Fabrication of niobium doped Pb（Zr, Ti）O3 fibers by viscous polymer processing

A technique based on viscous polymer processing （VPP） was described, which can produce high ceramic content green fibers. PZT-5 ceramic powders were ball milled to get high dispersibility. The slurry prepared for VPP was a composition of PZT-5 powder, PVA binder and glycerin. High ceramic content PZT-5 fibers were extruded with the slurry. The results show that the ceramic powders have fine mean particle size of 0.54 pan, high specific surface area of 3.55 m^2/g and zeta potential of 8.81 mV after 16 h milling. The fibers sintered at 1 280 ℃ for 4 h have pure perovskite structure and grains of 2-5 μm in size, with little pores or cracks. The ultimate tensile strength of sintered fibers is up to 13.84 MPa compared with 2.88 MPa of green fibers. The remnant polarization （Pr） and coercive field （Ec） of the fibers are 50.65 μC/cm^2 and 2.45 kV/mm, respectively. This fiber can withstand an electric field of 9 kV/mm higher than the ceramic （5 kV/mm）, which shows high directional and compact qualities.     

Fabrication and properties of low oxygen grade Al2O3 dispersion strengthened copper alloy

The low oxygen grade Al2O3 dispersion strengthened copper alloy without hydrogen-fired expansion was fabricated by the technique of vacuum hot press and hot extrusion. The mechanical and electrical properties measurements and microstructures observation on as-hot extruded, as-cold drawn and as-annealed Cu-Al2O3 alloy were conducted. The results show that the addition of a suitable amount of boron in the alloy can lower the residual free oxygen content and then inhibit the hydrogen-fired expansion. The density, σb, σ0.2, hardness, δ and electrical conductivity of the alloy reach 8.86 g/cm^3 (relative density of 99.6%), 340MPa, 250MPa, HB95,24% and 93%(IACS) respectively after hot extruded with the extrusion ratio of 30:1. Its properties have no change after annealed at 900℃ for 1h. Its strength increases after cold drawing, while its ductility and electrical conductivity drop gradually. Various properties of the cold drawn alloy can recover to those of as-extruded after annealed at 900℃ for 1h without the occurrence of recrystallization.     

Electroless nickel plated graphite fibers and surface behavior in Gr（Ni）/6061 Al composite

The electroless nickel plated graphite fibers reinforced aluminum matrix composites （Gr（Ni）/Al） were produced by squeeze casting, and the microstructure of Gr（Ni）/Al composite and surface behavior of Ni-P coating were studied. The optimum process of electroless Ni-P plating included： burning to get rid of glue→degreasing→neutralization→acidulating→sensitizing→activation→ electroless plating. The surface analysis results show that the electroless nickel plating can diffuse into the graphite fiber surface during the squeeze casting, and the Ni-P coating and aluminum alloys can produce brittle phase NiAl3 or NiAl. The X-ray diffraction（XRD） results indicate that Al4C3 is so little that no Al4C3 peaks are found, and the harmful Al4C3can be decreased by the electroless plating Ni-P coating. The coating improves the interfacial bonding of continuous graphite fibers reinforced aluminum matrix composites.     

Structure and bonding orientation of favorable growth unit Al6（OH）18（H2O）6 of gibbsite

1INTRODUCTION Thecrystalgrowthcharacteristicsofgibbsite insupersaturatedsodiumaluminatesolutionwere extensivelyinvestigated[15],butthestructureand formofthegrowthunitwerenotrelated.Firstly,Vanstratenetal[6]indicatedthatthegrowthunit transitionstateofaluminateacidradicalexistedin thecrystallizationofgibbsitefromalkalinesodiumaluminatesolution.Parkinsonetal[7]figuredout thatAl(OH)-4,Al(OH)2-5andAl(OH)3-6would belikelytobecomegrowthunitsofgibbsitefromtheviewpointofcrystalsurfacebindingene…     

Fluorescence and preparation of Sr2（P2O7）：Ce,Tb phosphate by co-precipitation method

The micron-sized Sr2（P2OT）：Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-pre-cipitates of （NH4）2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, trans-mission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 ℃ is Sr2（P2O7）：Ce,Tb, which belongs to ortho-rhombic phase. The powder is spherical and the size dis-tribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0：0.4：0.6 shows the best fluores-cence effect annealed at 1,100 ℃ for 3 h. The phosphors produce green fluorescence by being excitated with ultra-violet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr2（P2O7）：Ce,Tb phos-phors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.     

Efects of Washing and Drying on Crystal Structure and Pore Size Distribution（PSD） of Zn4O13C24H12 Framework（IRMOF-1）

In this study,the efects of various methods of washing and drying of MOF-5 nanocrystals on structure formation were investigated.Eight samples of MOF-5 were synthesized under diferent conditions.TGA,XRD and PSD analysis were applied to characterize of the samples.The methods of washing and drying were found to be important in determining the final structure of MOF-5s.MOF-5 with high BET surface area can be obtained by choosing a suitable method of washing and drying.According to the results obtained in this work,it was found that vacuum drying at 425℃ is sufcient to dissolve the MOF-5-DMF.Similar results were obtained by washing method(with℃H2Cl2and℃HCl3),when compared with vacuum drying at 425℃ according to XRD test.The pore size distribution of samples 1-5 and 8 were calculated by SHN1 method and results showed that the samples in which solvent vacuum was DMF,have lower pore volume,uniform pore size distribution and the pore size are smaller than samples 3,4 and 8.It was also found that activated MOF-5can be converted to its deactivated form prior to drying of the samples.     

Influence of CaF2 on the structure and dielectric properties of Ag（Nb0.8Ta0.2）O3 ceramics

Ag(Nb0.8Ta0.2)O3 ceramics were prepared by the traditional solid-state reaction method. The effect of CaF2 addition on the structure and di-electric properties of Ag(Nb0.8Ta0.2)O3 ceramics was investigated. The addition of CaF2 led the ceramics to a larger grain size and distortion of lattice. With the addition of 4.5 wt.% CaF2, the permittivity of the ceramics increased from 442 to 1028, the dielectric loss decreased sharply from 6.12 × 10-3 to 8.6 × 10-4, and the temperature coefficient of capacitance decreased from 1834 ppm/°C to-50 ppm/°C (at 1 MHz). These results indicated that the high permittivity was related with a large grain size, a low grain boundary density, and the weak Ta-O or Nb-O bond strength caused by the addition of CaF2.     

Preparation and spectroscopic, and thermal decomposition kinetic studies of europium（Ⅲ） complex [Eu（HNBD）3] （HNBD： 1-（6-hydroxy-1-naphthyl）-1,3-butanedione）

The complex of Eu（IH） with 1-（6-hydroxy- 1-naphthyl）- 1,3-butanedione （HNBD） was prepared for the first time and characterized by elemental analysis, IR, UV, fluorescence spectrum, and DTA-TG-DTG techniques. The IR and UV-visible spectra showed that Eu（Ⅲ） ion was coordinated to the HNBD ligand. The fluorescence spectrum showed the presence of Eu^3＋ characteristic emission. The TG-DTA-DTG curves showed that the thermal decomposition of the anhydrous complex was a two-stage process and the final residue was Eu2O3. The thermal decomposition kinetic parameters of the complex were evaluated from TG-DTG data by using three kinds of integral methods （Coat-Redfem equation, Horowitz and Metzger equation, Madhusudanan-Krishnan-Ninan equation）. The kinetic parameters of the first stage are E^＊ = 164.02 kJ.moll, A = 1.31 × 10^15 s^-l, AS^＊= 42.27 J·K^-l·mol^-l, △H^＊ = 159.51 kJ·mol^-l, △G^＊= 136.54 kJ·mol^-l, and n = 3.1, those of the second stage are E^＊= 128.52 kJ·mol^-l, A = 1.44× 106 s^-1, △S^＊= - 136.89 J·K^-l·mol^-l, △H^＊ = 120.41 kJ·mol^-l, △G^＊= 283.85 kJ·mol^-l, and n = 1.1.     

Calculation on Relation of Energy Bandgap to Composition and Temperature for Ga_xIn_（1－x）As_（1－y）Sb_y

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Preparation and electrochemical properties of LiMn1.95M0.05O4 （M=Cr, Ni）

The preparation process and electrochemical properties of LiMn2O4 and LiMnl.95M0.05O4 （M = Cr, Ni） were studied. The results show that the decomposition temperature range of xerogel prepared with lithium acetate and manganese acetate as raw rnaterials is large and the decomposition speed is slow. Oxygen consumed is apt to get a prompt supplement during the preparation of LiMn2O4, and carbonization of the organic matter can be reduced or avoided, which is favorable to the combination of lithium and manganese. Using lithium acetate, manganese acetate, chromium nitrate, and nickel nitrate as raw materials and adopting the citric acid complexing method, it has been found that the prepared powders have high purity, high quality stability, and even doping characters. With the increase of sintering temperature, the particle size and crystal lattice constant of LiMn1.95M0.05O4 （M = Cr, Ni） enhance. However, the purity of the product is relatively high and has no obvious change, which is advantageous to the control of the quality of LiMn1.95M0.0504 （M = Cr, Ni）. Doping with a small amount of Cr3. and Ni^2＋ can stabilize the spinel structure of LiMn2O4, suppress the Jahn-Teller effect, and improve the cycling properties but reduce the initial capacity.     

Loading effect at oxygen plasma etching of fabric of polyethylele terephtalate monofilament fibers

The results of studying the effect of loading under the low-temperature action of oxygen plasma on the surface of Italian fabric of polyethylene terephthalate monofilament threads are presented. Gravimetric and mass-spectrum techniques (mass spectrometer IPDO-2A) were used in this work. When the contact times of the plasma with the sample are less than the characteristic times of chemical reactions, the contact time determines the specific rates of heterogeneous processes. The reciprocal influence of heterogeneous and volumetric processes only becomes appreciable when the contact times of the plasma with the sample exceed the characteristic times of chemical reactions. As a result, the specific rates of etching, of oxygen consumption from the gas phase, and of the formation of gaseous products decrease with the increase in the reactor load ratio; however, the correlation of the destruction channels does not change. Compared to the air plasma, oxygen plasma was found to be more stable to the loading effect in a wide range of discharge parameters.     

Catalytic graphitization of polyacrylonitrile (PAN)-based carbon fibers with Fe-Cr2O3 composite coating

The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile(PAN)-based carbon fibers and its catalytic graphitization were studied.Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD,Raman spectroscopy and SEM.The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures.When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300°C,the interlayer spacing(d002) and ratio of relative peak area(AD/AG) reach 3.364-and 0.34,respectively.Whereas,the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800°C and the values of d002 and AD/AG are 3.414  and 0.68,respectively.The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating.The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution  precipitation mechanism.     

The analysis of Armos fibers reinforced poly(phthalazinone ether sulfone ketone) composite surfaces after oxygen plasma treatment

The effects of oxygen plasma treatment on both the fiber surface and interfacial adhesion of Armos fiber reinforced PPESK composites were investigated in this paper. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to analyze fiber surface chemical composition and surface roughness, respectively. The results indicated that oxygen plasma treatment had introduced a large amount of reactive functional groups onto the fiber surface and the fiber surface roughness was increased largely. The interlaminar shear strength (ILSS) of the untreated and oxygen plasma-treated composites was measured to evaluate the interfacial adhesion. The values of ILSS were enhanced dramatically; the water molecule diffusion into composite along interface was prevented effectively. The composite fracture mode was observed by scanning electron microscopy (SEM), which showed that the primary failure mode varied from interface failure to matrix failure after oxygen plasma treatment. Results indicated that oxygen plasma treatment was an effective method to improve the interfacial adhesion properties of Armos fiber reinforced PPESK composites by both chemical bonding and physical effects.     

Morphological evolutions of cast and melt-spun Mg_(97)Zn_1Y_2 alloys during deformation and heat-treating

Mg_(97)Zn_1Y_2 alloy has been studied as an elevated temperature creep resistant Mg-based alloy for nearly ten years.While, the strength of the cast Mg_(97)Zn_1Y_2 alloy with long-period stacking(LPS) structure is lower than that of the commercial AZ91 alloy at room temperature.The microstructure evolutions in Mg_(97)Zn_1Y_2(molar fraction,%) alloys with LPS phase,processed by rolling and annealing the as-cast alloy and rapidly solidifying/melt-spinning and age treating at different temperatures respecti...     

The oxidative intercalation of selected carbon fibers by bis(fluorosulfuryl)peroxide,S2O6F2

Oxidative intercalation of two selected PAN- and pitch-based carbon fibers by bis(fluorosulfuryl)peroxide, S₂O₆F₂, results in materials with enhanced electrical conductivities. The nature and the extent of intercalation show some differences in both systems. Pitch-based fibers can be intercalated up to a composition of C_7·5SO₃F. PAN-based fibers lose some of the lattice nitrogen atoms during intercalation and a lower degree of intercalation is noted. Conductance enhancements up to 14 and 17 times were observed for intercalated tows of pitch- and PAN-based fibers respectively. Specific resistivity measurements on intercalated filaments showed metallic behaviour of these materials up to 300 K. The observed conductance values are discussed, together with the structural data obtained on them.     

Electrografting of poly(carbazole-co-acrylamide) onto several carbon fibers: Electrokinetic and surface properties

Electrografting onto untreated high modulus (HM) and high strength (HS) carbon fibers as well as on electrochemically oxidized HM carbon fibers was carried out under preparative constant current electrolysis conditions by electrocopolymerizing carbazole-acrylamide. The surface morphology of the electrografted carbon fibers was determined by scanning electron microscopy (SEM). In order to obtain at least some information about the relative surface composition of the electrografted fibers energy dispersive X-ray microanalysis (EDX) was applied. For the characterization of chemical composition FTIR reflectance measurements were performed as well. The electrografted copolymer exhibited good thermal stability, which was determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The efficiency of the electrocopolymerization on carbon fiber surfaces under preparative constant current electrolysis conditions was also supported by electrokinetic measurements.     

Morphology of (KC60)n polymeric fibers

The fibers produced by co-evaporation of C₆₀ and potassium, and subsequent treatment in toluene, have been investigated by electron microscopy and optical spectroscopy. The electron diffraction pattern can be indexed in terms of the known orthorhombic (KC₆₀)_n structure. The frequencies of the vibrational modes indicate charge transfer between K and C₆₀, similar to bulk samples; no anisotropy of optical properties has been observed. The detailed analysis of the electron diffraction and micrographs reveal that, contrary to expectations, the direction of polymerization does not coincide with the direction of the long axis of the fibers. Furthermore, the structure is twinned, explaining the absence of optical anisotropy.     

Analysis of kinetic demixing in a mixed oxide (A,B)O in an oxygen potential gradient

It is well known that homogeneous mixed oxides (A,B)O show kinetic demixing of the cations when exposed at high temperatures to an oxygen potential gradient. This paper shows that when the cation distribution can be described by a random mixing model (the random alloy model) the resulting demixing analysis for the composition profiles can be greatly simplified, and made exact, by making use of the random alloy sum-rule. It is also shown that analyses based on an assumed linearity of the vacancy composition profile will predict incorrect demixing composition profiles for the cations.