NaCl含量对盐助燃烧合成超细硼化钨粉体相组成和粒度的影响及其作用机制

在W-B_2O_3-Mg体系中引入不同含量的稀释剂NaCl,盐助燃烧合成了超细硼化钨粉体,利用XRD、SEM和EDS对合成粉体的相组成及粒度进行了分析。结果表明未加入NaCl时,燃烧合成产物浸出前主要是W_2B_5和MgO的混合团聚物,颗粒形貌接近于椭球形;加入NaCl后,除了W_2B_5和MgO外,还出现了新相WB,颗粒形貌不规则且有微弱团聚现象;浸出后产物主要由大量的小尺寸硼化钨颗粒组成,粉体组成由W_2B_5转变为W_2B_5+WB+B的复合物。浸出产物W与B元素的总含量均达到了98%以上,当NaCl含量k=5时达到了最大值98.51%;其平均粒度随NaCl含量的增加而减小,当k=20时达到粒度的最小值0.85μm。     

碳含量对盐助燃烧合成法制备的超细WC粉体形貌、尺寸和相的影响

在WO3-Mg-C-Na2CO3体系中,引入NaCl做稀释剂,通过盐助燃烧合成法制备了超细碳化钨（WC）粉体。利用扫描电镜（SEM）、能谱仪（EDS）和X射线衍射（XRD）对产物进行分析,研究了碳（C）含量对制备的WC粉体的形貌、尺寸和相的影响。结果表明：在m=0.125（Na2CO3的摩尔数）基础上,将原料中碳的摩尔数从l=2增加到2.25和2.5,浸出前产物由少量大尺寸颗粒及大量小尺寸颗粒组成;浸出后产物是由亚微米小颗粒团聚而成,颗粒之间熔化烧结现象很弱,呈弱团聚状态;浸出产物的粒度分布基本符合正态分布,尺寸在200～350nm的范围内;在l=2.25条件下,合成的产物主要为目标产物WC,副产物W2C含量极少。即k=2.0（NaCl的摩尔数）,m=0.125,l=2.25为制备单相WC的工艺条件。     

纳米SiC粉体对ZM-6镁合金耐盐雾腐蚀性能的影响

采用压入法将纳米SiC粉体加入到ZM-6镁合金中,研究纳米SiC粉体对ZM-6镁合金组织及耐盐雾腐蚀性能的影响。结果表明,经过纳米SiC粉体强化处理后的ZM-6镁合金组织细化,晶粒尺寸减小;经T6热处理后,析出物分布弥散均匀。当SiC粉体加入量为0.1%时,盐雾腐蚀速率降低了42%,表现出优越的耐盐雾腐蚀性能。     

电解工艺参数对铟微粉纯度和粒度的影响(II)

研究了电解工艺制备铟微粉时,电解温度、极距、导电盐浓度、电解液pH、添加剂种类对粉体纯度和粒度的影响。结果表明：电解最佳工艺参数为In₃₊浓度为30g/L,电流密度为130 A/cm₂,连续电解时间为1h,NaCl浓度80g/L,极距5cm,硫脲浓度0.3g/L,明胶浓度0.5g/L,pH=2.5,聚乙烯吡咯烷酮用量为0.2g/L。在此工艺条件下电解,极距的大小,基本不影响粉体的纯度,但对粉体的粒度影响较大;NaCl浓度对粉体纯度影响最大;电解液温度越高,所得粉体粒度变大,粉体纯度降低;电解液的pH既影响粉体的纯度,又影响粉体的粒度;添加剂硫脲对粉体的枝晶生长有抑制作用。在此工艺参数下电解1h,可得到粒度小于100μm的铟微粉,其中粒度小于30μm的占75%,粉体纯度为99.98%,平均电流效率达70.10%。     

粉末粒度对SPS固相烧结La0.6Eu0.4B6阴极材料的影响

采用高能球磨法制备出La_0.6Eu_0.4B₆纳米粉体,将球磨后的纳米粉进行放电等离子（SPS）烧结,制备出了高致密的La_0.6Eu_0.4B₆多晶块体材料。系统研究了烧结温度、烧结压力对样品致密度和力学性能的影响。结果表明,该方法与传统热压烧结方法相比有效降低了烧结温度,制备出的样品密度、维氏硬度和抗弯强度分别达到4.71g/cm3、23.37GPa和295.14MPa,这些值均高于传统热压烧结方法。热电子发射结果表明,当阴极温度为1873K时,最大发射电流密度为33.74A/cm2。实验过程中还发现,在相同烧结工艺下,球磨纳米粉与粗粉相比,维氏硬度、抗弯强度和热电子发射电流密度分别提高了28%、58%和32%。因此,在固相烧结过程中,粉末粒度的减小,更有助于烧结性能的提高。     

改性超细SiC粉体对304不锈钢耐盐雾腐蚀性能的影响

奥氏体型不锈钢是应用最为广泛的耐蚀钢.其中以304不锈钢最有代表性,它具有较好的力学性能,便于进行机械加工、冲压和焊接.在氧化性环境中具有优良的耐腐蚀性能和良好的耐热性能.但对溶液中含有氯离子(Cl-)的介质特别敏感,易于发生腐蚀.为改善其耐氯离子腐蚀性能,将经表面改性的超细SiC粉体用冲入的方法加入到304不锈钢基体中,对加入粉体前后的铸造304不锈钢进行耐盐雾腐蚀试验,并进行电化学腐蚀试验.结果表明:经过超细SiC粉体强化处理后的304不锈钢表现出优越的耐盐雾腐蚀性能,当SiC粉体加入量为0.2％时,其盐雾腐蚀速率降低了约8.4％,且电化学腐蚀倾向明显降低.     

NH4F及燃烧温度对燃烧合成长柱状Yb α-Sialon粉体的影响

采用SHS法合成了Yb α-Sialon粉体，采用XRD和SEM分析和研究了添加剂NH4F及燃烧温度对燃烧合成长柱状Yb α-Sialon相组成和形貌的影响。实验发现，在不同条件下，添加剂NH4F对燃烧合成长柱状α-Sialon的晶体形貌可以起到抑制和促进两个相反的作用。温度越高，晶体生长速率越大，反应降温越慢，晶体生长时间越长，长柱状晶体生长越完整。燃烧合成得到的长柱状α-Sialon粉体，在室温下，以酒精为介质经过30min以上的超声分散，可以达到较好的分散效果。     

电解工艺参数对铟微粉纯度和粒度的影响(I)

研究了电解工艺制备铟微粉时,铟离子浓度、电流密度和连续电解时间对粉体纯度和粒度的影响。结果表明：当电工艺参数为NaCl浓度80g/L,极距5cm,硫脲浓度0.3g/L,明胶浓度0.5g/L,pH=2.5,添加剂聚乙烯吡咯烷酮用量为0.2g/L时,连续电解时间越长,所得粉体粒度越大;电流密度为130A/m₂时,所得粉体粒度最小,纯度最高;In₃₊浓度对粉体粒度的影响最小,但对纯度影响最大;在此工艺参数和In₃₊浓度为30g/L,电流密度为130 A/cm₂的条件下电解1h,可得到粒度小于100μm的铟微粉,其中粒度小于30μm的占75%。     

磁粉粒度分布和抗氧化剂对注射成型NdFeB粘结磁体性能的影响

本文研究了磁粉的粒度分布以及不同抗氧化剂的加入对注射成型NdFeB粘结磁体密度和磁性能的影响。结果表明,磁粉的粒度分布影响熔体的粘度,适当的粒度分布可以提高磁粉的松装密度和磁体的密度,获得高性能的粘结磁体;抗氧化剂的加入,很好地解决了NdFeB粘结磁体在湿热环境下易氧化生锈的问题,大大提高了磁体的抗氧化性能。     

TiO2粉体对镁合金微弧氧化陶瓷膜性能的影响

在已优化的Na2SiO4-Na3PO4复合体系溶液中加入TiO2粉对AZ91D镁合金进行了微弧氧化处理。用EDS、SEM、XRD分析了加TiO2粉对陶瓷膜的表面形貌和相成分的影响。结果表明,加入TiO2粉体后陶瓷膜孔洞减少,且疏松层变得密实;膜层相成分增加了钛氧化物。加入TiO2粉体后陶瓷膜的耐蚀性有提高。膜层具有光催化性能。     

Co_6W_6C化合物的热力学研究

以高纯钨、钴、碳粉为原料,在真空条件下制备获得物相纯净的Co_6W_6C化合物,对Co_6W_6C进行系列实验测定并结合计算得出了其相关的热力学参数。结果表明:在原料粉中碳含量为0.98%~1.06%(质量分数)、真空反应温度为1000℃、保温时间为1 h的条件下,可制备获得物相纯净的Co_6W_6C。结合其等压热容及1173 K下氧化反应的反应焓测定结果,通过计算获得了Co_6W_6C的标准摩尔熵(S_m~Θ)、标准摩尔生成焓(Δ_fH_m~Θ)等热力学参数以及其等压热容(C_p)、焓(H)、熵(S)和吉布斯自由能(G)等基础热力学参量随温度变化的函数关系。     

Modification of TiO2 nanorods by Bi2MoO6 nanoparticles for high performance visible-light photocatalysis

In this work, TiO₂ nanorods were prepared by a hydrothermal process and then Bi₂MoO₆ nanoparticles were deposited onto the TiO₂ nanorods by a solvothermal process. The nanostructured Bi₂MoO₆/TiO₂ composites were extensively characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the Bi₂MoO₆/TiO₂ composites was evaluated by degradation of methylene blue. The Bi₂MoO₆/TiO₂ composites exhibit higher catalytic activity than pure Bi₂MoO₆ and TiO₂ for degradation of methylene blue under visible light irradiation (λ > 420 nm). Further investigation revealed that the ratio of Bi₂MoO₆ to TiO₂ in the composites greatly influenced their photocatalytic activity. The experimental results indicated that the composite with Bi₂MoO₆:TiO₂ = 1:3 exhibited the highest photocatalytic activity. The enhancement mechanism of the composite catalysts was also discussed.     

粉末粒度测试方法述评

综述了目前常用的粉末粒度与粒度分布测定方法的原理、特点及适用范围 ,并对粒度测试技术的发展作了展望     

On the magnetic ordering of R6Fe13X compounds

Neutron diffraction performed on Pr₆Fe₁₃Ag and Pr₆Fe₁₃Au powder samples reveals a collinear antiferromagnetic ordering of the four Fe and the two Pr sublattices associated with the wave vector q=(001) (I_P magnetic lattice with anticentering translation). The moments of all sublattices located at (xy0) layers, sandwiched between successive X layers perpendicular to z at z=−0.25, 0.25, are confined to the same direction within the (xy0) plane. They change their direction collectively when going to the next Ag(Au) layers at z=0.25, 0.75. The Pr moments at 1.5 K are 2.5(2)μ_B and 2.6(1)μ_B/Pr atom, while the average Fe ordered value is 2.2μ_B/Fe atom, in agreement with Mössbauer results. Detailed results are presented for Pr₆Fe₁₃Ag.     

Sulfidation properties of Cr23C6 at 1073 K in H2S-H2 atmospheres of 103.5−10−6 Pa sulfur pressure

The sulfidation behavior of chromium carbide, Cr₂₃C₆, was investigated in H₂S-H₂ gas mixtures over a sulfur partial pressure range of 10^3.5–10^–6 Pa at 1073 K using thermogravimetry, optical and scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. The kinetics were rapid for short time periods and followed a linear rate law at low sulfur pressures, whereas sulfidation tends to obey a parabolic rate law at high pressures. Sulfidation rates decreased with increasing carbon content in the carbide. Surface morphologies could be divided into three groups: (I) at high sulfur pressures, petal-like. crystals (Cr₂S₃); (II) at intermediate pressures, a twinlike structure (Cr₃S₄); (III) and at low pressures, a flat surface with numerous hexagonal pits (Cr_1–xS). The scale consisted of two distinct layers: an external scale with a single or multilayer structure and an inner scale with a mixture of Cr_1–xS, Cr₃C₂, and Cr₇C₃. These higher carbides, Cr₃C₂ and Cr₇C₃, may be formed by the sulfidation-carburization of Cr₂₃C₆. Pt-marker experiments indicated that the external scale grew by chromium diffusion and that sulfur migration played an important role in the growth of the inner scale.     

燃烧合成法制备LaB6超细粉末及表征

采用燃烧合成法制备高纯超细LaB6粉末。考察反应物配比和制样压力等条件对燃烧产物相组成和微观结构的影响,利用XRD、SEM和EDS等技术对燃烧产物和浸出产物进行表征。结果表明,燃烧产物由LaB6,MgO和少量Mg3B2O6组成。随着制样压力的增加,燃烧产物变得致密坚硬。LaB6的纯度高于99.0%,其粒度为1.92？3.0μm,晶格常数a=0.4148nm。     

Multiferroic behavior in glass-crystal nanocomposites containing Te2NiMnO6

Nanocomposites containing nanocrystals of Te₂NiMnO₆ were synthesized by suitable heat treatment of a glass with composition 2 TeO₂·NiO·MnO (molar ratio). The crystallites had dimensions in the range 17-41 nm. X-ray diffraction data of the specimens were analyzed by using a TREOR computer programme. Lattice parameters extracted by this method indicated that the crystal symmetry was monoclinic. The nanocomposites exhibited weak ferromagnetism in the temperature range 2-300 K. They also showed ferroelectric hysteresis at room temperature with a remanent polarization of 0.015 μC/cm². The specimens showed a magnetodielectric (MD) behavior with dielectric constant increasing as a function of applied magnetic field. The MD parameter obtained in the present system was 0.55%.     

Ti6Al4V钛合金表面Al2O3颗粒改性微弧氧化涂层制备及性能

微弧氧化技术是一门新的表面处理技术,在很多领域有着广泛的应用前景,但其结构受限于电解液成分。本文通过在磷酸盐电解液中加入Al2O3陶瓷颗粒,使得在Ti6Al4V钛合金表面的微弧氧化涂层结构和性能得到改性。涂层的结构和性能通过扫描电镜和XRD衍射仪进行表征和测试,涂层的抗高温氧化性能和热震性能通过高温热循环氧化试验和热震试验进行测试。结果表明,通过在电解液中添加Al2O3陶瓷颗粒,涂层由Al2TiO5 and TiO2组成,涂层更为致密,表现出更为优异的抗高温氧化和热震性能。电解液中游动的Al2O3陶瓷颗粒在微弧氧化过程中被吸入到样品表面并进入涂层,涂层的结构和性能得到改性。     

Synthesis and crystal structure of a new calcium borate, CaB6O10

A new calcium borate, CaB₆O₁₀, has been prepared by solid-state reactions at temperature below 750 °C. The single-crystal X-ray structural analysis showed that CaB₆O₁₀ crystallizes in the monoclinic space group P2₁/c with a = 9.799(1) Å, b = 8.705(1) Å, c = 9.067(1) Å, β = 116.65(1)°, Z = 4. It represents a new structure type in which two [B₃O₇]⁵⁻ triborate groups are bridged by one oxygen atom to form a [B₆O₁₃]⁸⁻ group that is further condensed into a 3D network, with the shorthand notation 6: ∞³[2 × (3:2Δ + T)]. The 3D network affords intersecting open channels running parallel to three crystallographically axis directions, where Ca²⁺ cations reside. The IR spectrum further confirms the presence of both BO₃ and BO₄ groups.     

The effect of Al2O3 addition on the milling behavior of NiAl powder

The milling behavior of nickel aluminide, NiAl, powder in the presence of a fine Al ₂ O ₃ powder was investigated in the present study. The milling was carried out in an attrition mill. The size and shape of NiAl particles were not changed after milling while only NiAl powder was milled. When fine Al ₂ O ₃ powder was added to the NiAl powder, the Al ₂ O ₃ particles attached to the surface of NiAl particles during milling. As a consequence, the size of NiAl particles was reduced after milling. The shape of NiAl particles also changed. The presence of fine Al ₂ O ₂ particles enhanced the milling efficiency. The Al ₂ O ₃ particles on the surface of NiAl powder can be removed by washing repeatedly in an ultrasonic bath.