Ceramics

Composite electrolytes containing lithium ion conducting polymer matrix and ceramic filler are promising solid-state electrolytes for all solid-state lithium ion batteries due to their wide electrochemical stability window, high lithium ion conductivity and low electrode/electrolyte interfacial resistance. In this study, we report on the polymer infiltration of porous thin films of aluminum-doped cubic garnet fabricated via a combination of nebulized spray pyrolysis and spin coating with subsequent post annealing at 1173 K. This method offers a simple and easy route for the fabrication of a three-dimensional porous garnet network with a thickness in the range of 50 to 100 µm, which could be used as the ceramic backbone providing a continuous pathway for lithium ion transport in composite electrolytes. The porous microstructure of the fabricated thin films is confirmed via scanning electron microscopy. Ionic conductivity of the pristine films is determined via electrochemical impedance spectroscopy. We show that annealing times have a significant impact on the ionic conductivity of the films. The subsequent polymer infiltration of the porous garnet films shows a maximum ionic conductivity of 5.3 × 10⁻⁷ S cm⁻¹ at 298 K, which is six orders of magnitude higher than the pristine porous garnet film. Full article

Composite ceramics of stabilizer oxide coated ytterbia-samaria costabilized zirconia (1.5Yb1.5Sm-TZP) and 24–32 vol% of tungsten carbide as an electrically conductive dispersion were manufactured by hot pressing at 1300–1400 °C for 2 h at 60 MPa pressure. The materials were characterized with respect to microstructure, phase composition, mechanical properties and electrical discharge machinability by die sinking. Materials with a nanocomposite microstructure and a strength of up to 1700 MPa were obtained. An attractive toughness of 6–6.5 MPa√m is achieved as 40–50% of the zirconia transformed upon fracture. The materials show fair material removal rates of 1 mm³/min in die sinking. Smooth surfaces indicate a material removal mechanism dominated by melting. Full article

Brushing with bonded abrasives is a flexible finishing process used for the deburring and the rounding of workpiece edges as well as for the reduction of the surface roughness. Although industrially widespread, insufficient knowledge about the contact behavior of the abrasive filaments mainly causes applications to be based on experiential values. Therefore, this article aims to increase the applicability of physical process models by introducing a new prediction method, correlating the contact forces of single abrasive filaments, obtained by means of a multi-body simulation, with the experimentally determined process forces of full brushing tools during the surface finishing of ZrO₂. It was concluded that aggressive process parameters may not necessarily lead to maximum productivity due to increased tool wear, whereas less aggressive process parameters might yield equally high contact forces and thus higher productivity. Full article

Fine biocompatible powders with different phase compositions were obtained from a 0.5 M solution of ammonium sulfate (NH₄)₂SO₄ and calcium lactate Ca(C₃H₅O₃)₂. The powder after synthesis and drying at 40 °C included calcium sulfate dehydrate CaSO₄·2H₂O and calcite CaCO₃. The powder after heat treatment at 350 °C included β-hemihydrate calcium sulfate β-CaSO₄·0.5H₂O, γ-anhydrite calcium sulfate γ-CaSO₄ and calcite CaCO₃. The phase composition of powder heat-treated at 600 °C was presented as β-anhydrate calcium sulfate β-CaSO₄ and calcite CaCO₃. Increasing the temperature up to 800 °C leads to the sintering of a calcium sulfate powder consisting of β-anhydrite calcium sulfate β-CaSO₄ main phase and a tiny amount of calcium oxide CaO. The obtained fine biocompatible powders of calcium sulfate both after synthesis and after heat treatment at temperature not above 600 °C can be recommended as a filler for producing unique composites with inorganic (glass, ceramic, cement) or polymer matrices. Full article

Ceramic tiles and ceramic tile adhesives (CTA) are two impressive materials that have changed construction history. Ceramic tiles could not provide their beauty and durability for buildings when used as a covering both for the inside and exterior finishing without CTA. Nowadays, they are complex multi-component systems. Among the various CTAs, cementitious products are the most commonly used. This article presents an extensive review of the literature, showing how they are perceived in the scientific literature today. In this paper, an attempt is made to review individual adhesives’ ingredients’ effects on their properties, with particular reference to redispersible polymer powders and methylcellulose ethers. The article presents the basics of the CTAs, assessing and verifying the constancy of their performance in force in European Union countries. Furthermore, it gives a critical review of CTA’s normalized measurement methodologies. The study also draws attention to the need to consider measurement uncertainty in decision-making and conformity assessment, supported by an analysis of the results of multi-annual inter-laboratory studies and market surveillance tests. Future research suggestions are also made based on the review, mainly from the adhesive manufacturer’s perspective. Full article

Anisotropic CuCrO₂ thin films were successfully prepared on glass substrate by the electrospinning method followed by annealing at 600 °C. The directionality of the nanowires increased with increases in rotation speed. In addition, the structural formation and optoelectronic behavior of the CuCrO₂ thin films have been studied by X-ray powder diffraction studies, transmission electron microscopy, field emission scanning electron microscopy, and UV-vis spectroscopy. The X-ray diffraction studies revealed a delafossite properties of the CuCrO₂. The electrical conductivity in the parallel and vertical directions of the films produced at 2000–3000 rpm differed by two to three orders of magnitude. The optical transmittance properties of the CuCrO₂ thin films were improved by increasing the rotation speed. Full article

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10 wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, Q_S(I). The value of Q_S(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, Q_S(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep). Full article

The glass transition is described as a time- and history-independent singular event, which takes place in an interval dependent on the distribution width of molecular vibration amplitudes. The intrinsic glass transition is not seen as a relaxation phenomenon, but is characterized by a fixed volumetric state at the glass temperature Tg₀. The relaxation behavior of the transport properties depends on the distance to Tg₀. Free volume is redefined and its generation is the result of the fluctuating transfer of thermal energy into condensed matter and the resulting combined interactions between the vibration elements. This creates vacancies between the elements which are larger than the cross-section of an adjacent element or parts thereof. Possible shifts of molecules or molecular parts through such apertures depend on the size and axis orientation and do not require further energetic activation. After a displacement, additional volume is created by delays in occupying abandoned positions and restoring the energetic equilibrium. The different possibilities of axis orientation in space result in the different diffusive behavior of simple molecules and chain molecules, silicate network formers, and associated liquids. Glass transformation takes place at a critical volume Vg₀ when the cross-section of apertures becomes smaller than the cross-section of the smallest molecular parts. The glass transition temperature Tg₀ is assigned to Vg₀ and is therefore independent of molecular relaxation processes. Tg₀ is well above the Kauzmann and Vogel temperatures, usually just a few degrees below the conventionally measured glass temperature Tg_(qT). The specific volume at the two temperatures mentioned above cannot be achieved by a glass with an unordered structure but only with aligned molecular axes, i.e. in a crystalline state. Simple liquids consisting of non-spherical molecules additionally alter their behavior above Vg₀ at Vg_l where the biggest gaps are as small as the largest molecular diameter. Tg_l is located in the region of the crystalline melting point T_m. Both regions, above and below T_m, belong to different physical states and have to be treated separately. In the region close to Vg₀ respectively Tg₀, the distribution of vibration amplitudes has to be taken into account. The limiting volume Vg₀ and the formation of apertures larger than the cross-section of the vibrating elements or parts thereof, in conjunction with the distribution width of molecular vibrations as Vg₀ is approached, and the spatial orientation of the molecular axes is key to understanding the glass transition. Full article

Calcium phosphate is attracting attention as a bone repair material and a controlled-release carrier of various drugs such as bone disease therapeutic agents and anticancer agents. Compared with some bioabsorbable polymers, calcium phosphates have the advantage of preventing a pH decrease in the surrounding body fluid. However, there are few studies comparing the effect of supporting substances with different physicochemical properties on the production of calcium phosphate microspheres with different crystalline phases. In this study, we investigated conditions for obtaining low crystallinity apatite and octacalcium phosphate (OCP) microspheres from calcium carbonate microspheres with different crystalline structures using a simple phosphoric acid treatment. Furthermore, we investigated the adsorption and release behavior of different dyes and proteins from the apatite and OCP microspheres. Overall, the factors governing the adsorption and release behavior are different depending on the molecular size and surface charge of the dye and protein adsorbates. Full article

A series of binary oxide systems with Ca/Si molar ratios of 0.05, 0.1, 0.25, 0.5 and 1.0 have been synthesized by the sol-gel technique from tetraethyl orthosilicate (TEOS) and metallic calcium powder. Upon calcination, a side effect of wollastonite formation as a result of the reaction between the components of the material has been observed in the two calcium-richest systems. The increase in calcium content produces an effect of porosity promotion. At high calcium contents, the homogeneity of the systems is limited by the ability of silica to disperse the calcium component. The properties of these systems are determined by the silica surface coverage with a large amount of the scattered CaCO₃ fine microcrystallites (calcite), resulting from the phase segregation. The gels were characterized by X-ray powder diffraction, low temperature nitrogen adsorption, transmission and scanning electron microscopy (TEM, SEM and SEM/EDS), thermogravimetric analysis (TGA), and FT-IR spectra, to describe the parameters important from the point of view of their application as a support for metal-based catalysts. Full article

Aluminum hydroxide is an essential material for the industrial production of ceramics (especially insulators and refractories), desiccants, absorbents, flame retardants, filers for plastics and rubbers, catalysts, and various construction materials. The calcination process of Al(OH)₃ first induces dehydration and, finally, results in α-Al₂O₃ formation. Nevertheless, this process contains various intermediary steps and has been proven to be complicated due to the development of numerous transitional alumina. Each step of the investigation is vital for the entire process because the final properties of materials based on aluminum trihydroxide are determined by their phase composition, morphology, porosity, etc. In this paper, five dried, milled, and size-classified aluminum hydroxide specimens were thermally treated at 260, 300, and 400 °C; then, they were studied in order to identify the effects of temperature on their properties, such as particle morphology, specific surface area, pore size, and pore distribution. The major oxide compounds identified in all samples were characteristic of bauxite—namely, Al₂O₃ * 3H₂O, SiO₂, Fe₂O₃, Na₂O, and CaO. Particles with smaller sizes (<10 µm = 76.28%) presented the highest humidity content (~5 wt.%), while all samples registered a mass loss of ~25 wt.% on ignition at 400 °C. The identified particles had the shapes of hexagonal or quasi-hexagonal platelets and resulted in large spherulitic concretions. The obtained results suggest that ceramic powders calcined at 400 °C should be used for applications as adsorbents or catalysts due to their high specific area of about 200–240 m²/g and their small pore width (3–3.5 nm). Full article

A novel approach is demonstrated for the synthesis of the high entropy transition metal boride (Ta, Mo, Hf, Zr, Ti)B₂ using a single heating step enabled by microwave-induced plasma. The argon-rich plasma allows rapid boro-carbothermal reduction of a consolidated powder mixture containing the five metal oxides, blended with graphite and boron carbide (B₄C) as reducing agents. For plasma exposure as low as 1800 °C for 1 h, a single-phase hexagonal AlB₂-type structure forms, with an average particle size of 165 nm and with uniform distribution of the five metal cations in the microstructure. In contrast to primarily convection-based (e.g., vacuum furnace) methods that typically require a thermal reduction step followed by conversion to the single high-entropy phase at elevated temperature, the microwave approach enables rapid heating rates and reduced processing time in a single heating step. The high-entropy phase purity improves significantly with the increasing of the ball milling time of the oxide precursors from two to eight hours. However, further improvement in phase purity was not observed as a result of increasing the microwave processing temperature from 1800 to 2000 °C (for fixed ball milling time). The benefits of microwave plasma heating, in terms of allowing the combination of boro-carbothermal reduction and high entropy single-phase formation in a single heating step, are expected to accelerate progress in the field of high entropy ceramic materials. Full article

A detonation process based on 2,4,6 trinitrotoluene (TNT), used as an energetic reagent, was successfully implemented in the synthesis of a series of metal oxide ceramics. TNT offers better physicochemical and mechanical properties than the energetic compounds traditionally used in such processes, thus offering safer handling and transport conditions. The experimental procedure, which consisted to of mixing the energetic molecule with a ceramic salt, was simple to perform. The detonation products were characterized by X-ray diffraction, scanning and transmission electron microscopies, energy dispersive X-ray spectroscopy and nitrogen physisorption. The as-synthesized ceramic powders (CeO₂, HfO₂, Nb₂O₅, and In₂O₃) were crystalline and made of nano-sized quasi-spherical particles. This investigation provides an enhanced detonation synthesis process for elaborating ceramics. The majority of the oxide materials mentioned in this study had never previously been prepared by the detonation process. Full article

Octacalcium phosphate (OCP) is widely used in biomaterial fabrication by virtue of its unique crystal structure and low environmental loading. Although various ion and molecule substitution methods into the OCP unit lattice have been introduced, it remains unclear which factors and mechanisms dominate the substitution process. Experimental studies have indicated that Na alkali metal ions are substituted at the P3 PO₄ conjugated site in acidic to weakly acidic conditions and the P5 PO₄ conjugated site in neutral to weak basic conditions. Ionic species calculation methods have indicated that the pair ratios of Na and HPO₄²⁻ (NaHPO₄⁻) are small in acidic reacting solutions but large under weakly basic conditions. Consequently, the roles played by NaHPO₄⁻ and ionic pair formation processes are thought to dominate ion and molecule substitution into the OCP unit lattice. Such ionic pair formation strongly inhibits dicarboxylic acid substitution into the OCP unit lattice due to the replacement of the Ca ion, which conjugates P5 PO4 as an anchor of dicarboxylic acid. Full article

Additive manufacturing is well established for plastics and metals, and it gets more and more implemented in a variety of industrial processes. Beside these well-established material platforms, additive manufacturing processes are highly interesting for ceramics, especially regarding resource conservation and for the production of complex three-dimensional shapes and structures with specific feature sizes in the µm and mm range with high accuracy. The usage of ceramics in 3D printing is, however, just at the beginning of a technical implementation in a continuously and fast rising field of research and development. The flexible fabrication of highly complex and precise 3D structures by means of light-induced photopolymerization that are difficult to realize using traditional ceramic fabrication methods such as casting and machining is of high importance. Generally, slurry-based ceramic 3D printing technologies involve liquid or semi-liquid polymeric systems dispersed with ceramic particles as feedstock (inks or pastes), depending on the solid loading and viscosity of the system. This paper includes all types of photo-curable polymer-ceramic-mixtures (feedstock), while demonstrating our own work on 3D printed alumina toughened zirconia based ceramic slurries with light induced polymerization on the basis of two-photon absorption (TPA) for the first time. As a proven exemplary on cuboids with varying edge length and double pyramids in the µm-range we state that real 3D micro-stereolithographic fabrication of ceramic products will be generally possible in the near future by means of TPA. This technology enables the fabrication of 3D structures with high accuracy in comparison to ceramic technologies that apply single-photon excitation. In sum, our work is intended to contribute to the fundamental development of this technology for the representation of oxide-ceramic components (proof-of-principle) and helps to exploit the high potential of additive processes in the field of bio-ceramics in the medium to long-term future. Full article

This topical review describes the salient results of recent research on silicon nitride, a ceramic material with unique properties. The outcome of this ongoing research strongly encourages the use of monolithic silicon nitride and coatings as contemporary and future biomaterial for a variety of medical applications. Crystallographic structure, the synthesis and processing of monolithic structures and coatings, as well as examples of their medical applications that relate to spinal, orthopedic and dental implants, bone grafts and scaffolds, platforms for intelligent synthetic neural circuits, antibacterial and antiviral particles and coatings, optical biosensors, and nano-photonic waveguides for sophisticated medical diagnostic devices are all covered in the research reviewed herein. The examples provided convincingly show that silicon nitride is destined to become a leader to replace titanium and other entrenched biomaterials in many fields of medicine. Full article

This study was performed as an adjunct to an existing clinical study to validate the effect of veneer: framework thickness ratio on stress distribution in an implant-supported all-ceramic fixed partial denture. Two commercially available titanium dental implants with corresponding customized abutments and a patient-retrieved all-ceramic fixed partial denture were scanned using a high-resolution micro-CT scanner. Reconstructed 3D objects, along with a simulated bone surface, were incorporated into a non-manifold assembly and meshed simultaneously using Simpleware software (Synopsys Simpleware ScanIP Version P-2019.09; Mountain View, CA). Three such volume meshes (Model A, Model B, Model C) corresponding to veneer: framework thickness ratios of 3:1, 1:1, and 1:3 respectively were created, and exported to a finite element analysis software (ABAQUS). An axial load of 110 N was applied uniformly on the occlusal surfaces to calculate the static stresses and contour plots were generated in the post-processing module. From the data obtained, we observed optimum stress distribution in Model B. Also, the tensile stresses were concentrated in the posterior connector region of the prosthesis in all three models tested. Within the limitations of this study, we can conclude that equal thickness of veneer and framework layers would aid in better stress distribution. Full article

The spark plasma sintering (SPS) method is of great interest to the powder and powder metallurgy industry and material researchers of academia for both product manufacturing and advanced material research and development. Today in Japan, a number of SPS products for different industries have already been realized. Today’s fifth-generation SPS systems are capable of producing parts of increasing size, offering improved functionality, reproducibility, productivity, and cost. For instance, pure nano-Tungsten Carbide WC powder (no additives) is fully densified with a nano-grain-sized structure for glass lens application in the optics industry. The SPS is now moving from scientific academia and/or R&D proto-type materials level usage to practical industry use product stage utilizing in the field of electronics, automotive, mold and die, cutting tools, fine ceramics, clean energy, biomaterials industries, and others. This paper reviews and introduces the peculiar phenomenon of SPS and the progress of SPS technology, method, development of SPS systems, and its industrial product applications. Full article

Even though the (75 NaPO₃-25 CaF₂) (in mol%) glass can be heat-treated into transparent glass-ceramic with Er³⁺ doped CaF₂ crystals precipitating in the volume of the glass during heat-treatment, this glass was found to be a poor glass former, limiting its use as upconverter under 975 nm pumping. In this study, the impact of the glass composition on the thermal, optical and structural properties of the glass was investigated in order to understand how the glass composition can be tailored for the development of thermally stable upconverter glass-based material. The addition of MgO, Fe₂O₃ and Al₂O₃ in the NaPO₃-CaF₂ glass system increases the thermal stability of glass due to the depolymerization of the glass network. However, the changes in the glass composition also impacted on the nucleation and growth process. Indeed, CaF₂ and other crystals were found in the newly developed glasses after heat-treatment leading to glass-ceramics with lower intensity of upconversion than the (75 NaPO₃-25 CaF₂) glass-ceramic used as a reference. Glasses were also prepared with different concentrations of Er₂O₃ and ErF₃. These glasses were found to be promising as not only are they thermally stable, but they also exhibit green and red emission with high intensity under 975 nm pumping due to Er³⁺ clustering. Full article