The technology of synthesis of porous microgranular material based on diatomaceous clay is considered. The process of foaming microgranules in an industrial furnace was implemented in the way of obtaining granular foam-glass ceramic of coarse fractions. The main properties of microgranular foam-glass ceramic samples were investigated depending on the NaOH content in the charge, as a result of which its composition was optimized to obtain particles with a size of 75 ?m and a minimum content of particles sinking in water. The peculiarity of the porous structure of microgranular foam-glass ceramic makes it possible to obtain more durable lightweight grouting slurries in comparison with the traditional additive. The research results expand the range of materials made of foam-glass ceramic and the raw material base due to the more accessible for development deposits of diatomaceous clays in the arctic regions.
During the synthesis of different calcium phosphate phases, the pH variation of the slurry solution affects the purity, structure, and chemical composition of final products. High-capacity buffering agent solutions were used to keep the pH value constant during the synthesis procedure. Consequently, high purity and single-phase HA, b-TCP. Also, morphological evaluation of granules from plate-like to completely porous structure is another result of keeping the slurry pH constant during the synthesis step. Increasing the specific surface area of BCP granules from 10 to 38 m2/g affected the in vitro behaviour of the products. Precipitation of 20 nm hydroxyapatite phase after suspension of experimental samples for 30 days in simulation body fluid attributed to using Tris buffer solution during synthesis.
The paper presents the results of a study on the cyclic strength of cutting ceramics: a replaceable polyhedral plate developed at NSTU and VOK-60 cutting ceramics when processing a hardened steel billet made of HVG steel (45 HRC) with two opposite grooves. Turning was performed until the cutting edge of the plates was destroyed. Using the HITACHI S3400N electron microscope, the structure of the destroyed surface layer was investigated and the mechanism of destruction of the cutting edge of tool plates made of cutting ceramics was determined. It has been established that the developed cutting ceramics have a greater resistance to fracture under conditions of intermittent turning of hardened steel compared to the VOK-60 brand. The low operability of the cutting plates made of the developed ceramics under conditions of intermittent turning is mainly caused by the chipping of the cutting edge due to the formation of microcracks at the grain boundaries. A characteristic feature of the mechanism of brittle fracture of cutting ceramics is intergrain tearing and chipping of large Al2O3 grains.
The combined effect of the microwave field and the content of reinforcing medium-dispersed silicon carbide particles on the density of a ceramic material based on montmorillonite containing clay of the Orenburg region is investigated. It is shown that with the content of carbide particles in the range of 20 – 30 wt. % after microwave drying of the samples, the maximum values of the density of the “ceramic mass-silicon carbide” system are reached. The increase in the density of all ceramic mass compositions is due to an increase in sintering coefficients and the appearance of a strong stable sillimanite phase in the phase compositions.
Substrates for the surface enhance Raman spectroscopy (SERS) are being actively developed with the aim of precise detecting of the low concentrations of organic molecules. However, the complexity and cost of substrates manufacturing often limits their applications. In this work, we proposed a simple method for preparing SERS substrates based on the nanoporous glass functionalized with silver particles and demonstrated their efficiency in the detecting of low concentrations of benzoic acid.
Hydrated zirconia was obtained by solid state synthesis and precipitation. Physicochemical properties and phase composition of calcined hydrated zirconia was investigated by XRD, IR and DSC-TG. Hydrated zirconia obtained by solid state synthesis has lower moisture content and higher filterability to compare with precipitated one. Zirconia precursor synthesis with ammonium carbonate considerable decrease specific surface area to compare with precursor precipitated by ammonium hydroxide or ammonia. Tetragonal and monoclinic zirconia was obtained by hydrated zirconia calcination under 450 °C. Calcination temperature increase up to 600 °C lead to drastically decrease of tetragonal zirconia content. The roast obtained under 1150 °C contain only monoclinic zirconia.
In the framework of the one-dimensional problem of evaporation of the absorbing layer of the material with the “instantaneous” release of laser pulse energy, the possibility of reducing energy costs when scribing glass and ceramic plates is investigated. A method of scribing is proposed, in which the laser radiation released through the back surface of the plate is returned to the plate using a mirror with a reflection coefficient of ~ 99 %. Optimal modes of plate scribing have been determined. It is shown that with deep scribing, it is possible to reduce energy costs by 1.4 – 1.8 times compared to traditional laser scribing. When the depth of the scribing groove is less than 0.3 of the plate thickness, the use of the considered method is impractical due to the insignificance of the positive effect.
The article presents the results of a physicochemical study of the process of high-temperature sintering and solid-phase reactions in a ternary composition based on Koitash quartzite, Angren clay and Karakhtaisky limestone for obtaining unshaped dinas refractory materials. It was found that as a result of these processes, chemical interaction occurs both with the help of solid-phase reactions and with the participation of a liquid phase with the formation of highly basic aluminosilicate minerals with high refractoriness, strength and low porosity, which are reflected in the production of unshaped refractory materials with improved physical and mechanical technological properties.
A new luminescent hybrid material based on silica aerogel and a boron-containing coordination compound with 8-hydroxyquinoline has been created, and its physico-chemical and spectral-luminescent characteristics have been studied. A scheme for the synthesis of a hybrid luminescent material has been developed/ The scheme eliminates the need for preliminary expensive synthesis of a high-purity organoelemental boron-containing phosphor. It has been established that aerogel hydrophobization significantly increases the stability of the luminescent characteristics of the hybrid material.
Zircon-containing whitening agents are indispensable components increasing the cost of ceramic tiles. In the ceramic industry, the developing of unique and low-cost whitening agents with comparable final product quality is an essential motivation. In this study, a unique ZrO2–Al2O3–K2O-based whitening agent was developed by mixing zircon silicate, Al2O3, K-feldspar, and marble with various weight concentrations to reduce costs and give a valid alternative to the commercially available R6-coded ZrO2–Al2O3–Na2O whitening agent. To test the innovative ZrO2–Al2O3–K2O-based whitening agent’s efficiency, a systematic characterization procedure was utilized to reveal factors affecting the tile opacity, including size, shape, and distribution of opacifier particles and the incident light wavelength. First, X-ray diffraction and X-ray fluorescence analyses examined the initial grain sizes and structural properties of the whitening agent constituents. Second, a wet milling process in industrial mills was utilized to produce a homogenized ZrO2–Al2O3–K2O-based composite whitening agent. Structural, mineralogical, and morphological properties of the final product were determined after the drying process. The efficiency of the wet milling process was proved according to scanning microscopy analysis revealing homogenous particle size distribution of constituents with mainly composed of ZrO2, Al2O3, and SiO2 phases. Energy dispersive X-ray analysis reveals that Si–Al–O–Zr and Ca were major elements whereas Na was obtained as minor element. The full article will be published in the translated version of the journal Glass and Ceramics, 2022, V. 79, No. 5–6.
