共查询到20条相似文献,搜索用时 31 毫秒
1.
Dopant-free calcium aluminate glasses are very sensitive to ultraviolet radiation; new optical absorption bands rapidly appear around 400 nm on illumination and are easily bleached when the glass is heated to >100° to 250°C. This coloringbleaching process is reversible when the illumination and heating cycles are repeated, A clear correlation was found between the intensities of the uv-induced optical absorption and the ESR signal of Al-OHC. 相似文献
2.
YOSHIHIRO ABE KOICHI KAWASHIMA SUGURU SUZUKI 《Journal of the American Ceramic Society》1981,64(4):206-209
Coloring and bleaching of reduced phosphate glasses in the systems K2 O-B2 Or Al2 O3 -P2 O5 and K2 O-Al2 O3 -P2 O5 , containing no silver halide, were studied. The as-cast glasses, which are colorless and transparent, become tinged with red when they are reheated at high temperatures for long times. The bleached specimens (PTC-RP glass) are obtained by heating at >600°C, then quenching. The PTC-RP glasses exhibit coloring phenomena by irradiation of light or by heating above 200°C; the colored glasses are again bleached thermally. Coloring of the glasses by heating is described in this paper in terms of phase change within the colloidal phosphorus formed in the glasses. The apparent activation energy for the thermocoloring is estimated to be ∼15×104 J/mol (35 kcal/mol). 相似文献
3.
V. I. Arbuzov M. V. Voroshilova S. I. Nikitina Yu. K. Fedorov 《Glass Physics and Chemistry》2006,32(6):595-603
This paper reports on the results of an investigation into the influence of the purity of the initial materials used for preparing vitreous lead metaphosphate, the acidity of the phosphate matrix, and the contents of additives of Group I–III and V elements and the second glass-former on the location of the UV transmission edge of simple binary and ternary lead phosphate glasses. It is shown that, even for a binary glass of the composition (mol %) 50PbO · 50P2O5, the location of the UV transmission edge can be shifted by ~50 nm on the wavelength scale depending on the purity of the initial reactants. The shift of the UV transmission edge toward the UV spectral range for ternary glasses containing no variable-valence elements other than lead is considerably larger than that for the high-lead phosphate glass of the previously proposed composition involving antimony, niobium, and cerium oxides. It is established that the addition of niobium oxide Nb2O5 to lead phosphate glasses brings about a red shift of the UV transmission edge and a change in the crystallization ability of the glasses. Niobium oxide at a content up to 1.5 mol % increases the crystallization ability of the glass, whereas a change in the niobium oxide content from 1.5 to 3.1 mol % results in a decrease in the crystallization ability. It is demonstrated that the crystallization ability of high-lead phosphate glasses increases at a boron oxide content higher than 5 mol %. 相似文献
4.
Glass formation was observed in the system ZnO-TeO2 in mixtures containing 20 to 40 mole % ZnO. Softening occurred at 350°C and the glasses crystallized at 400°C. High dielectric constants (ca. 20) and high electrical resistivities (ca. 1011 ohm-cm−1 ) were measured. The zinc tellurite glasses have a higher density and refractive index and are considerably softer than silicate glasses. The optical transmission range was between 0.38 and 6.6μ with two absorption bands in the infrared. Spectra of Cu2+ and Nd3+ doped samples are also given. 相似文献
5.
GeSe2 –Ga2 Se3 –CsI chalcohalide glasses are synthesized, and their optical properties and thermo-mechanical properties are studied. A typical characteristic of the glasses is their excellent transparency in the red-light region in addition to the 8–14 μm atmospheric window, which is of vital importance to the quality control of infrared systems. The short-wavelength absorption edge λs of the glass system has a distinct blue shift with increasing CsI content, and the physicochemical interpretations are suggested and formulated. These glasses present a glass transition temperature ( T g ) around 300°C and good thermal stability. Consequently, they can be promising candidate materials for infrared optics, although their hardness is relatively weak. 相似文献
6.
Masayuki Nogami Katsumi Nagaska Etsuro Kato 《Journal of the American Ceramic Society》1990,73(7):2097-2099
The sol–gel process has been applied successfully to the preparation of small-particle-size CdS-doped silica glasses with a significant quantum size effect. Gels prepared through the hydrolysis of a complex solution of Si(OC2 H5 )4 and Cd(CH3 COO)2 ·2H2 O were heated at 500°C, then reacted with H2 S gas to form fine, hexagonal, CdS-microcrystal-doped glasses. The optical absorption edge is blue shifted by ∼0.4 eV compared with the bulk absorption value of CdS crystal. This result is interpreted in terms of a quantum-confinement effect of small crystal size. 相似文献
7.
Xi Du Liaolin Zhang Guoping Dong Kaniyarakkal Sharafudeen Jian Wen Dongdan Chen Qi Qian Jianrong Qiu 《Journal of the American Ceramic Society》2014,97(1):185-188
ZnO–TeO2–P2O5 glasses were prepared by melt‐quenching method. The color of the glass samples changed from colorless to pale red and dark red with increasing TeO2 content. Coloration mechanism and nonlinear optical properties of ZnO–TeO2–P2O5 glasses have been investigated. Raman spectra and transmission electron microscope measurements indicated the precipitation of ZnTe quantum dots in the glasses and ZnTe quantum dots are the origin of coloration. Z‐scan technique was used to examine the nonlinear optical properties of the glasses. The glass sample with 30 mol% TeO2 exhibits large third‐order nonlinear optical susceptibility of 10?11 esu. 相似文献
8.
Two new glass systems based on a range of lead-indium phosphate and lead-scandium phosphate compositions have been developed and characterized. These glasses have a relatively high index of refraction ( n = 1.75 to 1.83) in the visible region and exhibit moderate dispersion (Abbe number ∼30). The ultraviolet absorption edge occurs near 300 nm and the glasses strongly absorb in the infrared at wavelengths greater than 2800 nm. Both glass types can be prepared at relatively low temperatures (900° to 1000°C) and are easily poured down to ∼800°C because of their low melt viscosities. The glasses exhibit good chemical durability and resistance to both weathering and intense γ-radiation. These materials have a glass transition temperature of about 430°C, a softening point of about 460°C, and thermal expansion coefficients in the range of 10.8 × 10−6 to 12.0 × 10−6 /°C. The structure of these phosphate glasses is shown to consist of a distribution of chains of PO4 tetrahedra held together by bonding between the non-bridging oxygens of the tetrahedra and the metal cations. The polyphosphate chain length distribution was determined by a liquid chromatographic technique. Potential aqueous corrosion mechanisms are discussed and some general guidelines for forming a chemically durable phosphate glass are given. 相似文献
9.
Phototropic glasses in which TlCl crystallites play an active role were developed. When glasses containing Tl and Cl were reheated at 420° to 480°C for 3 to 20 h, phototropic glasses were obtained which were transparent, translucent, or opaque, depending on the temperature and time of heat treatment. X-ray powder diffraction patterns of these glasses indicated the presence of TlCl crystallites. The optical absorption in the visible region which developed in the glass after uv exposure was similar to that developed in TlCl crystals prepared by melting TlCl powder. These facts suggest that the phototropy is caused by TlCl crystallites precipitated in the glass by heat treatment. Optical absorption was measured during both darkening and bleaching of the glass. 相似文献
10.
GeSe2 –Ga2 Se3 –KX (X=I, Br, or Cl) chalcohalide glasses are synthesized, and their optical properties and thermo-mechanical properties are investigated. A structural model is put forward to elucidate the interesting compositional dependences of the short-wavelength absorption edge (λs ) and glass transition temperature ( T g ). These glasses are transparent in the red-light region in addition to the 3–5 and 8–14 μm atmospheric windows. Most of their T g exceed 300°C, and they also present good thermal stability. These properties make them attractive materials for infrared optics. 相似文献
11.
Summary A convenient form of instrument has been devised for comparing the color of cottonseed oils with glasses of the Lovibond scale.
In this apparatus each color must be made up by a combination of the same color glasses, one chemist cannot use a single 8.5
red glass and another a 5, a 3, and a 0.5 glass to get the 8.5 match, all are forced to use an 8 and a 0.5 red, superimposed
for this 8.5 reading.
The glasses are protected from dirt and scratches, and are easily revolved into the optical field by the turning of external
nurled wheels.
The total color, yellow + red, when a match is made, is indicated in a straight vertical line upon four concentric dials,
thus diminishing the chances for error in recording the glasses used.
A uniform light source, practically normal daylight, is provided in the instruments which will eliminate lack of agreement
between different laboratories due to the use of various kinds of illumination.
The author wishes to express his indebtedness to Mr. P. F. Ballenger formerly Chief Engineer of the Southern Cotton Oil Co.,
for his assistance in solving the mechanical difficulties incident to the building of this device, for without his help it
would be merely a chemist contraption instead of a finished instrument. 相似文献
12.
Phase relations in the system PbO-GeO2 were determined using the quenching technique. The five compounds detected were: 4PbO-GeO2 , 3PbO-2GeO2 , PbO-GeO2 , and PbO-4GeO2 . The 3:2 and 1:1 compounds melt congruently at 744° and 799°, respectively. The 4:1 compound melts incongruently at 726°C to PbO plus liquid, whereas the 1:4 compound melts incongruently to GeO2 plus liquid at 790°C. The 1:2 compound has a temperature range of stability between 707° and 730°. The data indicate that no liquid immiscibility gap exists in the system. Indices of refraction for glasses in the system were compared with lead silicate glasses. An addition of ∼65%PbO to GeO2 is required to prepare a glass with an index near 2.0 whereas with SiO2 , ∼85% PbO is required. It appears that the lead germanate glasses have higher indices than all other two-component oxide glasses. The addition of PbO to GeO2 decreases the rutile-to-quartz transformation temperature from 1000°C for pure GeO2 to 990°C. Infrared spectra of lead germanate glasses (∼60w% PbO) show that transmission is good up to 5.5μ but decreases drastically between 5.5 and 6.5μ. 相似文献
13.
Shangcong Cheng Chengyu Song Peter Ercius 《Journal of the American Ceramic Society》2020,103(9):4983-4988
To investigate the possible structural differences between silica glass fibers and bulk silica glasses, electron energy loss spectroscopy (EELS) has been used to study the short-range and medium-range structures of both forms of silica glasses. The short-range structure of silica glass, such as the coordination and symmetry, was investigated by the energy loss near edge structure (ELNES) of Si L2,3-edges. The ordering structure in the medium-range was analyzed by the exponential optical absorption edge also known as the Urbach edge of the glasses. The optical absorption data were obtained from the low energy loss spectrum of EELS through Kramers-Kronig analysis. The results show that silica fiber has the same short-range structure as the bulk specimen, but is significantly more disordered than the bulk glasses. 相似文献
14.
Masayuki Nogami Yoichi Goto Yasushi Tsurita Toshihiro Kasuga 《Journal of the American Ceramic Society》2001,84(11):2553-2556
The effect of phosphorus ions on the proton conductivity was examined for the sol–gel-derived glasses. The porous glasses were prepared through hydrolysis of PO(OCH3 )3 and Si(OC2 H5 )4 , in which the phosphorus ions consisted of the POH bonds and were dissolved into the silica matrix without any P-O-Si bond. The electrical conductivity increased in a humid atmosphere and reached ∼30 mS/cm at 50°C under 70% RH. High conductivity is achieved by both the POH bonds and the molecular water bonded to the POH bonds. The conductivity increased with a change in humidity from 40% to 80% RH. The phosphorus ions were selectively dissolved in water, resulting in a lower conductivity. 相似文献
15.
Masayuki Nogami Katsumi Nagasaka Toshiharu Suzuki 《Journal of the American Ceramic Society》1992,75(1):220-223
The sol–gel process has been applied to the preparation of small-sized CdTe-doped silica glasses. Gels synthesized by the hydrolysis of a complex solution of Si(OC2 H5 )4 , Cd(CH3 COO)2 · 2H2 O, and Te were heated from 350° to 600°C in a H2 ─N2 atmosphere to form fine cubic CdTe crystals. The size of CdTe crystals, determined from the line broadening of X-ray diffraction pattern, increases from 4 to 9 nm in diameter with increasing heat-treatment temperature. The optical absorption edge shifts to the higher-energy side as the size of the CdTe crystals decreases. This phenomenon is interpreted in terms of a quantum confinement effect of electron and hole in the CdTe microcrystals. 相似文献
16.
The durability of eight fluoride glasses was tested in liquid water from 25° to 75°C. The studies were done by first growing a corrosion layer and then examining structure and chemistry in cross section with an optical microscope and an electron microprobe. In this way the details of the corrosion behavior could be directly determined. The results indicate that the corrosion process proceeds by a moving boundary, whose penetration rate is diffusion limited. 相似文献
17.
Paul W. Angel Chandra S. Ray Delbert E. Day 《Journal of the American Ceramic Society》1990,73(10):2965-2969
The glass-formation region of the calcia-gallia-silica system was determined. The glasses within this region were measured to have a density of 3 to 4 g/cm3 , a refractive index of 1.6 to 1.73, an Abbe number between 35 and 58, a thermal expansion coefficient of 6.5 × 10−7 /°C to 11.5 × 10−7 /°C, softening temperatures between 730° and 790°C, and a Vickers microhardness of 5.2 to 7.3 GPa. Crystalline phases were identified along the glass-formation boundary. Infrared transmission spectra were used to explain glass structures and their effect on glass properties. The results suggest that the role of calcia in the glass structure is similar to that for calcia in calcium aluminosilicate glasses. 相似文献
18.
Hsiwen Yung P. Y. Shih H. S. Liu T. S. Chin 《Journal of the American Ceramic Society》1997,80(9):2213-2220
Stannous-lead phosphorus oxynitride (Sn-Pb-P-O-N) glasses were prepared by remelting under an anhydrous ammonia atmosphere. Glasses that contained up to ∼4.2 wt% (9 at.%) of nitrogen were obtained. The rate of nitrogen dissolution was studied as a function of remelting time (3–66 h) and temperature (400°–600°C). The onset nitridation temperature was extrapolated to be 315°C; higher nitridation temperatures accelerated nitrogen dissolution. Nitridation of the stannous-lead oxyphosphate (Sn-Pb-P-O) glasses decreased the dissolution rate in water and the thermal expansion coefficient; however, it increased the dilatometric softening temperature, the glass-transition temperature, the microhardness, and the density. The chemical durability of the nitrided glasses increased more than four orders of magnitude with 3.0 wt% of nitrogen content. An increase in the lead oxide content in the stannous phosphate glasses also improved the chemical durability. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggested that nitrogen replaces the terminating hydroxyl ion and the bridging and nonbridging oxygen atoms in the PO4 tetrahedra to form the functional groups –NH<, –N<, and –N=, which leads to enhanced crosslinking of the glass network. Quantitative results regarding these bondings have been given. 相似文献
19.
Sandhya Jayaraman Rukmani Richard K. Brow Signo T. Reis Elke Apel Volker Rheinberger Wolfram Höland 《Journal of the American Ceramic Society》2007,90(3):706-711
The critical cooling rate and fluorescence properties of lithium (Li) disilicate glasses and glass–ceramics, doped with 2.0 wt% CeO2 and with up to 0.7 wt% V2 O5 and 0.3 wt% MnO2 added as colorants, were investigated. The critical cooling rates, R c , of glass melts were determined using differential thermal analysis and were found to be dependent on the relative concentrations of V2 O5 and MnO2 , decreasing from 25±3° to 16±3°C/min. Annealed glasses were heat treated first to 670°C, and then to 850°C to form Li metasilicate and Li disilicate glass–ceramics, respectively. The fluorescence intensities of the Ce-doped glasses and glass–ceramics decrease by a factor of 100 with the addition of the transition metal oxides. This optical quenching effect is explained by the association of the Ce3+ ions with the transition metal ions in the residual glassy phase of the glass–ceramics. 相似文献
20.
D.W. JOHNSON JR. E.M. RABINOVICH J.B. MacCHESNEY E.M. VOGEL 《Journal of the American Ceramic Society》1983,66(10):688-693
The sintering of dried colloidal SiO2 gels, whose preparation and properties are reported in Part I, is described. The effects of various sintering parameters were studied and the conditions for achievement of the best optical quality include the use of: a pretreatment of the SiO2 at ∼925°C, moderate heating rate (∼400°C/h), He+CI2 atmosphere, 1500° to 1600°C sintering temperature, and 1 to 4 h sintering time. Dynamic sintering kinetic studies (heating rate=400°C/h) show that this SiO2 sinters to nearly theoretical density by about 1380°C. However, optical transparency is achieved by removal of minor residual porosity at above 1500°C. Isothermal sintering data fit to a model assuming interconnecting cylinders of SiO2 predict the proper activation energy for the viscosity if initial stages of sintering are considered. Residual porosity in sintered glasses is related to large interstices in the unsintered gel. 相似文献