CdS纳米颗粒填充的自支撑多孔硅光致发光特性

为了研究CdS纳米颗粒填充的自支撑多孔硅的光致发光特性,选用电阻率为0.01~0.02Ω·cm的P型硅片,先采用二步阳极氧化法制备自支撑多孔硅,再利用电泳法将CdS纳米颗粒填充入该自支撑多孔硅中.采用扫描电子显微镜、X射线能谱分析、X射线衍射分析、光致发光谱分析对所制备样品的形貌、相结构、组份及发光性能进行研究.实验结果表明:自支撑多孔硅内部成功填充了CdS纳米颗粒,该CdS纳米颗粒衍射峰为(210);CdS纳米颗粒填充的自支撑多孔硅光致发光峰峰位发生红移,且从570nm转移到740nm;电泳时间直接影响CdS纳米颗粒的填充量,导致相关的发光峰强度及发光峰位明显不同.     

紫外-可见光光束在TiO_2纳米颗粒胶体中的传输（英文）

紫外光诱导纳米颗粒胶体射流加工技术利用紫外光场对入射纳米颗粒的催化作用实现对工件表面材料的高效去除。为掌握紫外光诱导纳米颗粒胶体射流加工过程中紫外光束在纳米二氧化钛胶体中的传输特性,基于纳米二氧化钛胶体对紫外-可见光的吸收及散射理论,通过系列实验得到紫外-可见光束在不同浓度、吸收层厚度的二氧化钛纳米颗粒胶体中的传输特性及衰减关系。结果表明,为保证足够强度的紫外光能通过纳米二氧化钛胶体照射在工件表面,胶体浓度宜控制在500mol/m3以下,光-液耦合区胶体吸收层的厚度不宜超过20mm。     

紫外-可见光光束在TiO2纳米颗粒胶体中的传输

紫外光诱导纳米颗粒胶体射流加工技术利用紫外光场对入射纳米颗粒的催化作用实现对工件表面材料的高效去除。为掌握紫外光诱导纳米颗粒胶体射流加工过程中紫外光束在纳米二氧化钛胶体中的传输特性,基于纳米二氧化钛胶体对紫外-可见光的吸收及散射理论,通过系列实验得到紫外-可见光束在不同浓度、吸收层厚度的二氧化钛纳米颗粒胶体中的传输特性及衰减关系。结果表明,为保证足够强度的紫外光能通过纳米二氧化钛胶体照射在工件表面,胶体浓度宜控制在500 mol/m3以下,光-液耦合区胶体吸收层的厚度不宜超过20 mm。     

耐γ辐射匹配层的制备及其在超声换能器的应用*

超声换能器是超声无损检测系统的核心器件。匹配层作为超声换能器的重要组成部分,能减小声阻抗失配造成的声能损失,提高换能器能量传输效率。传统超声换能器由于匹配层等有机材料在射线辐照条件下引起化学键断裂而失效,从而影响检测的准确性。为了研制高性能耐辐射超声换能器,本文选择具有良好耐辐射性能的双酚A型环氧树脂作为基体,氧化铝陶瓷粉末作为无机填料,制备了不同氧化铝含量的匹配层(0%～80%),研究了该系列匹配层样品经过γ射线辐照后的颜色、密度、声速、声阻抗和声衰减的变化情况。随着辐照剂量的增加(0～1000kGy),样品的颜色逐渐加深,密度几乎保持不变;声速,声阻抗和声衰减略有提高。基于该匹配层,研制了中心频率9MHz的超声换能器,换能器辐照前后信号变化不大,表明该系列匹配层在较大剂量辐照下仍然具有良好的声学性能,是较为优异的耐辐射匹配层材料,具有较好的应用前景。     

凹凸棒石/硅橡胶复合材料的热氧化降解和老化性能研究（英文）

本文采用高压均质结合对辊挤压工艺对天然凹凸棒石进行棒晶解离得到了纯度较高和比表面积较大(133.7 m2/g)的纳米解离凹凸棒石.进一步通过机械共混法分别将天然凹凸棒石和纳米解离凹凸棒石与硅橡胶生胶复合制备了天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶材料,研究了天然凹凸棒石和纳米解离凹凸棒石对凹凸棒石/硅橡胶复合材料热氧化降解和老化性能的影响.结果表明,天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶在300℃热氧老化处理0.5 h后,相比于纯硅橡胶,初始5%失重温度从385℃提高至396～399℃.系列表征结果表明,天然凹凸棒石和纳米解离凹凸棒石增强了纳米粒子与硅橡胶之间的相互作用从而抑制了纳米颗粒聚集,并且可显著提高硅橡胶侧链Si-CH_3的保存率,从而提高了该复合材料的热氧化降解和老化性能.此外,纳米解离凹凸棒石可大大抑制纳米粒子的长大;因此老化后,纳米解离凹凸棒石-硅橡胶表现出了比硅橡胶(10.6%、7.4%和5.0%)更高的拉伸强度、断裂伸长率和撕裂强度保留率(40.6%、34.9% 和30.1%).     

石墨烯与纳米颗粒协同提高复合体系热导率

本文详细阐述了石墨烯和球形纳米颗粒间提高复合物热导率的协同效应。石墨烯和纳米颗粒在复合物中可形成紧密堆积结构,该结构阻止了石墨烯的团聚。二维的石墨烯能够在纳米颗粒之间架桥,为复合体系提供了更加有效的声子传输通道,降低了界面热阻。当石墨烯添加量为质量分数1.0%时,导热硅脂的热导率达到了3.45 W/(m·K),EVA复合材料的热导率达到了2.41 W/(m·K);在PC/ABS基体中,石墨烯添加质量分数0.5%时,热导率达到3.11 W/(m·K);在环氧树脂基体中,当负载银的石墨烯填充量为质量分数5.0%时,热导率到达了0.95 W/(m·K)。     

基于微纳结构及材料特性的光场调控模拟研究

利用时域有限差分算法（FDTD）对微纳结构靶的光场分布进行仿真模拟,探究微纳结构靶中的光传输机制,分析材料特性和结构参数对光传输特性和光场分布的影响。基于光场分布及演化的仿真模拟结果,对比半导体氧化铝、绝缘体二氧化硅和金属铜三种导电性不同的材料上纳米线和纳米孔阵列微纳结构靶的激光传输特性,分析光传输过程中的光场分布变化。研究结果表明,通过改变氧化铝和二氧化硅纳米孔（线）阵列结构靶中孔洞（纳米线）直径和间距等结构参数,可以实现对微纳结构靶中光传输特性和光场分布的调制,实现光场在介质材料和真空区域间的周期振荡分布,或是以一种稳定形态传输;激光在铜纳米孔阵列中传输时,透光性随孔洞半径的增加而增加。基于光场分布及演化的仿真模拟结果,对比不同材料、不同微纳结构靶的激光传输演化特性,给出物理图像及对应现象规律,根据光场调控需求,给出微纳结构靶设计。     

凹凸棒石/硅橡胶复合材料的热氧化降解和老化性能研究

本文采用高压均质结合对辊挤压工艺对天然凹凸棒石进行棒晶解离得到了纯度较高和比表面积较大(133.7 m²/g)的纳米解离凹凸棒石. 进一步通过机械共混法分别将天然凹凸棒石和纳米解离凹凸棒石与硅橡胶生胶复合制备了天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶材料,研究了天然凹凸棒石和纳米解离凹凸棒石对凹凸棒石/硅橡胶复合材料热氧化降解和老化性能的影响. 结果表明,天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶在300 oC热氧老化处理0.5 h后,相比于纯硅橡胶,初始5%失重温度从385 oC提高至396∽399 oC. 系列表征结果表明,天然凹凸棒石和纳米解离凹凸棒石增强了纳米粒子与硅橡胶之间的相互作用从而抑制了纳米颗粒聚集,并且可显著提高硅橡胶侧链Si-CH₃的保存率,从而提高了该复合材料的热氧化降解和老化性能. 此外,纳米解离凹凸棒石可大大抑制纳米粒子的长大;因此老化后,纳米解离凹凸棒石-硅橡胶表现出了比硅橡胶(10.6%、7.4%和5.0%)更高的拉伸强度、断裂伸长率和撕裂强度保留率(40.6%、34.9% 和30.1%).     

垂直载荷下湿玻璃珠样品的声速和衰减测量及非线性声学响应

为了分析垂直载荷下颗粒物质的声速、声衰减系数、谐波非线性等特性,本工作采用飞行时间法测量了不同含水量下声速随压强的变化规律,并利用傅里叶变换法分析了干、湿玻璃珠样品的声衰减和非线性声学特性。结果表明:干、湿玻璃珠样品中的声速、声衰减系数以及谐波非线性均随压强呈幂律变化;湿颗粒样品中随着液体含量增多,声速逐渐增加,超声波透过湿颗粒样品时的能量耗散和非线性逐渐减小。分析原因表明,压强和孔隙流体改变了颗粒之间的接触分布,使得颗粒体系的声速、声衰减以及谐波非线性等特性都随之发生变化。     

气泡对沉积物声学特性影响研究:以东海沉积物为例

气泡对海底沉积物的声学物理特性的影响在海洋学、海洋地质学和海洋地球物理学等领域中都有着重要的研究意义. 利用Micro-CT扫描仪对沉积物样品进行无损检测扫描, 根据沉积物样品中水、气和固体颗粒对X射线吸收率的不同, 提取了沉积物的气体体积(气泡)含量. 利用智能非金属超声检测仪对沉积物样品进行超声无损测定, 得到沉积物声速与衰减. 通过回归分析, 建立了样品采集海域沉积物孔隙填充气体与流体含量与沉积物声学特性之间的相关关系. 结果表明: 含气量的少许增大就会引起声速的急剧降低和声衰减的急剧上升, 但含气量超过10%后, 这种上升和降低的幅度明显减小.     

Preparation and atomic oxygen erosion resistance of silica film formed on silicon rubber by sol-gel method

Based on the characteristic that silicon coupling agents have the capability to develop ‘molecular bridge’ in the interface of organic materials and inorganic materials, silica films were prepared on the surface of flexible silicon rubber by sol-gel method and the optical transmittance of the sample before and after atomic oxygen irradiation was tested. The surface morphology and structure of silica films were investigated by scanning electronic microscope (SEM) and Fourier transformed infrared spectroscopy (FTIR). The results indicated that the silica sol could easily form a uniform thin film on the surface of silicon rubber pretreated by high concentration silicon coupling agents, and the inorganic silica films could combine with organic silicon rubber without obvious delamination on the interface.     

Synthesis and characterization of polyester bionanocomposite membrane with ultrasonic irradiation process for gas permeation and antibacterial activity

Optically active bionanocomposite membranes composed of polyester (PE) and cellulose/silica bionanocomposite (BNCs) prepared with simple, green and inexpensive ultrasonic irradiation process. It is a novel method to enhance the gas separation performance. The novel optically active diol containing functional trifluoromethyl groups was prepared in four steps reaction and it was fully characterized by different techniques. Commercially available silica nanoparticles were modified with biodegradable nanocellulose through ultrasonic irradiation technique. Transmission electron microscopy (TEM) analyses showed that the cellulose/silica composites were well dispersed in the polymer matrix on a nanometer scale. The mechanical properties nanocomposite films were improved by the addition of cellulose/silica. Thermo gravimetric analysis (TGA) data indicated an increase thermal stability of the PE/BNCs in compared to the pure polymer. The results obtained from gas permeation experiments showed that adding cellulose/silica to the PE membrane structure increased the permeability of the membranes. The increase in the permeability of the gases was as follows: P_CH4 (38%) <P_N2 (58%) <P_CO2 (88%) <P_O2 (98%) Adding silica nanoparticles into the PE matrix, improved the separation performance of carbon dioxide/methane and carbon dioxide/nitrogen gases. Increasing the cellulose/silica mass fraction in the membrane increased the diffusion coefficients of gases considered in the current study. Further, antimicrobial test against pathogenic bacteria was carried out.     

Study of magnetite nanoparticle suspensions by photometry and NMR relaxometry

A method has been described for preparation of suspensions of magnetite nanoparticles stabilized by porous silicon dioxide. The process of sedimentation of nanoparticles in suspensions of different compositions and concentrations has been analyzed by transmission coefficient measurements. Spectra of the transmission coefficient have been obtained for suspensions containing composite nanoparticles, the initial silicon dioxide, and macroscopic magnetite particles. The average effective radius of nanoparticles has been calculated from the time dependences of the transmission coefficient. It has been demonstrated that the synthesized nanoparticles possess magnetic-resonance contrast properties.     

Design and Dynamics Investigation for a Silicone Rubber Shock Absorber

A new kind of coupling-type silicone rubber shock absorber was prepared. Vibration and static stiffness tests were carried out to investigate the characteristics of vibration control. A mechanical model of the shock absorber was established, and the working principle of the shock absorber was studied by comparing the vibration test with simulation results. The dynamic results show the shock absorber has excellent vibration control performance. The coupling characteristics originate from the contact of inner and outer silicone rubber. It is shown that the stiffness and damping coefficients in the coupling process are critical for vibration control of the shock absorber.     

质子辐照对MQ硅树脂增强的加成型硅橡胶质损及热性能的影响

 采用空间综合辐照模拟设备研究了100 keV和150 keV能量的质子辐照对MQ硅树脂增强的加成型硅橡胶的损伤及其对硅橡胶热性能的影响。试验结果表明：质子辐照后,硅橡胶表面出现损伤裂纹,随辐照能量和剂量的增加,裂纹的数量增多,裂纹增大;质子辐照后,硅橡胶的质量有所损失,其质损率随辐照能量和剂量的增加而增加;质子辐照后硅橡胶的耐热性随辐照剂量的增加先略有增加而后下降,经辐照后的硅橡胶在玻璃态和玻璃转变区的温度区间内收缩率降低,而在高弹态的温度区间内膨胀率增加。     

Analysis and identification for the electromagnetic ultrasonic interfacial echoes using instantaneous spectrum and artificial neural network

The proper frequency is experimentally chosen to be the operation frequency of the electromagnetic acoustic transducer. The instantaneous amplitude, phase and frequency of the detected ultrasonic echoes from a multilayer adhesive sample of steel and rubber materials are calculated and composed to form three-dimensional instantaneous spectrum which is successful to distinguish the testing signals from different adhesive states qualitatively. Then, average instantaneous parameters in sensitive time window are picked up and used as the input eigenvectors for the BP artificial neural network. Identified results in both training and testing volumes demonstrate that the detected electromagnetic ultrasonic interracial echoes can be identified and classified automatically with the correctness ratio larger than 95%.     

Photochemical welding of silica microspheres to silicone rubber by ArF excimer laser

Transparent fused silica (SiO₂) microspheres 2.5 μm in diameter were photochemically welded to transparent, flexible silicone rubber ([SiO(CH₃)₂]_n) substrate by 193 nm ArF excimer laser induced photochemical modification of silicone into silicon oxide. Single layer of silica microspheres was easily formed on an adhesive silicone rubber before laser irradiation after dropping of silica microspheres dispersed in ethanol and subsequent tape peeling. The welding rate, the percentage of welded microspheres tested by ultrasonic cleaning with ethanol, was examined by varying the single pulse fluence and irradiation time of ArF excimer laser. The welding layer underneath microsphere, silicon oxide, was also found to emit white light of strong intensity under UV light illumination.     

基于有限元模拟的超声应力系数标定及分析*

应力系数的标定作为超声应力检测最为关键的环节,直接决定应力检测结果的准确性。传统的应力系数试验标定对于被测物的表面粗糙度、耦合剂厚度、声匹配块与被测物接触力等因素十分敏感,但缺少基本参照值。基于COMSOL建立多物理场耦合的超声应力检测模型,施加不同的拉伸载荷,计算临界折射纵波到达时间与不同应力值之间的关系,模拟标定45#钢的超声应力系数为13.7MPa/ns。单轴水平拉伸试验标定的45#钢应力系数为16.5MPa/ns。结果表明,通过两种方法标定的应力系数较为接近,试验标定的应力系数偏大,这是由于有限元方法能够消除试验过程中各种不确定因素对声时精确测量所造成的影响,能够更加纯粹的反映材料的声弹性效应,因此具有作为基础数据的参考价值。有限元方法作为传统试验方法的补充,可以减小试验标定数据的离散性,提高超声应力检测结果的可信度。     

Determination of acoustic impedances of multi matching layers for narrowband ultrasonic airborne transducers at frequencies <2.5 MHz - Application of a genetic algorithm

The effective ultrasonic energy radiation into the air of piezoelectric transducers requires using multilayer matching systems with accurately selected acoustic impedances and the thickness of particular layers. One major problem of ultrasonic transducers, radiating acoustic energy into air, is to find the proper acoustic impedances of one or more matching layers. This work aims at developing an original solution to the acoustic impedance mismatch between transducer and air. If the acoustic impedance defences between transducer and air be more, then finding best matching layer(s) is harder. Therefore we consider PZT (lead zirconate titanate piezo electric) transducer and air that has huge acoustic impedance deference. The vibration source energy (PZT), which is used to generate the incident wave, consumes a part of the mechanical energy and converts it to an electrical one in theoretical calculation. After calculating matching layers, we consider the energy source as layer to design a transducer. However, this part of the mechanical energy will be neglected during the mathematical work. This approximation is correct only if the transducer is open-circuit. Since the possibilities of choosing material with required acoustic impedance are limited (the counted values cannot always be realized and applied in practice) it is necessary to correct the differences between theoretical values and the possibilities of practical application of given acoustic impedances. Such a correction can be done by manipulating other parameters of matching layers (e.g. by changing their thickness). The efficiency of the energy transmission from the piezoceramic transducer through different layers with different thickness and different attenuation enabling a compensation of non-ideal real values by changing their thickness was computer analyzed (base on genetic algorithm). Firstly, three theoretical solutions were investigated. Namely, Chebyshev, Desilets and Souquet theories. However, the obtained acoustic impedances do not necessarily correspond to a nowadays available material. Consequently, the values of the acoustic impedances are switched to the nearest values in a large material database. The switched values of the acoustic impedances do not generally give efficient transmission coefficients. Therefore, we proposed, in a second step, the use of a genetic algorithm (GA) to select the best acoustic impedances for matching layers from the material database for a narrow band ultrasonic transducer that work at frequency below the 2.5 MHz by considering attenuation. However this bank is rich, the results get better. So the accuracy of the propose method increase by using a lot of materials with exact data for acoustic impedance and their attenuation, especially in high frequency. This yields highly more efficient transmission coefficient. In fact by using increasing number of layer we can increase our chance to find the best sets of materials with valuable both in acoustic impedance and low attenuation. Precisely, the transmission coefficient is almost equal to unity for the all studied cases. Finally the effect of thickness on transmission coefficient is investigated for different layers. The results showed that the transmission coefficient for air media is a function of thickness and sensitive to it even for small variation in thickness. In fact, the sensitivity increases when the differences of acoustic impedances to be high (difference between PZT and air).