bluuebunny/crossref_metadata_2025 huggingface dataset:
Microwave Dielectric Properties of RENbO4 (RE=Y, Yb,Ce) Ceramics
Authors: Zhang Zhi Li , Xu Chun , Liu Qiu Ping
Published: March 2010

In the search of more microwave dielectric materials with high-quality factor (Qf ) and high relative dielectric constant (r), RENbO4 (where RE = Y, Ce, Yb) niobate ceramics were synthesized from a solid-state ceramic route, their sintering behavior and microwave dielectric properties were investigated. All of the RENbO4 ceramics formed a single-phase fergusonite-type structure (monoclinic, with space group I2/c), except CeNbO4. They all have an excellent quality factor and dielectric constant value in range of 20 – 28, and the inherent reasons were analyzed.
Preparation of ZnNb2O6 Nano-Powders by Pechini Method
Authors: Zhang Ying Chun , Wang Shu Ming , Zhou Xiang Na , Fu Bao Jian , Yue Zhen Xing
Published: March 2010

ZnNb2O6 ceramics with a columbite crystal structure, is a promising candidate for application in microwave devices. In this study, ZnNb2O6 nano-powders were prepared using Nb2O5 and Zn(NO3)2 as raw materials by Pechini method. The microstructure and crystal structure of ZnNb2O6 powders were investigated systematically using X-ray powder diffraction and SEM techniques. The effect of amount of citric and ethylene on the formation of sol-gel and the particle size of ZnNb2O6 powders were also investigated using orthogonal design. Finally, the optimum process parameters for synthesis ZnNb2O6 nano-powders were obtained in this study.
Preparation and Microwave-Absorption Property of SiO2-SiC-Based Composites
Authors: Guan Li , Fan Bing Bing , Li Ming Liang , Wen He Jing , Li Kai , Wang Hai Long , Chen De Liang , Zhang Rui
Published: March 2010

SiO2-SiC composite particles were prepared using a sol-gel process. BaTiO3 powders were synthesize through solid-state reaction. They were mixed as microwave absorbents with Fe3O4 powders to obtain the complex absorption. Epoxide resin (EP) was used as matrix and solidified with the mixtures. The techniques of DSC-TG, XRD were used to characterize the composite particles and the obtained compacts. A vector network analyzer was used to measure the reflectivity of the SiO2-SiC-based composites. The effects of the aborbents’ contents on the reflection of the microwave absorption materials were disscussed. It was found that SiO2-SiC composites could be prepared using sol-gel process and BaTiO3 powders could be synthesize through solid-state reaction. The results indicated that SiO2-SiC composite is contribute to absorb microwave, where SiO2-SiC: BaTiO3: Fe3O4 = 6:2:2 (vol %), the frequency region in which the maximum reflectivity is more than -10 dB is 5.4-7.6 GHz.
Microstructures and Microwave Properties of CaTiO3 Doped (ZnMg)TiO3 Dielectrics with CaO-B2O3-SiO2 Addition
Authors: Li Bo , Zhou Xiao Hua , Zhang Shu Ren , Xiang Long Cheng
Published: March 2010

The microwave properties and microstructures of (ZnMg)TiO3-based dielectric prepared by conventional solid-state method were investigated as functions of CaTiO3 and CaO-B2O3-SiO2 additions. The effects of CaTiO3 on the crystal phase and the evolution of microstructure of (Zn0.65Mg0.35)TiO3 were studied. The result indicated that CaTiO3 secondary phase coexists with (ZnMg)TiO3 main phase in the ZMT-CT ceramics, which confirmed by EDS analysis. Because of CaTiO3 with large τf value (τf = 800 ppm/°C), the temperature coefficient of resonant frequency (τf) of ZMT-CT with biphasic structure was adjusted to near zero value. The microwave properties of (Zn0.65Mg0.35)TiO3 ceramics doped with 5wt% CaTiO3 sintered at 1150°C were ε ≈ 24, τf ≈ ±10 ppm/°C, Q×f > 45,000 GHz. Further, it was found that the CaO-B2O3-SiO2 additive could successfully reduce the sintering temperature of (Zn0.65Mg0.35)TiO3–CaTiO3 ceramics from 1150 to 950°C, and significantly improve the densification of this system, which were densified below 1000°C. This was due to the formation of liquid phases during the sintering observed by SEM. The (Zn0.65Mg0.35)TiO3–0.05CaTiO3 dielectrics with 1 wt% CaO-B2O3-SiO2 sintered at 950~1000°C exhibited the optimum microwave properties: ε ≈ 22, Q×f ≈ 20,000 GHz and τf ≈ ±10 ppm/°C.
Fabrication of Barium Titanate Inverse Opals by Sol-Gel Electrophoretic Deposition Process
Authors: Li Bo , Wang Jin Qing , Fujiwara Rei , Kuwabara Makoto , Fu Ming , Zhou Ji
Published: March 2010

Barium titanate (BTO) inverse opal photonic crystals were fabricated by a process of self-assembly of polystyrene opal template in combination with electrophoretic deposition (EPD) of nanoparticles from BTO suspension. In this process, stable monodispersed suspension of BTO nanoparticles was prepared by dispersing BTO gel into a mixed solvent of 2-methoxyethanol and acethylacetone. Then the BTO nanoparticles were infilled into the interstices of the opal template formed by monodisperse polystyrene microspheres by electrophoretic deposition, and then polystyrene template was removed by calcining the specimen at a final temperature of 500oC. SEM images show that the inverse opals possess face-centered cubic (fcc) structure with center to center distant of the air spheres 310 nm. A photonic bandgap in the visible range is observed from reflection spectra of the sample. Such BTO inverse opals as photonic crystals should be useful in device applications.
Dielectric Properties of CaCu3Ti4O12 Ceramics
Authors: You Jing Han , Gong Xiao Yang , Li Tong Wei , Chen Qing Dong , Li Li Ben
Published: March 2010

CaCu3Ti4O12 ceramics were prepared by the traditional solid-state reaction method and the dielectric properties were investigated, the activation energy and relaxation time factor of the samples were calculated. Debye relaxation theory was attempted to analyze the experimental datum, the static and high-frequency dielectric constants were obtained according to Cole-Cole spectra. The temperature dependence of the dielectric constant of CaCu3Ti4O12 were fitted by computer and the theoretical results nearly agree with experimental results.
Sol-Gel Process for the Synthesis of Single-Phased BaTi2O5 Powder
Authors: Li Guo Jun , Zhang Qi , Ren Rui Ming , Lü Hao
Published: March 2010

The single-phased BaTi2O5 (BT2) powders were synthesized by a sol-gel method by using barium acetate and tetrabutyl titanate as starting materials and ZrO2 as stabilizing agent. A samll amout of ZrO2 is effective to prepare BT2 in a single phase and the second phase of BaTiO3 (BT) and Ba6Ti17O40 (B6T17) increases with increasing ZrO2 content. BT2 starts to form at about 700 oC and BT2 in a single phase is obtained at 800 to 1250 oC in air at 0.5 mol% ZrO2. The synthesized grains at 900 oC are nearly spherical in shape and whose sizes are 0.2-0.5 m.
Develop Single-Phase High Dielectric Constant SiO2-Based Composite Gate Dielectric
Authors: Chan Chao Chin , Wei Yin Fang , Diao Chien Chen , Hsieh Yuan Tai , Cheng Ping Shou
Published: March 2010

In this study, we hoped to find the single-phase high dielectric FET gate-used ceramic materials, which will be used in the sputtering method and have the dielectric constants higher than those of SiO2 and Si3N4. TiO2, La2O3 and ZrO2 are mixed with SiO2 to format the (1-x) TiO2-x SiO2, (1-x) ZrO2-x SiO2 and (1-x) La2O3-x SiO2 compositions, where x is dependent on the different raw materials. The all compositions are calcined at 1100oC and sintered at 1400oC~ 1550oC for 2hrs, and the X-ray patterns are used to find the crystal phases of all sintered ceramics. Because of the existence of single-phase, the sintering and dielectric characteristics of 0.3 La2O3-0.7 SiO2 ceramic are further developed.
Dielectric Properties of BiFeO3 Ceramics with Equal and Unequal Substitutions of Ti for Fe
Authors: Gu Yan Hong , Chen Wan Ping , Ding Ming Jian , Qi Jian Quan
Published: March 2010

BiFeO3, BiFe0.9Ti0.1O3 and BiFe0.9Ti0.05O3 ceramics were prepared by solid state reactions and were compared in electrical and dielectric properties. The resistivity of BiFe0.9Ti0.05O3 was 1.3×1012 Ω cm, which was about two and a half orders of magnitude higher than that of BiFeO3. and three times higher than that of BiFe0.9Ti0.1O3. The dielectric loss of BiFe0.9Ti0.05O3 was 0.1 and 0.02 at 100Hz and 1MHz, respectively. These phenomena can be explained base on the decrease of oxygen vacancies VO•• and defect complexes between the ferrum vacancies VFe and oxygen vacancies VO•• in the ceramics.
Extrinsic Scaling Effects on the Dielectric Response of Grained BaTiO3 Films
Authors: Li Li Ben , Su Li Qiu , Zhen Zhi Qiang , Li Xin Zhong , Chen Qing Dong , Li Tong Wei
Published: March 2010

A set of gradient stresses is used in Landau thermodynamic theory to explain the dielectric diffusion of BaTiO3 films grown on thick copper foils. Every grain in the films is treated as a single domain core that is surrounded by boundaries with low dielectric constant. The dielectric diffusion is mainly induced by the diffusive phase transition caused by the gradient stresses. The low dielectric constant boundaries suppress the peak value of the dielectric constant. The results agree with the experiments.
Low Sintering of the Temperature-Stable Dielectric Ceramics Based on Barium Titanate in Reducing Atmosphere
Authors: Sun Chang Ku , Wang Xiao Hui , Li Long Tu , Song Tae Ho
Published: March 2010

The optimized composition and sintering process of the low sintering X7R-type temperature-stable dielectric ceramics based on Barium Titanate in reducing atmosphere have been investigated. Flux aids SiO2-B2O3-Li2O were used in the experiments. The influence of composition and the content of flux agent on the microstructures and properties of ceramics materials were systemically studied. The X7R-type dielectric ceramics materials could be sintered at low temperature of 950oC in H2/N2 atmosphere, by optimizing flux content and adjusting process parameters. The dielectric constant of ceramics was effectively improved using two-step sintering process.
Low Temperature Sintering of Ferro-Materials with Both Capacitance and Inductance Properties
Authors: Qi Xi Wei , Han Wei Qi , Wang-Yang Pei Hua , Wang Hai Feng
Published: March 2010

Ferro-materials which possess both capacitance and inductance were sintered at low temperature using Bi2O3 as sintering additives. The composition of ferro-materials is 0.4PMZNT- 0.6NiCuZn. PMZNT relaxor ferroelectric is a solid solution that consists of Pb(Mg1/3Nb2/3)O3, Pb(Zn1/3Nb2/3)O3 and PbTiO3. NiCuZn ferrite with general formula is Ni0.2Cu0.2Zn0.6Fe2O4. Effects of the content of Bi2O3 and sintering temperature on the relative density of prepared ferro-materials have been studied. Dense ferro-materials were obtained at as low as 890°C with 2.0 wt% of Bi2O3. The X-ray diffractometer (XRD) identifications showed that ferro-materials consisted of distinct ferroelectric and ferromagnetic phases. Scanning electron microscopy (SEM) observations revealed that low temperature sintered ferro-materials possess high density and fine-grained microstructures. Prepared ferro-materials exhibit electromagnetic properties.
Dielectric and Sintering Properties of the Doping CaO-B2O3-SiO2 System Low Temperature Co-Fired Ceramics
Authors: He Ming , Zhang Shu Ren , Zhou Xiao Hua , Hu Jian Geng , Zhang Ting , Li Bo
Published: March 2010

. A doping CaO-B2O3-SiO2 system low temperature co-fired ceramics (LTCC) was prepared with a mixture of high temperature melting glass and sol-gel glass for different ratio. The effects of sol-gel glass content on the microstructure, crystalline phases, sintering properties and dielectric properties of CaO-B2O3-SiO2 system were investigated at 850°C. The results show that the samples with sol-gel glass doping had little change in phase composition, but contained more calcium silicates, and less calcium borate. As the amount of sol-gel glass increased, the shrinkage improved, the sintered density slightly decreased, the dielectric constant (εr) reduced, and the dielectric loss (tgδ) decreased. When the amount of sol-gel glass was 14.5wt%, εr and tgδ of the doping sample were 5.80, 4.6×10-5 (at 1 MHz), respectively. Moreover, the doping system had a good matching ability with gold slurry and Au-Pt-Pd slurry.
Control of the Shrinkage during Hybrid Microwave Sintering of Nano-Sized ZnO Based Powder for Varistors
Authors: Marinel Sylvain , Savary Etienne , Pautrat Alain , Retoux Richard
Published: March 2010

The microwave heating allows sintering in a very short time which is useful to keep the materials nanostructure. Up to now the trial error method is commonly used to find the best experimental parameters. This method is time consuming and does not allow getting a high reliability. In this work, a specific optical based position sensing device has been used to record the shrinkage during hybrid microwave sintering. Owing to this particular device, the control of the nano-sized ZnO based powder sintering has been successfully achieved. Very fine microstructures were obtained and electrical properties of those nano-ceramics were determined.
Admittance Spectroscopy of Y2O3-Doped ZnO Varistors Sintered at Different Temperature
Authors: Liu Jun , He Jin Liang , Hu Jun , Long Wang Chen , Luo Feng Chao
Published: March 2010

ZnO varistors are multicomponent polycrystalline ceramics with highly nonlinear current-voltage characteristics and surge energy absorption capabilities. The voltage gradient of the ZnO varistor is inversely proportional to its average grain size. Recently, the rare-earth oxides have been reported as growth inhibitor of ZnO grains to obtain high voltage gradient. Although the dopant of rare-earth oxides can remarkably enhance the voltage gradients of varistor samples, their leakage currents and nonlinear coefficients deteriorate at the same time. In this paper, the sintering effects on electrical characteristics and admittance spectroscopies of ZnO varistor samples doped with yttrium oxides were investigated. Samples were fabricated under different sintering temperatures, including 1000 °C, 1100 °C, 1200 °C and 1300 °C. Then, the electrical characteristics and admittance spectroscopies of these varistor samples were measured. The measured current-voltage results behave special U-type curves related to sintering temperature. Furthermore, the admittance spectroscopy of these samples revealed the sintering effects on the intrinsic defects of ZnO varistors.
Effects of pH Value on the Structures and Optical Properties of Bi2S3 Thin Films
Authors: Huang Jian Feng , Wang Yan , Cao Li Yun , Zhu Hui , Zeng Xie Rong
Published: March 2010

Bismuth sulfide (Bi2S3) is an important semiconductor material, which has wide applications in thermoelectricity, electronics, photoelectricity and infrared spectroscopy. Bi2S3 thin films have been deposited on ITO substrates through a cathodic electrodeposition approach at room temperature. The as-deposited thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence spectrum (PL). The effects of solution pH values on the structures and optical properties of the thin films were particularly investigated. Results show that uniform Bi2S3 thin films with oriented growth along (240) direction can be obtained at the solution pH value range from 4.5 to 6.5. The as-prepared thin films exhibit stable blue-green photoluminescence properties under the ultraviolet light excitation at room temperature. With the increase of the solution pH values, the crystallization of the Bi2S3 thin films improves while the grain size of the obtained thin films decreases and the light emission intensity of the thin films decreases.
Effect of Bi2O3 Addition on the Electrical and Physical Properties of Lead-Free 0.98(Na0.5K0.5)NbO3-0.02 Ba(Zr0.04Ti0.96)O3 Piezoelectric Ceramics
Authors: Wang Chun Huy
Published: March 2010

The 0.98(Na0.5K0.5)NbO3–0.02Ba(Zr0.04Ti0.96)O3 ceramics have been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the Ba(Zr0.04Ti0.96)O3 diffuses into the lattice of (Na0.5K0.5)NbO3 to form a solid solution, in which a orthorhombic phase with a perovskite structure was found In order to improve the sinterability of the ceramics, Bi2O3 additions were used as a sintering aid. The electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.3 and 0.55, respectively, at the sintering of 1100oC for 5 h. For 0.98NKN-0.02BZT ceramics by doping 0.5 wt.% Bi2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.21 and 0.57, respectively. The ratio of thickness coupling coefficient to planar coupling coefficient is 2.7.
Influence of Processing Factors on the Phases and Morphologies of ZnS Optical Thin Films
Authors: Wang Yan , Huang Jian Feng , Cao Li Yun , Zhu Hui , Zeng Xie Rong
Published: March 2010

ZnS is one of the most important semiconductors with wide direct band-gap (3.68 eV) and it is widely used as electroluminescence, flat panel display and cathode ray luminous materials. Uniform ZnS optical thin films were deposited on Si (111) substrates by a vacuum evaporation method. The influences of evaporation temperature, deposition time and the distances between substrates and evaporation sources on the phases and morphologies of the ZnS thin films were investigated. The as-prepared thin films were characterized by X-ray diffraction and atomic force microscopy. Results show that the as-prepared thin films are composed of sphalerite ZnS with a little wurtzite phase. The obtained thin films exhibit an oriented epitaxial growth along (111) direction. The evaporation temperature has a great effect on the phases and morphologies of ZnS thin films. Uniform ZnS thin films can be achieved at the evaporation temperature of 1200°C for 30 min. The crystallization of ZnS thin films improves with the increase of evaporation time.
Reversible Surface Wettability Conversion of ZnO Film
Authors: Liu Hong Qin , Lu Shi Xiang , Xu Wen Guo , Pan Wei
Published: March 2010

The ZnO films were fabricated by chemical oxidation of metallic Zn in a 5% N, N-dimethyl- formamide (DMF) aqueous solution at 95°C for 24h. After modified with octadecyltrichlorosilane (OTS), a superhydrophobic ZnO film was obtained. The superhydrophobic film turned into a superhydrophilic one after UV irradiation, which can be recovered through being placed in the dark.
Preparation and Dielectric Properties of Oriented PZT Thin Films by LB Technique
Authors: Tang Dong Yan , Zhang Xiao Hong , Qiao Ying Jie , Li Y.
Published: March 2010

The oriented La modified PZT thin films were prepared on Pt/Ti/SiO2/Si substrate by the LB technique. The pre-sintering temperatures and the annealing temperatures for La modified PZT were determined by TG-DTA curves and XRD detect results. XRD detection of PZT and PZT with different La amount illustrated the crystal constructions and the effects by modification. The AFM observation of PLZT thin films with organic acid indicated that the LB technique could obtain smooth and flat film with the deposition of PLZT particles within nanometers on substrate. The detection results of the electrical properties indicated that the modification of La had great influence on the electric properties of LB thin film. PLZT thin film by annealing at 650°C had better dielectric constant of 569.2 and dielectric loss of 0.4915 at 5 kHz. And the amount of La of 2% in mass gave the piezoelectric constant of 14pC/N.
Enhanced Brightness and Efficiency in Single-Layer White Polymer Light-Emitting Diodes (PLEDs)
Authors: Chou Dei Wei , Chen Kan Lin , Huang Chien Jung , Chen Chern Hwa , Chen Wen Ray , Meen Teen Hang , Shiau Ke Shiang
Published: March 2010

In this paper, the improvements in luminance and efficiency have been demonstrated in a white polymer light-emitting device (PLED) with the structure of ITO/ poly (N-vinylcarbazole) (PVK): 1,1,4,4- tetraphenyl-1,3-butadiene (TPB):5,6,11,12-tetrapheny lanpthacene (rubrene) /LiF(1 nm)/Ca(10 nm)/Al(100 nm). The luminance of the white PLED is up to 4940 cd/m2 at 17 V. The current efficiency and Commission Internationale d’Eclairage (CIE) coordinates is 1.66 cd/A and (0.325, 0.326), respectively. The enhancement of the luminance and efficiency can be attributed to an improved hole-injection ability and balance carrier recombination through two ways: (1) enhancing the hole-injection from ITO by using O2 plasma treatment, and (2) balance the recombination of hole and electron by produce a buffer layer with σ-bonded segments of polymer between the ITO and the polymer layer. Besides, orange-emitting rubrene provides that direct recombination of holes and electrons occurred on the dopant molecules and trapping significantly enhanced the luminance and efficiency.
Synthesis of the Gold Nanocubes by Electrochemical Method with Surfactant Solution and Acetone Solvent Addition
Authors: Chen Kan Lin , Huang Chien Jung , Chiu Pin Hsiang , Wang Yeong Her
Published: March 2010

Monodispersed gold nanocubes of highly uniform size were fabricated by a simple electrochemical method. The lengths of the edges of the gold nanocubes were about 30 nm. The growth solution was prepared from two cationic surfactant solutions as micelle templates with added acetone solvent. The primary surfactant was hexadecyltrimethylammonium bromide (CTAB) and the co-surfactant was tetradodecylammonium bromide (TTAB).
Preparation of La1-xCexNiO3 (x= 0 ~ 0.4) Perovskite-Type Oxide by Sol-Gel Using Polyvinyl Alcohol
Authors: Soongprasit Kanit , Aht-Ong Duangdao , Sricharoenchaikul Viboon , Atong Duangduen
Published: March 2010

Perovskite-type oxides catalyst are of interest for various application such as auto-thermal reforming (ART), catalytic wet air oxidation (CWOA) and piezoelectric (PZT). In this paper, La1-xCexNiO3 (x= 0-0.4) perovskite-type oxides have been prepared b sol-gel process using PVA. The precursor was mixed metal ion and PVA with a mole ratio of 1:1 and 1:2. The decomposition during the calcinations process was evaluated by thermogravimetric analysis and differential thermal analysis. Phase of synthesized materials were characterized with X-ray diffraction. Morphological analysis and elemental composition of catalysts was determined by Scanning electron microscope and energy dispersion spectroscopy. The characterization results show that highly crystalline and homogeneous phase of these perovskite oxides were successfully synthesized by the sol-gel method via PVA as a complexing agent.
Zinc-Doped TiO2 Nanotube Arrays
Authors: Yang Yang , Wang Xiao Hui , Li Long Tu
Published: March 2010

Zinc-doped TiO2 nanotube arrays were fabricated by immersing TiO2 nanotube arrays in zinc-containing solution for hours. And subsequent heat-treatment was crucial for Zn2+ coming into the crystal lattice of TiO2 nanotubes. TEM analysis was used as main technique to investigate the structure of zinc-doped TiO2 nanotubes, and found that the Zn2+ ions only combine into the lattice of TiO2 nanotubes. This kind of doping can change the valence structure in the surface of TiO2 nanotube array. The obtained zinc-doped TiO2 nanotube arrays have potential application in photocatalysis.
Preparation and Characterization of Unique Foamy Zirconia Single Crystals via Sol-Gel-Hydrothermal Method
Authors: Chang Qi Bing , Zhou Jian Er , Wang Yong Qing , Meng Guang Yao
Published: March 2010

Porous ZrO2 single crystals were prepared through a sol-gel-hydrothermal method and characterized by XRD, HR-TEM, SEM and FT-IR. The results show that the dried sol gel was converted into monoclinic zirconia crystals after calcined above 550 °C. The zirconia single crystal has a porous structure with the crystal sizes of 20-70 nm. The origin of the pores was the gaseous hydrolysates of the superstoichiometric urotropine. The gel structure and the hydrothermal treatment are the required conditions resulting in the pores in crystals. After sintered at 1400 °C, the disc of the obtained ZrO2 crystals was dense. However, Y2O3 should be added to avoid fracture due to phase change if the disc was used as heat insulating layer.
Improving Ag-DLC Film Adherence on High-Speed Steel by Varying Ag Contents in A Mid-Frequency Dual-Magnetron Sputtering
Authors: Yu Xiang , Wang Cheng Biao , Peng Zhi Jian
Published: March 2010

Aiming at improving their tribological behaviors, adhesion of diamond-like carbon (DLC) films on high-speed steel was investigated by varying doping silver (Ag) contents in a mid-frequency dual-magnetron sputtering system. Scratch testing was performed on the Ag-DLC films under a progressive normal load from 3 to 80 N, along with a Rockwell C indenter at a relative displacement speed for a Rockwell testing. A microscopic analysis of the scratch evolution under a progressive normal load permits identification of the various traces and the damage mechanisms of the films. A process of the film adhesion failure typically in turn appears like this, germination of the cracks along the longitudinal edges of the scratch traces; propagation in front of the indenter; and, detachment in the subsurface by shearing. An Ag-DLC film of 15.2 at% Ag exhibits a superior adherence on the steel substrate as compared with the three Ag DLC films of the other doping silver contents.
Preparation and Oxidation Resistance of the Borate Glass Coating on Graphite Anode
Authors: Yu Xiao Hua , Zeng Gui Sheng , Xie Gang , Li Rong Xing
Published: March 2010

The protection coating, which was used on graphite anode, was developed. The materials were SiO2, B2O3 and soluble glass as binder. The micrographic pattern, the phase composition and the components of borate glass coating were analyzed. The results indicated that the coating was morphology of borate glass at 700~850°C, the components were SiO2, and B2O3 from XRD analysis, the coating could permeate into the pores of the graphite anode and seal the cracks developed by the coating, and it was adhesive strongly to the graphite anode from SEM analysis. The effects of the temperature and time on oxidation weight loss ratio and oxidation rate of graphite anode coating were observed and analyzed. The mechanism of oxidation resistance of the coating layer was explained. In addition, the thermal cycle experiments with the borate glass coating were done at 800°C and 850°C, and the results demonstrated the sample had good ability of resistance to thermal shock.
W-Doped DLC Films by IBD and MS
Authors: Fu Zhi Qiang , Wang Cheng Biao , Wang Wei , Peng Zhi Jian , Yu Xiang , Lin Song Sheng , Dai Ming Jiang
Published: March 2010

W-doped DLC films were synthesized from ethyne and tungsten by ion beam deposition and magnetron sputtering, and the influence of W target current on the structures and the properties of W-doped DLC films were studied. There exist some defects smaller than 3micron in W-doped DLC films and the influence of W target current on the defects is unobvious. The W content in the films is tardily increased with W target current below 3.5A, and then acutely rises with W target current. When target current is below 3.5A, the ratio of sp3-C to sp2-C is first decreased and then increased with the rise of target current, and the ratio of WC-C to sp2-C is close to 0; but when the target is above 3.5A, the ratio of sp3-C to sp2-C is decreased and the ratio of WC-C to sp2-C is augmented with further increasing target current. The hardness and the modulus is first decreased with target current and the minimum value is reached for the W-doped DLC films deposited with a target current of 2.6A. The W-doped DLC films deposited with a target current of 2.6A exhibit the best film-substrate adhesion. The W-doped DLC films deposited with a low target current exhibit a friction coefficient while the wear resistance of the W-doped DLC films deposited with a medium target current of 2.6A is best.
Property and Microstructure of CNTs/AlN Ceramics
Authors: Wang Hong Lei , Zhou Xin Gui , Yu Hai Jiao , Zhao Shuang , Luo Zheng
Published: March 2010

CNTs/AlN ceramics were fabricated by hot-pressing and their bulk density, flexural strength, thermal conductivity were characterized. The microstructure was also investigated. The fracture surface were analyzed by SEM. TEM was used for analyzing the microstructure. It is found that the density, mechanic and thermal-conductivity properties markedly decreased as the CNTs reinforced AlN ceramic; through microstructure observation, the conglomeration of CNTs mostly exist among the AlN grain boundary, and the CNTs were scathed by the high temperature and pressure of the hot-pressing.
Titanium Nitride Coatings on Ti Alloys by PIRAC for Orthopedic Implants
Authors: Wu Shou Jun , Gutmanas Elazar Y. , Gotman I.
Published: March 2010

In the present work, Ti and Ti-6Al-4V were PIRAC nitrided at the relatively low temperatures of 700-850°C. To obtain thicker TiN layers, 3 stage PIRAC based coating was applied: (1) PIRAC nitriding followed by (2) PIRAC titanizing followed by (3) additional PIRAC nitriding. The microstructure and phase composition of the obtained surface layers were characterized employing X-ray diffraction and scanning electron microscopy with chemical analysis (SEM/EDS). Bending test was employed to evaluate the coatings adhesion to the substrate. Lower PIRAC nitriding temperatures yielded smoother TiN coatings with a more gradual microhardness decrease from the surface to the bulk. All PIRAC TiN based coatings have excellent adhesion to substrate – no delamination of the coating in bending tests was observed. The best combination of microhardness and adhesion was obtained using 3 stage PIRAC process.
Deposition Kinetics of the Cristobalite Aluminum Phosphate Coating on SiC Coated Carbon/Carbon Composites Prepared by Hydrothermal Electrophoretic Technique
Authors: Yang Wen Dong , Huang Jian Feng , Cao Li Yun , Zeng Xie Rong
Published: March 2010

Cristobalite aluminum phosphate (C-AlPO4) coatings were prepared by hydrothermal electrophoretic process on SiC coated C/C composites at different temperatures. The as-prepared C-AlPO4 coatings was characterized by SEM analyses. The influence of hydrothermal deposition temperature on the microstructures of the as-prepared coatings and the deposition kinetics mechanism were investigated. Results show that dense and homogeneous C-AlPO4 coatings on SiC coated C/C composites can be achieved at 373K and 220V deposition voltage; Kinetics investigations show that the deposition process of the C-AlPO4 coatings on SiC coated C/C composite is controlled by the diffusion rate of the charged C-AlPO4 particles to the cathode; the deposition rate increases with the increase of hydrothermal temperature. The diffusion equation and the kinetic expression of coating process follow the Fick’s second law and Ahrennius relationship. The deposition activation energy of the C-AlPO4 coatings fabricated by the hydrothermal electrophoretic process is calculated to be 21.88kJ/mol.
Characterization of Silicon Carbide Grown on RB-SiC by Chemical Vapor Deposition
Authors: Meng Fan Tao , Du Shan Yi , Tian Gui Shan , Zhang Yu Min
Published: March 2010

Silicon carbide is one of the best materials for satellite mirror and chemical vapor deposition (CVD) is an effective method of preparing SiC whiskers and films. In this paper, SiC whiskers or films were deposited on substrates of RB-SiC in an upright chemical vapor deposition furnace of Φ150mm × 450 mm with methyltrichloride silicane (MTS) as precursor gas and H2 as carrier gas under dilute gases of different H2/Ar ratio and different deposition temperature between 1050°C and 1150°C. The morphology and composition of the CVD-SiC grown on RB-SiC substrate were determined by scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. As a result, whisker-like, worm-like or ball-like SiC can be respectively obtained dependent on different deposition conditions such as H2/Ar ratio and deposition temperature, and the composition of the productions are determined as β-SiC by XRD. Furthermore, the deposition mechanisms of different morphologies of SiC are introduced.
Characteristic of Palladium Coated Tubular Alumina Composite Membrane for Hydrogen Separation
Authors: Kitiwan Mettaya , Atong Duangduen
Published: March 2010

The palladium membrane has been developed for high temperature separation of hydrogen from other syngas molecules. In this study, tubular α-alumina substrate was used as a support for increase mechanical strength for thin palladium membrane. Prior depositing of palladium film, a dip-coating of palladium nuclei was performed to cover the substrate. Afterward, surface of activated support was modified with a thin intermediate layer for improving adhesion between support and Pd membrane. Electroless plating of dense palladium membrane was achieved from the plating bath containing EDTA stabilized palladium complex and hydrazine. The microstructural characteristics of palladium membranes were analyzed.
Reaction Synthesis of TiC-Ni Composite Coating on Copper Substrate Using Electro-Thermal Explosion Ultra-High Speed Spraying
Authors: Liu Jing Jing , Liu Zong De , Liu Dong Yu , Zhao Li Ping , Wang Liang , Xi Wei Chun
Published: March 2010

In this work, TiC-Ni coating was synthesized on copper substrate by electro-thermal explosion ultra-high speed spraying method at the discharge voltage of 26kV. Microstructure, phase structure, elemental distribution and microhardness of the coating were studied by means of scanning electron microscope in back-scatter-electron and secondary electron, energy-dispersive analysis X-ray spectroscopy, X-ray diffraction and Vickers hardness tester. The TiC-Ni coating, which exhibits no pores or cracks, consists of an irregular spheroidal TiC phase embedded in a nearly continuous Cu0.81Ni0.19 binder. TiC particles are uniformly distributed and the size of the TiC particle of the coating is less than 1.0 m because of the solute trapping effect. The average hardness of the TiC-Ni coating is approximately 1200 HV0.3.
Evaluating Absolute Hardness of Ceramic Coatings Using Relative Method
Authors: Li Kun Ming , Bao Yi Wang , Wan De Tian , Qiu Yan , Tian Li , Huang Jow Lay
Published: March 2010

Micro-hardness measurements of thin coatings have to face the problem of the influence of the substrate. Based on relative method and the relationship between the composite hardness (the hardness of the coated sample) and the substrate hardness, a new model is proposed to evaluate the absolute hardness of ceramic coatings. Indentation tests with various load levels were carried out with specimens of (Ti,Al)xN1-x/SiyN1-y composite coating on SKH51 steel substrate. The results were analyzed by the new model and compared with those calculated by J-H (Jönsson and Hogmark) and L-C (Lesage and Chicot) models. The mean coating hardness obtained from this model shows similar results with the J-H model but a little higher than that from L-C model.
Fabrication of Superhydrophobic Surfaces on Al Substrates for Anti-Adhesion and Self-Cleaning Applications
Authors: Li Tao , Liu Chang Song , Zhang Qiang , Li Zhi Wen
Published: March 2010

Superhydrophobic surfaces, which have anti-adhesion and self-cleaning properties, were fabricated on Al substrates. The self-cleaning surface was prepared by two steps: firstly, a chemical solution method was used to create the surface roughness with disorderly veins micronanostructures. Secondly, fluoroalkylsilane was deposited on the rough surface to lower its surface energy. The combination of veins micronanostructures and fluoroalkylsilane modification gave the surface a superhydrophobicity with static water contact angle of 166° and sliding angle of smaller than 1°. Additionally, the surface showed a strong anti-adhesion with water and a satisfied self-cleaning property. Water droplets easily rolled off the surface and picked up dirt and debris with them. The surfaces obviously corresponded to Cassie (not Wenzel) -model. Air entrapped within the veins microstructures greatly increases the air/water interface, effectively preventing the penetration of water into the grooves, and finally exhibiting the self-cleaning property. The results will greatly extend Al substrates for specific functions such as water-repellence, self-cleaning and anti-fouling.
Effects of Adding SiC Powder on the Properties of Carbon Fiber Reinforced Si-O-C Composites Fabricated via Precursor Pyrolysis
Authors: Liu Jing Yu , Jian Ke , Chen Zhao Hui , Fang Zhi Wei , Peng Xia Hui
Published: March 2010

Three dimensional carbon fiber reinforced silicon oxycarbide (3D Cf/Si-O-C) composites with low cost silicon resin as precursors and 3D Cf as reinforcement. Effects of adding SiC powder (SiCP) on the microstructure, mechanical properties and anti-oxidation properties of 3D Cf/Si-O-C composites were investigated. The results showed that adding SiCP filler could reduce the porosity and improve the interface bonding, therefore the properties of composites increased. But when the SiCP content was excessive, it was difficult to dense the matrix of composites at the further cycles and pores existed in the matrix. As a result, the mechanical properties of the composites decreased. It was found that when fabricated with 18.2 weight percent SiCP the composites exhibited highest mechanical properties, and the flexural strength and fracture toughness reached 421.3MPa and 13.0 MPa•m1/2, respectively. And the anti-oxidation properties were improved with the increase of the SiCP content. When fabricated with 25.0 weight percent SiCP the composites exhibited best oxidation resistance properties, and the composites retained 89.5% of original flexural strength.
Synthesis of TiO2/Muti-Walled Carbon Nanotubes Composite
Authors: Zhang Min , Zhang Na , Chu Jing , Sun Jing , Li Qiang
Published: March 2010

TiO2/Multi-walled carbon nanotubes (MWNTs) were prepared via a wet chemical route with hydrolysis of titanium salts. The purification and oxidation treatment of MWNTs in concentrated HNO3 solution were conducted to modify the nanotubes. Then the pre-treated carbon nanotubes were added into the titanium salt and in the end the composites were formed. The microstructure of as-prepared TiO2/MWNTs composite was studied by TEM. The samples were calcined at different temperature. By X-ray diffraction (XRD), the phase transformation of nano-structured TiO2 in composites was determined. The photocatalytic activity of samples being calcined at different temperature was studied by using the conversion of methyl orange in aqueous solutions as probe reaction. The influence of the structure on photocatalysis efficiency was discussed. By contrast with that of pure TiO2 nanoparticles, the special structure of TiO2/MWNT composite could remarkably improve the efficiency of the photocatalytic reaction. The results indicated that the excited e- in conduction band of TiO2 might transfer into MWNTs and the possibility of the recombination of e-/h+ pairs decreased.
Influence of the Processing Parameters on the Coating Hardness on LD10 A-Alloy
Authors: Pan Ming Qiang , Chi Guan Xin , Wei Dong Bo , Di Shi Chun
Published: March 2010

The paper discusses the influence of processing parameters on the hardness of LD10 aluminum alloy coating treated by the power source with positive and negative pulse in the alkaline electrolyte. Lots of experiments were done with different processing parameters including positive current density, negative current density, frequency, duty ratio, processing time and electrolyte temperature, and the micro-hardness tester HVS-1000 was used to measure the coating hardness. The results indicate that elevating the duty ratio, or reducing the frequency can be advantageous to improve the coating hardness, and the coating is the hardest treated in electrolyte at the 30°C. And when the value of the positive and negative current density is reasonable, and the processing time rationally matches with the current density, the coating with HV2800 can be obtained.
Preparation of Compositionally Graded CVD SiC Oxidation-Resistant Coating
Authors: Tang Jie , Huo Yan Li , Chen Yu Feng , Liu Hai Lin , Wang Chun Peng , Peng Xiao Ying
Published: March 2010

A SiC coating was chemical vapour deposited (CVD) on a Cf/SiC composite with the ratio of H2 and methyltrichlorosilane (MTS) changed gradually from 6:1 to 12:1 during the CVD processing. Energy-dispersive spectrometry (EDS) of the coating showed that the content of C decreased while Si increased continuously from the interface between coating and Cf/SiC substrate to the outside surface of coating. The obtained compositionally graded structure effectively reduced the generation of microcracks by releasing the mismatch of CTE of the coating and the composite.
Influence of Liquid Evaporation on the Components of SiC High Emissivity Coating
Authors: Yi J. , He Xiao Dong , Guan Chun Long
Published: March 2010

The process of Electron Beam-Physical Vapor Deposition (EB-PVD) preparing SiC coating with liquid evaporation was firstly discussed from a thermodynamic viewpoint. The results showed that the ratio of SiC in the as-deposited coating gradually increases and tends to reach a stable maximum of 0.73 with the evaporation temperature increase from 2500 K to 3400 K. To verify the thermodynamic analysis, amorphous SiC coating was deposited on Si substrate by EB-PVD at 3100 K. SiC concentration across the cross section of coating was calculated from the area of elements spectrum in X-ray photoelectron spectroscopy (XPS) depth profile analysis. The results showed that the average SiC concentration was about 0.7.
Deposition of Bioactive Titania Layers on Non-Metallic Substrates under Ambient Conditions due to Hydrolysis of Titanium Oxysulfate Solution
Authors: Xiao Fan , Song Ren Guo
Published: March 2010

Titania layer is deposited on polyethylene substrates when they are soaked in TiOSO4/H2O2 solution and aged in hot water. The aging in hot water promoted the precipitation of anatase and rutile in the surface layer, indicating that cleavage and recombination of the Ti-O-Ti bond took place. The Ti-OH functional groups were rearranged and emerged accompanying the structure relaxation in the layer. Moreover, the aging in hot water enhanced crystalline of titania and then obtained well apatite-forming ability on the polyethylene substrates in SBF. This was accounted for by the removal of residual impurities due to TiOSO4/H2O2 treatment. They had an anatase/rutile dual layer microstructure: the dense bottom layer predominantly consisted of rutile, while the upper layer consisted of loosely packed aggregation of anatase particles. The titania deposition was the results of compromise among two conflicting processes: 1) hydrolysis of titanium oxysulfate to yield either soluble titanol-complexes or titania, 2) dissolution of the titania under the presence of hydrogen peroxide to yield similar complexes or compounds. Various soaking periods were carried out to investigate the dissolution-deposition equilibrium in the solution. Anatase/rutile dual layers were thus deposited on titanium and polyethylene substrates when they were soaked in TiOSO4/H2O2 solution and aged in hot water. The proper soaking time in the treating solution is the other key factors to control the formation of dense titania layers. The resulted titania layers have apatite-forming ability.
UV-Enhanced Bioactivity of PS/TiO2 Coating Prepared by Layer-by-Layer Self-Assembly Method
Authors: Zhang Zhi Xian , Xiao Fan , Gao Fei
Published: March 2010

The TiO2 nanopowder was prepared with TiOSO4 as raw material at low temperature by hydrolysis method, and microspheres coated polyethylene and TiO2 were then fabricated on titanium by layer-by-layer self-assembly technology. Using ultraviolet irradiation of titanium coating in distilled water for some time, titanium with enhanced bioactivity was achieved when immersed in simulated body fluid (SBF). The morphology, size and crystal shape before and after ultraviolet irradiation were characterized by scanning electron microcopy (SEM) and X-ray diffraction (XRD). UV irradiation of titanium results in the conversion of Ti4+ to Ti3+ and the generation of oxygen vacancies, which could react with the absorbed water to form basic Ti–OH groups. Compared with the coating non-UV irradiation, the UV-irradiated coatings do not present any obvious differences in morphology, surface roughness, grain size and phase component; however, they have more abundant basic Ti–OH groups thus the water contact angle decreases greatly so the surface become much more hydrophilic.
The Color of Fe2O3 and Bi2O3 Pigmented Dental Zirconia Ceramic
Authors: Wen Ning , Yi Yuan Fu , Zhang Wei Wei , Deng Bing , Shao Long Quan , Dong Li Min , Tian Jie Mo
Published: March 2010

The aim of this study was to explored the effects of Fe2O3 and Bi2O3 on the color properties of a 3Y-TZP zirconia ceramics for dental application. Pigmented dental ZrO2 powders were prepared by mixing different concentration of Fe2O3 and Bi2O3, also in their combinations with 3Y-TZP powders. The mixture was compacted by isostastic pressure, then densely sintered. Color parameters were measured by Minolta CM2600d spectrophotometer. XRD was used to exam the structure of colored 3Y-TZP. Experimental results showed that the hue of the materials shift from yellow-green to yellow-red with the increasing concentration of the Fe2O3 and Bi2O3. Combined use of Fe2O3 and Bi2O3 could further decrease the L* value, which color scope was suitable for dental color matching. The XRD spectra showed only tetragonal phase was detected.
Effect of Ceria Additive on Microstructure and Properties of Laser-Cladded Bioceramic Coating
Authors: Zheng Min , Fan Ding , Zhang Jian Bin , Li Xiu Kun
Published: March 2010

The calcium phosphate bioceramic coating was fabricated on titanium alloy (Ti-6Al-4V) substrate by a 5kW continuous transverse flow CO2 laser. Due to the peculiar role of rare earth oxide in laser cladding, the effect of ceria additive on the microstructure and properties of laser-cladded bioceramic coating was investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), microhardness and corrosion resistance testing. The results indicate that the appearance of rare earth oxide ceria in the precursor powders has an impact on the microstructure and properties of the laser-cladded bioceramic coating. Calcium phosphate bioceramic such as hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) are synthesized on the top surface of laser-cladded specimens. And the addition of rare earth oxide ceria in pre-placed powders has an influence on the formation of calcium phosphate bioceramic phases. Furthermore, it reveals that the laser-cladded bioceramic coating of ceria additive in pre-placed powders has more favorable microhardness and corrosion resistance compared with the coating without rare earth oxide.
Preparation and Properties of Injectable Hydroxyapatite for Bone Repair Materials
Authors: Liu Hua , Chen Xiao Feng , Zhou Chang Ren
Published: March 2010

The aim of this study was to develop a novel injectable hydroxyapatite for bone repair materials. This study was based on the in situ setting properties of calcium phosphate cement (CPC), which properties were improved. The solid phase consisted of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). The liquid phase was the weak acidic solution of chitosan. The CPC powder was mixed with the chitosan solution to form a paste that could conform to the bone cavity even for irregularly shaped cavities. All the by-production disappeared by neutralization reaction. The CPC paste could then set in situ to form hydroxyapatite (HA) as the final product. The chemical process of CPC hydration was studied. The process was controlled by dissolution and precipitation chemical reaction. The kinetic model of hydration reaction was established. The effects of preparing conditions, such as powder to liquid ratio and particle size, on setting time and compressive strength were investigated systematically. The optimal condition was that the liquid phase contained 3% chitosan, 5% citric acid and 15% glucose (wt%), powder to liquid ratio was 0.8 g/ml, and powders were respectively ground for 40 hours.