全玻璃真空太阳集热管光-热性能

从能量平衡方程导出全玻璃真空太阳集热管的 3个光 热性能参数 ,即热损系数ULT、闷晒太阳曝辐量H和空晒性能参数Y与真空集热管的罩管玻璃的太阳透射比τ、选择性吸收表面的太阳吸收比α、发射比ε、和集热管内的气体压强p ,以及太阳辐照度、环境温度和真空太阳集热管的几何尺寸等函数关系。理论计算的真空太阳集热管的 3个热性能参数与实验的结果比较一致。上述全玻璃真空太阳集热管的光 热性能参数已经被国家标准《全玻璃真空太阳集热管》(GB/T 170 49- 1997)采用。

Hydrothermal synthesis, characterization and optical properties of La_2Sn_2O_7:Eu^(3+) micro-octahedra

Pyrochlore structure La2Sn2O7：Eu3＋ microcrystals with uniform octahedron shape were successfully synthesized via a hydrothermal route at 180 °C for 36 h. The crystal structure, particle size, morphologies, and optical properties of the as-synthesized products were investigated by XRD, TEM, SEM, EDS, FT-IR, Raman spectroscopy and PL. The effects of pH of precursor solution, precursor concentration, reaction temperature, and time were investigated. The results reveal that pH of the precursor solution not only plays an important role in determining the phase of the as-synthesized products, but also has a significant influence on the morphologies of the samples. High-quality and uniform octahedrons with an average size of about 700 nm could be easily obtained at the pH value of 12. The possible formation mechanism of octahedral-like La2Sn2O7：Eu3＋ microcrystals was briefly proposed. The photoluminescence spectra show that La2Sn2O7：Eu3＋ micro-octahedra display stronger emission in the range of 582-592 nm compared with the samples with other shapes.

Mesh-Like Bi2MoO6 with Enhanced and Stable Visible Light Photocatalytic Activity

Mesh-like Bi2MoO6 product was successfully synthesized by a hydrothermal method without using any surfactant or template. The pH value played an important role in the formation of this morphology. The as-prepared mesh-like Bi2MoO6 sample exhibited excellent visible-light-driven photocatalytic e ciency. The photocatalytic activity of the mesh-like Bi2MoO6 sample was much higher than that of bulk Bi2MoO6 sample prepared by solid-state reac-tion. Di erence in the photocatalytic activities of the mesh-like Bi2MoO6 sample and bulk Bi2MoO6 sample was further investigated.

Synthesis,characterization and gas-sensing properties of Pd-doped SnO_2 nano particles

SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surface chemistry of these nano particles were characterized by transmission electron microscope,X-ray diffractometer and X-ray photoelectron spectroscope respectively.It was observed that Pd-doping had little effect on the grain sizes of the obtained SnO2 nano particles during the hydrothermal route.During thermal annealing,Pd-doping could restrain the growth of grain sizes below 500℃ while the grain growth was promoted when the temperature increased to above 700℃.XPS results revealed that Pd existed in three chemical states in the as-synthesized sample as Pd^0,Pd^2＋ and Pd^4＋,respectively.Pd^4＋ was the main state which was responsible for improving the gas-sensing property.The optimal Pd-doping concentration for better gas-sensing property and thermal stability was 2.0%-2.5% （mole fraction）.

Laser-weldable Si_p-SiC_p/Al hybrid composites with bilayer structure for electronic packaging

Laser-weldable Sip-SiCp/Al hybrid composites with high volume fraction （60%-65%） of SiC reinforcement were fabricated by compression moulding and vacuum gas pressure infiltration technology. Microscopic observation displayed that the Sip-SiCp/Al hybrid composites with bilayer structure were compact without gas pores and the intergradation between Sip/Al layer and SiCp/Al layer was homogeneous and continuous. Further investigation revealed that the Sip-SiCp/Al hybrid composites possessed low density （2.96 g/cm^3）, high gas tightness （1.0 mPa·cm^3）/s）, excellent thermal management function as a result of high thermal conductivity （194 W/（m·K） and low coefficient of thermal expansion （7.0×10^-6 K-1）. Additionally, Sip-SiCp/Al hybrid composites had outstanding laser welding adaptability, which is significantly important for electronic packaging applications. The gas tightness of components after laser welding （48 mPa·cm^3）/s） can well match the requirement of advanced electronic packaging. Several kinds of these precision components passed tests and were put into production.

Hydrothermal Synthesis of Rhombus-like SmCO3OH Microplates and Its Photoluminescence Property Doped with Eu^3＋

Rhombus-like SmCO3OH microplates with the edge lengths ranging from 5 μm to 10 μm and the thickness about 1.5 μm were synthesized through a simple hydrothermal method using urea as the precipitance. The structure and properties of the rhombus-like SmCO3OH microplates were characterized by X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The optical property of the rhombus-like SmCO3OH microplates doped with Eu^3＋ was investigated by photoluminescence. A broad and strong emission band at 677 nm was obtained, which can be contributed to producing light conversion film.

Influence of addition of B_2O_3 on properties of Yb^(3+)-doped phosphate laser glass

The three host glasses doped with Yb 3+ were prepared by means of conventional melt quenching technology, and the influence on physical and spectral properties of phosphate glass due to addition of B2O3 was investigated and compared with silicate glass. The results show that due to the existence of OH- impurities which induce the non-radiative route, the fluorescence lifetime of phosphate glass is shorter, so silicate glass has better spectral properties than phosphate glass. Silicate glass has more excellent thermal-mechanical properties than phosphate glass, but with the addition of B2O3, thermal-mechanical properties of phosphate glass are improved greatly without fluorescence quenching effect, and this kind of borophosphate glass will be the candidate to be used in high average power solid state laser.

Thermal stability and Judd-Ofelt analysis of optical properties of Er^(3+)-doped tellurite glasses

Er3＋-doped TeO2-ZnO-Na2O-B2O3-GeO2 （TZNBG） glasses were prepared by melt-quenching method. Differential scanning calorimetry （DSC） and thermal mechanical analysis （TMA） were used to calculate thermal parameters： crystallization temperature （Tx）, glass transition temperature （Tg） and thermal expansion （α）. Besides, Judd-Ofelt theory is applied to analyzing absorption spectra. Intensity parameters -λ （λ=2, 4, 6）, transition probabilities Aed, radiative lifetime τi, and branching ratios β of Er3＋ transitions were obtained. Emission cross-section σemis of 4I13/2→4I15/2 transition of Er3＋ was calculated according to the theory of McCumber. All of the parameters indicate that the thermal stability and optical properties of Er3＋-doped TZNBG glasses are improved effectively.

Dark Color ZnO Quasi-One-Dimensional Nanostructures Grown by Hydrothermal Method and Modulation of their Optical Properties

Zinc oxide has a large energy gap and thus it has potential application in the field of solar cells by tuning the absorption of sunlight. In order to enhance its absorption of sunlight,dark color zinc oxides have been prepared by traditional hydrothermal method directly using a zinc foil as both source and substrate. We found that we could tune the optical properties of ZnO samples by changing the temperature. In particular, increasing temperature could significantly reduce the reflectivity of solar energy in the visible range. We speculate that the phenomenon is relevant to the sharp cone morphology of the ZnO nanorods grown on the surface of Zn foils, which furthermore enhance refraction and reflection of light in the nanorods. The capacity to improve the light absorption of ZnO may have a bright application in raising the efficiency of solar cells.

Solvothermal Synthesis and Optical Performance of One-dimensional Strontium Hydroxyapatite Nanorod

One-dimensional strontium hydroxyapatite （Sr-HAp） nanorods were successfully synthesized by a simple solvothermal method. The products were characterized via X-ray diffraction （XRD）, Fourier transform infrared （.FT-IR）, .cold field emission.sc.anning.elec.tron microscopy_.（FESEM）, transmission.electron microscopy （TEM）,photoluminescence （PL） excitation and emission spectra. The experimental results indicated that oleic acid as a surfactant played a key role in confining the growth of the Sr-HAp powders. A possible formation mechanism of the one-dimensional nanorod was proposed and elaborated. Moreover, the as-obtained Sr-HAp samoles showed an intense and bright emission band centered at 460 nm under long-wavelength UV light excitation and the contents of NaOH used in the synthetic process had an obvious impact on the optical performance of Sr-HAp powders. The possible luminescent mechanism of the Sr-HAp samples was discussed.

Analysis of I-V Thermal Characteristic on GaN-based p-i-n Ultraviolet Detector

The I-V characteristic of GaN-based p-i-n ultraviolet detector is presented. It is measured at different temperatures and analyzed with changing temperature. The ideality factor of the device is 2.09 at room temperature. The maximum ideality factor is 2.14 at 100 ℃, which declines above 100 ℃, and the minimum ideality factor is 1.26 at 300 ℃. The coefficient of forward voltage vs. temperature is -1.97 mV/℃ with a forward current of 1 mA. Based on double injection model, the deep lying impurity activation energy in the i-region is 0.1 343 eV.

Theoretical Study on Vibrational Spectra, Detonation Properties and Pyrolysis Mechanism for Cyclic 2-Diazo-4,6-dinitrophenol

Based on the full optimized molecular geometrical structures at the DFT-B3LYP/6- 311＋G^＊＊ level, there exists intramolecular hydrogen bond interaction for cyclic 2-diazo- 4,6-dinitrophenol. The assigned infrared spectrum is obtained and used to compute the thermodynamic properties. The results show that there are four main characteristic regions in the calculated IR spectra of the title compound. The detonation velocities and pressures are also evaluated by using Kamlet-Jacobs equations based on the calculated density and condensed phase heat of formation. Thermal stability and the pyrolysis mechanism of 2- diazo-4,6-dinitrophenol are investigated by calculating the bond dissociation energies at the B3LYP/6-311＋G^＊＊ level.

Effects of Zn/P ratio on structures and properties of zinc-iron phosphate glasses

Effects of Zn/P ratio on the structures and properties of glasses with the general composition of （80-x）ZnO-20Fe2O3-xP2O5 （x=40, 45, 50, 55, 60） （molar fraction, %） were investigated. Glass structure was measured by infrared absorption spectrum. Glass density （/9） was measured by the Archimedes method. Coefficients of thermal expansion （a） and characterization temperature were obtained by a dilatometer. Water durability of each glass was estimated from the dissolution rate （DR）in water at 90 ℃ for 24 h. With increasing Zn/P ratio, water durability of zinc-iron phosphate glasses increases dramatically without large increase in the characterization temperature. （80-x）ZnO-20Fe2O3-xP2O5 glasses with 0.3≤Zn/P≤0.5 are suit for low-to-mid temperature sealing application for substrates with a〈8.0× 10^-6℃^-1.

Performance Evaluation of New Two Axes Tracking PV-Thermal Concentrator

The overall problem with PV （photovoltaic） systems is the high cost for the photovoltaic modules. This makes it interesting to concentrate irradiation on the PV-module, thereby reducing the PV area necessary for obtaining the same amount of output power. The tracking capability of two-axes tracking unit driving a new concentrating paraboloid for electric and heat production have been evaluated. The reflecting optics consisting of flat mirrors provides uniform illumination on the absorber which is a good indication for optimised electrical production due to series connection of solar cells. The calculated optical efficiency of the system indicates that about 80% of the incident beam radiation is transferred to the absorber. Simulations of generated electrical and thermal energy from the evaluated photovoltaic thermal （PV/T） collector show the potential of obtaining high total energy efficiency.

Characterization of ZnSe microspheres synthesized under different hydrothermal conditions

ZnSe microspheres were synthesized via a facile hydrothermal method under mild conditions using aqueous zinc nitrate and sodium selenite as raw materials. The effects of hydrothermal temperature, reaction time, concentration of NaOH and amount of hydrazine hydrate on the phase structure, morphology and size of final products were carefully investigated. The phase structures, morphologies and optical properties of the final products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. ZnSe microspheres assembled by average size (about 20 nm) nanocrystals were prepared using 20 mL of 1 mol/L NaOH solution and 10 mL of hydrazine hydrate at 180 °C for 4 h. The results show that the products obtained at low hydrothermal temperature and short reaction time have poor crystallinity and contain impurity phases. The appropriate NaOH concentration and amount of hydrazine hydrate ensure to obtain pure ZnSe with spherical morphology and better luminescence property.

Enhanced photocatalytic properties of hierarchical nanostructured TiO_2 spheres synthesized with titanium powders

Using Ti powder as reagent, TiO 2 nanoneedle/nanoribbon spheres were prepared via hydrothermal method in NaOH solution. The samples were characterized by field emission scanning electron microscopy （FESEM）, transmission electron microscopy （TEM） with selected area electron diffraction （SAED）, X-ray diffraction （XRD）, and UV-visible light absorption spectrum. The results indicate that the growth orientations of the crystals are influenced by the hydrothermal temperature and NaOH concentration. The diameter of the nanoneedle spheres and nanoribbon spheres （40 50 μm） are almost the same as that of Ti powders. TiO 2 nanoneedle/nanoribbon sphere powders are anatase after heat treatment at 450 °C for 1 h. Furthermore, methyl orange was used as a target molecule to estimate the photocatalytic activity of the specimens. Under the same testing conditions, the photocatalytic activities of the products decrease in the following order： TiO 2 nanoneedle sphere, TiO 2 nanoribbon sphere and P25.

Influence of Ag on photocatalytic performance of Ag/ZnO nanosheet photocatalysts

Ag/ZnO nanosheet composites were prepared by zinc nitrate, sodium hydroxide and silver nitrate via a simple hydrothermal method. The crystal structure, morphology, optical property and photocatalytic performance were studied by means of XRD, SEM, HRTEM, XPS, and PL methods. It is found that both the pure ZnO and composite Ag/ZnO samples have the same morphology of nanosheet. The interaction of spherical Ag particles with ZnO matrix in the Ag/ZnO sample leads to an increase in photocatalytic efficiency for the possible increase of concentration of surface hydroxyl and the photo-induced electrons and holes. The addition of Ag can reduce the recombination rate of photo-generated carriers and the sample with addition of 3 at% Ag to ZnO exhibits the best photocatalytic activity with the degradation rate up to 95% within 15 min.

Functionalized Gold Nanorods for Tumor Imaging and Targeted Therapy

Gold nanorods,as an emerging noble metal nanomaterial with unique properties,have become the new exciting focus of theoretical and experimental studies in the past few years.The structure and function of gold nanorods,especially their biocompatibility, optical property,and photothermal effects,have been attracting more and more attention.Gold nanorods exhibit great potential in applications such as tumor molecular imaging and photothermal therapy.In this article,we review some of the main advances made over the past few years in the application of gold nanorods in surface functionalization,molecular imaging,and photothermal therapy. We also explore other prospective applications and discuss the corresponding concepts,issues,approaches,and challenges,with the aim of stimulating broader interest in gold nanorod-based nanotechnology and improving its practical application.

Synthesis and properties of UV curable polyurethane acrylates based on two different hydroxyethyl acrylates

Two kinds of UV curable polyurethane acrylate oligomers （PUPA and PUCA） were synthesized via the addition reaction between isophorone diisocyanate （IPDI） and polyethylene glycol monoacrylate （PEA6） or polycaprolactone modified hydroxyethyl acrylate （PCLA2）. The structures of PUPA and PUCA were characterized by Fourier transform infrared spectroscopy （FT-IR）, IH nuclear magnetic resonance （^H NMR）, gel permeation chromatography （GPC） and differential scanning calorimeter （DSC）, and the thermal stability and dynamic mechanical thermal properties of their cured films were measured by thermogravimetric analysis （TGA） and dynamic mechanical analysis （DMA）, respectively. The viscosity of the oligomers and mechanical properties of the cured films were also studied. The results show that both oligomers have narrow molecular weight distribution. The viscosity of PUPA is 2.310 Pa.s at 25 ℃, while that of PUCA is： up to 3.980 Pa-s. The UV cured PUPA and PUCA films have homogeneous phase structure, and the PUCA film shows higher glass transition temperature and storage modulus. Furthermore, the PUCA film possesses better mechanical properties than PUPA, while the latter shows better alkali resistance.

Thermal fatigue crack growth behavior of ZCuAlFeMn alloy strengthened by laser shock processing

The effect of laser shock processing(LSP) on the hardness, surface morphology, residual stress, and thermal fatigue properties of a ZCuAl10Fe3Mn2 alloy was investigated to improve the thermal fatigue performance and decrease the surface crack of high-temperature components. The microstructure and crack morphology were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). The results showed that laser shock could significantly improve the thermal fatigue performance of the alloy at a pulse energy of 4 J. Under the effect of thermal stress and alternating stress, microstructure around the specimen notch was oxidized and became porous, leading to the formation of multiple micro-cracks. The micro-cracks in the vertical direction became the main cracks, which mainly expanded with the conjoining of contiguous voids at the crack tip front. Micro-cracks in other directions grew along the grain boundaries and led to material shedding.