Photoinduced changes of the rate of dissolution of bilayer films of chalcogenide glasses

The change of the rate of dissolution upon the exposure of bilayer As₃₉S₆₁/As₃₆S₄₄Se₂₀ films to light of wavelength 380 nm and more than 470 nm from the sulfo-selenide layer side has been investigated. Although light of wavelength 380 nm is absorbed in the first layer, in the second layer photoinduced structural changes are observed, which are assumed to occur as a result of the diffusion of electron-hole pairs from the illuminated selenium-containing layer to the nonexposed arsenic sulfide in contact. The excess charge carriers induce structural changes in the As₃₉S₆₁ film that are registered as dissolution rate changes. The calculated value of the drift mobility of the slowest charge carriers (electrons) of 10^?11 cm²/(V s) is in agreement with the literature data. Studies of the Raman spectra of the films of interest confirmed that the diffusion of excess electrons and holes into the sulfide layer resulted in structural changes that manifested themselves in a decrease in the intensities and widths of the bands corresponding to vibrations of structural groups containing homopolar bonds.     

Halogen-containing chalcogenide glasses: Synthesis and properties

Methods for the synthesis of chalcogenide glasses (CGs) containing active and volatile components, in particular, bromine have been developed. The density, volume expansivity, microhardness, refraction index, and magnetic susceptibility of these glasses have been studied. Using the EPR method, the concentration of the intrinsic paramagnetic centers in bromide-modified CGs has been determined.     

High extinction-ratio microstructure fiber based on chalcogenide glasses

Extinction ratio (ER) is one of the important parameters to characterize the polarization-maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled-off extrusion method. The core and cladding material of the fiber are Ge₉As₂₃Se₆₈ and Ge₁₀As₂₂Se₆₈. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid-infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18-cm-long PM fiber for the first time.     

Application of the excited state model to chalcogenide glasses

The limiting displacement of an atom (a group of atoms), which corresponds to the maximum of the interatomic interaction force, is treated as a process of atomic excitation in liquids and glasses. The formation, migration, and disappearance of excited atoms are caused by local fluctuations of the configurational entropy. These processes in chalcogenide (and other) glasses are considered small-scale low-energy processes. The parameters of the excited state model as applied to oxygen-free inorganic systems are analyzed.     

Anodic film studies on nickel under high rate transpassive dissolution conditions

Coulometry and Auger Electron Spectroscopy (AES) were employed to study thickness and composition of anodic films formed on nickel under high rate transpassive dissolution conditions. Nickel anodes were polarized at constant current densities up to 30 A/cm² in alkaline nitrate electrolytes of different nitrate and hydroxyl ion concentration using a flow channel cell with a constant electrolyte flow velocity of 10m/sec. Results show that with increasing current density film thickness goes through a maximum. Nitrogen is detected at the apparent film metal interface in the current region where metal dissolution occurs. No correlation between anodic film thickness and dissolution efficiency is found. The data, together with previous observations, suggest that high rate transpassive dissolution takes place from film free sites.     

Influence of heat treatment conditions on the precipitation and dissolution of lead sulfide nanocrystals in sodium zinc silicate glasses

The influence of the temperature of the primary heat treatment in the case of two-stage heat treatment of glasses on the kinetics of precipitation of PbS nanocrystals and the structure of the glass-ceramic materials prepared has been investigated. The main structural parameters of the glass-ceramic material, such as the radius of lead sulfide nanocrystals, relative volume of the crystalline phase, concentration of nanocrystals, and dispersion of nanocrystal sizes, have been determined under different heat treatment conditions. It has been demonstrated that a variation in the temperature of the primary heat treatment in the range below the glass transition temperature of the glass matrix makes it possible to control the nanocrystal sizes and to obtain close-to-monodisperse size distributions of nanocrystals.     

Ultra-large mode area mid-infrared fiber based on chalcogenide glasses extrusion

We have prepared an ultra-large core, high numerical aperture (NA) chalcogenide (ChG) step-index fiber (SIF) with a mode area of >43 600 μm² at the wavelength of 5.5 μm by an improved extrusion method. The fiber based on two ChG glasses with similar softening temperature has a core diameter of 339.0 μm and ultra-thin cladding. The fiber exhibits a minimum loss of 1.75 dB/m at 9.74 μm and an optical loss of <5.0 dB/m from 5.3 to 10.8 μm. Broadband supercontinuum (SC) covering from 1.2 μm to 13.7 μm has been generated in a 17-cm-long ultra-large mode area fiber with large core and high NA. All these show that, the fiber possesses the potential for high-power infrared laser transmission.     

Effect of doping by transitional elements on properties of chalcogenide glasses

In present work, the results on the influence of doping by transitional elements on thermal, optical, structural and magnetic properties of chalcogenide glasses are presented.Thermal properties (T_g values for undoped and doped glasses) were studied using differential scanning calorimetry technique. Activation energy of glass transition was estimated with the use of Kissinger’s expression. Structural studies were carried with the use of Raman and infrared spectroscopy and X-ray diffraction. Radial electron distribution functions in doped and undoped bulk glasses were obtained and analyzed. In Raman spectra, main observed effect under the introduction of dopants was the change of relative concentration of main and non-stoichiometric structural units characteristic for As₂S₃ glasses. Investigation of influence of transition metals Mn-dopants on the optical properties of As₂S₃ glass was studied in mid-IR region. Pure chalcogenide glasses are diamagnetics. Introduction of transitional and rare earth impurities changes the magnetic properties of investigated chalcogenide glasses.     

Dielectric spectroscopy and dissolution studies of bioactive glasses

The first and rate-limiting step in the degradation of bioactive glasses is thought to be the ion exchange of hydrated protons in the external fluid with alkali metal cations in the glass. The activation energy (E_a) for alkali ion hopping can be followed by dielectric spectroscopy. The replacement of CaO by Na₂O resulted in a reduction in the E_a for ion hopping. In contrast, increasing the glass network connectivity or reducing the nonbridging oxygen content of the glass resulted in an increase in E_a. Substitution of K₂O for Na₂O had little influence on E_a. Mixing alkali metals increased the E_a as expected on the basis of the mixed alkali effect. There was no correlation between the E_a for ion hopping and the dissolution behavior of the glass. Furthermore, the activation energy for Si, Ca Na, and K ion release was found to be approximately a factor of three lower than that for ion hopping suggesting that another rate-controlling mechanism is important in the degradation of bioactive glasses. The presence of a second relaxation process suggested that bioactive glasses undergo amorphous phase separation into silica-rich and orthophosphate-rich phases and the two relaxation processes are due to ion hopping in the two phases.     

Effect of heat treatment on AgI-rich chalcogenide glasses with enhanced ionic conductivity

The glass-ceramics of AgI-based electroconductive chalcogenide system was realized using an appropriate heat treatment at a fairly high temperature (T_g + 40°C) and different times ranging from 4 to 20 hours. The crystallization behavior and electroconductive properties of the heat-treated samples were studied in detail. Transmission study was performed, and the results show that the cut-off edge of the short wavelength is red-shifted at prolonged annealing time but remains an excellent transmittance in the mid-infrared (IR) region. XRD and scanning electron microscopy results indicated that the precipitated crystalline phases are mainly β-/γ-AgI. Moreover, a small amount of α-AgI, which rarely existed at room temperature, is precipitated in the AgI-rich chalcogenide glass-ceramics. The ionic conductivity of all glass-ceramics was enhanced by heat treatment in contrast to that of base glass. Raman analysis exhibited the structure variation in the glass sample after heat treatments. This study provided an observation of crystallization in chalcogenide glass containing large amounts of AgI and be of good guidance to fabricate novel AgI-based chalcogenide glass-ceramics that can be candidates in infrared optics and solid electrolyte applications.     

岩盐溶解速率的研究

在岩盐溶解速率及其影响因素的实验研究基础上,建立了岩盐溶解速率的计算公式。研究的结果可为岩盐开采和其他水溶法矿物开采提供参考。     

Defects of the hypervalent configuration type and their manifestation in properties of chalcogenide glasses

The results obtained in quantum-chemical investigations of defects of the hypervalent configuration (HVC) type in chalcogenide glasses are reviewed for the first time. The similarity and difference between the hypervalent configurations and conventional defects of the valence alternation pair (VAP) type are analyzed. It is demonstrated that the hypervalent configurations are more energetically favorable and, hence, offer advantages in the interpretation of macroscopic (features of structural diffraction, high viscosity of melts, breaking-free mechanism of bond switching upon viscous flow, mechanical strength in the solid state, excess entropy, etc.) and microscopic (electron-optical) glass properties, including the properties traditionally interpreted within double-well potentials and soft atomic configurations. The prospects of the hypervalent configuration model and the ensuing new directions in studies of chalcogenide glasses are considered.     

Defects of the hypervalent configuration type and their manifestation in properties of chalcogenide glasses

The results obtained in quantum-chemical investigations of defects of the hypervalent configuration (HVC) type in chalcogenide glasses are reviewed for the first time. The similarity and difference between the hypervalent configurations and conventional defects of the valence alternation pair (VAP) type are analyzed. It is demonstrated that the hypervalent configurations are more energetically favorable and, hence, offer advantages in the interpretation of macroscopic (features of structural diffraction, high viscosity of melts, breaking-free mechanism of bond switching upon viscous flow, mechanical strength in the solid state, excess entropy, etc.) and microscopic (electron-optical) glass properties, including the properties traditionally interpreted within double-well potentials and soft atomic configurations. The prospects of the hypervalent configuration model and the ensuing new directions in studies of chalcogenide glasses are considered.     

Atomic structure and dissolution properties of yttrium-containing phosphate glasses

We have conducted classical molecular dynamics simulations of three compositions of yttrium-containing phosphate glasses, to study the atomic structure around yttrium, and understand how yttrium incorporation will affect the glass dissolution rate. The Y-O bond length is about 2.2 Å and the coordination number is 6.3. To avoid effects due to different network connectivities, our compositions were chosen to keep the Qⁿ distribution and network connectivity roughly constant, which was confirmed through direct calculation. For these compositions, the structure of the phosphate network is comprised of finite-length chains of PO₄ tetrahedra bound to the network modifiers. We showed that yttrium bonds to 4.2-4.3 of these chains, compared to 3.8 for calcium, and 3.1-3.2 for sodium. This implies that yttrium will bond more parts of the glass to the same place, and therefore, that yttrium incorporation will strengthen phosphate glass against dissolution, making it potentially suitable for radiotherapy applications where a durable glass is required.     

Preparation and refractive index characterization of chalcogenide glasses with gradient refractive index

Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot-pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile.     

搅拌速率及温度对化学镀镍包石墨的影响

通过化学镀的方法在石墨表面镀覆镍层,使用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分别对复合粉末的表面形貌和物相组成进行表征,研究了镀液的搅拌速率及温度对镍包石墨复合粉末表面形貌的影响。结果表明：搅拌速率和温度过低时,镀液反应不完全,复合粉末包覆不完整;过高的搅拌速率和温度会导致镀液自分解,镀层与基体脱离,镀液中存在团絮状的镍;搅拌速率为400 r/min,温度为85℃时,石墨粉末表面可均匀且完整地镀上一层厚度平均在1μm左右的镍镀层。