纳米CeO2粉体的制备及其发光性能研究

以氨水和硝酸铈为反应原料,采用沉淀滴定法制备了纳米CeO2粉体,通过XRD、SEM、TEM等手段对其进行了结构表征和形貌分析;考察了不同溶剂、煅烧温度等对其颗粒尺寸的影响;应用荧光光谱法测试了其发光光谱,首次探讨了纳米CeO2粉体的发光性能。结果表明,前驱体经过300～700℃煅烧后可以得到颗粒尺寸为4-30nm的立方萤石结构CeO2晶体,其形貌接近于球形。在无水乙醇溶剂中得到的纳米CeO2颗粒分散较好,其颗粒尺寸随煅烧温度的升高而增大。纳米CeO2粉体具有良好的蓝光发光性能,在276nm的激发波长作用下,其发射光谱的最大峰值为473nm。     

纳米多壁碳管结构变化对其复合材料微波性能影响

采用不同温度热处理纳米多壁碳管,研究纳米多壁碳管结构变化对相应复合材料的微波特性的影响.采用拉曼光谱分析表征纳米多壁碳管热处理前后的结构变化;测试纳米多壁碳管/石蜡复合材料在0.5 ～ 6GH介电谱.结果显示,热处理温度≤1000℃,纳米多壁碳管的ID/IG值基本不变,相应复合材料的复介电常数大致相等且吸波性能基本相同;热处理温度＞ 1000℃,ID/IG值明显减小,内部结构发生重排,纳米多壁碳管平均晶粒尺寸增大,相应的纳米多壁碳管复合材料的复介电常数无论实部还是虚部均明显下降,微波吸收峰向高频移动.通过热处理控制纳米多壁碳管的ID/IG值和平均晶粒尺寸,可以调整纳米多壁碳管复合材料的微波介电谱,达到调整纳米多壁碳管复合材料的微波吸收特性的目的.     

吸收剂颗粒尺寸对吸波材料性能的影响

对最佳的吸收剂颗粒粒度进行数值计算和分析。从趋肤效应和单个磁畴颗粒大小两个角度,以纯铁粉为例对最佳的粒度做了分析,结果表明,对于2~18 GHz的雷达波,铁粉颗粒在16 nm~1μm为好。还分析了利用纳米颗粒的量子尺寸效应来吸收电磁波时颗粒的尺寸范围,计算结果表明,此时颗粒尺寸至少应小于22 nm。     

相变材料微胶囊表面吸附纳米颗粒对传热过程的影响

通过对相变材料微胶囊、纳米颗粒和基液之间传热过程的仿真计算,分析了纳米颗粒的数目、粒径和热导率对微胶囊与流体之间传热Nu的影响.进而采用数值方法研究了吸附纳米颗粒后,微胶囊-流体传热系数的提高对相变过程的影响,研究结果为纳米颗粒的强化传热机制提供了部分理论依据.      

底部封闭竖直细管内纳米流体的沸腾特性和临界热通量

以水-氧化铜纳米颗粒组成的纳米流体为工质, 对底部封闭细小圆管内的沸腾特性以及临界热通量进行了实验研究.结果表明:沸腾时管内纳米流体的浓度不随加热时间长短而改变, 沸腾液体的纳米颗粒除微量吸附在管壁外, 其余全部被蒸汽携带走, 同时吸附层厚度到了一定程度就不再变化.相对于纯水而言, 随着纳米浓度的增加, 纳米流体的沸腾特性有所劣化, 这主要是因为纳米颗粒吸附在管壁上, 减小了壁面粗糙度, 从而减小了液体和壁面的接触角.随着纳米浓度的增加, 纳米流体的临界热通量也随之增加.纳米流体的临界热通量不仅与管长与管径比有关, 而且还与纳米浓度有关.      

Al_2O_3-ZrO_2-MgAl_2O_4三元纳米复相陶瓷的微观组织和力学性能

采用溶胶-凝胶法制备Al2O3-ZrO2-MgAl2O4纳米复合粉体.利用真空热压烧结技术制备了Al2O3-30mol%ZrO2-30mol%MgAl2O4(AZ30S30)三元纳米复相陶瓷.微观组织研究表明:所得纳米复相陶瓷是一种典型的"晶间/晶内"复合型纳米结构,基体氧化铝和第二相均为等轴状,氧化铝晶间散布着氧化锆和尖晶石第二相晶粒,同时有大量的球形氧化锆小颗粒分散在基体氧化铝晶粒内.对不同晶粒尺度复相陶瓷的断裂韧性测试及纳米压痕实验表明:微米级复相陶瓷的最大硬度为22GPa,而纳米复相陶瓷具有更好的力学性能,其硬度随着晶粒尺寸的减小而增加,最大可达35GPa.微米级复相陶瓷的断裂韧性为8.9MPa·m1/2,而纳米复相陶瓷的断裂韧性为10.04MPa·m1/2,其增韧机理主要为ZrO2相变复合增韧、"内晶"型纳米颗粒韧化以及细晶韧化.     

微纳结构CoCrFeNi基高熵合金粉末冶金制备及强韧化机理研究

针对CoCrFeNi基高熵合金强塑性失配问题,提出了基于高能球磨、放电等离子体烧结和热挤压相结合的粉末冶金制备方法,探究了制备工艺参数对晶粒尺寸、第二相颗粒和孪晶组织演变的影响规律,分别制备出由粗晶、细晶和纳米颗粒构成的多尺度异构CoCrFeNiMnTi_0.2高熵合金,以及包含超细晶、纳米颗粒和纳米孪晶的CoCrFeNiMnTi_0.2高熵合金。拉伸力学性能显示,两种高熵合金屈服强度和断后伸长率分别高达1298 MPa和13%,以及1507MPa和7%,均实现了较好的强塑性均衡。最后,基于对霍尔佩奇系数修订,建立了纳米颗粒增强超细晶CoCrFeNi基高熵合金强化模型,揭示了纳米颗粒与微纳异构组织耦合强韧化机制,以及超细晶、纳米颗粒与纳米孪晶协同强韧化机理,并进一步发现纳米孪晶能够增加高熵合金流变应力,使新的变形孪晶形核,从而诱发多级变形行为。     

纳米流体在圆管型丝网热管换热强化中的应用

对纳米流体强化水平放置的丝网热管换热特性进行了实验研究.实验工质为水基CuO纳米流体,颗粒平均粒径50 nm,质量分数为0.5%～2.0%.实验在定压下进行,压力为7.45～19.97 kPa.结果显示,纳米流体替代去离子水后,热管换热性能大幅度提高.蒸发段换热系数提高了170%～410%.运行压力对热管换热特性有明显影响.压力越小,热管换热的强化越显著.热管换热特性随纳米流体质量分数的增加而提高,到达一定值后开始随之下降,最佳质量分数在1.0%左右.      

纳米SiC增强碳纤维层合板摩擦磨损性能

为了探寻一种简便的制备纳米SiC增强碳纤维层合板的方法,本文将纳米SiC颗粒均匀分散在无水乙醇中,制备成不同质量分数的SiC试剂,然后均匀喷涂在碳纤维预浸料表面,固化成型。对不同试件进行摩擦磨损实验,得到不同含量的纳米SiC颗粒对碳纤维层合板摩擦因数、磨损量的影响规律,并且对磨损形貌和复合材料的硬度进行分析。实验结果表明：在碳纤维预浸料表面喷涂纳米SiC颗粒能够有效改善碳纤维层合板的摩擦磨损性能;当纳米SiC浓度为1%时,层合板的摩擦因数、磨损量、磨痕的宽度及深度较于不含纳米SiC的层合板分别降低52%,63%,32.3%,54.8%,摩擦磨损性能最好。     

纳米锑颗粒的制备及其分散性研究

采用电化学方法电沉积制得不同形貌及粒径的纳米锑颗粒,并在制备过程中使用OP-10对纳米锑颗粒表面进行了原位改性.通过TEM、XRD、FTIR等方法对纳米锑颗粒的形态、物相和包覆效果进行表征.结果显示,纳米锑颗粒的制备具有时间效应和电流效应.随着反应时间的加长,纳米锑颗粒粒径变大,且在某种程度上存在着团聚现象;电流密度在一定范围内,适当增大电流密度有利于纳米锑颗粒的形成.纳米锑颗粒的表面改性,主要是通过OP-10的长链分子结构与纳米锑颗粒之间的化学吸附以及OP-10的长链烷基分子之间的氢键、范德华力相互作用,分子链相互缠结,部分通过C-H键互相渗入,最终有效地包覆在纳米锑颗粒表面来达到其表面改性效果,同时在反应过程中醚键也起了一定作用.纳米锑颗粒在纯液体石蜡油中的分散稳定性能与其添加量有关,其最佳添加量为0.5％.     

Orion-2: First scientific results

The ultraviolet spectral images of thousands of faint stars, up to the 13th mag., in the wavelength region of 2000–5000 Å are obtained by means of the space astrophysical observatory Orion-2 aboard the spaceship Soyuz-13. These spectrograms were designed generally for an investigation of the continuous spectra of the stars in ultraviolet. The processing and measurement of part of the material available confirm the expectations for the solution of a large number of problems concerning the physics of stars and stellar atmospheres. Some of the results obtained are included in the present review. Particularly, the observed distribution of continuous energy in the ultraviolet of normal hot stars is in line, according to Orion-2 data, with theoretical prediction; the existence of a new type of high temperature (> 20000K) and low absolute luminosity stars is noticed; the blocking effect of the ultraviolet absorption lines expected for the A-type stars is confirmed; a number of empirical regularities concerning the behaviour of the ultraviolet doublet of ionized magnesium, 2800 Mg ii, in the stellar spectra are derived; the chromosphere in cold stars is detected; the role of a multiplet of ionized titanium, 3080 Ti ii, in stellar spectra is revealed; probably an abnormal silicon-rich stellar envelope around a Be-type star is discovered; a new method for the spectral classification of the stars by their ultraviolet spectral images is developed; a range of interesting facts relating to the structure of the ultraviolet spectra of middle type stars (F-K) come to the fore; an exceptional ultraviolet spectrogram for the planetary nebula II 2149 and its nuclei is obtained; the blocking effect of emission lines in the spectrum of the B-type emission and normal O-type stars has been detected; a remarkably faint (12^itm.6) and high temperature star (No. 1) of strange spectral structure has been discovered.     

Development of a 1m-normal-incidence-EUV telescope

Astrophysical plasmas at temperatures in the range (0.5–5)×10⁵ K that occur e.g. in interstellar space, in the extended atmospheres around stars of essentially all spectral types, including the numerous late-type stars with low photospheric temperatures, and in the atmospheres of highly evolved stars, can best be studied at extreme ultraviolet wavelengths where they release the bulk of their energy. We report here the current development status of a 1m-normal-incidence-EUV-telescope that will be flown on an ARIES rocket to observe the spectra of nearby stars in the 350 – 700 mm range.     

Prediction of shock-layer ultraviolet radiation for hypersonic vehicles in near space

A systemic and validated model was developed to predict ultraviolet spectra features from the shock layer of near-space hypersonic vehicles in the ‘‘solar blind" band region. Computational procedures were performed with 7-species thermal non-equilibrium fluid mechanics, finite rate chemistry, and radiation calculations. The thermal non-equilibrium flow field was calculated with a two-temperature model by the finite volume technique and verified against the bow-shock ultra-violet(BSUV) flight experiments. The absorption coefficient of the mixture gases was evaluated with a line-by-line method and validated through laboratory shock tube measurements. Using the line of sight(LOS) method, radiation was calculated from three BSUV flights at altitudes of 38,53.5 and 71 km. The investigation focused on the level and structure of ultraviolet spectra radiated from a NO band system in wavelengths of 200–400 nm. Results predicted by the current model show qualitative spatial agreement with the measured data. At a velocity of 3.5 km/s(about Mach11), the peak absolute intensity at an altitude of 38 km is two orders of magnitude higher than that at 53.5 km. Under the same flight conditions, the spectra structures have quite a similar distribution at different viewing angles. The present computational model performs well in the prediction of the ultraviolet spectra emitted from the shock layer and will contribute to the investigation and analysis of radiative features of hypersonic vehicles in near space.     

加入纳米颗粒的相变悬浮液黏性和热导率特性

提出了在相变悬浮液中添加TiO2纳米颗粒以提高其热导率的概念,并使用旋转流变仪和热物性仪测量了这种新型悬浮液流变特性和热导率。研究结果表明,对于体积浓度为10%的相变悬浮液,当加入的纳米颗粒质量浓度不超过5%(体积浓度1.18%)时,低剪切率下悬浮液表现出非牛顿流体的特性,高剪切率下仍可视为牛顿流体。相变悬浮液的黏性随纳米颗粒浓度增加而增加,当纳米颗粒质量浓度为5%时,相变悬浮液的黏性提高约23%。相变悬浮液的热导率随着纳米颗粒浓度的增加而增加,当纳米颗粒质量浓度为5%时,相变悬浮液热导率提高约7.3%。     

The Mercury Atmospheric and Surface Composition Spectrometer for the MESSENGER Mission

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) is one of seven science instruments onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft en route to the planet Mercury. MASCS consists of a small Cassegrain telescope with 257-mm effective focal length and a 50-mm aperture that simultaneously feeds an UltraViolet and Visible Spectrometer (UVVS) and a Visible and InfraRed Spectrograph (VIRS). UVVS is a 125-mm focal length, scanning grating, Ebert-Fastie monochromator equipped with three photomultiplier tube detectors that cover far ultraviolet (115–180 nm), middle ultraviolet (160–320 nm), and visible (250–600 nm) wavelengths with an average 0.6-nm spectral resolution. It will measure altitude profiles of known species in order to determine the composition and structure of Mercury’s exosphere and its variability and will search for previously undetected exospheric species. VIRS is a 210-mm focal length, fixed concave grating spectrograph equipped with a beam splitter that simultaneously disperses the spectrum onto a 512-element silicon visible photodiode array (300–1050 nm) and a 256-element indium-gallium-arsenide infrared photodiode array 850–1,450 nm. It will obtain maps of surface reflectance spectra with a 5-nm resolution in the 300–1,450 nm wavelength range that will be used to investigate mineralogical composition on spatial scales of 5 km. UVVS will also observe the surface in the far and middle ultraviolet at a 10-km or smaller spatial scale. This paper summarizes the science rationale and measurement objectives for MASCS, discusses its detailed design and its calibration requirements, and briefly outlines observation strategies for its use during MESSENGER orbital operations around Mercury.     

The Role of Modern Sensor Applications in the United Nations Resource Exploration and Evaluation Programs

In the first six months of 1971, the United Nations executed surveys using a number of the recently developed geophysical sensors on behalf of the United Nations Development Program in Ethiopia, Kenya, and Lesotho. The Ethiopia and Kenya surveys had the objective of direct exploration for and inventory of geothermal resources and involved coverage of some 39 000 km2 and 1550 km2, respectively, of thermal scanning in the 3 to 5 micron and 8 to 14 micron ranges. The Lesotho survey, experimental in nature, had the objective of exploration for diamondiferous kimberlite pipes and involved some 2600 km2 of aerial survey, utilizing true color, false color, and multispectral photography, scanning in the ultraviolet and 3 to 5 micron and 8 to 14 micron infrared spectra, infrared radiometry, and aeromagnetics. A preliminary evaluation of the results indicates a degree of success that will dictate expanded use of these methods by the United Nations in the future.     

Advanced Technologies Demonstrated by the Miniature Integrated Camera and Spectrometer (MICAS) Aboard Deep Space 1

MICAS is an integrated multi-channel instrument that includes an ultraviolet imaging spectrometer (80–185 nm), two high-resolution visible imagers (10–20 μrad/pixel, 400–900 nm), and a short-wavelength infrared imaging spectrometer (1250–2600 nm). The wavelength ranges were chosen to maximize the science data that could be collected using existing semiconductor technologies and avoiding the need for multi-octave spectrometers. It was flown on DS1 to validate technologies derived from the development of PICS (Planetary Imaging Camera Spectrometer). These technologies provided a novel systems approach enabling the miniaturization and integration of four instruments into one entity, spanning a wavelength range from the UV to IR, and from ambient to cryogenic temperatures with optical performance at a fraction of a wavelength. The specific technologies incorporated were: a built-in fly-by sequence; lightweight and ultra-stable, monolithic silicon-carbide construction, which enabled room-temperature alignment for cryogenic (85–140 K) performance, and provided superb optical performance and immunity to thermal distortion; diffraction-limited, shared optics operating from 80 to 2600 nm; advanced detector technologies for the UV, visible and short-wavelength IR; high-performance thermal radiators coupled directly to the short-wave infrared (SWIR) detector optical bench, providing an instrument with a mass less than 10 kg, instrument power less than 10 W, and total instrument cost of less than ten million dollars. The design allows the wavelength range to be extended by at least an octave at the short wavelength end and to ∼50 microns at the long wavelength end. Testing of the completed instrument demonstrated excellent optical performance down to 77 K, which would enable a greatly reduced background for longer wavelength detectors. During the Deep Space 1 Mission, MICAS successfully collected images and spectra for asteroid 9969 Braille, Mars, and comet 19/P Borrelly. The Borrelly encounter was a scientific hallmark providing the first clear, high resolution images and excellent, short-wavelength infrared spectra of the surface of an active comet’s nucleus.     

Galileo Ultraviolet Spectrometer experiment

The Galileo ultraviolet spectrometer experiment uses data obtained by the Ultraviolet Spectrometer (UVS) mounted on the pointed orbiter scan platform and from the Extreme Ultraviolet Spectrometer (EUVS) mounted on the spinning part of the orbiter with the field of view perpendicular to the spin axis. The UVS is a Ebert-Fastie design that covers the range 113–432 nm with a wavelength resolution of 0.7 nm below 190 and 1.3 nm at longer wavelengths. The UVS spatial resolution is 0.4 deg × 0.1 deg for illuminated disc observations and 1 deg × 0.1 deg for limb geometries. The EUVS is a Voyager design objective grating spectrometer, modified to cover the wavelength range from 54 to 128 nm with wavelength resolution 3.5 nm for extended sources and 1.5 nm for point sources and spatial resolution of 0.87 deg × 0.17 deg. The EUVS instrument will follow up on the many Voyager UVS discoveries, particularly the sulfur and oxygen ion emissions in the Io torus and molecular and atomic hydrogen auroral and airglow emissions from Jupiter. The UVS will obtain spectra of emission, absorption, and scattering features in the unexplored, by spacecraft, 170–432 nm wavelength region. The UVS and EUVS instruments will provide a powerful instrument complement to investigate volatile escape and surface composition of the Galilean satellites, the Io plasma torus, micro- and macro-properties of the Jupiter clouds, and the composition structure and evolution of the Jupiter upper atmosphere.