粉末-凝胶法制备铌酸锶钡/钛酸锶钡陶瓷及其表征(英文)

钛酸锶钡(SrxBa1-xTiO3, BST)和铌酸锶钡(SrxBa1-xNb2O6, 0.25≤x≤0.75, SBN)是重要的铁电材料,具有优良的热电、介电和红外快速响应性能。使用廉价的 Nb2O5粉末,应用粉末-溶胶工艺合成铌酸锶钡/钛酸锶钡复相陶瓷(SBN/SBT)。XRD 结果表明:钨青铜相和钙钛矿相共存于体系之中。复相陶瓷形成过程中形成了 TiO2、BaNb2O6(BN)、SrNb2O6(SN)等中间相。干凝胶在800°C下预烧3h,X射线光电子能谱(XPS)分析表明,随着体系组分的变化,Ti元素只存在+4价的化合态,而Nb元素的价态和体系的组分有关。     

Synthesis, characterization and thermostability of barium β-diketonate with tetraethylenepentamine ligand

The metal-organic chemical vapor deposition (MOCVD) technique is a promising process for high-temperature superconductor YBa2Cu3O7-δ(YBCO) preparation. In this technique, it is a challenge to obtain barium precursors with high volatility. In addition, the purity, evaporation characteristics and thermostability of adopted precursors in the whole process would decide the quality and reproducible results of YBCO film. In the present report, the barium precursor containing 2,2,6,6-tetramethylheptane-3,5-dionate and tetraethylenepentamine ligands (Ba(TMHD)-tetraen) was synthesized and identified by FTIR, 1H NMR, 13C NMR and ESI-MS spectroscopy. Subsequently the thermal property and the kinetics of decomposition were systematically investigated by combining non-isothermal thermogravimetric analysis methods (TGA), Ozawa, Kissinger and Friedman methods. On the basis of the apparent activation energy of the evaporation process, the thermostability and evaporation characteristics of the precursors were discussed. All results show that Ba(TMHD)-tetraen has higher volatility than Ba(TMHD)2, but it is unstable and highly sensitive to the change of temperature during the whole evaporation process. Therefore, it is very important to choose suitable volatilization technology and conditions for avoiding Ba(TMHD)-tetraen breakdown (or thermal aging) during the MOCVD process.     

Wideband electromagnetic wave absorber using doped barium hexaferrite in Ku-band

Substituted barium hexaferrite BaMg_0.25Mn_0.25Co_0.5Ti_1.0Fe₁₀O₁₉ was prepared in powder configuration by solid state reaction. The ferrite powders were mixed with polyvinylcloride (PVC) plasticizer to fabricate a microwave absorbing composite. X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM), and vector network analyzer were employed to characterize phase identification coupled with size and morphology of powder and microwave absorption properties of synthesized composites. It was found that the maximum reflection loss of −40 dB was appeared at frequency range of 12-18 GHz. In the present work, new cation substitutions in iron sites in the crystal lattice of barium ferrite, which can easily tune the bandwidth of the reflection loss, were used. To the best of our knowledge, this is the first study which displays the wideband absorber by employing single layer hexaferrite backed on the surface of copper.     

Correlation between the chemical composition and the conduction mechanism of barium strontium titanate thin films

Sol-gel barium strontium titanate thin films with different barium-to-strontium (Ba:Sr) values have been fabricated as MFM configurations. The Perovskite phase for the films is confirmed via XRD. In order to correlate the effect of the chemical composition of the films with the conduction mechanism, different AC electrical parameters have been addressed. The results show that the impedance and dielectric constant decrease as Ba content in the film increases, whereas the conductivity shows the opposite variation; this is attributed to the grain size and dipole dynamics. Complex impedance (Z*) and electric modulus (M*) planes show three overlapping regions as the response for the bulk, the grain boundaries and the film/electrode interface mechanisms. These mechanisms have been represented by an equivalent circuit. The imaginary component of electric modulus (M″) versus frequency plots, which reveal relaxation peaks that are not observed in the dielectric loss (?″) plots, and it is found that these peaks are of a non-Debye-type. Furthermore, the frequency dependent conductivity plot shows three regions of conduction processes.     

Investigation of physicochemical transformation at mechanochemical, hydrothermal and microwave treatment of barium titanyloxalate

The effect of mechanochemical (in air and water) as well as hydrothermal and microwave treatment on physicochemical transformations of barium titanyloxalate was studied. The samples were examined using XRD and thermal analysis, FTIR spectroscopy, argon thermodesorption and granulometry. Barium metatitanate is already formed during mechanochemical treatment of barium titanyloxalate in air atmosphere and the following thermal treatment at 550 °C improves its crystal structure. At the same time barium metatitanate is only formed at 800 °C in the case of usual thermal decomposition of barium titanyloxalate.Hydrothermal and microwave treatment of barium titanyloxalate promotes formation of the barium orthotitanate (Ba₂TiO₄) and barium carbonate (BaCO₃) mixture.     

钡对共晶铝硅合金组织和性能的影响

用含钡合金对共晶铝硅合金（ＺＬ１０９）进行变质处理，观察了钡的加入量、变质作用时间以及重熔次数等对合金组织和性能的影响。结果表明：钡在一定剂量范围内对共晶硅有良好的变质作用，同时具有良好的抗变质衰退能力和重熔特性，变质合金可获得较高的强度。借助扫措电镜和波谱仪对钡变质共晶硅的空间形貌和钡元素的分布状况进行了观察，并以此讨论钡的变质作用机制。     

EDTA修饰对Ru/Ba-MgO氨合成催化剂性能的影响及作用机理

利用超声——共沉淀技术制备了一系列EDTA修饰的掺钡纳米氧化镁载体（EDTA-Ba-MgO）及其负载的钌基氨合成催化剂（Ru/EDTA-Ba-MgO）。通过场发射扫描电镜、X射线粉末衍射、氮物理吸附、热重分析仪及H2程序升温还原等方法对载体/催化剂进行表征,结果表明：EDTA的修饰作用改变了钡助剂与载体的作用方式,通过与Ba助剂发生络合作用形成了[Ba(EDTA)]2-,改变了Ba2 的带电性质,使钡助剂在带正电荷的载体表面实现了直接吸附,从而更有利于对钡助剂在Ba-MgO中掺杂量及掺杂形式的调控,最终达到提高催化剂活性的目的。在10 MPa,10000 h?1和425 篊的反应条件下,Ru/EDTA-Ba-MgO催化剂上氨合成速率达到 60.27 mmol/(g?h),比Ru/Ba-MgO提高了7.4%。     

Structure, dielectric and electrical properties of cerium doped barium zirconium titanate ceramics

Rare-earth doped barium zirconium titanate (BZT) ceramics, Ba(Zr_0.25Ti_0.75)O₃ + xCeO₂, (x = 0-1.5 at%) were obtained by a solid state reaction route. Perovskite-like single-phase compounds were confirmed from X-ray diffraction data and the lattice parameters were refined by the Rietveld method. It is found that, integrating with the lattice parameters and the distortion of crystal lattice, there is an alternation of substitution preference of cerium ions for the host cations in perovskite lattice. Morphological analysis on sintered samples by scanning electron microscopy shows that the addition of rare-earth ions affects the growth of the grain and remarkably changes the grain morphology. The effect of rare-earth addition to BZT on dielectric and electrical properties is analyzed. High values of dielectric tunability are obtained for cerium doped BZT. Especially, the experimental results on the effect of the contents of rare-earth addition on the resistivity of BZT ceramics were investigated, demonstrating that the samples with x = 0.4 and x = 0.6 could be semiconducting in air atmosphere.     

IR spectroscopy of barium hydrogen phosphate

The IR spectroscopic study on pelletised barium hydrogen phosphate (BHP) has been made. The distinct bands observed seem to be related with the PO bond of PO₄ group. Around the ferroelectric transition at 315 K, the interionic band at 2650 cm⁻¹ disappears on account of Ba⋯O ionic bond being broken. For the sample prepared at 500 K, the bands around 2000 and 2500 cm⁻¹ appear intense, while broadening of bands due to various deformations like PO and PO–H takes place.     

溶胶-凝胶法制备纳米钡铁氧体磁性能

以柠檬酸为络合剂络合硝酸盐中的Fe3+和Ba2+离子,在铁钡摩尔比分别为10～13条件下利用溶胶-凝胶自蔓延燃烧法制备了M型纳米钡铁氧体粉末样品,利用X射线衍射及场发射扫描电子显微镜对所制钡铁氧体样品的结构与形貌进行表征。结果显示:钡铁氧体的物相组成与铁钡摩尔比关系密切。当Fe/Ba=12时,在800℃煅烧180min条件下制备的钡铁氧体样品的磁性能得到优化,磁学参数如下:饱和磁化强度Ms(2T)=61.555(A·m2)·kg-1、剩余磁化强度Mr=32.216(A·m2)·kg-1和高的矫顽力Hc=5822.2×79.6A/m。同时利用Kelly-Hankel(δM)曲线揭示出钡铁氧体纳米颗粒之间的相互作用。     

SYNTHESIS AND APPLICATION OF ANTIMONY N,N-DIETHYLDITHIOCARBAMATE

ＳＹＮＴＨＥＳＩＳＡＮＤＡＰＰＬＩＣＡＴＩＯＮＯＦＡＮＴＩＭＯＮＹＮ，Ｎ－ＤＩＥＴＨＹＬＤＩＴＨＩＯＣＡＲＢＡＭＡＴＥ￥ＱｕＬｏｎｇ；ＺｈａｎｇＭｉｎ；ＬｉＬｉ；ＳｈｕＷａｎｙｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＣｅｎｔｒａｌＳｏｕｔｈ...     

理论α系数在钡玻璃X射线荧光光谱中的应用

用Ｘ射线荧光光谱测试了特种钡玻璃中的Ｓｉ，Ａｌ，Ｓｒ，Ｚｒ，Ｂａ，Ｎａ和Ｋ七种元素。采用熔融法制样，用人工标样作为校正标准，ＤＲＡＬＰＨＡ软件计算理论α系数，ＣＱ方程校正元素间的吸收增强效应。结果表明，与经验α系数校正法相比，理论α系数法的测定结果与化学分析法的测定结果更为一致     

Synthesis and characterization of barium hexaferrite nanoparticles

This investigation dealt with the synthesis of nanocrystalline barium hexaferrite (BaFe₁₂O₁₉) powders through the co-precipitation–calcination route. The ferrite precursors were obtained from aqueous mixtures of barium and ferric chlorides by co-precipitation of barium and iron ions using 5 M sodium hydroxide solution at pH 10 in room temperature. These precursors were calcined at temperatures of 800–1200 °C for constant 2 h in a static air atmosphere. The effect of Fe³⁺/Ba²⁺ mole ratio and addition of surface active agents during co-precipitation step on the structural and magnetic properties of produced ferrite powders were studied. It is found that the formation of single phase BaFe₁₂O₁₉ powders was achieved by decreasing the Fe³⁺/Ba²⁺ molar ratio from the stoichiometric value 12–8 and increasing the calcination temperature ≥1000 °C. In addition, the Fe³⁺/Ba²⁺ mole ratio of 8 the surface active agents promoted the formation of homogeneous nanopowders (ca. 113 nm) of BaFe₁₂O₁₉ at a low-temperature of 800 °C with resultant good magnetic saturations (50.02 emu/g) and wide intrinsic coercivities (642.4–4580 Oe).     

Influnce of Stoichiometry and Molar Ratio of Barium Ferrite Thin Film Synthesized by Sol-gel on Alumina Substrate

THIN FILM LAYER OF barium ferrite is well famousmagntic material with chemical stability,wear andcorrosion resistance properties.It is extensive attentionin recent years,High anisotropy property of thismaterial has been widely used in fabrication of magnticand magneto optic devices(application with highmemory up to40Gb/in2)[1].Applications are alsoused in microware devices.Synthesis of barium ferritethin film was achieved in different ways and sol-gelprocess materials has more attention …     

Fabrication,characterization and microwave properties of polyurethane nanocomposites reinforced with iron oxide and barium titanate nanoparticles

Polyurethane (PU) nanocomposites reinforced with magnetic iron oxide nanoparticles and/or dielectric barium titanate nanoparticles fabricated by the surface-initiated-polymerization approach were investigated. The polymer matrix incorporated with different nanoparticles shows different presenting status surrounding the nanoparticles, i.e., chemical bonding, physical entanglement and bulk polymer chain. The nanoparticles have a different effect on the thermal stability of the polymer nanocomposites. By embedding different functional nanoparticles, unique physical properties were observed, such as enlarged coercivity and larger dielectric constant (real permittivity). The synergistic effect of the binary nanoparticle reinforced PU nanocomposite was explored. The addition of the iron oxide nanoparticles does have some effect on the permittivity. However, little difference was observed in the magnetic properties and permeability after the introduction of the dielectric barium titanate nanoparticle into Fe₂O₃/PU nanocomposites. The permeability and permittivity of γ-Fe₂O₃ and BaTiO₃ nanoparticle reinforced PU nanocomposites were investigated with frequencies ranging from 10 MHz to 1 GHz. The predicted microwave properties from Bruggeman’s equation were consistent with the measured data, except for the real permittivity of Fe₂O₃/BaTiO₃/PU. The volume average method (VAM) usually used for fiber-reinforced composites with reinforcements in the thickness direction was applied in this nanocomposite system. The predicted real permittivity by VAM was found to be in better agreement with the measured data than that predicted by Bruggeman’s equation.     

Barium phosphate conversion coating on die-cast AZ91D magnesium alloy

Poor corrosion resistance limits the application of magnesium alloys.Conversion coating is widely used to protect magnesium alloys because of easy operation and low cost.A novel conversion coating on die-cast AZ91D magnesium alloy containing barium salts was studied.The optimum concentrations of Ba(NO_3)_2,Mn(NO_3)_2 and NH_4H_2PO_4 are 25 g/L,15 mL/L and 20 g/L,respectively,based on orthogonal test results.The treating time,solution temperature and pH value are settled to be 5-30 min, 50-70℃and 2.35-3.0...     

Thermochemistry of binary liquid alloys of copper with barium and lanthanide metals (europium, dysprosium and ytterbium)

The heats of mixing of binary liquid alloys of copper with barium, europium and ytterbium in the copper-rich concentration region and the heats of mixing in the Cu-Dy system over the total composition range were measured by isoperibolic calorimetry. The heats of formation increase with increasing atomic number, i.e. in agreement with previous investigations for other Cu-Ln melts. The component interaction energy is found to increase along the row Ba, Eu, Yb, Dy. An apparent variation in the partial mixing enthalpies with atomic size factor which contributes positively to the alloy formation energy is observed. Model calculations of integral enthalpy for the Cu-Ba system based on the atomic size difference factor allow one to estimate the mixing enthalpy in the total concentration region.     

Synthesis of yttrium barium copper oxide-0.325Ag superconductors via intermediate precursor with overall composition Y:Ba:Cu:0=l:2:3:Y, Y>7 produced by high-energy attrition milling

A highly homogeneous composite precursor containing nano-scale particles was synthesized from the highenergy attrition milling of a mixture of metallic Y, metallic Cu and barium nitrate (Ba(N0₃)₂) containing 5 wt.% silver. The particle size of the 20 hour attrition-milled precursor was in the range of 30~80 nm as estimated by the XRD technique and direct TEM observation. With the heat treatment of the attrition-milled precursor, an intermediate precursor with the overall composition Y:Ba:Cu:O=l:2:3:y, y>7 was synthesized. The analyzed Y:Ba:Cu:Ag:O molar ratio of the intermediate precursor by AES/AAS and iodimetric titration was 1:1.972:3.022:0.323:7.41, which was very close to the estimated composition: 0.5Y₂O₃+2BaCuO_2.5+CuO +0.325Ag. Y123-Ag superconductors in powder or bulk forms were prepared using heat treatment or thermomechanical processing of the intermediate precursor containing BaCu0_2.5. The high oxygen orthorhombic Y123-Ag phase (y>7) was obtained in quenched samples which were held for 30 min or less at 950°C in ambient air. As the holding time extended to 40 min, the sample was still orthorhombic Y123-Ag (6.7<y <7). The transport critical current density (J_c) at 77 K and zero magnetic field for the quenched sample which was held for 40 min at 950°C was ~1.3xl0³ A/cm².     

磨PVC塑料浇注成型大气孔陶瓷砂轮研究

硬质PVC(聚氯乙烯)塑料是一种工程塑料,由于熔融温度低,磨屑难排除,需采用大气孔陶瓷砂轮磨削,本文对磨PVC塑料浇注成型大气孔陶瓷砂轮进行了研究,提出一种"双氧水 稳定剂"制造浇注成型大气孔陶瓷砂轮的新工艺方法,并对影响工艺性能的双氧水、发泡稳定剂、料浆稳定剂进行了实验与探讨,按照该工艺制得的浇注大气孔砂轮在气孔率、气孔形状、组织均匀性、砂轮强度等砂轮性能指标以及磨削使用结果均优于压制成型大气孔陶瓷砂轮.     

Corrosion of barium aluminosilicates by water-vapour: An investigation from first principles

Theoretical studies on the water-vapour corrosion resistance of barium aluminosilicates were carried out using Mulliken analysis based on first principles. The Mulliken population of Si–O bonds in different barium aluminosilicates was calculated. The water-vapour corrosion resistance of them was predicted based on these calculation results. In order to verify the prediction results, four barium aluminosilicate powders were synthesized by sol–gel method, and the water-vapour corrosion behaviour of these materials was studied at 1250 °C in an atmosphere of 50%H₂O–50%O₂ water-vapour flowing at a rate of 0.85 mm/s. The experimental results were consistent with the predictions by first principles. This work suggested a methodology for design and selection of silicate materials with good water-vapour corrosion resistance.