Microstructure and dielectric properties of BaTi_4 O_9 (f)/0.64 BaTi_4 0_9+0.36 BaPr_2 Ti_4 O_(12) composites

The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti~(3+) and Ti~(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10~(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.     

Surface Nanocrystallization of C45E4 Steel by Ultrafast Electropulsing-ultrasonic Surface Treatment

The effect of high-energy electropulsing-ultrasonic surface treatment(EUST) on the surface properties and the microstructure evolution of C45 E4 steel was investigated. Refined microstructure and reduced surface roughness were obtained owing to the surface nanocrystallization process. Compared with the ultrasonic surface treatment(UST), the impact depth of the surface strengthened layer was increased by 40% to 700 μm after EUST. The average grain size of the surface nanocrystallization layer was reduced to 30-50 nm. The surface roughness of the C45 E4 steel was reduced to 0.25 μm, and the surface microhardness was dramatically enhanced to 460 HV. The improvement of microstructure and micro-hardness at ambient temperature was likely attributed to the acceleration of atomic diffusion and the enhancement of plastic deformation ability in the surface strengthened layer under the influence of electropulsing. Due to the electropulsing-assisted ultrasonic strengthening effect, the surface nanocrystallization in this ultrafast procedure was noticeably enhanced.     

Structures and magnetic properties of nanocomposite CoFe_2O_4-BaTiO_3 fibers by organic gel-thermal decomposition process

The nanocomposite xCoFe2O4-(1-x)BaTiO3(x=0.2,0.3,0.4,0.5,molar fraction) fibers with fine diameters and high aspect ratios(length to diameter ratios) were prepared by the organic gel-thermal decomposition process from citric acid and metal salts.The structures and morphologies of gel precursors and fibers derived from thermal decomposition of the gel precursors were characterized by Fourier transform infrared spectroscopy,X-ray diffractometry and scanning electron microscopy.The magnetic properties of the nanocomposite fibers were measured by vibrating sample magnetometer.The nanocomposite fibers consisting of ferrite(CoFe2O4) and perovskite(BaTiO3) are formed at the calcination temperature of 900 ℃ for 2 h.The average grain sizes of CoFe2O4 and BaTiO3 in the nanocomposite fibers increase from 25 to 65 nm with the calcination temperature from 900 to 1 180 ℃.The single fiber constructed from these nanograins of CoFe2O4 and BaTiO3 has a necklace-like morphology.The saturation magnetization of the nanocomposite 0.4CoFe2O4-0.6BaTiO3 fibers increases with the increase of CoFe2O4 grain size,while the coercivity reaches a maximum value when the average grain size of CoFe2O4 is around the critical single-domain size of 45 nm obtained at 1 000 ℃.The saturation magnetization and remanence of the nanocomposite xCoFe2O4-(1-x)BaTiO3(x=0.2,0.3,0.4,0.5) fibers almost exhibit a linear relationship with the molar fraction of CoFe2O4 in the nanocomposites.     

Beckmann Rearrangement of Erythromycin A 9（E）－Oxime

9-Deoxo-6-deoxy-6, 9-epoxy-9, 9α-didehydro-9α-aza-9α-homoerythromycin A ( 1 ), 9-deoxo-11-deoxy-9, 11-epoxy-9, 9α-didehydro-9α-aza-9α-homoerythromycin A (2) and 9α-aza-9α-homoerythromycin cyclic lac-tam (3) were synthesized by the Beckmann rearrangement of erythromycin A 9(E )-oxime (4). The structures of compounds (1), (2) and (3) have been identified by their spectral data. The reaction mechanism was also dis-cussed. The yield of the Beckmann rearrangement of compounds (4) was better than that reported in literatures.     

Effects of Si and Ce on the microstructure and hydrogen storage property of Ti_(26.5)Cr_(20)V_(45)Fe_(8.5)Ce_(0.5) alloy

In this paper, the effects of Si and Ce on the microstructure and hydrogen storage property of Ti26.5 Cr20V45Fe8.5Ce0.5 alloy were studied, respectively. First of all, effects of Si on the microstructure and hydrogen storage properties of Ti26.5Cr20(V45Fe8.5)1?xSixCe0.5 (x = 0, 0.5, 1.0, 1.5 and 2.0 at%) alloys were studied by X-ray diffraction, scanning electron microscopy and P-C isotherm measurements. As the Si addition increases, the hydrogen absorption capacities of alloys decrease but the equilibrium pressure increases, due to the formation of Laves phase. Secondly, the effect of Ce on Ti26.5Cr20 (V45Fe8.5)0.98Si2 alloy was studied. It was found that Ce addition is an effective way to eliminate the effect of Si on the hydrogen storage properties of the alloy.     

Microstructure Evolution and Dynamic Mechanical Properties of Laser Additive Manufacturing Ti-6Al-4V Under High Strain Rate

The dynamic mechanical properties of the Ti-6Al-4V (TC4) alloy prepared by laser additive manufacturing (LAM-TC4) under the high strain rate (HSR) are proposed. The dynamic compression experiments of LAM-TC4 are conducted with the split Hopkinson pressure bar (SHPB) equipment. The results show that as the strain rate increases, the widths of the adiabatic shear band (ASB), the micro-hardness, the degree of grain refinement near the ASB, and the dislocation density of grains grow gradually. Moreover, the increase of dislocation density of grains is the root factor in enhancing the yield strength of LAM-TC4. Meanwhile, the heat produced from the distortion and dislocations of grains promotes the heat softening effect favorable for the recrystallization of grains, resulting in the grain refinement of ASB. Furthermore, the contrastive analysis between LAM-TC4 and TC4 prepared by forging (F-TC4) indicates that under the HSR, the yield strength of LAM-TC4 is higher than that of F-TC4.     

A Novel Fluorescence Probe 9-（4-（1,2-diamine）benzeneN 1-phenyl）acridine for Nitric Oxide Determination

A novel fluorescent probe 9-(4-(1,2-diamine)benzene-N1-phenyl)acridine(DABPA) was synthesized for the detection of nitric oxide(NO) and characterized by IR, 1H-NMR and EI-MS spectroscopy. Based on a photoelectron transfer mechanism, the fl uorescence intensities of DABPA were investigated with the different concentrations of NO. Under the optimal experimental conditions, the fl uorescence intensity of DABPA had a good linear relationship(R2=0.9977) with NO concentration in the range from 1×10-7 to 1.5×10-6 mol/L with a detection limit of 1×10-8 mol/L. The cytotoxicity induced by DABPA was evaluated by the MTT(3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide) assay for biological application. Furthermore, the probe DABPA had also been successfully applied to real-time image NO produced in PC12 cells in the presence of L-arginine.     

Effect of sulphate-reducing bacteria on the electrochemical impedance spectroscopy characteristics of 1Cr18Ni9Ti

The electrochemical characteristics of 1Cr18Ni9Ti in sulphate-reducing bacteria (SRB) solutions and the biofilm of SRB on the surface of the 1Cr18Ni9Ti electrode were studied by electrochemical, microbiological, and surface analysis methods. Electro- chemical impedance spectroscopy (EIS) of 1Cr18Ni9Ti was measured in the solutions with and without SRB at the culture time of 2, 4, 8 d, respectively. The measurement used two test methods, the nonimmersion electrode method and the immersion electrode method. It was found that the polarization resistance (Rp) of 1Cr18Ni9Ti in the solutions without SRB is the greatest for each test method. When using the nonimmersion electrode method, Rp shifts negatively at first and then positively, and the time constant is only one. Although using the immersion electrode method, the Rp shifts positively at first and then negatively, and the time constant also changes when the biofilm forms. The biofilm observed through SEM is with pores. It was demonstrated that SRB has acceler- ated corrosion action on 1Cr18Ni9Ti. The protection effect of the biofilm on the electrode depends on the compact degree of the film.     

Gas sensitivity of poly (3, 4-ethylene dioxythiophene) prepared by a modified LB film method

An arachidic acid/poly (3, 4-ethylene dioxythiophene) (AA/PEDOT) multilayer Langmuir-Blodgett (LB) film was prepared by a modified LB film method. The theories were utilized to explain the effects between HCl molecule and LB film. The gas sensitivity mechanism of poly (3, 4-ethylene dioxythiophene) (PEDOT) multilayer film can be explained by the charge transfer between p system of PEDOT and oxidization HCl system. The gas sensitivity of PEDOT LB film deposited interdigital electrode to HCl was tested. The results showed that film thickness, treating temperature, deposition speed had different influence on film gas sensitivity. The AA/PEDOT film deposited device exhibited nonlinear behavior to HCl gas at lower concentration (20-60 ppm) and linear response behavior at higher gas concentration was observed. The time of the compound LB film of the AA/PEDOT responding to the 30 ppm HCl gas is about 20 seconds, which is far quicker than the time of the film to the PEDOTPRESS film(about 80 seconds). It is not higher film press to better film. When the film press attains 45 mNs/m, the sensitivity of the AA/PEDOT film on the contrary descends.     

Syntheses and applications of Eu（Ⅲ） complexes of 2-thienyltrifluoroacetonate, terephthalic acid and phenanthroline as light conversion agents

A series of europium(Ⅲ) complexes of 2-thienyltrifluoroacetonate (HTTA), terephthalic acid (TPA) and phenanthroline (Phen) were synthesized. The new complexes Eu(TPA)(TTA)Phen and Eu2(TPA)(TTA)4Phen2 were characterized by elemental analysis, IR spectrum, scanning electron microscope and thermal stability analysis. The results show that the thermal stability of the Eu( Ⅲ ) complexes increases in the following order: the mononuclear complex Eu(TTA)3Phen, the binuclear complex Eu2(TPA)(TTA)4Phen2, the chain polynuclear complex Eu(TPA)(TTA)Phen. And the formation of the binuclear/polynuclear structure of the new complexes appears to be responsible for the enhancement of their thermal and optical stability. In addition, The fluorescence excitation spectra of these new complexes show more broad excitation bands than that of the complex Eu(TTA)3Phen corresponding to their formation. The enhancement of Eu3 fluorescence in the new complexes can be observed by the addition of Gd3 . The bright red luminescent plastics can be obtained when the complex EuGd(TPA)(TTA)4Phen2 is added above 0.5% (mass fraction).     

Electrochemical determination of Gibbs free energy of formation of magnesium ferrite

The standard Gibbs free energy of formation of magnesium ferrite was determined by means of two types of solid state electrochemical cells: one using MgZr4(PO4)6 (MZP) as the solid electrolyte and the other using CaF2 as the solid electrolyte. The first cell was operated in the range of 950 to 1100 K. The second cell was operated in the range of 1125 to 1200 K. The reversibility of the cell EMFs was confirmed by microcoulometric titration. The Gibbs energy changes of magnesium ferrite relative to component oxides were calculated based on EMF measurements and are given by following expressions, respectively: △G(o)Ⅰ = -3579-15 T (J/mol) and △G(o)Ⅱ =6258-24.3 T (J/mol). The results obtained from two different cells are consistent with each other. The results also are in agreement with Rao's and Tretjakov's data in the measured temperature range. When the Gibbs free energies of formation of MgO and Fe2O3 were substituted in the reaction, the Gibbs free energies of formation of MgFe2O4 was obtained in two temperature ranges and the formations are shown as follows: △G(o)Ⅰ Formation = -1427394 360.5 T (J/mol) and △G(o)Ⅱ Formation = -1417557 351.2 T (J/mol).     

BAYER LIQUORS IN ALUMINA REFINERIES STUDIED BY FOURIER TRANSFORM INFRARED SPECTROSCOPY

Abstract:The assignments of the absorption peaks in the Fouriertransform infrared (FTIR)spectra of the Bayer liquors were established inthis study,which provided the basis for the study of Bayer liquors byFTIR techniques.The FTIR study of the Bayer liquors from two aluminarefineries indicated that both liquors contained carbonate,humate andAl(OH)_4~-ions.The existence of sulphate ions in one of the liquors was alsodiscovered.     

Orbital Calculations of Kaolinite Surface:on Substitution of Al~(3 ) for Si~(4 ) in the Tetrahedral Sites

The surface properties of kaolinite were determined using density functional theory discrete variational method(DFT-DVM)and Gaussian 03 program.A SiO_4 tetrahedral hexagonal ring with two Al octahedra was chosen to model the kaolinite crystal.The total density of states of the kaolinite cluster are located near the Fermi level at both sides of the Fermi level.Both the highest occupied molecular orbit (HOMO)and the lowest unoccupied molecular orbit(LUMO)of kaolinite indicate that kaolinite system can not only readily interact with electron-acceptor species,but also readily interact with electron-donor species on the edge surface and the gibbsite layer surface,and thus,shows amphoteric behavior.Substitution of Al~(3 ) for Si~(4 ) in the tetrahedral site linking the vacant Al~(3 ) octahedra does not increase the surface chemical reactivity of kaolinite,while substitution of Al~(3 ) for Si~(4 ) in the tetrahedral site with the apex O linking Al~(3 ) octahedra increase the surface chemical reactivity of the siloxane surface of kaolinite,especially acting as electron donors. Additionally,substitution of Al~(3 ) for Si~(4 ) in the tetrahedral site results in the re-balance of charges,leading to the increase of negative charge of the coordinated O atoms of the AlO_4 tetrahedra,and therefore favoring the formation of ionic bonds between cations and the surface O atoms in the basal plane.     

STUDIES ON THE BIODEGRADATION MECHANISM OF β-TRICAICIUM PHOSPHATE CERAMICS

In order to clarify the biodegradation mecha-nism of β-tricalcium phosphate(β-TCP)ceramics,In vitroand In vivo experiments have been carried out.Nanometricmicroelectrodes were applied to measure the pH values in-side and outside phagocytes which were cultured for 72hours respectively in β-TCP-bearing and β-TCP-free medi-um.Radioactive isotope~(45)Ca was used to trace the distribu-tion and metabolism process of degraded products.We foundthat the degradation of β-TCP ceramics was due to the dis-solving process in body fluid and the degrading process me-diated by cells.After β-TCP ceramics labellbd by~(45)Ca wereimplanted into rabbits,radioactive~(45)Ca was tested in blood,faece and organs such as heart,kidney and stomach etc.Itwas also found in the nearby new bone.So,we think a smallpart of the degraded products enter the animal’s blood andtake part in the metabolism of body.Others are reused toform new bone.The reports from clinical application alsogave us strong support.     

Synthesis and Characterization of Shape Memory Polyurethane for Deployable Structures

A series of shape memory polyurethane elastomers(SMPUs) were synthesized by altering the chain extenders.The reaction was proceeding by solution prepolymerization method.Infrared spectra(IR),Differential scanning calorimetry(DSC) and specific viscosity method were carried out to examine the structure,glass transition temperature(Tg) and molecular weight of these SMPUs.The shape memory abilities and tensile properties of the material were investigated simultaneously.The IR results showed that the SMPUs were successfully synthesized and the Tg of the samples were all above 45 ℃ according to the DSC test.All the samples can recover to its original shape completely after bending to 180°.Tensile properties were tested on the samples.The sample MDI/PBAG/BDO with the mole ratio 4/1/3 gets the best tensile strength and highest ultimate elongation.     

Photocatalytic properties of thin films of ruthenium metallopolymers/gold nanoparticle: Polyoxometalate composites using visible excitation

Thin layers of an electrostatically associated adduct RuPVP-AuNP:POM formed between the polyoxomolybdate, [S2 Mo18 O62 ]4, the polycationic metallopolymer [Ru(bpy)2(PVP)10 ](ClO4)2 and DMAP-protected gold nanoparticle have been deposited onto electrodes using two separate methods, alternate immersion layer-by-layer assembly and pre-assembled drop-casting; PVP is poly(4-vinylpyridine), BPY is 2,2’-bipyridyl, and DMAP is 4-dimethylaminopyridine. Significantly, the efficiency of the photocatalysis depends markedly on the structure of the [RuPVP-AuNP:POM] even when photonic properties are very similar. Strikingly, despite their similar photonic properties, an additional optical transition is observed in UV-vis and the Raman spectra of pre-assembled drop cast [RuPVP-AuNP:POM], which was not seen in dip coated [RuPVP-AuNP:POM]. Importantly, this electronic communication enhances the photocatalytic oxidation of benzaldehyde by a factor of more than four. While there is clear evidence for photosensitisation in the drop cast not present for the dip coated systems, the magnitude of the photocurrent, i.e.,(82.2 6.6) nA·cm 2for pre-assembled drop cast [RuPVP-AuNP:POM] at a ruthenium to Au nanoparticle mole ratio of 48:1, is twice as large as that those found in [Ru-PVP:POM] film.     

Mechanical behaviors of polycrystalline NiTi SMAs of various grain sizes under impact loading

This work presents mechanical properties of the NiTi polycrystalline superelastic shape memory alloys(SMA) of 5 different grain sizes under high-speed impacts. The amorphous, nanocrystalline(40, 80, 120 nm) and coarse grain(20 μm) sheets are manufactured with cold rolling and suitable heat treatments. A Hopkinson tensile bar is used to perform tests up to 45 m/s. Highspeed camera system and digital image correlation method are used to get the strain field and particle velocity field at a sampling frequency of 2×10~6 frames/s with a resolution of 924×768 pixels. Nominal stress-strain curves are obtained for all the sheets with a strain rate of about 1000 s~(-1) and they have a similar evolution to the quasi-static case but with much higher stress levels. The rate sensitivity is increased with the grain size and the stress level can reach up to a 70% growth for a coarse grain sheet but be totally insensitive for the amorphous sheet in the strain rate from 10~(-4) to 10~3 s~(-1). A single transformation front can be found under high-speed impact(45 m/s) at the early loading stage. The speed of the transformation front is calculated from strain time histories and the highest front speed of 811 m/s is observed which is never observed before. It also reveals that the front speed depends also on the grain size. With the same loading speed, the bigger the grain size is, the slower the transformation front speed is.     

First-principles study on electronic structure,magnetic and dielectric properties of Cr-doped Fe_3C

The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show that the thermodynamic stability of Crdoped Fe_3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe_3C, Fe_(11)CrC_4(g), and Fe_(11)CrC_4(s) are respectively 21.36 μB/cell, 16.92 μB/cell, and 17.62 μB/cell, and in Fe_(11)CrC4(g) and Fe_(11)CrC_4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe_(11)Cr C_4(s)Cr_3CFe_(11)Cr C_4(g)Fe_3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.     

Lower temperature synthesis of cerium-doped polycrystalline lutetium pyrosilicate powders by a novel sol-gel processing

A novel sol-gel processing was developed to synthesize polycrystalline cerium-doped lutetium pyrosilicate(Lu2Si2O7:Ce,LPS:Ce)powders under low temperature.It was found that the addition of propylene oxide(PPO)could promote the formation of Lu-O-Si bonds in precursor,which was beneficial to the formation of LPS phase.X-ray diffraction(XRD)patterns indicated that the single-phased LPS powder was well crystallized at 1050°C.Microstructure observation demonstrated that the synthetic LPS powder was composed of ellipsoidal grains with the mean size of 40 nm.The luminescent properties were characterized by photoluminescence(PL),X-ray excited luminescence(XEL)and vacuum ultraviolet(VUV)spectroscopy at room temperature.The synthetic LPS:Ce powder emitted a broad emission spectrum centered at about 380 nm,which should be ascribed to the 5d→4f transition of Ce3+.Decay time of the synthetic LPS:Ce powder was measured to be only 32 ns.     

Synthesis and Structural Analysis of LDH-SO_4-CO_3 Whisker

High-quality LDH-SO_4-CO_3 whiskers were synthesized via liquid precipitation method using MgSO_4·7 H_2 O and Al_2(SO_4)_3·18 H_2O as precursors and Na_2CO_3-NaHCO_3 buffer solution as precipitant. The influence of buffer solution concentration on the characteristics of the samples was investigated. The asgrown whiskers were characterized by X-ray diffraction, transmission electron microscopy, and BrunauerEmmett-Teller N_2 specific surface area measurements. The results show that the buffer solution concentration has significant impact on whiskers with intercalated structure. The LDH-SO_4-CO_3 whiskers with well-defined geometry, distinct intercalated structure, decent quality, and excellent dispersing capability can be obtained under the following conditions: buffer solution volume ratio of 45%, reaction temperature of 83°C, and reaction time of 182 h. The obtained whiskers are well-crystallized and exhibit homogeneous morphology consisting of fiber bars.