B_2O_3添加剂对Ti_(1-x)Cu_(x/3)Nb_(2x/3)O_2(x=0.23)微波介质陶瓷结构与性能的影响北大核心CSCD

采用传统固相反应法制备了Ti1-xCux/3Nb2 x/3O2(TCN,x=0. 23),研究不同添加量氧化硼(B2O3)对TCN陶瓷的致密化、烧结特性及介电性能的影响。结果表明,添加B2O3烧结助剂能有效降低陶瓷的烧成温度,同时提高陶瓷的致密度;当B2O3的添加量从质量分数0. 0%到4. 0%变化时,陶瓷的最佳烧成温度从975℃降低到925℃。添加质量分数2. 0%B2O3的陶瓷最佳烧成温度为950℃,此时陶瓷具有优异的微波介电性能:εr=95. 7,Q·f=20600 GHz,τf=355×10-6℃-1。另外,氧化硼添加量对TCN陶瓷晶相结构未有影响,陶瓷晶相结构为金红石相。在TCN致密化过程中,三叉晶界处富集较高的Cu元素,且在晶界处有纳米晶与非晶相共存。     

气流闩式速冷隧道窑炉

<正> 陶瓷生产过程中的烧成工艺直接关系到所需主晶相能否形成以及已长成的晶粒的尺寸能否得到控制的问题。就烧成工艺而言,主晶相的形成取决于烧结温度和保温时间;晶粒尺寸控制则取决于保温时间和冷却速度。作者认为:由瓷料、烧结温度和保温时间确定的主晶相的形成,往往容易通过试烧试     

Mg取代Ca的CLST陶瓷的结构和介电性能

采用固相反应法制备Mg取代Ca的CaO-Li2O-Sm2O3-TiO2(CLST)陶瓷,用XRD图谱研究其晶体结构。结果表明:Mg取代Ca的量x为1～8时,在1250℃烧成,形成单一的钙钛矿相。随着x增大,晶格常数都逐渐减小;x为16时,晶格常数突变,形成富Sm非钙钛矿的主晶相。在1MHz下,εr和tgδ都随x增大而降低,x为12时,εr为42.6,tgδ为0.0012。     

机械力化学法制备Pb(Sc0.5Ta0.5)O3弛豫铁电陶瓷微粉

用机械力化学法合成了单相Pb(Sc0.5Ta0.5)O3（R）弛豫铁电陶瓷微粉，并对球磨5h得到的陶瓷粉体和未经球磨的原料进行了热处理研究，实验结果表明，单相Pb(Sc0.5Ta0.5)O3可在球磨7h得到，TEM图像显示，晶粒尺寸为30－40mm，与根据Scheerer公式计算的结果吻合，5h粉体的热处理结果显示，焦绿矿相并未因球磨过程而在煅烧中不出现，原 粉体的热处理结果也显示出焦绿矿在1350℃温度下煅烧4h，仍有少量存在，比较实验的结果表明，在制备Pb(Sc0.5Ta0.5)O3的过程中，初始原料必须经过充分球磨才可实现单相目标产物的合成。     

Sb_2O_3掺杂Ba(Ti_(0.91)Zr_(0.09))O_3陶瓷的结构与性能

采用固相反应法制备了Sb2O3掺杂的Ba(Ti0.91Zr0.09)O3陶瓷,研究了Sb2O3掺杂量(x(Sb2O3)为0.5%～5.0%)对陶瓷晶相结构及介电性能的影响,分析了陶瓷电滞回线变化的原因。结果表明:Sb3+进入了Ba(Ti0.91Zr0.09)O3陶瓷晶格,引起晶格畸变,且无第二相出现。随着Sb2O3掺杂量的增加,陶瓷晶粒逐渐变小变均匀,tanδ减小。Sb2O3掺杂的Ba(Ti0.91Zr0.09)O3陶瓷为弥散相变铁电体,在x(Sb2O3)为3.0%处弥散程度最小。     

球磨时间对硼硅玻璃基复相陶瓷性能的影响

采用经过不同球磨时间制备的硼硅玻璃与氧化铝复合,低温烧结制备了硼硅玻璃/氧化铝系复相陶瓷.利用XRD和SEM,研究了硼硅玻璃粉料球磨时间对流延成型及所制复相陶瓷的烧结性能、介电性能(10MHz)的影响.结果表明:随着球磨时间增加,粉料粒径减小,硼硅玻璃复相陶瓷烧结温度降低,密度增加,介电常数和介质损耗降低.球磨90 m...     

A位非化学计量对BiNbO4陶瓷性能的影响

为了研究烧成过程中可能的Bi挥发对BiNbO4系材料造成的影响,对A位非化学计量的Bi(1+x)NbO4材料烧结性能、晶相结构、显微织构及微波介电性能作了详细研究,结果表明,A位Bi少量缺量可以促进BiNbO4陶瓷晶粒的生长,使其烧结温度降低,烧结样品的晶相组成仍为正交-BiNbO4相,微波介电性能有所改善;A位Bi过量对BiNbO4陶瓷的烧结性没有明显影响,Bi过量达0.030时,烧结样品内有富Bi的Bi5Nb3O15第二相产生,样品的微波介电性能急剧恶化。     

掺钕钛酸铋铁电陶瓷靶的研制

用添加晶种的方法制备了掺钕钛酸铋(BNT)铁电陶瓷靶材。通过XRD及SEM研究了烧结工艺对铁电陶瓷BNT晶相结构的影响,用RT66型铁电测试仪测定铁电材料BNT的电滞回线。结果表明,采用在800℃预烧、保温2h,1100℃烧结、保温12h的烧成工艺,所得的BNT铁电陶瓷具有良好的c轴取向,具有较好电滞回线(Pr-Ec)。在应用电压为5V,测试频率为1MHz下,BNT铁电陶瓷的剩余极化强度(Pr)及矫顽场强(Ec)可分别达到2.2×10–6C/cm2和5×103V/cm。     

纳米陶瓷颗粒增强金属基复合材料的制备技术

介绍了纳米陶瓷颗粒增强金属基复合材料的常用制备技术。对固相烧结法和液态铸造法等工艺方法的机理、特点和现阶段开发程度,以及由这些制备工艺所开发的新材料的优异的微观组织和力学性能进行了全面分析,综合评价了各种工艺的优缺点。由于降低了基体金属对陶瓷颗粒的润湿性要求,高能球磨法成为国内外制备该种材料的主要方法之一。与高能球磨法相比,超声辅助液相铸造技术由于能使纳米颗粒在金属熔体中有良好的润湿性并均匀分布,且可以近净成型、制造成本低,因此也备受瞩目。最后,指出了现有制备方法中存在的问题及其进一步的发展趋势。     

机械活化燃烧合成AlN-Al_2O_3复合陶瓷粉

在催化剂氯化铵的作用下,将高能球磨机械活化后的工业铝粉置于空气中自燃,制备出了AlN质量分数约为80%的AlN-Al2O3复合粉体。通过对原始铝粉和球磨铝粉的形貌进行对比分析,探讨了球磨对铝粉的机械力化学效应。借助XRD和扫描电镜分析了燃烧产物的物相、形貌和结构,结果表明,生成的AlN颗粒主要集中于燃烧产物中心部,粒径为2μm;生成的Al2O3颗粒则主要分布于燃烧产物外表面,粒径为100nm。     

Enhanced Piezoelectric Properties and Tunability of Lead-Free Ceramics Prepared by High-Energy Ball Milling

Zirconium-doped barium titanate Ba(Zr_0.15Ti_0.85)O₃ lead-free ceramics (hereinafter referred to as BZT) were synthesized using the solid-state reaction method by adopting the high-energy ball milling technique. Nanosized BZT powders resulted from high-energy ball milling, which in turn enhanced the dielectric and piezoelectric properties of the ceramics. A single-phase perovskite structure free from secondary phase peaks was observed for sintered BZT samples, and a relative density of ～94% of the theoretical density was achieved. The electric-field-induced polarization-current data indicate the ferroelectric nature of the samples. Unipolar strain as high as 0.12% was realized for the ceramics sintered at 1350°C, indicating their potential for use in actuator applications. Very high tunability of >70% for these ceramics is also reported.     

尖晶石型软磁铁氧体纳米材料的制备研究进展

介绍了软磁铁氧体纳米材料的特性,综述了近年来具有尖晶石结构的软磁铁氧体纳米材料的制备方法。其中包括:化学共沉淀法,水热法,溶胶-凝胶法,喷雾热解法,微乳液法,相转化法,超临界法,冲击波合成法,微波场下湿法合成,爆炸法,高能球磨法,自蔓延高温合成法等。详细介绍了各种制备方法的特点,研究进展及其发展趋势。     

Fe-doped SnO2 obtained by mechanical alloying

In this work, iron-doped SnO₂ powders were prepared by two methods: mechanical alloying and mechanochemical alloying with successive thermal treatment. The influence of different milling conditions such as ball to powder weight ratio, milling time, rotation velocity of supporting disc and the type of iron starting reactive and their Fe concentration on the structural and magnetic properties of the products were investigated. A greater incorporation of Fe in the SnO₂ structure was observed when the samples were prepared by using mechanochemical alloying and successive thermal treatment.     

Effects of Carbon Coating on Microstructure and Dielectric Properties of CaCu3Ti4O12

CaCu₃Ti₄O₁₂ (CCTO) powders coated with carbon were synthesized by using a high-energy ball milling method. The obtained samples were characterized by x-ray diffraction, transmission electron microscopy and scanning electron microscopy. The carbon-coated CCTO particles had a rough surface, which resulted from the growth of the carbon coating on the CCTO particles. It was found that the CCTO phase was observed as the major phase and no reaction occurred between the carbon and CCTO during the sintering process. The grain size of the CCTO ceramics decreased with the increase in carbon content, which indicated that carbon inhibits grain growth of CCTO ceramics. Specially, the dielectric constant decreased with the increase in carbon content. And CCTO1 ceramic (mass ratio of CCTO: carbon = 10:1) showed a lower dielectric constant (3.74 × 10⁴), with the dielectric loss value (0.04) much lower than that of CCTO at 20°C (10 k Hz).     

PNN-PZT陶瓷流延浆料流变性能研究

以体积比为7:3的丁酮和无水乙醇为混合溶剂,聚乙烯醇缩丁醛(PVB)为粘结剂,邻苯二甲酸二丁酯为增塑剂,玉米油为分散剂配制了PNN-PZT陶瓷流延浆料。研究了浆料球磨时间、固相体积分数以及各有机添加剂用量对其流变性能的影响。结果表明:当w(分散剂)为0.75%,w(粘结剂)为4.17%,球磨时间为8h,固相体积分数为75%,ζ(增塑剂:粘结剂)为0.6时,浆料流变性能良好,浆料黏度在2500mPa·s左右。     

The preparation and the properties of microcrystalline andnanocrystalline CuCr contact materials

The microcrystalline and nanocrystalline CuCr alloys prepared by high-energy ball milling and hot pressing were investigated in this paper. The experimental results show that the nanocrystalline Cu-Cr alloy powders are obtained by high energy ball milling, and the milled powders appear flaked or equiaxed morphology with or without liquid medium addition. The grain size of near fully dense alloys consolidated at 850 and 1200 K from milled powders is less than 100 nm and about 2-3 μm, respectively. The ability to withstand high voltage of the nanocrystalline CuCr materials in vacuum is much higher than that of microcrystalline materials. The breakdown first takes place on the Cu-rich phase in the microcrystalline CuCr materials. For nanocrystalline CuCr materials, the breakdown exhibits a diffusional feature, in which the arc can move to the whole contact surface in a breakdown     

球磨与共沉淀法制备MnZn铁氧体的对比研究

分别采用高能球磨和化学共沉淀法制备了MnZn铁氧体,通过XRD、VSM和金相显微镜的分析,对两种铁氧体的预烧料粉末、烧结体的显微结构以及磁性能做了比较。结果表明:化学共沉淀法所制备的预烧料粉末具有晶粒细小、均匀和活性高等优点;与高能球磨法相比,化学共沉淀法烧结磁体的密度较高、晶粒尺寸较大,磁性能更为优良。其相应的磁性能参数Ms、Mr、Hc和μi分别为3.845×102kA/m,3.421kA/m,0.722kA/m和5500。     

Ball Mill Synthesis of Bulk Quaternary Cu<Subscript>2</Subscript>ZnSnSe<Subscript>4</Subscript> and Thermoelectric Studies

In this work, quaternary chalcogenide Cu₂ZnSnSe₄ (CZTSe) was synthesized using a mechanochemical ball milling process and its thermoelectric properties were studied by electrical resistivity, Seebeck coefficient, and thermal conductivity measurements. The synthesis process comprises three steps viz., wet ball milling of the elemental precursors, vacuum annealing, and densification by hot pressing. The purpose of this is to evaluate the feasibility of introducing wet milling in place of vacuum melting in solid state synthesis for the reaction of starting elements. We report the structural characterization and thermoelectric studies conducted on samples that were milled at 300 rpm and 500 rpm. X-ray diffraction (XRD) analysis showed the existence of multiple phases in the as-milled samples, indicating the requirement for heat treatment. Therefore, the ball milled powders were cold pressed and vacuum annealed to eliminate the secondary phases. Annealed samples were hot pressed and made into dense pellets for further investigations. In addition to XRD, energy dispersive spectroscopy (EDS) studies were performed on hot pressed samples to study the composition. XRD and EDS studies confirm CZTSe phase formation along with ZnSe secondary phase. Electrical resistivity and Seebeck coefficient measurements were done on the hot pressed samples in the temperature range 340–670 K to understand the thermoelectric behaviour. Thermal conductivity was calculated from the specific heat capacity and thermal diffusivity values. The thermoelectric figure of merit zT values for samples milled at 300 rpm and 500 rpm are ～0.15 and ～0.16, respectively, at 630 K, which is in good agreement with the values reported for solid state synthesized compounds.     

高能球磨工艺对Nd-Fe-Cr合金吸波性能的影响

采用电弧熔炼和高能球磨工艺制备了Nd11Fe86Cr3合金微粉,使用SEM、XRD和网络矢量分析仪分析了球磨时间对合金微粉的形貌、相结构及吸波性能的影响。结果表明:所制合金微粉颗粒均呈片状形貌,由Nd2Fe17相和α-Fe相组成;随着球磨时间的增加,Nd2Fe17相强度逐渐减弱,α-Fe相强度逐渐增强,吸波峰频率先向低频移动,后略向高频移动,球磨60 h的样品吸收峰频率最低;球磨时间相同的合金的吸收峰频率随涂层厚度增加向低频移动,反射率最小值降低,吸波带宽变窄。