Glass Physics and Chemistry最新文献

Foam glass based on waste glass is one of the most important ecological construction materials due to its thermal, acoustic and electromagnetic insulation powers. This work aims to study the effect of Na₂SiO₃ on the characteristics of foam glass made from soda-lime waste glass using CaCO₃ as a foaming agent. Foam glass samples were prepared by sintering at a temperature of 850°C for 10 min with a heating rate of 6.5°C/min. The first sample contains 99 wt % waste glass powder and 1 wt % CaCO₃, and the other samples were developed by replacing a quantity of glass powder with 10, 20, 30 and 40 wt % of Na₂SiO₃. The effect of this substitution on the properties of foam glass was studied using a scanning electron microscope (SEM), a differential thermal analysis (DTA), a thermal gravimetric analysis (TGA), Fourier-transform infrared analysis (FTIR), thermal insulation and mechanical strength tests. Experimental results showed that the addition of Na₂SiO₃ increases the porosity of foam glass giving it a very low thermal conductivity (0.026 Wm^–1 K^–1) by thus increasing its power of thermal insulation.

Compositions and a methodology for manufacturing composite materials for remote photoluminescent converters of LED radiation based on quartz glass and ultrafine powders of yttrium–aluminum garnet activated by cerium ions (Y₃Al₅O₁₂:Ce³⁺) are developed. The conditions for the synthesis of garnet by the method of thermochemical reactions (combustion) of nitrate salts in citric acid are optimized, and agglomerated powders with primary particle sizes of 0.8–12.3 μm are obtained for the reaction with a deficiency of acid and in the range from 49 to 207 nm for synthesis under conditions of excess citric acid. The physicochemical, structural, and spectral-luminescent characteristics of powdered samples and quartz glass–low-melting glass–phosphor composites formed at low sintering temperatures (650–700°C) are studied. It is shown that when the composite plate is illuminated with a blue LED (λ_max = 455 nm), a spot of white light is visually recorded, formed from a combination of scattered blue radiation and yellow radiation excited in YAG:Ce³⁺ particles (λ_max = 560 nm).

The phase equilibria in two three-component and one four-component salt systems based on potassium salts are studied. The influence of lower dimensional systems on the final appearance of the four-component system is shown.

During the synthesis of ZnS:Cu,Br phosphors (zinc sulfide activated by copper and bromine ions), a composite wurtzite–sphalerite structure is formed, and the luminescence intensity and the content of luminescence centers in the form of donor–acceptor pairs of Cu_Zn–Br_S reach a maximum at a certain proportion of the wurtzite phase in the phosphor. This is confirmed by the study of the phase composition of the synthesized phosphors and changes in the radioluminescence spectra. The observed result is proposed to be explained using the concepts of percolation theory, taking into account that the formation of a luminophore matrix of a composite wurtzite–sphalerite composition promotes an increase in the diffusion rate of the activator and coactivator ions (Cu⁺ and Br^–) along the interphase boundary and the formation of glow centers. It is shown that radiation exposure, which promotes the formation of structural defects in the initial ZnS matrix, additionally increases the luminescence intensity. The use of this approach allows the creation of materials with the optimal nanostructure and high target characteristics.

Silica aerogel has rec eived more and more attention in the field of thermal insulation. However, the poor mechanical properties and high temperature instability of pure silica aerogels seriously restrict the development and application of silica aerogels. Fiber reinforcement is an effective way to improve the mechanical properties of silica aerogels. In this paper, Al₂O₃–SiO₂ aerogel was compounded with mullite fiber to prepare silicon–aluminum aerogel fiber felt. When the strain value reaches 30%, the compressive strength of the fiber felt with aerogel content of 50.1 wt % reaches 0.21 MPa, and the thermal conductivity of fiber felt decreases from 0.0425 to 0.0322 W/m K when the aerogel content increases to 50.1 wt %. The thermal insulation performance test of fiber felt also showed that the addition of aerogel could significantly improve the heat insulation of fiber felt, and the cold surface temperature of fiber felt was only about 33°C when the flame exceeding 1000°C calcined the fiber felt for 10 s. This work provides a simple solution to prepare aerogel/nanofiber felt with good mechanical properties and low thermal insulation. Highlights: silicon–aluminum composite aerogel felt (AS/ASNFAs) has been prepared by sol-gel and impregnation method, AS/ASNFAs has good mechanical properties (the compressive strength reaches 0.21 MPa) and thermal insulation (0.0322 W/m K), AS/ASNFAs has good flame retardancy, and it remains stable after being burned at 1000 degrees butane for 10 min.

For the first time, the dependence of Poisson’s ratio of the diamond–silicon carbide composite “IDEAL” is studied in a wide range of industrial diamond grain sizes ranging from nanometers to hundreds of micrometers. The deformation mechanism of a body consisting of particles with different coefficients of volumetric thermal expansion is discussed.

Thermal expansion of samarium oxoborogermanate Sm₁₄(GeO₄)₂(BO₃)₆O₈ is studied by the method of high temperature powder X-ray diffraction in the temperature range of 30–1200°C. The coefficients of thermal expansion are calculated: α₁₁ = 9.59(12), α_c = 7.56(13), α_V = 26.74(30) × 10^–6°C^–1 at 30°C; and α_a = 14.44(12), α_c = 10.74(13), α_V = 39.61(28) × 10^–6 °C^–1 at 1200°C. A structural interpretation of the anisotropy of thermal expansion is carried out. With increasing temperature, the degree of anisotropy remains practically unchanged, the structure expands minimally along the c axis, and maximally in the ab plane, perpendicular to the preferred orientation of the BO₃ triangles in the crystal structure. The melting point of Sm₁₄(GeO₄)₂(BO₃)₆O₈ is clarified.

This paper examines the protective properties of two-layer protective panels based on the diamond–silicon carbide ceramic material “Ideal” in comparison with a panel containing corundum tiles. For the first time, the fractional composition of fragments formed after the dynamic testing of panels is assessed and the total surface energy of the resulting small fragments is determined. It is shown that Ideal ceramics are close in terms of properties to ideally brittle material, as a result of which the effective dissipation of kinetic energy and destruction of the indenter are ensured. It is established that during the brittle fracture of Ideal ceramics, the formation of transcrystalline cracks is observed, which proves the high level of strength of interphase bonds in the material.

A series of La₂O₃–Al₂O₃–ZrO₂–TiO₂ glasses co-doped with Er³⁺ and Yb³⁺ ions ([30 – (30/88)(x + y)] La₂O₃–[58 – (58/88)(x + y)]Al₂O₃–4ZrO₂–8TiO₂, x = 2 mol %, and y = 4, 8, 12, 16, 20 mol %, abbreviated as LAZT: xEr³⁺/yYb³⁺) were synthesized using a containerless aerodynamic levitation technique. The amorphous nature, thermal stability, mechanical properties, elemental distribution uniformity, optical transmittance, and refractive index dispersion were characterized. The prepared LAZT: xEr³⁺/yYb³⁺ glasses exhibit homogeneous distribution of all elements, exceptional thermal stability (glass transition temperature T_g > 850°C), superior mechanical properties, high refractive index (~1.9) and Abbe number (>40). The glass-forming ability of the system, initially increasing and then decreasing with increasing the Yb³⁺ concentration, is overall below 100°C, which is relatively poor, and highlights the advantage of containerless technique in preparing the LAZT-based glasses. The above results show that the LAZT: xEr³⁺/yYb³⁺ glasses prepared by the containerless technique are suitable for optical research, practical industrial and up-conversion luminescence applications.

The influence of reinforcing fillers of different structures on the physical and mechanical characteristics of thermoplastic elastomer (TPE) based on butadiene-styrene elastomer is studied with the aim of further application to additive technologies for the production of elastic materials of a complex geometry. The optimal concentrations for graphene and carbon nanotubes (CNTs) are selected to achieve the maximum reinforcement effect. It is noted that by introducing a combined filler into a polymer matrix, it is possible to obtain a synergistic effect and achieve higher physical and mechanical characteristics due to the different structure of the filler. It is shown that the use of 3D printing with nanoreinforced material allows achieving better physical and mechanical characteristics compared to the standard molding methods.