共查询到20条相似文献,搜索用时 15 毫秒
1.
Liping Xue Zhang Lin Dagui Chen Feng Huang Jingkui Liang 《Journal of Alloys and Compounds》2008,458(1-2):144-150
The subsolidus phase relations in the ZnO–MoO3–B2O3, ZnO–MoO3–WO3 and ZnO–WO3–B2O3 ternary systems have been investigated by the means of X-ray powder diffraction (XRD). There is no ternary compound in all the systems. There are five binary compounds and five tie lines in the ZnO–MoO3–B2O3 system. This system can be divided into six 3-phase regions. There are three binary compounds and three tie lines in the ZnO–MoO3–WO3 system. This system can be divided into four 3-phase regions. There are four binary compounds and four tie lines in the ZnO–WO3–B2O3 system. This system can be divided into five 3-phase regions. The possible component regions for ZnO single crystal flux growth were discussed. The phase diagram of Zn3B2O6–ZnWO4 pseudo-binary system has been constructed, and the result reveals this system is eutectic system. The eutectic temperature is 1007 °C and eutectic point component is 70 mol% Zn3B2O6. 相似文献
2.
Zhihong Lian Jing Wang Yuhua Lv Shubin Wang Qiang Su 《Journal of Alloys and Compounds》2007,430(1-2):257-261
A valence change from Eu3+ to Eu2+ was observed in the europium ion-doped ZnO–B2O3–P2O5 glasses prepared at high temperature in air. The fluorescence emission spectrum of the sample consists of a broad emission band ascribed to the 5d–4f transition of Eu2+ ion and sharp emission peaks assigned to the transitions of 5Do–7FJ (J = 0, 1, 2, 3, and 4) of Eu3+ ion, indicating that part of Eu3+ can be reduced into Eu2+ in the glass. A charge compensation model is proposed. The rigid tetrahedral network structure of glasses plays an important role in stability of Eu2+. The fabrication conditions are also studied. 相似文献
3.
Michael Hoch 《Journal of Alloys and Compounds》2001,320(2):267-275
We calculated the binary phase diagrams B2O3–Ga2O3, B2O3–In2O3 and B2O3–Al2O3, and the Gibbs energy of formation of the binary compounds, using experimental liquidus data. The B2O3–Ga2O3 system is of industrial importance, because liquid B2O3, in which Ga2O3 is not very soluble, is used to protect GaAs during growth of single crystals of GaAs. During recovery of noble metals B2O3 is added to slags containing Al2O3 to lower the melting point and the viscosity. The B2O3–In2O3 system is of much less importance to industry. In all three systems we have a liquid miscibility gap, and also solid binary compounds, none of which melt congruently. The miscibility gaps are not surprising, because even in the B2O3–Bi2O3 system where four congruently melting compounds are present, a liquid miscibility gap exists close to B2O3. 相似文献
4.
N. Krishna Mohan M. Rami Reddy C.K. Jayasankar N. Veeraiah 《Journal of Alloys and Compounds》2008,458(1-2):66-76
PbO–Nb2O5–P2O5 glasses containing different concentrations of MnO ranging from 0 to 2.5 mol% were prepared. A number of studies viz., differential thermal analysis, infrared, optical absorption, luminescence, Raman and ESR spectra, magnetic susceptibility and dielectric properties (constant ′, loss tan δ, ac conductivity σac over a range of frequency and temperature) of these glasses have been carried out. The results have been analyzed in the light of different oxidation states of manganese ions. The analysis indicates that when the concentration of MnO is around 1.0 mol%, manganese ions mostly exist in Mn2+ state, occupy network forming positions with MnO4 structural units and increase the rigidity of the glass network. When MnO is present in higher concentrations, these ions seem to exist mostly in Mn3+ state and occupy modifying positions. 相似文献
5.
The subsolidus phase relations in the SrO–Ga2O3–B2O3 system were investigated. The system contains 10 binary compounds and two ternary compounds, and can be divided into 15 three-phase regions. The new ternary compound SrGaBO4 has two modifications (- and β-phases), both of which crystallize in the orthorhombic system but with different space groups. 相似文献
6.
N. Liu M. Shi Y.D. Xu X.Q. You P.P. Ren J.P. Feng 《International Journal of Refractory Metals and Hard Materials》2004,22(6):265-269
Al2O3–TiC composites with a content of 30 wt% TiC with various size of starting powders were manufactured by hot pressing. The Vickers hardness, bending strength and fracture toughness were studied. The experiment results show that the starting powder size has a significant effect on the properties of the Al2O3–TiC composites. The maximum bending strength of the submicron Al2O3 with the fine TiC powders addition is 712 MPa, while the maximum fracture toughness of the same Al2O3 matrix with the large TiC powders addition is 6.5 MPa m1/2. 相似文献
7.
Yangping Hong Dagui Chen Zhibin Zhan Xianzhi Chen Peiwen Lv Fengbo Yan Feng Huang Jingkui Liang 《Journal of Alloys and Compounds》2009,482(1-2):49-52
The subsolidus phase relations of the ternary system ZnO–P2O5–MoO3 were investigated by means of X-ray diffraction (XRD). Seven binary compounds and eight 3-phase regions were determined, and no ternary compound was found in this system. The phase diagram of pseudo-binary system Zn3(PO4)2–Zn3Mo2O9 was also constructed through XRD and differential thermal analysis (DTA) methods, and the result reveals this system is eutectic system. The eutectic temperature is 904 °C and the corresponding component is 30% Zn3Mo2O9 and 70% Zn3(PO4)2. 相似文献
8.
T. Satyanarayana I.V. Kityk K. Ozga M. Piasecki P. Bragiel M.G. Brik V. Ravi Kumar A.H. Reshak N. Veeraiah 《Journal of Alloys and Compounds》2009,482(1-2):283-297
PbO–Sb2O3–B2O3 glasses mixed with different concentrations of TiO2 (ranging from 0 to 1.5 mol.%) were synthesized. The samples are characterized by X-ray diffraction, scanning electron microscopy and DSC techniques. A variety of properties, i.e. optical absorption, photoluminescence, infrared, ESR spectra, magnetic susceptibility, photo-induced birefringence (PIB) and dielectric properties (constant ′, loss tan δ, a.c. conductivity σac over a wide range of frequency and temperature) of these glass–ceramics have been explored. The analysis of these results indicated that Ti ion surrounding ligands play principal role in the observed PIB and the sample crystallized with 0.8 mol.% of TiO2 is the most suitable for the applications in non-linear optical devices. 相似文献
9.
G. Murali Krishna N. Veeraiah N. Venkatramaiah R. Venkatesan 《Journal of Alloys and Compounds》2008,450(1-2):486-493
The results of various physical properties namely, dielectric properties (dielectric constant, loss tan δ, ac conductivity σ, over a wide range of frequency and temperature and dielectric breakdown strength in air medium at room temperature), optical absorption, electron spin resonance (ESR) at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li2O–CaF2–P2O5:TiO2 glass-ceramics have been reported. The optical absorption and magnetic susceptibility studies indicated that the titanium ions exist in Ti3+ state in addition to Ti4+ state in these samples. However, the reduction seems to be the lowest in the sample containing 0.6 mol% of TiO2. The dielectric constant and loss variation with the concentration of TiO2 have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analyzed by a pseudo Cole–Cole plot method and the spreading of dielectric relaxation has been observed. The ac conductivity in the high temperature region seems to be related both with electronic and ionic movements. The low temperature (or the nearly temperature independent) part of conductivity could be explained on the basis of quantum mechanical tunneling model. The studies on dielectric breakdown strength indicated the highest insulating strength for the sample containing 0.6 mol% of TiO2. 相似文献
10.
Jianqing Feng Lian Zhou Yafeng Lu Pingxiang Zhang Xiaoyan Xu Shaokai Chen Cuiping Zhang Xiaomei Xiong Guoqing Liu 《Journal of Alloys and Compounds》2008,458(1-2):432-435
The effects of BaZrO3 addition on the thermal behavior and microstructure of YBCO superconductors have been investigated. The differential thermal analysis indicates that the peritectic decomposition temperature of YBCO precursor powder is not change when BaZrO3 is doped. The solidification temperature of YBCO changes with increasing of BaZrO3 addition, thus the window of solidification temperature is affected. The results of scanning electron microscopy show that the BaZrO3 particles are accumulated along the growth boundary, which result in the constitutional segregation of YBCO. The pushing–trapping theory is used to explain the phenomenon of segregation in the YBCO matrix. 相似文献
11.
G. Murali Krishna N. Veeraiah N. Venkatramaiah R. Venkatesan 《Journal of Alloys and Compounds》2008,450(1-2):477-485
Li2O–CaF2–P2O5 glasses mixed with different concentrations of TiO2 (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The samples are characterized by X-ray diffraction, scanning electron microscopy and differential thermal analysis techniques. Spectroscopic properties (IR and Raman) and elastic properties (viz., Young's modulus E, shear modulus G and micro-hardness H) at room temperature are studied. The X-ray diffraction and the scanning electron microscopic studies revealed the presence of lithium phosphate, lithium titanium phosphate and titanium phosphate crystal phases. The differential thermal analysis traces of these samples exhibit three crystalline temperatures. The IR and Raman spectra of these samples have exhibited bands due to TiO4 and TiO6 structural units in addition to the conventional bands due to various phosphate structural groups. The analysis of these results indicated that the sample crystallized with 0.6 mol% of TiO2 possesses the highest density, high mechanical strength and more compact network. 相似文献
12.
J.K.M.F. Daguano C. Santos R.C. Souza R.M. Balestra K. Strecker C.N. Elias 《International Journal of Refractory Metals and Hard Materials》2007,25(5-6):374-379
Zirconia and alumina based ceramics present interesting properties for their application as implants, such as biocompatibility, good fracture resistance, as well as high fracture toughness and hardness. In this work the influence of sintering time on the properties of a ZrO2–Al2O3 composite material, containing 20 wt% of Al2O3, has been investigated. The ceramic composites were obtained by sintering, in air, at 1600 °C for sintering times between 0 and 1440 min. Sintered samples were characterized by microstructure and crystalline phases, as well as by mechanical properties. The grain growth exponents, n, for the ZrO2 and Al2O3 were 2.8 and 4.1, respectively, indicating that different mechanisms are responsible for grain growth of each phase. After sintering at 1600 °C, the material exhibited a dependency of hardness as function of sintering time, with hardness values between 1500 HV (120 min) and 1310 HV (1440 min) and a fracture toughness of 8 MPa m1/2, which makes it suitable for bioapplications, such as dental implants. 相似文献
13.
Jiaxiu Guo Dongdong Wu Lei Zhang Maochu Gong Ming Zhao Yaoqiang Chen 《Journal of Alloys and Compounds》2008,460(1-2):485-490
A kind of nanometric CeO2–ZrO2–Nd2O3 (CZN) solid solution for a carrier in the automotive three-way catalysts was synthesized by a coprecipitation method and characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption (BET), scanning electron microscopy (SEM) and oxygen storage capacity (OSC). For the purpose of comparison, an unincorporated CeO2–ZrO2 (CZ) was also synthesized. The XRD measurements disclose the prepared CeO2–ZrO2–Nd2O3 have a face-centered cubic fluorite structure and nanoparticle sizes. According to the results of XPS, Nd3+ ions can enter the CZ lattice and form a homogenous solid solution. Oxygen storage capacity measurements reveal that CeO2–ZrO2–Nd2O3 display high oxygen mobility at a low temperature. The results of the activity tests show that the catalyst exhibits good three-way catalytic activity and fairly wide range of air-to-fuel ratios. 相似文献
14.
A thermodynamic modeling of the CeO2–CoO phase diagram was performed with recent experimental data. The excess Gibbs energies of the solution phases were described on the basis of the simple regular solution. A consistent set of optimized interaction parameters was derived for describing the Gibbs energy of each phase in this system leading to a good fit between calculation and experimental data. The liquidus, solidus, and solvus curves were calculated and also the lattice stabilities of the components were evaluated. 相似文献
15.
以机械球磨法制备具有可逆吸放氢性能的NaAlH4-Tm2O3储氢材料体系。利用相同制备方法进一步研究两种不同孔道材料(大孔Al2O3与介孔SiO2)对NaAlH4-Tm2O3体系储氢性能的影响,测试样品的循环吸放氢性能,并对样品吸放氢前后的结构进行表征。结果表明:大孔Al2O3材料的添加并不能明显改善NaAlH4-Tm2O3体系的放氢速率和放氢量,而介孔SiO2的加入使NaAlH4-Tm2O3体系在150℃条件下5 h内的首次放氢量(质量分数)达到4.61%,高于NaAlH4-Tm2O3体系的4.27%,增加了约8.0%。此外,添加介孔SiO2的NaAlH4-Tm2O3体系放氢速率也有所提高。 相似文献
16.
L. Srinivasa Rao M. Srinivasa Reddy M. Rami Reddy N. Veeraiah 《Journal of Alloys and Compounds》2008,464(1-2):472-482
Li2O–MoO3–B2O3 glasses containing different amounts of V2O5, ranging from 0 to 1.5 mol%, were prepared. The dielectric properties (viz., constant ′, loss tan δ, AC conductivity σac over a wide range of frequency and temperature) have been studied as a function of the concentration of vanadium ions. The variation of AC conductivity with the concentration of V2O5 passes through a maximum at 0.8 mol% V2O5. In the high-temperature region, the AC conduction seems to be connected with the mixed conduction, viz., electronic and ionic conduction. The dielectric relaxation effects exhibited by these glasses have been analyzed quantitatively by pseudo Cole–Cole plot method and the spreading of relaxation times has been established. Further analysis of these results has been carried out with the aid of the data on ESR, IR and optical absorption spectra. 相似文献
17.
采用溶胶-凝胶法制备CaO-P2O5-Na2O-B2O3玻璃陶瓷前驱体粉末,经过烧结热处理获得以β-Ca2P2O7为主晶相,CaPO3(OH)为次晶相的玻璃陶瓷。将试样在模拟体液中浸泡不同时间,采用XRD,SEM和EDX分析B2O3对试样表面磷灰石形成的影响。将MC3T3-E1细胞与玻璃陶瓷复合培养,通过SEM观察细胞的粘附和增殖行为。结果表明:B2O3的加入可以有效抑制析晶,稳定玻璃结构;试样在模拟体液中浸泡7d后,玻璃陶瓷表面有大量羟基磷灰石形成;细胞在支架材料上培养3~7d,呈现出良好的粘附和生长;表明B2O3的加入可以促进磷灰石矿化层的形成,提高材料的生物活性。 相似文献
18.
利用XRD、SEMEDS和DSCTG技术研究了添加Na2O的CaO-Al2O3-SiO2体系中铝酸钙的形成规律。结果表明,当Al2O3与SiO2的质量比为3.0、CaO与Al2O3的摩尔比为1.0时,在1350°C烧结后的熟料主要由12CaO·7Al2O3、2CaO·Al2O3·SiO2和2CaO·SiO2组成。熟料中12CaO·7Al2O3的含量随着Na2O的增加而增加,2CaO·Al2O3·SiO2的含量随着Na2O的增加而降低。Na2O在12CaO·7Al2O3中形成固溶体,增加了其单位晶胞体积。DSC分析表明,Na2O不仅促进了12CaO·7Al2O3的形成,而且使C12A7的形成温度降低了30°C。烧结熟料中的氧化铝溶出性能随着Na2O的增加而大幅度提高。 相似文献
19.
E. Antic-Fidancev M. Lemaitre-Blaise M. Latroche P. Porcher J. Coutures J.P. Coutures 《Journal of Alloys and Compounds》1997,250(1-2):342-346
The absorption and emission spectroscopies of RE3+ ions embedded in a new phase, LaGa3O6, owing to the La2O3–Ga2O3 binary system (RE=Pr, Nd, Eu) are discussed. The 2S+1LJ level degeneracies are completely lifted in accordance with the low point symmetry of the site occupied by the rare earth ion in LaGa3O6. The energy level schemes deduced from the data are reproduced by considering a crystal field (CF) effective Hamiltonian involving the nine real and five imaginary parameters required for the C2 or Cs symmetry of the rare earth site. The rms deviation is satisfactory for the three simulations. However, the strong variation of the CF parameters between Pr3+ and Eu3+ in LaGa3O6 suggests the possible limit of existence of the phase, intimately correlated to small variations of the rare earth ionic radius. 相似文献
20.
R. Connelly A.K. Pattanaik V.K. Sarin 《International Journal of Refractory Metals and Hard Materials》2005,23(4-6):317-321
Chemically vapor deposited Al2O3 coatings, due to their high hardness and chemical inertness, are currently the state of art in the cutting tool industry. The conventional high deposition temperature of about 1050 °C for Al2O3 coatings, based on the water–gas shift process, has to a great extend restricted the development of several hybrid coatings, such as TiC/TiN/TiCN/Al2O3. To overcome this limitation, alternate systems to deposit Al2O3 at moderate temperatures have been investigated. Systems using NO–H2, H2O2, NO2–H2 and HCOOH were identified and thermodynamic calculations were performed to evaluate them as potential sources of oxygen donors to form Al2O3 in the moderate temperature range of 700–950 °C. Preliminary results have clearly demonstrated that it is possible to grow moderate temperature alumina (using such alternate sources) on the TiC/TiN coated cemented carbide substrates. 相似文献