardening behavior were studied by SEM, TEM observations, and tensiletest. The results showed that there existed macrostress, microstress and thermal mismatch stress inSiCw/Al compo-site,and the presence of microstress and thermal mismatch stress has no influenceon the measurement of macrostress, but the macrostress can affect the measured value of thermalmismatch stress. Thermal res dual stress induced during the composite fabrication process, will be further in-creased when the composite were subjected to the e

低能离子束方法制备重掺杂Fe的Si∶Fe固溶体

利用质量分离的低能离子束方法 ,以离子能量为 1 0 0 0 e V,剂量为 3× 1 0 1 7cm- 2 ,室温下往 p型 Si(1 1 1 )单晶衬底注入 Fe离子 ,注入的样品在 4 0 0℃真空下进行热处理 .俄歇电子能谱法 (AES)对原位注入样品深度分析表明 Fe离子浅注入到 p型 Si单晶衬底 ,注入深度约为 4 2 nm.X射线衍射法 (XRD)对热处理样品结构分析发现只有 Si衬底的衍射峰 ,没有其他新相 .X射线光电子能谱法 (XPS)对热处理样品表面分析发现 Fe2 p束缚能对应于单质 Fe的峰 ,没有形成 Fe的硅化物 .这些结果表明重掺杂 Fe的 Si∶ Fe固溶体被制备 .电化学 C- V法测量了热处理后样品载流子浓度随深度的分布 ,发现 Fe重掺杂 Si致使 Si的导电类型从 p型转为 n型 ,Si∶ Fe固溶体和 Si衬底形成 pn结 ,具有整流特性

激光熔覆大厚度Fe_(57)Co_8Ni_8Zr_(10)Si_4B_(13)非晶表层及其微结构研究

利用激光熔覆制备出1.2mm厚的Fe_(57)Co_8Ni_8Zr_(10)Si_4B_(13)大厚度非晶表层。用XRD,ES,TEM,DSC及硬度对获得的非晶表层进行了多种分析，研究了非晶合金表层的微结构与非晶形成能力。初步探讨了大厚度非晶表层的形式机制。

Undercooling and Rapid Solidification of Nb-Si Eutectic Alloys Studied by Long Drop Tube

Niobium-silicide alloys have great potential for high temperature turbine applications. The two-phase Nb/Nb5Si3 in situ composites exhibit a good balance in mechanical properties. Using the 52 in drop tube, the effect of undercooling and rapid solidification on the solidification process and micro-structural characterization of Nb-Si eutectic alloy was studied. The microstructures of the Nb-Si composites were investigated by optics microscope (OM), X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with X-ray energy dispersive spectrometry (EDS). Up to 480 K, deep undercooling of the Nb-Si eutectic samples was successfully obtained, which corresponds to 25% of the liquidus temperature. Contrasting to the conventional microstructure usually found in the Nb-Si eutectic alloy, the microstructure of the undercooled sample is divided into the fine and coarse regions. The most commonly observed microstructure is Nb+Nb5Si3, and the Nb3Si phase is not be found. The change of coarseness of microstructure is due to different cooling rates during and after recalescence. The large undercooling is sufficient to completely bypass the high temperature phase field.

Formation and Structure of Composite Coating of HAD and Micro-Plasma Oxidation on A3 Steel

Composite coatings were obtained on A3 steel by hot dipping aluminum(HAD) at 720 degreesC for 6 min and micro-plasma oxidation (MPO) in alkali electrolyte. The surface morphology, element distribution and interface structure of composite coatings were studied by means of XRD, SEM and EDS. The results show that the composite coatings obtained through HAD/MPO on A3 steel consist of four layers. From the surface to the substrate, the layer is loose Al2O3 ceramic, compact Al2O3 ceramic, At and FeAl intermetallic compound layer in turn. The adhesions among all the layers are strengthened because the ceramic layer formed at the At surface originally, FeAl intermetallic compound layer and substrate are combined in metallurgical form through mutual diffusion during HAD process. Initial experiment results disclose that the anti-corrosion performance and wear resistance of composite coating are obviously improved through HAD/MPO treatment.

过滤电弧沉积TiN、ZrN和TiN／CrN多层纳米薄膜的性能比较

用过滤电弧离子镀(FAMIP)技术在高速钢基体上沉积了TiN、ZrN单层薄膜和TiN／CrN多层纳米薄膜。利用扫描电子显微镜(SEM)观察了薄膜及其划痕的表面形貌;用X射线衍射仪(XRD)分析了薄膜的相组成,结合显微探针仪、划痕试验机、金相显微镜和钻床,研究了金属陶瓷单层和多层纳米薄膜的性能并进行比较。研究结果表明:3种薄膜的临界载荷值均大于80N,多层纳米薄膜的耐磨性明显优于2种单层薄膜。

EDTA溶胶凝胶法制备La_2Ni_(1-x)M_xO_4(M=Cu,Fe)稀土复合氧化物

本文以EDTA溶胶凝胶法合成K2NiF4型稀土复合氧化物La2Ni1-xMxO4(M=Cu,Fe),并对反应生成粉体分别进行SEM表征与XRD测试。结果表明,选取合适的制备工艺,可以形成La2Ni1-xMxO4(M=Cu,Fe)稀土复合氧化物材料;随着掺杂离子半径增大,生成材料晶格常数a增大同时,c减少,粉体颗粒粒径较大,同时少量杂相存在。

微/纳米氧化锌（ZnO）的生长、性质及其应用研究

纳米氧化锌（ZnO）是一种直接宽带隙半导体材料，室温下其禁带隙宽为本3.37 eV，激子束缚能为60 meV。纳米ZnO有明显的尺寸效应、表面和界面效应等，物理化学性能优越。在压电材料、铁电材料、平面显示、表面声波、传感器、场发射器件、激光、光催化等方面有着广泛的用途。近年来，对纳米ZnO材料的研究成为国内外的一个热点。 本论文研究了用化学气相沉积（CVD）法制备微/纳米ZnO材料。通过控制实验条件，合成了多种特殊结构和形貌的微/纳米ZnO材料，并用扫描电子显微镜（SEM）、高分辨率透射电镜（HR-TEM）、X-射线衍射仪（XRD）、Raman光谱和光致发光（PL）等对材料的结构和光学性能进行了表征。采用CVD法，在温度为630 °C，氧气流量为15 sccm，氩气流量为300 sccm的条件下，制备了一种纳米带冠四足状ZnO（T-ZnO）。此结构ZnO材料的每根足顶端均有一规则的六方帽形结构，具有很大的比表面积。实验结果表明：合成的ZnO材料为纤维锌矿结构单晶，并且沿着(0001)方向生长；室温下的PL谱有两个激发峰，一个是在393 nm处相对较弱的近带紫外峰，另一个是在511 nm处强峰。而材料在600 °C下氧气中退火30 min后，511 nm附近的绿光激发辐射峰则基本消失了，这说明在511 nm处的绿光激发辐射峰可能是由于氧空位引起的。此外，通过改变实验条件，还得到了其他多种结构的微/纳米ZnO材料。 通过大量实验，找到了一种在低温下合成微/纳米ZnO材料的新方法，即水蒸气氧化法。用ZnI2作为锌源，水蒸气作为氧化剂，实验温度在300～500 °C范围内，大大低于通常CVD法的500～1500 °C。采用此法，用硅做基底，得到了一系列有趣的实验结果，大多数情况下ZnO纳米晶自组装成很规则的圆。而在瓷舟中收集到的纳米ZnO跟普通CVD法结果相似，可以得到锥状、棒状等结构的纳米晶，但其生长方式与硅基底上的有很大差别。此外，用水蒸气氧化法，还实现了ZnO纳米晶在碳纳米管（CNTs）上的直接生长，而且其PL性能增强，这可能是纳米ZnO和CNTs相互耦合的结果。在700 °C温度下，以锌粉和ZnI2作为锌源，用水蒸气作为氧化剂，在硅基底的正反面分别得到了纳米棒和纳米推子阵列。此外，还对水蒸气氧化法的化学反应机理进行了分析，实验结果证明：固态ZnI2在受热和一定真空度下先蒸发成ZnI2分子，ZnI2分子遇到水蒸气发生反应生成偶极ZnO分子，这些ZnO偶极分子在硅基底上通过静电力自组装成特殊的几何形状。 此外，还通过分子动力学模拟的方法，对材料的力学性能进行了研究，得到了ZnO的弹性常数和体弹性模量，模拟值跟其他研究人员的实验和模拟结果吻合得很好，并估出算了ZnO晶体的表面能和断裂韧性。 本论文还对制备材料的光催化性能进行了系统的研究，采用CVD法制备ZnO，对铬黑T（EBT）进行光催化降解实验。通过正交实验方法，得到了ZnO催化降解EBT的最佳工艺条件，即催化剂用量为5 g/L，光照强度为120 W，反应温度为20 °C，反应时间为120 min，EBT浓度为10 mg/L，溶液pH值为4。 在最佳实验条件下，20分钟内有95%的EBT被降解完，30分钟内则全部降解。因此，ZnO在EBT的降解中催化效率很高，在废水处理中具有潜在的应用前景。

激光制备高温结构用涂层的研究

该文以提高在高温、高压、高速、重载和腐蚀介质等恶劣工况下使用的枪管、炮管、发动机叶片、热轧辊等零部件使用性能和寿命为应用背景,在综述前人工作的起点上,以制备科学的研究为基础,从熔覆层的使用性能和工艺性能(降低残余应力,防止开裂)出发,利用激光熔覆和复合材料原位合成技术,围绕成分、相组成、组织结构控制和工艺优化,设计并研制了FeMoSi、MoSi<,2>-SiC、α-Fe(Al)/Fe<,3>Al和FeAl四种在不同温度和服径工况下使用,能耐高温氧化、烧蚀和磨损的优异的新型高温结构用金属间化合物涂层.用OM、XRD、SEM、EDAX和显微硬度仪对熔覆层的组织结构/性能进行了研究.

Long-Term Evolution Of Delayed Ettringite And Gypsum In Portland Cement Mortars Under Sulfate Erosion

The magnitude evolution of ettringite and gypsum in hydrated Portland cement mortars due to sulfate attack was detected by X-ray powder diffraction. The influences of sulfate concentration and water-to-cement ratio on the evolution of ettringite and gypsum were investigated. Experimental results show that the magnitude of ettringite formation in sodium sulfate solution follows a three-stage process, namely, the 'penetration period', 'enhance period of strength', and 'macro-crack period'. The cracking of concrete materials is mainly attributed to the effect of ettringite. The gypsum formations occurred in two stages, the 'latent period' and the 'accelerated period'. The gypsum formation including ettringite formation was relative to the linear expansion of mortars to some extend. Both water-to-cement ratio and sulfate concentration play important roles in the evolution of ettringite and gypsum. (C) 2008 Elsevier Ltd. All rights reserved.

Effect of humidity on microstructure and properties of YBCO film prepared by TFA-MOD method

Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3 (001) substrate by metal organic deposition method. All YBCO films were fired at 820 degrees C in humidity range of 2.6%-19.7% atmosphere. Microstructure of YBCO thin films was analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Superconducting properties of YBCO films were measured by four-probe method. XRD results showed that the second phase (such as BaF2)and a-axis-oriented grains existed in the films prepared at 2.6% humidity condition; a-axis-oriented grains increased in the film prepared at higher than 4.2% humidity condition; almost pure c-axias-oriented grains existed in the films fired at 4.2% humidity condition. Morphologies of the YBCO films showed that all films had a smooth and crack-free surface. YBCO film prepared at 4.2% humidity condition showed J(c) value of 3.3 MA/cm(2) at 77 K in self-field.