International Journal of Applied Ceramic Technology最新文献

The present study intends to establish biphasic composite scaffolds containing polycaprolactone/hydroxyapatite (PCL/HA) and PCL/barium titanate (PCL/BT) layers with improved mechanical and biological properties by preserving HA and tuning BT contents. The porous piezo-biphasic scaffolds were fabricated, using extrusion three-dimensional printer technology, and on the basis of the scanning electron microscopy results, a relative porosity of 210–250 µm was created. The presence of BT phase in the biphasic scaffolds was confirmed by X-ray diffraction and Fourier transform infrared analyses. The printed biphasic composites demonstrate suitable mechanical strength compared to one containing only 35% PCL and 65% HA compositions, which had a strength of 2.5 MPa. However, the strength for 80% BT-incorporated biphasic composite was almost 13.5 times higher than that of monolithic specimen. The measured output voltages for the scaffolds after being subjected to an electric field affirmed that adding BT nanoparticles in biphasic composites leads to an increase in the output voltage that was lower compared to the monolithic scaffold. The piezo-biphasic scaffold containing 80% BT is found to possess the highest enhancement in cytocompatibility for MG63 cells with the survival rate of approximately 95%, rendering the PCL/HA–PCL/BT biphasic scaffolds promising candidates for bone regeneration.

In this study, we investigated the impact of polyethylene glycol, sodium carboxymethyl cellulose, and polyvinyl alcohol on the rheological behavior, printability, and mechanical/physical properties of 3D-printed scaffolds for high-temperature applications using SiC/clay ceramic paste. Employing the Direct Ink Writing method, varying concentrations of each polymer (PEG: 2.5%–10% weight, CMC: .6%–1.8% weight, PVA: .25%–1% weight) were incorporated into the composition. The resulting SiC/clay paste, with adjusted additive content, was used to 3D-print scaffold structures through Direct Ink Writing. Sintering of clay-bonded SiC samples were carried out at 1300°C for 1 h in an ambient atmosphere. The research revealed that altering the additive amounts significantly influenced the rheological behavior, mechanical properties, and physical characteristics of the printed specimens. Notably, the ideal properties with additive concentrations (10% wt PEG, 1% wt PVA, and .6% CMC) were identified, providing the best outcomes in terms of printability and firing results. High density samples with 2.09, 1.93, and 1.79 g/cm³, high compression strength of 20.82, 14.5 and 12.53 MPa with 32.26%, 42.5%, and 52.63% open porosity for samples containing PVA, CMC, and PEG modifiers were obtained, respectively. Additionally, the study led to the development of a high solid loading printable paste with an 80% weight.

The corrosion of SiC_f/SiC composites in gas environment threatens their long-term service in aeroengines as hot-end structure components. Addition of corrosion-resistant phases into SiC matrix is a potential strategy to improve the service performance of SiC_f/SiC materials. Here, AlN added SiC ceramics were prepared by reactive melt infiltration, and the effect of AlN phase on the oxidation resistance of the ceramics was emphasized. The oxidation tests were performed in dry oxygen and water oxygen atmospheres at 1100°C–1300°C, respectively. The oxidation mechanism was discussed based on the microstructure evolution of the oxide layer. The results show that the oxide layer is composed of aluminum silicate glass and Al₂O₃ flakes dispersedly distributed in the glass phase. As the temperature rises, the oxide layer gradually grows and thickens. Finally, a smooth and dense protective layer could be formed on the surface of ceramics to resist oxidation. This study can provide a profound insight to construct SiC_f/SiC composites with excellent oxidation resistance.

To solve the problem that Si was volatile and dense Si/SiC ceramics were difficult to achieve by spark plasma sintering (SPS) under a low sintering temperature and pressure, three kinds of SiC powders were used for particle grading and then ball-milled with different time to further change and regulate their particle size and morphology, and finally nearly dense Si/SiC ceramics were prepared by SPS. The effect of milling time on particle size, morphology, tap density, phase, and microstructure of the SiC powders, as well as on bulk density, microhardness, thermal conductivity, phase, and microstructure of the Si/SiC ceramic, was researched. When the mixed SiC powders were ball-milled for 12 min, the bulk density, microhardness, and thermal conductivity of Si/SiC ceramic were 2.96 g/cm³, 22.95 GPa, and 152.84 W/(m K), respectively. Ball milling changed the particle gradation and micro-powder morphology and then affected the powder particle stacking state. Forming continuous pore channels was conducive for the volatile liquid Si to flowing and filling pores in a short time, resulting in denser Si/SiC ceramics at a lower sintering temperature and pressure. This study was useful for the preparation of ceramics containing volatile liquid phase by SPS.

The Knoop hardness (HK) and compression strength (σ_c) of 23 advanced ceramics were measured to determine if an overarching HK/σ_c relationship could be identified for ceramics, or if one exists for a specific class of ceramics, similar to the hardness/yield strength relationship (H/Y ≈ 3) identified by Tabor for metals. Compression strength was determined using a dumbbell-shaped specimen that virtually eliminates the end splitting that occurs when cylinders or cuboids are tested and provides a more representative compression strength value. HK values were obtained over a range of indentation loads between 0.98 and 98N. Four HK values, HK₂, load-independent HK, the hardness from the proportional specimen resistance model, and a brittleness parameter, were obtained and plotted against compression strength. An overarching relationship could not be identified for ceramics in general and the only class of ceramics that had a consistent relationship was tungsten carbide/cobalt that had a HK/σ_c of approximately 2.5. The consistent relationship for the WC/Co materials is due to the cobalt plastically deforming during the loading processes, something that does not occur in the other ceramics evaluated.

Fiberboard (FB) is extensively utilized in heat-insulating refractory materials owing to its lightweight nature and excellent resistance to high temperatures. Nevertheless, the inadequate mechanical properties and limited dimensional stability of FB hinder its further application. The vacuum filtration was utilized in this study to manufacture inorganically modified insulation FB, incorporating plus fiber/1260 fiber and silica sol as the primary constituents and sepiolite powder (HS) as the modifier. The experimental results show that the fabricated samples exhibited extremely high porosity (75.3%–90.2%) and low thermal conductivity (.063–.15 W m⁻¹ K⁻¹, 200–800°C). The fibers were arranged in a three-dimensional structure, overlapping with each other, and the silica sol adhered to the fibers, forming a spatial mesh structure through cross-linking. Importantly, the incorporation of HS was effective in controlling the agglomeration of the silica sol, leading to a more uniform distribution within the fibers. Additionally, the study found that the mechanical properties (high hardness (64–72 HA)) and high-temperature durability of the FBs were enhanced due to the flocculant modification. This study highlights promising prospects for industrial applications and offers a cost-effective admixture for modifying and preparing high-performance FBs, which is expected to see broad adoption in thermal insulation and energy conservation applications.

The social progress, economic growth, and meteoric urbanization prompt the exploitation of available resources triggering the contagion of the biological and physical elements of the atmosphere irrationally causing global environmental pollution. Environmental contamination monitoring is a dire necessity. Although a number of technologies find mention in the literature for environmental remediation, however, environmental catalysis is an advanced steadily growing technique for pollution abatement. In this dimension, ceramic materials have turned heads due to their wide-scale application areas. Hitherto, research is being done on advanced ceramics to fabricate novel modules for energy storage applications, in designing green buildings, pollution rheostats, and environmental engineering. This article deals with the abatement of environmental contaminants by adopting various methodologies such as aerobic and anaerobic biological treatments, adsorption, chemical oxidation, membrane separation, photocatalysis, ozonation using the ceramic as precursor materials. The ceramic membranes are cost-effective, ecofriendly, efficacious, and green approach to obliterate toxins and harmful gases released in environment. Even though, limited literature is available on the abolition of harmful contaminants from air and soil using ceramic materials, an attempt has been made to present currently available data with best of our knowledge. This article will sensitize researchers to refabricate novel materials for environment sustainability.

Functionally graded ceramic systems consisted of Al₂O₃/(Al₂O₃–ZrO₂) and Al₂O₃/(Al₂O₃–Nd₂Ti₂O₇) have been produced by gel casting. In Al₂O₃/ZrO₂ systems, Al₂O₃ was gathered with three different Al₂O₃/ZrO₂ mixtures with varying ZrO₂ contents. For Al₂O₃/Nd₂Ti₂O₇ system, Al₂O₃ layer was combined with 3 mol% Nd₂Ti₂O₇-doped Al₂O₃. All samples sintered at 1480 and 1540°C showed strong adhesion between layers without any crack formation. In the Al₂O₃/ZrO₂ systems, both layers were intact; a distinct separation was observed, whereas a large reaction zone was observed for the Al₂O₃/Nd₂Ti₂O₇ system as a consequence of reaction between both phases. The separation between layers for both systems was identified by SEM–EDX analyses. The hardness and wear tests of the samples showed that functional grading approach ensures combining various physical properties in a monolithic body.

At present, graphite is commonly used as the carbon source in Al₂O₃-C refractory. However, graphite resources are limited and belong to the category of nonrenewable resources. Coconut shell is a biomass material with low cost, low impurity, and high reactivity, and also belongs to renewable resources. Therefore, the research for using coconut shell carbon as a substitution for graphite in Al₂O₃-C refractory has great significance. In this work, the coconut shell was firstly carbonized at 200–1000°C in flowing argon, and the microstructure of the carbonized coconut shells was investigated. Then the carbonized coconut shell powder was introduced into Al₂O₃-C refractory instead of graphite, and the effect of carbonized coconut shell on mechanical properties and microstructure evolution of materials was investigated. The results show that the carbonized coconut shell has porous structures, composed of amorphous carbon and disordered micro-graphite with many defects, endowing its high reactivity. Compared with graphite, the carbonized coconut shell promotes the Si and Al to in situ formation of nonoxide ceramic whiskers (SiC, Al₄C₃, and AlN), which play a strengthening and toughening role in the materials. When graphite is replaced by 1 wt% carbonized coconut shell, the residual strength ratio of samples increased from 81.8% to 90.2%, and that of the hot modulus of rupture increased from 17.53 MPa to 18.47 MPa.

ZrB₂–SiC ceramics are the potential candidates for the ultrahigh-temperature thermal protection materials of sharp-bodied reentry and hypersonic vehicles. However, their ultrahigh-temperature mechanical behaviors have been rarely reported. In the present work, an ultrahigh-temperature testing method for the tensile properties of ceramics is proposed. The tensile behaviors of ZrB₂–20 vol% SiC are studied up to 1950°C in air and to 2050°C in nitrogen atmosphere for the first time. The tensile stress–strain curves, Young's modulus, and tensile strength are obtained. The microstructure evolutions, including crystallization of sintering aids, grain recombination, and grain oxidation, are observed, and their effects on the tensile properties are analyzed. The mechanisms controlling the tensile behaviors at ultrahigh temperatures are revealed. The maximum operating temperature of ZrB₂–SiC ceramics has been identified.