Hasil untuk "Clay industries. Ceramics. Glass"

Giulia Tameni, Diana Lago, Hana Kaňková et al.

This paper focuses on the activation of boro-alumino-silicate glass from discarded pharmaceutical containers as fine powders suspended in relatively diluted alkaline solutions (2.5 M NaOH/KOH), followed by drying at 40 °C for 7 days. A specific molecular mechanism of glass hardening is proposed. Unlike geopolymers, the hardening does not result from the condensation of products of extensive dissolution. Instead, condensation reactions occur in hydrated surface layers, leading to strong bonds (Si-O-Si, Al-O-Si, etc.) between individual glass particles. Silicates, borates, and aluminates from glass dissolution combine with alkaline ions, yielding additional soluble phases. This mechanism is supported by the results of solid-state NMR spectroscopy and elemental analysis using ICP-OES. Stable matrices prepared by direct foaming or by the inclusion of cenospheres or commercial expanded glass (Poraver®) can be exploited for the fabrication of lightweight components

Karthikeyan Ramachandran, Aayushi Soni, Doni Daniel Jayaseelan

Abstract This study utilizes finite element analysis (FEA) to explore the effect of standardized notch shapes—triangular, circular, and rectangular on the tensile behavior of oxide–oxide (O–O) ceramic matrix composites (CMCs) across various temperature ranges. Findings reveal that unnotched samples exhibited a superior equivalent stress of ∼425 MPa, closely aligning with experimental values. However, under elevated temperatures of 1000°C and 1200°C, degradation occurs, reaching up to 54% decrease at 1200°C. Notched samples demonstrate similar behavior, with all notches acting as stress concentrators. Analysis of single and double notches highlights that circular notches have the most significant stress concentrators due to their smooth surfaces and lack of sharp edges, in contrast to rectangular and triangular notches. Although all notch types influence stress concentration, the absence of non‐sharp corners in circular notches limit stress dissipation, resulting in higher stress concentrations. This trend persists under high temperature as well. The study emphasizes the critical need for a thorough assessment of notch effects, considering their position, orientation, shape, and size, as they significantly affect the mechanical properties of O–O CMCs.

Qingyi Kong, Rao Zhang, Lei Chen et al.

Phase decomposition can effectively enhance the mechanical properties of carbide ceramics and can overcome the difficulty of enhancing the mechanical properties of single-phase multicomponent carbide ceramics. In this work, a series of nonstoichiometric (TiZrVNb)Cx ceramics were prepared by spark plasma sintering (SPS) at different temperatures. The effects of the carbon content on the phase composition, microstructure evolution, and mechanical properties were investigated in detail. Phase decomposition occurred with decreasing carbon content. Two different solid solutions of (Ti,V)-rich and Zr-rich phases formed from the decomposition of equimolar single-phase solid solutions, namely, the Zr-poor phase and Zr-rich phase, respectively. The distribution of Nb element is relatively uniform. The semicoherent interfaces between the Zr-poor phase and the Zr-rich phase can harden and strengthen effectively under the synergistic effect of grain refinement. Ceramics with phase decomposition structures have apparent advantages compared to single-phase high-entropy carbides. This work provides an important train of thought for the microstructure tailoring and properties optimization of multi-component carbide ceramics.

O. Vasiliev, D. Vedel, V. Muratov et al.

We explored the Zr₁₋ₓHfₓB₂ system with first-principles cluster expansion and thermodynamic analysis of possible reactions targeting the synthesis in vacuum-thermal conditions. The results suggest that the system may have a slight tendency to ordering but at high temperatures the formation of solid solutions is driven by the entropy of mixing. We realized the synthesis of an equimolar composition (x = 0.5) by sintering of ZrB2 and HfB2 and reduction from oxides by boron with varying homogenization of the reacting mixtures. The temperature of the complete transformation strongly depended on the reactants homogeneity and was 1900 °C for more coarse raw materials and below 1700 °C for a fine hydrothermal mixture of oxides. The possibility of producing non-equimolar compositions of the solid solutions by the same method was also experimentally demonstrated.

M. García-Galán, F.J. Martínez-Vázquez, N. Rebollo-Muñoz et al.

A novel method for obtaining ceramic (tricalcium phosphate, TCP) fibres with a small diameter (below 0.1 mm) is proposed and its potential use in the 3D printing of scaffolds for biomedical applications is explored. An ink consisting of a high solid content (40 vol%) ceramic slurry in a photocurable resin was prepared and extruded using near-field electrospinning. The influence of the electric potential, flow rate, and distance between tip and collector on the fabrication process in static mode were studied and the role played by unidirectional motion of the collector was also analyzed. A one order of magnitude reduction in the diameter of the jet to around 30 μm is demonstrated under static conditions, which increased to around 100 μm when collector was displaced. Continuous fibres were deposited but the slurry spread over the collector. The method was implemented on a DIW system, using in-flight UV light curing to prevent the spreading of the ink upon deposition. The feasibility of the strategy was demonstrated, although challenges remain for the optimization and control of the fabrication process. Nevertheless, these preliminary results suggest this could be a promising alternative to produce 3D ceramic scaffolds for biomedical applications with improved spatial resolution. Resumen: Se propone un nuevo método para la obtención de fibras cerámicas (fosfato tricálcico, TCP) de pequeño diámetro (menos de 0.1 mm) y se explora su potencial uso en la impresión 3D de andamiajes para aplicaciones biomédicas. Suspensiones cerámicas de alto contenido sólido (40 vol%) en una resina fotocurable fueron extruidas mediante electrohilado de campo cercano, analizando la influencia del potencial eléctrico, el caudal y la distancia entre la punta y el colector y el movimiento de este en el diámetro de la fibra. Se demuestra una reducción de un orden de magnitud en el diámetro del chorro hasta ∼30 μm en estático y hasta ∼100 μm con el colector en movimiento. Se depositaron fibras continuas, pero se observó esparcimiento de la suspensión sobre el colector. El método se implementó en un sistema de moldeo robotizado, utilizando curado en vuelo por luz ultravioleta para evitar el esparcimiento de la tinta tras la deposición. Aunque la viabilidad de la estrategia queda demostrada, siguen existiendo retos para la optimización y control del proceso de fabricación. No obstante, estos resultados preliminares indican que esta técnica podría ser una alternativa prometedora para producir andamios cerámicos 3D para aplicaciones biomédicas con una resolución espacial mejorada.

Claudia Heuer, Steffen Dudczig, Christos G. Aneziris et al.

In the recent years, the demand for clean steel in critical applications e.g. in construction or transportation industry has increased. In view of the research and developments in the steel production and refinement it seems logical to pursue new approaches on the refractories and to evaluate the existing ones. Within this study zirconia castables stabilized by yttria or magnesia with additions of an alumina or an alumina-magnesia based binder were developed. The influence stabilizer and binder type on the phase evolution of the zirconia castables was investigated. The physical, mechanical and thermomechanical properties were evaluated. Subsequently, the zirconia castables were tested in a steel casting simulator under industry-oriented conditions. Alterations in surface chemistry and morphology were studied via optical light and scanning electron microscopy. Using an automated feature analysis, the solidified steel was investigated regarding the formation of non-metallic inclusions during steel casting experiments to identify their type and frequency.

Pengfei Zhang, Guangchao Yang, Lingfeng Zhang et al.

The short carbon fiber (Csf) reinforced SiC-BN-10%X (X = ZrC, ZrO2 or ZrB2) composites were prepared by hot pressing at 1900 °C and 40 MPa for 1 h. The phase composition and fracture morphology of the prepared composites were investigated, and the interfacial reactions between carbon fiber and ceramic matrix were discussed. The results show that ZrC, ZrB2 and ZrO2 all react with the Csf/SiC-BN system to form a lot of ZrB2 and ZrC, and the carbon fibers in all composites are corroded and damaged. The carbon atoms from ZrC and carbon fiber react with oxide film (ZrO2, B2O3, SiO2) or transition products (ZrSiO4, B4C) to form ZrC, ZrB2, SiC and CO. The interplanar spacing of the ZrC grains in the prepared composites decreases due to the consumption and shortage of carbon atoms. In the Csf/SiC-BN-10%ZrO2 composite, ZrO2 is completely reacted and almost all carbon fibers are exhausted.

Luiza Felippi de Lima, J.E. Zorzi, R.C.D. Cruz

Basalts, which cover about 70% of the Earth's surface, are igneous rocks originating from cooling and solidifying the magma on the Earth's surface. Products obtained from the melting of rocks have a wide market and can be considered the precursors of glass-ceramic technology. These materials are promising due to the possibility of converting low-cost natural raw materials into products with excellent mechanical, thermal, and chemical properties. In this article, a general overview of the basic principles for obtaining basaltic glass-ceramic materials will be made, as well as their properties, applications, and potentialities. Resumen: Los basaltos, que cubren aproximadamente el 70% de la superficie de la Tierra, son rocas ígneas que se originan al enfriar y solidificar el magma en la superficie terrestre. Los productos obtenidos de la fusión de rocas tienen un amplio mercado y pueden considerarse los precursores de la tecnología de vitrocerámica. Estos materiales son prometedores debido a la posibilidad de convertir materias primas naturales de bajo costo en productos con excelentes propiedades mecánicas, térmicas y químicas. En este artículo se realiza una descripción general de los principios básicos para obtener materiales basálticos de vitrocerámica, así como sus propiedades, aplicaciones y potencialidades.

Kazuz Abdul, Radovanović Željko, Veljović Đorđe et al.

α-Tricalcium phosphate/fluorapatite (α-TCP/FAp) mixed powders were prepared in order to obtain dental root canal filling cements. Different liquids for cement pastes have been investigated and the most suitable one for obtaining rheologically optimal pastes was chosen for further analysis. Morphological changes in the cement materials as a consequence of the formation of hydroxyapatite (HAp) after the immersion in a simulated body fluid (SBF), an influence on the cell viability, and final success of the filling were investigated by field emission scanning electron microscopy. Treatment of the α-TCP/FAp mixtures in SBF at 37°C resulted in a complete transformation of α-TCP into HAp after 10 days, while the exposure of MRC-5 human and L929 animal fibroblast cells to the cement showed complete absence of cytotoxicity. The root canal of an extracted tooth was filled with the α-TCP/FAp cement containing 5 wt.% of FAp and relatively strong adhesion between the cement and dentine was observed after 48h. The same cement material was immersed during 10 days in SBF and after that both human and animal fibroblast cells during in vitro MTT tests showed higher cell viability compared to the control sample. These findings lead to a conclusion that the α-TCP/FAp based cement demonstrates potential for further development towards dental cement application.

Norikazu Ishigaki, Junji Akimoto

We successfully prepared single-phase sample of the low-temperature β-type form of lithium phosphate Li3PO4 by a stoichiometric mixing of LiOH solution and NH4H2PO4 powder at room temperature without heating. The orthorhombic lattice parameters with the space group of Pmn21 for β-Li3PO4 were refined to be a = 6.1281(6) Å, b = 5.2674(5) Å, c = 4.8923(2) Å, and V = 157.92(2) Å3. We also prepared the single-phase sample of high-temperature γ-Li3PO4 by heating the β-Li3PO4 at 650°C. The orthorhombic lattice parameters with the space group of Pmnb for γ-Li3PO4 were refined to be a = 6.12569(5) Å, b = 10.48730(9) Å, c = 4.92957(4) Å, and V = 316.685(4) Å3. The structure transformation from β- to γ-type phase was examined utilizing the XRD measurements. The XRD data confirmed the continuous phase change in the temperature range between 25°C and 650°C. The lattice contraction for the β-Li3PO4 phase was observed between 150°C and 350°C. The phase transformation from β- to γ-Li3PO4 was observed around 450°C. The spherical primary particle size was ca. 20–30 nm order for both β- and γ-Li3PO4 samples. Accordingly, the nano-sized particle Li3PO4 sample can be easily prepared using the present synthetic technique at room temperature.

Priyadharshini Perumal, Ali Hasnain, Tero Luukkonen et al.

Porous ceramics were generated by direct foaming the alkali-activated unprocessed kaolin (impure kaolin, iK) with the addition of hydrogen peroxide (H2O2) and calcining at a low temperature of 400 ​°C. Hydrogen peroxide, a blowing agent, decomposes producing oxygen gas bubbles forming the porous structure in the fresh alkali-activated iK paste. In the present study, three different molarity of alkali activator (5, 10, or 15 ​M NaOH) were employed. The dosage of blowing agent (H2O2) was varied between 0 and 2% with a constant dosage of 0.5% (wt. of binder) of surfactant. The gas bubbles in fresh-state geopolymer slurry are unstable with a tendency to coalesce. In such cases, surfactants are introduced to improve the stability of the gas-liquid interface. Two different surfactants: non-ionic and cationic ones were used to study the properties of alkali-activated porous material. Fresh properties such as viscosity, yield stress, foaming rate, and fresh density were compared between reference iK samples without surfactants and those with surfactants. The mechanical and microstructural properties of alkali-activated (AA) low-temperature porous iK ceramics were determined after calcination. Pore structures were characterized with electron microscope to understand the interaction of different parameters during fresh/hardened state and their relevance with the changes in the mechanical properties. Surfactants, irrespective of the type, highly influenced the fresh properties of the AA-iK samples, which in turn reflected on the compressive strength of the porous ceramics.

Anil Maini, Mohammad Ashraf Shah

Abstract This study has reported about the preparation and characterization of Copper oxide (CuO) nanoparticles doped with Cobalt series at low temperature by Sol‐gel method. The characterization techniques like X‐ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy, defused reflectance spectroscopy (DRS), and DC measurement have been used to confirm its phase formation, that is, monoclinic, surface porous morphology, the redshift of Raman peaks confirms optical phonon confinement, whereas increasing bandgap signifies the quantum confinement effect. The semiconducting nature of samples has been observed by two probe method. Furthermore, the study has focused in detail on the effect of cobalt doping with varying concentrations by wt % on its structural, morphological, optical, and conductivity features.

Kyriaki Corinna Datsiou, Dominic Hall, Mauro Overend

Glass strength is very sensitive to damage accumulation during its service life. Repair methods for glass have been proposed over the last decades to volumetrically fill or remove existing flaws from the surface of glass. However, the lack of information on the strength recovery attributable to glass repair methods restrict their use to low consequence class applications in buildings thereby making replacement of damaged installed glass the only safe and practical solution when dealing with damaged glass. Repair methods involving volumetric filling of visible flaws with resins, removal of visible flaws with polishing and chemical repair with acid treatment of visible flaws are undertaken in this study to investigate the strength recovery in 60 artificially aged annealed glass specimens. It is found that the polishing provides the most promising strength recovery results showing a 132 and a 40% increase in design and mean strength whilst the acid treatment provides the worst performance. Polishing repairs are further investigated in this study to determine their efficacy in strength recovery after environmental ageing (exposure to UV, humidity and freeze-thaw cycles).

Miodrag M. Milutinov, Maria Vesna Nikolić, Snežana G. Luković et al.

In this paper, the influence of additional sieving and milling of starting industrial Mn-Zn powders on magnetic properties was investigated. The starting powder was milled for 60 minutes, followed by sieving through 325 and 400 meshes. The starting and milled powders were used to fabricate toroid shaped samples sintered at 1200°C for 2 hours. Structural parameters of the fabricated samples were analysed by X-ray diffraction and scanning electron microscopy. Complex permeability, core loss density, and hysteresis were measured using the modified watt-meter method. The complex permeability and hysteresis loop were modelled with a new model proposed in the paper. The core loss density was modelled with the Steinmetz empirical equation. The experimental results and calculations show the significance of the additional milling and sieving process on magnetic properties of Mn-Zn ferrite in the frequency range 0.1-10MHz. These processes increase the relative permeability about 3 times and decrease the core loss 4 times by milling of the starting powder.

Criado, Emilio

Gyanendra P. Tiwari, Ashok K. Suri, Nagaiyar Krishnamurthy et al.

The volume expansion of tantalum due to the dissolved hydrogen has been determined using Bragg equation. The hydrogen was dissolved in the pure tantalum metal at constant temperature (360 °C) and constant pressure (132 mbar) by varying the duration of hydrogen charging. The amount of dissolved hydrogen was within the solid solubility limit. The samples with different hydrogen concentration were analyzed by X-ray diffraction technique. Slight peak shifts as well as peak broadening were observed. The relative changes of lattice parameters plotted against the hydrogen concentration revealed that the lattice parameters varied linearly with the hydrogen concentration.

Fernández Canteli, A., García Prieto, M. A., Lamela Rey, M. J. et al.

This paper reports on a probabilistic model for design of glass plates and the procedure to determine the allowable load of specified types of glass, as a proposal for a new Spanish code for structural glass. After the experimental material characterization, the design model, implemented in the Windesign software, allows the user to calculate either the probability of failure of a monolithic glass plate for a given dimensions and specific loading, or to determine the plate thickness needed to withstand a known loading for a given probability of failure. Moreover, a comparative analysis among the results obtained by the model proposed here and the current foreign glass design standards, such as the American ASTM E 1300-02, the Italian UNI 7143-72, the French NFP 78-201-1 and the New Zealander NZS 4223 is presented.<br><br>El presente artículo describe un modelo probabilístico de cálculo de placas de vidrio y el procedimiento que permite la determinación de la carga admisible en determinados tipos de vidrio, como propuesta de una nueva norma española de vidrio estructural. Una vez caracterizado el material, el modelo, implementado en el programa Windesign, permite el cálculo de la probabilidad de fallo para una placa de vidrio monolítico de dimensiones dadas sometida a una determinada carga, o en su caso, la determinación del espesor de placa capaz de resistir una carga conocida para una probabilidad de fallo dada. Asimismo se presenta un estudio comparativo entre los resultados obtenidos para el modelo aquí propuesto y varias normas extranjeras de vidrio, tales como la norma americana ASTM E 1300-02, la italiana UNI 7143-72, la francesa NFP 78-201-1 y la neozelandesa NZS 4223. Palabras clave: Vidrio estructural; Modelo probabilística; Mecánica de fractura; Norma de cálculo.

de Aza, A. H., Turrillas, X., Rodríguez, J. L. et al.

Due to their adequate time-resolution, high temperature Powder Neutron Diffraction applied to reaction-sintering process allows in situ reaction analyses and transient phase identifications, which otherwise cannot be detected by quenching and conventional diffraction methods. Bearing in mind that dolomite MgCa(CO3)2 is often used as a raw material in the synthesis of different refractory materials, in the present work, neutron diffraction time-resolved experiments were carried out during MgCa(CO3)2 decomposition and the first steps of the reaction-sintering process of MgCa(CO3)2-Al2O3 and MgCa(CO3)2-ZrSiO4 mixtures. The results obtained up to 1300ºC are presented and discussed to understand how these minerals behave during these first steps of the reaction sintering process. The activation energy for dolomite and calcite breakup was calculated from fitting to a contracting sphere model. Additionally, the dolomite mean thermal expansion coefficients were calculated along a and c axes from 25º to 700º C.<br><br>La utilización de la difracción de neutrones a alta temperatura, aplicada a la investigación de procesos de sinterización reactiva, permite el estudio de las reacciones que tienen lugar in situ y, debido a su excelente poder de resolución temporal, la identificación de posibles fases transitorias de corta vida. Este trabajo recoge algunos de los resultados obtenidos durante la descomposición de la dolomita MgCa(CO3)2 y los primeros estadios (hasta 1300º C) de la sinterización reactiva de mezclas de dolomita con alúmina (Al2O3) y dolomita con circón (ZrSiO4). Teniendo en cuenta estos datos se han establecido las secuencias de reacción, así como la formación de distintas fases transitorias en cada uno de los sistemas. Así mismo, se han determinado las energías de activación correspondientes a la descomposición del MgCa(CO3)2 y del CaCO3 en compactos de MgCa (CO3)2 puro y en las mezclas estudiadas. Adicionalmente, mediante refinamiento Rietveld se ha determinado la variación con la temperatura de los parámetros cristalinos a y c de la celda unidad del MgCa(CO3)2 hasta temperaturas próximas a su descomposición (700º C).

Oliva, A. I., Pech-Canul, M. A., Ceh, O. et al.

In this work a simple method for monitoring the low temperature oxidation of aluminum thin films, which is based on measurements of electrical resistance using the four-probe technique, is proposed. Kinetic growth data of the aluminum oxide layer, obtained using different values of applied current on as-deposited metallic films is presented. The temperature gradient measured on the films were 2 °C and 9 °C when the corresponding applied currents were 0.1A and 0.2 A. The obtained data show a good agreement with the Cabrera-Mott`s model for low temperature oxidation of metals. From kinetic curves, values of the energy barrier (U) and of the electrostatic potential (V) were obtained, which are reasonable with the values reported in the literature. The sample with a larger current applied, exhibited a higher oxidation rate due to a thermal effect and by the larger electrostatic potential established across the oxide layer. This simple method can be interesting to monitoring and controlling the oxidation process.<br><br>En este trabajo se propone un método sencillo para el seguimiento del proceso de oxidación de capas delgadas de aluminio, basado en mediciones de la resistencia eléctrica usando la técnica de cuatro puntas en línea. Se presentan datos de cinética de crecimiento de la capa de óxido de aluminio para dos muestras recién depositadas a las que se aplicaron valores distintos de corriente. Los cambios de temperatura medidos fueron de 2 °C y 9 °C para corrientes aplicadas de 0.1 A y 0.2 A. Los datos muestran buen acuerdo con el modelo de Cabrera-Mott para oxidación de metales en baja temperatura. A partir de las curvas de crecimiento se obtuvieron valores de la barrera de energía (U) y del potencial electrostático (V), razonables con los reportados en la literatura. La muestra con mayor corriente aplicada se oxidó más rápido debido al efecto térmico ya que se estableció un mayor potencial electrostático a través de la capa de óxido. Este sencillo método de análisis puede ser de gran interés para el control del proceso de oxidación en metales.

Celi, L. A., Caballero, A. C., Villegas, M. et al.

Lead zirconate titanate ceramic powders have been surface modified by using phosphor esther 0.3% in volume. The phosphorous modification gave higher densities at lower temperatures associated with a reduction of the weight losses during the densification process. From the relationships between ceramic processing and microstructure, it was established that the phosphorous surface modification allows the effective grain growth control as well a higher homogeneity in the grain size distribution.&lt;br&gt;&lt;br&gt;Se ha realizado un proceso de modificación superficial con ester fosfato al 0.3% en volumen, sobre polvo cerámico de titanato circonato de plomo, PZT. Se observa que el material modificado con fósforo presenta una mayor densificación aparente a una temperatura menor unida a una reducción de las pérdidas de peso durante el proceso de densificación. Se han establecido las relaciones entre el procesamiento y las microestructuras del material PZT sin modificar y el modificado. Se evidencia un control del crecimiento de grano y una mayor homogeneidad en la distribución de tamaños de grano en el material modificado.