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1.
The new calcium aluminoborate glasses with the composition of CaO–Al2O3–B2O3–RE2O3 (RE = Dy and Tb) were synthesized and the luminescence of Dy3+ and Tb3+ was investigated. The results show that the emission intensity of Tb3+ ion was enhanced when introducing Dy3+ ion into CaO–Al2O3–B2O3–Tb2O3 glass due to the energy transfer processes between Dy3+ and Tb3+. The energy transfer efficiencies, transfer probabilities as well as donor–acceptor critical distances were also calculated. The energy transfer mechanism between Dy3+ and Tb3+ ions is electric dipole–dipole interaction, which can be concluded by both fluorescence decay and emission intensity ratio varieties. 相似文献
2.
Kai Zheng Shengbing Yang Jiaojiao Wang Christian Rűssel Changsheng Liu Wen Liang 《Journal of Non》2012,358(2):387-391
A novel Na2O–K2O–CaO–MgO–SrO–B2O3–P2O5 borophosphate glass fiber is prepared. The thermal properties including differential thermal analysis (DTA) and viscosity measurement of the glass were presented. The tensile strength of the glass fiber is measured. The reaction of the glass fibers in the SBF solution is characterized by XRD, FTIR and SEM. XRD and FTIR indicate that the carbonate hydroxyapatite has formed rapidly on the glass. Cell attachment, spreading and proliferation on the glass are determined by MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay method using Human osteosarcoma MG-63 cells. The bioactivity and biocompatibility of the glass fiber make it a good potential prospect in the field of tissue engineering. 相似文献
3.
In an effort to design low-melting, durable, transparent glasses, two series of glasses have been prepared in the NaPO3–ZnO–Nb2O5–Al2O3 system with ZnO/Nb2O5 ratio of 2 and 1. The addition of ZnO and Nb2O5 to the sodium aluminophosphate matrix yields a linear increase of properties such as glass transition temperature, density, refractive index and elastic moduli. The chemical durability is also significantly, but nonlinearly, improved. The glass with the highest niobium concentration, 55NaPO3–20ZnO–20Nb2O5–5Al2O3 was found to have a dissolution rate of 4.5 × 10? 8 g cm? 2 min? 1, comparable to window glass. Structural models of the glasses were developed using Raman spectroscopy and nuclear magnetic resonance spectroscopy, and the models were correlated with the compositional dependence of the properties. 相似文献
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5.
Transparent glass-ceramics were synthesized by heat-treatment of glass with a composition of 5La2O3–13.2MgO–28.8Al2O3–46SiO2–4.5TiO2–2.5ZrO2–0.15CoO (LMAS) (wt.%). The activation energy of crystallization and the Avrami parameter for the LMAS glass were determined from the DTA curves at different heating rates. The most two intense bands of Raman spectrum of initial glass at ~ 810 cm?1 and ~ 900 cm?1 were connected with the presence of [SiO4] and [TiO4] tetrahedral, respectively. After heat-treated at 700 °C/10 h+820 °C/8 h, the intensity of the band for [TiO4] tetrahedral weakened, while an intensive band at ~ 800 cm?1 for the Ti–O bond appeared. Other bands were characteristics of high-silicate network and x(MgTi2O5)·y(Al2TiO5) polycrystals. The changes reflected phase separation after heat-treatment of the initial glass. The strong absorption band of glass-ceramics centered at 580 nm can be assigned to 4A2(4F)→4T1(4P) and the broad absorption band at 1100–1700 nm to 4A2(4F)→4T1(4F) transitions of tetrahedral coordinated Co2+ ion. Two broad emission bands, one was around 660 nm, the other was from 800 nm to 1050 nm, of glass-ceramics correspond to the 4T1(4P)→4A2(4F) and 4T1(4P)→4T2(4F) transitions of tetrahedral coordinated Co2+ ions. The absorption and emission features clearly demonstrated that Co2+ ions were incorporated into nanocrystals and located in tetrahedral sites. 相似文献
6.
Co2+-doped La2O3–MgO–Al2O3–SiO2 (LMAS) glass-ceramics was synthesized by conventional method. The microstructure of LMAS GCs heat-treated at 760 °C/12 h + 930 °C/4 h was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The spectroscopic properties of Co2+-doped LMAS GCs were studied by absorption spectrum, excitation spectrum, and temperature dependent luminescence spectra. XRD results revealed the sizes of MgAl2O4 crystalline phases are about 9.1 ± 1.5 nm. The three peaks in the visible absorption band of LMAS GCs at 549 nm, 585 nm and 626 nm are connected with the transitions from 4A2 level to 2A1/2T2(2G), 4T1(4P) and 2E/2T1(2G) levels, respectively, and excitations into them emit the radiation at around 666 nm. The luminescence intensity increased with temperature increasing from 10 K to 150 K, while it weakened with temperature increasing from 150 K to 350 K. These features were explained by the effects of two competing mechanisms. 相似文献
7.
A. Edukondalu M. Purnima Ch. Srinivasy T. Sripathi A.M. Awasthi Syed Rahman K. Siva Kumar 《Journal of Non》2012,358(18-19):2581-2588
Glasses with composition xLi2O-(30 ? x)Na2O–10WO3–60B2O3 (where x = 0, 5, 10, 15, 20, 25 and 30 mol%) have been prepared using the melt quenching technique. In the present work, the mixed alkali effect (MAE) has been investigated in the above glass system through density and modulated DSC studies. The density and glass transition temperature of the present gasses varies non-linearly, the exhibiting the mixed alkali effect. From the optical absorption studies, the values of direct optical band gap, indirect optical band gap energy (Eo) and Urbach energy(ΔE) have been evaluated. The values of Eo and ΔE vary non-linearly with composition parameter, showing the mixed alkali effect. The electronic polarizability of oxide ions, optical basicity and the Yamashita–Kurosawa's interaction parameter have been examined to check the correlation among them and bond character. Based on good correlation among electronic polarizability of oxide ions, optical basicity and the Yamashita–Kurosawa's interaction parameter, the present Li2O–Na2O–WO3–B2O3 glasses were classified as normal ionic (basic) oxides. 相似文献
8.
Influence of single fluxes (10 wt.% B2O3), bi-component fluxes (4 wt.% B2O3 + 6 wt.% Na3AlF6), and complex fluxes (4 wt.% B2O3 + 4 wt.% Na3AlF6 + 2 wt.% Na2O) on the thermal kinetic parameters, microstructure, flexural strength and coefficient of thermal expansion (CTE) of Li2O–Al2O3–4SiO2 (LAS) glass–ceramics was investigated through differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that complex fluxes could efficiently decrease transition temperature (Tg) and crystallization temperature (Tp), and accelerate the formation of needle-like β-spodumene crystals which benefit high flexural strength. The homogeneous LAS glass–ceramic (sample C3) which has a high strength of 132.4 MPa and low CTE (100–650 °C) of 2.74 × 10? 6/°C is obtained by doping of the initial LAS glass by complex fluxes of 4 wt.% B2O3, 4 wt.% Na3AlF6, and 2 wt.% Na2O, nucleating at 630 °C/120 min and then crystallized at 780 °C/120 min. It is worthy of further investigation as a bonder of diamond composite material due to its outstanding prosperities. 相似文献
9.
《Journal of Non》1997,210(1):95-100
Bi particles of different sizes were produced in Na2O–B2O3 glasses by melt quenching and heat treatment technique. Melting temperature of Bi particles was measured by differential scanning calorimetry and X-ray diffraction. Measured melting temperatures of Bi particles are lower than bulk Bi melting temperature. Results of transmission electron microscopy were analyzed for the dependence of melting temperature on particle radius. The pressure and surface energy effect on melting temperature is estimated. The melting behavior of Bi particles in Na2O–B2O3 glasses depends on the difference in the interfacial energies between the solid particle/glass and liquid particle/glass, and liquid particle/glass, σsm−σlm, which is estimated to be 255×10−3 J m−2. 相似文献
10.
Glasses in the formulation close to BaSiO3–BaB2O4 eutectic compound are developed for sealing of intermediate-temperature (500–650 °C) solid oxide fuel cell (IT-SOFC). Thermal and microstructural analyses of the glasses with 0–10 mol% Al2O3 are also conducted. Detailed crystallization kinetics and interfacial stability of the glass in contact with yttria-stabilized zirconia (YSZ) and samaria-doped ceria (SDC) are investigated and compared. The results show that the formulation, 47BaO–21B2O3–27SiO2–5Al2O3 (G1A5), performs the best on glass forming ability (GFA) among all tested formulations, and shows matched thermal expansion and working temperature to CeO2-based electrolytes of IT-SOFC. Two major crystalline phases that precipitate from G1A5 above 750 °C are platy hexacelsian and BaSiO3 grains. 相似文献
11.
Ki-Dong Kim 《Journal of Non》2008,354(15-16):1715-1720
The influence of K2O/(MgO + K2O) on some melt properties, including crystallization during cooling of melts and glass-forming ability, was investigated in the Li2O–Al2O3–SiO2 system with low Al2O3 content. The dependence of viscosity on K2O/(MgO + K2O) above 1000 °C showed a monotonic decrease due to the reduction of [MgO4] concentration and the conductivity also decreased due to the larger ion radius of K. The temperature dependence of conductivity for all melts showed an abrupt change at one temperature due to crystallization in which temperature of crystallization decreases with increase of K2O. The crystallization behavior near liquidus temperature was studied quantitatively by calculating the crystal volume fraction from apparent viscosity value. The glass-forming ability of the melts was discussed by using data related with viscosity and crystallization. Finally, it was suggested that the melts with K2O/(MgO + K2O) ? 0.75 have a good glass-forming ability. 相似文献
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The effect of the substitution of ZnO for TiO2 on the chemical durability of Bi2O3–SiO2–ZnO–B2O3 glass coatings in hot acidic medium (0.1 N H2SO4 at 80 °C) for different times was studied. The thick films produced by a screen-printing method and heat treated at 700 °C/5 min were analyzed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The glass from the Bi2O3–SiO2–ZnO–B2O3 system developed Zn2SiO4 and a glassy phase that were readily attacked by hot 0.1 N sulfuric acid, whereas the heat treated coating from the Bi2O3–SiO2–TiO2–ZnO–B2O3 system presented a finer microstructure with thin interconnected Bi4Ti3O12 crystals and a glassy phase more resistant to hot 0.1 N sulfuric acid attack etching. 相似文献
14.
SiO2–B2O3 aerogels have been prepared by drying wet gels at a supercritical condition for ethanol in an autoclave. Aerogels have been nitrided for 6 h in flowing ammonia at the temperature of 1200 °C. It has been found that the amount of nitrogen incorporated in these aerogels always exceeds 20 wt%. This is a much higher value compared with the amount of nitrogen incorporated in a pure silica aerogel nitrided at the same conditions. The specific surface area of SiO2–B2O3 aerogels has been between 312 and 359 m2/g. After nitridation some shrinkage of aerogels has been observed and the surface area decreases about 20%. In FTIR spectra of SiO2–B2O3 aerogels a typical bands for SiO2 are observed. After nitridation a shift and broadening of 1100 cm?1 band to lower wavenumbers indicates that Si–N and B–N bonds are formed in nitrided aerogels. 相似文献
15.
M. Shapaan 《Journal of Non》2009,355(16-17):926-931
This paper presents the results of kinematical studies of glass transition and crystallization in the unconventional glassy system (60?x)V2O5–xAs2O3–20Fe2O3–10CaO–10Li2O (x = 0, 10, 20, 30, 40 mol%) using differential scanning calorimetry (DSC). The glass transition temperatures (Tg), the onset crystallization temperatures (Tc), and the peak temperatures of crystallization (Tp) were found to be dependent on the compositions and the heating rates. From the dependence on heating rates of (Tg) and (Tp) the activation energy for glass transition (Eg) and the activation energy for crystallization (Ec) are calculated. The thermal stability of (60?x)V2O5–xAs2O3–20Fe2O3–10CaO–10Li2O was evaluated in term of, criteria ΔT = Tc ? Tg. All the results confirm that the thermal stability increase with increasing As2O3 contents. From the electric–dielectric measurements it was found that, σdc, σac(ω) and θD/2 decrease with increasing As2O3 contents. It is also observed that the dielectric constant (ε1(ω)) and the loss factor (tan δ) decrease with increasing As2O3 contents in this glass system. 相似文献
16.
Xiao Hu Guillaume Guery Joshua Boerstler J. David Musgraves Don Vanderveer Peter Wachtel Kathleen Richardson 《Journal of Non》2012,358(5):952-958
Glass ceramic materials with composition 75TeO2–xBi2O3–(25-x)ZnO (x = 13, 12, 11) possessing transparency in the near- and mid-infrared (MIR) regions were studied in this paper. It was found that as the Bi2O3 content increased in the glass composition, the observed crystallization tendency is enhanced, and high crystal concentrations were obtained for the glasses with high Bi2O3 content while maintaining transparency in the MIR region. Crystal size in the glass ceramic was reduced by adjusting the heat treatment conditions; the smallest average size obtained in this study is 700 nm. Bi0.864Te0.136O1.568 was identified using X-ray Diffraction (XRD) and found to be the only crystal phase developed in the glass ceramics when the treatment temperature was fixed at 335 °C. The morphology of the crystals was studied using Scanning Electron Microscopy (SEM), and crystals were found to be polyhedral structures with uniform sizes and a narrow size distribution for a fixed heat treatment regime. Infrared absorption spectra of the resulting glass ceramics were studied. The glass ceramic retained transparency in the infrared region when the crystals inside were smaller than 1 μm, with an absorption coefficient less than 0.5/cm in the infrared region from 1.25 to 2.5 μm. The mechanical properties were also improved after crystallization; the Vickers Hardness value of the glass ceramic increased by 10% relative to the base glass. 相似文献
17.
The structure of glasses within the system Li2O–Al2O3–B2O3–P2O5 has been studied through 31P, 11B and 27Al Nuclear Magnetic Resonance, and the effect of Al2O3 substitution by B2O3 and P2O5 network formers on the structure and properties investigated for a constant Li2O content. Multinuclear NMR results reveal that substitution of Al2O3 for B2O3 and P2O5 network formers in a glass with composition 50Li2O·15B2O3·35P2O5 produces a change in boron environment from four-fold to three-fold coordination. Meanwhile aluminum can be present in four-, five- and six-fold coordinations a higher amount of Al(IV) groups is found for increasing alumina contents. The behavior of the glass transition temperature and electrical conductivity of the glasses has been interpreted as a function of the structural changes induced in the glass network when alumina is substituted for B2O3, P2O5 or both. Small additions of alumina produce a drastic increase in glass transition temperature, while it does not change for [Al2O3] greater than 3 mol.%. However, the electrical conductivity shows very different behavior depending on the type of substitution; it can remain constant when B2O3 content decreases or sharply decrease when P2O5 is substituted by Al2O3, which is attributed to a higher amount of BO3 and phase separation. 相似文献
18.
F. Pinakidou M. Katsikini P. Kavouras F. Komninou Th. Karakostas E.C. Paloura 《Journal of Non》2008,354(2-9):105-111
The structural role, coordination geometry and valence of Fe in a series of Fe2O3–PbO–SiO2–Na2O glasses are studied by means of Fe-K-NEXAFS and EXAFS spectroscopies. Parameters for the study are the concentration of the Fe and Pb-oxides, the SiO2/Na2O ratio and the cast temperature. The EXAFS and NEXAFS results reveal that the role of Fe3+ depends on the concentration of Fe2O3. More specifically, in most of the studied quaternary systems, the Fe3+ ion is a glass former, i.e. the Fe atoms belong to FeO4 tetrahedra that participate in the formation of the glassy network. The role of Fe as an intermediate oxide is identified only in one sample with 20 wt% Fe2O3, where ~80 at.% of the Fe atoms are tetrahedrally coordinated with O atoms, while the remaining ~20 at.% of the Fe atoms occupy octahedral sites. It is also revealed that the tetrahedral coordination of Fe in the vitreous matrix is destroyed when a number of parameters is altered, such as the Tcast, the (Fe + Si)/O and the SiO2/Na2O ratio. 相似文献
19.
Glasses of the (20 ? x)CaO–xSrO–(20 ? y)Na2O–60B2O3 ? y (CSNB) system with (5 ≤ x ≤ 15) mol% and y = 0.1 mol% of V2O5 were characterized by X-ray diffraction (XRD), EPR (Electron Paramagnetic Resonance), Optical absorption Spectra and FT-IR (Fourier transform Infrared Spectroscopy) studies. EPR spectra of all the glass samples exhibit resonance signals characterstic of VO2+ ions. The values of spin-Hamiltonian parameters indicate that the VO2+ ions in CSNB glasses were present in octahedral sites with tetragonal compression and belong to C4v symmetry. Spin-Hamiltonian parameters ‘g’ and ‘A’ were evaluated. The Optical band energy (Eopt) and Urbach energy (ΔE) were calculated from their ultra violet edges. By correlating EPR and Optical data the molecular orbital coefficients have been evaluated. IR spectra of these glasses were analyzed in order to identify the contribution of each component to the local structure that determines the physical properties of these glasses. 相似文献
20.
Transparent rare-earth Eu3+-doped ZnO–Ga2O3–SiO2 nano-glass-ceramics were obtained by a sol–gel method. X-ray diffraction and transmission electron microscopy were used to characterize the as-synthesized materials. Results showed that ZnGa2O4 nanocrystals with the size of 5 nm were precipitated from ZnO–Ga2O3–SiO2 system and dispersed in the SiO2-based glass when the heat-treatment temperature was up to 800 °C. Photoluminescence characterization of Eu3+-doped ZnO–Ga2O3–SiO2 nano-glass-ceramics was carried out and the results show that the as-synthesized material display intense emission at 615 nm belonging to 5D0 → 7F2 transition. 相似文献