复合型超声马达纵-扭振动固有频率简并研究

纵、扭振动固有频率简并是提高纵-扭复合型超声马达输出力矩的关键问题。然而同一弹性体内的纵振固有频率远高于扭振固有频率．目前对两种振动固有频率的简并缺乏深入的理论研究。纵一扭复合型超声马达振动分析模型都基于一维理论。在此提出了一种纵、扭振动固有频率简并的新方法。通过将纵一扭复合型超声马达设计成双定子对称结构．在定子上附加一个调整环改变定子的力学边界条件。实现纵、扭振动同频共振。应用Hamilton原理建立了考虑泊松效应的定子纵、扭振动理论模型，分析了定子的纵振与扭振第一阶固有频率随调整环质量和位置的变化规律，通过优化马达的几何结构参数获得了纵振与扭振的同频谐振点。     

宇称时间对称声子晶体纳米杆波动特性分析

提出一种宇称时间对称声子晶体纳米杆结构,并构建一种非局部有限元杆的波动力学模型,研究宇称时间对称声子晶体纳米杆中一些新颖的弹性波传播机理。研究结果表明宇称时间对称性声子晶体纳米杆的能带结构出现简并点,且简并点之前频率为实数,简并点之后频率则以复共轭的形式成对出现。虚部能带结构中正、负频率的成对出现表明结构中单色波传播呈现增强和衰减的效应。进一步研究尺寸效应对一维宇称时间对称声子晶体纳米杆结构中弹性波传播的影响,研究表明尺寸效应可以改变结构带隙频率所在位置及其宽度。该研究为宇称时间对称性声子晶体纳米结构在振动与弹性波控制领域的工程应用提供一定的理论指导。     

电磁防护仿生原理与故障自修复机制研究

借鉴生物神经网络信息传递的抗扰特点,开展了电磁干扰环境下通过仿生方式进行的电子电路抗扰与防护研究,以便采用新原理、新技术和新方法解决传统的电磁干扰防护手段不足的问题。通过基于布尔模型的复杂生物网络拓扑建模与简并特征分析,证明了网络简并性与功能鲁棒性之间的相互作用关系,以解决抗扰原理问题;通过构建基于神经元电路和可塑突触电路的神经网络电路模型,分析了突触权重的分布对于网络自修复特性的影响,以解决防护机制问题。进而,为电磁防护仿生原理及自修复机制的深入研究形成了一定的理论基础并完成了前期实践。     

透明导电膜ZnO:Al(ZAO)的组织结构与特性

ZnO:Al(ZAO)是一种简单并半导体氧化物薄膜材料，具有高的载流子浓度和光学禁带宽度，因而具有优异的电学和光学性能，极具应用价值，对于其能级高度简并的ZAO半导体薄膜材料，在较低的温度下，离化杂质散射占主导地位，在较高的温度下，晶格振动散射将成为主要的散射机制；晶界散射仅当晶粒尺寸较小（与电子的平均自由程相当）时才起作用，本文分析了ZAO薄膜的制备方法，晶体结构特性，电子和光学性能以及载流子的散射机制。     

纵-扭复合超声振动加工系统设计及频率简并研究

纵-扭复合超声振动加工技术在硬脆性材料的加工中受到越来越多的重视,针对该种需求,设计了一种纵-扭复合超声振动加工系统,基于有限元方法对该类系统普遍存在的频率简并问题进行了研究。利用数值解析方法设计出超声换能器和超声变幅杆,之后在变幅杆上做出螺旋槽,一部分纵向振动转换为扭转振动;以目标频率附近的纵、扭谐振频率尽量接近为原则,利用有限元软件分析系统的结构参数对纵、扭谐振频率的影响规律,实现频率简并;在此基础上对系统进行模态分析和瞬态动力学分析,结果表明系统可以实现纵-扭复合超声振动,验证了此种频率简并方法的有效性和实用性。     

半导体量子点玻璃的研究进展

介绍了半导体量子点材料禁阻类型,详细阐述了共熔法、溶胶-凝胶法、离子注入法等半导体量子点玻璃材料的制备方法,探讨了半导体量子点玻璃的尺寸效应、禁阻效应、库仑阻塞效应和非线性光学效应等特性及其未来应用前景.     

3种偶氮化合物的合成及三阶非线性光学性能

合成了3种1,3,4-噻二唑偶氮化合物,其中1种为新化合物,用IR、1H NMR和元素分析表征了其结构.采用飞秒激光,运用简并四波混频法,研究了化合物在非共振状态下的三阶非线性光学性能.它们的三阶非线性光学极化率X(3)为(3.84～3.95)×10-13esu,非线性折射率n2为(7.07～7.27)×10-12esu,分子二阶超极化率γ为(3.56～3.72)×1031esu,响应时间τ为101fs.探索了化合物的分子结构对三阶非线性光学性能的影响.引入离域能小的芳杂环,形成吸供构型,增大取代基的吸或供电子能力等有利于获得较大的三阶非线性光学性能.     

非磁性半导体磁阻效应物理模型研究

非磁性半导体的磁阻效应一直以来受到了科研工作者的广泛关注,具有重大的研究意义和价值,在磁性传感器、高密度存储等方面有着潜在应用前景。主要综述了几种典型的非磁性半导体磁阻效应物理模型,即空间电荷效应模型、纳米非均匀性模型、二极管辅助几何增强模型、载流子复合模型和雪崩电离模型。最后,对非磁性半导体的雪崩电离基磁阻效应进行了分析和展望。     

单元素半导体量子点制备及其光致发光性能的研究进展

单元素半导体量子点的制备成功使光电集成成为可能.介绍了单元素半导体量子点的制备方法,包括射频磁控溅射技术、硅离子注入技术、化学气相沉积法、溶胶-凝胶法等;并且介绍了单元素半导体量子点的发光机理模型,包括量子限制效应模型、与氧有关的缺陷发光、量子限制效应-发光中心复合发光和界面层中的激子效应发光等;另外对单元素半导体量子点的发展前景进行了展望.     

有机功能色素类化合物的合成与三阶非线性光学性能

设计并合成了苯并二呋喃酮、双偶氮-9,10-蒽二酮、苯并噻蒽以及偶氮-1,3,4-噻二唑4个系列的有机色素类化合物,并用UV,IR,1H NMR和元素分析表征了结构.采用飞秒激光,运用简并四波混频法,研究了化合物的三阶非线性光学性能.它们的三阶非线性光学极化率χ(3)为2.64～3.95×10-13esu,非线性折射n2为4.85～7.27×10-12esu,分子二阶超极化率γ为2.85～3.72×10-31esu.探索了化合物的分子结构对三阶非线性光学性能的影响.长的共轭链、吸供取代基和杂环的引入、取代基强的供电子或吸电子能力等因素有利于获得较大的三阶非线性光学性能.     

二氧化钛掺杂改性的研究进展

二氧化钛作为一种具有光催化活性的氧化物半导体材料,在利用太阳能降解环境污染物的领域具有广阔的应用前景。但是,由于二氧化钛存在光量子产率低,禁带宽度较大,光催化反应活性较低等缺点,严重阻碍了其在实际应用中的发展。目前,为改善二氧化钛的光催化性能,多种化学物质被用于二氧化钛的掺杂研究,包括过渡金属、贵金属、非金属和稀土元素等,不论是对二氧化钛进行单独掺杂或共掺杂都已被广泛地研究,结果表明,适当的掺杂将显著提高二氧化钛的光催化活性。本文对该领域的研究现状进行了综述,在此基础上对二氧化钛掺杂改性研究的发展进行了展望。     

Design and synthesis of polymetallic nanoparticles and their catalytic applications

High-temperature hydrogen reduction reactions enable the synthesis and processing of binary metal oxide composite nanoparticles starting from titanium, ruthenium, and silicon, while the use of a surface modifier and an organic surfactant enables the synthesis of catalytic thin films from binary semiconductor oxides. Surface characterization by XRD, SEM, TEM, AFM, Raman spectroscopy, and BET measurements indicate that the incorporation of binary oxide particles into the semiconductor materials altered the surface properties and morphology of the nanoparticles while the surface modifier and organic surfactant loading can be experimentally adjusted to obtain thin films of varying morphological characteristics.     

一种新型的半导体光催化剂——纳米氧化亚铜

半导体光催化技术是解决环境污染问题的有效手段,从光催化的催化机理出发,在分析了二氧化钛光催化剂的局限性的基础上,介绍了一种新型的可见光型半导体光催化剂--纳米氧化亚铜,对其制备方法和在光催化剂方面的研究进展作了综述,并对光催化剂的应用及未来研究方向进行了展望.     

Highly active oxide photocathode for photoelectrochemical water reduction

A clean and efficient way to overcome the limited supply of fossil fuels and the greenhouse effect is the production of hydrogen fuel from sunlight and water through the semiconductor/water junction of a photoelectrochemical cell, where energy collection and water electrolysis are combined into a single semiconductor electrode. We present a highly active photocathode for solar H(2) production, consisting of electrodeposited cuprous oxide, which was protected against photocathodic decomposition in water by nanolayers of Al-doped zinc oxide and titanium oxide and activated for hydrogen evolution with electrodeposited Pt nanoparticles. The roles of the different surface protection components were investigated, and in the best case electrodes showed photocurrents of up to -7.6 mA cm(-2) at a potential of 0 V versus the reversible hydrogen electrode at mild pH. The electrodes remained active after 1 h of testing, cuprous oxide was found to be stable during the water reduction reaction and the Faradaic efficiency was estimated to be close to 100%.     

Responsive surface charge transfer doping effect of reductive bio-molecules (glucose, fucoidan, and heparin) contacting on semiconducting titanium oxide films

Titanium oxide films appear to have extensive potentials in various applications largely because of its unique semiconducting properties. Usually, attentions are paid to characterize or tailor their surface electronic states, depending upon specific working circumstances as well as the requirements by their functional performances. Nevertheless, very rarely concern has been taken to the responsive effect on their electronic surface states when they come into contact with surrounding environments, which actually plays an important or even decisive role in their subsequent functions. For instance, cases like biomedical application could normally render the surface sequentially contacting with varying ambient media. In this study, we implemented initial contacting titanium oxide film with three representative bio-molecules (glucose, fucoidan, and heparin), and investigated the responsive effect of charge transfer doping on its electronic properties and its bio-performance. It was shown that the contacting imposed apparently n-type surface-charge-transfer-doping effect on the titanium oxide films. Their surface resistivity increased; their photo-luminance emissions were obviously quenched; their hydrophilic properties were improved; and denaturalization of fibrinogen on the surface was suppressed. Electrons were assigned to inject into titanium oxide film to produce the n-type doping effect. Our finding suggests that the semiconductor biomaterials surface properties and performances might be largely or even decisively influenced by the initial contacting of ambient conditions.     

Study of reactive sputtering titanium oxide for metal-oxide-semiconductor capacitors

Metal oxide semiconductor (MOS) capacitors with titanium oxide (TiO_x) dielectric layer, deposited with different oxygen partial pressure (30, 35 and 40%) and annealed at 550, 750 and 1000 °C, were fabricated and characterized.Capacitance-voltage and current-voltage measurements were utilized to obtain, the effective dielectric constant, effective oxide thickness, leakage current density and interface quality. The obtained TiO_x films present a dielectric constant varying from 40 to 170 and a leakage current density, for a gate voltage of − 1 V, as low as 1 nA/cm² for some of the structures, acceptable for MOS fabrication, indicating that this material is a viable high dielectric constant substitute for current ultra thin dielectric layers.     

Anodization: a promising nano-modification technique of titanium implants for orthopedic applications

Anodization is a well-established surface modification technique that produces protective oxide layers on valve metals such as titanium. Many studies have used anodization to produce micro-porous titanium oxide films on implant surfaces for orthopedic applications. An additional hydrothermal treatment has also been used in conjunction with anodization to deposit hydroxyapatite on titanium surfaces; this is in contrast to using traditional plasma spray deposition techniques. Recently, the ability to create nanometer surface structures (e.g., nano-tubular) via anodization of titanium implants in fluorine solutions have intrigued investigators to fabricate nano-scale surface features that mimic the natural bone environment. This paper will present an overview of anodization techniques used to produce micro-porous titanium oxide structures and nano-tubular oxide structures, subsequent properties of these anodized titanium surfaces, and ultimately their in vitro as well as in vivo biological responses pertinent for orthopedic applications. Lastly, this review will emphasize why anodized titanium structures that have nanometer surface features enhance bone forming cell functions.     

Gas Sensitive Porous Silver-Rutile High-Temperature Schottky Diode on Thermally Oxidized Titanium

The fabrication of porous silver-${rm TiO}_{2}$ gas sensitive Schottky diodes by utilizing thermally grown oxide layer on titanium substrates is described. The junction was formed by the partial sintering of silver particles on the oxidized metal substrate. The connection between titanium metal and its native oxide is ohmic and the substrate performs as a stable back-contact to the oxide semiconductor. For the characterization of the device, electrical contacts were made by connecting silver wires to the titanium substrate and the silver aggregate. Operating at elevated temperatures, the device behaved as a Schottky diode of high junction energy barrier in clean air, while in highly reducing atmospheres the barrier height dropped to zero and the junction was characterized as an ohmic contact. This reversible transition afforded a broad dynamic range and high sensitivity for chemical detection: Operating at 300 $~^{circ}$C, the reverse current of the diode increased by six orders of magnitude in response to the presence of 1 w-% 1-butanol vapor in the surrounding air, and a single diode was able to detect hydrogen in the 50 ppm to 8% concentration range. The observed electronic features of the device were described through a model constructed based on the work function of silver varying from 4.3 to $sim$6.5 eV with oxygen adsorption.      

Transluzente oxidfaserverstärkte Glasmatrix‐Verbundwerkstoffe

Translucent oxide fiber reinforced glasmatrix composites The aim of the work is the developement of transparent glass matrix composites. Therefore besides the mechanical properties also the optical properties of the components have to be adapted. In this study the influence of different fiber coatings (boron nitride, titanium oxide and a boron nitride/titanium oxide double coating) on the mechanical and optical properties of Nextel 440‐fiber reinforced glass was investigated. Micromechanical investigations (push‐in‐tests) and 3‐point‐bending tests have shown the best improvement of the fracture toughness for the binary boron nitride/titanium oxide coating. For single coatings of boron nitride or titanium oxide the transparency was characterized by the transmission spectra.     

Bi2Ti2O7薄膜制备及 Bi2Ti2O7绝缘栅场效应管研制

采用化学溶液沉积法,以硝酸铋和钛酸四丁酯为原料成功地制备了Bi2Ti2O7介质膜。制膜过程简单,成本低廉,得到的薄膜具有良好的绝缘性和较高的介电常数,用其制备的绝缘栅场效应管理与相同尺寸的SiO2绝缘栅场效应管相比,具有较高的跨导和较低的开启电压。