半导体纳米光功能材料的合成方法

本文以硫属半导体纳米材料的合成为例，综合了纳米光功能材料的合成方法，各种方法的特点和今后的发展方向。     

人工光合成体系高效产氢

<正>日前,中科院理化所借鉴自然界光合作用的机制和过程,通过人工光合成途径,将太阳能转化为化学能,特别是氢能,为开发和利用太阳能并逐步解决能源短缺和环境污染问题开辟了新道路。科研人员首次利用量子点和廉价金属盐,通过可见光催化协助的方法,原位构筑了具有空腔结构     

无机基有机复合光功能材料的研究进展

无机基有机复合光功能材料研究是近十年发展起来的信息材料研究的新领域和热点,本文系统总结、评述了无机基有机复合光功能材料及其相关技术的进展、前景和面临的局限及其解决思路。     

日启动人工光合成化学基础技术开发

据报道,日本人工光合成化学工艺技术研究组合（ARPChem）12月113成立“清洁可持续化学工艺基础技术开发（革新性催化剂）”项目,利用能被阳光激发活性的光催化剂,把水分解成氢气和氧气,并用氢分离膜对获得的氢气和氧气进行高纯度分离处理,进而合成碳数为2～4的烯烃类原料（乙烯、丙烯等）,用作塑料原料。同时,利用新催化剂将二氧化碳变为一氧化碳等。在上述这些反应中,各种高功能及高性能催化剂的实用化是关键。     

光波导放大器用材料的研究进展

回顾了3种光放大器的工作原理、应用现状,分析了4类主要的光波导放大器用材料的性能、特点和研究现状.分析表明,非氧化物玻璃和硅基光波导材料对研制光波导放大器有很好的应用潜力.     

新一代磁光材料及器件研究进展

磁光材料是典型的多功能材料,其应用频率覆盖了射频、微波、毫米波、THz波和光波段,是一类优秀的全波段材料.首先对磁光材料发展的动态进行了分析;其次就磁光材料应用于磁光盘、光纤通信器件、THz器件等进行了讨论;最后,对作者课题组的一些新的研究工作做了介绍,以期能对这一领域的发展起到促进作用.     

上转换发光材料的合成与应用

综述了目前国内外上转换发光材料的几种合成方法,包括传统的高温固相合成法、溶胶一凝胶法、水热合成法、共沉淀法等.总结了不同方法的优缺点,对上转换材料合成方法的发展进行了展望.并介绍了上转换技术的一些应用.     

光声光谱测试技术及在材料分析中的应用

光声光谱作为一种比较新型的材料无损测试技术,具有灵敏度高、能进行微量分析、以及不受样品形状限制等优点。本文对光声光谱测试技术的测试原理及测试系统组成进行了详细说明,并举例说明其在材料分析中的应用。     

红外上转换纳米发光材料的水热合成

利用稀土离子Y~(3+)、Yb~(3+)、Er~(3+)与乙二胺四乙酸形成的配合物,加入可溶性氟化物.控制溶液的pH值,利用配位-沉淀平衡体系制备了复合氟化物纳米粒子前驱物,在240℃下水热晶化前驱物,合成了红外上转换纳米发光材料.     

A study of parameters affecting the continuous CO2 laser cuts

Abstract

This work attempts to discover, by experimentation, some of the parameters governing cutting efficiency in perspex of a continuous CO₂ laser. The experimentation took the form of taking cuts in specimen pieces with the laser. While varying the parameters of speed of cut and position of the focal plane of the laser beam relative to the surface of the perspex, all other parameters were kept constant. These experiments produced conclusive ideas of the optimum position of the focal plane and the best speeds for cutting perspex at the same time producing the best cut quality obtainable. When the theoretically predicted minimum cut width is compared with the experimentally obtained results, the agreement is found to be almost exact.     

A study of uv preionization pulsed tea CO2 laser

Abstract

A uniform volumetric discharge was obtained by means of an auxiliary UV preionization in a home‐made TEA CO₂ laser. The maximum output pulse energy of this laser system was about 12J per pulse with a pulse duration of 80 ns. The ratio of electric field to neutral particle density (E/N) in this laser was 7.6×10^‐16 V cm². The peak power and pulse shape of the laser were studied. The time delay between the predischarge and the maindischarge during the stable operation of this laser system has also been studied. It was observed that the laser was operating with uniform glow discharges when the time delayed between the predischarge and the maindischarge was in the range of 1.0 μs to 6.0 μs. The spark array used as a preionizer for producing the UV radiation in this system is new, simple, durable, and can be easily fabricated.     

Fabrication of hydrophilic paclitaxel-loaded PLA-PEG-PLA microparticles via SEDS process

In this work, chemically bonded poly(D, L-lactide)-polyethylene glycol-poly(D, L-lactide) (PLA-PEG-PLA) triblock copolymers with various PEG contents and PLA homopolymer were synthesized via melt polymerization, and were confirmed by FTIR and ¹H-NMR results. The molecular weight and polydispersity of the synthesized PLA and PLA-PEG-PLA copolymers were investigated by gel permeation chromatography. Hydrophilicity of the copolymers was identified by contact angle measurement. PLA-PEG-PLA and PLA microparticles loaded with and without PTX were then produced via solution enhanced dispersion by supercritical CO₂ (SEDS) process. The effect of the PEG content on the particle size distribution, morphology, drug load, and encapsulation efficiency of the fabricated microparticles was also studied. Results indicate that PLA and PLA-PEG-PLA microparticles all exhibit sphere-like shape with smooth surface, when PEG content is relatively low. The produced microparticles have narrow particle size distributions and small particle sizes. The drug load and encapsulation efficiency of the produced microparticles decreases with higher PEG content in the copolymer matrix. Moreover, high hydrophilicity is found when PEG is chemically attached to originally hydrophobic PLA, providing the produced drug-loaded microparticles with high hydrophilicity, biocompatibility, and prolonged circulation time, which are considered of vital importance for vessel-circulating drug delivery system.     

Clover leaf-shaped Al2O3 extrudate as a support for high-capacity and cost-effective CO2 sorbent

Amine-functionalized clover leaf-shaped Al₂O₃ extrudates (CA) were prepared for use as CO₂ sorbent. The as-synthesized materials were characterized by N₂ adsorption, XRD, SEM and elemental analysis followed by testing for CO₂ capture using simulated flue gas containing 15.1% CO₂. The results showed that a significant enhancement in CO₂ uptake was achieved with the introduction of amines into CA materials. A remarkably high volume-based capacity of 70.1 mg/mL of sorbent of this hybrid material suggests that it can be potentially used for CO₂ capture from flue gases and other stationary sources, especially those with low CO₂ concentration. The novel adsorbent reported here performed well during prolonged cyclic operations of adsorption-desorption of CO₂.     

Fast adiabatic heating and temperature relaxation in near-critical fluids under zero gravity

Heat transport in supercritical CO₂ is studied under microgravity conditions. A large temperature and density region around the critical point is explored (CO₂ cells were filled at critical density= _c and off-critical densities= _c±0.18 _c). Local heating is obtained by using a small thermistor located in the bulk fluid. Through interferometric observations, a new mechanism of thermalization has been evidenced. Thermal expansion of a warm diffusing boundary layer around the heating thermistor is responsible for rapid adiabatic heating of the bulk fluid through the emission of pressure waves at the border. The scaled thickness of the thermal boundary layer follows a power law. When the heat flow stops, the bulk adiabatic heating instantaneously vanishes and the temperature relaxation inside the thermal boundary layer follows locally a diffusive process.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

CO2 + R23 Binary System: Virial Coefficients Derived from Burnett Measurements

Burnett PVT measurements were performed on trifluoromethane (R23) and mixtures of R23 with carbon dioxide (CO₂). The Burnett apparatus was calibrated using helium. Fourteen expansions were performed for 5 isotherms and in a pressure range from 130 kPa to 6 MPa for R23. Second and third virial coefficients were derived from the collected data and compared with literature values; good agreement was found between them. PVTx measurements for the binary CO₂+R23 system were carried out for five isotherms (303, 313, 323, 333, and 343 K). In all, 18 runs were performed in a pressure range from 150 kPa to 5.9 MPa. The composition of the mixtures was measured with a gas chromatograph after it had been calibrated using samples prepared gravimetrically. Second and third virial coefficients for the system were derived, together with the second and third cross virial coefficients, from experimental results using virial coefficients for CO₂ from previous measurements (for the same sample as used in the present study). Samples for composition measurements were collected during the first Burnett expansion. Second virial coefficients for the system showed positive deviations from ideal values, while the third virials were negative. No previous experimental results were found for the PVTx properties of this binary system.