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1.
《Journal of Non》1986,85(3):393-412
The structures of PbO·SiO2 and 2PbO·SiO2 glasses have been analyzed by use of X-ray diffraction data and pair function method. For PbO·SiO2 glass, a model consisting of chains of PbO3 pyramids and silicate chains showed good agreement with the observed RDF. For 2PbO·SiO2 glass, the present authors reported previously a model in which chains of PbO3 pyramids are connected with SiO4 tetrahedra, while the chromatographic analyses of silicate anions by Götz et al. and Smart et al. showed that silicate anions are distributed from monomer to polymer in the glass. We reexamined the structure of this glass referring to these results. Three representative models containing isolated SiO4, Si4O12 rings and (SiO3)n chains respectively as well as PbO3 chains were constructed and the RDFs were calculated with changing structure parameters. These three models showed satisfactory agreement with the observed data, showing that silicate anions are distributed from monomer to polymer in 2PbO·SiO2 glass and an increase of SiO2 content leads to polymerization of silicate anions to longer chains up to PbO·SiO2 composition, while the chains of PbO3 pyramids remain unchanged. 相似文献
2.
《Journal of Non》2003,315(1-2):77-88
The crystallisation of CaO–ZrO2–SiO2 glasses doped with V2O5 (0.1–5 mol%) has been investigated in terms of microstructure and thermal parameters. Results indicate that crystallisation is predominantly controlled by a surface nucleation mechanism, even though a partial bulk nucleation has been encountered in compositions containing more than 2 mol% of doping oxide. As detected from differential thermal analysis curves, glass transition temperature and crystallisation temperature, are strongly dependent upon V2O5 content varying from 0.0 to 2.0 mol%, while the crystallisation activation energy values decrease with a parabolic trend from B-glass (0.0 mol% V2O5 content, 495±7) to V-0.7 (0.7 mol% V2O5 content, 420±6) composition, increasing again to 442±5 kJ/mol K with higher amount of V2O5. The microstructure of the glass-ceramic materials clearly showed a marked dependence upon the amount of V2O5, also due to the presence of phase separation for content higher than 0.7 mol%. Wollastonite, CaO·SiO2, and a calcia–zirconia–silicate, 2CaO·4SiO2·ZrO2, are the main crystalline phases whose ratio slightly varies with vanadium oxide content. The glass ceramics obtained from the studied materials are greenish and bluish coloured, so it is possible to use the studied glasses as coloured frits for tile glazes. 相似文献
3.
The experiments were carried out on studying the effect of phase separation on nucleation and crystallization in the glass based on the system of CaO–MgO–Al2O3–SiO2–Na2O. In the experiments, TiO2 was chosen as nucleating agent. Three batches of 5, 8 and 10 wt% TiO2 substitution were investigated by the techniques of DSC, XRD, FTIR and FESEM equipped with EDS. XRD and FTIR analysis indicated that the super cooled glasses were all amorphous, the heat treatment leading to nucleation would cause a disruption of silica network which followed phase separation. The phase separation followed the generation of crystal seeds Mg(Ti, Al)2O6. FESEM observation and EDS analysis revealed that the more TiO2 content of glass, the more droplet separated phase and crystal seeds after nucleation heat treatment. The main crystal phase is clinopyroxene, Ca(Ti, Mg, Al)(Al, Si)O6, of crystallized glass. 相似文献
4.
Ternary zinc–calcium-phosphate glasses prepared by classical melting method were characterized through X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) along with energy dispersive X-ray analysis (EDAX), Fourier Transform InfraRed (FTIR) and Raman spectroscopy. The study of these glasses was done in order to supply information regarding their structural particularities since the zinc role in biological environment, especially in the bone, is still under debate.XRD analysis confirmed the vitreous character of the as-prepared samples, while SEM and EDAX measurements indicated the presence of some non-homogeneous domains on their surfaces with approximately similar elemental composition. According to FTIR and Raman spectroscopy, the local structure of glasses up to 10 mol% ZnO is mainly built by Q2 tetrahedrons connected by P–O–P linkages. For 50 mol% ZnO, the modifier role of zinc ions is strongly reflected on the local structure dominated in this case by Q1 pyrophosphate units.The surface reactivity of the samples has been analyzed in vitro by immersion in simulated body fluid (SBF) at 37 °C. XRD, SEM–EDAX, FTIR and Raman methods were employed to characterize the structural changes that occurred on the surface of ZnO–CaO–P2O5 samples reacting with SBF. The X-ray diffraction patterns demonstrated the formation of a hydroxyapatite layer on the samples surface while the other used methods didn't reveal concisely that phenomenon. Based on X-ray measurements, the influence of zinc concentration on the hydroxyapatite layer development was followed. 相似文献
5.
H. Aguiar E.L. Solla J. Serra P. González B. León F. Malz C. Jäger 《Journal of Non》2008,354(45-46):5004-5008
The results of a structural study combining NMR and Raman spectroscopy of several melt-derived glasses in the system Na2O–MgO–CaO–P2O5–SiO2 are presented. The Raman spectra show clear changes in the Si–O–Si vibrational modes (related to the bridging oxygen atoms, BO) and also verify the presence of non-bridging oxygen atoms (NBO), also named terminal oxygens. The intensity of the Si–O–NBO stretching mode depends on the cation concentration. It can be concluded from the NMR studies that the MgO-containing samples have orthophosphate units charge-compensated by Ca2+ and Mg2+. The silicate matrix also contains both types of two-valent cations and consists of Q2 and Q1 units. Similarly, the Na2O-containing samples contain isolated orthophosphate units in a silicate matrix (Q2 and Q3 units), both charge-compensated by mixed cations Ca2+ and Na+. These experimental data were compared with theoretical parameters given by the Stevels model, which is a suitable tool for understanding bioactive behavior of these glasses. Furthermore, results of the in vitro tests carried out in simulated body fluids are presented and compared with both Raman and NMR structural data. 相似文献
6.
The surface modification and crystallization process of BaO–B2O3–SiO2 glass compositions when exposed to CO2 laser irradiation was evaluated as a function of the laser power, irradiation time and surface condition. The glass surface was modified by the application of laser power exceeding 0.40 W and an irradiation time of more than 300 s. Micro-Raman and X-ray diffraction measurements revealed at high laser power the formation of β-BaB2O4 (β-BBO) crystalline phase. The crystallization of the irradiated region was enhanced when β-BBO micrometer sized particles were dispersed on the surface of the glass sample. The intensity of the second harmonic generation observed in the crystallized region was found to depend mainly on the condition of the glassy surface prior to glass irradiation. 相似文献
7.
Komornikov V. A. Timakov I. S. Zajnullin O. B. Grebenev V. V. Makarova I. P. Selezneva E. V. Ksenofontov D. A. 《Crystallography Reports》2019,64(6):984-990
Crystallography Reports - The phase equilibria in the CsHSO4–CsH2PO4–NH4H2PO4–H2O four-component aqueous salt system have been studied. The crystallization ranges and solubilities... 相似文献
8.
Bo Lei Xiaofeng Chen Yingjun Wang Naru Zhao Chang Du Liming Fang 《Journal of Non》2009,355(52-54):2678-2681
A macroporous nanoscale bulk bioactive glass (SiO2–CaO–P2O5 system) was prepared by sol–gel co-template method. Porosimeter analysis showed that the as-synthesized bioactive glasses (BGs) had a porosity of 85% and exhibited a multimodal pore size distribution, nanopores (10–40 nm) and macropores (100 nm–10 μm). Morphological and structural characterizations showed the pores were interconnected with pore walls of about 250 nm in width and 1 μm in length. In vitro bioactivity test indicated that the as-synthesized bulk BGs exhibited faster apatite layer formation capability than the conventional sol–gel BGs. Additionally, the deposited layer was identified as hydroxycarbonate apatite, which is similar to the inorganic part of human bone. 相似文献
9.
In searching for new kind of photoelectric material, chalcogenide glasses in the GeS2–Sb2S3–CdS system have been studied and their glass-forming region was determined. The system has a relatively large glass-forming region that is mainly situated along the GeS2–Sb2S3 binary side. Thermal, optical and mechanical properties of the glasses were reported and the effects of compositional change on their properties are discussed. These novel chalcogenide glasses have relatively high glass transition temperatures (Tg ranges from 566 to 583 K), good thermal stabilities (the maximum of deference between the onset crystallization temperature, Tc, and Tg is 105 K), broad transmission region (0.57–12 μm) and large densities (d ranges from 2.99 to 3.34 g cm?3). These glasses would be expected to be used in the field of rare earth doped fiber amplifiers and nonlinear optical devices. 相似文献
10.
Regularities of phase transformations in glasses of the Li2O–Al2O3–SiO2–TiO2 system doped with up to 2.5 mol% of alkali- and divalent metal oxides were studied by X-ray diffraction analysis, Raman scattering and optical spectroscopy. Ni(II) ions were used as spectral probes of phase transformations because Ni(II)-ions enter the inhomogeneous regions formed during the phase separation and crystallization, and their absorption spectra change with heat-treatment temperature reflecting formation of aluminotitanate amorphous regions, spinel nanosized crystals and β-quartz solid solutions, consequently.It was demonstrated that the technological additives do not change the sequence of the phases' formation but accelerate the liquid phase separation and crystallization. Addition of MgO and ZnO leads to increasing the temperature range of spinel precipitation. Addition of CaO, BaO and PbO results in increasing the light scattering of prepared glass-ceramics.In selection of the technological additives for decreasing the melting temperature of glass-ceramics for optical and photonic applications the influence of the additives on the structure and optical properties of the prepared material should be considered. 相似文献
11.
《Journal of Non》1989,110(1):13-16
Multilayer, wavelength-selective reflecting coatings were prepared by alternate stackings of amorphous zirconia and silica by the sol-gel spinning technique; alkoxide-derived, polymeric sols were used. A detuned, i.e. non-λ/4 stacking system was applied. The spectrum showed a transmission minimum (∼ 4%) at a wavelength of 430 nm, with a bandwidth of 72.5 nm after deposition of the 17th layer. 相似文献
12.
Zhenfeng Zhu Yanbin Zhang Yinpo Qiao Dianguang Liu Bingqing Wang Zhichun Zhang 《Journal of Non》2012,358(12-13):1550-1553
A series of luminescent glasses composed of CaO–B2O3–SiO2 co-doped with cerium oxide (CeO2), terbium oxide (Tb4O7) and samarium oxide (Sm2O3) were prepared by high temperature melting method, aiming to realize the white emitting and tunable luminescent color in the glass matrix. The full colors including blue, green and reddish orange emitting were observed simultaneously in the photoluminescent spectra of ternary Ce/Tb/Sm co-doped CaO–B2O3–SiO2 glasses excited by ultraviolet light. It is shown that the combination of these three emitting allows the realization of white light emitting in ternary co-doped CaO–B2O3–SiO2 glasses. Furthermore, the tunable luminescent color and chromaticity parameters could be realized by varying the content of dopant in the glass matrix, which makes these co-doped glasses good candidates for white light emitting diodes (LEDs). 相似文献
13.
《Journal of Non》2001,279(2-3):204-208
Composition change during the melting process of some glasses in the PbBr2–PbCl2–PbF2–PbO–P2O5 system melted at 450–470°C for 15 min was studied. Results show that there was a remarkable difference between the batch composition and the analyzed composition. Large amount of P, Br, Pb, and Cl were lost mainly in the form of PbBr2, PbCl2 and P2O5. The content of O is influenced by two factors. The incomplete decomposition of NH4H2PO4 or the reaction between P2O5 and H2O in the atmosphere increases the content of O, while the volatilization of P2O5 decreases the content of O. 相似文献
14.
《Journal of Crystal Growth》2003,247(3-4):613-622
The equilibrated grain boundary groove shapes for the commercial purity succinonitrile (SCN) and succinonitrile–carbon tetrabromide (CTB) eutectic system were directly observed. From the observed grain boundary groove shapes, the Gibbs–Thomson coefficients for the solid SCN–liquid SCN and solid SCN–liquid SCN CTB have been determined to be (5.43±0.27)×10−8 Km and (5.56±0.28)×10−8 Km, respectively, with numerical method. The solid–liquid interface energies for the solid SCN–liquid SCN and solid SCN–liquid SCN CTB have been obtained to be (7.86±0.79)×10−3 J m−2 and (8.80±0.88)×10−3 J m−2, respectively from the Gibbs–Thomson equation. The grain boundary energies in the SCN and SCN rich phase of the SCN–CTB system have been calculated to be (15.03±1.95)×10−3 J m−2 and (16.51±2.15)×10−3 J m−2, respectively, from the observed grain boundary groove shapes. The thermal conductivity ratios of the liquid phase to the solid phase for SCN and SCN–4 mol% CTB alloy have also been measured. 相似文献
15.
L.N. Ignatieva N.V. Surovtsev N.N. Savchenko S.V. Adichtchev S.A. Polyshchuk Yu.V. Marchenko V.M. Bouznik 《Journal of Non》2011,357(22-23):3807-3812
The glasses in the MnNbOF5–BaF2–5BiF3–ErF3 system were obtained and their thermal and optical properties were studied. The specialties of crystallization depending on system composition are showed. The glass structure is discussed based on results of the IR and Raman spectra study. During the studies of inelastic light scattering, there revealed a strong photoluminescence, produced by erbium emission, whose intensity depends not only on the erbium trifluoride content in glass, but also on the glass network structure. 相似文献
16.
New chalcogenide glasses from the GeSe2–GeTe–PbTe system were synthesized. The glass forming region was determined using visual, X-ray diffraction and scanning electron microscopy analyses. It is extended towards the GeSe2 and lies partially on the GeSe2–GeTe (0–58 mol% GeTe) and GeSe2–PbTe (20.0–57.5 mol% PbTe) sides. No glasses were obtained in the GeTe–PbTe system. The investigated physicochemical properties vary between 4.04–6.21 g/cm3 (density, d); 97–121 kgf/mm2 (microhardness, HV); ?0.187 ÷ 0.007 (compactness, C) and 14.3–17.8 GPa (elasticity modulus, E), respectively. 相似文献
17.
Development of crystallization in the CaO–Al2O3–TiO2–P2O5 system glasses was investigated in the presence of ionic and metallic silver. Differential thermal analysis, X-ray diffractometry, ultra violet–visible spectrophotometry, atomic force microscopy and scanning electron microscopy were used to evaluate the resulted glasses and glass-ceramics. It was found that silver ions facilitated crystallization by decreasing the viscosity of the glasses. However, metallic silver, which was formed through heat treatment in hydrogen atmosphere, improved heterogeneous crystallization of the reduced glasses in the subsequent heat treatment. The preformed metallic silver led to effective crystallization of calcium titanium phosphate (CaTi4(PO4)6), calcium metaphosphate (Ca(PO3)2) and calcium pyrophosphate (Ca2P2O7) phases at significantly decreased temperatures. The two latter phases were partially dissolved out by leaching in acidic solution and left out a porous structure of calcium titanium phosphate glass-ceramic. 相似文献
18.
Donghui Zhao Xianghua Zhang Hua Wang Huidan Zeng Hongli Ma J.L. Adam Guorong Chen 《Journal of Non》2008,354(12-13):1281-1284
In the present work, thermal properties of GeSe2–As2Se3–CdSe glasses were investigated via DSC measurements. The dependences of glass transition temperature and thermal stability on glass composition were discussed. XRD measurement was also performed to validate the effect of cadmium on the thermal properties of glasses. The calculated Avrami exponent was used to demonstrate the three-dimensional growth of crystals in the glass matrices. The crystallization kinetics for the glasses was studied by using the modified Kissinger and Ozawa equations. 相似文献
19.
A new series of chalcohalide glasses in the GeS2–In2S3–CsI pseudo-ternary system were prepared by conventional melt-quenching method. The glass-forming region was determined and it is mainly situated in the GeS2-rich domain. The glasses have relatively high glass transition temperatures (Tg ranges from 335 to 405 °C) and good thermal stabilities. Based on the Raman spectra, it can be speculated that the glassy net is mainly constituted by [GeS4] and [InS4?xIx] tetrahedra, which are interconnected by the bridging sulfur atoms. And the ethane-liked structural units [S3Ge–GeS3] can be formed because of the lacking of sulfur. Cs+ ion, which was added from CsI, exists as the nearest neighbor of I? ion. 相似文献
20.
V.N. Sigaev N.V. Golubev S.Yu. Stefanovich T. Komatsu Y. Benino P. Pernice A. Aronne E. Fanelli B. Champagnon V. Califano D. Vouagner T.E. Konstantinova V.A. Glazunova 《Journal of Non》2008,354(10-11):873-881
Amorphous nanoheterogeneities of the size less than 100 Å have been formed in glasses of the Li2O–Nb2O5–SiO2 (LNS) and Li2O–ZnO–Nb2O5–SiO2 (LZNS) systems at the initial stage of phase separation and examined by transmission electron microscopy, small-angle X-ray and neutron scattering. Both LNS and LZNS nanoheterogeneous glasses exhibit second harmonic generation (SHG) even when they are characterized by fully amorphous X-ray diffraction (XRD) patterns. Chemical differentiation and ordering of glass structure during heat treatments at appropriate temperatures higher Tg lead to drastic increase of SHG efficiency of LNS glasses contrary to LZNS ones in the frame of amorphous state of samples. Following heat treatments of nanostructured glasses result in crystallization of ferroelectric LiNbO3 and non-polar LiZnNbO4 in the LNS and LZNS glasses, respectively. Taking into account similar polarizability of atoms in LNS and LZNS glasses, the origin of the principal difference in the second-order optical non-linearity of amorphous LNS and LZNS samples is proposed to connect predominantly with the internal structure of formed nanoheterogeneities and with their polarity. Most probably, amorphous nanoheterogeneities in glasses may be characterized with crystal-like structure of polar (LiNbO3) phase initiating remarkable SHG efficiency or non-polar (LiZnNbO4) phase, which do not initiate SHG activity. It gives an opportunity to vary SHG efficiency of glasses in a wide rage without remarkable change of their transparency by chemical differentiation process at the initial stage of phase separation when growth of nanoheterogeneities is ‘frozen’. At higher temperatures, LiNbO3 crystals identified by XRD precipitate in LNS glasses initiating even more increase of SHG efficiency but visually observable transparency is impaired. 相似文献