Search Results (411)

The surface of ceramic products manufactured using diamond grinding is replete with shallow scratches, deep grooves and other defects. The thickness of the defective layer amounts to 3–4 µm and it must be removed to increase wear resistance of the products when exposed to intense thermomechanical loads. In this study, removal of the defective layers from samples made of ZrO₂, Al₂O₃ and Si₃N₄ with a beam of fast argon atoms was carried out with a stripping rate of up to 5 µm/h. To prevent contamination of the source of fast argon atoms by the sputtered dielectric material, the beam was compressed and passed to the sample through a small hole in a wide screen. Due to the removal of the defective layer, abrasive wear decreased by an order of magnitude and the adhesion of coatings deposited on the cleaned ceramic surfaces improved significantly. Full article

The paper presents the results of studies of the resistance of lithium ceramics to helium swelling during its accumulation in the structure of the near-surface layer, and the identification of the three types of lithium ceramics most resistant to radiation degradation: Li₄SiO₄, Li₂TiO₃, and Li₂ZrO₃. The simulation of helium swelling under high-dose irradiation was carried out by irradiation with He²⁺ ions with fluences of 1 × 10¹⁶ ion/cm²–5 × 10¹⁷ ion/cm², which allows for simulating the implanted helium accumulation with a high concentration in the damaged surface layer (about 500 nm thick). The samples were irradiated at a temperature of 1000 K, the choice of which was determined by the possibility of simulating radiation damage as close as possible to real operating conditions. Such accumulation can result in the formation of gas-filled bubbles. Through the application of X-ray phase analysis, indentation testing, and thermophysical parameter assessments, it was ascertained that among the three ceramic types, Li₄SiO₄ ceramics exhibit the highest resistance to helium-induced swelling. These ceramics experienced less significant alterations in their properties compared to the other two types. An analysis of the correlation between the structural and strength parameters of lithium-containing ceramics revealed that the most significant changes occur when the volumetric swelling of the crystal lattice becomes the dominant factor in structural alterations. This phenomenon is manifested as an accelerated degradation of strength characteristics, exceeding 10%. At the same time, analysis of these alterations in the stability of thermophysical parameters to the accumulation of structural distortions revealed that, regardless of the type of ceramics, the degradation of thermophysical properties is most pronounced under high-dose irradiation (above 10¹⁷ ion/cm²). Full article

The pursuit of low-power/low-voltage operation in devices has prompted a keen interest in the mesoscale effects within ferroelectric thin films. The downsizing of ferroelectrics can significantly influence performance; for instance, the remanent polarization and coercive field are susceptible to alterations based on thickness. In this study, randomly oriented Bi_3.25La_0.75Ti₃O₁₂ thin films were fabricated on Pt/Ti/SiO₂/Si substrates using the sol–gel method, and SEM observations revealed rod-like grains in all thin films. The investigation delved into the correlation between dielectric and ferroelectric properties with thin film thickness. The thin film exhibited an increased remanent polarization and a reduced coercive electric field. Additionally, the ferroelectric domain structure was scrutinized through PFM, and the resistor properties of the BLT4 thin film were studied, which shows the potential of BLT thin films in non-volatile memory and memristor. Full article

This study compares HfO₂ ceramics synthesized using sol–gel and combustion methods, emphasizing the impact of the method of synthesis on the resulting properties of the material. The research findings illustrate morphological differences between sol–gel and combustion-derived HfO₂. While sol–gel samples displayed irregular nanoparticles with pronounced boundaries, combustion samples revealed more homogeneous structures with particles tending towards coalescence. It was discerned that Eu³⁺ doping induced oxygen vacancies, stabilizing the tetragonal phase, while subsequent doping with Nb⁵⁺ significantly reduced these vacancies, which was also observed in photoluminescence analysis. Furthermore, combustion synthesis left fewer organic residues, with urea presence during synthesis contributing to residual organic components in the material. XPS analysis was used to evaluate the presence of oxygen-deficient hafnia sub-oxide in the samples. The study underscores the important role of tailored synthesis methods in optimizing the properties and applications of HfO₂. Full article

Transparent glass-ceramics with a Li₂O–Al₂O₃–SiO₂ (LAS) system have been extensively utilized in optical systems in which thermal stability is of utmost importance. This study is aimed to develop thermal treatment routes that can effectively control the structure of transparent LAS glass-ceramics and tune its thermal expansion coefficient within a wide range for novel applications in photonics and integrated optics. The optimal conditions for the nucleation and crystallization of LAS glass were determined by means of differential scanning calorimetry and a polythermal analysis. XRD, Raman spectroscopy, and TEM microscopy were employed to examine the structural changes which occurred after heat treatments. It was found that the second stage of heat treatment promotes the formation of β-eucryptite-like solid solution nanocrystals, which enables effective control of the coefficient of thermal expansion of glass-ceramics in a wide temperature range of −120 to 500 °C. This work provides novel insights into structural rearrangement scenarios occurring in LAS glass, which are crucial for accurately predicting its crystallization behavior and ultimately achieving transparent glass-ceramics with desirable properties. Full article

The study examines the influence of variations in the compositions of components for the production of lithium-containing ceramics based on lithium metazirconate obtained by the method of mechanochemical grinding and subsequent thermal sintering. For component variation, two compositions were used, consisting of zirconium dioxide (ZrO₂) and two distinct types of lithium-containing materials: lithium perchlorate (LiClO₄·3H₂O) and lithium carbonate (Li₂CO₃). Adjusting the concentration of these components allowed for the production of two-phase ceramics with varying levels of impurity phases. Using X-ray phase analysis methods, it was determined that the use of LiClO₄·3H₂O results in the formation of a monoclinic phase, Li₂ZrO₃, with impurity inclusions in the orthorhombic phase, LiO₂. On the other hand, when Li₂CO₃ is used, the resulting ceramics comprise a mixture of two phases, Li₂ZrO₃ and Li₆Zr₂O₇. During the studies, it was established that the formation of impurity inclusions in the composition of ceramics leads to an increase in the stability of strength properties with varying mechanical test conditions, as well as stabilization of thermophysical parameters and a decrease in thermal expansion during long-term high-temperature tests. It has been established that in the case of two-phase ceramics Li₂ZrO₃/Li₆Zr₂O₇ in which the dominance of the Li₆Zr₂O₇ phase is observed during high-temperature mechanical tests, a more pronounced decrease in resistance to cracking is observed, due to thermal expansion of the crystal lattice. Full article

We investigated the effects of Co doping on Pr_0.7Ca_0.3MnO_3−d in the perspective of an oxygen-bonding state change. In all compositions, Pr_0.7Ca_0.3Mn_1−xCo_xO_3−d (PCMCx, x = 0, 0.1, 0.2, 0.3) showed an orthorhombic structure, and the lattice gradually contracted with increasing Co content. The doped Co was mostly present as 2+ and 3+, which decreased the average oxidation value of the B site and created oxygen vacancies for charge compensation. However, as the Co content increased, the proportion of Co³⁺ increased, and the content of oxygen vacancies gradually decreased. In addition, the ratio of adsorbed oxygen in PCMC0.1 was the highest, and the B-O covalency was enhanced. Accordingly, the electrochemical reaction of oxygen with the cathode material in PCMC0.1 could occur most easily, showing the smallest polarization resistance among the Co-doped Pr_0.7Ca_0.3MnO_3−d. We can confirm the formation of oxygen vacancies via Co doping and the effect of B-O covalency on the oxygen-reduction reaction of Pr_0.7Ca_0.3MnO_3−d. Full article

This study explores the potential benefits of incorporating Recycled Demolition Waste (RDF) as an additive in ceramic mass for the brick industry, with a focus on applications such as thermoblocks. The research underscores the significance of sustainable waste management practices and environmental conservation by diverting waste from landfills. RDF, exhibiting combustion properties above 550 °C, emerges as a valuable candidate for enhancing clay-based materials, particularly in the brick production process where firing temperatures exceed 850 °C. Conducted in two phases, the research initially concentrated on RDF preparation, RDF integration with clay materials, and its influence on extrusion and drying phases. Employing innovative techniques involving brick and tile industry machinery coupled with sand incorporation yielded promising results. The grounding of RDF particles to less than 1 mm not only facilitated the mixing process but also ensured stable grinding temperatures within the hammer mill, reducing operational costs. During extrusion, challenges associated with unprocessed RDF material were addressed by utilizing ground RDF, leading to a more efficient and cost-effective process with enhanced plasticity and reduced water requirements. Practical implications for brick plant operations were identified, promoting resource and energy savings. Drying behavior analysis revealed the positive impact of RDF integration, showcasing reduced sensitivity, decreased drying linear shrinkage, and improved density properties. RDF’s role as an inert additive resulted in a 5% reduction in density, enhancing porosity and thermal insulation properties, particularly in thermoblock applications. In the brick industry, where durability, thermal performance, and cost-efficiency are paramount, this study emphasizes the potential benefits of incorporating RDF into clay-based materials. While further research is needed to address the firing procedure of RDF as a brick mass additive, the initial findings underscore the promise of this approach for sustainable and environmentally responsible brick production. This study contributes to the literature by shedding light on the advantages and challenges of integrating RDF into clay-based products, supporting sustainability and waste reduction in construction and manufacturing. The findings provide valuable insights into the performance and feasibility of these mixtures, offering crucial information for industries striving to adopt eco-conscious production methods. This article not only outlines the applied methodology and experimental setup but also presents results related to the behavior of RDF-inclusive clay block mixtures in the production environment. Anticipated to exert considerable influence on future practices and policies, this research contributes to the growing body of knowledge concerning eco-friendly and sustainable manufacturing processes. Full article

Fly ash (FA)-based geopolymer was prepared using sodium hydroxide and sodium silicate (in 2.5ratio) as an alkali activator liquid (AL). The condition of FA/AL was optimized for achieving 1.00, 1.25, 1.5, and 1.75 ratios by varying the alkali concentrations, which are referred to as GP1, GP2, GP3, and GP4, respectively. The influence of slight variations in the FA/AL ratio on microstructure, morphology, functional groups, and composition was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). FESEM detected a homogeneous fused matrix of fly ash and alkali activator solution up to 1.5 ratios; GP3 showed a dense morphology. FTIR confirmed that the formation of aluminosilicate gel induced a shift in the T–O (T = Si or Al) asymmetric stretching band, nearing a lower frequency. XRD showed an amorphous structure with phases, including quartz, mullite, hematite, and sodalite. The thermogravimetry and differential thermal analysis (TGA–DTA) indicated that the geopolymer samples were thermally stable. The electrical study concluded that the geopolymer possessed insulating properties. Full article

Bioceramics are the most promising materials used for hard tissue reconstruction. In this study, wollastonite/hydroxyapatite (HAp/WS)-type composite ceramic structures were synthesized with the aim of reaching a material with improved properties for use in bone tissue regeneration. The scaffolds were synthesized using a foam replica method, starting from ceramic powders with different mass ratios. These were subsequently studied and compared to identify the ideal mass ratio in terms bioactive character, appropriate mechanical properties, but also microstructural influence. The results indicate that all of the samples showed a highly porous microstructure with interconnected pores and high mineralization after 21 days of immersion in SBF. The porous structures with 90% and 70% mass contents of hydroxyapatite presented a well-defined structure and the highest values of mechanical compressive strength. Biocompatibility evaluation showed that osteoblast-like cells are able to penetrate the inner volume of the structures, exhibiting a biocompatible behavior in terms of morphological features and viability following 7 days of incubation. All results show that the porous composite ceramics with 90% and 70% mass contents of hydroxyapatite are promising materials for bone tissue regeneration. Full article

This study examines the impact of the impregnation of fireclay-based conventional (CC) and medium-cement castables (MCCs) with liquid sodium silicate glass under vacuum conditions. The goal is to assess how this treatment affects the physical and mechanical properties and durability (alkali and thermal shock resistance) of these castables used in biomass combustion boilers, where they are exposed to temperatures up to 1100 °C. The research work employs standard test methods to evaluate the physical and mechanical properties. Additionally, advanced techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and specific tests for alkali resistance and thermal shock resistance are used. The research findings suggest that impregnation with sodium silicate glass under vacuum significantly enhances the alkali resistance of both CC and MCCs. This improvement is primarily due to the reduction in porosity and the increase in density. SEM images reveal that the impregnated samples are coated with a glassy layer and the pores are partially filled with sodium silicate. Tests for alkali resistance demonstrate the formation of a protective glassy layer (with a thickness of 0.9–1.5 mm) on the castable surfaces, thereby reducing the further penetration of alkali into deeper layers of the samples. However, it is important to mention that the impregnated refractory castables have reduced resistance to thermal shock cycles. Full article

Selective emission of green light phosphor powder Y₄SiAlO₈N as the host material and Tb³⁺ as the activator was successfully achieved using spray pyrolysis (SP). Samples synthesized with various calcination temperatures and precursor concentrations indicated that the most suitable parameter for the synthesized powder is the calcination of 0.05 M Y_3.92SiAlO₈N:0.08Tb³⁺ at a temperature of 1600 °C. The effect of the selected parameters was substantiated by the high purity of the Y_3.92SiAlO₈N:0.08Tb³⁺ phase, as confirmed by X-ray diffraction (XRD) analysis. The Scherrer equation was used to calculate grain size. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) confirmed the presence of micron-sized particles, which matched well with the theoretical chemical composition. The specific surface area of the phosphor powder was determined using the Brunauer–Emmett–Teller method. Finally, fluorescence spectrometry was used to determine the luminescence properties. The correlation between the crystallinity of the phosphor powder and narrowing emission is also discussed. Full article

This article investigates the structures and conductive properties of polycrystals of Na₃Fe₂(PO₄)₃ obtained by solid-state and melt synthesis methods using concentrated optical radiation. It has been established that in the melt synthesis method, the material is synthesized under significantly non-equilibrium thermodynamic conditions, leading to the creation of deformations in the sample, which contribute to the enhancement of ionic conductivity. Additionally, the synthesis duration is reduced by half. Through a comparative assessment of the structural parameters and conductive properties of these materials, it is demonstrated that polycrystals obtained by the melt method exhibit better texture and higher ionic conductivity. The occurrence of deformations during the synthesis of α-Na₃Fe₂(PO₄)₃ under high temperature-gradient conditions indicates the elasticity of the crystalline framework {[Fe₂(PO₄)]³⁻}_3∞. It is concluded that the non-equilibrium thermodynamic conditions of α-Na₃Fe₂(PO₄)₃ synthesis promote the formation of deformations in the crystalline structure of polycrystals, leading to a partial increase in symmetry and ionic conductivity. Full article

Vat photopolymerization is an additive manufacturing technique that utilizes photosensitive resins to fabricate 3D polymeric objects with high precision. However, these objects often lack mechanical strength. This study investigated the strengthening of a resin based on epoxidized soybean oil acrylate, specifically designed for vat photopolymerization, by the in situ formation of hydroxyapatite nanocrystals. First, a stable alpha tricalcium phosphate (α-TCP)-resin feedstock mixture was developed (~30 vol.% α-TCP), which proved suitable for fabricating monoliths as well as complex triply periodic minimal surface (gyroid, diamond, and Schwarz) porous structures through vat photopolymerization. The results demonstrated that the incorporation of α-TCP particles led to a significant mechanical improvement of the resin. Second, post-printing hydrothermal treatments were utilized to transform the α-TCP particles into hydroxyapatite crystals within the resin. It was observed that the space between hydroxyapatite crystals within the composites was occupied by the cured resin, resulting in a more compact, stronger, and mechanically more reliable material than the porous hydroxyapatite produced by the hydrolysis of α-TCP mixed with water. Moreover, water absorption during the hydrothermal treatments caused the plasticization of the cured resin. As a consequence, the hydroxyapatite-resin composites displayed slightly lower mechanical properties compared to the as-printed α-TCP-resin composite. Full article

La_1.03Sr_1.97Al_0.97M_0.03O₅ (M = Fe, Co, Ni, and Cu) samples were synthesized using a citrate sol–gel method to develop a novel environmentally friendly inorganic green pigment. Among them, the Co-doped sample exhibited a vivid yellow, but not green. Then, (La_0.94Ca_0.06)Sr₂(Al_0.97Mn_0.03)O₅ was synthesized and characterized with respect to the crystal structure, optical properties, and color. The sample was obtained in a single-phase form and the lattice volume was smaller than that of the (La_0.94Ca_0.06)Sr₂AlO₅ sample, indicating that Mn ions in the lattice of the sample were pentavalent. The sample exhibited optical absorption at a wavelength below 400 nm and around 650 nm. These absorptions were attributed to the ligand, the metal charge transfer (LMCT), and d-d transitions of Mn⁵⁺. Because the green light corresponding to 500 to 560 nm was reflected strongly, the synthesized sample exhibited a bright green color. (La_0.94Ca_0.06)Sr₂(Al_0.97Mn_0.03)O₅ showed high brightness (L* = 50.1) and greenness (a* = −20.8), and these values were as high as those of the conventional green pigments such as chromium oxide and cobalt green. Therefore, the (La_0.94Ca_0.06)Sr₂(Al_0.97Mn_0.03)O₅ pigment is a potential candidate for a novel environmentally friendly inorganic green pigment. Full article