Hydroxyapatite is a versatile material with strong potential for environmental remediation, yet its large-scale use is limited by the cost and purity requirements of conventional precursors. This study introduces a low-cost and sustainable synthesis route for hydroxyapatite using technical-grade phosphoric acid, highlighting the beneficial role of industrial impurities in tuning its structural, optical, and adsorption properties, thus promoting its broader use in environmental applications. Hydroxyapatite powders were synthesized from calcium hydroxide and technical-grade phosphoric acid (Ca/P = 1.67) at 25 °C in aqueous medium, then dried and calcined (500–1100 °C). Structural, chemical, and optical analyses revealed single-phase nano-hydroxyapatite (12.6–57.3 nm) with high surface area (176.95 m²·g-1) and strong wettability. The optical band gap decreased from 4.5 ± 0.4 eV to 3.2 ± 0.4 eV after calcination, indicating defect-induced electronic modification. The poorly crystallized hydroxyapatite exhibited excellent Cd²⁺ and Pb²⁺ adsorption (99 % and 97 % removal in 100 min) but limited bisphenol A elimination (2.73 % in 180 min).
Achim Rösiger, Stefan Kleiner, Simon Unseld
et al.
In manufacturing of UHTCMC components machining is often one of the ultimate process steps and have then important objectives, including dimensional tolerances and surface roughness. Additionally, the prevention of any damage to high-value components is very important. In this study, the machining of 0/90°-C/ZrB2 composite is investigated to understand some fundamental mechanisms involved. Specifically, the material removal mechanisms of the heterogeneous and anisotropic material structure through scratch tests are explored. Grinding experiments are conducted to evaluate surface quality, measuring surface roughness and grinding forces. This allows an interpretation of machining induced damage mechanisms of UHTCMCs. 0/90°-C/ZrB2 shows generally brittle removal mechanisms and influence of fiber cutting direction. Scratching depth and speed influences less on damage. This was also found in the grinding experiments, where roughness remains almost constant.
Abstract As a subserie of the dental ceramic material family, glass–ceramics are favored for their excellent aesthetic properties. The feasibility of current commercially available dental glass–ceramics applications has been proven, while the assurance and development of more functional properties for them are still being explored. Effective utilization of various modification mechanisms by adjusting the chemical composition and microstructure is essential to improve the mechanical properties, aesthetic properties, and other properties such as biocompatibility of dental restorative materials. Among them, the mechanical properties of restorations should take into account the mechanical properties of glass ceramics and the final restoration (restoration and tooth set) in the mechanical behavior. This paper provides an overview of the chemical composition design, classification of microstructure, property requirements, and strengthening methods applied to dental glass–ceramics, including ion exchange, chain effects, heat treatment modulation, and strengthening mechanisms. In addition, research on traditional hot pressing, subtractive manufacturing, and newly developed additive manufacturing in glass–ceramics are systematically presented. Finally, the tendency of dental glass–ceramics was forecasted by analyzing the relationship between glass–ceramic composition, process, and mechanical properties.
This study focused on achieving high ionic conductivity in Li-La-TiO (LLTO) solid electrolyte. To enhance ionic conductivity, the synthesis reaction was optimized by controlling the composite crystal structure of TiO2 at the B-site of the perovskite (ABO3) structured LLTO, incorporating rutile, brookite, and anatase phases. The solid-phase LLTO, synthesized utilizing the core – shell structured composite-phase TiO2 developed in this study for the first time, successfully transformed its crystal structure to β-LLTO (tetragonal to cubic). This resulted in a significant improvement in ionic conductivity (i.e. 1.11 × 10−4 Scm−1). The study findings confirmed that the composite crystal structure TiO2 used in the solid-phase synthesis of LLTO induced an increase in oxygen vacancies during the synthesis process, thereby reducing the step-free energy required for the final synthesis.
Abstract As the core component of lightning arrester, the performance of ZnO varistor directly affects the protection level of lightning arrester. Under the action of long‐term AC voltage, the varistors are prone to AC aging, which leads to the deterioration of its performance parameters and microstructure, resulting in the failure of the varistors. In this paper, the effects of MnO2 doping on the voltammetry and double Schottky barrier characteristics of ZnO varistors under AC were studied by means of C--V, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy characteristic testing. The AC accelerated aging test was carried out for 168 h under 135∘C and 0.85 ratio of peak voltage. The results showed that the introduction of Mn4+ inhibited the migration of interstitial zinc ions to grain boundaries and decreased the AC aging rate. The aging rate was lowest when 1.5 mol% MnO2 was doped.
Ivan Zorin, Dominik Brouczek, Sebastian Geier
et al.
In the past decade, significant progress has been made in ceramics additive manufacturing (AM). Material research and the rapid evolution of high-resolution printing technologies enabled the production of high-quality, high-precision, complex-structured ceramic objects. In this contribution, we propose a contactless, non-destructive method of mid-infrared optical coherence tomography (mid-IR OCT) for at-line inspection and quality assurance of AM ceramics. The OCT system operates in the spectral range from 3.15 μm to 4.2 μm featuring extended probing depth into porous ceramics. The spatial resolution of the mid-IR OCT system is suited to most of AM techniques: the axial resolution (determined by the coherence length) is 8 μm; the lateral resolution is around 40 μm (determined by the size of the focused beam). The capabilities of the method are demonstrated by imaging diverse high-scattering single and multi-component samples (in both green and sintered states) fabricated by means of lithography-based ceramics manufacturing. The selected materials are alumina and zirconia, the gold standard in AM. Some features of interest, such as local changes in porosity, surface and sub-surface defects and layer structure, were accessed and analyzed.
Marco Mariani, Guillermo Frias Blanco, Elisa Mercadelli
et al.
Our work describes an optimised procedure for granulating nanometric and fine micrometric particles by spray-drying to achieve ready-to-print α-Al2O3 powders. The study started by identifying raw materials suited for the process through complete characterisation of particles shape, size, and surface properties. Then, dispersion in diluted and concentrated water-based suspensions was achieved thanks to polyethyleneimine and the effect of gradual dispersant addition was assessed by determining ζ potential and aggregates size variation. Suspensions rheology was studied and modelled through Krieger-Dougherty equation to identify the maximum solid loading allowing sufficient feeding through the spray-dryer nozzle. Finally, optimisation of the granulation conditions was performed.The procedure has allowed to achieve size distributions with D90 < 50 μm and Hausner ratio <1.3 ensuring sufficient flowability. The granulated powders were printed and the porosity evolution of the samples after sintering was studied by mercury intrusion porosimetry and SEM analysis.
Amirhosein Paryab, Toktam Godary, Rashid Khalilifard
et al.
In the bone tissue engineering field (BTE), it is of significant importance to develop bioactive multifunctional scaffolds with enhanced osteoconductivity, osteoinductivity, and antibacterial properties required for lost bone tissue regeneration. In this work, a bioactive glass-ceramic scaffold was manufactured via a novel polymer-derived ceramics (PDC) manufacturing method. To gain antibacterial properties, the silver ions were incorporated in controlled amount along with other precursors in the PDC processing stage. Microstructural and structural properties of the fabricated silicate-phosphate glass-ceramic scaffold were evaluated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis, respectively. Furthermore, bioactivity, antibacterial, and cytotoxicity evaluation of PDC scaffolds were conducted. The microstructural analysis determined that scaffolds have interconnected porous network with two different pore range size favorable for osteointegration and bone formation. The structural analysis confirmed that fabricated glass-ceramic scaffolds contain bioactive octacalcium phosphate (OCP) phase responsible for enhanced bioactivity and HCA formation during the immersing of scaffolds in simulated body fluid (SBF) for several days. Moreover, PDC scaffolds with Ag nanoparticles showed considerable antibacterial properties against Gram-negative Klebsiella pneumoniae and Gram-positive Staphylococcus aureus bacteria cells. This study has demonstrated that it is possible to develop a novel group of antibacterial and bioactive Ag incorporated silicate-phosphate glass-ceramic scaffolds for BTE applications, such that, it was verified in vivo. Resumen: En el campo de la ingeniería de tejido óseo (BTE), es de gran importancia desarrollar andamios multifuncionales bioactivos con osteoconductividad mejorada, osteoinductividad y propiedades antibacterianas necesarias para la regeneración del tejido óseo perdido. En este trabajo, se fabricó un andamio de vitrocerámica bioactive mediante un nuevo método de fabricación de cerámica derivada de polímeros (PDC). Para obtener propiedades antibacterianas, los iones de plata se incorporaron en una cantidad controlada junto con otros precursores en la etapa de procesamiento de PDC. Las propiedades microestructurales y estructurales del armazón de cerámica de vidrio de silicato-fosfato fabricado se evaluaron mediante microscopía electrónica de barrido (SEM) equipada con espectroscopía de dispersión de energía (EDS) y análisis de difracción de rayos X (XRD), respectivamente. Además, se llevó a cabo una evaluación de bioactividad, antibacteriana y citotoxicidad de los andamios de PDC. El análisis microestructural determinó que los andamios tienen una red porosa interconectada con dos tamaños de rango de poros diferentes favorables para la osteointegración y la formación de hueso. El análisis estructural confirmó que los andamios de vitrocerámica fabricados contienen una fase de fosfato octacálcico bioactivo (OCP) responsable de la bioactividad mejorada y la formación de HA durante la inmersión de los andamios en fluido corporal simulado (SBF) durante varios días. Además, los andamios de PDC con nanopartículas de Ag mostraron considerable propiedades antibacterianas contra las células de bacterias Gram-negativas Klebsiella pneumoniae y Gram-positivas Staphylococcus aureus. Este estudio ha demostrado que es posible desarrollar un grupo novedoso de andamios de vitrocerámica de silicato-fosfato incorporados en Ag antibacterianos y bioactivos para aplicaciones de BTE, de manera que se verificó in vivo.
Katharina Walbrück, Lisabeth Drewler, Steffen Witzleben
et al.
New sustainable, environmentally friendly materials for thermal insulation of buildings are necessary to reduce their carbon footprints. In this study, Miscanthus fiber-reinforced geopolymer composites, foamed with sodium dodecyl sulfate (SDS), were developed using fly ash as a geopolymer precursor. The effects of fiber content, fiber size, curing temperature, foaming agent content, fumed silica specific surface area and fumed silica content on thermal conductivity and compressive strength were evaluated using a Plackett-Burman design of experiment. Furthermore, the microstructure of geopolymer composites was investigated using X-ray diffraction (XRD), X-ray micro-computed tomography (μCT) and scanning electron microscopy (SEM). The measured characteristic values were in the following ranges: Thermal conductivity 0.057 W (m K)−1 to 0.127 W (m K)−1, compressive strength 0.007 MPa–0.719 MPa and porosity 49 vol% to 76 vol%. The results reveal an enhancement of thermal conductivity by elevated fiber size and foaming agent content. In contrast, the compressive strength is enhanced by high fiber content. Additionally, SEM images indicate a good interaction between the fibers and the geopolymer matrix, because nearly the whole fiber surface is covered by the geopolymer.
Daniel Ursu, Anamaria Dabici, Marinela Miclau
et al.
We report for the first time the fabrication of hierarchical ordered superstructure CuB2O4 with flower-like morphology via a one-step, low temperature hydrothermal method. The tetragonal structure of CuB2O4 was determined by X-ray diffraction and high-resolution transmission electron microscopy. Optical measurements attested of the quality of the fabricated CuB2O4 and high temperature X-ray diffraction confirmed its thermal stability up to 600 °C. The oriented attachment growth and the hierarchical self-assembly of micrometer-sized platelets producing hierarchical superstructures with flower-like morphology are designed by pH of the hydrothermal solution. The excellent band gap, high thermal stability and hierarchical structure of the CuB2O4 are promising for the photovoltaic and photocatalytic applications.
Paul Fourton, Keyvan Piroird, Matteo Ciccotti
et al.
In laminated glass under impact, most of the energy dissipation occurs in the coupled delamination and deformation of the polymer interlayer. The strong dependency of these mechanisms on interlayer nature, on loading rate and on temperature is known: however, the effect of the interfacial adhesion is unexplored. In this work, a surface modification technique is proposed, along with a mechanical characterization of the debonding with the Through Crack Tensile Test. We show that changing adhesion mostly affects dissipation close to the delamination front, while dissipation in the volume of the PVB interlayer seems unaffected, which we attribute to the competition between the changes in both strain and strain rate in the viscoelastic interlayer. Finally, we discuss the experimental observation of the limits of the steady-state debonding regime, related to the competition between adhesive crack propagation and cohesive failure in the interlayer.
Paulina Bukieda, Michael Engelmann, Bernhard Weller
et al.
Research has shown that the general approach to determine the bending strength of thermally curved glass with the aid of the four-point bending test for flat glass according to EN 1288-3 is applicable. At the moment, however, there is no statutory method available for directly extrapolating the breaking strain from the breaking load without the use of expensive strain gauges. Such a method is developed by means of an experimental and numerical study in a research project between the Bundesverband Flachglas e.V. (Federal Flat Glass Association) and the Fachverband Konstruktiver Glasbau e.V. (Professional Association Structural Glass Constructions), the Institute of Building Construction at the Technische Universität Dresden and four glass bending specialists. Moreover, it will provide the basis for testing cylindrically curved glass of any bending radius. The project partners have already submitted a proposal for a new standard to the Deutsches Institut für Normung e.V. (German Institute for Standardisation). The paper gives the theoretical background for determining the strength of flat glass according to EN 1288‑3 and quantifies the additional effects for the testing of thermally curved glass. Furthermore, the testing method of the executed experimental study on thermally curved glass is described. The range of parameters for the tested specimens included the glass thickness from 3 mm to 12 mm and the bending radii from 400 mm to 2000 mm. We recorded the strain at selected points at the tensioned side and the input force for each specimen. The measured relation between strain and load validates a numerical model, which is able to depict the actual two-dimensional stress distribution for thermally curved glass and includes non-linear aspects. The model allows for the determination of correction factors. With those, the bending strength of thermally curved glass can be calculated by measuring merely the input force during the four-point bending tests. The correction factors are summarised in charts depending on the radius and the thickness of the glass sample.
Abstract Zirconium nitride (ZrN) ceramics were prepared via hot pressed sintering (HP) at 1750 °C in N2 atmosphere with ZrO2–Y2O3 as sintering additive. X-ray diffraction was applied to analyze the phase composition of the as-prepared ceramics to study the high temperature phase relation in ZrN–ZrO2–Y2O3 ternary system and establish ZrN–ZrO2–Y2O3 ternary phase diagrams. The results show that ZrN and tetragonal ZrO2 (t-ZrO2) solid solution, face-centered cubic ZrO2 (c-ZrO2) solid solution, body-centered cubic Y2O3 (c-Y2O3) solid solution coexist in the system of ZrN–ZrO2–Y2O3.
A novel green nonaqueous sol-gel process was developed to prepare 3 mol% Y2O3-doped ZrO2 nanopowder from zirconium oxychloride and without need for washing of the obtained particles. It was shown that highly dispersive nanometer-scale zirconia powder with the particle size of 15–25 nm and BET surface area of 41.2 m2/g can be prepared. The sintering behaviour was also investigated. Density of the translucent body sintered at 1400 °C is 98.7 ± 0.3% of its theoretical density and the surface and cross section areas are dense without holes or other defects. The bending strength of the sintered sample is 928 ± 64 MPa.
Cordierite ceramic membranes were manufactured from natural clay, oxides and organic wastes as pore forming agents. Mixtures aforementioned materials with the pore-forming agents (up to 10 wt.%) were investigated in the range 1000–1200 °C using thermal analysis, X-ray diffraction, scanning electron microscopy, mercury porosimetry and filtration tests. Physical properties (density, water absorption and bending strength) were correlated to the processing factors (pore-forming agent addition, firing temperature and soaking time). The results showed that cordierite together with spinel, diopside and clinoenstatite neoformed. SEM analysis revealed heterogeneous aspects. The results of the response surface methodology showed that the variations of physical properties versus processing parameters were well described by the used polynomial model. The addition of pore forming agent and temperature were the most influential factors. Filtration tests were performed on the best performing sample. The results allowed to testify that these membranes could be used in waste water treatment.
The present work investigates the effect of precursor concentration (mc) on the structural, optical, morphological and electrical conductivity properties of In2S3 thin films grown on amorphous glass substrates by nebulized spray pyrolysis (NSP) technique. The mixed phase of cubic and tetragonal structure of In2S3 thin films at higher concentration has been observed by X-ray diffraction pattern. The reduced strain by increasing the precursor concentration increased the average crystallite from 17.8 to 28.9 nm. The energy dispersive analysis by X-ray (EDAX) studies confirmed the presence of In and S. The transmittance, optical direct band gap energy, Urbach energy and skin depth of In2S3 films have been analyzed by optical absorption spectra. The better conductivity and mobility noticed at mc = 0.15 M are explained by carrier concentration and crystallite. Better optical and electrical conductivity behaviour of In2S3 thin film sample proposes for effective solar cell fabrication.
3D Ti-mesh has been coated with bioceramics under different coating conditions, such as material compositions and micro-porosity, using a dip casting method. Hydroxyapatite (HA), micro-HA particles (HAp), a bioglass (BG) and their different mixtures together with polymer additives were used to control HA-coating microstructures. Layered composites with the following coating-to-substrate designs, such as BG/Ti, HA + BG/BG/Ti and HAp + BG/BG/Ti, were fabricated. The bioactivity of these coated composites and the uncoated Ti-mesh substrate was then investigated in a simulated body fluid (SBF). The Ti-mesh substrate and BG/Ti composite did not induce biomimetic apatite deposition when they were immersed in SBF for the selected BG, a pressable dental ceramic, used in this study. After seven days in SBF, an apatite layer was formed on both HA + BG/BG/Ti and HAp + BG/BG/Ti composites. The difference is the apatite layer on the HAp + BG/BG/Ti composite was rougher and contained more micro-pores, while the apatite layer on the HA + BG/BG/Ti composite was dense and smooth. The formation of biomimetic apatite, being more bioresorbable, is favored for bone regeneration.
Romero-Gómez, P., González, J. C., Bustamante, A.
et al.
It has been performed a kinetic study of the thermal transformation of Limonite [FeO(OH).nH<sub>2</sub>O] by thermal gravimetric analysis (TGA), thermal X-ray Diffraction (XRD) and μ-Raman spectroscopy. The mineral was extracted from the Taraco District, Huancané Province, Puno region (Peru). Powdered XRD identify goethite phase as the main mineralogical component besides quartz. It was subjected to <i>in-situ</i> thermal treatment in the range of temperatures 100 to 500 ºC in air and an inert atmosphere (nitrogen). The goethite phase remains stable from room temperature until 200 ºC. From 250ºC there is a phase transformation α-FeO(OH) → α-Fe<sub>2</sub>O<sub>3</sub> with 8 wt % weight loss and a chromatic change, <i>i.e.</i>, the change of the hydroxylated goethite phase (yellow) to oxided hematite phase (red), as evidenced by the TGA and evolution of the XRD profiles. Moreover, the μ-Raman spectra of the <i>in-situ</i> thermal treatment corroborate that there is a transition at 290 ºC by the transformation of the characteristic Raman bands of the goethite to hematite phase, in the frequency range from 200 to 1800cm<sup>-1</sup>.<br><br>Se ha realizado un estudio cinético de la transformación térmica de limonita [FeO(OH).nH<sub>2</sub>O] mediante análisis térmico gravimétrico (TGA), termodifracción de rayos X (DRX) y espectroscopía μ-Raman. La muestra estudiada fue extraída de un yacimiento en el distrito de Taraco, provincia de Huancané, Región de Puno (Perú). La técnica DRX en polvo identificó la fase goetita como el principal componente mineralógico, además de cuarzo. La muestra se sometió a un tratamiento térmico <i>in-situ</i> en un intervalo de temperaturas de 100 a 500 °C en atmósfera de aire e inerte (nitrógeno) y se estudió por DRX. Los resultados han mostrado que la fase goetita permanece estable desde la temperatura ambiente hasta 200 °C. A partir de los 250 °C se produce una transformación de fase α-FeO(OH) → α-Fe<sub>2</sub>O<sub>3</sub> con un cambio cromático, es decir, el paso de la fase hidroxilada goetita (amarillo) a la fase oxidada hematites (rojo) con una pérdida de peso de un 8 %, teniendo como evidencia la evolución de los perfiles de difracción y los resultados de ATG. Los espectros μ-Raman del tratamiento térmico <i>in-situ</i> corroboran que se produce también una transición de fase a la temperatura de 290 °C a través de la transformación de las bandas Raman características de la fase goetita hacia la fase hematites en el rango de frecuencias de 200 a 1800cm<sup>-1</sup>.