The vibrational spectra of B2O3-GeO2 glasses

Infrared and Raman spectra were measured for a series of glass compositions in the binary B₂O₃-GeO₂ system at room and elevated temperatures. No coordination changes were detected from spectral analysis for either boron or germanium with concentration or temperature changes. Interpretation of the vibrational spectra indicated that both boroxol rings and BO₃-triangular units were present as the basic units in glasses with higher B₂O₃ concentrations. Only BO₃-triangular units were detected as the basic units in glasses with lower B₂O₃ concentrations. Raman spectra of glasses measured at higher temperatures (>T_g) indicated that their boroxol ring concentrations decreased as a function of temperature. The enthalpy for ring rupture in 35GeO₂–65B₂O₃ glass was 7.7 kcal/mol. Also, spectral analysis indicated that the boroxol ring concentrations of these glasses at room temperature were dependent upon their previous heat treatments.     

EPR and magnetic susceptibility studies of B2O3–Bi2O3–Gd2O3 glasses

Glasses of the xGd₂O₃ · (100 − x)[B₂O₃ · Bi₂O₃] system with 0.5 ⩽ x ⩽ 10 mol% were studied by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. Data obtained show that for low gadolinium oxide contents of the samples (x ⩽ 3 mol%) the Gd³⁺ ions are randomly distributed in the host glass matrix and are present as isolated and dipole–dipole coupled species. For higher gadolinium oxide contents of the samples (x > 3 mol%) the Gd³⁺ ions appear as both isolated and antiferromagnetically coupled species. The EPR spectra of the glasses reveal resonance sites with an unexpected high crystalline field in addition to the ‘U’ spectrum, typical for Gd³⁺ ions in disordered systems. This absorption line is due to Gd³⁺ ions that replace Bi³⁺ ions from the host glass matrix and could play the network unconventional former role in the studied glasses.     

Thermal expansion and transition temperature of glasses in the systems BeO–Al2O3–B2O3 and MgO–Al2O3–B2O3

Researches were conducted for glasses in the systems BeO–Al₂O₃–B₂O₃ and MgO–Al₂O₃–B₂O. The following characteristics have been determined: thermal expansion coefficient within 20–300 °C, structural thermal expansion coefficient (STEC) and glass transition temperature. The discussed properties of Be-aluminoborate and Mg-aluminoborate glasses have been compared with those of Ca-, Sr- and Ba-aluminoborate glasses. TEC of studied glasses gets higher going from Be-aluminoborate glasses to Ba-aluminoborate ones, but T_g decreases under the same succession. The dependence of STEC on the nature of a given cation is more complicated. The pattern of dependence of the properties on composition is due to changing the boron coordination number with respect to oxygen, which is the main network-former, and to competition between the aluminium and boron for the oxygen brought by an ion-modifier. The difference between the effect of one ion-modifier and that of another is determined by decreasing the radius of an ion and increasing its electric field strength in the succession from Ba²⁺ to Be²⁺. The ions of Be and Mg can also act as network-former to some extent.     

Characterization studies of AgIAg2OMoO3 glasses

Glass formation has been investigated in the system AgIAg₂OMoO₃. X-ray absorption edge chemical shifts, infrared spectra and heat capacities of the various glass compositions have been measured. The probable anion structures in the oxygen excess and deficient regions have been discussed.     

Thermal and optical properties of glasses of the system Bi2O3 – B2O3

In the binary system Bi₂O₃ – B₂O₃ glasses were prepared in the composition range 57.5 mol% ‐ 80 mol% B₂O₃ by defined slow cooling of large melt samples (about 75 cm³, each). Temperatures of crystallization, of melting and of glass transition were determined and density data of the glasses were derived using the hydrostatic weighting method. Thermal expansion coefficients and high precision refractive indices, together with their dispersion, were measured. The measured physical properties indicate subtle discontinuous structural changes of the glasses with glass composition, that match with the ranges of existence of the crystalline compounds of the binary system Bi₂O₃ – B₂O₃. Thermal investigations together with X‐ray powder diffraction analyses of crystallized glass samples prove the so far doubtful existence of a borate compound named “BiBO₃” in the PDF within the composition range 52.5 – 57.5 mol% B₂O₃.     

Effect of composition on ionic transport in SiO2–B2O3–Na2O glasses

Ionic diffusion was investigated in the SiO₂–B₂O₃–Na₂O glass system over a wide composition range by impedance spectroscopy measurements. The Na⁺ cation transport mechanism was described by an interstitial pair migration model based on Frenkel defects in ionic crystals. The activation energy of the static electrical conductivity is shown to be correlated with the boron coordination number in these glasses. Published ¹¹B NMR results were used to calculate the activation energies of sodium cations acting as charge compensators for the [BO_4/2]⁻ tetrahedron and of sodium cations bonded to non-bridging oxygen atoms. These values are in agreement with the activation energies of the Na₂O–B₂O₃ and Na₂O–SiO₂ binary systems, respectively.     

Thermal and optical properties of CuO–BaO–B2O3–P2O5 glasses

CuO-doped barium borophosphate glasses in a series of xCuO–(45 − x)BaO–10B₂O₃–45P₂O₅ in molar ratio with x = 0–15 mol% were prepared by a melt-quenching technique. All the glasses had excellent thermal stability against crystallization. Glass transition temperature, thermal expansion coefficient and molar volume decrease with increasing CuO concentration. The linear relationship between the absorption coefficient and CuO concentration exists for a peak wavelength in the transitions of ²A_1g → ²B_1g, ²B_2g → ²B_1g, ²E_g → ²B_1g. The relationship between the properties and glass structure evaluated by Raman spectroscopy is discussed.     

Low-temperature heat capacity of GeO2 and B2O3 glasses: thermophysical and structural implications

The heat capacities of rapidly quenched B₂O₃ and GeO₂ glasses have been measured by adiabatic calorimetry from less than 10 to 350 K. The residual entropies at 0 K obtained from these new results and ancillary data are 11.2±0.8 and 6.6±1.1 J/mol K for B₂O₃ and GeO₂ glasses with fictive temperatures of 980 and 543 K, respectively. On a g atom basis, both of these entropies are similar to the low value found previously for SiO₂ glass. For B₂O₃, this is likely due to the small contribution of boroxol groups to the topological entropy of the glass. The importance of the Boson peak increases in the order SiO₂, GeO₂, B₂O₃ which corresponds to the order of decreasing glass transition temperatures. Some implications about short- and medium-range order are finally drawn from these results and the differences between the glass and crystal phases of the three oxides.     

三维Ag2O/WO3复合催化剂的制备及光催化性能研究

WO3是一种带隙约为2.7 eV的过渡金属半导体,可见光就能激发其光催化活性,这极大地提高了太阳光的利用率,但纯WO3纳米材料催化活性偏低,针对这一难题,本文选取了三维网格结构的WO3纳米材料为载体,利用化学搅拌法制备了不同摩尔比的Ag2O/WO3复合光催化剂.选择亚甲基蓝为研究对象,测定了不同摩尔比的Ag2O/WO3复合催化剂的光催化性能.实验表明,当Ag2O和WO3的摩尔配比为1∶2时,该复合催化剂的光催性能最好.过量的Ag2O纳米颗粒会增加Ag2O/WO3内部电子空穴的复合几率,反而导致光催化剂反应活性的降低.     

Effect of ZnO and Bi2O3 addition on linear and non-linear optical properties of tellurite glasses

Glasses in the system TeO₂-Bi₂O₃-ZnO were studied with respect to their linear refractive indices and optical absorption in the UV-vis range. The third order non-linear refractive indices were measured using degenerated four wave mixing (DFWM). The optical Kerr susceptibilities calculated hereof were in the range from 5.49 to 6.58 × 10⁻¹³ esu and hence 34-41 times larger than that of fused SiO₂. They are roughly proportional to values theoretically calculated by the theory of Lines.     

Calorimetric studies of AgI-doped tellurite glasses

The heat capacity changes during the glass transition of TeO₂---TlO_0.5 glasses containing AgI or (AgI)_0.75(TlI)_0.25 up to mole fractions of 0.4 or 0.55 have been measured by differential scanning calorimetry. The glass transition temperatures of the binary compositions decrease with increasing TlO_0.5/TeO₂ ratio. With rising Ag⁺ concentration, the cohesion of the glass network is weakened and the structural contributions to the relaxation phenomenon as well as its activation enthalpies diminish. There is no interaction between the iodide in probably crystalline form and the host glass network. Compared with binary and ternary silver tellurite glasses, the corresponding thallium tellurite compositions are less stable.     

Kerr studies of several tellurite glasses

Estimates of Kerr electrooptical sensitivity of several tellurite glasses are presented. The highest value of Kerr coefficient B ～ 190 × 10^?16 m V^?2 is registered for 0.6TeO₂–0.3TlO_0.5–0.1ZnO glass. This evidences the prospects of thallium–tellurite glass system for electrooptical applications. A gradual decrease of B from 41 × 10^?16 to 26 × 10^?16 m V^?2 in (1 ? x) TeO₂ – xNbO_2.5 system is revealed for x increasing from 0.1 to 0.15. No crystalline phase was found in that system, thus allowing attributing its Kerr sensitivity to the intrinsic properties of the glass matrix. The Kerr coefficient variation from 66 to 81 × 10^?16 m V^?2 was observed for 0.85TeO₂–0.15WO₃ glasses co-doped with small amounts of silver and cerium. The analysis of optical absorption spectra of several silver-containing tellurium–tungsten oxide glasses makes it possible to think that introducing cerium provokes formation of new mid-range orderings.     

Enhancement of optical birefringence in tellurite glasses containing silver nanoparticles induced via thermal poling

Wavelength-selective enhancement of optical birefringence has been observed in a tellurite glass containing silver nanoparticles (Ag NPs) induced via thermal poling. The birefringence appears as an optical rotation of linearly polarized light; a large optical rotation is observed at around the wavelength of localized surface plasmon resonance (LSPR) of Ag NPs. The optic axis is oriented along the electric field applied during the thermal poling, suggesting that birefringence induced in the glass matrix through the thermal poling is drastically enhanced by the NPs at around the LSPR. Because of the birefringence of the matrix, the wavelength of LSPR shifts depending on the polarization state of the incident light, which in turn induces the polarization dependence of the real part of the refractive index via the Kramers–Kronig relation.     

The effects of ZnCl2 and ErCl3 on the vibrational spectra and structure of tellurite glasses

A series of zinc tellurite glasses, containing up to 40 mol% ZnCl₂ and doped with 1–10 mol% ErCl₃, was prepared by melting and casting and their structure was analyzed by polarized Raman and variable incidence infrared reflection spectroscopies. Kramers–Kronig analysis of the infrared reflectivity led to the identification of the vibrational mode components. The Raman spectra are dominated by an intense, depolarized boson peak at ∼45 cm⁻¹ and a high frequency, polarized peak at ∼767 cm⁻¹. The introduction of ZnCl₂ and ErCl₃ modifiers led to a blue shift of the high frequency peak, while the intensity of the boson peak was found to increase continuously with the Er³⁺ content. It is shown that the erbium and zinc compounds both break TeOTe bonds, introducing non-bridging chlorine species, connected mostly to the zinc atoms.     

Al2 O3晶型对K2 WO4/Al2 O3物化性质及催化合成甲硫醇的影响

采用等体积浸渍法改性制备了K2 WO4/Al2 O3催化剂,研究了载体Al2 O3晶型对K2 WO4/Al2 O3催化剂物化性质及催化合成甲硫醇的影响.借助XRD、SEM、EDS、BET及NH3/CO2-TPD等手段对不同催化剂的晶相组成、微观形貌、孔结构及表面酸碱性质进行了表征分析.结果表明,Al2 O3晶型对K2 WO4/Al2 O3催化剂晶相组成及微观形貌影响较小,但对孔结构及表面酸碱性质影响较大.与K2 WO4/η-Al2 O3和K2 WO4/θ-Al2 O3催化剂相比,K2 WO4/γ-Al2 O3催化剂具有更大比表面积及孔容(介孔比表面积为226.75 m2·g-1,总孔容为0.557 cm3·g-1),且表面仅有弱酸和弱碱中心(弱酸浓度为0.42521 mmol·g-1,弱碱浓度为0.44184 mmol·g-1).在反应温度370℃,反应压力1.0 MPa,H2 S流速4.9 mL·min-1,CH3 OH流速0.03 mL·min-1反应条件下,K2 WO4/γ-Al2 O3催化剂表现出优良催化性能,甲醇转化率和甲硫醇选择性分别达81.58;和87.05;,与K2 WO4/η-Al2 O3和K2 WO4/θ-Al2 O3催化剂相比,甲醇转化率分别提高了4.23;和19.42;,甲硫醇选择性分别提高了14.68;和7.85;.