The Dielectric Properties and Preparation Method of BaTiO3/PVDF 0-3 Composites

A series of 0-3 composties of the polyvinylidene fluoride (PVDF) and BaTiO3 was prepared,BaTiO3 was modified with titanate coupling agent .The dielectric properties and the interfacial interaction of composites by different preparation methods were examined and compared,The result shows that the relaive dielectric constant ε of the composite prepared in solution has a maximum value at about 70% weight fraction of BaTiO3 and the dielectric loss tanδ increases rapidly when the fraction exceeds 70%, For the composite preared in melt, the relative dielectric constant ε almost raches a maximum value at about 60% weght fraction of BaTiO3 and the dielectric loss is comparatively lower,The deielectric proerties of composites ore improved by using a coupling aent.     

Effect of milling process on the core-shell structures and dielectric properties of fine-grained BaTiO3-based X7R ceramic materials

Fine-grained BaTiO3-based X7R ceramic materials were prepared and the effects of milling process on the core-shell structures and dielectric properties were investigated using scanning electron microscope, transmission electron microscope, and energy dispersive spectroscopy (EDS). As the milling time extends, the dielectric constant of the ceramics increases, whereas the temperature coefficient of capacitance at 125°C drops quickly. The changes in dielectric properties are considered relevant to the micro-s...     

Effect of tunnel structure on the specific capacitance of etched aluminum foil

The morphology of etched aluminum foil was observed using scanning electron microscopy, which led to the establishment of a cylindrical model and two merged models, considering the fixed weight loss of etching. The maximum of specific capacitance and the cor- responding optimum values for tunnel sizes at various anodization voltages were predicted. The increased size distribution and taper of tun- nels were demonstrated to decrease the specific capacitance, whereas the addition of polymeric additive into the ttmnel widening solution was demonstrated to increase the capacitance. The formation of merged tunnels on the etched aluminum surface, irrespective of the presence of row-merged tunnels or cluster-merged tunnels, resulted in a dramatic decrease in the specific capacitance. It is concluded that, enhancing the uniformity of turmel size and distribution and avoiding the formation of merged tunnels are the effective approach to achieving the higher capacitance for the tunnel etched and formed aluminum foil.     

Phase Structure and Dielectric Properties of Doped BaTiO3 Ceramics

The effects of two rare earth oxides such as CeO2 and Sm2O3 on the phase structure and dielectric properties of BaTiO3 ceramic were investigated. Results indicate that the dielectric constant of this system will increase greatly with the increasing content of these two oxides, and Ce^4＋ substitutes for Ba^2＋ located at A-site in ABO3 structure. Quantitative XRD analysis shows that c/a ratio in the sample with addition of CeO2 will increase, which implies the increase of tetragonality in system, causing the augment of dielectric constant, and the decrease of the crystal＇s geometrical symmetry results in curie-temperature moving towards low temperature; Sm^3＋（0.096 nm） substitutes for Ba^2＋（0.135 nm） possessing larger radius in A-site and the electrovalency in A-site increases, the mutual effect is strengthened, so the polarization is enhanced, and the dielectric constant increases notablely.     

Effect of different forms of silica on sintering,microstructure and properties of borosilicate glass/Al2O3 composites

The effects of the introduction of silica glass and silica ceramic into Ca-Al-B-Si-O glass/ Al2O3 composites on decreasing the shrinkage and the dielectric constant of samples were investigated by FTIR, DSC, XRD and SEM. The results show that silica ceramic filler can better improve the formation of Si– O–Si network in the composites under high temperature, which leads to increased continuity of glass network at high temperature, and deduces the increase of viscosity of composites and further results in the decrease in the shrinkage of samples. Densification, three-point strength, and dielectric constant of samples decrease with the increase of silica glass or silica ceramic content. By contrast, Ca-Al-B-Si-O glass/Al2O3 composites with 4 wt% silica ceramic exhibit better properties of a bulk density of 2.81 g cm-3, a porosity of 0.3%, a 3dp value of 202 MPa, a ε r value of 7.41, a tan δ value of 8.3×10-4at 10 MHz and a well matching with Ag electrodes. This material is suitable to be used as the LTCC material for the application in wireless communications.     

Dielectric and Piezoelectric Properties of 0-3 PZT/PVDF Composite Doped with Polyaniline

Lead zirconate titanate （ PZT ） / polyvinylidene fluoride （PVDF） 0-3 piezoelectric composites doped with polyaniline （PANI） were obtained by hot-press method. The polarization properties of the composites were characterized by XRD and P- E hysteresis loops at room temperature. And the dielectric and piezoelectric properties were also measured. The results show that the poling of PZT could be effectively carried oat and the dielectric constant e, and dissipation tanδ increase monatonously by increasing the volume fraction of PANI in the composite. The piezoelectric constant d33, and the planar electromechanical coupling factor kp increase while the mechanical quality factor Qm decreases with the increase in the content of PANI. The d33, kp and Qm show the extremum values at 8 vol%-10 vol% PANI.     

Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 Complex Perovskite Ferroelectric Ceramics with High Dielectric Constant and Low Firing Temperature

The effects of different firing temperatures on the stability of perovskite phase, grain size, and dielectric properties were investigated by XRD, TEM, SEM and dielectric measurements. The dielectric ceramics of Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system were obtained by chemical coprecipitation in water. The ceramics have higher dielectric constant (7003-9714), lower firing temperature(950-1150℃), quite uniform microstructure with grain size less than 2.5 mp, and lower temperature coefficients of capacitance. As a re-sult, it was confirmed that the simple and low cost chemical route used namely coprecipitation in water is a desired method for preparinghigh property dielectfic materials applicable to multilayer capacitors.     

Growth characterization of anodic film on AZ91D magnesium alloy in an electrolyte of Na2SiO3 and KF

Anodization of AZ91D magnesium alloy in the electrolyte solution of 0.5 mol/L of sodium silicate and 1.0 mol/L of potassium fluoride was investigated. The anodic films were characterized using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The corrosion resistance of the various anodized alloys was evaluated by a fast corrosion test using the solution of hydrochloric acid and potassium dichromate. The results showed that the addition of KF resulted in the presence of NaF in the anodic film. The thickness of the anodic film formed under a constant current density of 20 mA/cm2 for 16 min at 60℃ exceeded 100 μm. The growth of the anodic film could be divided into three stages based on the anodizing time; the growth rate was much faster during stage Ⅱ than in stages Ⅰ and Ⅲ. The anodic film exhibited the highest corrosion resistance for the AZ91 alloy,which is attributed to the fact that the anodization was maintained until the end of stage Ⅱ.     

Effect of Ni-doping on electrochemical capacitance of MnO2 electrode materials

Mn/Ni composite oxides as active electrode materials for supercapacitors were prepared by solid-state reaction through the reduction of KMnO4 with manganese acetate and nickel acetate at low temperature. The products were characterized by X-ray diffractometry(XRD) and transmission electron microscopy(TEM). The electrochemical characterizations were performed by cyclic voltammetry (CV) and constant current charge-discharge in a three-electrode system. The effects of different potential windows, scan rates, and cycle numbers on the capacitance behavior of Mn0.8Ni0.2Ox composite oxide were also investigated. The results show that the composite oxides are of nano-size and amorphous structure. With increasing the molar ratio of Ni, the specific capacitance goes through a maximum at molar fraction of Ni of 20%. The specific capacitance of Mn0.8Ni0.2Ox composite oxide is 194.5 F/g at constant current discharge of 5 mA.     

Fabrication of independent nickel microstructures with anodizing of aluminum, laser irradiation, and electrodeposition

Independent microstructures made of Ni metal were fabricated by five sequential processes: porous anodic oxide film formation, pore sealing, laser irradiation, Ni electroplating, and removal of the aluminum substrate and anodic oxide films. Aluminum plates and rods were anodized in an oxalic acid solution to form porous type anodic oxide films, and then immersed in boiling distilled water for pore sealing. The anodized and pore-sealed specimens were irradiated with a pulsed neodymium-doped yttrium aluminum garnet (Nd-YAG) laser beam in a Ni plating solution to remove anodic oxide film locally by rotating and moving up / down with an XYZθ-stage. Nickel was deposited at the area where film had been removed by cathodic polarization in the solution before removing the aluminum substrate and anodic oxide films in NaOH solutions. Cylindrical or plain network structures were fabricated successfully.     

Morphology and growth of porous anodic oxide films on Ti-10V-2Fe-3Al in neutral tartrate solution

Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time. Scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM) were used to investigate the morphology evolution of the anodic oxide film. It is shown that above the breakdown voltage, oxygen is generated with the occurrence of drums morphology. These drums grow and extrude, which yields the compression stress. Subsequently, microcracks are generated. With continuous anodizing, porous oxides form at the microcracks. Those oxides grow and connect to each other, finally replace the microcrack morphology. The depth profile of the anodic oxide film formed at 1 800 s was examined by Auger electron spectroscopy (AES). It is found that the film is divided into three layers according to the molar fractions of elements. The outer layer is incorporated by carbon, which may come from electrolyte solution. The thickness of the outer layer is approximately 0.2–0.3 μm. The molar fractions of elements in the intermediate layer are extraordinarily stable, while those in the inner layer vary significantly with sputtering depth. The thicknesses of the intermediate layer and the inner layer are 2 μm and 1.0–1.5 μm, respectively. Moreover, the growth mechanism of porous anodic oxide films in neutral tartrate solution was proposed.     

Morphology and conductivity of in-situ PEO-LiClO4-TiO2 composite polymer electrolyte

PEO-LiClO4-TiO2 composite polymer electrolyte films were prepared. TiO2 was formed directly in matrix by hydrolysis and condensation reaction of tetrabutyl titanate. The crystallinity, morphology and ionic conductivity of composite polymer electrolyte films were examined by differential scanning calorimetry, scanning electron microscopy, atom force microscopy and alternating current impedance spectroscopy, respectively. The glass transition temperature and the crystallinity of composite polymer electrolytes are decreased compared with those of PEO-LiClO4 polymer electrolyte film. The results show that TiO2 particles are uniformly dispersed in PEO-LiClO4-5%TiO2 composite polymer electrolyte film. The maximal conductivity of 5.5×10^-5 S/cm at 20℃ of PEO-LiClO4-TiO2 film is obtained at 5% mass fraction of TiO2.     

Study on the thermal stability and electrical properties of the high-k dielectrics (ZrO2)x(SiO2)1?x

(ZrO₂) _x (SiO₂)_1−x (Zr-Si-O) films with different compositions were deposited on p-Si(100) substrates by using pulsed laser deposition technique. X-ray photoelectron spectra (XPS) showed that these films remained amorphous after annealing at 800°C with RTA process in N₂ for 60 s. The XPS spectra indicated that Zr-Si-O films with x=0.5 suffered no obvious phase separation after annealing at 800°C, and no interface layer was formed between Zr-Si-O film and Si substrate. While Zr-Si-O films with x >0.5 suffered phase separation to precipitate ZrO₂ after annealing under the same condition, and SiO₂ was formed at the interface. To get a good interface between Zr-Si-O films and Si substrate, Zr-Si-O films with bi-layer structure (ZrO₂)_0.7(SiO₂)_0.3/(ZrO₂)_0.5(SiO₂)_0.5/Si was deposited. The electrical properties showed that the bi-layer Zr-Si-O film is of the lowest equivalent oxide thickness and good interface with Si substrate. Supported by the National Nature Science Foundation of China (Grant No. 60636010) and the National Basic Research Program of China (“973” Program) (Grant No. 2004CB619004)     

Effect of silver growth temperature on the contacts between Ag and ZnO thin films

Highly c-axis oriented ZnO thin films were deposited on Si substrates by the pulsed laser deposition (PLD) method. At different growth temperatures, 200 nm silver films as the contact metal were deposited on the ZnO thin films. The growth temperatures have great influence on the crystal quality of Ag films. Current-voltage characteristics were measured at room temperature. The Schottky contacts between Ag and ZnO thin films were successfully obtained when silver electrodes were deposited at 150°C and 200°C. Ohmic contacts were formed while the growth temperatures were lower than 150°C or higher than 200°C. After analysis, the forming of Ag/ZnO Schottky contacts was shown to be dependent on the appearance of the p-type inversion layer at the interface between Ag and ZnO layers.     

Optimization of the process for preparing Al-doped ZnO thin films by sol-gel method

Transparent and conducting Al-doped ZnO thin films with c-axis-preferred orientation were prepared on glass substrate via sol-gel route. The physical and chemical changes during thermal treatment were analyzed by TG-DSC spectra and the crystallization quality was characterized by XRD patterns. The optimized preheating and post-heating temperatures were determined at ~420℃ and ~530℃, respec-tively. From thermodynamic and kinetics views, we investigated the mechanism of orientation growth with (002) plane parallel to the substrates. The surface morphologies of the films, post-heated at 420℃, 450℃, 530℃ and 550℃, respectively, were observed by SEM micrographs. The film post-heated at 530℃ shows a homogenous dense microstructure and exhibits the minimum sheet resistance of 140 Ω/Sq. The visible optical transmittance of all the films is beyond 90%. In addition, the annealing treatment in vacuum can contribute greatly to the electrical conductivity.     

Manufacture of high-dispersed W-Cu composite powder by mechano-thermal process

In order to improve the process of co-reduction of oxide powder, a new mechano-thermal process was designed to produce high-dispersed W-Cu composite powder by high temperature oxidation, short time high-energy milling and reduction at lower temperature. The particle size, oxygen content and their sintering abilities of W-Cu composite powder in different conditions were analyzed. The results show that after a quick milling of the oxide powder for about 3-10 h, the reduction temperature of the W-Cu oxide powder can be lowered to about 650 ℃ from 700-750 ℃ owning to the lowering of particle size of the oxide powder. The average particle size of W-Cu powder after reduction at 650 ℃ is about 0. 5μm smaller than that reduced at 750 ℃. After sintering at 1 200℃ for 1 h in hydrogen atmosphere, the relative density and thermal conductivity of final products (W-20Cu) can attain 99. 5% and 210 W ·m-1· K-1 respectively.     

Influence of annealing time on the microstructure and properties of Pb(Zr0.53Ti0.47)O3 thin films

The PZT thin films were prepared on (111)- Pt/Ti/SiO2/Si substrates by sol-gel method, and lead acetate [Pb(CH3COO)2], zirconium nitrate [Zr(NO3)4] were used as raw materials. The X-ray diffractometer (XRD) and scanning electron microscopy (SEM) were used to characterize the phase structure and surface morphology of the films annealed at 650 ℃ but with different holding time. Ferroelectric and dielectric properties of the films were measured by the ferroelectric tester and the precision impedance analyzer, respectively. The PZT thin films were constructed with epoxy resin as a composite structure, and the damping properties of the composite were tested by dynamic mechanical analyzer (DMA). The results show that the films annealed for 90 minutes present a dense and compact crystal arrangement on the surface; moreover, the films also achieve their best electric quality. At the same time, the largest damping loss factor of the composite constructed with the 90 mins-annealed film shows peak value of 0.9, higher than the pure epoxy resin.     

Property improvement of multilayer TiN/Ti films with C+ implantation

Using the MEVVA ion source, carbon ions have been implanted in TiN coatings deposited by multiarc ion plating. The Vickers microhardness of the C⁺-implanted TiN films increased with the increase in the ion flux and dose. X-ray diffraction (XRD) analysis showed that the TiC phases had been formed in the films. In addition, the films had the preferred growth orientations of TiN and TiC, both of which were (111) orientation after annealing at 500°C for 30 min. Auger electron spectra analysis indicated that C⁺-implanted profile was in typical Gaussian-like distribution in single films. The distribution with multipeaks of C atoms was obtained in multi-layer TiN/Ti. The possibility of the multilayer films (Ti(C,N)/TiN/Ti(C,N)/TiN and Ti(C,N)/TiC/Ti(C,N)/TiC) forming using the C-implanted TiN/Ti films is presented for the first time. Project supported by the National Natural Science Foundation of China and the “863” Hi-Tech Program of China.     

Effects of Thickness on the Electrical Conductivity of Sputtered YSZ Film with Nanocrystalline Columnar Microstructure

In order to investigate the effect of the thickness on the electrical conductivity of yttriastabilized zirconia(YSZ) film, the nanocrystalline columnar-structured YSZ film with thickness of 0.67-2.52 μm was prepared by magnetron sputtering through controlling the deposition time. All the sputtered films with different thicknesses consist of the main phase of cubic YSZ as well as a small amount of monoclinic YSZ. The thicker films exhibit a typical columnar grain structure based on the fractured cross-sectional SEM observations. The average diameters of columnar grains increase from about 40 nm to 100 nm with the film thickness from 0.67 μm to 2.52 μm according to TEM analysis. The thinnest YSZ film with 0.67 μm thickness shows the highest apparent electrical conductivity in the four films in 400-800 ℃ due to the contribution from the highly conductive film/substrate interfacial region. On the other hand, the real electrical conductivities of YSZ films increase with film thickness from 0.67 μm to 2.52 μm after eliminating the contribution of the film/substrate interface. The increasing film thickness leads to the grain growth as well as the decrement in the volumetric fraction of the resistive columnar grain boundary and a consequent higher real electrical conductivity.     

Extraordinary self-lubrication properties of non-hydrogenated diamond-like carbon films under humid atmosphere

Tribological properties of non-hydrogenated diamond-like carbon (DLC) films were investigated under humid (RH=80%) and dry (RH=5%) air. These films were deposited by pulsed laser deposition (PLD) at different substrate temperatures. Tribological properties of DLC fabricated by PLD is not sensitive to the relative humidity of testing environment. Because of the unique growth mechanism of DLC prepared by PLD, DLC is of “soft-hard” double layers, having a very low friction coefficient and wear rate under humid atmosphere. The minimum coefficient and wear rate of film under humid circumstance are 0.045 and 5.94×10⁻¹⁰ mm³N⁻¹m⁻¹, respectively, just a little bit more than those under dry condition. The root means square roughness of film is less than 1 nm. The sp³ content of film grown at room temperature (RT) is 72%, and the sp³ content decreases with temperature. Raman spectrum shows that the micro-structure is amorphous network. The largest hardness and elastic modulus of film are 51 GPa and 350 GPa, respectively and they reduce with increase of deposition temperature too. Water contact angles on surface are more than 90° which indicates that films fabricated by PLD are hydrophobic with low surface energy.