Charge state of composites based on polyethylene with semiconductor filler TlInSe<Subscript>2</Subscript>

In the present work, the spectra of currents of thermostimulated depolarization for composite corona electret LDPE + ε vol % TlInSe₂ are obtained by the thermoactivation spectroscopy method [11] and their electret properties and change conditions are investigated.     

Atomic force microscopy studies of the surface relief of composites of high-density polyethylene and additives of TlGaSe<Subscript>2</Subscript> and the analysis of their dielectric properties

In this work, we describe a technique for the preparation of composites of high-density polyethylene and additives of TlGaSe₂, the atomic force microscopy studies of their surface relief, and the analysis of their dielectric properties.     

Oxidation resistant Mo-Mo<Subscript>2</Subscript>B-silica and Mo-Mo<Subscript>2</Subscript>B-silicate composites for high temperature applications

Development of Mo composites based on the Mo-Si-B system has been demonstrated as a possible new route to achieving a high temperature Mobased material. In this new system, the silicide phases are replaced directly with silica or other silicate materials. These composites avoid the high ductile to brittle transition temperature observed for Mo-Si-B alloys by removing the Si that exists in solid solution in Mo at equilibrium with its silicides. A variety of compositions is tested for room temperature ductility and oxidation resistance. A system based upon Mo, Mo₂B, and SrO·Al₂O₃·(SiO₂)₂ is shown to possess both ductility at 80 vol.% Mo and oxidation resistance at 60 vol.%. These composites can be produced using a powder processing approach and fired to greater than 95% theoretical density with a desirable microstructure of isolated boride and silicate phases within a ductile Mo matrix.     

Studies on Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> high K gate dielectrics applied in a fully depleted SOI MOSFET

Al₂O₃/ZrO₂/Al₂O₃ gate stacks were prepared on ultrathin SOI (Silicon on insulator) substrates by ultrahigh vacuum electron beam evaporation and post-annealed in N₂ at 450°C for 30 min. Three clear nanolaminate layered structure of Al₂O₃(2.1 nm)/ZrO₂(3.5 nm)/Al₂O₃(2.3 nm) was observed with a high-resolution cross-sectional transmission electron microscope (HR-XTEM). High frequency capacitance voltage (C-V) characteristics of a fully depleted (FD) SOI MOS capacitor at 1 and 5 MHz were studied. The minority carriers determine the high frequency C-V properties, which is opposite to the case of bulk MOS capacitors. The series resistance of the SOI substrate is found to be the determinant factor of the high frequency characteristics of FD SOI MOS capacitors. This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24≈27, 2003.     

Effects of nano-TiO<Subscript>2</Subscript> dispersion on thermoelectric properties of Co<Subscript>4</Subscript>Sb<Subscript>11.7</Subscript>Te<Subscript>0.3</Subscript> composites

Nano-TiO2/Co4Sb11.7Te0.3 composites were prepared by mechanical alloying (MA) and cold isostatic pressing (CIP) process.The phase composition,microstructure,and thermoelectric properties were characterized.The diffraction spectra of all samples well corresponds to CoSb3 skutterudite diffraction plane.TiO2 agglomerates into irregular clusters.They locate at the grain boundaries or some are distributed on the surface of Co4Sb11.7Te0.3 particles.For composites with high TiO2 content (0.6% and 1.0% TiO2),the phonon scattering by TiO2 particle,pores,and small size grains can result in a remarkable reduction in thermal conductivity.The maximum value of ZT is 0.79 for sample with 0.6 wt.% TiO2 at 700 K,which is 11% higher than that of non-dispersed sample.     

Rapid synthesis and consolidation of nanostuctured Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-MgSiO<Subscript>3</Subscript> composites by high frequency induction heated sintering

Nanopowders of MgO, Al₂O₃ and SiO₂ were made by high energy ball milling. The rapid sintering of nanostuctured Al₂O₃-MgSiO₃ composites was investigated by the high-frequency induction heating sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and inhibits grain growth. Highly dense nanostructured Al₂O₃-MgSiO₃ composites were produced with the simultaneous application of 80 MPa pressure and the induced output current of total power capacity (15 kW) within 2 min. The sintering behavior, grain size and mechanical properties of Al₂O₃-MgSiO₃ composites were investigated.     

Magnetoelectrical effect in layered composites PbZr<Subscript>0.53</Subscript>Ti<Subscript>0.47</Subscript>O<Subscript>3</Subscript>-Mn<Subscript>0.4</Subscript>Zn<Subscript>0.6</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>

The magnetoelectric (ME) effect in two- and three-layered composites made up of polarized ceramic plates of lead zirconate-titanate PbZr_0.53Ti_0.47O₃ (PZT) and manganese-zinc ferrite Mn_0.4Zn_0.6Fe₂O₄ (MZF) has been studied. Dependences of the transverse ME voltage coefficient (α₃₁) on the magnetostrictive layer thickness and the magnetic field intensity and frequency have been established. The mechanical coupling coefficient of the composite plates has been estimated. Results obtained for two-layered PZT-MZF structures have been analyzed using the method of efficient medium parameters.     

Rapid consolidation of nanocrystalline Ti<Subscript>3</Subscript>Al-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites from mechanically synthesized powders by high frequency induction heated sintering

Nano-powders of Ti₃Al and ²Al₂O₃ were synthesized from 3TiO₂ and 5Al powders by high energy ball milling. Nanocrystalline Al₂O₃ reinforced composite was consolidated by high frequency induction heated sintering within 2 minutes from mechanochemically synthesized powders of 2Al₂O₃ and Ti₃Al. The relative density of the composite was 99.5%. The average hardness and fracture toughness were 1340 kg/mm² and 8 MPa·m^1/2, respectively.     

Up-Date of a Thermodynamic Database of the ZrO<Subscript>2</Subscript>-Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> System for TBC Applications

The thermodynamic database of the ZrO₂-Gd₂O₃-Y₂O₃-Al₂O₃ system is up-dated taking into account new data on lattice stabilities of ZrO₂, Gd₂O₃ and Y₂O₃ and heat capacity measurements for the monoclinic phase Gd₄Al₂O₉ and phase with garnet structure Gd₃Al₅O₁₂. New data for the heat capacities of Gd₂Zr₂O₇ (pyrochlore) and GdAlO₃ (perovskite) as well as on the enthalpy of formation of fluorite solid solutions (Zr_1−x Gd _x )O_2−x/2 were found to be in good agreement with calculated results. In comparison with the previous assessment, taking into account new experimental data resulted in a change of the melting character of the Gd₄Al₂O₉ phase from a peritectic one to a congruent one in the Gd₂O₃-Al₂O₃ system. Correspondently, in the ternary system ZrO₂-Gd₂O₃-Al₂O₃, the melting character of the three-phase assemblage Gd₂O₃ (B), Gd₄Al₂O₉ and GdAlO₃ changed from eutectic to transition type U. The T ₀-lines for T/M and F/T diffusionless transformations and driving force of partitioning to equilibrium assemblage T + F were calculated in the ZrO₂-Gd₂O₃-Y₂O₃ system.     

Electrothermopolarization influence upon the structure and properties of a composition on the basis of polyethylene and Co(AlO<Subscript>2</Subscript>)<Subscript>2</Subscript>

The influence of electrothermopolarization on the structure and properties (electret, strength) of a composition on the basis of polyethylene and a low-molecular dye Co(AlO₂)₂ was investigated. It was experimentally established that the additive Co(AlO₂)₂ changes the polyethylene structure. As a result, the electret properties of the composition change. Correlation of the strength properties with the changes of the degree of the crystallinity of the polyethylene was observed.     

Synthesis and photocatalytic properties of lanthanum doped anatase TiO<Subscript>2</Subscript> coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> composites

A composite photocatalyst (La/TiO<,2>/Fe<,3>O<,4>) with a lanthanum doped TiO<,2> (La/TiO<,2>) shell and a magnetite core was prepared by coating photoactive LafTiO<,2> onto a magnetic Fe<,3>O<,4> core. The morphological, structural, and optical properties of as-prepared samples were charac- terized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy. The effect of lanthanum content on the photocatalytie properties was studied, and the result revealed that 0.15 mol% La/TiO<,2>/Fe<,3>O<,4>exhibited the highest photoactiv- ity. The photocatalytic properties of the prepared photocatalyst under UV and visible light were investigated in aqueous solution using methyl orange (MO) as a target pollutant. The results showed that the prepared photocatalyst was activated by visible light and used as an ef- fective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, La/TiO<,2> was tightly bound to Fe<,3>O<,4> and could be easily recovered from the medium by a simple magnetic process.     

Rapid consolidation of nanocrystalline NbSi<Subscript>2</Subscript>-Si<Subscript>3</Subscript>N<Subscript>4</Subscript> composites by pulsed current activated combustion synthesis

A dense nanostructured 4NbSi₂-Si₃N₄ composite was synthesized by a Pulsed Current Activated Combustion Synthesis (PCACS) method within 3 minutes in one step from mechanically activated powders of NbN and Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. A highly dense 4NbSi₂-Si₃N₄ composite with a relative density of up to 98 % was produced under simultaneous application of a 60 MPa pressure and the pulsed current. The average hardness and fracture toughness values obtained were 700 kg/mm² and 3.5 MPa·m^1/2, respectively     

Phase Diagram of the Quaternary Al(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>-Cu(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-Zn(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>-H<Subscript>2</Subscript>O System

The phase diagram of the H₂O-Zn(NO₃)₂-Al(NO₃)₃-Cu(NO₃)₂ quaternary system at 30 °C has been established by using the conductivity measurements. The solid-liquid equilibria of the H₂O-Zn(NO₃)₂-Al(NO₃)₃, H₂O-Zn(NO₃)₂-Cu(NO₃)₂, H₂O-Al(NO₃)₃-Cu(NO₃)₂ ternary systems and two isoplethic sections were determined experimentally. The solid phases in equilibrium with the saturated solution are the tri- and hemipentahydrate of copper nitrate, the hexahydrate α and β of the zinc nitrate and the nonahydrate of aluminum nitrate. The copper and zinc nitrates are relatively soluble in opposition to the aluminum nitrate which presents some important precipitation domains.     

Sol-gel preparation and characterization of Li1.3Al0.3Ti1.7（PO4）3 sintered with flux of LiBO2

Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ were prepared by sol-gel method. The structural identification, surface morphology, ionic conductivity, and activation energy of the pellets were studied by X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. The results show that all the Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ have similar X-ray diffraction patterns. The sintered pellet becomes denser and the boundary and corner of the particles become illegible with the increase of LiBO₂. Among the Li_1.3Al_0.3Ti_1.7(PO₃)₄ pellets sintered with different mole fractions of LiBO₂, the one sintered with 1 mol% LiBO₂ shows the highest ionic conductivity of 3.95×10⁻⁴ S.cm⁻¹ and the lowest activation energy of 0.2469 eV.     

Thermodynamic Assessment of PrCl<Subscript>3</Subscript>-CaCl<Subscript>2</Subscript> and NdCl<Subscript>3</Subscript>-CaCl<Subscript>2</Subscript> Systems

By using the CALPHAD technique, an assessment of the binary PrCl₃-CaCl₂ and NdCl₃-CaCl₂ systems have been carried out. From measured phase equilibrium data and experimental integral properties, the PrCl₃-CaCl₂ and NdCl₃-CaCl₂ phase diagrams were optimized and calculated. A set of thermodynamic functions has been optimized based on an interactive computer-assisted analysis. The calculated results by present method agree well with the experimental data.     

Viscosity and Structure of CaO-SiO<Subscript>2</Subscript>-P<Subscript>2</Subscript>O<Subscript>5</Subscript>-Fe<Subscript>t</Subscript>O System with Varying P<Subscript>2</Subscript>O<Subscript>5</Subscript> and FeO Content

A rotary viscosimeter and Raman spectrum were employed to measure the viscosity and structural information of the CaO-SiO₂-P₂O₅-Fe_tO system at 1673 K. The experimental data have been compared with the calculated results using different viscosity models. It shows that the National Physical Laboratory (NPL) and Pal models fit the CaO-SiO₂-P₂O₅-FeO_t system better. With the P₂O₅ content increasing from 5% to 14%, the viscosity increases from 0.12 Pa s to 0.27 Pa s. With the FeO content increasing from 30% to 40%, the viscosity decreases from 0.21 Pa s to 0.12 Pa s. Increasing FeO content makes the complicated molten melts become simple, and increasing P₂O₅ content will complicate the molten melts. The linear relation between viscosity and structure parameter Q(Si + P) was obtained by regression analysis. The calculated viscosity by using the optimized NPL and Pal model are almost identical with the fitted values.     

PbO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> composite electrodes

Electrodeposition of composite PbO₂-based materials containing titanium dioxide particles was studied. The TiO₂ content of the composite depends on the bath composition and the deposition conditions. Inclusion of TiO₂ particles in PbO₂ substantially changes the morphology and structure of the deposit. The oxygen overpotential at composite materials increased but the rate of the conversion of 4-chlorophenol into nontoxic compounds remained virtually unchanged. The lifetime of the electrodes containing the inert TiO₂ phase was found to be twice as long as that of traditional PbO₂ anodes.     

Preparation and optical properties of Y<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> powder

Y(NO3)3 and NH3·H2O were used as a raw materials,and nano-Y2O3 powder was successfully synthesized by a precipitation method.Employing TEOS as a raw material,SiO2 powder was successfully prepared by a alkoxide-hydrolysis method,and a Y2O3/SiO2 composite powder was obtained by coating.The Y2O3,SiO2,and Y2O3/SiO2 powders were characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),and Fourier transform infrared spectrophotometer(FT-IR);the Y2O3 and Y2O3/SiO2 powders were further examined ...     

Preparation and characterization of nanostructured Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> and Sn<Subscript>0.5</Subscript>-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript>

Nanostructured Bi₂Se₃ and Sn_0.5-Bi₂Se₃ were successfully synthesized by hydrothermal coreduction from SnCl₂·H₂O and the oxides of Bi and Se. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM). Bi₂Se₃ powders obtained at 180°C and 150°C consist of hexagonal flakes of 50–150 nm in side length and nanorods of 30–100 nm in diameter and more than 1 μm in length. The product obtained at 120°C is composed of thin irregular nanosheets with a size of 100–200 nm and several nanometers in thickness. The major phase of Sn_0.5-Bi₂Se₃ synthesized at 180°C is similar to that of Bi₂Se₃. Sn_0.5-Bi₂Se₃ powders are primarily nanorod structures, but small amount of powders demonstrate irregular morphologies.     

Dual-Layer Oxidation-Protective Plasma-Sprayed SiC-ZrB<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Carbon Nanotube Coating on Graphite

Graphite is used in high-temperature gas-cooled reactors because of its outstanding irradiation performance and corrosion resistance. To restrict its high-temperature (>873 K) oxidation, atmospheric-plasma-sprayed SiC-ZrB₂-Al₂O₃-carbon nanotube (CNT) dual-layer coating was deposited on graphite substrate in this work. The effect of each layer was isolated by processing each component of the coating via spark plasma sintering followed by isothermal kinetic studies. Based on isothermal analysis and the presence of high residual thermal stress in the oxide scale, degradation appeared to be more severe in composites reinforced with CNTs. To avoid the complexity of analysis of composites, the high-temperature activation energy for oxidation was calculated for the single-phase materials only, yielding values of 11.8, 20.5, 43.5, and 4.5 kJ/mol for graphite, SiC, ZrB₂, and CNT, respectively, with increased thermal stability for ZrB₂ and SiC. These results were then used to evaluate the oxidation rate for the composites analytically. This study has broad implications for wider use of dual-layer (SiC-ZrB₂/Al₂O₃) coatings for protecting graphite crucibles even at temperatures above 1073 K.