共查询到20条相似文献,搜索用时 680 毫秒
1.
The synthesis of CuO---Al 2O 3---SiO 2 glasses by the sol-gel method was investigated and the thermal expansion of bulk glasses was measured. Phase separation was observed in these glasses and apparently consisted of a copper-rich dispersed phase and a network former-rich matrix phase. The low thermal expansion coefficient of these glasses was governed by the matrix phase. 相似文献
2.
The linewidth-broadening of the EPR spectra of Cu 2+ in silicate, borate and phosphate glasses was analyzed in terms of the distribution of g| and A| (δ | and δ A|) and related to the distribution of the rigidity of the network structure. X- and K-band spectra were measured for the glasses doped with 63Cu 2+ (93% abundance). The linewidth of the HFS shoulders with parallel orientation to H increased linearly with increasing m or microwave frequency. δ g| and δ A| showed a marked dependence on glass composition. For example, in Na 2O---B 2O 3 glasses, on going from x (mol% of Na 2O) being small through intermediate to large, δ g| varied from small through large to negligibly small. In contrast to these glasses δ g| was extremely large for 75PbO · 25B 2O 3 glass. The large δ g| for the Na 2O---B 2O 3 glassesof intermediate x was attributed to the coexistence of various borate groups competitively coordinating to Cu 2+. Negligibly small δ g| for 70Na 2O · 30B 2O 3 glass and extremely large δ g| for 75PbO ·25B 2O 3 glass, both with a narrower structural distribution, reflect regidity of the glass network. The Pb---O bonding is strong enough to distort the coordination of Cu 2+-complex. The situation is the reverse in Na 2O---B 2O 3 glasses. 相似文献
3.
The formation of high titanium oxide (30–60 wt%) containing glasses was studied. Stable titanate glasses with high content of TiO 2 and BaO could be obtained even without other glass-forming oxides. It is demonstrated that the coloration of titanate glasses with high content of TiO 2 is due to oxygen loss during the melting. A systematic study of controlling melting and heat treatment conditions led to the successful decoloration of titanium oxide containing glasses. Infrared spectra and X-ray diffraction studies showed that Ti 4+ in titanate glasses is in sixfold coordination. Phase separation was observed by electron microscopy when the titanate glasses were heat-treated at the temperature above Tg. The crystallization of titanate glasses is generally preceded by phase separation. The obtained crystalline phases are mainly different titanates. 相似文献
4.
The selective response to Hg 2+, Cd 2+ and Cu 2+ ions was studied for HgS- and CdS---Ge 0.20Te 0.30Se 0.50 and Cu 2Se---As 0.40Se 0.60 glass electrodes. These glass electrodes, containing a suitable amount of the above heavy metals, showed the Nernstian response to the corresponding metal ions. Some metal ions, however, interfered with the selective response. The selectivity of these glass electrodes was found to be connected with the relative position of the Fermi levels of the chalcogenide glasses and redox couples for metal ions. 相似文献
5.
The spectral absorption of Cu 2+ and Ni 2+, the density, molar volume, refractive index, molar refraction, thermal expansion coefficient, transformation and dilatometric softening temperatures of mixed alkali borate glasses are reviewed. These results indicate that in borate glasses, mixed alkalis do not produce gross alterations of the glass network, and that the weak deviations observed may be related to the boric oxide anomaly. 相似文献
6.
Transition metal (TM) ions have been used as colouring agents in the glass industry for a long time. Recently, great attention has been paid to the TM ion doped glasses for the development of new lasers or luminescence materials. The absorption spectra of TM ions in different kinds of glasses have been studied extensively, but little work has been done for fluorescence and relaxation spectra. In this paper emphasis is laid on analysing the influence of chemical bond characteristics of the base glass on the spectra and the site structure of transition metal ions in glasses. Recent experimental results about the luminescence characteristics of low valence ions (such as Ti 3+, Cr 3+, V 2+, Mn 2+, Cu +, Mo 3+) in glasses are also reported. 相似文献
7.
The behavior of copper ions in the Cu 2O·Al 2O 3·4SiO 2 (in moles) glass on heating in air at temperatures up to 500°C was studied. When the glass, in which about 90% of Cu was present as Cu + ions, was heated in air above 300°C, a CuO layer was formed on the surface. The amount of CuO was increased with heating temperature and time, corresponding to the decrease in weight of the glass. Furthermore, the fraction of Cu 2+ ions in the glass increased. These observations suggest that oxygens do not diffuse into the glass, but Cu + ions migrate to the surface from the interior to balance the surplus positive charge produced by the oxidation of Cu + to Cu 2+ ions inside the glass. The following reaction scheme for the formation of the CuO layer was proposed; 2Cu +(interior) + 21O 2(surface) → Cu 2+(interior) + CuO(surface). 相似文献
8.
以石墨烯和自制TiO 2粉末为原料,通过两步水热法联合真空抽滤法制备还原氧化石墨烯/TiO 2纳米线(rGO/TiO 2 NWs)复合膜。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、拉曼光谱对rGO/TiO 2 NWs复合膜的形貌、结构进行表征。研究结果表明,还原氧化石墨烯和TiO 2 NWs成功地复合在一起,复合材料中TiO 2 NWs分散性较好。Cu 2+吸附实验结果表明,复合材料中TiO 2 NWs所占比例、pH值是影响Cu 2+吸附效果的重要因素,研究复合材料对Cu 2+的吸附效果应该在pH值为6.0的近中性环境。其中TiO 2 NWs含量为50%时,复合膜对Cu 2+的吸附量最高,达到rGO薄膜的4倍。复合薄膜有较好的吸附稳定性,重复使用5次后,吸附率是原吸附量的91%。 相似文献
9.
The influence of phase separation and crystallization on the internal friction of some oxide glasses is reviewed and discussed. In alkali-containing glasses, the internal friction peak caused by stress-induced diffusion of alkali ions decreases in magnitude and shifts to higher temperature slightly due to phase separation. And in alkali-free glasses phase separation only exerts a minor decrease upon the background of internal friction curves, whereas crystallization influences the internal friction of these glasses more strongly. Because of crystallization, in alkali-containing glasses alkali ions might diffuse in a residual glass phase and a crystal phase, respectively. This might cause corresponding internal friction peaks. And in alkali-free glasses, no evident internal friction peak is observed. However, the author found a high and wide internal friction peak at about 100°C in the crystallized MgO·Al 2O 3·SiO 2·TiO 2 and ZnO·Al 2O 3·SiO 2·ZrO 2 glasses. The peak occurring in the two glasses studied is probably connected with glass crystallization and crystallized crystals. 相似文献
10.
The Ge 25Ga 5Se 70 and Ge 30Ga 5Se 65 pure and Pr 3+-doped glasses were prepared by direct synthesis from elements and PrCl 3. It was found that up to 1 mol% PrCl 3 can be introduced in the Ge 25Ga 5Se 70 and Ge 30Ga 5Se 65 glasses. Both types of glasses with overstoichiometric and substoichiometric content of Se were homogeneous and of black color. The optical energy gap is Eoptg=2.10 eV, and the glass transition temperature is Tg=543 K for Ge 25Ga 5Se 70 and Tg=633 K for Ge 30Ga 5Se 65. The long-wavelength absorption edge is near 14 μm and it corresponds to multiphonon processes. Doping by Pr 3+ ions creates absorption bands in transmission spectra, which can be assigned to the electron transitions from the ground 3H 4 level to the higher energy levels of Pr 3+ ions 3H 5, 3H 6, 3F 2, 3F 3 and 3F 4, respectively. By excitation with YAG:Nd laser line (1064 nm), two intense luminescence bands (1343 and 1601 nm) were excited. The first band can be ascribed to electron transitions between 1G 4 and 3H 5 energy levels of Pr 3+ ions. Full width at half of maximum (FWHM) of the intensity of luminescence was found to be 70 nm for (Ge 25Ga 5Se 70) 1 − x(PrCl 3) x and (Ge 30Ga 5Se 65) 1 − x(PrCl 3) x glasses. The FWHM in selenide glasses is lower than in halide and sulphide glasses. The second luminescence band (1601 nm) can be probably ascribed to the transitions between 3F 3 and 3H 4 energy levels of Pr 3+ ions. The absorption and luminescence spectra of Pr 3+ ions in studied glasses are slightly influenced by stoichiometry of glassy matrix. The Raman spectra of studied glasses were deconvoluted and assignment of Raman bands to individual vibration modes of basic structural units was suggested. The structure of studied glasses is mainly formed by corner-sharing and edge-sharing GeSe 4 tetrahedra. The vibration modes of Ga-containing structural units were not found, they are apparently overlapping with Ge-containing structural units due to small difference between atomic weights of Ge and Ga. In the glasses with substoichiometry of Se, the Ge–Ge bonds of Ge 2Se 6 structural units were found. In Se-rich glasses the Se–Se vibration modes were found. In all studied glasses also ‘wrong' bonds between like atoms were found in small amounts. Maximum phonon energy of studied glasses is 320 cm −1. 相似文献
11.
The glass-forming region in the BiO 1.5---BaO---CuO system was determined, and the structure and crystallization of the glasses were investigated and compared to glasses containing CaO or SrO in place of BaO. It has been found that the glass-forming region in this system is wider than those in the BiO 1.5---CaO---CuO and BiO 1.5---SrO---CuO systems. BaBiO 2.77 was preferentially formed in the first stage of crystallization at all glass compositions. It is suggested that the Ba 2+ ions may preferentially occupy the sites near BiO 6 octahedra, while the Ca 2+ ions in BiO 1.5---CaO---CuO glasses may not have a site preference with respect to the BiO 6 octahedra. 相似文献
12.
The short range structures of B 2O 3 (90 mol%)---Cs 2O (10 mol%) and B 2O 3 (80 mol%)---Cs 2O (20 mol%) liquids were analyzed at 973 and 1053 K, respectively, by an X-ray diffraction method, and the effects of Cs 2O addition on the boron-oxygen bonding were investigated. The existence of BO 3 triangles, which form the so-called boroxol ring structure, was confirmed in B 2O 3---Cs 2O liquids, as well as in B 2O 3 liquid, but some fraction of the BO 3 triangles was thought to be converted to BO 4 tetrahedra. Similar results have previously been observed also in B 2O 3---Cs 2O glasses. A Cs atom was found to be surrounded by six O atoms; four Cs---O interatomic distances were about 3.2 Å but the other two were at 3.8–3.9 Å. These distances indicate that distorted Cs---O octahedra may exist in these B 2O 3---Cs 2O liquids. 相似文献
13.
The colorless and transparent glasses in the Al 2O 3---B 2O 3---SiO 3 system with high B 2O 3 and SiO 2 content were prepared from gels at low temperature. Their IR spectra not only revealed the evolution of the gel to glass conversion, but also showed that the formation of mixed bonds in the glasses obtained did not show any effect due to the B 2O 3 content. The accuracy of the glass composition is dependent upon the SiO 2/B 2O 3 molar ratio. The higher the ratio, the less the deviation of the analyzed compositions of the resulting glasses from their original calculated values. It is obvious that the higher the ratio, the lower the thermal expansion coefficient and the higher the transformation temperature of the glass, and the temperature at which the thermal contraction reaches an equilibrium is higher. 相似文献
14.
Raman spectra were measured of rapidly quenched glasses and the corresponding liquids in binary and ternary (pseudobinary) systems composed of Li 2O and several glass-forming oxides such as B 2O 3, P 2O 5, and/or SiO 2. The fractions of the various structural units present were determined from the deconvoluted Raman peaks. Glasses with large amounts of Li 2O were composed of discrete structural units such as ortho-oxoanions and pyro-oxoanions. Based on these data the structural units in the glasses and the corresponding liquids were identical, although in some cases those in the corresponding crystals were different. In the pseudobinary systems combining pyro-oxosalts of lithium borate, phosphate and silicate, non-bridging oxygens were preferentially formed at the phosphate structural units rather than at the borate or silicate structural units. This order of preference was consistent with that of the acidity of the glass-forming oxides in the liquids. 相似文献
15.
The properties and concentrations of oxygen-deficient type structural defects in type III SiO 2 glasses implanted with Ti +, Cr +, Mn +, Fe +, or Cu + to doses from 0.5×10 16 to 6×100 16 ions/cm 2 at an energy of 160 keV have been measured by using vacuum UV and EPR spectroscopies. An intense absorption band centered around 7.5 eV is observed in all the samples except for Cu-implanted ones and is attributed primarily to Si---Si homo-bonds with the bond distance close to that of the Si 2H 6 molecule. The homo-bond and implanted ion concentrations are of the same order of magnitude in the implanted layers. An E′ type center associated with the homo-bond is observed in all the samples except for Cu-implanted ones. Anomalous behaviors of the Cu-implanted samples are attributed to the formation of Cu-colloids. An enhanced formation of metallic particles or colloids is suggested for the samples implanted with Cr, Mn or Fe to doses higher than 3×10 16 ions/cm 2. 相似文献
16.
以处理后的脱硫石膏为原料,在H 2SO 4-H 2O体系中以Cu(NO 3) 2为晶形控制剂采用水热法制备脱硫石膏晶须,探讨了Cu(NO 3) 2对脱硫石膏晶须生长的影响机理。结果表明:Cu(NO 3) 2对脱硫石膏有明显促溶作用,其中Cu 2+可减小溶液中各离子的活度系数,使溶液中的Ca 2+浓度增大。NO -3通过静电作用在Ca 2+周围聚集并对SO 2-4产生屏蔽作用,导致脱硫石膏继续溶解并使Ca 2+和SO 2-4的浓度处于相对稳定状态,有利于半水脱硫石膏晶体的形核与生长。此外,Cu 2+还可在晶须的生长过程中选择性吸附在晶须表面,生成CuSO 4,促进了脱硫石膏的结晶生长,最终在Cu(NO 3) 2用量为2.0%(质量分数)时制备的脱硫石膏晶须长径比约为73。 相似文献
17.
A series of titania-silica glasses with 0–9% TiO 2 were fabricated using a sol/gel process. The sol was prepared by dispersing colloidal silica fume in an aqueous solution of titania which was synthesized through the acid-catalyzed hydrolysis of titanium isopropoxide. The sols gelled in 2–4 days, and then were dried for 6–8 days. The dry gels were sintered at 1450–1500°C to produce clear, dense, microstructure-free glasses. The gels underwent a total shrinkage of 50% to yield glass rods about 50 mm long and 5 mm in diameter, or glass discs about 4 cm in diameter and 5 mm thick. The drying step was most critical in the production of crack-free specimens. In the gel, the transmission electron microscope (TEM) revealed the presence of 1–5 nm rutile microcrystallites uniformly distributed within a network of colloidal silica particles. After sintering to 1450–1500°C, though, a dense, transparent, microstructure-free glass was created. Fourier transform infrared spectroscopy (FTIR) verified the formation of an amorphous solid-solution of titania and silica after sintering. The thermal expansion of the glasses was measured using a differential dilatometer. The average linear coefficients of thermal expansion (CTE @ 25–675°C) varied between +5 × 10−7 and −0.2 × 10−7°C−1 in the range 0 to 9% TiO2. The glass with 7.2% TiO2 exhibited a zero thermal expansion coefficient at 150–210°C. The hysteresis in CTE on heating and cooling was of the order of 0.01–0.02 ppm. 相似文献
18.
Ag +/Na + ion-exchanged R 2O–Al 2O 3–SiO 2 glasses with uniform concentration profile of Ag + and Na + were prepared by heat treatment in molten silver salt followed by holding at the same temperature in an ambient atmosphere. Their glass transition temperature ( Tg) and thermal expansion coefficient (TEC) were measured and structures were investigated using 29Si-MAS NMR, 27Al-MAS NMR, IR and Raman spectroscopies. Both Tg and TEC decreased with increase of the exchange ratio, but Tg was still above the ion-exchange temperature of 400°C even for the fully exchanged sample. The 29Si- and 27Al-MAS NMR spectra were mostly unchanged and no sign of the structural alteration of the glass network was observed. On the other hand, the vibrational spectra showed remarkable peak shifts depending on the exchange ratio. From these structural results, it was found that when the exchange ratio was low, the introduced Ag + ions were stabilized at the non-bridging oxygen (NBO) site, and then Na + ions in AlØ 4 site were exchanged by Ag + ions after full replacement of NBO sites, where Ø represents the bridging oxygen. 相似文献
19.
The properties and structure of (45 - x)RO · xNa 2O · 2.5Al 2O 3 · 52.5P 2O 5 (R = Mg, Ca, Sr, Ba, 0 x 31 mol%) glasses were investigated. The variation in the molar volumes of glasses in the MgO series is closely related to the formation of the end groups in the glasses with the substitution of Na + ions for Mg 2+ ions, resulting in a variation of the density and refractive index of the glasses. The properties of glasses containing CaO in terms of Na 2O substitution depend mainly on the low field strength of Na + ions substituting for CaO even though the end groups occurring in the glasses increased. The variation in properties of the glasses containing SrO and BaO, some of which were substituted by Na 2O, could be explained by differences in masses, field strength and polarizability between the Na + ions and the alkaline-earth ions due to a small variation in the structure of the glasses despite Na 2O substitution. 相似文献
20.
Glasses with compositions xCuO·(100 − x)SiO 2 and 5R nO· xCuO. (95−x)SiO 2, where R = Li, Na, Ca and X = 0.25–10, were prepared by the sol-gel method. Samples were thermally treated between 60 °C and 1000 °C in oxidizing and reducing atmospheres. Copper incorporation was studied by spectrophotometry, X-ray diffraction and TEM. All the samples are transparent and present a bluegreen colour at 600 °C in oxidizing atmosphere. The obtained results prove that copper is mainly incorporated as Cu2+. At higher temperatures all the samples present -cristobalite, the samples containing Li2O or CaO also show -quartz as crystalline phases. In reducing atmosphere particle segregation takes place, producing in some cases opaque materials. Under specific conditions, transparent ruby glasses were obtained. 相似文献
|