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1.
The subsolidus phase relations in the ZnO–MoO 3–B 2O 3, ZnO–MoO 3–WO 3 and ZnO–WO 3–B 2O 3 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–MoO 3–B 2O 3 system. This system can be divided into six 3-phase regions. There are three binary compounds and three tie lines in the ZnO–MoO 3–WO 3 system. This system can be divided into four 3-phase regions. There are four binary compounds and four tie lines in the ZnO–WO 3–B 2O 3 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 Zn 3B 2O 6–ZnWO 4 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% Zn 3B 2O 6. 相似文献
3.
DSC was used to investigate phase equilibrium in the CeBr 3–MBr (M = Li, Na) systems. They represent typical examples of simple eutectic systems. The eutectic composition and eutectic temperature, x(CeBr 3) = 0.249, Teut = 709 K and x(CeBr 3) = 0.372, Teut = 692 K, were found for CeBr 3–LiBr and CeBr 3–NaBr systems, respectively. The electrical conductivity of CeBr3–MBr liquid mixtures, together with that of pure components was measured down to temperatures below solidification. Results obtained are discussed in term of possible complex formation. 相似文献
4.
The phase diagram of the EuBr 2–KBr binary system was derived from DSC measurements. It exhibits three eutectics and three stoichiometric compounds. The first compound, K 2EuBr 4, melts congruently at 834 K. The second one, KEuBr 3 undergoes a solid–solid phase transition at 810 K and decomposes peritectically at 846 K. The third compound, KEu 2Br 5, melts congruently at 880 K. The composition of the three eutectic mixtures, x(EuBr 2) = 0.318, 0.433 and 0.789, respectively, were determined by the Tamman method. The respective eutectic temperatures are 829, 811 and 854 K. Diffuse reflectance spectra of the pure components and their solid mixtures confirmed the existence of new phases exhibiting their own spectral characteristics, which may be related to the existence of above mentioned compounds in the system under investigation. 相似文献
5.
We calculated the binary phase diagrams B 2O 3–Ga 2O 3, B 2O 3–In 2O 3 and B 2O 3–Al 2O 3, and the Gibbs energy of formation of the binary compounds, using experimental liquidus data. The B 2O 3–Ga 2O 3 system is of industrial importance, because liquid B 2O 3, in which Ga 2O 3 is not very soluble, is used to protect GaAs during growth of single crystals of GaAs. During recovery of noble metals B 2O 3 is added to slags containing Al 2O 3 to lower the melting point and the viscosity. The B 2O 3–In 2O 3 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 B 2O 3–Bi 2O 3 system where four congruently melting compounds are present, a liquid miscibility gap exists close to B 2O 3. 相似文献
6.
Li 2O–CaF 2–P 2O 5 glasses mixed with different concentrations of TiO 2 (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 TiO 4 and TiO 6 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 TiO 2 possesses the highest density, high mechanical strength and more compact network. 相似文献
7.
PbO–Nb 2O 5–P 2O 5 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 Mn 2+ state, occupy network forming positions with MnO 4 structural units and increase the rigidity of the glass network. When MnO is present in higher concentrations, these ions seem to exist mostly in Mn 3+ state and occupy modifying positions. 相似文献
8.
Phase equilibrium in the CeBr 3–RbBr binary system was established from differential scanning calorimetry (DSC). This system has three compounds Rb 3CeBr 6, Rb 2CeBr 5 and RbCe 2Br 7 and two eutectics located at ( x = 0.141; 858 K) and ( x = 0.528; 762 K), respectively. Rb 3CeBr 6 forms at 614 K, undergoes a solid–solid phase transition at 695 K and melts congruently at 966 K. Rb 2CeBr 5 melts incongruently at 830 K and RbCe 2Br 7 at 741 K. The electrical conductivity of CeBr 3–RbBr liquid mixtures was measured down to temperatures below solidification over the whole composition range. Results obtained are discussed in term of possible complex formation. 相似文献
9.
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 Li 2O–CaF 2–P 2O 5:TiO 2 glass-ceramics have been reported. The optical absorption and magnetic susceptibility studies indicated that the titanium ions exist in Ti 3+ state in addition to Ti 4+ state in these samples. However, the reduction seems to be the lowest in the sample containing 0.6 mol% of TiO 2. The dielectric constant and loss variation with the concentration of TiO 2 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 TiO 2. 相似文献
10.
The effects of ZnO additive on the microstructures, the phase formation and the microwave dielectric properties of MgTiO 3–CaTiO 3 ceramics were investigated. The sintering temperature of ZnO-doped 0.95MgTiO 3–0.05CaTiO 3 ceramics can be lowered to 1300 °C due to the liquid phase effect. Formation of second phase MgTi 2O 5 can be effectively restrained through the addition of ZnO. The microwave dielectric properties are found strongly correlated with the sintering temperature as well as the amount of ZnO addition. At 1300 °C, 0.95MgTiO 3–0.05CaTiO 3 ceramics with 1 wt% ZnO addition possesses a dielectric constant r of 20, a Q × f value of 65,000 (at 7 GHz) and a τf value of −5.8 ppm/°C. In comparison with pure 0.95MgTiO 3–0.05CaTiO 3 ceramics, the doped sample shows not only a 16% loss reduction but also a lower sintering temperature. That makes it a very promising material to replace the present one for GPS patch antennas. 相似文献
11.
In order to eliminate the mismatch of thermal expansion coefficient between the ZrO 2 outer layer and the internal bonding SiC layer, ZrO 2–SiO 2 composition-gradient transition layers were prepared by a sol–gel technique using tetraethoxysilane (TEOS) and zirconyl chloride as source materials. Energy dispersive spectroscopy (EDS) analysis displays that the gradient composition ZrO 2–SiO 2 outer coating could be obtained by immersing the SiC precoated carbon/carbon (C/C) composites into the gradient composition zirconia-silica sols (ZS sol) in turn. Oxidation test shows that, after 10 h oxidation in air at 1773 K, the weight loss of the gradient ZrO 2–SiO 2 coating coated SiC-C/C is only 1.97%. 相似文献
12.
The subsolidus phase relations in the SrO–Ga 2O 3–B 2O 3 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 SrGaBO 4 has two modifications (- and β-phases), both of which crystallize in the orthorhombic system but with different space groups. 相似文献
13.
The DSA anodes based on RuO 2–SnO 2 oxides are most employed in chlorine-alkali cells. Their properties are strongly influenced by the mixed-oxide coating structures. In this paper, two RuO 2–SnO 2/Ti DSA anodes with different Ru and Sn molar ratios were prepared through a sol–gel technique. The nano-structure, morphology, grain structure and composition of the coatings were investigated by means of XRD, SEM and TEM. XRD analysis indicates two rutile-type solid solutions are formed. Peak profile analysis shows that in the solid solution where SnO 2 is the major component smaller crystallites (about 20–30 nm) are formed than in those where RuO 2 is the major component (about 100–200 nm). The SEM images reveal the coating with high level of SnO 2 possesses more accumulated and compact structures. The EDS analysis indicates that two DSA anodes coatings in which SnO 2 is similar to the designed concentration are prepared by the sol–gel method. TEM characterization shows the polygonal crystallites are present in the obtained RuO 2–SnO 2 coatings. The voltages of Cl 2-evolution and O 2-evolution suggest both RuO 2–SnO 2/Ti DSA anodes have a good electrochemical performance and can be used for the chlorite industrial productions. 相似文献
14.
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 ZrO 2–Al 2O 3 composite material, containing 20 wt% of Al 2O 3, 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 ZrO 2 and Al 2O 3 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 m 1/2, which makes it suitable for bioapplications, such as dental implants. 相似文献
15.
The catalytic effect of the addition of lanthanum oxide (La 2O 3), in the range 0.5–2.0 mol%, on the hydrogen storage properties of MgH 2 prepared by ball milling has been studied. The addition of La 2O 3 reduces the formation during milling of the metastable orthorhombic γ-MgH 2 phase. The desorption rate of samples with 1 and 2 mol% La 2O 3 comes out to be about 0.010 wt% per second at 573 K under an hydrogen pressure of 0.3 bar, better than for sample with 0.5 mol% La 2O 3. The presence of LaH 3 after hydrogenation/dehydrogenation cycles has been observed in all samples. The sample with 1 mol% of La 2O 3 gives a lower hysteresis factor compared with sample with 2 mol%. 相似文献
16.
Aluminum matrix composites reinforced by Al 3Zr and ZrB 2 particles were fabricated from Al– x wt.%(K 2ZrF 6–KBF 4) ( x = 5, 10, 15, 20, 25) systems via magnetochemistry in situ reaction and the dry sliding wear properties and behavior of the composites were investigated. XRD and SEM analysis show that ZrB 2 and Al 3Zr reinforcement phases have been obtained and been distributed uniformly in the aluminum matrix. Wear test results show that the values of wear weight loss of the composites decrease with the increase of x under all identical wear conditions, and that of the relative wear resistance Rrelat. increases under the applied load of 100 N. Especially, when x = 25, the wear weight loss (under a sliding time of 120 min and an applied load of 100 N), which is 0.245 to that of the A356 alloy, and the Rrelat. (under the intermediate wear-sliding stage and an applied load of 100 N) is 4.772, which is 1.513 to that of the primary stage, respectively. Two modes of the wear mechanisms of the as-prepared composites were identified. 相似文献
17.
Pore morphology and pore size distribution in yttria-stabilized zirconia (ZrO 2–8 mol% Y 2O 3) have been investigated, for two sintering temperatures, namely 1200 and 1270 °C, using small-angle neutron scattering. The results show that the reduction in the porosity, at 1270 °C compared to that at 1200 °C, occurs by the elimination of the pores at the lower end of the pore size distribution. In addition, the polydispersity is also lower at 1270 °C and the nature of the distribution is altered significantly near the smaller radius range. The average pore size shifts towards the higher radius range. The specific surface area of the pores is also diminished at 1270 °C because of the elimination of the finer pores. 相似文献
18.
Al 2O 3–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 Al 2O 3–TiC composites. The maximum bending strength of the submicron Al 2O 3 with the fine TiC powders addition is 712 MPa, while the maximum fracture toughness of the same Al 2O 3 matrix with the large TiC powders addition is 6.5 MPa m 1/2. 相似文献
19.
To clarify the existence of metastable phases in the ZrO 2–CeO 2–CeO 1.5 system, evolved-oxygen gas analyses, (EGA), by heating a single phase of t′ and t″ (Ce (1−x)Zr xO 2) with various compositions, x, in a reducing gas and successive oxidation were carried out repeatedly. The oxygen release behaviour of the t′ and t″ phases was very complicated. The single κ phases, (Ce (1−x)Zr xO 2) with the composition, x=0.5 and 0.6, which were obtained by oxidizing the resulting pyrochlore as a precursor in O 2 gas at 873 K, exhibited a sharp oxygen release at the lowest temperature; the composition range of κ phase may be x=0.450.65. A new tetragonal phase t*, (Ce (1−x)Zr xO 2), which was attained by cyclic redox process together with annealing in O 2 gas at 1323 or 1423 K, exhibited a sharp oxygen release at the highest temperature; the composition range of t* phase may be as wide as x=0.200.65. A metastable solid solution expressed by a chemical formula of Ce (8−4y)Zr 4yO (14−δ) ( y=01) possessing a CaF 2-related structure appeared on deoxidation of the t* phase. A ternary phase diagram containing the t* and Ce (8−4y)Zr 4yO (14−δ) solid solution was proposed. 相似文献
20.
In the present work, the spectroscopic and magnetic properties of heteronuclear Cu:Pr squarate are reported. Single crystals of [Pr 2Cu(C 4O 4) 4(H 2O) 16]·2H 2O were obtained by reaction of squaric acid, praseodymium chloride and copper chloride in water solution according to the procedure described earlier. The crystals of title compound are isomorphic with [La 2Cu(C 4O 4) 4(H 2O) 16]·2H 2O crystal, where squarate anions participate as bridging ligands between metal ions. The UV region of absorption spectra of the title compound is dominated by C–T band of Cu(II), f–d transition of Pr(III) and internal π–π*(A1g→Eu) and π–π*(A1g→Eg) ligand transitions. In visible and IR regions, t2g–eg of copper Cu(II) as well as 3H4→3PJ, 1D2, 1G4, 3FJ, 3H6 Pr(III) transitions at 293 and 4 K were recorded. At low temperature splitting given by Jahn–Teller effect can be observed. Significant anisotropy of d–d transitions intensities confirms well the Jahn–Teller effect, too. Unexpectedly high intensity of 3H4→1G4 transition is probably due to the intensity borrowing from the Cu (II) d–d transition. The 3P0 and 1D2 emission of Pr(III) in the [Pr2Cu(C4O4)4(H2O)16]·2H2O crystals is quenched even at 77 K. Whereas emission of appropriate polynuclear europium squarate was detected. The pathways of excited state quenching by eg levels of Cu(II), multhiphonon relaxation and concentration quenching can be considered in the system under studies. Magnetic susceptibility measurements were carried out in 300–1.7 K temperature range and are discussed in relation to the structure. Effect of the polymeric structure on spectroscopic behaviour is presented. Selectivity of polymeric europium squarate in vitro test for different tumor cells is shown. 相似文献
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