Open Ceramics最新文献

In this study, we report the low-cost synthesis of titanium carbide (TiC) from recycled precursors and further used to synthesize MAX phase material, Ti₃AlC₂. The recycled precursor, carbon extracted from the used tyres using a few processes is used to synthesize TiC with high purity. The use of tyre-derived carbon offers several environmental benefits such as facile synthesis, low cost, environment-friendly, etc. The as-synthesized TiC is further used as a precursor to synthesize low-cost Ti₃AlC₂. The structure of TiC and Ti₃AlC₂ are characterized by UV–visible spectroscopy and X-ray diffraction analysis. The microstructure and surface morphology of the samples are examined using scanning electron microscope imaging and energy-dispersive X-ray spectroscopy. The chemical bonding information is analyzed by Fourier transform infrared spectroscopy and the thermal behaviour of the samples are examined using thermogravimetric analysis. The successful cost-effective synthesis of TiC and Ti₃AlC₂ are confirmed from XRD analysis and the samples show high purity. TiC and Ti₃AlC₂ show excellent thermal stability which helps in their potential applications in the future. This study proclaims a new strategy to synthesize low-cost Ti₃AlC₂ MXene for the large-scale production using TiC precursor where the TiC precursor is synthesized using carbon precursor.

This study presents a data-driven framework based on machine learning (ML) using extreme gradient boosting (XGBoost) for predicting the hardness of silicon nitride (Si₃N₄) ceramics reinforced with graphene. The XGBoost model takes into account various factors such as graphene type and content, characteristics of the raw Si₃N₄ powder, the parameters of the sintering process (sintering technique, temperature, pressure, holding time), and the characteristics of the sintered samples, i.e., the density, $\frac{\alpha }{\beta }$ content and Vickers hardness. The parameters that influence the Si₃N₄ hardness most strongly are identified, with sintering pressure, sintering time and density being the most influential. The addition of graphene content up to a certain threshold (1 wt%) has a positive impact on hardness. However, beyond that it leads to a lower density and a lower mechanical performance. Sintering parameters, particularly the sintering pressure, temperature, holding time and technique, strongly affect the density, final grain size, $\frac{\alpha }{\beta }$ Si₃N₄ composition and subsequently the hardness. The study highlights the importance of density and the densification process in achieving high hardness in Si₃N₄ ceramics. The developed ML model provides a valuable tool for predicting the hardness of Si₃N₄+graphene ceramics composites and offers insights into selecting suitable graphene type, content, and processing parameters. While the study primarily focuses on Si₃N₄+graphene composites, this novel approach holds promise for the in-silico design and analysis of diverse ceramic materials.

In this work, hot-pressing of alumina in contact with hexagonal boron nitride or doped with boron carbide was conducted at 1500 °C for 30 min. After hot-pressing, abnormal grain growth induced by boron diffusion from these substances into alumina was detected, as clearly demonstrated with SEM, EDS, EBSD, and Raman spectroscopy. Grain boundary complexion transformations, solute drag, or another mechanism relating to interface-controlled grain boundary mobility are presumed to be the fundamental mechanism responsible for abnormal grain growth observed in this work.

This study investigates the effects of Nb₂O₅ as a dopant in TiO₂–Al₂O₃ ceramics to lower sintering temperature and enhance performance, including the physical, mechanical, and dielectric properties of the ceramics at sintering temperatures 1250 °C–1350 °C. Specifically, TiO₂–Al₂O₃ ceramics doped with 1.5 wt% Nb₂O₅ and sintered at 1350 °C exhibit remarkable density 94 %, compressive strength 1372 MPa, and abrasion resistance 1.36 × 10⁻⁴ mm³/N·m, surpassing those of pure alumina ceramics. This improvement is attributed to enhanced grain boundary diffusion and strain energy resulting from Nb⁵⁺ cation substitution. The incorporation of Nb₂O₅ in TiO₂–Al₂O₃ ceramics reduce sintering temperatures by 150–200 °C. The dielectric constant of TiO₂–Al₂O₃ ceramics doped with 1.5 wt% Nb₂O₅ sintered at 1350 °C is found to be 13.4, with a dielectric loss of 2.56 × 10⁻² and insulation resistance 7.3 × 10¹² Ω. Nb₂O₅ is an effective additive for reducing sintering temperatures in Al₂O₃ based ceramic.

The rheological properties of BAS (BaAl₂Si₂O₈) slurries are investigated in order to optimize the impregnation of an alumina preform to manufacture oxide/oxide composite materials. The fiber preform morphology has been deeply investigated, especially the fiber to fiber gap within tows and compared to the grain size of the matrix powder. The slurry viscosity is measured as a function of powder and organic additives concentration to find the best combination. The optimal combination is evaluated by different measurements including: zeta potential, sedimentation and wettability to verify the slurry behavior for the fibers infiltration. An aqueous slurry containing 20–25 vol% of BAS with 1 wt% of dispersing agent (Darvan 821-A™) improved the rheological properties for fibers infiltration. Finally, characterizations of the composite show a good infiltration in the fiber tows spaces and indicate a mean porosity of 37 vol%, including 9 vol% of macroporosity.

This study investigates ceramic fused filament fabrication (CF³) 3D printing of alumina with an emphasis on the impact of particle morphology on feedstock preparation and printability. Spherical powder displayed superior flow with higher apparent density, tap density, and powder packing fraction compared to irregular powder. A 55 vol % powder loading was chosen to ensure good flowability during printing. Irregular powder-based feedstocks had 40X higher viscosity than spherical powder feedstocks at 400 s⁻¹ shear rate, posing potential printing challenges. Slow printing speed maintained low feed-rates for consistent material flow. The debinding and sintering process produced macroscopically defect-free alumina components with relative densities above 89 % for both powder morphologies. The focus of the work is on comparing two different powder particle morphologies influencing feedstock behavior, printing fidelity, and sintered part properties.

Ceramic additive manufacturing (AM) requires a complex process chain with various post-processing steps that require expensive machines and special expertise. The key to further market penetration is AM that makes it possible to integrate into an already established ceramic process chain. Most successful AM technologies for ceramics are, however, based on processes that initially have been developed for polymeric materials. For ceramics AM, polymers or precursors are loaded with ceramic particles. This strategy facilitates the entry into AM, however the introduction of organic additives into the ceramic process chain represents a considerable technological challenge to ultimately obtain a ceramic component after additive shaping. In the present communication, two technologies based on ceramic suspensions will be introduced, the “layerwise slurry deposition” (LSD) and “laser induced slip casting” (LIS) technology. Both technologies take advantage of the high packing densities reached by conventional slip casting and moreover enable the processing of fines, even nanoparticles.

Processing-structure-property relationships of 3D-printed multi-scale porous ceramics were investigated. Direct ink writing (DIW) of oil-templated colloidal pastes produced hierarchically porous beta-tricalcium phosphate (TCP) scaffolds. Print architecture and microporosity within filaments were varied, mimicking bone structure. The scaffolds exhibited 60–70 % porosity with interconnected macropores 300–700 μm and microporosity within the filaments at the 10 micron-scale. Varying surfactant and oil concentrations created two micro-pore morphologies – bubble-like pores (emulsion) and channel-like pores (capillary suspension). Emulsion scaffolds were stronger, stiffer and more reliable than capillary suspension scaffolds under both compression and bending. Reducing nozzle diameter and inter-filament distance improved strength and stiffness, at lower density. Immersed at physiological pH, the hierarchically porous TCP scaffolds' strength and modulus degraded at a moderate rate suitable for bone tissue engineering (BTE). Mechanical behavior can be controlled by manipulating process parameters which influence the material's structure. These properties were comparable with trabecular bone, promising for BTE.

The wear behavior of SiC bonded diamond materials produced by liquid silicon infiltration in diamond preforms was investigated. The wear behavior in sand blasting tests (SiC abrasives, 5 bar pressure) was correlated with the microstructure. All SiC bonded diamond materials showed a wear, which was approximately 10 times less than the wear behavior of the reference SiC material.

Systematic changed microstructures were created by increasing the infiltration temperature. As the infiltration temperature increases, a graphite layer is formed at the diamond-SiC interface. At the highest infiltration temperature (1670 °C), the layer thickness reaches approx. 580 nm. The results show that wear resistance is not negatively affected by the graphite layer. On the contrary, for materials with a graphite layer thickness of up to 70 nm, the wear resistance increases by up to 30 %. The wear increases again only at the highest infiltration temperature. However, this is probably caused more by the internal damage to the diamonds and not by the graphite layer at the interface.

Additive manufacturing (AM) of ceramic bone implants from tricalcium phosphate (TCP) offers several benefits for bone regeneration and defect treatment. TCP scaffolds, e.g. featuring lattice or gyroid geometries, can effectively induce bone ingrowth and integration, showing a high potential in the treatment of large bone defects, e.g. as filler material for large bone defects. A major advantage of TCP is its osteoconductivity making it an effective choice for a broad range of orthopedic and dental applications. In addition, AM allows for the possibility to create precise, patient-specific implants with controllable mechanical properties. Those properties can be controlled by the implants' microstructure, e.g. in relation to bulk density and internal porosity. In this contribution, eleven resorbable bone implants were produced from β-tricalcium phosphate (β-TCP) in order to quantify the internal porosity in three dimensions using microcomputed tomography (μ CT). All components were manufactured using an extrusion-based process and scanned using an industrial μCT system at a voxel size of 10 μm. Two samples were physically prepared to allow a high-resolution μCT analysis at a voxel size of 1 μm. Results show that post-processed image data enables the non-destructive inspection of highly complex ceramic AM implants. Using μCT we were able to quantify internal porosity in β-TCP bone implant and quantify the geometry and distribution of wall thicknesses in the gyroid geometry. However, a detailed microstructural analysis is only possible using high-resolution μCT volume data, e.g. in relation to internal porosity. The findings emphasize that ceramic AM is able to produce complex components. However, NDT using μCT is crucial in the development of new materials and geometries. μCT provides high-resolution insights into the internal and external structure of ceramic AM components. It plays a critical role in detecting internal features, including small-scale porosity and delamination which are crucial for the integrity and functionality of medical implants. Moreover, μCT provides volumetric data that supports the design and manufacturing process at various stages, enabling an iterative approach of continuous improvement in mechanical performance and osseointegration.