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1.
Specimens of the glassy system: (70 − x)TeO2 + 15B2O3 + 15P2O5 + xLi2O, where x = 5, 10, 15, 20, 25 and 30 mol% were prepared by the melt-quenching. An ultrasonic pulse-echo technique was employed, at 5 MHz, for measuring: the ultrasonic attenuation, longitudinal and shear wave velocities, elastic moduli, Poisson ratio, Debye temperature and hardness of the present glasses. It is found that the gradual replacement of TeO2 by Li2O in the glass matrix up to 30 mol% leads to decrease the average crosslink density and rigidity of prepared samples which affects the properties, i.e., the hardness, ultrasonic wave velocities and elastic moduli are decreased, while the Poisson ratio and the ultrasonic attenuation are increased. Also, optical absorption spectra were recorded in the range, 200-800 nm for these glasses. The obtained results showed that a gradual shift in the fundamental absorption edge toward longer wavelengths occurred. Values of both of the optical energy gap, Eopt, and width tails, ΔE, are determined. It is observed that Eopt is decreased and ΔE increased with the increase of Li2O in the glass matrix up to 30 mol%. The compositional dependences of the above properties are discussed and correlated to the structure of tested glasses.  相似文献   

2.
Transport property and structural investigation have been carried out on newly synthesized Ag+ ion conducting composite electrolyte system. The composite electrolyte system (1 − x)[0.75AgI:0.25AgCl]:xTiO2, where 0 ? x ? 0.5 (in molar weight fraction) has been synthesized by melt quenching and annealing methods. The chemical compound TiO2 (second phase dispersoid) dispersed in different compositions in a quenched (0.75AgI:0.25AgCl) mixed system/solid solution; this solid solution was used as a first phase host salt in place of AgI. The different preparation routes were adopted for the composite electrolyte system. Composition x = 0.1 exhibited highest conductivity at room temperature. The composite system 0.9[0.75AgI:0.25AgCl]:0.1TiO2 was synthesized at different soaking times by melt quenching method. The system exhibited optimum conductivity at 20 min soaking time (σrt ≈ 1.4 × 10−3 S/cm). The ac conductivity has been measured from Z′-Z″ (Cole-Cole) complex impedance plots using impedance spectroscopic (IS) technique. The electrical conductivity as a function of temperature and frequency has been studied, and activation energy Ea, was calculated from Arrhenius plots for all compositions (0 ? x ? 0.5). The dc conductivity value has been evaluated from Log σ vs. log f plots. Structural characterization studies were carried out by X-ray diffraction (XRD) and differential thermal analysis (DSC) techniques.  相似文献   

3.
CuZr as well as CoZr are well known metallic glass-formers in a wide compositional range. Since the binary Cu-Co system exhibits a metastable liquid-liquid miscibility gap, i.e. Cu and Co tend to separate from each other, the ternary Cu-Co-Zr system is a promising candidate to form phase separated glass-glass composites. In this work (Cu60Co40)1 − xZrx metallic glasses with relatively low Zr contents of x = 37 and x = 32 were prepared by melt spinning and investigated by in-situ small-angle and wide-angle X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Certain heat treated samples were additionally investigated by high-resolution transmission electron microscopy (HRTEM). Even for x = 32 there are no indications for any kind of phase separation in the as-quenched state within experimental resolution, i.e. the critical temperature Tc for a liquid-liquid phase separation has already decreased from 1556 K for binary Cu60Co40 to a temperature below the glass transition temperature Tg = 762(5)K found for (Cu60Co40)68Zr32. Combined in-situ SAXS/WAXS and HRTEM investigations reveal that thermal annealing also does not induce an amorphous-amorphous phase separation. Instead the formation of nano crystallites of a so far unknown Cu-rich/Zr-poor phase with relatively low activation energy for crystallization Ea = 116(7) kJ/mol at temperatures far below the crystallization temperature deduced from DSC measurements is observed.  相似文献   

4.
Erbium-doped glasses with composition xGeO2-(80 − x)TeO2-10ZnO-10BaO were prepared by melt-quenching technique. The phonon sideband spectra and the optical absorption band edges for the host matrix were confirmed by means of the spectral measurements. Standard Judd-Ofelt calculations have been completed to these glasses. The dependence of up-conversion and infrared emission under 980 nm excitation on the glass composition was studied. The quantum efficiencies for the 4I13/2 → 4I15/2 transition of trivalent erbium in the glasses were estimated.  相似文献   

5.
Spectrometric and ellipsometric studies of (1 − x)TiO2 · xLn2O3 (Ln = Nd, Sm, Gd, Er, Yb; x = 0.33, 0.5) thin films at room temperature were performed. The obtained dispersion dependences of refractive indices are successfully described by the optical-refractometric relation. The dependence of optical pseudogap and refractive indices on composition and molar mass of the films is investigated. The influence of compositional disordering on the energy width of the exponential absorption edge is studied.  相似文献   

6.
N. Baizura 《Journal of Non》2011,357(15):2810-2815
Tellurite 75TeO2-(10 − x)Nb2O5-15ZnO-(x)Er2O3; (x = 0.0-2.5 mol%) glass system with concurrent reduction of Nb2O5 and Er2O3 addition have been prepared by melt-quenching method. Elastic properties together with structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo-overlap technique at 5 MHz and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Shear velocity, shear modulus, Young's modulus and Debye temperature were observed to initially decrease at x = 0.5 mol% but remained constant between x = 1.0 mol% to x = 2.0 mol%, before increasing back with Er2O3 addition at x = 2.5 mol%. The initial drop in shear velocity and related elastic moduli observed at x = 0.5 mol% were suggested to be due to weakening of glass network rigidity as a result of increase in non-bridging oxygen (NBO) ions as a consequence of Nb2O5 reduction. The near constant values of shear velocity, elastic moduli, Debye temperature, hardness and Poisson's ratio between x = 0.5 mol% to x = 2.0 mol% were suggested to be due to competition between bridging oxygen (BO) and NBO ions in the glass network as Er2O3 gradually compensated for Nb2O5. Further addition of Er2O3 (x > 2.0 mol%) seems to further reduce NBO leading to improved rigidity of the glass network causing a large increase of ultrasonic velocity (vL and vS) and related elastic moduli at x = 2.5 mol%. FTIR analysis on NbO6 octahedral, TeO4 trigonal bipyramid (tbp) and TeO3 trigonal pyramid (tp) absorption peaks confirmed the initial formation of NBO ions at x = 0.5 mol% followed by NBO/BO competition at x = 0.5-2.0 mol%. Appearance of ZnO4 tetrahedra and increase in intensity of TeO4 tbp absorption peaks at x = 2.0 mol% and x = 2.5 mol% indicate increase in formation of BO.  相似文献   

7.
Glasses of the system: (70−x) TeO2 + 15B2O3 + 15P2O5 + xLi2O, where x = 5, 10, 15, 20, 25 and 30 mol% were prepared by melt quench technique. Dependencies of their glass transition temperatures (Tg) and infrared (IR) absorption spectra on composition were investigated. It is found that the gradual replacement of oxides, TeO2 by Li2O, decreases the glass transition temperature and increases the fragility of the glasses. Also, IR spectra revealed broad weak and strong absorption bands in the investigated range of wave numbers from 4000 to 400 cm−1. These bands were assigned to their corresponding bond modes of vibration with relation to the glass structure.  相似文献   

8.
L.Y. Zhu 《Journal of Non》2009,355(1):68-207
ZrxTi1−xO2 (x = 0.1-0.9) fibers were prepared by the sol-gel dry-spinning method. Polyacetylacetonatozirconium (PAZ) and tetrabutyl titanate (C16H36O4Ti) were used as raw materials. The green fibers were obtained from the amorphous spinnable solution and then heat-treated to convert into polycrystalline fibers. The main phase changes from TiO2 to zirconium titanate (ZT) and then tetragonal ZrO2 with increasing ZrO2 content. The crystallization temperature varied with the molar ratio of Zr:Ti. The heat-treated fibers at 1050 °C have few pores and no cracks with diameters of 10-20μm and lengths of 1-5 cm.  相似文献   

9.
Glasses with the mol% composition 4.9Na2O · 33.3CaO · 17.1Fe2O3 · 44.7B2O3 were melted, rapidly quenched using a twin roller technique, and subsequently tempered in the range from 550 to 620 °C. This led to the crystallization of magnetite with mean crystallite sizes in the 10-20 nm range. Using higher temperatures resulted in a larger quantity of formed crystallites and slightly larger mean crystallite sizes. Larger tempering times did not lead to substantial crystal growth. The time law of Ostwald ripening was not followed. This is explained by an increase in viscosity of the residual glassy phase during nucleation and crystal growth. Here, the smaller iron concentration near the crystals leads to higher viscosities and to the formation of a diffusional barrier around the crystals, which reduces further crystal growth. The crystallization stops, if Tg of the residual glassy phase is equal to the tempering temperature. Magnetite nano crystals with sizes in the 10-20 nm range offer a wide range of applications, such as the preparation of ferrofluids or of materials for medical diagnostics and therapy.  相似文献   

10.
P. Bharathan 《Journal of Non》2011,357(18):3366-3372
We have experimentally measured the current-voltage and capacitance-voltage characteristics of Au/amorphous AsxSe1 − x (x ≤ 0.05)/Zr trilayer structures at temperatures from 4 to 295 K. The observed capacitance of structures with an amorphous AsxSe1 − x (a-AsxSe1 − x) thickness of ~ 0.4 to ~ 2.8 μm does not significantly change over the entire range of applied bias (− 5 V to 5 V), indicating that the a-AsxSe1 − x films are fully depleted and thus the structures are Mott barriers. The current-voltage (I-V) characteristics of the a-As0.03Se0.97 device at low (< 3000 V/cm) to moderate fields (3000 V/cm-10000 V/cm) follow the predictions of trap limited space charge conduction theory, as they exhibit Ohmic behavior at low fields and trap limited space charge current at moderate fields. According to the trap limited space charge current model of Lampert, the a-As0.03Se0.97 film has an effective hole mobility, Θμ (with Θ < 1), of ~ 5 × 10− 7 cm2/V-sec at 295 K. This value is similar to, but consistently lower than previously reported mobilities inferred from time of flight measurements. The current at high fields (> 104 V/cm) increases rapidly with applied field as a result of carrier emission from localized states and is consistent with transport by the Poole-Frenkel mechanism. A permanent transition to a high conductance state (~ 10− 3 S) is observed after exposure to very high electric fields (~ 4 × 105V/cm).  相似文献   

11.
The thermodynamical miscibility in 0.8[xB2O3-(1 − x)P2O5]-0.2K2O glasses has been studied by measuring the glass transition temperature and the mixing enthalpy. Measurements have been performed by differential scanning calorimeter and hydrofluoric acid solution calorimetry at 298 K. The enthalpies of mixing are significantly negative over the whole range of composition. The results are discussed in terms of intermolecular associations.  相似文献   

12.
Qiang Mei 《Journal of Non》2003,324(3):264-276
The glass forming range of the Ag2S + B2S3 + GeS2 ternary system was investigated for the first time and a wide range of ternary glasses were obtained. The Archimedes’ method was used to determine the densities of the Ag-B-Ge glasses. The thermal properties of these thioborogermanate glasses were studied by DSC and TMA. The Raman, IR and NMR spectroscopy were used to explore the short-range order structure of the binary (Ag-B) and (Ag-Ge) and ternary (Ag-B-Ge) glasses. The results show the presence of bridging sulfur tetrahedral units, GeS4/2 and AgBS4/2, and trigonal units, BS3/2, in the ternary glasses. Non-bridging sulfur units, AgSGeS3/2 and Ag3B3S3S3/2 six membered rings, are also observed in these glasses at higher Ag2S modification levels because the further addition of Ag2S results in the degradation of the bridging structures to form non-bridging structures. The NMR studies show that Ag2S goes into the GeS2 subnetwork to form Ag3S3GeS1/2 groups before going to the B2S3 subnetwork. In doing so, it is suggested that B10S20 supertetrahedra exist in Ag2S + B2S3 and Ag2S + B2S3 + GeS2 glasses. Significantly B-S-Ge bonds form in the B2S3 + GeS2 glasses, whereas they appear to be absent in the ternary glasses. From these observations, a structural model for these glasses has been developed and proposed.  相似文献   

13.
N. Bayri  H. Gencer  M. Gunes 《Journal of Non》2009,355(1):12-2594
In this study, we have investigated the effect of substituting Mn for Fe on the crystallization kinetics of amorphous Fe73.5−xMnxCu1Nb3Si13.5B9 (x = 1, 3, 5, 7) alloys. The samples were annealed at 550 °C and 600 °C for 1 h under an argon atmosphere. The X-ray diffraction analyses showed only a crystalline peak belonging to the α-Fe(Si) phase, with the grain size ranging from 12.2 nm for x = 0 to 16.7 nm for x = 7. The activation energies of the alloys were calculated using Kissinger, Ozawa and Augis-Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson-Mehl-Avrami equation. The activation energy increased up to x = 3, then decreased with increasing Mn content. The values of the Avrami exponent showed that the crystallization is typical diffusion-controlled three-dimensional growth at a constant nucleation rate.  相似文献   

14.
A high-energy X-ray diffraction study has been carried out on a series of 0.5Li2S + 0.5[(1 − x)GeS2 + xGeO2] glasses with x = 0.0, 0.1, 0.2, 0.4, 0.6 and 0.8. Structure factors were measured to wave vectors as high as 30 Å−1 resulting in atomic pair distribution functions with high real space resolution. The three dimensional atomic-scale structure of the glasses was modeled by reverse Monte Carlo simulations based on the diffraction data. Results from the simulations show that at the atomic-scale 0.5Li2S + 0.5[(1 − x)GeS2 + xGeO2] glasses may be viewed as an assembly of independent chains of (Li+-S)2GeS2/2 and (Li+-O)2GeO2/2 tetrahedra as repeat units, where the Li ions occupy the open space between the chains. The new structure data may help understand the reasons for the sharp maximum in the Li+ ion conductivity at x ∼ 0.2.  相似文献   

15.
Er2O3-doped Bi2O3-B2O3-Ga2O3 glasses were prepared by the conventional melt-quenching method, and the Er3+:4I13/2 → 4I15/2 fluorescence properties are studied for different Er3+ concentrations. when the Er2O3 concentration increases from 0.03 to 3.0 mol%, the measured lifetime of Er3+:4I13/2 level decrease from 2.24 to 0.9 m s, and from 0.25 to 0.20 m s for the Er3+:4I11/2 level. The fast energy migration among Er3+ ions cause the reduction of lifetime of the 4I13/2 level, whereas the change in the 4I11/2 level is mainly due to a cooperative upconversion process (4I11/24I11/2) → (4F7/24I15/2). Based on the dipole-dipole interaction theory, the interaction parameter, CEr,Er, for the migration rate of Er3+:4I13/2 ↔ 4I13/2 was calculated to be 32 × 10−40 cm6 s−1.  相似文献   

16.
R.G. Kuryaeva 《Journal of Non》2009,355(3):159-163
The refractive index for glass of the CaO · Al2O3 · хSiO2 system with х = 6 in the range of pressures up to 6.0 GPa was measured using a polarization-interference microscope and an apparatus with diamond anvils. The changes in the relative density characterizing the compressibility of glass were estimated from the measured refractive indices within the framework of the theory of photoelasticity. The data were compared with the previous data for glasses of the same system with х = 2 and 4. The most compressible of the three glasses in the range 2.0-6.0 GPa was the CaO · Al2O3 · 6SiO2 glass. For glasses with х = 2, 4 and 6 we calculated the degrees of polymerization of silicon-aluminum-oxygen network, NBO/T (NBO - non-bridging oxygen), which are determined as the ratio of the number of gram-ions of non-bridging oxygen atoms to the total number of gram-ions of network formers. The structure-chemical parameter NBO/T was calculated with due regard for the formation of triclusters and highly coordinated aluminum. The degree of polymerization of the CaO · Al2O3 · хSiO2 glasses increases with increasing х, which agrees with the change of their relative density under pressure.  相似文献   

17.
Hongxia Lu 《Journal of Non》2007,353(26):2528-2544
Tracer diffusion coefficients of the radioactive isotope Na-22 were measured in glasses of the type (CaO·Al2O3)x(2 SiO2)1−x to study the diffusion of sodium as a function of glass composition, x, temperature and initial water content. The diffusion of Na-22 in glasses diffusion-annealed in dry air can always be well described by a single tracer diffusion coefficient, but sometimes not in samples annealed in common air. It was found that the sodium tracer diffusion coefficient decreases by about six orders of magnitude when the glass composition x changes from 0 to 0.75 at 800 °C. The temperature dependence of the diffusion of sodium seems to decrease as the silica content increases. Variations of the initial water content in some of the glasses investigated did not very significantly influence the rate of the tracer diffusion of sodium.  相似文献   

18.
Cd1 − xFexTe single crystals were prepared by vapour phase growth method in the composition range of 0 ≤ x ≤ 0.03. Chemical analysis, surface morphology, structural investigations and electrical properties were carried out by EDAX, SEM, XRD, TEM and transport technique, respectively. Microscopic variations between the target and actual compositions were noticed. Morphology studies revealed that dislocation aided growth is active in the present crystals. TEM and XRD studies confirmed that the samples of all compositions crystallized in zinc blende structure, and the lattice parameters varied almost linearly decreases with Fe content. At room temperature, the resistivity of the Cd1 − xFexTe crystals of all compositions (x = 0.01, 0.015, 0.02, 0.025 and 0.03) lies in the range of 3.5-6.5 M Ω, the activation energies lie in the range of 63-133 meV, and the samples were show the ‘p’ type conductivity.  相似文献   

19.
Shengchun Li  B. Li  J.J. Wei 《Journal of Non》2010,356(43):2263-2267
(30 − x/2)Li2O·(70 − x/2)B2O3·xAl2O3(x = 0, 5 and 10) composite gels have been fabricated by the sol-gel method. LiOCH3, B(OC4H9)3, and Al(OC4H9)3 were used as precursor for Li2O, B2O3, and Al2O3, respectively. B(OC4H9)3 and Al(OC4H9)3 were hydrolyzed separately and then mixed. The crystallization behavior and structure of the gels upon thermal treatment temperatures between 150 and 550 °C are characterized on the basis of SEM, XRD and IR analyses. Xerogel with x = 0 exhibits non-crystal features, whereas crystalline phases are found in the xerogels with x = 5 and 10. The crystalline phases are not found with increasing heat treatment temperatures from 150 to 450 °C, but crystalline phases appear present at 550 °C. The xerogel with x = 0, subject to thermal treatment below 450 °C, is found to be still amorphous, and a 550 °C heat treatment leads its structure changing from glassy to crystalline.  相似文献   

20.
Refractory bulk metallic glasses and bulk metallic glass composites are formed in quaternary Ni-Nb-Ta-Sn alloy system. Alloys of composition Ni60(Nb100−xTax)34Sn6 (x = 20, 40, 60, 80) alloys were prepared by injection-casting the molten alloys into copper molds. Glassy alloys are formed in the thickness of half mm strips. With thicker strips (e.g., 1 mm), Nb2O5 and Ni3Sn phases and the amorphous phase form an in situ composite. Glass transition temperatures, crystallization temperatures, and ΔTx, defined as Tx1 − Tg (Tx1: first crystallization temperature, Tg: glass transition temperature) of the alloys increase dramatically with increasing Ta contents. These refractory bulk amorphous alloys exhibit high Young’s modulus (155-170 GPa), shear modulus (56-63 GPa), and estimated yield strength (3-3.6 GPa).  相似文献   

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