Sintering Of Glass Research Articles

Flash sintering glass–ceramic treatment of Sr-contaminated soil waste

Effective disposal of radioactive waste is crucial for safe development of nuclear energy. In this study, flash sintering technology is used for the first time to quickly solidify simulated Sr-contaminated soil waste. The waste can be converted into a glass–ceramic phase by heating the waste at 1100 °C for 1 min during flash sintering. The phase evolution during flash sintering as a function of density and amorphous fraction was systematically investigated. Additionally, the microstructural evolution of the matrices and the leaching behavior of simulated waste elements (e.g., Sr) were evaluated. This study explores the feasibility of using flash sintering for treating radioactive contamination waste.

Field-assisted sintering of barium titanate and 45S5 bioactive glass for biomedical applications

The development of electrically active biomaterials, which create electrical cues on demand to foster cellular stimulation, remains a challenge. Here, we utilized a Field-assisted sintering approach to densify barium titanate and 45S5 bioactive glass to create a piezoelectric and potentially bioactive composite. By using Field-assisted sintering, we aimed to fabricate dense piezoelectric specimens, preserving a low degree of crystallization of the bioactive glass to keep bioactivity as high as possible. Therefore, we have varied the compositions of the materials and processed them at different sintering temperatures. This enabled us to produce dense test specimens in the 94 %–98 % relative density range. The samples were successfully polarized, and piezoelectric charge constants d33 were determined for the composites. The content of bioactive glass and the sintering temperature influence the charge constant d33. It is in the range of 0.8–3.4 pC/N for the composites, approximately in the order of magnitude assigned to natural tissues such as bone. X-ray diffraction was used to analyze the composition of the processed samples and to investigate the influence of an additional thermal post-treatment. Altogether, we established a process window for field-assisted sintering, allowing the fabrication of a piezoelectric and potentially bioactive biomaterial for tissue engineering.

Mixed alkali effect on the mechanical, thermal and biological properties of 58S bioactive glass

Bioactive glasses (BG) containing silicon, phosphorous, and boron have emerged as promising materials for bone tissue engineering. Modifying ions play a multifaceted role in BGs, influencing their structure, properties, and biological activity that depends on their size, charge, and coordination chemistry. This study investigates the addition of sodium borate (Na2B4O7) to the 58S BG and the mixed alkali effect (MAE) resulting from incorporating Na and B ions into the CaO–SiO2–P2O5 system. In specific concentrations, Na+ and Ca2+ ions function as network modifiers, introducing structural disruptions and generating defects that impact the glass transition temperature (Tg), crystallization temperature (Tc), hardness, and sintering characteristics. The physicochemical characterization of BGs confirms the incorporation of Na and B structures. Furthermore, the Na and B doped glass sample with a [Na/Si] ratio of 0.045 exhibits favorable properties for promoting cell attachment, including forming a hydroxyapatite (HAp) layer over the surface, thereby accelerating human placental mesenchymal stem cells (hPMSCs) proliferation. The findings demonstrate the potential of Na2B4O7 incorporation in BG for bone tissue engineering applications.

BATCH COMPOSITION INFLUENCE ON SINTERING AND CRYSTALLIZATION PROCESSES OF CORDIERITE GLASSES OBTAINED BY THERMAL PLASMA MELTING

This article focuses on the production of glasses and glass-ceramic materials with a cordierite (2MgO∙2Al2O3∙5SiO2) composition. The processes of crystallization and sintering of cordierite glasses, which are based on natural raw materials, pure oxides and pre-synthesized cordierite, have been investigated. It has been determined that cordierite glasses produced via plasma melting exhibit high structural defects attributed to rapid heating and cooling rates. The relaxation of microstresses in the glasses takes place within the temperature range of 480 – 490 °C. Glasses based on synthesized cordierite exhibit a crystallization temperature of 930 – 1020 °C, depending on the presence and type of nucleating agents. This is approximately 20 – 50 °C lower compared to glasses based on component mixtures. The primary crystallization product of studied glasses at 900 °C is the high-quartz solid solution with formula MgO∙Al2O3∙3SiO2, which is dissociate above 1000 °C with the formation of cordierite. The addition of 5% ZrO2 to the batch increases the viscosity of softened glasses and their crystallization temperature, resulting in increased activity of glass powders in the sintering processes due to the higher impact of liquid-phase sintering on the general densification process of glass-ceramics. This allows for the production of glass-ceramics with open porosity of 2 – 4% at 1300 – 1350 °C. The addition of 5% TiO2 to the batch reduces the glass crystallization temperature. However it does not significantly effect on the cordierite glass-ceramics sintering processes. For citation: Sharafeev S.M., Shekhovtsov V.V., Zvyagina E.E. Batch composition influence on sintering and crystallization processes of cordierite glasses obtained by thermal plasma melting. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 80-87. DOI: 10.6060/ivkkt.20246707.7032.

Novel cesium immobilization by alkali activation and cold consolidation of waste pharmaceutical glass

A new method of cesium immobilization has been successfully developed by combining alkali activation of boro-alumino-silicate glass and viscous flow sintering. Powdered glass from discarded pharmaceutical vials, suspended in a 2.5 M CsOH aqueous solution, underwent surface hydration as well as partial dissolution. Condensation reactions occurring at hydrated surface layers upon drying at 40 °C over 7 days resulted in welding of adjacent particles, forming a network that trapped newly formed gel and crystal phases. The newly formed phases including crystalline boro-pollucite (CsBSi2O6), were derived mostly from Cs+ ions reacting with the products of glass dissolution and exhibited a high chemical stability. Further stabilization was achieved through viscous flow sintering at 700 °C, resulting in the incorporation of Cs+ ions in a glass matrix. The effectiveness of the immobilization was confirmed by leaching test using the Materials Characterization Center-1 Standard (MCC-1). This innovative approach not only enhances the chemical stability of cesium waste forms, but also aligns with principles of cleaner production by repurposing pharmaceutical glass waste, promoting sustainable materials management.

Glass Sintering Aid Effect on Magnetic and Dielectric Properties of YFeO3 Ceramics

YFeO3 (YFO) and optimized glass wt% [0.5Li2O-0.5K2O-2B2O3 (LKBO) and BaO-Bi2O3-B2O3 (BBBO)] as a sintering aid in YFO ceramics were fabricated using fine powders prepared from sol-gel technique. Pure YFO and glass sintering aid added into YFO ceramics show orthorhombic crystal structure, confirmed by Rietveld refinement with the help of X-ray powder diffraction data. Scanning electron microscopy study revealed that the glass sintering aid added into YFO ceramics shows a higher average grain size than that of YFO ceramic. X-ray photoelectron spectroscopy was employed to confirm the presence of each atom/ion/element and their oxidation number in their respective samples. Using the Archimedes method, the density of the each ceramic sample was estimated. The BBBO glass sintering aid added into YFO exhibited a higher maximum magnetization value (2.82 emu g−1) compared to that of LKBO added into YFO (2.51 emu g−1) as well as pure YFO (1.53 emu g−1) ceramics. BBBO glass sintering aid added into YFO ceramic shows a higher dielectric constant, lower dielectric loss, and lower conductivity compared to LKBO added into YFO as well as pure YFO ceramics. In conclusion, improved magnetic and dielectric response of BBBO glasses added into YFO ceramic is a potential candidate for different dielectric-magnetic based applications.

Customized linear refractive index GRIN prepared by rapid sintering of multilayer chalcogenide glass powders

AbstractGradient refractive index (GRIN) lenses have recently become a hot topic in compact imaging and achromaticity. Current research focuses on exploiting GRIN materials and upgrading the preparation technology. In this study, infrared (IR) GRIN materials were successfully prepared by spark plasma sintering of multilayer chalcogenide glass (ChGs) powders. ChGs powders were derived from the Ge20Se80‐xTex series glasses (x = 0–28 mol%) with a maximum refractive index difference (Δn) of 0.25. The similar glass transition temperatures (ΔTg < 10°C) promote efficient sintering of multilayer powders. Six‐, eight‐, and ten‐layer powders of different compositions were rapidly sintered with a thickness of 600, 300, and 200 µm per layer, respectively. Such tiny layer thickness enables the GRIN materials to exhibit nearly linear refractive index variation. Energy dispersive spectroscopy line scans well characterized the gradient variation of GRIN. The maximum deviation of the refractive index gradient from the fitted target line was only ± 0.016 for the 10‐layer GRIN. The sintered GRIN shows excellent IR transparency, which is of great interest for mid‐wave and long‐wave infrared imaging.

Sintering and crystallization kinetics of bioactive glass 13–93

This study investigates the sintering and crystallization behavior and kinetic of the bioactive glass (BG) 13–93 with nominal composition (in mol%): 54.6 SiO2 - 1.7 P2O3 - 22.1 CaO - 6.0 Na2O - 7.9 K2O - 7.7 MgO. Sintering and crystallization were investigated non-isothermally for various particle size fractions smaller than 315 µm as well as for bulk samples. Densification was not hindered by the presence of crystalline phases across all particle size fractions. Afterwards, wollastonite was found as the dominant crystal phase at higher temperature which resorb primary surface precipitation-like quartz crystallites. The growth direction shifts into volume when the sample surface is nearly covered. The crystal growth rate of wollastonite was calculated from the crystalline surface layer thickness measured during heating. The findings of this study are relevant for the high temperature processing of BG 13–93.

Minimally processed recycled yttria-stabilized tetragonal zirconia for dental applications: Effect of sintering temperature on glass infiltration

This study aimed to develop a recycling process for the remnants of milled 3Y-TZP and enhance their properties using glass infiltration. 3Y-TZP powder was gathered from the vacuum system of CAD–CAM milling equipment, calcined and sieved (x < 75 μm). One hundred twenty discs were fabricated and pre-sintered at 1000 °C/h. These specimens were then divided into four groups, categorized by glass infiltration (non-infiltrated [Zr] or glass-infiltrated [Zr-G]) and sintering temperature (1450 °C [Zr-1450] or 1550 °C [Zr-1550]/2h). After sintering, the specimens were characterized by X-Ray Diffraction (XRD), relative density measurement, and scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). The biaxial flexural strength test was performed according to the ISO 6872 and followed by fractographic analysis. Subsequent results were analyzed using Weibull statistics. Relative density values of the sintered specimens from Zr-1450 and Zr-1550 groups were 86.7 ± 1.5% and 92.2 ± 1.7%, respectively. Particle size distribution revealed particles within the range of 0.1–100 μm. XRD analysis highlighted the presence of the ZrO2-tetragonal in both the Zr-1450 and Zr-1550 groups. Glass infiltration, however, led to the formation of the ZrO2-monoclinic of 9.84% (Zr-1450-G) and 18.34% (Zr-1550-G). SEM micrographs demonstrated similar microstructural characteristics for Zr-1450 and Zr-1550, whereas the glass-infiltrated groups exhibited comparable infiltration patterns. The highest characteristic strength was observed in the glass-infiltrated groups. Fractographic analyses suggested that fracture origins were related to defects on the tensile side, which propagated to the compression side of the samples. Both the sintering temperature and glass infiltration significantly influenced the mechanical properties of the 3Y-TZP recycled.

Bioactivity and characterization of Wollastonite-Li-silicate glass

Glasses were prepared from nominal wollastonite-lithium silicate in the ratios of 87.5/12.5, 75/25, 50/50, 25/75, and glasses respectively. However, the glass of 25/75 ratio run through devitrification into lithium silicate and little quartz whereas, the other three ratios formed transparent glasses. The thermal behavior of glasses shows a decrease in the main exothermic temperature; which goes along with an increase in the lithium silicate content. Sintering of such glasses at the crystallization temperature given by differential thermal analysis (at 607 °C + 705 °C and at 661 °C) or at one step at 1000 °C, indicates the formation of three phases of pseudowollastonite [Ca3(Si3O9)], wollastonite (CaSiO3), and lithium silicate (Li2SiO3). The results of the in-vitro test by means of soaking in SBF for two weeks tracked by scanning the sample's surface and measuring the calcium and phosphorous ions using induced coupled plasma (ICP) in the SBF, exhibited that samples had improved talent to accelerate the mineralization of calcium phosphate and that the ratio of Ca/P declined from 2.55 to 1.86 upon increment of the Li2O ratio. The X-ray analysis shows the formation of hydroxyapatite on the sample’s surfaces. The biocompatibility and thermal properties of the premeditated glass ceramics secure exceptional properties and can be used to impress different biomedical applications.

Low cost structured photocatalysts from stereolithography of colorless pharmaceutical glass

The present study is dedicated to the manufacturing of highly porous triply periodic minimal surface (TPMS) constructs, fabricated from recycled end of life borosilicate pharmaceutical glass employing masked stereolithography. The structures were prepared from a simple blend of photocurable resin with glass powder (<38 µm). The gyroid model was selected with the porosity varying from 75 to 90%. Hot stage microscopy was applied to examine the glass sintering behaviour to improve the translucency of the 3D scaffolds. The obtained 3D scaffolds were dip-coated with TiO2 and further utilized for the photocatalytic degradation of dyes. The photocatalytic efficiency of the 3D scaffolds was evaluated by the degradation of methylene blue in water. It was found that 3D scaffolds coated with TiO2 showed a 40% higher degradation rate in comparison to bare 3D scaffolds under UV irradiation, which determines the significant role of TiO2 in the organic dye degradation. The better efficiency of 3D scaffolds coated with TiO2, compared with uncoated BSG 3D scaffolds is attributed to a better recombination rate, and the migration of electrons to the surface of the scaffold, where the charges participate in the photodecomposition of MB dye. The efficiency of the scaffolds was assessed for five consecutive cycles. The degradation efficiency after the fifth cycle was 75%, confirming the stability of the system.

Upcycling glass wool and spodumene tailings in building ceramics from kaolinitic and illitic clay

With concerns related to the high cost and environmental footprint of energy, reducing the sintering temperature in the ceramic industry remains a key challenge. This study investigates the effect of glass wool waste on the sintering properties of kaolinitic and illitic clays, two types of clay commonly used in the ceramic industry. Both clays were substituted with 20 and 40 wt% glass wool, and the effect on sintering at 850, 950, and 1050 °C was investigated. The properties of the sintered materials were assessed with several techniques, including X-ray diffraction, scanning electron microscopy, bulk density, water absorption, dilatometry, and compressive and flexural strength. The water absorption of the prepared ceramics varied from 0 to 30 %, while compressive and flexural strength were in the ranges of 10–60 MPa and 2–15 MPa, respectively, depending on the glass wool content and sintering temperature. The addition of glass wool induced more glass formation, microstructure densification, and higher firing shrinkage at lower temperatures, which contributed to an increase of more than 100 % strength at 850 °C. The addition of 10–20 parts spodumene tailings was observed to mitigate the firing shrinkage at 950 °C with no significant effect on the mechanical properties.

Immobilization of simulated An3+ in radioactive sludge via microwave sintering: Mechanism and performance

This study investigates the safe disposal of simulated radioactive sludge. Microwave sintering of silicate glass (SG) particles and simulated sludge is performed to prepare amorphous glass materials and oxy-apatite (AⅠxAⅡ10-x(SiO4)6O2) glass ceramics. The phase-evolution, microstructure, nucleation-growth mechanism, and chemical stability of the solidified products are systematically investigated. The optimum vitrification degree of the solidified product containing 60 wt.% SG particles in the radioactive sludge is achieved at 1200 ℃. Elements are uniformly distributed, and the final solid-solubility of Nd in the glass structure is 32 wt.%. For higher content, the Nd remained fixed at the AⅠ and AⅡ positions of an oxyapatite crystalline structure. The glass-ceramic material exhibited a high solid-solubility of Nd up to 40 wt.%. Furthermore, the normalized leaching rate of Nd was observed at a low level of 10−6 g·m−2·d−1 after 42 d. This study suggests a new processing method for the safe disposal of radioactive sludge.

Crystallization mechanism of B12.5 bioactive borosilicate glasses and its impact on in vitro degradation

Understanding the thermal properties and crystallization mechanisms are crucial upon sintering of bioactive glasses. In this study, crystallization mechanism and sintering ability of S53P4-based B12.5 borosilicate glass series, containing varying amounts of magnesium and/or strontium, was assessed. Additionally, the effect of crystallization onto these glasses bioactive properties was investigated.Glasses were composed of 47.12 SiO2 - 6.73 B2O3 - 21.77-x-y CaO - 22.65 Na2O - 1.72 P2O5 - x MgO - y SrO, where x,y = 0, 5 or 10 (mol%). Thermal properties were analysed with DTA, and glass transition temperatures and onset of crystallization were determined to gain an overview of temperature range suitable for heat treatments, and for calculation of activation energies related to viscous flow and crystallization. Further, sintered bodies were formed by heat-treating coarse glass particles in large temperature range; their porosity was assessed, cross section were analysed by SEM and crystallinity was studied with XRD. To evaluate the impact of crystallization on the in vitro reactivity, dissolution studies were executed in SBF-solution up to one week, with pH and ion content of solution measured at the end of immersion. Immersed particles were studied with FTIR to observe changes in the glasses structure.The main crystallization mechanism of B12.5-based glasses was determined to be surface crystallization. While the crystallization interfered with viscous flow sintering of the pure borosilicate glass, Mg and Sr addition enabled sintering of amorphous bodies more easily and with wider temperature range. Mg in the composition especially enabled densification. In vitro studies presented that surprisingly, partially crystallized specimen were initially more reactive than the amorphous specimen.

Glass Microspheres Thermo-Deformation Sintering Processes in the Technologies of Obtaining Materials for Underwater Technical Equipment

Abstract In this work, the important scientific and technical problem of creating multifunctional composite materials for shipbuilding and ocean engineering was solved. The work aimed to study the thermal deformation processes of sintering glass microspheres to obtain lightweight glass composites with a cellular structure that provides positive buoyancy and sound insulation properties. For this purpose, glass microspheres of Na2O‒SiO2 and Na2O‒B2O3‒SiO2 composition with a dispersion of 10 to 60 μm were used as raw materials. They were sintered to form a closed, porous structure. The theoretical substantiation of technological parameters is based on the concepts of solid state and glassy state chemistry and physicochemical concepts of glass softening processes. The process of hot-pressing glass microspheres without plasticisers and additives was investigated. The author’s own laboratory equipment was used for the experiments. The sintering intensity was determined from the results of shrinkage processes; the kinetic shrinkage curves were constructed in semilogarithmic coordinates. The glass composite samples were examined by optical and electron microscopy. As a criterion, the storage of spherical microspheres under the influence of simultaneous heating to 700 °C with the application of pressure in the range of 0,5 to 1,5 MPa was chosen. It was established that the formation of a predominantly closed-porous structure of glass composites with a density of 350...600 kg/m3 occurs by the mechanisms of viscous glass phase flow through liquefaction processes in the walls of microspheres. At the same time, shrinkage processes in the linear direction reach up to 50%. The acoustic properties were investigated by measuring the differences in sound pressure levels in octave frequency bands using a Kundt pipe. The water absorption of the glass composite samples was determined at hydrostatic pressures up to 20 MPa. The research results were compared with the characteristics of analogue composites, such as syntactic foams and foam glass. The developed materials can be used in the design and manufacture of technical equipment for research and maintenance of underwater infrastructure. The prospects for further research are related to the feasibility study and marketing research on implementing the developed glass composites.

Study on Low-Temperature Conductive Silver Pastes Containing Bi-Based Glass for MgTiO3 Electronic Power Devices.

Low-temperature lead-free silver pastes deserve thorough investigation for sustainable development and application of MgTiO3 ceramics in electronic devices. In this study, a series of Bi2O3-B2O3-ZnO-SiO2-Al2O3-CaO glasses with suitable softening temperatures were prepared via melt quenching using a type of micrometer silver powder formed by silver nanoparticle aggregates. The composite pastes containing silver powder, Bi2O3 glass powder and an organic vehicle were then screen-printed. The effects of glass powder concentration and sintering temperature on the microstructure of the surface interface were also investigated. The results showed that the silver paste for microwave dielectric ceramic filters (MgTiO3) possessed good electrical conductivity (2.28 mΩ/□) and high adhesion (43.46 N/mm2) after medium temperature (670 °C) sintering. Thus, this glass powder has great application potential in non-toxic lead-free silver pastes for metallization of MgTiO3 substrates.

Novel experimental strategy towards temperature inhomogeneity during spark plasma sintering of metallic glasses

Novel experimental strategy towards temperature inhomogeneity during spark plasma sintering of metallic glasses

Effect of Thermal Treatments and Ion Substitution on Sintering and Crystallization of Bioactive Glasses: A Review.

Bioactive glasses (BGs) are promising materials for bone regeneration due to their ability to bond with living bone tissue. However, thermal stability and mechanical properties of BGs need improvement for better clinical performance. In this paper, we present an overview of the influence of different ions on the sintering and crystallization of BGs. Specifically, this review focuses on the impact of thermal treatments on the crystallization of 45S5 and other significant BG compositions. Potential applications of these thermally treated BGs, such as scaffolds, BG-based composites, and thermally sprayed coatings, are explored. Moreover, the substitution of ions has been investigated as a method to enhance the thermal properties of BGs. Notably, zinc, potassium, and strontium have been studied extensively and have demonstrated promising effects on both the thermal and the mechanical properties of BGs. However, it is important to note that research on ion inclusion in BGs is still in its early stages, and further investigation is necessary to fully comprehend the effects of different ions on sintering and crystallization. Therefore, future studies should focus on optimizing the ion substitution method to improve the thermal, mechanical, and even biological properties of BGs, thereby enhancing their potential for various biomedical applications.

High luminous efficiency of a phosphor-in-glass plate by optimization of the glass and phosphor content for high-power LED applications

Generally, white light-emitting diodes (LEDs) are fabricated by combining blue LED chips with yellow phosphors. When fabricating white LEDs, the phosphor is typically mixed with an organic resin and applied to the LED chips as a paste. A phosphor-in-glass (PiG) plate can alternatively be used to address the poor high-temperature reliability of the paste method. However, because pores form in the PiG plate during the sintering process, this method results in a loss of optical efficiency. Accordingly, we aimed to improve the fluidity of glass and light efficiency by optimizing the sintering temperature of the glass powder and the phosphor content respectively for reducing internal porosity in the PiG. In this study, glass powder was sintered at different temperatures to produce glass plates, while also varying the phosphor content to fabricate PiG plates. The optimal light characteristics were realized with a glass sintering temperature of 640 °C and a phosphor content of 20 wt%.

Preparation and Characteristics of the Fired Bricks Produced from Polyaluminum Chloride Slag and Glass Powder

Polyaluminum chloride slag produced in the production of water treatment agents pollutes the environment and wastes land resources in the process of landfill and waste. In order to solve the resource waste of researching polyaluminum chloride slag, it was used to prepare sintered bricks. In this study, sintered bricks were prepared from polyaluminum chloride slag and glass powder. Taking compressive strength, water absorption, linear shrinkage and bulk density as measurement indexes, the effects of the glass powder content (0–10 wt%), molding moisture (10–20%), molding pressure (15–27.5 MPa), heating method (heat preservation at 400 °C and 1000 °C for 2 h, heat preservation at 500 °C and 1000 °C for 2 h, and heat preservation at 1000 °C for 2 h), heating rate (2–10 °C/min) and sintering temperature (900–1100 °C) on the performance of sintered brick and the conditions for meeting Chinese standards were studied. Then, the sintered bricks prepared at different temperatures were characterized by X-ray diffraction and scanning electron microscopy. The results show that the compressive strength (bulk density) increases and the water absorption decreases with the increase of the glass powder content, molding pressure, molding moisture and sintering temperature. Moreover, the linear shrinkage increases with the increase of the molding pressure, molding moisture and sintering temperature, but decreases with the increase of the glass powder content. When the glass powder content of the sintered brick is 10 wt%, with molding moisture of 20 wt%, molding pressure of 25 MPa, heating mode to directly raise the temperature to the target temperature, heating speed of 10 °C/min and sintering temperature of 1100 °C, the properties, pH value and leaching toxicity of sintered bricks meet the requirements of Chinese standard brick MU15. XRD and SEM analyses showed that with the increase of the sintering temperature, new albite and amphibole phases were formed in the structure, and quartz and other silicate minerals melted to form a liquid phase, making the structure more compact and the performance better. The research results provide a reference for the comprehensive utilization of polyaluminum chloride slag.