Low-temperature Ceramics Research Articles

A niobium and tantalum co-doped perovskite electrolyte with high ionic conduction for low-temperature Ceramics Fuel cell

In recent studies, fast ionic conduction through surface doping and coating has been a favorite subject and has indicated a promising and stable strategy to optimize ions in the developed electrolytes for low-temperature ceramic fuel cells (LT-CFCs). We have designed co-doped perovskite (Nb/Ta-SrCoO3) to enhance further ionic properties using the Solid-state blending technique. The prepared SCNT (SrCoNb0.3Ta0.3O3) was used as an electrolyte sandwiched between symmetrical electrodes and delivered attractive fuel cell performance (650 mW/cm2) with better stability at the low operating temperature of 520 °C compared to other compositions of SCNT. The low grain boundary resistance manifests SCNT's high ionic conduction + microstructural properties, assisting with higher fuel cell performance. The co-doping enables the fermi-level to move towards the -ive side, establishing a space charge region constituting BIEF (built in electric field) and helping to enhance the ions' transportation through the surface and interface. This work thus points out a new type of electrolyte with a different working mechanism from previous studies. It indicates a feasible approach to developing high-performing and stable electrolytes for LT-CFCs.

Low-Temperature Calcium Phosphate Ceramics Can Modulate Monocytes and Macrophages Inflammatory Response In Vitro.

Creating bioactive materials for bone tissue regeneration and augmentation remains a pertinent challenge. One of the most promising and rapidly advancing approaches involves the use of low-temperature ceramics that closely mimic the natural composition of the extracellular matrix of native bone tissue, such as Hydroxyapatite (HAp) and its phase precursors (Dicalcium Phosphate Dihydrate-DCPD, Octacalcium Phosphate-OCP, etc.). However, despite significant scientific interest, the current knowledge and understanding remain limited regarding the impact of these ceramics not only on reparative histogenesis processes but also on the immunostimulation and initiation of local aseptic inflammation leading to material rejection. Using the stable cell models of monocyte-like (THP-1ATRA) and macrophage-like (THP-1PMA) cells under the conditions of LPS-induced model inflammation in vitro, the influence of DCPD, OCP, and HAp on cell viability, ROS and intracellular NO production, phagocytosis, and the secretion of pro-inflammatory cytokines was assessed. The results demonstrate that all investigated ceramic particles exhibit biological activity toward human macrophage and monocyte cells in vitro, potentially providing conditions necessary for bone tissue restoration/regeneration in the peri-implant environment in vivo. Among the studied ceramics, DCPD appears to be the most preferable for implantation in patients with latent inflammation or unpredictable immune status, as this ceramic had the most favorable overall impact on the investigated cellular models.

Composite Remineralization of Bone-Collagen Matrices by Low-Temperature Ceramics and Serum Albumin: A New Approach to the Creation of Highly Effective Osteoplastic Materials.

This study examined the effectiveness of coating demineralized bone matrix (DBM) with amorphous calcium phosphate (DBM + CaP), as well as a composite of DBM, calcium phosphate, and serum albumin (DBM + CaP + BSA). The intact structure of DBM promotes the transformation of amorphous calcium phosphate (CaP) into dicalcium phosphate dihydrate (DCPD) with a characteristic plate shape and particle size of 5-35 µm. The inclusion of BSA in the coating resulted in a better and more uniform distribution of CaP on the surface of DBM trabeculae. MG63 cells showed that both the obtained forms of CaP and its complex with BSA did not exhibit cytotoxicity up to a concentration of 10 mg/mL in vitro. Ectopic (subcutaneous) implantation in rats revealed pronounced biocompatibility, as well as strong osteoconductive, osteoinductive, and osteogenic effects for both DBM + CaP and DBM + CaP + BSA, but more pronounced effects for DBM + CaP + BSA. In addition, for the DBM + CaP + BSA samples, there was a pronounced full physiological intrafibrillar biomineralization and proangiogenic effect with the formation of bone-morrow-like niches, accompanied by pronounced processes of intramedullary hematopoiesis, indicating a powerful osteogenic effect of this composite.

Improving thermal insulation and fire resistance of ceramifiable EVA/ceramic hybrid composites via low temperature sintering and foaming strategy

Energy efficient buildings, propulsion components and thermal protection systems require materials with high thermal protective properties. Traditional polymer composites or ceramic materials have limited comprehensive applications because of their poor thermal protective properties or poor processability. Herein, a novel fire resistant and thermally insulating polymer/ceramic hybrid ceramifiable composite was developed based on low temperature sintering principle and foaming on fire strategy. Specifically, the influences of raw materials of low temperature ceramics, such as glass frit, phosphate, etc, on the properties of ceramifiable ethylene-vinyl acetate (EVA) composites were investigated. Its fire resistance and thermal insulation properties were evaluated by simulating different sintering environments. The results show that the ceramifiable composite exhibits the highest improvement in fire resistance because a crystalline phase was formed at high temperatures. Gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and EVA contributes to the formation of the porous structure in ceramic residues. The optimal system can resist above 1000 °C flame for 30 min without disintegration, and the temperature of the unfired side was maintained around 200 °C. The reliability of the strategy was verified by the effective medium theory model.

Showcasing the Potential of Iron-Doped Electrolytes to Enhance the Ionic Conduction for a Low-Temperature Ceramics Fuel Cell

Showcasing the Potential of Iron-Doped Electrolytes to Enhance the Ionic Conduction for a Low-Temperature Ceramics Fuel Cell

Laser assisted direct ink writing of multi‐material bismuth molybdate—silver artificial dielectrics for radio frequency applications

AbstractAdditive manufacturing of co‐fired low temperature ceramics offers a unique route for the fabrication of novel 3D radiofrequency (RF) and microwave components, embedded electronics and sensors. This study demonstrates the fabrication, materials analysis, and RF characterization of a multi‐material bismuth molybdate—silver (Bi2Mo2O9—Ag) artificial dielectric fabricated by laser assisted direct ink writing. The proposed fabrication technique enables 3D printing of dissimilar materials while minimizing inter‐material diffusion through the liquid phases. The permittivity of the artificial dielectrics increased up to 99% over the investigated frequency range (8–12 GHz) compared to the fabricated pure ceramic sample.

Low-Temperature Magnesium Calcium Phosphate Ceramics with Adjustable Resorption Rate

Low-temperature ceramics based on magnesium calcium phosphate cement are a promising resorbable material for bone tissue restoration with the possibility of functionalization. The replacement of the magnesium Mg2+ ion with a calcium Ca2+ ion at the stage of preparation of the precursor leads to the production of multiphase ceramics containing phases of brushite, monetite, and newberyite, with different dissolution rates. Multiphase ceramics leads to volumetric resorption with preservation of their geometric shape, which was confirmed by the results of an evaluation of the output of magnesium Mg2+ and calcium Ca2+ ions into the contact solution of the ceramics and the X-ray density of ceramic samples during subcutaneous implantation. The combined introduction of sodium pyrophosphate decahydrate and citric acid monohydrate as setting inhibitors neutralizes their insignificant negative effect on the physico-chemical properties of ceramics (strength, pH, porosity), determining the optimal composition. In vivo experiments with setting inhibitors in the composition of ceramics showed a different biological response, affecting the rate of resorption on par with magnesium ions. Preliminary data on biocompatibility and solubility determined magnesium-calcium phosphate ceramics containing additives that regulate setting to be a potential material for bone tissue restoration and a vector for further research, including in orthotopic implantation models.

The effect of natural fiber ratio on mechanical properties of kaolin/fly–ash at low temperature ceramics

This study aims to increase the feasibility of ceramics at low temperature using natural fibers. The ceramics (Ce) were prepared by mixing a powder of kaolin and fly–ash at an equal ratio of 50:50 wt.%. The mixture was milled by ball–milling technique. The natural fibers ceramics (CeNF) were created by adding local pineapple leaves to kaolin and fly–ash powder. Scanning electron microscopy (SEM) was used to amorphous observation and particle size determination. The compositions of Ce and CeNF were investigated by using X–ray diffraction (XRD) technique. The mechanical properties of ceramics were determined by hardness and density test. The results showed that the grinding of kaolin and fly–ash for 4 h produced the highest strength Ce. For the addition of local pineapple leaves at 2 wt.%, the strength could be increased from 92.9 kgf to 118.3 kgf.

Determining patterns in the formation of cordierite phase during the synthesis of density-sintered low-temperature ceramics based on glasses of the MgO–Al2O3–SiO2 system

The search for effective modifiers of the structure of densely baked cordierite ceramics to reduce the firing temperature is a relevant task but typically requires a large amount of experimental research. The object of this study is the reaction of the formation of the cordierite phase with the participation of glass components of the eutectic compositions of the MgO– Al2O3–SiO2 system under low-temperature firing conditions. In this case, thermodynamic analysis was used as a tool to assess the probability of chemical reactions. Thermodynamic analysis can significantly reduce the volume of the experimental sample. This paper reports the results of theoretical and experimental studies into the features of the course of chemical reactions with the participation of glass components of eutectic compositions of the MgO–Al2O3–SiO2 system. It was revealed that once the stoichiometric ratio is maintained, the resulting product of the interaction between the components of eutectic glasses of the MgO–Al2O3–SiO2 system with charging components is cordierite. Changes in the mineralogical composition of cordierite compositions depending on the firing temperature have been determined. The formation of the cordierite phase is preceded by the process of transformation of meta kaolinite Al2O3·2SiO2, which is a product of kaolin dehydration, into mullite 3Al2O3·2SiO2. Subsequently, the formation of cordierite (in addition to crystallizing directly from eutectic glasses) occurs with the participation of the mullite phase. The formation of the cordierite phase occurs in several stages and is completed at a temperature of 1300 °C. The established features of the reactions of cordierite formation make it possible to determine the most optimal compositions for glasses of the MgO–Al2O3–SiO2 system to obtain low-temperature cordierite ceramics with a high degree of sintering. At the same time, it is also possible to control the phase composition of ceramics and its properties

CERAMIC MATERIALS BASED ON Al2O3 FOR LTCC APPLICATION

In the paper presents an overview on the topic of obtaining high-temperature (HTCC) and low-temperature (LTCC) ceramics. The topic observe transition from a high-temperature process of obtaining ceramic materials to a low-temperature. Typical LTCC production process and the characteristics and properties of a “classic” glass ceramic composite described hereof. The main directions of application glass ceramics obtained by LTCC technology are shown.

Stereolithographic additive manufacturing of Luneburg lens using Al2O3-based low sintering temperature ceramics for 5G MIMO antenna

In this paper, we provided a manufacturing method for low-sintering-temperature radio frequency (RF) devices by stereolithographic (SLA) printing. The effect of ceramic powder percentage on rheological properties, curing behavior, sintering properties, microstructure, and dielectric properties was discussed. With the proportion of ceramic powder ranging from 60 wt% to 75 wt%, the viscosity of slurries declined, the sintering shrinkage rate varied from 21.61% to 15.83%, the dielectric constant raised from 5.22 to 6.64, and the dielectric loss initially reached the optimum value of 0.0024 and then deteriorated to 0.0035. The maximum solid content of slurries was 75 wt%, and the printable viscosity should be below 7.33 Pa·s. At the mass ratio of 65:35, the samples sintered at 850 °C showed good properties: a density of 3.0135 g·cm−3, a dielectric constant of 5.56, a low dielectric loss of 2.4 × 10−3, and τf = −32.76 ppm/°C. The printed Luneburg lens showed a gain enhancement of over 5 dB, by using a 10 dBi standard gain horn antenna as a feed source. Thus, this research established a foundation for the fabrication of ceramic RF devices with high-performance, complex structures, and low sintering temperature via SLA printing.

Effect of Complex Additives Based on Iron, Cobalt, and Manganese Oxides and Sodium Silicate on the Sintering and Properties of Low-Temperature Ceramics 3Y–TZP–Al2O3

Effect of Complex Additives Based on Iron, Cobalt, and Manganese Oxides and Sodium Silicate on the Sintering and Properties of Low-Temperature Ceramics 3Y–TZP–Al2O3

Retention of arsenic using alkali- and acid-bonded low temperature ceramics

ABSTRACT Immobilisation of AsIII and AsV using alkali- and acid-bonded low temperature ceramics (LTCs), respectively, has been investigated. Arsenic was loaded into these matrices as solubilised arsenic or as a solid via precipitation with a metal nitrate. Where appropriate, samples were heated to 1000°C to consolidate their microstructure and reduce their open porosity. Samples were assessed according to microstructural characterisation and standard leaching protocols. Alkali-bonded LTCs, even after the application of a thermal treatment, did not bind arsenic sufficiently to pass a TCLP protocol, whereas acid bonded LTCs showed better potential for immobilising As. At a loading of 5 wt% As2O5, a TCLP leach test on an acid bonded LTC resulted in As levels of 7 ppm, close to the regulatory limit of 5 ppm As.

Prospects for design and construction development of integral circuits of LC–filters based on the modern dielectric materials

An analysis of design and technological solutions related to the production of integrated microwave filters based on modern materials - liquid-crystalline polymers (LCP) and low-temperature ceramics (LTCC) is considered. An important factor in the design of integrated filters based on multilayer printed circuit boards is the limited choice of designs for inductive and capacitive elements. It is proposed to use dielectric materials with more stable parameters and a wide range of operating frequencies (LCP up to 20 GHz, and LTCC up to 40 GHz). The results of comparison of the manufacturing process of microwave filters based on LCP and LTCC technologies are shown. One of the possible schemes and designs of a bandpass filter with a cut-off frequency of 2.9 GHz, a bandwidth of 500 MHz, and an insertion loss of about 1 dB is demonstrated. Experimental characteristics based on computer simulation of the microwave filter are presented. It is concluded that the use of LTCC-technology is preferable for solving the problem of microminiaturization of microwave filters, and the use of LCP-technology is expedient for creating narrower-band filters intended for operation in a higher frequency range of microwave filters.

Sol - gel method for producing of glass binding in the Li2O - Al2O3 - SiO2 system for ceramic materials

The results of glass binding obtaining in the Li2O — Al2O3 — SiO2 system for ceramic materials are presented in the article. The lithium aluminum silicate system was chosen taking into account the low temperature expansion coefficients of crystalline phases that form in it. This will allow controlling the thermal expansion of materials into which the glass binding will be introduced. A sol - gel method based on ethyl silicate and soluble salts of the corresponding oxides is proposed as a method for producing of glass binding. This method is more rational in comparison with the traditional method of glass melting due to low energy costs. Also, the method allows to obtain a more uniform and active product.
 The effect of glass binding on the properties of ceramic materials for various purposes has been investigated. As such materials, low-temperature electrotechnical porcelain, quartz ceramics, and engobe coatings were chosen. The glass binding was introduced into the raw material charge of these materials in an amount of 5 wt. %. Further, the properties of calcined product without additives and with additives under the same conditions were compared.
 The intense fluxing effect of glass binding during the formation of electrical porcelain has been established. The glass binding reinforces the effect of natural fluxes (pegmatites) that are present in the basic composition of the mass. This contributes to the material compaction during firing. The formation of eucryptite and spodumene helps to reduce the thermal expansion of material. The introduction of glass binding into the engobe led to a less intense compaction of its structure. This was observed due to an insufficient amount of the added glass binding for this type of material. In the composition of quartz ceramics, glass binding contributed to the material sintering, but the thermal properties were deteriorated.
 Thus, the sintering results of ceramic material with the introduction of glass binding in the charge composition are positive. However, sintering significantly depends on the material type. The glass binding stimulates the formation of a melt in which solid finely dispersed components of the ceramic mass dissolve. This contributes to the formation of a dense durable ceramic.

Multi-material additive manufacturing of low sintering temperature Bi2Mo2O9 ceramics with Ag floating electrodes by selective laser burnout

ABSTRACTAdditive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi2Mo2O9 (BMO, sintering temperature = 620–650°C, εr = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (εr) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a post-printing sintering step to create BMO/Ag 3D structures was thus demonstrated.

Phase Composition and Properties of the Low-Temperature Structural Ceramics in the Clay-Calcium Containing Material System

The ceramic materials structure formation with the given esthetics-consumer properties is the most important mission of the modern production and should be based on the knowledge of physical and chemical processes, which are flowing past in masses based on the systems differing in the content of alkaline, alkaline-earth oxides and oxides of iron in clay raw materials.

Recycling lithium mine tailings in the production of low temperature (700–900 °C) ceramics: Effect of ladle slag and sodium compounds on the processing and final properties

This paper deals with the valorization of quartz and felspar rich lithium mine tailings (QFS) in the development of construction materials. Ladle slag was used as green strength increasing agent. Sodium hydroxide and carbonate were used as fluxing agents to allow sintering at 700–900 °C. Of these, sodium hydroxide was found to be the more efficient. The sintered ceramics were characterized by X-ray diffraction, scanning electron microscopy, compressive test, water absorption, apparent density and dilatometry; the results were found to comply with ASTM C62-99 specifications for building brick, and interesting for a sustainable use of resources.

Determining Factors in the Formation of Low-Temperature Ceramics Structure

A computer simulation approach to sintering of low-temperature ceramics has been developed within the framework of the micromechanics of heterogeneous media. It is taken into account that the reinforcement of the refractory component can be formed at different structural levels determined by the particle fraction size. The formation of the reinforcement of interacting refractory particles in individual sintered layer mesovolumes causes the pore structure formation, and the heterogeneous pore distribution through the mixture layer thickness in the initial compact determines the shrinkage anisotropy of the sintered ceramics. The conditions are determined in which the reinforcement of refractory components is formed at different structural levels. An initial block of layers formed of a mixture of refractory and low-melting components with a binder was obtained in the laboratory. Low-temperature ceramics samples were synthesized. The structure of a separate layer of the sintered ceramics was examined by X-ray tomography. Experiments were conducted to confirm the reliability of the sintering simulation results obtained with taking into account the effect of the heterogeneous component distribution and fractional composition of the initial mixture on the properties of low-temperature ceramics.

Simulation of sintering of low-temperature ceramic products formed by additive technology

Computer simulation methods have been applied to study the processes of low-temperature ceramics synthesis corresponding to technological processes. The simulation is performed for micron- and nanosized powders with different morphology. The synthesized composite medium has the characteristics (microlayer thickness, pore volume fraction, etc.) that reflect imperfections in the initial dispersion. The developed model allows one to examine the governing factors of physical and chemical processes in low-temperature ceramics synthesis.