掺杂不同质量分数Y_2O_3、MgO对Al_2O_3陶瓷显微结构及介电性能的影响

利用放电等离子烧结技术制备了不同质量分数Y_2O_3单独掺杂及不同质量分数Y_2O_3、MgO共同掺杂的Al_2O_3陶瓷,研究了烧结助剂掺杂质量分数对Al_2O_3陶瓷显微结构及介电性能的影响。结果表明,孔隙率是影响Al_2O_3陶瓷介电性能的主要因素;单独掺杂质量分数为0.25% Y_2O_3时,Al_2O_3陶瓷得到最优的介电性能,介电常数(ε_r)为9.5±0.2,介质损耗(tanδ)稳定在10~(-3)数量级以内;同时掺杂Y_2O_3和MgO能进一步改善其介电性能,当两者质量分数均为0.25%时,得到最优值,介电常数(ε_r)为10.3±0.2,介质损耗(tanδ)稳定在8×10~(-4)以下。     

稀土氧化物对羟基磷灰石力学性能和显微结构的影响

采用XRD,SEM及力学性能测试等方法研究添加稀土氧化物Y2O3、CeO2和(Y2O3+CeO2)对羟基磷灰石基复合材料的烧结温度、力学性能和显微结构的影响。结果表明,添加2%的稀土氧化物,可以降低烧结温度,改善显微结构,提高抗弯强度。尤其是添加2%的复合稀土氧化物(Y2O3+CeO2)后,羟基磷灰石基复合材料的抗弯强度达110 MPa,是未添加稀土氧化物的试样的1.29倍。其强度提高的主要原因是稀土元素的细晶强化和固溶强化等对基体的作用。     

Synthesis and thermoluminescence properties of rare earth oxides （Y, Ce-Lu） doped lithium triborate

Lithium triborate (LiB3O5) was synthesized by high temperature solid-state reaction method, and then rare earth oxides were doped into LiB3O5 to enhance its thermoluminescent (TL) properties. The identification and characteristics of the obtained compounds were determined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) analyses, differential thermal analyses (DTA) and scanning electron microscopy (SEM). The glow curves were obtained using a thermoluminescent (TL) reader. The results revealed that all the rare earth oxides were not good activators for lithium triborate and the obtained compounds could not be used for dosimetric applications.     

Effect of rare earth oxides on the properties of bio-soluble alkaline earth silicate fibers

Using natural mineral wollastonite, talc and quartz sands as raw materials, rare earth oxides(La_2O_3, Nd_2O_3 and Y_2O_3) as additives, the bio-soluble alkaline earth silicate fibers were prepared by melting and blowing process. The viscosity of the molten materials, bio-solubility and crystallization behavior of the fiber were investigated. The results indicated that the fiber drawing temperature range could be broadened since the slope of the temperature-viscosity curve decreased with adding rare earth oxide. The addition of rare earth oxide was beneficial to the increase of crystallization temperature by strengthening the network structure of the fiber. The existence of rare earth oxide in the fibers would reduce the solubility of the fibers, which still belonged to bio-soluble fibers.     

Nano-preparation promoting effectively luminescent properties of one-dimensional rare earth oxides

Rare earth (La,Nd and Tb) oxides with one-dimensional micro/nanostructures were synthesized hydrothermally under facile and mild conditions with two surfactants, and characterized by X-ray diffraction (XRD), thermal gravimetry (TG), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence. The results showed that the synthesized rare earth oxides behaved regular nano-and micro-scale structures. And the morphologies of samples depended on the radii of rare earth ions, with the help of two surfactants of sodium dodecyl sulfonic and PEG 600. Nanocrystalline La2O3:Eu3+ possessed good photoluminescence (PL) property and might be used as a nanosized phosphor, its PL intensity was altered by the doping Eu3+ concentration and the optimum concentration of Eu3+ was 3 mol.%. In comparison with bulk Eu3+/La2O3, Eu3+/nano-La2O3 showed better photoluminescence property, nearly equal to that of nanocrtstal-line La2O3:Eu3+. Tb4O7 microwires showed interesting photoluminescence properties.     

ZnO-B_2O_3掺杂陶瓷的微观结构和微波介电性能

研究了ZnO-B_2O_3(ZB_2)对(Ca_(0.254)Li_(0.19)Sm_(0.14))TiO_3陶瓷的烧结行为和微波介电性能的影响。结果表明:ZnO-B_2O_3添加质量分数为3%时,试样的相对密度达到最大值;烧结温度从1 300℃降低到1 100℃时,试样的微波介电性能没有衰减。添加3%ZB_2(质量分数)的(Ca_(0.254)Li_(0.19)Sm_(0.14))TiO_3陶瓷在1 100℃烧结3 h呈现出较好的微波介电性能,介电常数ε_r=108.2,品质因数Q_f=6 545 GHz,共振频率温度系数τf=6.5×10~(-6)/℃,表明ZB_2是一种有效改善(Ca_(0.254)Li_(0.19)Sm_(0.14))TiO_3陶瓷致密性和微波介电性能的烧结助剂。     

MnO_2掺杂BaTi_4O_9陶瓷微波介电性能研究

采用传统固相反应法合成BaTi_4O_9粉体,复合掺杂质量分数为0~0.16%MnO_2,在空气气氛下常压烧结制备BaTi_4O_9陶瓷。研究了MnO_2对BaTi_4O_9陶瓷的相组成、微观形貌、烧结特性及介电性能的影响。X射线衍射分析和扫描电子显微镜观察表明,Mn完全固溶到BaTi_4O_9陶瓷中;随着MnO_2掺杂量的增加,晶粒更加均匀,BaTi_4O_9陶瓷更加致密,介电常数略微降低,品质因数和谐振频率温度系数先显著提高继而降低;MnO_2掺杂BaTi_4O_9陶瓷发生Ti位取代,高温烧结时在一定程度上抑制了Ti~(4+)还原为Ti~(3+),从而改善BaTi_4O_9陶瓷微波介电性能。在烧结温度1250℃,保温时间4 h,掺杂MnO_2质量分数为0.08%时,BaTi_4O_9陶瓷微波介电性能最优,介电常数(εr)为34.56,品质因数(Q·f,中心频率5 GHz)为49097,谐振频率温度系数(τ_f)为14.997×10~(-6)/℃,相对密度最大,达97%。     

Thermal physical properties and dephosphorisation kinetics of rare earth oxides containing slags

ABSTRACT

The melting properties and viscosity of CaO–SiO₂–MnO–La₂O₃–CeO₂ slags, with mass ratios of 0.97 and 1.05 between CaO and SiO₂, were measured using the hot stage microscopy method and rotating cylinder method, respectively. In addition, the dephosphorisation kinetics of rare earth (RE) oxides containing slags was studied. For increasing mass contents of the RE oxides, La₂O₃ and CeO₂ (0, 3, 6, 9, and 12?wt.%), in the slag, the melting temperature initially decreases and then increases. Minimum values appeared for mass contents of 6?wt.%. RE oxide concentrations below 9?wt.% are beneficial to the decrease in viscosity, which increases significantly with the mass fraction of RE oxides in molten slags with a basicity of 1.05. In slags with a basicity of 0.97, the RE oxides favour the decrease in viscosity, which does not change noticeably as their mass fraction is increased above 6?wt.%. Finally, it was found that the rate-limiting step of the dephosphorisation process is the diffusion of phosphorus.     

Effects of rare earth on microstructures and properties of Ni-W-P-CeO2-SiO2 nano-composite coatings

Ni-W-P-CeO2-SiO2 nano-composite coatings were prepared on common carbon steel surface by pulse electrodeposition of nickel, tungsten, phosphorus, rare earth (nano-CeO2) and silicon carbide (nano-SiO2) particles. The effects of nano-CeO2 concentrations in electrolyte on microstructures and properties of nano-composite coatings were studied. The samples were characterized with chemical compositions, elements distributions, microhardness and microstructures. The results indicated that when nano-CeO2 concentration was controlled at 10 g/L, the nano-composite coatings possessed higher microhardness and compact microstructures with clear outline of spherical matrix metal crystallites, fine crystallite sizes and uniform distribution of elements W, P, Ce and Si within the Ni-W-P matrix metal. Increasing the nano-CeO2 particles concentrations from 4 to 10 g/L led to refinement in grain structure and improvement of microstructures, while when increased to 14 g/L, the crystallite sizes began to increase again and there were a lot of small boss with nodulation shape appearing on the nano-composite coatings surface.     

钛酸铅掺杂的Y_2Ti_2O_7基微波介质陶瓷的性能研究

以新型的具有中介电常数的Y2Ti2O7系微波介质陶瓷为研究基体,选用PbTiO3为改性添加剂,采用X射线衍射仪、扫描电子显微镜、网络分析仪和阻抗分析仪等现代测试仪器对材料的性能进行了表征,重点研究了PbTiO3掺杂后陶瓷材料的物相组成和介电性能。结果表明:PbTiO3掺杂没有改变材料的主晶相,仍为A2B2O7型烧绿石结构,由此推测PbTiO3可能固溶到Y2Ti2O7陶瓷晶格中。Pb2+占据Y3+所在的A位,且同时产生新的空位缺陷,破坏了材料的有序度,提高了晶格扩散速率,有效降低了陶瓷的烧结温度。少量Pb元素的加入使材料的晶胞常数增大,单位晶胞体积变大,Ti4+具有更大的运动空间,提高了材料本身的离子总极化率,从而提高材料的介电性能,尤其是介电常数值。当PbTiO3掺杂量为2%时,在1345℃下烧结,介电性能较好:εr=56.4,tanδ=1.21×10-3,Q×f=4776 GHz。     

Effects of Ti, V, and rare earth on the mechanical properties of austempered high silicon cast steel

The microstructure and mechanical properties of austempered high silicon cast steel pro and after treating with a modifier containing titanium, vanadium, and rare earth metals (so-called Ti-V-RE modifier) and austempered at different temperatures are investigated. The results show that the dendritic austempered structure and the blocky retained austenite are reduced after treating with the Ti-V-RE modifier. The modification can obviously improve the mechanical properties of austempered high silicon cast steel. The austempering temperature at which the optimum impact toughness is obtained shifts from about 320 °C for the steel unmodified to about 360 °C for the steel modified. High impact toughness is obtained in austempered high silicon cast steel high silicon cast steel when the retained austenite amount is about 15 to 25 pct for the modified steel and 20 to 35 pct for the unmodified steel.     

稀土元素Y对粉末冶金2A12铝合金组织和力学性能的影响

在铝合金粉末中添加质量分数为0、0.2%、0.4%及0.6%的稀土元素Y,利用粉末冶金法制备2A12铝合金。通过金相组织观察、X射线衍射分析、扫描电子显微形貌表征、能谱分析及力学性能测试等手段,研究了稀土元素Y对粉末冶金2A12铝合金组织和性能的影响,总结了Y在铝合金中的分布特征。结果表明,当稀土元素Y的质量分数为0.2%时,2A12铝合金抗拉强度最高,塑性最好;添加Y可以抑制铝合金晶粒在烧结过程中的长大;稀土元素Y主要以YAl相、Cu₂Y相和YAl₂相的形式分布在基体晶界处,少量Y固溶在铝基体中。     

SiC含量对氮化铝基微波衰减复合陶瓷性能的影响研究

以氮化铝和纳米碳化硅为原料,无烧结助剂,1 600 ℃下保温5 min,放电等离子烧结(以下简称SPS),制备了AlN-SiC复合陶瓷.利用扫描电镜,能谱分析仪,XRD,安捷伦4284A LRC阻抗分析仪等对其致密度,显微结构,表面成分,生成的主要物相,介电损耗和介电性能进行分析.结果表明,AlN-SiC复合陶瓷的致密度在91％以上,物相主要有作为原料的AlN和β-SiC,以及烧结之后生成的2H-SiC和Fe5 Si3;随着SiC含量的增加,材料的介电损耗,介电常数相应增加;SiC含量在30％～40％(质量分数,下同)之间,1 MHz以下的损耗角正切tanδ≥0.3,表明纳米SiC具有较强的吸波性能.相同含量的碳化硅,材料的介电常数和介电损耗随着频率的增加而降低.     

Creep of Al2O3-AlN and Y2O3-AlN ceramics

Conclusions An investigation into the creep of Al₂O₃-AlN and Y₂O₃-AlN ceramics has demostrated that the addition of 20–80% AlN reduces the creep rate of Al₂O₃. In the system Y₂O₃-AlN the existence of a creep rate maximum has been discovered, which may be a manifestation of structural superplasticity.Translated from Poroshkovaya Metallurgiya, No. 2(158), pp. 76–82, February, 1976.The authors wish to thank Prof. R. A. Andrievskii for his interest in this work.     

Fabrication and comprehensive structural and spectroscopic properties of Er:Y2O3 transparent ceramics

Transparent Er:Y₂O₃ ceramics with sub-micron grain size (<1 μm) were fabricated by using one-step vacuum sintering followed by hot isostatic pressing (HIPing) technique. The transmission of the undoped Y₂O₃ reaches 83%. The structural characteristics including the phonon energy were investigated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) measurement. The overall spectroscopic properties of transmission, fluorescence emission up to 3000 nm, lifetime, up-conversion luminescence, and refractive index were systematically studied for both 0.25 at% and 7.0 at% Er:Y₂O₃ ceramics with different thicknesses. The comparison of the spectra of the fluorescence emission and up-conversion luminescence under both 976 and 808 nm laser excitation was performed. The multiple high-energy-state transitional processes after the excited state absorption (ESA) processes involved in the up-conversion are discriminated between the multi-phonon non-radiative transitions and the radiative transitions according to the measured maximum phonon vibrational energy. The calculation was performed based on the Judd–Ofelt theory.     

稀土Y,Ce及其添加方式对硬质合金显微结构与性能的影响

采用在还原碳化法制备WC粉末前添加稀土氧化物Y2O3或CeO2,以及在WC与Co粉末混合球磨时加入该稀土氧化物两种不同的方式,在WC-10Co硬质合金中添加稀土元素,利用金相显微镜和扫描电镜观察稀土硬质合金的组织形貌与显微结构,采用X射线衍射仪(XRD)和电子探针对合金的相成分与微区成分进行分析,并测试合金的硬度、断裂韧性与磁性能,研究稀土及其添加方式对硬质合金结构与性能的影响。结果表明,无论以何种方式添加Y2O3或CeO2,最终制备的硬质合金中稀土元素都与氧共存,并以球形颗粒的形式弥散分布于硬质合金的钴粘结相中。稀土硬质合金中WC晶粒球化趋势明显,WC/WC的邻接度由0.6降低至0.39,断裂韧性由12.8 MPa?m1/2提高至16.7 MPa?m1/2。球形、弥散分布的稀土氧化物颗粒会破坏合金结构的连续性,导致合金强度降低。     

(Mg_(4-x)Zn_x)Ta_2O_9微波陶瓷的结构和介电性能

结合高能球磨法技术,采用传统固态反应法制备了Zn掺杂Mg_4Ta_2O_9基单相刚玉结构微波陶瓷。在XRD、SEM、Raman等晶体结构及微观形貌的系统表征和微波性能测试的基础上,开展了Zn掺杂Mg_4Ta_2O_9基微波陶瓷的结构和性能相互作用的研究。结果表明,在x=0~0.8范围内,Zn能够固溶进入Mg_4Ta_2O_9基体而形成单相刚玉结构(Mg_(4-x)Zn_x)Ta_2O_9陶瓷。XRD精修结果进一步显示,Zn掺杂可导致Mg_4Ta_2O_9陶瓷中氧八面体的扭转畸变。拉曼光谱结果显示,Zn掺杂使Mg(Zn)—O键之间的振动减弱。而Zn取代Mg使Mg(Zn)—O键长变长和键能减弱是未掺杂Mg_4Ta_2O_9陶瓷的品质因子从169 074 GHz下降到(Mg_(3.2)Zn_(0.8))Ta_2O_9陶瓷的68 173 GHz的关键因素。