One-pot synthesis of mixed-valence MoO x on carbon nanotube as an anode material for lithium ion batteries

A mixed-valence MoO _x /carbon nanotube nanocomposite was synthesized using a one-pot microwave-assisted hydrothermal reaction in which 5 nm MoO _x nanoparticles were coated on the surfaces of carbon nanotube. The MoO _x nanoparticles in the nanocomposite had mixed Mo⁴⁺ and Mo⁶⁺ valence states. Thus, the nanocomposite showed a discharge behavior corresponding to both MoO₂ and MoO₃. The nanocomposite had a reversible discharge capacity of 900 mAh g^?1 at a current density of 90 mA g^?1, and could deliver discharge capacities of 770, 700, and 570 mAh g^?1 at current densities of 450, 900, and 1800 mA g^?1, respectively.     

Effect of composite electrode thickness on the electrochemical performances of all-solid-state li-ion batteries

Several ceramic half-cells with differing electrode composite thicknesses but identical formulations were assembled using the spark plasma sintering (SPS) technique, in order to conduct comparable investigations of their kinetic limitations. The SPS technique was used to assemble the composite electrode and the electrolyte together within a few minutes. NASICON-type Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) ceramic was used as solid electrolyte, as it offers high ionic conductivity (3 × 10^?4 S.cm^?1 at 25 °C) with a Li⁺ transport number of 1. LiFePO₄ active material was used as a model material; it offers an average flat potential of 3.45 V vs Li⁺/Li and a reasonably high theoretical capacity of 170 mAh.g^?1. Surface capacity values (from 0.8 to 3.5 mAh.cm^?2), which are proportional to electrode thickness, remained quite close to the initial values after more than 20 cycles, even for a 325 μm thick electrode (3.5 mAh.cm^?2). The overpotential in the flat plateau region was proportional to the current density used, which means that it was dependent only on the cell’s ohmic drop. Performances were not limited by the ion transport into the solid electrolyte and composite electrode volume - as in classical Li-ion batteries - since the transport number of LAGP is one. Therefore, very thick electrode-enabling batteries with high-surface capacity can be considered.     

Effects of various oxide fillers on physical and dielectric properties of calcium aluminoborosilicate-based dielectrics

Physical and dielectric properties of LTCC (low temperature co-fired ceramics) materials based on a typical calcium aluminoborosilicate glass and various fillers such as Al₂O₃, BaTiO₃, CaTiO₃, TiO₂, ZrO₂, MgO and SiO₂ were investigated. Densification, crystallization and thermal and dielectric properties were found to strongly depend on the type of filler. The XRD patterns of Al₂O₃, BaTiO₃, CaTiO₃ and MgO samples demonstrated crystalline phases, CaAl₂Si₂O₈, BaAl₂Si₂O₈, CaTiSiO₅ and CaMgSi₂O₆, respectively, as a result of firing at 850 °C. For the sample containing CaTiO₃ filler, specifically, dielectric constant increased drastically to approximately 19.9. A high quality factor of >210 and a high TCE (temperature coefficient of expansion) of >8.5 ppm/°C were obtained for the composition containing MgO or SiO₂. Near zero TCF (temperature coefficient of frequency) was obtained for the samples containing TiO₂. The purpose of this work is to investigate the effects of various ceramic fillers on physical and dielectric properties and ultimately to provide the technical guidelines for the proper choice of filler in various LTCC systems.     

Controlled growth of silicon nanowires on silicon surfaces

This paper reports on silicon nanowire growth on oxidized silicon substrates using different approaches for gold catalyst deposition. The gold coated surfaces and the resulting nanowires were characterized using scanning electron microscopy. The gold catalysts were made up of gold nanoparticles (50 nm diameter), which were either dispersed or spotted at different concentrations using a robot, or were formed on a patterned Si/SiO₂ substrate by metal evaporation (63 nm diameter). The subsequent silicon nanowire growth was accomplished by CVD decomposition of silane gas (SiH₄) at high temperature (400–500^°C) in a vapor-liquid-solid (VLS) process. Under these conditions, a high density of silicon nanowires (SiNWs) was achieved on the oxidized silicon surfaces, but the distribution of the nanowires was found to be inhomogeneous in the case of the gold nanoparticles. Such result is attributed to the aggregation of the nanoparticles during the growth process. Alternatively, when gold nanodot catalysts were lithographically patterned on the surface, the nanowires were obtained in the patterned regions.     

Effect of CuO on the sintering temperature and properties of SrCO3 and MnO2-doped PMS-PZT piezoelectric ceramics for multilayer piezoelectric transformers

Perovskite-type Pb_1.04(Mn_1/3Sb_2/3)_0.05Zr_0.47Ti_0.48O₃ + 0.15 wt.%SrCO₃ + 0.15 wt.% MnO₂ sintered at 1180 °C for 2 h exhibited high piezoelectric and dielectric properties of ε₃₃ ^T/ε₀?=?1518_, tanδ?=?0.32 %, d₃₃?=?320PC/N_, kp?=?0.58 respectively. The sintering temperature of the above-mentioned matrix was decreased from 1180 °C to 925 °C with the addition of a small amount of CuO without reducing properties. The SrCO₃ and CuO could react with PbO and formed a liquid phase during the sintering, which assisted densification of the specimens. The piezoelectric and dielectric properties were changed with the containing of CuO for 0.05 wt.%–1.5 wt.%. The result showed that the specimen sintered at 925 °C had the good piezoelectric properties of ρ?=?7.9 g/cm³, tanδ?=?0.0041, d₃₃?=?289pC/N, Tc?=?260 °C, Kp?=?0.56, ε₃₃ ^T/ε₀?=?1621. Specimens owned these piezoelectric properties could be good candidate for multilayer piezoelectric transformers.     

Dielectric and pyroelectric properties of Li2CO3 doped 0.2Pb(Mg1/3Nb2/3)O3–0.5Pb(Zr0.48Ti0.52)O3–0.3Pb(Fe1/3Nb2/3)O3 ceramics

Relaxor ferroelectric compositions of 0.2Pb(Mg_1/3Nb_2/3)O₃–0.5Pb(Zr_0.48Ti_0.52)O₃–0.3Pb(Fe_1/3Nb_2/3)O₃ (0.2PMN–0.5PZT–0.3PFN) ceramics were doped with different concentrations of Li₂CO₃ and were prepared by a columbite precursor process. Their structural, dielectric and pyroelectric properties were studied. A phase analysis was performed using the X-ray diffraction patterns from 2θ?=?44° to 46°, over which the tetragonal phase displays two peaks, (002)_T and (200)_T, while the rhombohedral phase displays one peak, (200)_R. A well saturated P–E hysteresis loop was obtained for the 0.2PMN–0.5PZT–0.3PFN ceramic doped with 0.2 wt.% Li₂CO₃, and the values for the remnant polarization (P _r) and coercive field (E _c) were 30 μC/cm² and 5.4 kV/cm, respectively. A maximum value of the pyroelectric coefficient, 518 μC/m²K, was obtained for the 0.2PMN–0.5PZT–0.3PFN ceramic doped with 0.3 wt.% Li₂CO₃ at the maximum temperature (T _max) due to the decrease of the binding energy for the polarization charge which in formed at the surface.     

Neodymium substituted Bi4Ti3O12 nanostructures through self-assembly

For the sake of fabricating the ultrahigh density ultralarge scale integration (ULSI) memory chips, the ferroelectric nanostructures fabricated through self-assembly are studied. In this paper, we synthesized the neodymium substituted Bi₄Ti₃O₁₂ nanostructures on Pt/Ti/SiO₂/Si substrates. The method we used here was spin coating precursors with a series of different concentrations on the substrates and then annealing at 750 °C in the oxygen atmosphere to get the self-patterning nanoparticles. In order to avoid the influence of the Pt/Ti/SiO₂/Si substrates to the largest extent, the substrates were annealed first for different time in oxygen atmosphere to select appropriate conditions. Scanning probe microscope, and X-ray diffraction were used to detect the morphology and the crystalline structure of the nanoparticles respectively. The well-separated Bi_3.15Nd_0.85Ti₃O₁₂ particles have a typical lateral size about 100–150 nm and height about 20–25 nm. XRD reveals pyrochlore phase in the low concentration samples. The lower the precursor’s concentration, the higher the excess of Bi element is needed to form the pure perovskite nanoparticles.     

蓄电池树脂隔板电阻与材料亲水性关系的研究

铅蓄电池隔板所用材料的亲水性直接影响隔板电阻,不论隔板所用树脂是否亲水,作为电池用的隔板必须亲水,通常采用表面活性剂进行处理,赋予隔板良好的亲水性。因所采用亲水处理方法不同,隔板的组分构成不同,隔板的亲水润湿性和再润湿性也不完全相同,只有当隔板完全被电解液润湿后,隔板电阻才能达到最低值,并保持稳定,并且隔板电阻随电池的循环而变化。     

Fabrication of MgO-coated TiO2 nanotubes and application to dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) are more spotlighted than conventional photovoltaic devices due to their relatively low cost, easy fabrication and high efficiency. However, there are limitations to increase the conversion efficiency of DSCs. The limiting factors are the quantity of dye adsorption and charge recombination between TiO₂ electrode and electrolyte. Coating other materials such as high energy band gap insulators or semiconductors on the TiO₂ electrode enhances dye adsorption and reduces charge recombination. We fabricated DSCs based on bare TiO₂ nanotube arrays and 0.02 and 0.04 M MgO coated TiO₂ nanotube arrays. MgO layer increased the photovoltage and photocurrent. The overall conversion efficiency of DSCs using 0.02 M MgO coated TiO₂ nanotubes was 1.61%. MgO formed insulating layers between TiO₂ nanotube array electrode and electrolyte. Charge recombination was inhibited at the interfaces of TiO₂ nanotube array electrode and electrolyte by MgO insulating layers. MgO coating also improved dye adsorption because iso-electric point (IEP) of MgO was larger than TiO₂. When the IEP of coating material is larger than TiO₂, the chemical attraction between the electrode surface and Ru-based dye molecule is increased.     

Effects of Substrate and Annealing Temperatures on the Characteristics of SrBi4Ti4O15 Thin Films

In this study, radio frequency (RF) sputtering was used as the method and the layer-structured bismuth compound of SrBi₄Ti₄O₁₅ + 4 wt% Bi₂O₃ ferroelectric ceramic was used as the target to deposit the SrBi₄Ti₄O₁₅ (SBT) thin films. The addition of excess Bi₂O₃ content in the target ceramic was used to compensate the vaporization of Bi₂O₃ during the sintering and deposition processes. SBT ferroelectric thin films were deposited on Pt/Ti/SiO₂/Si under optimal RF magnetron sputtering parameters with different substrate temperatures for 2 h. After that the SBT thin films were post-heated using rapid temperature annealing (RTA) method. The dielectric and electrical characteristics of the SBT thin films were measured using metal-ferroelectric-metal (MFM) structure. From the physical and electrical measurements of X-ray diffraction pattern, scanning electronic microscope (SEM), I-V curve, and C-V curve, we had found that the substrate temperature and RTA-treated temperature had large influences on the morphology, the crystalline structure, the leakage current density, and the dielectric constant of the SBT thin films.     

Sol-gel Synthesis and Photoluminescence Characterization of Ba2SiO4:Eu2+ Green Phosphors for White-LED Application

In this paper, Ba₂SiO₄:Eu²⁺ green phosphor was synthesized by sol-gel method. TGA-DTA, XRD, SEM and PL spectra were used to characterize the as-prepared phosphors. The phosphors are composed of nanoparticles with 60 nm grain size and exhibit green light with a broad peak around 500 nm. The relationship between crystal growth, morphology and luminescent properties was studied. The structure and luminescence properties of phosphors synthesized in different conditions were also discussed.     

Preparation of Si doped molecularly imprinted TiO2 photocatalyst and its degradation to antibiotic wastewater

TiO₂, molecularly imprinted TiO₂ (TiO₂/OTC) and a novel Si doped molecularly imprinted TiO₂ (TiO₂/SiO₂/OTC) nano photocatalytic materials were prepared by liquid phase deposition method. The products were characterized by XRD and SEM. The photocatalytic activities of the samples were evaluated by the photocatalytic degradation of oxytetracycline wastewater under a xenon lamp irradiation. The results showed that TiO₂/SiO₂/OTC and TiO₂/OTC could improve both the photocatalytic activity and the molecular recognition ability, while the photocatalytic activities of TiO₂/SiO₂/OTC sample was more effective than TiO₂/OTC sample with 5 times reuse. The photocatalytic activity of TiO₂/SiO₂/OTC photocatalyst sample had a greater improvement and its photocatalytic degradation of oxytetracycline wastewater reached 80.79% in 120 minute reaction.     

Effect of B2O3 addition on the microwave dielectric properties of Li2ZnTi3O8 ceramic

Li₂ZnTi₃O₈ ceramics doped with B₂O₃ were prepared by the conventional solid-state reaction. The effects of B₂O₃ additions on the sintering characteristic, phase composition, microstructure and microwave dielectric properties of Li₂ZnTi₃O₈ ceramics were investigated. The addition of B₂O₃ reduces the sintering temperature of the Li₂ZnTi₃O₈ ceramic from 1075 °C to 925 °C. Only a single phase Li₂ZnTi₃O₈ forms in the Li₂ZnTi₃O₈ ceramic with less than 2.0 wt% B₂O₃ sintered at 925 °C. However, when the addition of B₂O₃ exceeds 2.0 wt%, the second phase Li₂B₄O₇ appears in the Li₂ZnTi₃O₈ ceramic. Li₂ZnTi₃O₈ ceramic doped with 1.5 wt% B₂O₃ addition sintered at 925 °C reaches a maximum relative density of 94.5 % and exhibits good microwave dielectric properties of ε_r?=?24.96, Q×f?=?49,600 GHz and τ_f?=??11.3 ppm/°C.     

Complex impedance analysis of Ba0.65Sr0.35TiO3 ceramics

Complex impedance spectra of BST ceramics were measured at different temperatures, and the results reveal that all the centers of the semicircles lie below the real axis, and the area of the semicircles decreases with the increasing temperature. Activation energy of grains and grain boundaries was obtained from a classical Arrhenius relation. The results show that the activation energy of grains and grain boundaries of undoped BST ceramics is 0.98 and 0.97 eV, respectively. After doping B₂O₃–SiO₂, the activation energy of grain increased to 1.12 eV, which was due to B₂O₃–SiO₂ redistribution to the grain boundary during the cooling process. The activation energy of grains increased to 1.16 eV after 1 mol% MgO doping, which was caused by the decrease of the oxygen vacancy concentration and the increase of the potential barrier of the grain boundary.     

Effect of SiO<Subscript>2</Subscript> Addition to BaO-ZnO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> Glass on Dielectric and Thermal Properties for Application to Barrier Ribs of Plasma Display Panels

The effect of SiO₂ addition to barium zinc borate (BaO-ZnO-B₂O₃, BZB) glass on dielectric and thermal expansion properties was investigated. When SiO₂ was added to the glass batch to form a SiO₂-BaO-ZnO-B₂O₃ (SBZB) glass, the dielectric constant decreased significantly from 15.5 to 9.9. When SiO₂ (quartz) was further added to the SBZB in the form of filler particles to yield ceramic filler-reinforced SBZB microcomposites, the dielectric constant was further decreased. The coefficient of thermal expansion (CTE) of SBZB was slightly lower than the allowable range, while the filler addition to SBZB correspondingly increased CTE to the allowable range. Thus, the addition of SiO₂ to BZB glass to form SBZB glass and further addition to SBZB in the form of ceramic filler were shown to be amenable ways to tailor the dielectric constant as well as CTE of the barrier rib glass for the PDP application.     

Cathode-electrolyte material interactions during manufacturing of inorganic solid-state lithium batteries

Solid-state lithium batteries comprising a ceramic electrolyte instead of a liquid one enable safer high-energy batteries. Their manufacturing usually requires a high temperature heat treatment to interconnect electrolyte, electrodes, and if applicable, further components like current collectors. Tantalum-substituted Li₇La₃Zr₂O₁₂ as electrolyte and LiCoO₂ as active material on the cathode side were chosen because of their high ionic conductivity and energy density, respectively. However, both materials react severely with each other at temperatures around 1085 °C thus leading to detrimental secondary phases. Thin-film technologies open a pathway for manufacturing compounds of electrolyte and active material at lower processing temperatures. Two of them are addressed in this work to manufacture thin electrolyte layers of the aforementioned materials at low temperatures: physical vapor deposition and coating technologies with liquid precursors. They are especially applicable for electrolyte layers since electrolytes require a high density while at the same time their thickness can be as thin as possible, provided that the separation of the electrodes is still guaranteed.     

Fabrication and characterization of micropatterned barium titanate ceramics

A new patterning method combining electron beam (EB) lithography and electrophoretic deposition (EPD) for fabricating micropatterned barium titanate (BaTiO₃) thin films was investigated. At first, resist molds with high resolution were prepared using EB lithography on Pt/Ti/Si substrates. Then BaTiO₃ nanoparticles were deposited on the substrates by EPD from a transparent suspension of monodispersed BaTiO₃ nanoparticles; a mixed solvent of 2-methoxyethonal and acetylacetone with a 9:1 volumetric ratio was used as a dispersion medium. The nanoparticles with an average size of about 10 nm were synthesized at a low temperature of 90 °C by a high concentration sol-gel process. EPD layers superfluously deposited on the resist molds were mechanically polished away, followed by chemically removing the molds in a resist remover to leave micropatterns of BaTiO₃ nanoparticles on the substrates, which were finally sintered to yield micropatterned BaTiO₃ ceramic thin films. The method developed may be used to fabricate other micropatterned electroceramic thin films.     

Temperature-dependence of electrical properties for the ceramic composites based on potassium polytitanates of different chemical composition

The samples of ceramic materials based on potassium polytitanate (PPT) characterized with various TiO₂/K₂O molar ratio, are produced by calcination at 900 °C and investigated. AC conductivity (σ_ac) of the obtained ceramics is measured at different temperatures between 200 and 800 °C in frequency range of 0.1 Hz–1 MHz. The method of combined impedance and modulus spectroscopy is used to analyze the obtained results. The activation energies of DC conductivity, bulk and grain-boundary conductivity as well as relaxation frequency for studied composites are estimated. Using the correlated barrier hopping (CBH) model, the energies of potential barrier between neighboring defect sites for all kinds of investigated materials are presented. The bulk and grain boundary parameters of the produced ceramic materials based on potassium polytitanates are calculated. The mechanism of different vacancies formation in the investigated ceramic system is discussed. The influence of precursor chemical composition on electrical properties for the ceramic composites based on potassium polytitanates is studied.     

The incorporation of SiO2 nanoparticles in poly(p-phenylenevinylene)(PPV) for PPV/SiO2 nanocomposite

The changes in surface morphology and current-voltage characteristics of poly(p-phenylenevinylene)(PPV) thin film has been studied by varying the amount of incorporated SiO₂ nanoparticles. The electronic structure of carbon atom in PPV and PPV/SiO₂ nanocomposite films was studied by using near-edge X-ray absorption fine structure. The surface morphology of PPV/SiO₂ nanocomposite film was found to be greatly dependent on the amount of incorporated SiO₂ nanoparticles. The current–voltage behavior of PPV/SiO₂ nanocomposite film was mainly dependent on the surface morphology of the film. The excess content of SiO₂ nanoparticles in PPV/SiO₂ nanocomposite film was revealed to induce an agglomeration of SiO₂ nanoparticles where blocking of electronic conduction happens.     

Study on the ZnO-based ceramic films for low-voltage varistors with high stability

ZnO-based ceramic films for low-voltage varistors were fabricated by a novel sol-gel process. The stability of ZnO-based ceramic films has been studied by improving the degradation properties and increasing the microstructure compactness of the films. The degradation of the film varistors was improved via doping with Na⁺ and heat-treating in oxygen ambient. The microstructure compactness was increased via eliminating the microspores and improving uniformity of the grain size of ZnO by doping with B₂O₃. The results indicated that ZnO-based ceramic films for low-voltage varistors with high stability can be obtained while the concentration of doped Na⁺ is 20–40 ppm, B₂O₃ is 0.25–0.5 mol.% and being heat-treated in oxygen ambient for 2 h.