Table of Content

15 December 2009, Volume 38 Issue 6

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Preparation of FeIn_2S_4 Nanoparticles in Supercritical Water

ZHANG Hua-dong;LI Bo;ZHENG Qing-xin;XI He;TAO Xu-tang

2009, 38(6):  1299-1303. 

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Crystalline FeIn_2S_4 nanoparticles were successfully synthesized by a simple and one-step way, using thioacetamide (TAA), trichloride iron and tetrachloride indium as raw materials,supercritical water as reaction medium.The products were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that the obtained FeIn_2S_4 had cubic structure and a face-centered lattice. The microscopy images show that the synthesized FeIn_2S_4 particles were in sheet shape and exhibited weak agglomeration with the size ranging from 50 nm to 100 nm.

Preparation of ZnO Nanorod Arrays by Seed-assisted Chemical Bath Deposition Method

PAN Jing-wei;MA Xiang-yang;ZHANG Hui;YANG De-ren

2009, 38(6):  1304-1308. 

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ZnO nanorod arrays were prepared by seed-assisted chemical bath deposition, in which the c-axis oriented ZnO films prepared by magnetron sputtering were used as the seed layers. By means of scanning electron microscopy (SEM) and X-ray diffraction (XRD), we investigated the effects of deposition temperature of ZnO seed layer, chemical bath temperature and initial concentration of Zn source in precursor solution on the growth of ZnO nanorod arrays. As a result, the appropriate conditions for the growth of well crystallized ZnO nanoraod arrays which were nearly perpendicular to the substrate were defined.

Pinning Effect of the Neutron-irradiated 6H-SiC Crystals

RUAN Yong-feng;MA Peng-fei;JIA Min;LI Wen-run;ZHANG Yu-hui;ZHANG Shou-chao;WANG Dan-li

2009, 38(6):  1309-1312. 

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Two different 6H-SiC single crystals were neutron-irradiated with different dose of 5.74×10~(18) n·cm~(-2),8.2×10~(18) n·cm~(-2) and 1.72×10~(19) n·cm~(-2) respectively, the damages caused by neutron irradiation were studied by X-ray diffraction. It is found that the damages in the samples with higher purity or in the samples annealed before irradiation are less than that in the samples which are with lower purity or un-annealed. The experimental results indicate that the creations of irradiation damages are not only decided on the irradiation fluences, but also are decided on the structure and the composition of the samples. The inherent defects and the impurity atom play an important role in the irradiation process as the "pinning", which result in the increasing of the long-range defects such as dislocations.

Mechanical Parameters Test and Analysis for KDP Crystal

ZHANG Qiang-yong;LIU De-jun;WANG Sheng-lai;ZHANG Ning;MOU Xiao-ming;SUN Yun

2009, 38(6):  1313-1319. 

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The automatic and high precision system of RMT-150C was carried to test the mechanical parameters of KDP crystal. Elastic modulus, Poisson ratio, compressive strength and tensile strength were obtained. The results indicate that the elastic modulus in [001] and [100] are 39.25 MPa and 16.82 MPa while the Poisson rations are 0.24 and 0.16 respectively and the KDP is elastic-brittle transversely isotropic material. In addition, the compressive strength and tensile strength in [001] is higher than that in [100], so it is easier to crack in [100] than in [001]. Combined with the stress during growth process, it is found that the cracks are mainly caused by tensile stress, which lays an important foundation for studying the crack damage mechanism and proposing measures in the next step.

Study on Nd∶YAG Crystal Dislocation by Chemical Etching Method

SUN Jing;LI Chang-li;YU Wen-sheng;LI Si-hai;ZHANG Da-long;LIU Jing-he

2009, 38(6):  1320-1323. 

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The dislocation of Nd∶YAG crystal was studied by chemical etching method. The results indicate that the exhibition of the dislocation would be affected by corrosion temperature, corrosion time and corrosive agents. The exhibition of the dislocation was distinctive when the crystal was corroded by the concentrated phosphate acid at 220 ℃ for 20 min,and the pattern of etch pits was rhombus.By calculation, the dislocation density is about 10~3 cm~(-2). It was shown that the etch pit sizes and shapes of dislocation was different when the sample was corroded by the same corrosive under various etching time. At the same time , the dislocation pile-up groups was found on the edge of samples.

Influence of Filmogens on the Performance of Dye-sensitized Solar Cells

JI Wei-wei;ZHANG Xiao-dan;YANG Zhen-hua;ZHAO Ying

2009, 38(6):  1324-1328. 

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TiO_2 pastes were prepared using P25 powders and ethanol systems, which were used to make TiO_2 films as photo anode by the method of doctor blade coating. Comparing poly-vinyl pyrrolidone (PVP) with ethyl cellulose (M70) as film forming agents, it is discovered that the macro-and micro-structure of TiO_2 film using PVP has been improved, which mainly affects TiO_2 films porosities, surface area and dye adsorptions. PVP has played a significant role on the performances of dye-sensitized solar cells. As a result, short-circuit current increased from 5.59 mA/cm~2 to 11.31 mA/cm~2 and conversion efficiency increased from 2.70; to 5.31; under the standard AM1.5 irradiation condition.

Synthesis of Yttrium Silicates Nanocrystallites by Microwave-hydrothermal Method

XU Bin-sheng;CAO Li-yun;HUANG Jian-feng;WANG Ling-ling;XIA Chang-kui

2009, 38(6):  1329-1332. 

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Yttrium silicate nanocrystallites were synthesized by the microwave-hydrotherma1 method using Y(NO_3)_3·6H_2O, Na_2SiO_3 and NaOH as raw materials. The influence of solution composition, synthesis temperature and annealing temperature on the phase and microstructure of yttrium silicates crystallites were investigated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the powders. The results showed that Y_2SiO_5 content increase as the synthesis temperature increasing. The increase of annealing temperature is benefit for the growth of yttrium silicates crystallite. Y_2SiO_5, Y_(4.67)(SiO_4)_3O and Y_2Si_2O_7 crystallites with the particles size of 400-600 nm、200-400 nm and 400-600 nm can be achieved, using different initial solution composition under microwave hydrothermal at 150 ℃ for 10 min and annealing at 900 ℃ for 2 h,and the crystal is best.

Influence of Li Composition on the Photorefractive Properties of Pure Lithium Niobate Crystals

SHI Li-hong;YAN Wen-bo;LIU Jian-wei

2009, 38(6):  1333-1337. 

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The influence of Li composition on VIS-light photorefraction, UV-light-induced absorption and UV-light photorefraction in pure LiNbO_3 crystals at low light intensity was investigated. The experimental results indicate that different defects dominate the photorefractive centers of pure LiNbO_3 with varied compositions. For VIS-light photorefraction, Q polarons are introduced to explain the weak photovoltaic effect in LiNbO_3 with low composition, and bipolarons are considered to be responsible for the enhanced photovoltaic field in LiNbO_3 with high composition. It is also found that the UV-light-induced absorption and UV-light photorefraction have similar composition dependence. They increase slowly with the composition below 49.70 mol; but boosts up very rapidly above this critical composition. These findings are explained by the two different stages in the evolution of photorefractive centers during the increase of the crystal composition, which also proves our suggestion that different defects dominate the photorefractive centers of pure LiNbO_3 with varied compositions.

Study on Growth and Luminescence Properties of PbWO_4 Crystal Doped with Negative Ions

XIE Jian-jun;SHI Ying;WANG Jian;YUAN Hui;SONG Guo-xin;CHEN Liang;CHEN Jun-feng

2009, 38(6):  1338-1343. 

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This article presents the growth and luminescence properties of negative F~-, Cl~-, I~- and S~(2-) ions doped PbWO_4 crystals. Based on the results of measuring their X-ray powder diffraction, UV-VIS optical transmittance, photoluminescence, light yield and luminescence decay time, it can been seen that F- ion doping can obviously increase the optical transmittance at the 350-400 nm range, and enhance the luminescence intensity of PbWO_4 crystal, but the increase of the luminous intensity is mainly attributed to the slow illumination. Along with the increase of doped negative ions radius and the electric charge number,however, the luminescence intensity of PbWO_4 crystal decrease gradually and evident red-shift of the absorption edge is observed.

Preliminary Study on Textured ZnO/Si Heterojunction Solar Cells

ZHANG Ji-quan;ZHANG Fu-sheng;LIU Ai-min;LIU Wei-feng

2009, 38(6):  1344-1348. 

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p-Si<100> substrates were used to make textured structure in alkaline and IPA solution, ZnO∶Al thin films were deposited on textured Si substrates by ultrasonic spray pyrolysis techniques. Front and back electrode were prepared by techniques of lithography, metal sputtering and high vacuum evaporation, and subsequently annealed at a temperature of 400 ℃ under nitrogen environments. Atom force microscope, hall effect measurement, X-ray diffractomer and current-voltage characterization were employed to characterize solar cell performance. As a result, the conversion efficiencies of the fabricated solar cells of about 5.2; were obtained, with V_(oc)=355 mV, I_(sc)=36 mA, FF=0.41. Textured heterojunction structure effectively reduces light reflects, increased effective p-n junction area, thus improve solar cell performance. Silicon oxide film due to oxygen diffusion at the ZnO/Si interface through the porous structure of the ZnO films were the main effect of the solar cell efficiency.

Research on Dark Features in Diamond Films Produced by DC Arc Plasma Jet Method

JIANG Chun-sheng;GUO Shi-bin;LIU Zheng;TANG Wei-zhong;LV Fan-xiu

2009, 38(6):  1349-1354. 

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Dark features in diamond films prepared by DC arc plasma jet method were investigated by a laser marking process and fixed-point characterization. Optical microscopy, laser confocal scanning microscopy, scanning electron microscopy and electron backscattering diffraction methods were employed to analyze the defects at the same point. The results indicated that the dark features were such a kind of defects that embody pores and poor quality diamond phase located at grain boundaries of diamond films. The formation of the defects is related with the growth environment of the diamond films at specific grain boundaries.

Anisotropy of Resistance Transition Temperature of La-Ca-Mn-O Colossal Magnetoresistance Ceramics

HU Zhen-jiang;WANG Yue;ZHANG Yi-cai;JIANG Yi-jian

2009, 38(6):  1355-1357. 

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In order to further enhance resistance transition temperature (Tp) of metal-semiconductor of La-Ca-Mn-O colossal magnetoresistance ceramics, La_(0.67)Ca_(0.33)MnO_3 (LCMO) polycrystalline ceramics were formed as cylindrical pellets (φ13 mm×8 mm) by conventional solid-state reaction method. The anisotropy of LCMO samples which was cut from the sections parallel and perpendicular to the pressing direction were studied, respectively. The R-T curves shows that transition temperatures for these two types of specimens were 177 K and 261 K, respectively under and 0.5 T magnetic field. In addition, the mechanism of dramatic enhancement of transition temperature was explained through investigating XRD and SEM of the specimens.

Study on Fabrication and Properties of Y_2O_3:Er~(3+) Upconversion Nanofibers

DONG Xiang-ting;LIU Li;WANG Jin-xian;LIU Gui-xia

2009, 38(6):  1358-1364. 

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PVA/[Y(NO_3)_3+Er(NO_3)_3] composite nanofibers were fabricated by electrospinning.Y_2O_3∶Er~(3+) upconversion nanofibers were obtained by calcination of the relevant composite nanofibers. XRD analysis revealed that PVA/[Y(NO_3)_3+Er(NO_3)_3] composite nanofibers were amorphous in structure, and Y_2O_3∶Er~(3+) upconversion nanofibers were cubic in structure with space group Ia3. SEM images indicated that the mean diameter of the composite nanofibers was 130 nm, and Y_2O_3∶Er~(3+) upconversion nanofibers of 60 nm in average diameter were acquired at 600 ℃. TG-DTA analysis revealed that the water,organic compounds, nitrates in the composite nanofibers were decomposed and volatilized totally, and the weight of the sample kept constant when sintering temperature was above 600 ℃, and the total weight loss percentage was 80;. FT-IR analysis manifested that the spectrum of the composite nanofibers was basically the same as that of the pure PVA, and Y_2O_3∶Er~(3+) upconversion nanofibers were formed at 600 ℃.The upconversion spectroscopic properties of the Y_2O_3∶Er~(3+) nanofibres were investigated under the excitation of a 980 nm continuous wave diode laser. The Y_2O_3∶Er~(3+) nanofibers emitted strong green and red upconversion emissions centering at 522 nm,561 nm and 658 nm, respectively. The green emissions were attributed to the transitions of ~2H_(11/2)/~4S_(3/2)→~4I_(l5/2) energy levels of Er~(3+) , and the red emission was assigned to the transition of ~4F_(9/2)→~4I_(l5/2) energy levels of Er~(3+) . The formation mechanism of Y_2O_3∶Er~(3+) upconversion nanofibers was advanced. The technique could be applied to fabrication of other rare earth composite oxides upconversion nanofibers.

Influence of SiO_2 Additives on the Microstructure and Dielectric Properties of CaCu_3Ti_4O_(12) Ceramics

LI Wang;GONG Hui-ling;LIU Yu;LIU Bing-fa;LIU Gui-hua;DU Guo-ping

2009, 38(6):  1365-1369. 

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CaCu_3Ti_4O_(12) (CCTO) ceramics with the addition of SiO_2 were fabricated by the conventional solid-state reaction method. The phase structure, microstructure and the dielectric properties of the CCTO ceramics with different weight percentages of SiO_2 were investigated. There was no solid-state reaction between CCTO and SiO_2 at the sintering temperature, and the SiO_2 additives were observed to be present at the CCTO grain boundaries. It was found that the addition of SiO_2 influenced the microstructure and dielectric properties of the CCTO ceramics. The dielectric constant and loss tangent decreased with the increasing content of SiO_2. Impedance spectroscopy showed that the grain boundary resistance increased due to the addition of SiO_2 to CCTO, which should be main reason for the decrease in the loss tangent of the CCTO ceramics.

Study on the Optical Properties of B-implanted Lithium Niobate Waveguide with Ellipsometry

YU Xiao-hong;LIAN Jie;LU Fei;SONG Ping;GAO Shang

2009, 38(6):  1370-1374. 

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2.5 MeV B ion-implanted lithium niobate crystal was studied by ellipsometry method. Data from the measurement were inversed to fit a moderate four-layer model for the crystal. The depth of waveguide layer and the refractive index dispersion in the range of 0.3-0.8 μm were obtained. Barrier of reduced refractive index was found .Waveguide structure was get from the crystal surface to the depth of 2.0 μm in the crystal. The results provided important information for the fabrication of waveguide devices.

Two-dimensional Phononic Energy Bands Calculations by FDTD Combined with High-resolution Spectral Estimation

SU Xiao-xing;WANG Yue-Sheng

2009, 38(6):  1375-1379. 

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Based on the high-resolution spectral estimation method in modern signal processing, a postprocessing method is proposed to analyze the data series, which are generated during the iterations of the finite difference time domain (FDTD) method used to calculate the energy bands of two-dimensional (2D) phononic crystal. Numerical simulation results show that, compared with the postprocessing method based on Fourier transform, the proposed postprocessing method can reduce the number of iterations of the FDTD method significantly while yielding precise estimation of the eigenfrequencies of the 2D phononic crystal at the same time.

Research on BaM Ferrite Films Synthesized by Alternate Sputtering Method

ZHANG Hong;LIU Xi;LIU Xiao-xi;WEI Fu-lin;A.S.Kamzin;HE De-yan

2009, 38(6):  1380-1383. 

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The BaM ferrite films with fine grain size as small as 30 nm were prepared by reactive RF diode sputtering method, using alternate depositing process. It is found that two step annealing process is beneficial for films to form perpendicular orientation structures, which were identified by microstructure measurement such as X-ray diffraction pattern (XRD), conversion electron Mssbauer spectra (CEMS) and atomic force microscope(AFM).

Effects of Sintering Temperature on Luminescence Properties of Blue Long Afterglow Phosphors Sr_2Al_6O_(11):Eu~(2+), Dy~(3+)

XUE Hong-wei;CUI Cai-e;HUANG Ping;HAO Hu-zai

2009, 38(6):  1384-1387. 

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Blue-emitting long-lasting phosphors Sr_2Al_6O_(11)∶Eu~(2+),Dy~(3+) were synthesized by conventional solid state reaction method. The effects of sintering temperature on the phase-formation and the luminescent properties of the Eu~(2+)and Dy~(3+) co-doped blue strontium aluminates were investigated. Phase identification was carried out by X-ray powder diffraction analysis. Excitation and emission spectra were recorded using a luminescence spectrometer, and afterglow curves were measured by a photometer. The results revealed that with the calcining temperature rising from 1100 ℃ to 1300 ℃ gradually, the aluminate rich in strontium changed to the aluminate rich in aluminum while emission band shifted to the shorter wavelength side, and then to the longer wavelength side. The phosphor with a main phase Sr_2Al_6O_(11) and an emission peak at shortest wavelength of 468 nm was synthesized with a calcining temperature of 1200 ℃.The decay time (≥1 mcd/m2) of the phosphor whose main phase was Sr_2Al_6O_(11) reached 240 min.

Study on Influence Factors of h-BN Nanocrystals Prepared by Solvothermal Method

GE Lei;QIU Tai;YANG Jian

2009, 38(6):  1388-1393. 

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Hexagonal boron nitride nanocrystals were prepared by solvothermal method at 220 ℃ using Li_3N and BBr3 as raw materials. The effects of reaction time, surfactant and induced seeds on the production waere studied. The experimental results indicate that the hexagonal boron nitride was the dominant production and cubic boron nitride could be also found. The size of the crystals grew from 20 nm to 80 nm as the reaction time extended from 12 h to 36 h. With the addition of surfactant, the crystal size could be limited to 10 nm and the degree of sphericity improved. The content of hexagonal phase increased with the addition of h-AlN seeds, and some rod like h-BN nanocrystals appeared in the production.

Effect of Surfactant on Photoluminescence Properties of ZnS:Cu,Al Nanocrystals Synthesized by Hydrothermal Method

XIN Mei;CAO Wang-he

2009, 38(6):  1394-1398. 

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ZnS∶Cu,Al nanocrystals were synthesized by a hydrothermal method at 200 ℃. The photo luminescence (PL) spectra,FT-IR spectra and crystallinity of the rinsed and unrinsed samples under various molar ratios of S/Zn and effect of surfactant have been systematically investigated. The spherical-like nanocrystals had a grain size of approximately 15 nm and were well dispersed, with a zinc blende structure. Crystallization and particle size of samples decreased after the rinsed process. The PL emission intensity of unrinsed sample stronger than rinsed sample, but at low ratio of S/Zn, the enhanced emission intensity is more significantly. In addition, the surfactants also affect the surface state of nanocrystals and PL emission spectra. The results show that the luminescence mechanism of PL spectra attribute to the luminescence centers on surface of materials detected by UV light, so the surface state of nanomaterials determine the PL emission intensity and affect the crystallization of nanocrystals.

Photocatalytic Properties of Si-doped TiO_2 by Hydrothermal Method

LIU Yan-min;ZHANG Xue-jing;LIU Jing-ze;ZHANG Yan-feng;WEI Yu

2009, 38(6):  1399-1403. 

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A series of Si-doped nanocrystalline titania powders were prepared by hydrothermal method using titanium tetrachloride (TiCl_4) and sodium silicate (Na_2SiO_3) as precursors. The photocatalysts were characterized by X-ray diffraction (XRD) analysis, fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectrophotometer (UV-vis DRS). As the Si doped, photocatalysts with smaller crystal size, higher content of anatase phase were obtained. It was also found that Ti-O-Si band was formed in the Si-doped samples. The photocatalytic activity of Si-doped TiO_2 were improved compare with non-doped. The possible reasons of Si-doped for the enhanced photocatalytic activity was discussed.

Hydrothermal Synthesis of Bi_2S_3 Nanostructures with Different Morphologies

YAO Guo-guang;MA Hong;ZHU Gang-qiang

2009, 38(6):  1404-1409. 

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Different morphologies of nanostructured bismuth sulfide (Bi_2S_3) were prepared by hydrothermal method at 120 ℃ for 12 h. The products were characterized by XRD, SEM, TEM, HRTEM and UV-vis. The results show that raw materials have great effect on the morphologies of final products and mineralization agents play important roles on the synthetic temperature. The formation mechanism of the Bi_2S_3 nanostructures was discussed. The UV-vis measurement shows that compared to the bulk orthorhombic Bi_2S_3,the absorption spectrum of the sythesized Bi_2S_3 has a clear blue shift which might be ascribed to the size effect.

Preparation and Photocatalytic Properties of TiO_2 Nanotube Arrays

WANG Zhu-mei;LI Yue-ming;XIA Guang-hua;JIANG Xiang-ping;ZUO Jian-lin

2009, 38(6):  1410-1415. 

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Titania nanotube arrays were fabricated by anodic oxidation on a pure titanium sheet. The morphology, structure and optical properties of the nanotube arrays were characterized by FSEM,XRD and UV-Vis. The effect of anodic oxidation parameters on the morphology of TiO_2 nanotube arrays was investigated. The mechanism of the growth of the titania nanotube arrays was discussed, and the photocatalytic activity was tested. The results show that the vertical oriented TiO_2 nanotube arrays can be obtained at 20 V for 60 min in 0.5 wt;HF+1 mol/L H3PO_4 solution. The aperture size of nanotubes is 60-80 nm and the thickness of tube wall is about 10 nm. The spectral absorptivity of TiO_2 nanotube arrays membrane calcined at 600 ℃ on ultravlolet light 349.7 nm and visible light 443.9 nm was relatively higher. It was also found that the calcination temperature has an obvious effect on the crystal structure and photocatalytic activity of the titania nanotube arrays.

Study on Transmission Characteristics of Curved Waveguides Based on 2D Heterostructure Photonic Crystals

LIU Jing;CHEN Chao-yang;YANG Guang-song;DU Yong

2009, 38(6):  1416-1419. 

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The transmission characteristics of L-type waveguides system based on 2D heterostructure photonic crystals was studied by finite-difference time-domain ( FDTD) method. The results showed that it is better for controlling light transmission by introducing heterostructure in this system. In the L-type waveguide system, the transmission efficiency raises 6;-7; for the heterostructure photonic crystal, compared to that on homostructure photonic crystal. The studies provided a new design solution improving the efficiency of high-integration photonic crystals waveguide devices.

Solvothermal Synthesis and Crystal Structure of a New 3-D Open Framework Zinc Nitrite{[Zn(NO_2)_3]~-·H_3O~+·H_2O}_n

FAN Rui-qing;WANG Ping;YANG Yu-lin;HASI Wu-liji

2009, 38(6):  1420-1423. 

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A new three-dimensional open framework zinc nitrite {[Zn(NO_2)_3]~-·H_3O~+·H_2O}_n(Zn1) was synthesized by solvothermal method. The products was characterized by X-ray powder diffraction (XRD), IR spectra, Raman spectra, TG analysis and structurally determined by single-crystal X-ray diffraction analysis. The results indicated that the compound crystallizes in the trigonal symmetry, space group R-3c, with a=b=c=0.8814(6) nm, α=β=γ=55.51(2)°, V=2.0394(2) nm~3, Z=12, R_1=0.0325, wR_2=0.0829, GOF=1.077. The adjacent Zn centers are linked with O from NO_2~-to form 3-D structure of Zn1 containing 8-rings along [100] and [110] direction, respectively.

Investigation on Activation Energy of Intrinsic Microcrystalline Silicon Thin Films Deposited by VHF-PECVD

CHEN Qing-dong;WANG Jun-ping;LI Jie;ZHANG Yu-xiang;LU Jing-xiao

2009, 38(6):  1424-1428. 

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Intrinsic microcrystalline silicon thin films were deposited by VHF PECVD, the activation energy of thin films were measured by activation energy testing equipment. The activation energy of samples with different crystalline volume fractions prepared at different power and different pressure were studied. The results showed that the activation energy of samples deposited at amorphous/microcrystalline transition zone decreased as the crystalline volume fractions increasing. As the depositing power and pressure increasing, the depositing rates and activation energy were also increased. As a result, oxygen contamination could be suppressed by increasing depositing rates using relatively higher power and pressure.

Influence of Microstructure on the Optical Properpties of the Eu:Ti Nanomaterials

ZENG Qing-guang;LE Tian;CAI Jin-jun;DING Ze-jun;LIU Jian;SHENG Ye-qing;WANG Yi

2009, 38(6):  1429-1432. 

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In this manuscript, Eu doped in TiO_2 nanorods (Eu∶Ti nanorods) was prepared by hydrothermal and high temperatures annealing methods using TiO_2∶Eu nanoparticle(molar ratio TiO_2∶Eu =100∶1,the particle size was about 10-30 nm,anatase)as raw materials. The structure and optical properties of the Eu∶Ti nanorods were characterized by field emission scanning electronic microscopy (FE-SEM) and confocal microscope Raman spectrometer. The FE-SEM image shows the nanorods diameter is 30 nm and length is 300-600 nm. A part of anatase phase was also observed in nanorods by Raman spectra. The steady-state/lifetime spectrofluorometer was used to record the emission spectra and the lifetime curves of the samples. It is obviously that the fluorescence spectra of the Eu∶Ti nanorods is different from the nanoparticle, and the emission intensity of the former is stronger than later. By monitoring the ~5D_0→~7F_2 transition intensity of the Eu~(3+) excited by the 394 nm line, it is found that the lifetime of nanorods is longer 120 μs than the nanoparticle.

Thermal Conductivity and Tensile Properties of BN, SiC and Ge Nanotubes

SHEN Hai-jun;TIAN Shao-gang;FU Guang-jun

2009, 38(6):  1433-1437. 

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Thermal conductivity and axial tensile behaviour of single-wall BN, SiC and Ge nanotubes were simulated by MD(Molecular dynamics) method, and the thermal conductivity and load-strain curves of the nanotubes were given. According to the obtained results, the differences in conductivity and tensile-properties of the nanotubes were investigated. The results showed that the thermal conductivity of all the nanotubes decreases as the temperature and diameter increaing. At the same temperature, the BN nanotubes has the highest thermal conductivity, whereas the Ge and SiC tubes have the comparable one;The Ge tube has both the lowest anti-deformation and anti-loading capability, the BN tube the highest anti-load one, and the BN, SiC tubes the comparable anti-load one.

Adsorption Growth of SnO_2 Quantum Dot on the Surface of Sodium Titanate Crystal Fibers

WEI Zhi-ren;PENG Xiang-yu;ZHANG Li-ming;ZHOU Yang;DONG Guo-yi

2009, 38(6):  1438-1441. 

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In this paper, the adsorption growth characteristics of SnO_2 nanocrystals grown on the surface of sodium titanate crystal fibers were investigatived. The rutile structure SnO_2 nano-crystals quantum dot have been prepared on the surface of sodium titanate crystal fibers by the hydrothermal method using sodium titanate crystal fibers and proper amount of SnCl_4· 5H_2O as the precursors. The reaction conditions was pH value 11, the fill factor was 68;, reacting temperature were 120 ℃ and 150 ℃ respectively, the total reacting time was 24 h. The SnO_2 nano-crystals had a size of about 5 nm. The results show that the surface of sodium titanate had a strong apparent activation energy.

Analysis on the Nanomechanical Properties of CdZnTe(211) Face

LI Yan;KANG Ren-ke;GAO Hang;WU Dong-jiang;WANG Jing-he

2009, 38(6):  1442-1445. 

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The process of lapping, mechanical polishing and chemical mechanical polishing was used to machine the CdZnTe (211) face, when the surface roughness Ra was 0.94 nm, nano indenter was employed to measure the mechanical properties of CdZnTe (211) face, the experimental results show that the hardness and elastic modulus decrease as the indention load increasing, which is obvious the size effect. When the nanoindenter departs the crystal surface, the adherence effects are obvious. Strong anisotropy of the hardness and elastic modulus is shown on different crystallographic direction.

Synthesis of Nonlinear Optical Crystal Na_5[B_2P_3O_(13)] and BaAlBO_3F_2 by Hydrothermal Method

LI Zhi-hua;ZHANG Ji-hui

2009, 38(6):  1446-1449. 

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Na_5[B_2P_3O_(13)](NBP)and BaAlBO_3F_2(BABF)nonlinear optical crystals have been synthesized by hydrothermal method, the moderate reaction conditions have also been determined. The feasible initial charging ratio has been investigated in order to fabricate pure BABF. The as-synthesized NBP and BABF are characterized by XRD, SEM and second harmornic generation effect measurement, respectively.

Global Simulation Crystal Growth of CdZnTe by the Detached Vertical Bridgman Method

PENG Lan;ZHANG Quan-zhuang

2009, 38(6):  1450-1455. 

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CdZnTe single crystal growth process with detached vertical Bridgman method by FLUENT was simulated. Two kinds of boundary condition of the upper melt were calculated: (1)non-slip wall;(2) free surface. The gap width (e) between the crucible wall and crystal and gravity were the two key factors for the crystal growth process. The temperature distribution, stream function distribution and the solidification interface shape were displayed and analyzed both in the microgravity and the gravity condition with e equals to 0 mm, 0.5 mm and 1 mm, respectively. The simulation results showed that in the microgravity condition, when the upper of melt is non-slip wall, the flow strength of thermocapillary convection increases with the wider gap width. However, when the upper of melt is free surface, the flow strength shows the opposite trend with the increase of the gap width. In the gravity condition, the flow strength decreases with the increase of the gap width, which will improve the crystal quality.

Thermochemical Polishing Techniques of CVD Diamond Films

HUANG Shu-tao;ZHOU Li;JIAO Ke-ru;XU Li-fu

2009, 38(6):  1456-1462. 

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The polishing technology of diamond films has become one of the key technologies for the popularization and application of diamond films. In recent years, a number of alternative polishing techniques of diamond films have been reported, and each having technological advantages and disadvantages. The thermochemical polishing technology based on the diffusion of carbon atoms has good prospect due to its superior properties, e.g. excellent polishing quality, high efficiency and very small mechanical damage. But up to now, the thermochemiacal polishing method, in which the polishing plate is heated to high temperature, either need complicated apparatus or the polishing process is very costly. In this paper, the development and characteristics of thermochemical polishing techniques were reviewed, and the effects of different factors on thermochemical polishing of diamond films were also reviewed. Finally, a new super-high speed polishing method of diamond films has been proposed, which was aided by the rare earth metal. The effects of polishing temperature on the theoretical removal rate of diamond films has been analyzed by using diffusion mechanics, and the results agree well with the experiment data. The super-high speed polishing method has the advantages of simple apparatus and precision polishing for diamond films, etc.

Calculation of Type Ⅱ Phase-matching Walk-off Angle and Interaction Length of LBO Crystals

XUE Jian-hua;REN Qing-hua;WANG Ai-kun

2009, 38(6):  1463-1466. 

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From nonlinear optics theory, type Ⅱ frequency-doubling walk-off angle and interaction length of LBO crystal whose fundamental frequency wavelength is at 1064 nm were respectively calculated with numerical method . In the range of whole phase-matching angle, the angle range between the slow and the fast lights of 1064 nm is 0~1.0°. θ≈0°,φ≈90°, the angle is 0°;θ≈45°,φ≈55°, the maximum angle is approximately 1.0°. When the light-spot dimensions of slow and the fast lights are the same and wave vector incidents along the direction (θ≈0°,φ≈88°), the interactional length is the maximum.

Preparation of Au Nanometer Thin Film Using Silicon Nanoporous Array as Template

FU Xiao-nan;FU Jian-hua;LI Kun;LUO Yan-wei;LI Xin-jian

2009, 38(6):  1467-1471. 

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The Au/Si-NPA samples with different morphologies were fabricated experimentally by immersion technique using fresh and aged silicon nanoporous pillar array (Si-NPA)substrates as template. The results show that the differences between morphologies of the Au/Si-NPAs which were prepared on two kinds of substrates are due to the differences of oxygen quantities distributing on the surface of the Si-NPA substrates. The further studies show that the Si-NPA present two functionalities during fabricating of the Au/Si-NPA. One is as the reductant and another the template. The Si-NPA regular array structure leads to the velocity dependence of Au deposition on the local geometrical features of the Si-NPA surface. Finally, the quasi-periodical, regular Au nanocomposite thin film has been formed.

Application of Ion Implantation Technique in Optimization Treatment of Shandong Sapphire

CHENG You-fa;WANG Ji-yang;TIAN Liang-guang;ZHANG Huai-jin;LI Jian-jun

2009, 38(6):  1472-1476. 

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The paper reports the technique using ion implantation(Be~(2+) and Ti~(4+))technique in the Shandong sapphire treatment. Some testing and research had been done before and after the implantation. The results show that : (1)As ion was implanted in, the luster turned obviously brighter. While surface of the samples kept smooth as well as before;(2)As Be~(2+) was implanted in Shandong sapphire, the color turned obviously heavier, though Be~(2+) was not color-causing element, it could affect the color;(3)As Ti~(4+) was implanted in, the color of Shandong sapphire turned fade and brighter, which indicated that the dark color was because of high proportion of Fe~(2+)while low proportion of Ti~(4+). It is a new method of optimization and treatment in Shandong sapphire and other gems.

Light-emitting Properties of Alkali Metal-doped ZnO Thin Films

ZHANG Li-xue;CHEN Chang-le;LUO Bing-cheng

2009, 38(6):  1477-1480. 

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The compounds of ZnXO (X=Li, Na and K) were prepared by a convention solid reaction method and the highly c-axis oriented ZnXO (X=Li, Na and K) thin films were deposited on Si (111) substrates by magnetron sputtering method. The structures,surface morphology and the luminescent properties of thin films were measured by X-ray diffraction(XRD), atomic force microscopes(AFM) and photoluminescence(PL).The results indicated that the ZnXO thin films show good c-axis orientation. Different PL spectra were acquired at room temperature using xenon lamps as excitation light sources, with excitation wavelengths of 325 nm. The UV peaks and violet peaks were found to originate from free excition radiation recombination and the PL intensity was related to crystalline quality, and the blue-green peaks may be related to the zinc and oxygen vacancies. The physical mechanism was disscussed throngh which the red shift of UV PL peaks.

Study on the Surface Modification of Carbon Nanotubes Using Fenton Reagents

YIN Qiang;LI Ai-ju;SUN Kang-ning;SHI Jun;REN Qiang

2009, 38(6):  1481-1484. 

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Carbon nanotubes (CNTs) were modificated using Fenton reagents. The effects of different Fenton reaction(Fenton,Fenton/US and Fenton/UV) on the surface of CNTs were studied. The reaction mechanism between Fenton regeant and carbon nanotubes was also investigated. The purity of CNTs was investigated by TGA. The functional groups on the surface of CNTs were investigated by FTIR spectra, and the microstructure of CNTs was investigated by transmission electron microscopy (TEM). The results show that Fenton/UV can introduce a great deal of hydroxyl groups onto the surface of carbon nanotubes, and can not damage it badly;the reaction mechanism between Fenton and carbon nanotubes is that hydroxyl radical (HO· ) generated in the reaction can produce hydroxylation with the undersaturation double bond on the surface of carbon nanotubes.

Effect of In Doping on Zeta Potentials of Tin Oxide Powders Synthesized by Chemical Coprecipitation Method

HU Xue-bing;ZHOU Jian-er;XU Xiao-yong;WANG Yong-qing;ZHANG Xiao-zhen

2009, 38(6):  1485-1488. 

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In-doped tin oxide powders were prepared by a chemical coprecipitation process using tin tetrachloride, indium trichloride and ammonia as raw materials. The properties of SnO_2-based powders doped with In were studied systematically by X-ray diffraction (XRD) and Zeta potential analyzer. The results showed Zeta potential of In-doped SnO_2 powders is the lowest when the fraction of In-doped is 2 mol;. Compared with the pure SnO_2, the presence of the dopant alters slightly the crystal cell parameter of SnO_2 and increases significantly its crystal cell volume.

Study on Preparation of La_2O_3 Nanocrystalline by the Combustion Method

LIU Ying;FENG Jin-chao

2009, 38(6):  1489-1492. 

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The nanocrystalline La_2O_3 were prepared by the combustion method, in which the lanthanum nitrate was conducted as oxidant, ammonium citrate as fuel and a little urea as initiating agent. The influences of the factors on product, including calcinating temperature, stoichiometry ratio between materials and release gases were studied. The thixotropic paste complex LaCit was heated and burnt at a temperature of 150 ℃, and then the gray precursor was obtained. The nanocrystalline La_2O_3 was prepared by calcining the precursor at 700 ℃ for 2 h. Then the samples were characterized by XRD, TEM and SEM. The results indicate that the morphology of nanocrystalline La_2O_3 is clarity-rectangled flakes on an average length of 100-150 nm, the width of 40-80 nm and the thichness of 20 nm. The yield of nanocrystalline La_2O_3 is 85;-87; with narrow size distribution and good dispersion of particles.

Study on Stability of the Pull Rate in the Czochralski Growth Process of Single Silicon

FU Yong-ling;ZHANG Kai;QI Xiao-ye

2009, 38(6):  1493-1498. 

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For the purpose of reducing the pull rate fluctuation during the Czochralski crystal growth process of single silicon, the approach of controlling the temperature compensation rate was presented based on analyzing the energy and mass balance at the solid-liquid interface. A new fuzzy control method was proposed of which the membership function parameters were optimized using the genetic algorithm to tune the power input, thus the inner circumstance of the furnace was more suitable for the crystal growth. Experiment data verifies that with this approach, the precision of the crystal diameter was improved and the pull rate fluctuation was considerable reduced also.

Forbidden Band and Reforming of the Elastic Wave in Solid and Solid Constitute Phononic Crystal

LIU Qi-neng

2009, 38(6):  1499-1505. 

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Leading into the four-dimensional wave vector, the transfer matrix and the transmission coefficients of the solid and solid constitute phononic crystal were inferred. Using these formula the transmission coefficient of the longitudinal wave and transversal wave in the solid and solid constitute phononic crystal were calculated. When longitudinal wave oblique incidence, there is the forbidden band of longitudinal wave in the transmission wave, and there is reforming that longitudinal wave to transversal wave, the greater the incident angle is more obvious of the reforming. When transversal wave oblique incidence there is similar result also. Used these formula the transmission and reforming of the elastic wave in the solid and solid constitute phononic crystal are solved.

Study and Analysis of Factors Affecting on Synthesis of Carbon Nanotubes from V-type Pyrolysis Flame

LIU Yuan-chao;SUN Bao-min;ZHAO Hui-fu;DING Zhao-yong;JIA Bin

2009, 38(6):  1506-1510. 

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The V-type pyrolysis flame experimental system was introduced to synthesize carbon nanotubes. The carbon nanotubes from the experiment were characterized by scanning electron microscope and transmission electron microscope. The major factors including temperature, gas content, catalyst and equilibrium rate affected in carbon nanotubes synthesis were discussed. Carbon nanotubes with good morphology and less impurity can be captured when the temperature is from 800 ℃ to 1000 ℃, carbon monoxide/hydrogen/helium mixed gas flow is supplied and pentacarbonyl iron is served as the catalyst.

Polarization Fatigue Mechanism of the Perovskite Ferroelectric Thin Films under Cyclic Electric Field

NING Ping-fan;CUI Cai-e;HUANG Ping;KANG Ai-guo;HAO Hu-zai

2009, 38(6):  1511-1515. 

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An analytical model for the polarization fatigue under cyclic electric field of the perovskite ferroelectric thin films was proposed by incorporating the switch-induced charge-injection mechanism and the local phase decomposition theory into the oxygen vacancy electromigration model. The effects of the low permittivity interfacial layer on the fatigue property were analyzed with this model. The results showed that the interfacial layer is an crucial reason for polarization fatigue in ferroelectric thin films. The model can easily simulate the fatigue behavior of various ferroelectric thin films under different relaxation times, voltages, and temperatures.

Research on Preparation, Microstructure and Performance of MoB/CoCr Cermet Coatings

CHEN Xiao;ZHANG Ren-yuan;LI Feng

2009, 38(6):  1516-1521. 

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MoB/CoCr cermet coatings were deposited by low pressure plasma spraying (LPPS).The microstructure and phase component of coatings were characterized by XRD, SEM and EDAX, the coatings were also studied on bond strength and thermal shock resistance performance. The results show that phase component of powder and coating had little change, chamber pressure influenced the melting of powder dramatically during LPPS, and the ratio of fully-melted zone/partly-melted zone increased as chamber pressure increasing. The coatings are dense and have excellent combination with substrate. The main constituents of coatings remain invariant and the coatings have excellent performance of bond strength and thermal shock resistance. And the MoB/CoCr coating has much higer durability in the molten Al-12.07wt;Si after 1080 h immersion test.

Influence of Zn~(2+) on the Structure and Magnetic Properties of Hexagonal Strontium Ferrite

JIN Ming-lin;ZHU Cun-fu;BAO Zong-hong;QIAN Hui-chun;CHEN Qi-zhong

2009, 38(6):  1522-1526. 

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Strontium ferrites with La, Co and Zn substitution were prepared by conventional ceramic method, and the influence of Zn~(2+)on the structure and magnetic properties of hexagonal strontium ferrites had been investigated. The XRD results show that ferrites remain a hexagonal structure with the content of Zn~(2+)increasing, lattice parameter a was gradual increased and c first increased,then decreased with x increasing. SEM results show the grains represented an orderly plate, many of them even were hexagonal shape. The sizes of grains were gradual increased with the increasing content of Zn~(2+). By magnetic properties measurement, Br and Hcj both were 436 mT, 343 kA/m when x=0.15. It demonstrates the antiparallel magnetic moments can be effective decreased and saturation magnetization is increased, so the magnetic properties have been improved.

Phase Transition, Elastic Property and Electronic Structure of Wurtzite and Rocksalt ZnO

FEI Ying;CHENG Shuang;SHI Li-bin;YUAN Hong-kuan

2009, 38(6):  1527-1531. 

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The phase transition, elastic property and the electronic structure of wurtzite (B4) and rocksalt (B1) ZnO were investigated by the first principles based on density functional theory(DFT) and plane-wave pseudopotential method. The results showed that B4 phase transition into B1 phase happened about 12.72 GPa. The elastic modulus of B1 and B4 phase ZnO were 171.5 GPa and 132.8 GPa, respectively. The results of band structure showed that the B1 phase was indirect band gap semiconductor and its value was 1.404 eV. B4 phase was semiconductor with direct band gap of 1.107 eV.

XRD Analysis of Peroskite-type Larged Compound K_2Ln_2Ti_3O_(10) (Ln=La,Pr,Sm,Eu,Gd)

SHI Kun-bo;ZHANG Li-li

2009, 38(6):  1532-1535. 

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Series of layered perovskites K_2Eu_2Ti_3O_(10) and K_2Gd_2Ti_3O_(10) was fabricated by solid state reaction.The obtained products were characterized by X-ray diffraction (XRD) and inductively coupled plasma (ICP) techniques. The crystal structure of K_2Ln_2Ti_3O_(10) (Ln=Eu,Gd) series has been analyzed and the crystal parameters and indexed dates were obtained. The XRD results indicated that the K_2Ln_2Ti_3O_(10) (Ln=La,Pr,Sm,Eu and Gd) belonged to tetragonal crystal lattice and had I4/mmm space group, unit cell parameter. The cell parameters and the evolution of K_2Ln_2Ti_3O_(10) were gained.

Synthesis, Crystal Structure and Luminescent Properties of a Supramolecular Compound (C_(12)H_(10)N_4)(C_7H_6O_3)_2

BAI Yan;GAO Hui;DANG Dong-bin;ZHANG Guo-qiang

2009, 38(6):  1536-1539. 

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A new supramolecular compound (C_(12)H_(10)N_4)(C_7H_6O_3)_2 was synthesized and characterized by elemental analysis, IR, UV spectroscopy and single-crystal X-ray diffraction. In the crystal structure, multiform hydrogen bonds and stacking interactions lead to a supramolecular compound. The luminescent properties of the compound in the solid state were investigated. The crystal belongs to monoclinic, space group P2_1/c with a=0.3974(1) nm, b=2.0330(2) nm, c=1.4343(1) nm, β=94.892(2)°, V=1.15440(19) nm~3, dc=1.400 g/cm~3,Z=2, μ=0.102 mm~(-1), F_((000))=508, R_1=0.0359, wR_2=0.0893 [I>2σ(I)].

Investigation on the Nucleation Kinetics, Growth and Thermal Properties of γ-aminobutyric Acid Crystal

CHEN Xiao;YANG Wen-ge;HU Yong-hong

2009, 38(6):  1540-1543. 

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In this paper, the nucleation kinetics and thermal properties of γ-aminobutyric acid which is the chief inhibitory neurotransmitter in the mammalian central nervous system were investigated. The grown crystals have also been subjected to thermal studies. The DSC studies showed that the sample started to melt at 190.6 ℃ with high melting enthalpy of -343.4 J/g. The solubility of γ-aminobutyric acid was estimated at different temperatures in water. The induction period was measured for the different supersaturation ratios. The study revealed that the induction period of γ-aminobutyric acid decreased as the supersaturation increasing. The metastable zone width of γ-aminobutyric acid was measured by polythermal method. Interfacial tension has been estimated by the experimentally determined induction period values. Nucleation parameters, such as the radius of critical nucleus and the Gibbs free energy barrier, have also been investigated based on classical nucleation theory. The relationship between high melting enthalpy of γ-aminobutyric acid and its structure was also explained.

Synthesis, Crystal Structure and Fluorescence Properties of {[Ln(H_2O) _2(O_2CCH_2CH_2CO_2) _3]·H_2O}_n (Ln=Eu(Ⅲ),Sm(Ⅲ))

YANG Feng-yun;HAN Chun-ying;ZHANG Li-dan;WANG Lei;LI Jin-ge

2009, 38(6):  1544-1549. 

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The lanthanid-organic coordination polymers of {[Ln(H_2O) _2(O_2CCH_2CH_2CO_2) _3]·H_2O}_n (Ln= Eu(Ⅲ),Sm(Ⅲ)) were synthesized by solvent-thermal methld.The crystal structures were characterized by X-ray diffraction method and FT-IR spectrophotometer.The result indicate that both coordination polymers belong to monoclinic, space group C2/c, with cell parameters of Eu coordination polymer 1:a= 2.000(04) nm,b=0.7780(02) nm,c=1.387(03) nm,α=90 °,β=121.58(3) °,γ=90 °,V＝1.838(66) nm~3,Z＝4,F(000)=1344,M_r= 706.18, D_c= 2.551 Mg/m~3, μ=6.839 mm~(-1), R_1=0.0357, ωR_2=0.1012;with cell parameters of Sm coordination polymer 2 is a =2.0072(02) nm,b=0.7822(26) nm,c=1.3901(61) nm,α=90°,β =121.5840 °,γ=90 °,V＝1.8593(3) nm~3,Z＝4,F(000)=1336, M_r= 70296, D_c=2.511 Mg/m~3,μ=6.333 mm~(-1), R_1=0.0210,ωR_2=0.0498. Fluorescence properties had been observed in F-4500 FL spectrophotometer.

Synthesis and Crystal Structure of Coordination Polymers [Zn(phen)(H_2O)3SO_4]·H_2O

LAN Cui-ling;SHI Bing-fang;CHEN Hua-ni;LI Yuan-cheng

2009, 38(6):  1550-1554. 

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The title complex was synthesized by reaction of o-phenanthroline (phen) and zinc sulfate heptahydrate in water-ethanol solution. The crystal structure was characterized by X-ray diffraction, the complex composition was determined by elemental analysis, IR and UV spectrum. The results show that the title complex belongs to triclinic system with space group P_1~- and cell parameter: a=0.8042(3) nm,b=0.8636(8) nm, c=1.1595(1) nm, α=92.067(0)°, β=92.126(0)°,γ=103.761(0) °, V=0.7809(0) nm~3, Z=2, D_c=1.016 g/cm~3, μ=0.876 mm~(-1), F_((000))=424. The Zn(Ⅱ) is coordinated by one phen, three water molecule and one SO_4~(2-). The complex exhibites a distorted octahedron geommetry. 3D supramolecular structure is constructed by hydrogen bonds.

Preparation of Porous SiO_2/SiC Fiber from SiO_2/Resorcinol Hybrid Sol Precursor

SONG Qiu-sheng;ZHANG Kai;FEI Bin;XU Shun

2009, 38(6):  1555-1559. 

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SiO_2/Resorcinol hybrid sol was prepared by sol-gel method using TEOS and resorcinol as raw materials, and SiO_2/resorcinol hybrid fiber was prepared by drawing method. The hybrid fiber was characterized by FT-IR, DSC, TG, XRD and SEM. The results showed that partial resorcinol is linked silica with coralent bonds and the fiber was amorphous. The hybrid fiber was pyrolyzed at 600～1300 ℃ under atmosphere, the FT-IR, XRD and SEM showed that the hybrid fiber convert into porous SiO_2/SiC fiber when it was heated at 1300 ℃.