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1.
Undoped and transition metals (TM 3d)-doped lead phosphate glasses were prepared. Ultraviolet–visible absorption spectra were measured in the range 200–1100 nm before and after successive gamma irradiation. Experimental results indicate that the undoped lead phosphate glass reveals before irradiation strong and broad ultraviolet absorption which is related to the co-sharing of absorption due to both trace iron impurities and lead ions (Pb2+). In the TM-doped glasses, characteristic absorption bands are obtained in both the UV and/or visible regions due to each respective TM ion in addition to that observed by the base undoped UV absorption. Gamma irradiation produces with the undoped glass a prominent induced ultraviolet broad band centered at about 300 nm originating mostly from the contribution of trace iron impurities and the visible spectra reveal markedly high shielding behavior towards successive gamma irradiation, due to the presence of both high content of heavy Pb2+ ions and the sharing of phosphate as a partner. With TM-doped samples, the observed induced bands are virtually varying and related to the type of the sharing TM ions. Infrared absorption spectra reveal in the undoped and TM-doped glasses characteristic structural phosphate groups mainly consisting of metaphosphate and pyrophosphate units. Transition metals are assumed to cause depolymerization of the phosphate glass network with different ratios but the changes in IR spectral data are limited due to the low doping level. Gamma irradiation of the samples is assumed to cause changes in the bond angles or bond lengths of the structural phosphate units within network as evident in the variation of the intensities of the IR bands. 相似文献
2.
Amanpreet Saini Atul Khanna Vladimir K. Michaelis Scott Kroeker Fernando González David Hernández 《Journal of Non》2009,355(45-47):2323-2332
Glass samples from four systems: xPbO–(100?x)B2O3 (x = 30, 40, 50 and 60 mol%), 50PbO–yAl2O3–(50?y)B2O3 (y = 2, 4, 6, 8 mol%), 50PbO–ySiO2–(50?y)B2O3 (y = 5, 10, 20, 30 mol%) and 50PbO–5SiO2–yAl2O3–(45?y)B2O3 (y = 2, 4, 6, 8 mol%) were prepared by a melt-quench technique. Characterization of these systems was carried out using density measurements, UV–visible spectroscopy, differential scanning calorimetry (DSC), and 11B and 27Al magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR). Our studies reveal an increase in glass density with increasing lead(II) oxide concentration in pure lead borates and also with addition of silica into 50PbO–50B2O3 glass. 11B MAS NMR measurements determine that the fraction of tetrahedral borons (N4) reaches a maximum for the glass containing 50 mol% of PbO in the PbO–B2O3 glass series and that N4 is sharply reduced upon adding small amounts of Al2O3 into lead borate and lead borosilicate systems. 27Al MAS NMR experiments performed on glasses doped with aluminum oxide show that the Al3+ are tetra-, penta- and hexa-coordinated with oxygen, even without any excess concentration of Al3+ over charge-balancing Pb2+ cations. [5]Al and [6]Al concentrations are found to have unusually high values of up to 30%. The results of UV–visible absorption spectroscopy, DSC and density measurements support the conclusions drawn from the NMR studies, providing a consistent picture of structure–property relations in these glass systems. 相似文献
3.
Silver–copper alloy-induced crystallization of sputtered a-Si has been studied. In this alloy, Cu acts as a catalyst to accelerate the crystallization, while Ag acts as a new kind of buffer layer, different from Al2O3 and Si3N4, to obtain well-crystallized poly-Si films with short annealing time and free of post-treatment for ohmic contact. When the Cu content is limited to below 30%, Ag can effectively slow down the diffusion of Cu into Si and decrease the Cu–silicide nuclei density to improve the crystalline volume ratio from 80% to over 90%. A 1:4 ratio of Cu to Ag yields the best result. The crystalline volume ratio and Hall mobility reach nearly 100% and 29.4 cm2/V s, respectively. This high quality poly-Si film demonstrates a promising application in solarcells. 相似文献
4.
The effect of lead oxide (PbO) on optical properties of Dy3+-doped PbO–H3BO3–TiO2–AlF3 (LBTAFDy) glasses is investigated. The LBTAFDy glasses were prepared with different PbO contents ranging from 30 to 60 mol%. The Judd–Ofelt intensity parameters (Ωλ = 2, 4, 6) are obtained by the least square fit analysis. It is found that the Ω2 parameter and yellow-to-blue intensity ratio (Y/B) of the Dy3+ emission depend on the PbO content in LBTAFDy glass. The structural asymmetry around the Dy3+ ion and the DyO covalency are responsible for the changes in Ω2 parameter and Y/B ratio. The variation of decay time of 4F9/2 emission level with the PbO content also supports the changes in structural asymmetry and DyO covalency in LBTAFDy glass. 相似文献
5.
Guoping Dong Haizheng Tao Saisai Chu Xiudi Xiao Shufeng Wang Xiujian Zhao Qihuang Gong 《Journal of Non》2008,354(2-9):440-444
Ultrafast third-order optical nonlinearity of Ge–Ga–Ag–S chalcogenide glasses at the wavelength of 820 nm has been measured using femtosecond time-resolved optical Kerr (OKE) technique. The results show that Ge–Ga–Ag–S glasses have large third-order optical nonlinear susceptibility, χ(3) and the response time is also subpicosecond, which are predominantly due to the ultrafast distortion of electron cloud surrounding the balanced positions of Ge, Ga, Ag and S atoms. What’s more, a strong dependence of χ(3) on the composition and microstructure of these glasses was found which shows that [GeS4] and [GaS4] tetrahedra play an important role on the third-order optical nonlinearity. These Ge–Ga–Ag–S chalcogenide glasses would be expected as promising materials applied on all-optical switching devices. 相似文献
6.
Hatem A. Elbatal Zeinab S. Mandouh Hamdia A. Zayed Samir Y. Marzouk Gihan M. Elkomy Ahmed Hosny 《Journal of Non》2012,358(15):1806-1813
This research aims to investigate and compare the structural and the morphological properties of both lithium disilicate glasses doped with copper oxide and their glass–ceramic derivatives. Density measurements were measured for all samples by Archimedes method at room temperature. Differential scanning calorimetric analysis was used to determine the glass transition temperature (Tg) and crystallization temperature (Tc) for all glasses. The glass transition temperature was observed to decrease with increasing CuO concentration indicating the formation of non-bridging oxygen bonds in the glass network. X-ray analysis patterns reveal the appearance of crystalline lithium metasilicate phase as the main phase within the glass–ceramic derivatives, and their crystallite sizes were observed to decrease as the CuO increased. Experimental infrared absorption data indicate the existence of characteristic vibrational bands due to structural building SiO4 units in resemblance to the same vibrations observed from traditional crystalline silicates. Scanning electron microscopic investigations show the vitreous nature for lithium disilicate glasses and the distinct crystalline morphological features for the corresponding glass–ceramic derivatives. 相似文献
7.
The in vitro behavior of xAg2O (100 ? x)[50P2O5 · 30CaO · 20Na2O] glasses (0.14 ? x ? 20 mol%) is investigated in simulated body fluid (SBF) mainly with respect to bioactivity and silver ions release. In order to estimate the biodegradability and bioactivity, the samples were soaked in SBF, which has almost equal ions concentration to those of human blood plasma, and kept at 37 °C for fixed periods of time up to 18 days. After the fixed periods of time analyses were performed on the SBF solutions. Calcium and silver ions concentration of SBF after different soaking times of the glass samples were primarily examined. Conductivity data support the assumption that the released silver ions are reduced in SBF and their release is obstructed by growth of the bioactive layer on the glass surface. X-ray diffraction and infrared analysis attest the development on glass surface of a hydroxyapatite type layer. 相似文献
8.
《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
9.
G.V. Afonin S.V. Khonik R.A. Konchakov N.P. Kobelev A.A. Kaloyan V.A. Khonik 《Journal of Non》2012,358(2):220-223
Effective internal shear stress σi induced by torsional deformation of Zr46(Cu4/5Ag1/5)46Al8 and Zr46Cu46Al8 bulk metallic glasses different by the glass-forming ability of the maternal melts has been determined by measurements of stress relaxation upon stepwise unloading. It has been found that the ratio σi/σ0 (σ0 is the initially applied shear stress) decreases upon increasing the temperature from ≈ 0.8 at T = 450K (T ≈ 0.64 × Tg) to ≈ 0.08 at T = 638K (T ≈ 0.91 × Tg) independently of σ0 and glass composition. The obtained result is in good agreement with earlier data obtained on ribbon metallic glasses. The origin of deformation-induced internal stresses and their connection with deformation mechanisms of metallic glasses has been briefly discussed. 相似文献
10.
I. Kaban P. Jóvári T. Wágner M. Bartoš M. Frumar B. Beuneu W. Hoyer N. Mattern J. Eckert 《Journal of Non》2011,357(19-20):3430-3434
(As0.33S0.67)100-xAgx (0 ≤ x ≤ 28) bulk glasses showing micro-phase separation in a wide concentration range have been studied by X-ray diffraction, neutron diffraction and extended X-ray absorption fine structure measurements. The AsAgS2 composition, which forms a homogeneous glass, is modeled with the reverse Monte-Carlo simulation technique. It is established that Ag prefers the environment of S; Ag―As bonding cannot be observed. Similarly to the AsAgS2 crystalline modifications smithite and trechmannite, the main structural units of the glass are AsS3 pyramids. The covalent network of As and S atoms becomes fragmented in the glassy AsAgS2 unlike in the glassy AsS2. The environment of Ag atoms in the AsAgS2 glass differs from that in the crystalline state. In average, each Ag atom has four nearest neighbors, three of them being S and one being Ag. 相似文献
11.
Glasses in the xEu2O3·(100-x)[4TeO2·PbO2] system where 0 ≤ x ≤ 50 mol% have been prepared using the melt quenching method. The influence of europium ions on the structure of lead–tellurate glasses has been investigated using density measurements, FTIR and UV–VIS spectroscopy. Structural changes produced by increasing the rare earth concentration were followed.The europium and lead ions show a preference towards [TeO3] structural units causing a deformation of the TeOTe linkages. Structural changes inferred by analyzing the band shapes of IR spectra revealed that the increase of the Eu+ 3 content causes the intercalation of [EuOn] entities in the [TeO4] chain network. The excess of oxygen can be supported into the glass network by the formation of [PbOn] and [EuOn] structural units.The UV–VIS spectroscopy data show that europium ions enter the glass matrix in the Eu2+ and Eu3+ valence states, the last being predominant in the studied glasses. The Pb+ 2 ions produce strong absorption in the ultraviolet domain. 相似文献
12.
Ryszard J. Barczyński 《Journal of Non》2008,354(35-39):4275-4277
The conductivity of glasses in the 50WO3–(50 ? x)P2O5–xA2O (A = Na, K, Cs) system has been investigated as a function of composition. It is shown that in tungstenite–phosphate glasses containing different alkali metal ions the conductivity decreases with an increase in the alkali metal ion content. A decrease in conductivity is larger for heavier ions and reaches more than seven orders of magnitude in the case of glass containing Cs2O. This behavior remains in contrast to the literature data on conductivity in transition metal oxide glasses containing alkali metal ions where usually strong conductivity anomalies of several orders of magnitude at certain amount of ions are observed. No necessity of ion–polaron interaction has been pointed out. 相似文献
13.
Weidong Qin Jinshan Li Hongchao Kou Xiaofeng Gu Laszlo Kecskes Hui Chang Lian Zhou 《Journal of Non》2008,354(52-54):5368-5371
The effects of Zn addition on the glass forming ability and mechanical properties of Mg65Cu25?xZnxTb10 (x = 0, 2.5, 5, and 7.5) have been investigated. We show that small amounts of Zn addition improve the glass forming ability, strength, and ductility of the Mg–Cu–Tb bulk metallic glass. For the best glass forming composition, amorphous rods of Mg65Cu20Zn5Tb10 with a diameter of at least 7 mm have been prepared by a conventional copper mold casting method. Additionally, this composition exhibits obvious yielding and plastic deformation upon quasi-static compressive loading. The fracture strength, total strain to failure, and the plastic strain of the Mg65Cu20Zn5Tb10 bulk metallic glass reaches 1025 MPa, 2.05% and 0.15%, respectively. This is significantly superior compared to that exhibited by the original Zn-free Mg–Cu–Tb amorphous alloy. 相似文献
14.
FTIR spectra of three MgO–PbO–B2O3 glass series have been analyzed. There is a decrease in the fraction N4 of four coordinated boron with increasing the MgO content, at the expense of PbO. A new technique has been presented to make use of the N4 data and follow the change in the modifier and former fractions of PbO and MgO. These fractions change markedly, at different rates, with the glass composition. The fraction of modifier MgO is always less than the MgO content, which suggests a former role of this oxide in the studied glasses. The ability of the glass to include MgO increases with increasing PbO content. 相似文献
15.
Adam Strachota Martin Černý Zdeněk Chlup Miroslav Šlouf Jiřina Hromádková Josef Pleštil Hana Šandová Petr Glogar Zbyněk Sucharda Martina Havelcová Jana Schweigstillová Ivo Dlouhý Vladislav Kozák 《Journal of Non》2012,358(20):2771-2782
The optimization of the synthesis of silicon oxycarbide ceramics via the sol–gel/pyrolysis route is described, starting from several alkylalkoxysilanes and vinylalkoxysilanes. The main aim was to achieve low weight losses during cure and pyrolysis and also a compact ceramics morphology. The theoretical composition of the pyrolysates was changed between SiO1.5C and SiO1.2C2.3, by varying monomer types and ratios. An assessment of the real composition was performed using energy-dispersive X-ray spectroscopy. The smallest weight losses were obtained for the resins based on vinyltriethoxysilane and dimethyldiethoxysilane which were additionally modified by the addition of a small amount of boric acid. Somewhat higher weight losses combined with the best toughness were found for resins based on non-vinylated silsesquioxane with a low content on linear dimethylsiloxane units. As an alternative, a precursor (SiO0.9C2.8) was prepared via hydrosilylation, based on cyclic dimethylsiloxane oligomers interconnected to a network, but its weight losses were higher than those of sol–gel silicon oxycarbide. 相似文献
16.
Sherief M. Abo-Naf 《Journal of Non》2012,358(2):406-413
Structure and optical properties of MoO3-doped lead borate glasses which contain high PbO content (60, 70 and 80%) have been studied using Fourier transform infrared (FTIR) and ultraviolet–visible (UV–VIS) spectroscopic tools. FTIR spectra reveal absorption bands which are characteristic for various structural units of borate network, mainly BO3 triangles and BO4 tetrahedra, in addition to the PbOn (where n = 3 and/or 4) structural units. UV–VIS optical absorption spectra reveal broad intense charge transfer UV bands due to Pb2 + ions in the range 320–385 nm. Within this range, molybdenum ions, preferably Mo3 + and Mo5 +, can interfere at about 360–385 nm. Additionally, molybdenum ions give a weak visible band at about 850–860 nm. The optical absorption spectra of the studied glasses show marked resistance to successive gamma irradiation up to 5 Mrad. This shielding behavior can be related to the present high content of the high atomic mass Pb2 + ions. Changes in the atomic structure before and after gamma irradiation are described and explained. 相似文献
17.
18.
Mohammad Mahbubur Rahman K. Rukmani Rajam Sekhar S. Asokan 《Journal of Non》2012,358(12-13):1501-1505
Photo-thermal Deflection (PTD) technique is used to investigate the thermal diffusivity (α) of Ge17Te83 ? xTlx (0 ≤ x ≤ 13) glasses as a function of composition. The thermal diffusivity of these glasses is found to lie in the range 0.020 to 0.048 cm2/s, which is consistent with the memory type of electrical switching exhibited by these samples. Further, it is found that α shows an initial increase with Tl addition, followed by a decrease. The observed composition dependence of thermal diffusivity has been understood on the basis that the thallium atoms are incorporated as a covalent species for lower values of x, increasing the network rigidity; however, they enter as ionic species for higher x values, fragmenting the network. The initial increase in α is due to the increasing network rigidity and the subsequent decrease is because of the fragmentation of the network. Also, there is a strong correlation between the composition dependence of switching voltages observed earlier and the variation with composition of electrical resistivity and thermal diffusivity of Ge17Te83 ? xTlx glasses obtained in the present study. 相似文献
19.
Silvia H. Santagneli Jinjun Ren Matthias T. Rinke Sidney J.L. Ribeiro Younes Messaddeq Hellmut Eckert 《Journal of Non》2012,358(6-7):985-992
Vitreous samples (1-x) AgPO3–x MoO3 (0 ≤ x ≤ 0.5) were prepared by conventional melt-quenching and characterized by Differential Scanning Calorimetry (DSC). The structural evolution of the vitreous network was monitored by 31P solid state nuclear magnetic resonance and Raman scattering, and assignments were aided by corresponding studies on the model compound AgMoO2PO4. The 31P MAS-NMR data differentiate between species having two, one, and zero P―O―P linkages (Q(2) Q(1), and Q(0) species), respectively. Interatomic connectivities involving these units are revealed by two-dimensional INADEQUATE data, utilizing the formation of double quantum coherences mediated by indirect 31P–31P spin–spin interactions via P―O―P linkages. As this method discriminates against isolated P atoms, it also serves as an important spectral editing tool for constraining lineshape fits. 95Mo NMR data and Raman spectra suggest that the Mo species are most likely six-coordinate, forming four P―O―Mo linkages and are otherwise invariant with composition, except at MoO3 contents ≥ 40 mole %, where some Mo―O―Mo bonding and/or clustering is observed. 相似文献
20.
Fang Xia S. Baccaro Hua Wang Wei Hua Huidan Zeng Xianghua Zhang Guorong Chen 《Journal of Non》2008,354(12-13):1365-1368
In this work, multiple effects of γ-ray irradiation on properties of bulk Ge–As–Se chalcogenide glasses were studied. Increased density (ρ), thermal expansion coefficient (α) and decreased optical band gap (Eopt) were observed after irradiation, depending on glass compositions. Glasses with stoichiometric (GeSe2)100?x(As2Se3)x compositions showed linear correlations between As2Se3 proportion x and irradiation sensitivity, which is expressed by Δρ/ρ, Δα/α and ΔEopt/Eopt. Nonstoichiometric glasses (Ge2Se3)100?x(As2Se3)x exhibited irregular variations. The phenomena are discussed in terms of chemical bonds transition and structural evolution under γ-ray irradiation. 相似文献