Graphene has attracted much interest in recent years due to its unique and outstanding properties. Different routes to prepare graphene have been developed and achieved. Preparation methods of graphene used in recent years are intensively introduced, including micromechanical cleavage, chemical vapor deposition, liquid/gas- phase-based exfoliation of graphite, epitaxial growth on an insulator, chemical reduction of exfoliated graphene oxide, etc. And their advantages and shortcomings are further discussed in detail. The preparations of graphene are also prospected.

The progress was made in the area of extending the light absorption of TiO₂ into visible light region by methods of metal cation doping, metalloid anion doping, ion implantation and photosensitization. The particular advantage of metalloid anion doping was that the visible-light-activities can be obtained without the lose of UV-light activities. This article mainly summarized the recent progress in TiO₂ modification by means of metalloid anion doping and the advance in photocatalytic hydrogen production with the photosensitization semiconductor made in our group. In addition, the effect of metalloid anion doped TiO₂ in response to visible light was classified and evaluated. Based on the fact that the construction of inorganic salt-water splitting system without electron donors is a new subject with a view to practical research, the recent advance in the construction of inorganic salt-water splitting system is briefly reviewed while the prospects and existing problems especially for TiO₂ photocatalyst are also addressed.

Gallium phosphide (GaP) nanoparticle was synthesized by the reaction of sodium phosphide and gallium chloride in dimethylbenzene. GaP-supported platinum photocatalysts, Pt(0.80wt%)/GaP and Pt(4.2wt%)/ GaP nanoparticles, were prepared by the simple reduction of chloroplatinic acid (H₂PtCl₆) with hydrazine hydrate (N₂H₄·H₂O). The photocatalytic activities of GaP and Pt/GaP nanoparticles for the decomposition of crystal violet were investigated under visible light irradiation. The results indicate that GaP, Pt(0.80wt%)/GaP and Pt(4.2wt%)/GaP nanoparticles can harness visible light to decompose crystal violet in aqueous solution. The photocatalytic activity of Pt(0.80wt%)/GaP is better than that of GaP while the photocatalytic activity of GaP is better than that of Pt(4.2wt%)/GaP. The Pt coverage has an important effect on the photocatalytic activity of Pt/GaP nanoparticles.

Porous and nanostructured TiO₂ coatings with different Ca, P contents were prepared on titanium by plasma electrolytic oxidation (PEO) in a Ca and P containing electrolyte at different current densities. The surface morphologies and microstructure of the coatings were observed by scanning electron microscope (SEM). Phase compositions of the coatings were characterized using X-ray diffraction (XRD). Simulated body fluid (SBF) immersion tests were conducted to evaluate the apatite forming ability and bioactivity of coatings. The results reveal that the PEO coatings mainly consist of anatase and rutile phases, their surfaces exhibit grains of about 10-100 nm in size and pores less than 10 μm in diameter. The surface grains, coating thicknesses, surface roughness and Ca, P contents of the coatings all increase with the increase of the applied current density during PEO process. The as-prepared PEO coatings with high Ca and P contents could induce apatite formation after immersed in SBF for 14 d, indicating its good bioactivity. However, PEO coatings with low Ca and P contents or heat-treated coatings are bio-inert. The Ca, P contents of the PEO coatings and its crystallization state play key roles in inducing apatite formation in SBF.

Adulterate sodium silicon apatite cement (s-AC) porous scaffolds for bone repair were prepared by using the mixed powders of tetracalcium phosphate and dicalcium phosphate anhydrous, 5wt% sodium silicate water- solution as cement liquid, and NaCl particles as progens. The result shows that the composition of the s-AC scaffolds is sodium silicon apatite. The macroporous sizes of the scaffolds were in the range from 200 μm to 600 μm, the porosity of the scaffolds is from 58% to 75%, and the macropores were interconnected with each other. The compressive strength of the s-AC scaffolds is from 1.6MPa to 3.8MPa, and the degradability of sodium silicon doped s-AC scaffolds improves significantly as compared with AC in Tris-HCl solution. When the s-AC scaffolds are implanted in femur bone defect of rabbits, the histological analysis results show that the new bone tissue is formed on the surfaces and ingrew into the interior of the scaffolds, the well interconnected macropores promoted the bone tissue ingrowth into the scaffolds. In conclusion, the s-AC scaffolds exhibit good biocompatibility, degradability and osteogenesis in vivo, which will be a good biomaterial for bone repair.

ZnO and Zn₂SnO₄ are excellent functional semiconducting materials with wide direct band gap, high electron mobility and photocatalytic activity. High-density single-crystalline ZnO/Zn₂SnO₄ nanocables were successfully synthesized by using a simple thermal co-evaporation from a mixture source of ZnO and SnO₂ powders. The products in general contain various geometries of wires, with an average diameter of 50-100 nm. These nanowires are consisted of ZnO core and Zn₂SnO₄ sheath with ultra-length, up to several hundred microns. The images of transmission electron microscope (TEM) show that the ZnO core of the nanocable grows along the direction of <0001>. The interface between ZnO and Zn₂SnO₄ performs lattice coherent. The photoluminescence (PL) spectra recorded from the nanocables at room temperature show only a strong peak corresponding to UV band emission of ZnO at about 380.58 nm, which indicates that the sheath of Zn₂SnO₄ prohibits the oxygen deficiency in the surface of nanocables. ZnO/Zn₂SnO₄ nanocables can effectively suppress the recombination of the photogenerated electrons and holes, which is promising as anode for dye-sensitized solar cells.

Different types of zinc oxide (ZnO) nanostructures were prepared by electrochemical synthesis on an indium tin oxide (ITO) glass substrate by adjusting the concentration of the electrolyte, deposition time and temperature. X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM) and photoluminescence (PL) spectrum were to determine the characteristics of these ZnO nano structures. The results show that ZnO films is formed quickly at the voltage over a threshold. The ZnO films morphologies are determined by the concentration of the electrolyte. Nanobuds, nanorods, flakes can be obtained in turn with the concentration of Zn(NO₃)₂·6H₂O increasing. Such different morphology formation mechanisms are discussed on the basis of crystal growth theory. The PL spectra of the samples show that the flake ZnO films have a significant widen near edge emission peak with the depressed visible emission, which may have potential applications on optoelectronic devices and sensors.

Al-doped ZnO thin films were prepared by aerosol-assisted chemical vapour deposition (AACVD) on glass substrates. The effect of Al content (2at%-8at%) on the structural, optical and electrical properties of Al-doped ZnO thin films was investigated in detail. The samples were tested by XRD, SEM, EDAX and UV-Vis spectrophotometer. The results indicate that the AZO films have a hexagonal (wurtzite) structure without preferential orientation along c-axis, and however no Al related phases are observed. The average transmittances of the AZO film is over 72% in the visible regions. The optical band gap for the AZO films becomes narrow with the increasing Al dopant. The four-point probe technique is used to characterize thin films electrically. The data shows that Al dopant decrease the sheet resistance. The ZnO films doped with 6at% Al exhibit a minimum of sheet resistance (18Ω/□).

The electrical performance of the stacked glass-ceramic capacitors depends largely on the inner electrode structure and the interface quality. In this work, several metal films, such as Pt, Au, Cu and Ag, were deposited by DC magnetron sputtering serving as inner electrode layers between the dielectric layer and the silver paste electrode of glass-ceramic capacitors. The effect of the deposited metal films on the electrical properties of Na₂O-PbO-Nb₂O₅-SiO₂ glass-ceramic capacitors was investigated. Compared with the single paste electrode structure, Pt and Au metal films could effectively improve the electrical performance of the capacitors, corresponding to an increase of equivalent capacitance by 25% and a decrease of leakage current by an order of magnitude. SEM observations indicate that the Pt, Au and Cu metal films would help the formation of a dense electrode/dielectric interface and inhibit the diffusion of silver, whereas a porous interface and intense silver diffusion are often found in the single screen-printed paste electrode and the deposited Ag metal electrode. The above results reveal that Pt and Au metal films as inner electrodes could make the interface microstructure inhibit the silver diffusion and enhance the overall performance of the glass-ceramic based capacitors.

Effects of heat-treatment temperature on the microstructure and electrochemical properties of coal based needle coke were investigated by TG-DTG, XRD, SEM, XPS analysis and the charge/discharge, cyclic voltammetry curves. The graphitization mechanism of needle coke is suggested as well as the Li⁺ extraction-insertion behaviors. With the heat-treatment temperature increasing, the graphite-like crystal grows continuously attended with a complicated process, including the arrangement of crystal along radial/axial direction, dislocation dispersion among graphite layers, hexagonal carbon formation, crystal edge dispersion and folded graphite layer turning to plane. Meanwhile, the driving-forces are far different for different process. When needle coke is graphitized at 2800℃, it exhibits a lower charge/discharge potential and stable charge/discharge platform, and the insertion capacitance of Li⁺ can maintain at 305mAh/g even after charge/discharged for 40 cycles.

In order to improve the rate performance of lithium iron phosphate, Na⁺ doped LiFePO₄/C cathode materials were prepared by carbothermal reduction technology. Samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transfer infrared spectroscopy (FT-IR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Their electrochemical performances were investigated by galvanostatic charge/discharge in terms of cycling performance and rate capability. The results show that the samples have well regulated olivine type structures without any impurity peaks. Na-doping improves the conductivity and the Li+ diffusion rate of composite materials and decreases the polarization of electrode, and enhances the cycling performance and rate capability effectively. Compared with LiFePO₄/C, Li_0.99Na_0.01FePO₄/C exhibits good electrode properties with discharge capacities of 147.6, 126.4 and 105.1 mAh/g at 0.5C, 2.0C and 5C rates, respectively. In addition, it has excellent cycle stability at different rates and good performance.

The helical carbon nanotubes (HCNTs) was modified with carbon through thermal vapor deposition (TVD) of benzene at 900 ℃, and characterized by X-ray powder diffraction, transmission electronic microscope, scanning electronic microscope and Brunau-Emmertt-Teller method. The specific surface area of the HCNTs decreased after carbon coating. The obtained carbon coated HCNTs used as anode materials of Li-ion battery were studied. The results revealed that appropriate amount of carbon coating could improve the first columbic efficiency, the cycling stability and rate charge/discharge performance of the HCNTs. After 45 min carbon coating, HCNTs gained a weight increase approximately 220wt%, with its first columbic efficiency increasing from 59.2% to 77.8%, and delivered a discharge capacity of 265.6, 245.7, 196.0, 163.2 mAh/g at the rates of 1.0C, 2.0C, 5.0C and 10.0C, respectively. After 95 cycles at 10.0C, its discharge capacity retention was 93.3%. Although excessive carbon coating could further improve the first coulumbic efficiency and cycling stability of HCNTs, it also degraded the rate capability.

Paper-based friction materials containing four different graphite particle sizes were prepared using the wet paper-making process. The effects of graphite particle size on friction performance such as friction torque curves, dynamic friction coefficient, static friction coefficient and wear rate were studied by using an inertia friction tester. Meanwhile, the sensitivity of friction coefficient to braking pressure and rotating speed was also investigated. Worn surfaces of samples were analyzed by using scanning electron microscope. The results show that with graphite particle size decreasing, braking time increases and torque curves become more stable, while friction coefficient and wear rate decrease. The dynamic friction coefficient declines as braking pressure and rotating speed increase. Samples with proper particle size exhibit more stable friction coefficient in the continuous braking process. Lubricating film is formed to lower wear rate in the worn surface as the graphite particles size decreases.

The tribological properties of Sb₂S₃ nano-bundles as an additive in liquid paraffin were evaluated on a four-ball tester, thereafter the performance of Sb₂S₃ nano-bundles was compared with that of Sb₂S₃ nano-particles. The comparative analyses of friction coefficients, wear scar diameters and morphology of worn surfaces show that Sb₂S₃ nano-bundles and nano-particles can both improve tribological properties of base oil, Sb₂S₃ nano-bundles exhibit better friction reduction and anti-wear properties than Sb₂S₃ nano-particles at relative low load, and they possess very similar tribological performance at relative high load. As far as the load carrying ability is concerned, the performance of nano-particles is obviously better than nano-bundles. It is inferred that the sliding-rolling friction transition emerges when lubricated with nano-bundles/oil mixture at low load, which contributes to the good lubricating effect of the nano-bundles.

Pb(Fe_2/3W_1/3)O₃ was modified by doping Pb(Mg_1/2W_1/2)O₃ with Sol-Gel method using inorganic salts as precursors. At calcination temperature of 700℃, the resulted solid solution (1-x)Pb(Fe_2/3W_1/3)O₃-xPb(Mg_1/2W_1/2)O₃ kept a perovskite structure in the whole doping range of 0≤x≤1. The obtained Pb(Mg_1/2W_1/2)O₃ (x=1) is fully ordered with a unit cell as two times as that of Pb(Fe_2/3W_1/3)O₃ (x=0). Solid solution (1-x)Pb(Fe_2/3W_1/3)O₃- xPb(Mg_1/2W_1/2)O₃ (0<x<1.0) also has an ordered crystal structure showing supperlattice peaks of 1/2 (111) and 1/2 (311) in X-ray diffraction, whose intensities become stronger as x increases. Combining electron diffraction and elemental analysis in transmission electron microscope, solid solution (1-x)Pb(Fe_2/3W_1/3)O₃-xPb(Mg_1/2W_1/2)O₃ is verified as a single phase with perovskite structure, rather than a mixture of two phases. The particles of solid solution have a cubic morphology, and their grain size first decreases and then increases when doping coefficient x varies from 0.2 to 0.8. Due to the substitution of larger Mg²⁺ for smaller Fe³⁺ ions, its lattice constant increases linearly with the enhancement of x. According to the measured M-H curves, the magnetic performance of the solid solution decays as the doping coefficient x increases, because the formation of diamagnetic Pb(Mg_1/2W_1/2)O₃ could destroy the -Fe³⁺-W-O-W-Fe³⁺- and -Fe³⁺-O-Fe³⁺- magnetic bonds in antiferromagnetic Pb(Fe_2/3W_1/3)O₃ phase.

(Ba_1-xCa_x)(Ti_0.82Zr_0.18)O₃(BCZT, 0≤x≤0.26) ceramics was prepared by a solid phase reaction. The effect of Ca²⁺ doping on the microstructure and dielectric properties of the ceramics was studied. Results showed that the solid solubility lay around x=0.16 for BCZT ceramics while the second phase was observed. The value of c/a changed as the U-type curve with the variation of the Ca²⁺, and the minimum of the c/a was 1.00276 at x=0.06. It was found that Ca²⁺ ion substitution can be almost incorporated into the A site by the calculation of the tolerance factor and lattice constant. With increasing Ca²⁺ ion content, the grain size was decreased. The Curie temperature was shifted to low temperature, and the εr-T peak was decreased and broaden. The relaxor characteristics were obtained while Ca²⁺ ion content was further increased.

A newly developed rapid densify technique, spark plasma sintering (SPS), is used to prepare full-densified aluminum nitride (AlN) ceramics which are poorly sinterable. Some sintering aids are also used to promote the AlN ceramics’ densification and improve its thermal conductivity. In this work, effects of sintering aid Li₂O on densification, microstructure and thermal property of SPS sintered AlN ceramics were investigated. Results suggest that the initial sintering temperature of AlN samples reduce from 1550℃ to lower than 1200℃ with 1.0wt% Li₂O and 1.5wt% Sm₂O₃ (or Y₂O₃) adding as sintering aids . With Li₂O addition, AlN compacts can be fully densified at 1650℃. The microstructure of AlN compacts indicates that Li₂O is beneficial to generate aluminate liquid phase with better wettability and promote the densification of AlN ceramics, but it is unable to obtain higher relative density of AlN compacts because the escapement of gas phase though out liquid phase is very difficult in a rapid sintering process. Meanwhile, Li₂O addition affects the growth of AlN grains, and the better wettability of aluminate with AlN grain induces the homogeneous distribution of grain boundary phase. The deterioration of thermal conductivity of AlN ceramics is caused by the fact that the scattering of phonon is enhanced by small grain size and the secondary phase spreading adequately along the AlN grain boundaries. The thermal conductivity of AlN samples with 1.0wt% Li₂O and 1.5wt%Sm₂O₃ as sintering aids is lower than that of sample only with Sm₂O₃ as sintering aids.

The microwave dielectric properties of the (1-x)(Mg_0.9Co_0.1)TiO₃-x(Ca_0.61La_0.26)TiO₃(MCT-CLT) ceramics were investigated. The system was prepared using a conventional solid-state ceramic route. The objective of the present work is to compensate for the negative temperature coefficient of resonant frequency (τ_f) of (Mg_0.9Co_0.1)TiO₃ (MCT) by the addition of (Ca_0.61La_0.26)TiO₃ (CLT). The microwave dielectric properties are strongly correlated with the sintering temperature and the composition. Very dense MCT-CLT ceramics were prepared by sintering at 1300℃. When the ceramics were sintered at temperatures above 1300℃, the bulk density decreased and the dielectric properties deteriorated. With the increasing of x, the relative dielectric constant (ε_r) of the ceramics increases and the product of quality factor and resonant frequency (Q×f) decreases. For practical application, 0.87(Mg_0.9Co_0.1)TiO₃- 0.13(Ca_0.61La_0.26)TiO₃ (87MCT-13CLT) ceramics sintered at 1300℃ with a dielectric constant ε_r=22.4, a Q×f value of 35000 GHz and a temperature coefficient of resonance frequency (τ_f) of -8.7×10^-6/℃ was proposed in this paper.

ZrB₂ was first introduced into carbon preforms through ultrasonic and vacuum immersion-carbonthermal reduction method. After densification using thermal gradient chemical vapor in-ltration and graphitization, ZrB₂ doped C/C composites were prepared. The oxyacetylene ablation results show that the linear and mass ablation rates of the composites after doping with 6.87wt% ZrB₂ decreased by 64.9% and 67.5%, respectively. The ablation of C/C composites is mainly controlled by thermochemical and thermophysical reactions and mechanical denudation does not play a dominant role. The evaporation of ZrO₂/B₂O₃ during ablation would take away large amounts of heat, reducing the thermal impact of flame to the ablation surface.