Open Ceramics最新文献

In recent years, ceramic 3D printing has proven its potential for increasing the cost and time efficiency of ceramic manufacturing, especially for customizable products, small series production and for (multi-material) parts with complex design. This work gives an overview of the methods for ceramic additive manufacturing that are currently available for industrial production with their advantages and disadvantages. Ceramic Powder Bed Fusion- Laser Beam (PBF-LB) or also known as selective laser sintering or melting (SLS/SLM) is introduced, using a ceramic powder as starting material for shaping by selective laser irradiation. Amongst others, the technique offers a superior productivity, which might be the central argument in the future for evaluating the applicability of PBF-LB for industrial manufacturing. Additionally, a novel approach to ceramic PBF-LB is presented, using a thermoset binder for incorporating ceramic particles in the starting material that, due to the non-meltable nature of the binder, improve the dimension stability of the green parts during thermal debinding and sintering. The production of large, complex structures opens up a wide range of applications. One promising application for porous structures made of photocatalytic titanium oxide is water treatment. Such printed, debinded and sintered filter modules enable the degradation of organic residues in water, thus contributing to safer and higher water quality. Furthermore, high-resolution printing can be realized via micro-PBF-LB (μ-PBF-LB, also known as μ-SLS).

Vat photopolymerization additive manufacturing technology allows the shaping of ceramic structures with limitless opportunities in terms of design freedom, structural resolution, and improving processing speed while reducing cost and wastage. The quality of a final product is influenced by the raw materials and processing routes. The particle size distribution of ceramic powders significantly affects ceramic slurry's rheology and cure behaviour as well as the densification process during sintering. This work studies the rheological properties of slurries prepared from 8 mol.% yttria-stabilized zirconia powders with various particle size distributions and densification of green bodies prepared from these suspensions. The suspension with a narrow particle size distribution showed a non-Newtonian behavior with a viscosity of >1 Pa s at a solid loading above 29 vol%, and a significant densification at a sintering temperature of 1400 °C. The viscosity of a suspension prepared from a powder with a wide particle size distribution was <1 Pa s in a solid loading range of 29–37 vol%. The higher cure depth at a lower exposure energy for slurry with coarse particles allowed a reduction of the printing time, while suspension with fine particles can be used for high-resolution printing with longer exposure time.

The adsorption efficiency of surface-functionalized Philippine natural zeolite (PNZ) for heavy metal uptake from single and mixed metal ion-simulated wastewater solution is reported in this work. Atomic adsorption spectroscopy (AAS) findings revealed that NaCl-modified PNZ (MPNZ) exhibited the highest zinc ion adsorption of 99.96 % while PNZ yielded an adsorption of 95.61 %. The adsorption isotherms of raw PNZ and MPNZ both show similar shapes that reflect Type IV adsorption-desorption isotherms with Type H2 hysteresis loop which can be observed for micro-mesoporous materials (pore containing 2–50 nm). An increase in PNZ pore size from 10.11 nm to 13.36 nm for NaCl-PNZ and 15.59 for NaOH-PNZ is observed after alkaline treatment. EDS confirmed the decrease in Si/Al ratio from 4.02 to 3.76, indicative of possible higher negative charge in the PNZ framework which is favorable for an enhanced Coulombic or electrostatic interaction with the cationic heavy metals being detected in this study. MPNZ demonstrated an adsorption capacity of 99.96 % for copper in mixed-ion solution while 88.49 % and 86.67 % were obtained for zinc and nickel, respectively. These values are higher compared to PNZ having only 32.21 % uptake for zinc and 38.00 % for nickel. A hierarchy of the average metal adsorption capacity showed the order: copper > nickel > zinc. Rapid adsorption at the first hour of the adsorption reaction was attained in all solutions while samples with pH 9 exhibited the highest Ni²⁺ and Zn²⁺ percent removal. Moreover, the increase in initial solution concentration led to lower adsorption efficiency and the maximum uptake was attained at 100 ppm. The equilibrium data of adsorption and mechanism were suitably described by Langmuir isotherm model. With these, surface functionalization of PNZ has further enhanced its cationic adsorption capacity on heavy metals in both single and mixed-ion solution having promising potential for wastewater remediation.

The present work addresses powder bed binder jetting additive manufacturing by selective magnesium phosphate cement activation. Despite the potential of this technology to aid the digitalization of the construction industry, the effect of processing parameters on the mechanical performance of printed materials has not yet been studied to generate a guideline for the further development of the technology. Statistical methodologies were used to screen the effect of four printing process parameters (printing speed, layer thickness, raster angle, and build direction on flexural and compressive strength). As the exploited technology works with constant fluid pressure, the physical interpretation of the effect of each factor can be considered taking into account the interactions between the binder materials in the powder bed. Analysis of variance (ANOVA) indicated that printing speed and layer thickness significantly affect mechanical performances. Furthermore, the layout of samples for the printing process is preferable to be parallel the printhead movement. An anisotropic behavior was observed, and the samples subjected to compressive forces parallel to the layer plane possessed lower strength values. This effect can be interpreted as a result of a weak area of low density in between layers, leading to a pronounced delamination under compression.

Even though the strength of the printed material is not suitable for a structural concrete, it can be marginally improved by design of experiment and optimized for non-structural applications, such as for porous artificial stone. Design of experiment coupled with ANOVA methods can be used in the future to support the development of novel material mixtures, thus expanding the fields of application of this novel additive manufacturing technology.

In this study, nanoparticles of perovskiteCaZrO₃ were prepared by a solution combustion technique using urea, glycine, β-alanineand citric acid as fuels. The aim of this work is to estimate the effect of these different fuels on the structure and microstructure of CaZrO₃ powders. The flame reaction was estimated by means of a thermocouple which allowed us to show that the combustion reaction velocity. The thermal decomposition of nitrate precursors was studied with the help of TG-DTA coupled with the infrared spectroscopy. The FT-IR spectroscopy enabled to check the identity of the evolved gases over the mass loss process. CaZrO₃ powders were calcined at 900 °C for 1 h. The powders were thoroughly characterized by scanning electron microscopy, X-ray diffraction andThermodilatometry. Also, the combustion process using glycine as fuel is beneficial to produce CaZrO₃ powders at low temperature, which are known to have a good reactivity with fine particles.

The present study focuses on tailoring the relative content of Fe³⁺ and Fe²⁺ ions incorporation into hydroxyapatite (HA) lattice, employing a hydrothermal approach in a closed vessel to minimize Fe²⁺ oxidation and secondary phase formation. Citrate molecules are used to regulate nanoparticle formation/stability, creating a mild reducing environment, while the impact of a stronger reducing agent, hydroxylamine, is explored. Fe³⁺ insertion was found to be less favoured than Fe²⁺, possibly due to charge imbalance. Iron doping significantly alters stoichiometry and crystallinity of HA, with Fe³⁺ enhancing OH⁻ depletion. Morphological analysis reveals differences among samples, as induced by the different Fe ions incorporation: particularly Fe²⁺ ion incorporation is found to maintain rod-like structures, which changes upon Fe³⁺ presence. Overall, this study provides insights into controlled doping of HA with iron ions, vital for developing stable, redox-responsive nanomaterials applicable in cancer therapy and other applications where surface activity plays a relevant role.

Plenty of traditional and novel sintering techniques have been utilized to enhance the performance of perovskite materials. Among several sintering methods, electric field-assisted spark plasma sintering (SPS) is a modern category and has been effective for the excellent functionalities of perovskite compounds. The state-of-the-art SPS systems, perovskite materials development, and corresponding design are focused. This article will highlight the parameters of this technique, the advanced procedure of sintering, and their respective effects on the densification and dielectric performance of ABO₃ perovskite materials. No such work has been reported to relate the crystalline nature of the various functional perovskites with the spark plasma sintering procedures. This review illustrates a good compilation of recently reported few perovskite materials processed by spark plasma sintering and relationships between thermal effects, density, and dielectric performance. The enhanced density, high dielectric permittivity, and low dielectric loss were achieved due to SPS.

A double layer coating was designed and fabricated on glass surfaces by sol-gel method using a silica-titania (SiO₂–TiO₂) thin film as the bottom layer and an inorganic-organic (triethoxy(octyl)silane (OTES) modified SiO₂) upper layer. SiO₂ and TiO₂ sols were prepared using tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TIP) as precursors and nitric acid (HNO₃) as catalyst. The refractive index of the SiO₂–TiO₂ and OTES modified SiO₂ layers were 1.79 and 1.45, and their thicknesses were approximately 76.8 nm and 94.2 nm, respectively. The results show an increase of 7% in transmittance respect to the uncoated glass substrate. At the same time, OTES-modified SiO₂ top layer significantly improved the hydrophobicity of the system; the water contact angle of film increased from 56° for system without the OTES modified SiO₂ layer to 102° for the system with OTES-modified SiO₂ top layer.

The addition of Sn into the raw materials is currently one of the most widely used methods to improve the purity and mechanical properties of Ti₃AlC₂. It follows in this work to investigate the oxidation behavior of the resulting Ti₃Al_0.8Sn_0.2C₂ at 1200 °C with the oxidation time up to 500 h. The oxidation kinetics shows that its oxidation resistance is much worse than that of common MAX phases including Ti₃AlC₂, Ti₂AlC, and Cr₂AlC. The oxide layer mainly consists of TiO₂ and Al₂O₃, with only a small amount of SnO₂ at the beginning of the oxidation stage. Cracks induced by the internal thermal stress penetrate through the entire oxide layer after only 1 h, which is an important reason for the rapid oxidation of the internal substrate layer. This work is expected to provide some inspiration and reference for Ti₃Al_0.8Sn_0.2C₂ used as the potential high-temperature structural material.

The use of plastic waste as a resource in construction applications is an opportunity for environmental protection, conservation of natural resources and reduction of pollution. Unfortunately, they don't always withstand the stresses to which they are subjected, leading to subsidence and collapsing. An analysis of the causes using the Pareto curve shows that 74.47 % of the causes of this collapse are due to poorly formulated mixes and poor choice of raw materials for the composite. The compressive test carried out on the first sample of pavers studied showed a maximum compressive strength value of 4.6 MPa, which is below the standard requirements. As a result, the pavers were considered unsuitable for use on a T5 road. Through the use of the SUPERDECISION software, we were able to identify two favourable constituent materials - glass/glass waste and gravel - for the production of composite paving stones. By adding low-density plastic waste, collected, cleaned and crushed in the form of aggregates, we obtain a compressive strength of 7 MPa with gravel and 8 MPa with glass waste. These values are below the recommendations of the NF EN 1339 standard (Rc ≥ 20 MPa) for T5 traffic. The best composition for ecological paving is therefore (PET/PP/PEBD) + sand + glass (50/12.5/37.5). Analyzing these results shows that the raw materials used for ecological paving should be adapted to the loads.