Table of Content

15 February 2017, Volume 46 Issue 2

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2017, 46(2):  1. 

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Growth of High Quality β-Ga2O3 Single Crystal by EFG Method

JIA Zhi-tai;MU Wen-xiang;YIN Yan-ru;ZHANG Jian;TAO Xu-tang

2017, 46(2):  193-196. 

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High quality β-Ga2O3 single crystal with 25 mm in width and 100 mm in length were grown by edge-defined film-fed growth (EFG) method.The crystal apperance complete,colorless,no cracking.Powder X-ray diffraction demonstrated that the obtained crystal is β phase.High-resolution X-ray diffraction showed a full-width at half-maximum (FWHM) of the rocking curve of 93.6",indicating a high crystal quality.The ultraviolet absorption spectrum was investigated and the bandgap was estimated to be 4.77 eV.Furthermore,the effect of shouldering processing parameters on crystal quality was also discussed.

Analysis and Verification of Reaction Model for Silane Pyrolysis Polycrystalline Silicon CVD

FAN You-wen;CHEN Cai-xia

2017, 46(2):  197-203. 

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Based on a critical review of reaction kinetics of silane decomposition reported in literature,a simplified gas and surface reaction mechanisms are used for analyzing a horizontal single-substrate reactor with the 2-D boundary-layer reaction model of CHEMKIN software.The predicted growth rates of silicon agree well with the literature data.The effects of operation conditions on growth rate,such as the silane concentrations and the gas temperatures,were examined and the cluster savenging mechanisms were evaluated numerically.Neglecting the flow characteristics,the Ho mechanisms were used in the simulation under conditions of the mimic fluidized bed silane CVD reactor.The predicted growth rate is comparable with experimental data,indicating the above mechanisms can be further applied in CFD simulation of silane fluidized bed CVD reactors.

Analysis of PECVD Heat and Flow Field under Different Process Parameters and Showerhead Structures

JIANG Li;XIANG Dong;YANG Wang

2017, 46(2):  204-212. 

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The PECVD reaction chamber's fluid and heat transfer model were established,the influence of process parameters and showerhead plate structures on the heat and flow distribution were studied.Based on the typical process parameters,simulations were designed according to single variable principle to study the influence of process parameters on the velocity,pressure and temperature distribution above wafer.The simulation results show that,under different process parameters:the distribution of velocity is linear with radius;the fluctuation of temperature is small and shows good stability;pressure is distributed approximately parabolic along with radius with higher pressure in the center.In addition,the effect of showerhead plate's flow resistance distribution on the heat and flow distribution were studied by designing two sets of simulations.The results show that the velocity on the edge of heat plate remains unchanged for different flow resistance distributions,but there is a turning point in the velocity distribution and velocity is linearly distributed before and after the turning point.So,it can be concluded that the velocity distribution above wafer can be controlled to acquire higher deposition uniformity by changing the flow resistance distribution of showerhead plate.

Synthesis and Up-conversion Luminescence Properties of Lanthanum Fluoride in the Ionic Liquid

WANG Jing;SUN Ming-juan;DU Fei;YIN Jie;PAN Shang-ke;PAN Jian-guo

2017, 46(2):  213-218. 

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The ionic liquid (1-butyl 3-methyl imidazolium tetrafluoroborate) was the reaction system and the fluorine source of Lanthanum fluoride,and the effects of raw materials' stoichiometric ratio on the synthesis and morphology were also studied.The reaction mechanism was analyzed.The NaLaF4:Er/Yb and LaF3:Er materials were characterized and analyzed by XRD,SEM and other methods.Under 980 nm excitation,the up-conversion luminescence properties of the sample were measured,and the influence of Er3+ concentration and Yb3+ doping on the up-conversion luminescence properties were analyzed.The up-conversion luminescence properties of NaLaF4:Er and LaF3:Er in a temperature range of 303-583 K were measured.The temperature dependence of the fluorescence intensity ratio of 524 nm and 542 nm was discussed.

Enhancement of Organic Solar Cells Light Absorption Based on Incorporating Silica-coated Silver Nanospheres

CHEN Ming;ZHANG Ye;REN Jing-kun

2017, 46(2):  219-223. 

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Although dielectric-coated metallic nanoparticles were frequently applied in organic solar cells (OSCs) for improving the device performance by preventing the possible exciton quenching and charge recombination at the metal surface,there have been few theoretical researches addressing how the dielectric-coating of metal nanoparticles influences the optical performance of OSCs.The effect of coating silver nanaspheres were theoretically studied by a silica film on the absorption performance of OSCs.This results show that an integrated light absorption efficiency of 81.5; in the PSBTBT:PC71 BM active layer over the wavelength range from 350 nm to 850 nm at normal incidence,outperforming the structurally identical planar control cell by 9.54;.Detailed investigations reveal that the excitation of the dipole localized surface plasmon resonance,SPP and LSP and their mutual coupling are responsible for the observed broadband enhancement in light absorption.Through studying the influences of structure parameters,the results show that the thinner dielectric coating is more favorable for light absorption enhancement.In addition,refractive index impact on absorption enhancement of OSC is not obvious.

Effect of Hydrogen Peroxide on the Preparation of Zirconium Silicate Thin Films by Sol-gel Method

LI Cong;JIANG Wei-hui;FENG Guo;LIU Jian-min;WU Qian;MIAO Li-feng;ZHANG Quan

2017, 46(2):  224-230. 

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Zirconium silicate thin film was prepared via sol-gel method using zirconium oxychloide as zirconium source and tetraethyl orthosilicate as silicon source.The effects of hydrogen peroxide (H2O2)on the preparation of zirconium silicate film and the corrosion resistance of zirconium silicate film were investigated by means of SEM,DTA-TG,FT-IR and XRD,respectively.The results show that appropriate hydrogen peroxide effectively accelerates the hydrolysis of the zirconium oxychloide and overcomes the holes and poor densification caused by weight loss at high temperature.When the mole ratio of H2O2/Zr is less than 2,uniform and dense film can not be prepared.However,impurity phase appears when the mole ratio of H2O2/Zr is more than 2.Uniform and dense zirconium silicate thin film could be prepared when the optimal mole ratio of H2O2/Zr is 2.The thin film has excellent corrosion resistance against NaOH solution.The mass loss of silicon wafer is 16.92; after corrosion,however,the mass loss of silicon wafer with zirconium silicate thin film is only 0.56;.

Research Progress of Negative Thermal Expansion Ferroelectric Crystals

LIU Wen-bin;TIAN Tian;XU Jia-yue

2017, 46(2):  231-237. 

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Recently,negative thermal expansion (NTE) material is a hot topic in material science.In this paper,the progresses and mechanism of negative thermal expansion materials were reviewed.The crystal growth and thermal expansion characteristics of perovskite and tungsten ferroelectric crystals were introduced in detail.The NTE mechanism was discussed based on the ferroelectric phase transition and the potential applications of NTE were suggested.

Study on Preparation and Properties of Sr3YCo4O10.s +δ Polycrystal with Room Temperature Ferromagnetism

HU Jian-li;YU Lan;DU Xiao-li;SONG Shi-jin

2017, 46(2):  238-242. 

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Room temperature ferromagnetic Sr3YCo4O10.5+δ polycrystals with tetragonal structure were prepared by solid-state sintering method.The Sr3YCo4O10.5+δ polycrystals were characterized by thermogravimetricdifferential scanning calorimetry,X-ray diffraction and scanning electron microscopy.The results indicate that the final sintering temperature should be above 963 ℃,and the optimal sintering temperature was 1180 ℃ within our experiments.The Sr3YCo4O10.5+δ polycrystals show semiconductor behavior at 80-300 K,and the room-temperature resistivity reached its minimum of ～78.8 rΩ · cm with the optimal sintering temperature.The thermopower of polycrystals decreased with increasing temperature in at 317-1018 K,and the thermopower was 70.74 μV/K at 317 K.The magnetization-temperature curves and hysteresis loops showed that the spin states of internal Co3 +,magnetic domains and orientations of magnetic moments changed under the influence of applied magnetic field,temperature and crystal field,resulting in different magnetizations and magnetic states.With the applied magnetic field of 0.1 T,the Hopkinson peak with the largest magnetization of 0.46 emu/g was observed at 320 K in the ZFC curve,and the Curie temperature(Tc) was 323 K.While the largest magnetization of 1.1 emu/g was obtained at the Neel temperature(TN) of 264 K in the FC curve,and Tc was 320 K.The polycrystals all show room-temperature ferromagnetism in both ZFC and FC curves.

Photocatalytic Activity and Anti-photocorrosion Properties of Ag2O/TiO2 Heterojunction

2017, 46(2):  243-250. 

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Ag2O/TiO2 heterojunction photocatalysts were synthesized on FTO through hydrothennal method and ultrasonic precipitation method with precursors (Ti (Obu)4,Bi (NO3) 2 and AgNO3).The structures and morphologies of Ag2O/TiO2 heterostructure were investigated by field emission scanning electron microscopy (FESEM),X-ray diffraction (XRD) and UV-Vis spectra.The results indicate that Ag2O/TiO2 heterostructures consist of TiO2 nanorod arrays decorated with 200-300 nm Ag2O nanoparticles.Compared to the pure TiO2 nanorod arrays,the Ag2O/TiO2 heterostructures exhibit obviously absorption under visible light irradiation.Ag2O/TiO2 heterojunction photocatalytic activity improves significantly.Further,through visible light irradiation treatment,Ag-Ag2O/TiO2 composite stability system were fabricated,the mechanism for improving photocatalytic stability and activity of Ag-Ag2O/TiO2 composite system was also proposed.

Research Progress on Preparation of Carbon Nanomaterials by Plasma Discharge in Liquid Medium

2017, 46(2):  251-260. 

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Carbon nanomaterials,such as carbon nanotubes,carbon onions and graphene,have exhibit potential applications in the field of energy and environment.Based on recent domestic and foreign researches in preparing carbon nanomaterials by plasma discharge in liquid media such as liquid nitrogen,deionized water,salt solutions or organic solvents,the advantages and disadvantages of different discharge medium were compared,the reaction mechanism were discussed.The improvements and insufficient in the area of the preparation of carbon nanomaterials by plasma discharge in liquid method,which is meaningful for profound understanding of the concepts and principles of liquid plasma discharge process,improving the experimental and theoretical research methods,expanding the range of applications and realize industrial applications as soon as possible with proposals.

Effect of Different Filling Solvents on Morphology and Photocatalytic Performance of CaTi2O4 (OH) 2

HU Qi-guo;DONG Wei-xia;GU Xing-yong;LUO Ting

2017, 46(2):  261-266. 

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CaTi2O4 (OH)2 powders with different morphologies were prepared by hydrothermal method via changing the kinds of filling solvents.The phase structure and microstructure of the powders were characterized by X-ray diffraction and scanning electron microscopy.The adsorption and photo-degradation of Rhodamine B were characterized by UV-Vis absorption spectra.The influence of filling different solvents on the CaTi2O4 (OH)2 powders phase structure,morphology,optical energy gap and photocatalytic performance were investigated.The results show that ethanol and ethylene glycol could inhibit the growth and development of crystal,and could obtain nanowires or dendritic CaTi2O4 (OH)2 powders,which exhibited better adsorption properties for Rhodamine B.The CaTi2O4 (OH)2 powder with lamellar structure can be obtained when using solvent-free and filled with water or cyclohexane were used as filling solvent.Filling cyclohexane can promote the growth and development of CaTi2O4 (OH) 2 phase,which has the highest crystallinity of 78.04;,and the photocatalytic performance rate of Rhodamine B reached 91.6; at 3 h of UV-visible light.

Fabrication of Porous Mullite Ceramics by Freeze Drying Method Combined with Starch Consolidation

LI Hao;CHEN Yong-jun;LI Jian-bao;LUO Li-jie

2017, 46(2):  267-272. 

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Interconnected porous mullite ceramics were fabricated by freeze-drying process combining starch consolidation,using kaolin,aluminum hydroxide as starting materials,starch as consolidator and binder and Y2O3 as sintering additive.The effects of starch content on the slurry rheological property,porosity,pore-size distribution,microstructure and mechanical strength of porous mullite ceramics were investigated.It is found that the viscosity of slurry increased significantly with the starch addition increased from 15.84vol; to 20.59vol;,but decreased dramatically with the increase of shear rate and tended to be steady,suggesting a slight shear-thinning behavior.With the starch content increasing,the pore size of the ceramics decreased,displaying a homogeneous pore size distribution from bimodal to unimodal.Meanwhile,the porosity changed slightly and kept in the range of 61.5;-66.2;.In addition,when the starch content increased to 15.84vol;,the compressive strength of ceramics increased to the maximum values of 9.5 MPa,porosity also increased to 65.7;.However,the compressive strength tend to decease with the further increase of starch content.

Preparation and Phase Transformation during Calcination of Eu∶ Lu2SiOs Powders by Sol-gel Method

YANG Yi;YANG Lei;CHEN Yan-lin;YAN Ming

2017, 46(2):  273-277. 

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Lu2SiO5 (LSO) dried gel precursors were prepared by sol-gel method,which was subjected to thermal analysis.The TG curves were stable after 400 ℃.The exothermic peaks of the DSC curve at 402.8 ℃ and 1049.9 ℃,respectively correspond to the initial crystallization temperature of LSO powder and the phase transition temperature.The dried gel was calcined at 900 ℃,1000 ℃,1100 ℃ and 1200 ℃ for 2 h.The XRD shown that after calcination at 900 ℃ for 2 h,the product was not completely crystallized and amorphous phase also existed,but the characteristic diffraction peak of A-LSO phase had appeared.After calcination at 1000 ℃ for 2 h,the powders completely crystallized as A-LSO phase.After calcination at 1100 ℃ for 2 h,the A-LSO phase transformed to B-LSO phase,and the crystal transformation temperature was about 1050 ℃,which corresponded to the exothermic peak at 1049.9 ℃ in DSC curve.There were significant differences in the morphology of A-LSO and B-LSO.The particle size were both in 400-500 nm.The emission peaks located at 595 nm,617 nm,707 nm correspond to the 5D0→TF1,SD0→7F2,5D0→7F4 transition of Eu3+ respectively.The luminescence intensity was increased first and then decreased with the increase of Eu3+ doping concentration.The optimum doping concentration is 5; mol.

Study on the Dielectric Properties of Graphene/BST/PVDF Composite Thin Films

HONG Wei;PENG Bo;LIU Jun;JIANG Nan;LUO Ying

2017, 46(2):  278-284. 

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Firstly,graphene and barium strontium titanate powder modified with silane coupling agent was prepared.The graphene/BST/PVDF composite thin films were prepared by solution mixing method.The microstructure of the composite film,dielectric properties and thermal stability were measured and analyzed.The results show that silane coupling agent is successfully grafted onto the surface of graphene and barium titanate powder.They can be better dispersed in the PVDF matrix,the addition of graphene can significantly improve the dielectric properties of the material.When the mass fraction of graphene is 4.06;,the dielectric constant of the composite thin film has reached 515,and the dielectric loss is 0.6.In the seepage occur when mass fraction of 4.14;,dielectric constant of 1500 and dielectric loss reach 5 or so.The increase of the dielectric properties of the composites is greatly improved by the addition of graphene,and composite materials have good temperature stability in the common temperature range.

Fabrication and Up-conversion Luminescence Properties of Gd2O2S∶Yb3+ , Er3+ Nanopowders by Hydrothermal Reduction Method

LIU Fan;WANG Xu-ri;ZHANG Jing;YANG Yan-yu;ZHANG Zhao-ren;LIAN Jing-bao

2017, 46(2):  285-290. 

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Gd2O2S:Yb3+,Er3+ nanopowders were fabricated by hydrothermal method assisting with reduction route utilizing commercially available reagents of Gd2O3,Yb2O3,Er2O3,HNO3,CO (NH2)2and C12 H25 SO4Na.The structure,morphology and up-conversion luminescent properties were characterized by fourier transform infrared spectroscopy (FT-IR),X-ray diffractometry (XRD),transmission electron microscopy (TEM),selected area electron diffraction (SAED) and up-conversion luminescence spectra (UPL).The results show that the molar ratio of Gd3 + ∶ CO(NH2) 2∶ SO42-=2∶1∶ x have a significant influence on the structure of the as prepared products.The precursor synthesized with x =1.0 could be converted into pure Gd2O2S phase by calcining at 800 ℃ for 2 h in the hybrid atmosphere of flowing hydrogen and argon (90; Ar + 10; H2) resulting in quasi-spherical and agglomerated morphology with 30 nm in size.Under 980 nm infrared light excitation,UPL spectra of the Gd2O2S∶Yb3+,Er3+ nanophosphors show a red emission at 671 nm as the most prominent peak and a green emission at 548 nm as the secondary emission peak,which attribute to the 4F9/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3 + ions.The quenching concentration of Er3+ ions is 5;,and the emission mechanism is two photo model.

Preparation and Electrochemical Characteristics of VO2/Nickel Foam Integrating Electrode Materials

LI Kun-zhen;YUAN Jiang-tao;LIU Zhong-fei;XIONG Kuang-wei;JIN Shao-wei;WANG Pei-hong

2017, 46(2):  291-296. 

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The VO2/nickel foam integrating electrode materials were successfully prepared by one-pot hydrothermal approach,using V2O5,oxalic acid and nickel foam as raw materials.The structures and morphologies of VO2/nickel foam electrodes were characterized by (XRD) spectrometry and scanning electron microscopy (SEM).The results indicate that the VO2 shows a nanoflake-structure when the concentration of oxalic acid is 0.1 mol · L-1 this nanoflake-structured of VO2 has a thickness ranges of 80-140 nm.The electrochemical results indicate that the VO2/nickel foam electrode with a nanoflake-structured shows a specific capacitance of 3.99 F · cm-2 at a current density of 1 mA · cm-2 It is ascribed to a high specific surface area of the nanoflake-structured VO2/nickel foam electrode.The nanoflake-structured VO2/nickel foam electrode is recycled for 2000 cycles,only 9.95; of its specific capacity is lost,exhibits good cycle stability.

Fabrication and Properties of Poly/Hydroxyapatite Whisker with Composite Porous Scaffolds

QIN Xiao-su;LEI Yun;HUANG Jie;CHEN Qing-hua;YAN Ting-ting

2017, 46(2):  297-303. 

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The polylactic acid (PLA) and polylactic acid/hydroxyapatite whisker (HAw) composite porous scaffolds were fabricated through the solvent casting/vacuum evaporation/particle leaching method,using the sodium chloride as pore former,the chloroform as solvent.The surface morphology of polylactic acid are characterized by the SEM photographs.The XRD,SEM and Fr-IR,etc are employed to examine the composite morphology and structure characteristics of the polylactic acid with different quantity of HAw.Besides,we study the effect of the hydroxyapatite whisker contents on the hole structure parameters,mechanical properties and biological performance of the scaffolds material.The results reveal that the pore size and porosity of the scaffold can be controlled by the size and amount of the sodium chloride.The PLA/HAw series show the uniform structure,high porosity and good pore connectivity.The porosity of PLA/HAw composite porous scaffold ranges from 83.94; to 91.08;,which could meet the requirements of scaffolds for bone tissue engineering.The compressive strength of composite porous scaffolds is 5.72-12.73 MPa.Furthermore,the compressive strength reaches the maximum value of 12.73 MPa in 10; HAw/PLA.

Adsorption of NO2 Molecule on 4d Transition Metal Doped Graphene

DONG Hai-kuan;QI Yi-hui;LI Ming-biao;XIU Xiao-ming;SHI Li-bin

2017, 46(2):  304-310. 

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NO2 adsorption on graphene doped with 4d transition metal is investigated by the first principles based on density functional theory.It is observed that Cd atom cannot be doped into graphene due to saturated valence electron configurations of 4d10 5s2.Three kinds of NO2 adsorption configurations are investigated,in which N atom,one O atom and double O atoms in NO2 are close to the adsorption site,respectively.The most stable adsorption configuration is obtained by total energy optimization.NO2 adsorption can be studied by adsorption energy,charge transfer and other related data.The adsorption energy of NO2 adsorption on pure graphene is less than 0.2 eV.The adsorption ability is improved by doping 4d transition metal,and most of the adsorption energy is more than 2 eV.The effect of NO2 adsorption on Nb doped graphene is very good,and the adsorption system is relatively stable with the adsorption energy of 3.686 eV.Furthermore,by comparing the band structure change before and after NO2 adsorption,it is observed that Zr doped graphene change from semiconductor to metal after adsorption of NO2 molecule,and Nb doped graphene change from metal to semiconductor.

Synthesis of SiC-TiC Composite Powders Using Glucose as Carbon Source

HU Ji-lin;HU Chuan-yue;GUO Wen-ming;WANG Xue-cheng;TIAN Xiu-ying;PENG Yang-xi

2017, 46(2):  311-315. 

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SiC-TiC composite powders were synthesized in argon atmosphere by a carbothermal reduction method using silica sol,glucose and TiO2 as the raw materials.The effects of different reaction temperatures on phase composition,particle size distribution and microstructure of SiC-TiC composite powders were discussed.The synthesized powders were characterized by X-ray diffraction,laser particle size analyzer and scanning electron microscope.Results showed that the suitable conditions for synthesizing SiC-TiC composite powders were at 1550 ℃ for 2 h.The SiC-TiC composite powders synthesized at 1550 ℃ were composed of a small amount of flaky particles,a certain amount of whiskers and a large number of nearly spherical particles.The growth mechanism of SiC whiskers in powder samples followed the vapor-solid (VS) mechanism.

Preparation and Photocatalytic Performance of BiPO4 Using Different Phosphorus Source

LI Xiu-ping;ZHAO Rong-xiang;AI Dong

2017, 46(2):  316-322. 

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The three BiPO4 were prepared by ultrasonic technology.The rod BiPO4 were prepared with sodium hydrogen phosphate,the spindle BiPO4 were prepared with ionic liquid of imidazole-phosphate and the grain and rod BiPO4 synthesized by ionic liquid of triethylene tetramine-phosphate,respectively.The XRD indicate that peak of BiPO4 prepared in ionic liquid of triethylene tetramine-phosphate is highest,second in imidazole-phosphate and lowest in sodium hydrogen phosphate.UV-Vis shows the absorbent range of BiPO4 shift to high wavelength.The BET show special surface of BiPO4 are 3.9472 m2/g,11.548 m2/g and 24.063 m2/g in sodium hydrogen phosphate,imidazole-phosphate and triethylene tetramine-phosphate,respectively.Three BiPO4 have photocatalystic performance under ultraviolet.The photocatalytic activity of BiPO4 synthesized in triethylene tetramine-phosphate is highest.The experiments inspect the preparation and photocatalystic conditions of BiPO4.

Study on Purification Effect of Amorphous Silica Fume by Current Classification

ZHANG Shao-hong;TIE Sheng-nian

2017, 46(2):  323-328. 

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The current classifier was used as purification equipment to remove the impurities of silica fume.The optimal condition of process were explored:1:2 liquid-solid ration,four times of classification.the content of silicon oxide increased by 4.65;.Meanwhile,the element composition,recovery ratio,size distribution and particle morphology of silica fume were analyzed.The result shows that the content of C element reduces from 4.5; to 0.4;,removal rate over 90;,other impurity elements that in form of silicate or oxide are not removed;in optimal experimental condition,recovery ratio is 84.5;;average particle size increased from 0.334 μm to 0.557 μm;small particle were removed and particle size becomes more uniform,and the silica particle keep the original smooth spherical morphology.This is a green,environmental friendly waste recycle method which has small energy consumption and no change to the morphology,compared to the roasting process.

Study on the Thermoelectric Transport Properties of Al-doped ZnO Polycrystals

LIU Dan-dan;SONG Shi-jin;ZHANG Xue-feng;TAN Wen-peng;YU Lan

2017, 46(2):  329-333. 

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Zn1-x AlxO (0 ≤ x ≤ 0.005) polycrystalline bulks with hexagonal wurtzite structure were prepared by solid-state reaction method.The microstructure and thermoelectric properties of Zn1-xAlxO bulk were investigated.Doping Al makes ZnO grain increases and grain boundry decreases.The results show that the spinel ZnAl2 O4 appeared while x ＞ 0.003.The semiconductor behavior of bulks transform metallic behavior after Al doping in ZnO.Al doping is responsible for 1 orders of magnitude decrease of resistivety and the carrier concentration and mobility remarkable increase.At x =0.003 the minimum of resistivety is 1.7 mΩ · cm and the carrier concentration and mobility are maximum.The carrier concentration is 1.05 × 1021 cm-3.The mobility is 20 cm2/V · s at room temperature.The seebeck coefficient and power factor S2/p increases as the temperature increasing at 300-900 K.The maximum of the power factor is 0.4 mW/m · Ks at room temperature.The saturated solution of Al doping in ZnO is 0.003.

Study on Evaporation Process of CdSe Thin Films on Si Substrates

XIAO Fei;ZENG Ti-xian;YANG Hui;LIU Qi-ya;PEI Chuan-qi;ZHANG Min

2017, 46(2):  334-337. 

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CdSe nanocrystalline thin films were prepared by vacuum evaporation technique on the substrate of Si (100) under the different evaporation currents.The analysis and characterization of crystallization properties and surface morphology were carried out with the aid of modern analytical techniques,including XRD,thickness testing instrument and AFM.The results show that the evaporation current significant influence on crystalline properties and morphology of CdSe thin films.When the evaporation current is 75 A,the strongest diffraction apex was on the (002) crystal face,which exhibits an obvious growth advantage of the film with the c axis orientation,the thickness of film is about 160 nm and the grain size is about 40 nm.The sample surface for 75 A is smooth and crack-free with root mean square (RMS) roughness 5.63 nm.This results shown that the crystallization of the thin film is good.

Synthesis of Interconnected Nanometer Thick Magnesium Hydroxide Platelets on Porous Magnesium Substrate by Hydrothermal Method

ZHAO Xin;LI Meng

2017, 46(2):  338-343. 

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Interconnected nanometer thick platelets of magnesium hydroxide (Mg (OH) 2) were prepared on a sintered porous magnesium substrate by a hydrothermal method.Morphology and phase evolutions of the substrates during the reaction are investigated using scanning electron microscope (SEM) and X-ray diffraction (XRD).The results show that different denseness levels of interconnected magnesium hydroxide platelets with thicknesses of ～ 100 nm can be obtained by controlling the reaction time of the hydrothermal process within 20-40 min.Interconnected magnesium hydroxide platelets will grow and merge gradually into bulk crystal from the surface of the substrate.The nucleation and crystal growth mechanism of Mg(OH)2 during the hydrothermal reaction were discussed as well.

First-principles Study on Rare Earth Elements(Ce/Nd/Eu/Gd)and N Co-doped Rutile TiO2

2017, 46(2):  344-351. 

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The crystal structure,electronic structure and optical properties of pure rutile TiO2,Ce/Nd/Eu/Gd doped rutile TiO2,and Ce/Nd/Eu/Gd and N co-doped rutile TiO2 were investigated by the first-principles calculation method based on density functional theory.The results show that the unit cell expands,the lattice distorts in the doping systems.After doping the impurity into rutile TiO2,the Fermi level rises and gets through conduction band,and impurity level appears at the bottom of conduction band,which dues to improving the conductivity and the responsiveness of visible light.From the optical properties calculation,it is known that the peak of the curves of the dielectric function and the absorption spectrum is less than that of pure system,and the red shift appears in the reflectance spectrum and the energy loss spectrum.

Influence of ZrB2 Particle Size on Phase Composition, Microsturcture and Electrical Resistivity of Si3N4-ZrB2 Ceramics

LI Jing-Xi;WU Shang-Hua;GUO Wei-Ming;WU Li-Xiang

2017, 46(2):  352-355. 

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Si3N4-ZrB2 ceramics were fabricated by hot pressing at 1500 ℃,using the coarse and fine 20vol;ZrB2 powders as conductive phase,and 3vol; MgO-2vol; YB2O3 as sintering additive.The effect of ZrB2 particle size on the densification,phase composition,microstructure and electrical resistivity was studied.The result show that dense Si3N4-ZrB2 ceramic could be obtained with the introduction of MgO-YB2O3 additives,being independent of ZrB2 particle size.When coarse ZrB2 powders were used as raw material,the Si3N4-ZrB2 ceramics contained main α-Si3N4,β-Si3N4,ZrB2 phase and weak Yb4Si2N2O7 phase;ZrB2 grains isolated from each other,the electrical resistivity is about 9.5 × 103 Ω · m.However,using fine ZrB2 powders as raw material,Si3N4-ZrB2 ceramics contained newly weak ZrSi2 and ZrN conductive phase,in addition to main α-Si3N4,β-Si3N4,ZrB2 phase,and weak Yb4Si2N2O7 phase,the Si3N4-ZrB2 ceramics contained newly weak ZrSi2 and ZrN conductive phases due to weak reaction of ZrB2 with Si3 N4.The electrical resistivity was obviously decreased to 6.8 Ω · m due to the ZrB2 grain connection.

Preparation of Zn-Sr-HA Microspheres by Hydrothermal Homogeneous Precipitation Method

WANG Ping;LI Guo-chang

2017, 46(2):  356-360. 

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Changing Zn/Sr molar ratio and hydrothermal reaction time of the reaction solution,the strontium and zinc substituted hydroxyapatite (Zn-Sr-HA) microspheres were successfully prepared via hydrothermal method.The structure,composition and morphology of microspheres were studied by optical microscopy,X-ray fluorescence spectrometry (XRF),X-ray diffraction (XRD) and field emission scanning electron microscope (SEM).The results show that the products are all composed of HA microspheres when the Zn/Sr molar ratio is 3:2 or 1:1 in the initial solution at reaction temperature 180℃ for 3 h to 4 h.The average diameter of microspheres is about 10 μm to 20 μm,with uniform size and good dispersion.With the increase of the molar ratio of Zn/Sr in the initial solution,the Zn/Sr molar ratio of HA microspheres increase gradually,and the cell parameters a and c values decrease gradually.

Photocatalytic Degradation Behavior of Sm2O3/TiO2 for Methylene Blue Dye

ZHENG Xiao-gang;WANG Shu-xian;FU Wen-di;RONG Jing;HUANG Min;FU Xiao-jin;LIU Yong;YOU Yao-hui

2017, 46(2):  361-367. 

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The supported catalysts Sm2O3/TiO2,Sm2O3 doped TiO2 bulks,were synthesized by impregnation method,and employed to investigate the photodegradation behaviors of methylene blue under UV-light irradiation.The fabricated Sm2O3/TiO2 samples were characterized by several techniques such as XRD、SEM、TEM、N2-adsorption,XPS,ICP-OES.The effects of experiential parameters such as Sm2O3 content and methylene blue concentration on the photocatalytic degradation performance in methylene blue as well as photocatalytic stability were also performed.The results show that Sm2O3/TiO2 exhibited higher photocatalytic activity for methylene blue compared with TiO2-alone under UV-light region,which is ascribed to the crystal defect of TiO2 generated by Sm2O3 doping.This crystal effect,as the trap of photo electrons and holes,can achieve the effective separation of electron-hole pairs,landing to the enhancement in photocatalytic activity of Sm2O3/TiO2 samples.The photodegradation activity of Sm2O3/TiO2 increases and then decreases as Sm2O3-doped content increasing,while decreased with methylene blue concentration.Sm2O3/TiO2 samples with Sm2O3-doped content of 5.0wt; did not exhibit an evident loss of activity for the UV-light droved degradation of methylene blue after seven cycles under the same conditions.

Preparation and High-temperature Electrical Properties of Calcium-stabilized Zirconia

TIAN Li-ping;XUE Qun-hu;REN Wei-kang

2017, 46(2):  368-373. 

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The calcium-stabilized zirconia materials were prepared by using high-purity monoclinic zirconia powders as raw material,and adding various content of 4mol; 、8mol; and 12mol; CaO as stabilizer,respectively,the high-temperature conductivity of calcia-stabilized zirconia was investigated.After shaped by compression molding process and then sintered at 1710 ℃ for 2 h,the phase composition and microstmcture of the obtained samples were characterized through X-ray diffractometer and scanning electron microscope,and then the conductivity of zirconia materials was tested from room temperature to 1350 ℃.The results show that the content of cubic zireonia increases,while the content of the monoclinic phase decreases obviously as the addition of stabilizers increasing.The conductivity value of the sintered samples increases as the content of CaO and testing temperature increasing.The difference of phase composition results in the different conductivity whenever at lower or higher temperature zones for the calcia-stabilized zirconia,and the increase of the cubic phase content is helpful to improve the conductivity value.

Application of Grey Theory to Flotation Experiment

ZHAO Min-jie;FANG Jian-jun;ZHANG Lin;DAI Zong;YAO Zhang-wei

2017, 46(2):  374-380. 

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The feasibility of Grey theory analysis in mineral flotation experiment was discyssed.A response surface methodology model was established for malachite flotation.The dosage of sodium sulphide,isoamyl xanthate and ammonium sulfate was chosed as independent variable and recovery as dependent variable by the designing scheme of CCD.The results show that significance from large to small are as isoamyl xanthate,ammonium sulfate and sodium sulphide.Grey theory model was established based on the data of Response Surface Methodology,The dosage of sodium sulphide,isoamyl xanthate and ammonium sulfate was chosed as comparison sequence and recovery of malachite fotation as reference sequence,The correlation degree analysis of three reagent dosage are in accordance with the Sorting of significant of Response surface method.The result indicate that Grey theory analysis can be applied to flotation experiment as a useful method to learn.

Analysis of Defect States for Spoof Surface Acoustic Waves Based on Finite Element Method and Supercell Method

XIE Su-jun;OUYANG Shi-liang;DENG Ke;ZHAO He-ping

2017, 46(2):  381-384. 

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The point defect and line defect band structure of spoof surface acoustic waves were calculated by the finite element method and the supercell method,and acoustic confinement and waveguiding of surface phononic crystals with defect states were analyzed theoretically.The surface phononic crystal is composed of rigid surface with periodic grooves.Point defects and line defects can be introduced by changing the geometrical parameters of single groove in the core center or one row of grooves.Furthermore,combining the finite element method and the supercell method,it is very convenient to calculate the band structure of point defects and line defects,and obtain the eigen-pressure field of spoof surface acoustic waves which localized in the point defects and the line defects with specific frequency.By analyzing the defect band structure and eigen-pressure field diagram,we can intuitively understand the acoustic confinement and acoustic waveguides in the surface phononic crystal with defect states.

Effect of Excitation Power Density and Well Thickness on Photoluminescence Properties of InGaN/GaN Multiple Quantum Well

ZHANG Zheng-yi;LIANG Jiang;WU Wei

2017, 46(2):  385-392. 

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The growth of InGaN/GaN multiple quantum wells with different well thickness grown on cplane sapphire substrate by MOCVD was reported.The dependence of photoluminescence on excitation power density and well thickness was obtained.All samples exhibited an excitation-induced blueshift of the peak emission with the increase of excitation power density,and a larger blueshift of MQWs with wider well was measured.The shift of PL peak position with increasing excitation power density and well thickness can be clarified by the model of band filling effect and shielding of built-in field.The thinnest well LED sample (1.8 nm) has the highest optical output power,which is due to the weakest built-in field,however,its emitting wavelength is only 430 nm.