Al2O3 Ceramics Research Articles

Experimental and numerical investigation on the ricochet of hard-core 7.62 small-calibre projectiles from the SiC and Al2O3 ceramic targets

The presented research concerns an experimental and computational investigation of the ricochet of small-calibre projectiles from ceramic tiles. The performed experimental tests were in situ observed by a multi-anode X-ray imaging and a high-speed camera. A detailed experimental verification of the geometrical conditions demonstrated that the projectiles' cores exhibit a similar behaviour dependent on the impact angle for two ceramic grades, Al2O3 and SiC. The experimental inquiry was complemented by a thorough numerical analysis of the failure of the investigated target/threat configurations using the Impetus Afea® software. The conclusions on the ricochet were reached based on the findings of the instrumented ballistic tests combined with advanced 3D numerical simulations, and it can be considered one of the few investigations on this phenomenon from ceramic surfaces.

Interaction mechanism between DD5 superalloy with different Y content and ceramic molds with Y2O3 layer

DD5 alloys with different Y content were produced by directional solidification (DS) using ceramic molds with the Y2O3 layer. The interaction mechanisms between the corresponding alloys and the Y2O3 layer were discussed. It was found that the Y2O3 layer effectively hindered the direct contact reaction between the active melt and the Al2O3 ceramics, which was conducive to improving the purity of the melt and reducing the loss of Y. Slight dissolution and decomposition of the Y2O3 layer under high temperature melt erosion resulted in the release of Y and O elements into the alloy. The involvement of Y in the melt changed the interfacial reaction mechanism between the Y2O3 layer and the alloy. The interfacial reaction products of melting the DD5 alloy without Y were Al2Y4O9 and Y2O3, while the interfacial reaction product of melting the DD5 alloy with Y was mainly Y2O3.

High-Temperature Synthesis of Cast Ceramic Material Al2O3–Cr2O3 + ZrO2

High-Temperature Synthesis of Cast Ceramic Material Al2O3–Cr2O3 + ZrO2

Utilization of fused deposition modeling in the fabrication of lattice structural Al2O3 ceramics

This study focuses on fabricating lattice structural Al2O3 ceramics with lattice infill densities ranging from 25 % to 70 % using filament-based fused deposition modeling (FDM) technology. A specialized filament for FDM printing was developed, comprising 53 vol% Al2O3 powder and ethylene vinyl acetate (EVA) as the primary binder component. The filament demonstrated excellent flexibility as assessed by a self-designed three-point bending test. The impact of lattice infill density and sintering temperature on dimensional changes, microstructure evolution, compressive strength, and strength-to-density ratio was explored. It was found that with increasing sintering temperature, the samples became more compact, resulting in higher levels of shrinkage, bulk density, and compressive strength. At a sintering temperature of 1600 °C, the sintered parts reached their maximum density through the solid-state sintering process. The sample sintered at 1600 °C with 70 % infill density exhibited the maximum compressive strength of 31.47 MPa, with a corresponding strength-to-density ratio of 20.84 MPa/g·cm−3. These findings highlight the successful fabrication of lattice structural Al2O3 with low density and high compressive strength by FDM technology.

The chemical compatibility of oxide ceramic candidates in static PbLi for advanced breeding blanket channel components

The use of a PbLi eutectic alloy is extended in the Dual Coolant Lead Lithium (DCLL) and Water Coolant Lead Lithium (WCLL) Breeding Blanket (BB) design concepts in future fusion reactors. However, the reactivity of PbLi is a challenging problem, as the flow liquid metal can damage metallic and ceramic materials. For the development of BB technologies, to conduct chemical compatibility studies of materials that will be exposed to the liquid metal is therefore critical. The advanced DCLL concept considers the use of ceramic channels, which could help to extend the BB operating window above 550 °C while improving the tritium-breeding ratio. Since BB components will be highly exposed to neutrons, the influence of PbLi in neutron-like damaged components is also of high concern as compositional changes may modify properties and functionality of the exposed material. Consequently, selected ceramics were submitted to long-term chemical compatibility experiments using COES, a lab-scale facility located at the Liquid Metal Laboratory at CIEMAT, Spain. Commercial Al2O3 ceramics were tested in the as-received and light-ion-implanted conditions, the resultant surfaces after static PbLi exposition being studied by SEM-EDX microstructural and SIMS analytical techniques. The conclusions after the long-term chemical compatibility experiments suggest that the use of bulk alumina ceramics in contact with PbLi is promising. Although lithium diffuses inside the ceramic transforming the initial alumina stequiometry, the surface structural damage is limited to the first 50 µm in the worst case, and could be still considered as a candidate ceramic material for the advanced DCLL BB.

Development of Macro-Encapsulated Phase-Change Material Using Composite of NaCl-Al2O3 with Characteristics of Self-Standing

Developing thermal storage materials is crucial for the efficient recovery of thermal energy. Salt-based phase-change materials have been widely studied. Despite their high thermal storage density and low cost, they still face issues such as low thermal conductivity and easy leaks. Therefore, a new type of NaCl-Al2O3@SiC@Al2O3 macrocapsule was developed to address these drawbacks, and it exhibited excellent rapid heat storage and release capabilities and was extremely stable, significantly reducing the risk of leakage at high temperatures for industrial waste heat recovery and in concentrated solar power systems above 800 °C. Thermal storage macrocapsules consisted of a double-layer encapsulation of silicon carbide and alumina and a self-standing core of NaCl-Al2O3. After enduring over 1000 h at a high temperature of 850 °C, the encapsulated phase-change material exhibited an extremely low weight loss rate of less than 5% compared with NaCl@Al2O3 and NaCl-Al2O3@Al2O3 macrocapsules, for which the weight loss rate was reduced by 25% and 10%, respectively, proving their excellent leakage prevention. The SiC powder layer, serving as an intermediate coating, further prevented leakage, while the use of Al2O3 ceramics for encapsulation enhanced the overall mechanical strength. It was innovatively discovered that the Al2O3 particles formed a network structure around the molten NaCl, playing an important role in maintaining the shape and preventing leakage of the composite thermal storage phase-change material. Furthermore, the addition of Al2O3 significantly enhanced the rapid heat storage and release rate of NaCl-Al2O3 compared to pure NaCl. This encapsulated phase-change material demonstrated outstanding durability and rapid heat storage and release performance, offering an innovative approach to the application of salt phase-change materials in the field of high temperature rapid heat storage and release and encapsulating NaCl as a high-temperature thermal storage material in a packed bed system. Compared with conventional salt-based phase-change materials, the developed product is expected to significantly improve the reliability and thermal efficiency of thermal storage systems.

Effect of multiple laser peening on the wear resistance of 304 stainless steel

PurposeThe purpose of this paper is to investigate the effect of laser peening (LP) on mechanical and wear properties of 304 stainless steel sheet.Design/methodology/approachThree-dimensional morphology, micro-hardness and micro-structure of shocked samples were tested. The wear amount, wear track morphology and wear mechanism were also characterized under dry sliding wear using Al2O3 ceramics ball.FindingsThe LP treatment generates deformation twins that contribute to the grain refinement and hardness increase. The wear test displays that the wear mechanism of samples is mainly abrasive wear and oxidation wear at 10 N load. While at 30 N, the delamination and adhesion areas of treated sample are reduced visibly compared to untreated ones.Originality/valueThis study specifically investigates the mechanical and wear properties of 304 stainless steel after the direct action of LP on its surface, which shows an effective improvement on the wear resistance. For example, the wear loss of processed sample is reduced by 19% at 30 N, the friction coefficient decreases from 0.4714 to 0.4308 and the groove depth is reduced from 78.1 to 74.4 µm under same condition.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0007/

Aluminium-assisted in situ synthesis of bulk SiC nanowhiskers-alumina ceramics using waste coal gangue with high carbon

The green and efficient use of coal gangue (CG) is urgently required in the Chinese coal industry to avoid its adverse environmental impact. This study proposed an Al-assisted carbothermal reduction method to synthesise SiC–Al2O3 ceramics using high-C CG. The optimised experimental conditions for sintering SiC and their effects on the phase composition and related properties of the composites were investigated. The addition of Al optimised the in-situ synthesis pathway of SiC and significantly improved the carbothermal reaction efficiency, making the reactive temperature decrease from 1500 to 1200 °C. Additionally, sintering temperatures could modulate the SiC morphology by affecting the generation of SiO (gas) and the liquid phase of melting Al. The H3 formulation sintered at 900 °C was appropriate for producing SiCw/Al2O3 ceramics with a bending strength of 49.24 MPa, a thermal conductivity of 1.720 W (m K)−1 and good thermal shock resistance (no cracks forming after 20 cycles). This study aimed to fully combine the reactivity changes of CG with the melting reduction reaction of Al. Findings in this work offer novel insights into the synthesis of structural ceramics and the cleaner use of CG for solar thermal storage.

Vat photopolymerization of silicon carbide strengthened alumina ceramic composites with honeycomb structure for heat insulation and oil/water separation

In this study, the effects of different silicon carbide (SiC) particle sizes on the viscosity and curing behavior of alumina (Al2O3) ceramic suspensions were thoroughly investigated. The findings revealed that increasing the size of SiC particles led to a noticeable decrease in the viscosity of the suspension. The Al2O3 ceramic suspension with 0.6 μm SiC powder demonstrated a shallower cure depth and wider excess width compared to the suspension with 1.0 μm SiC powder. Sintering tests demonstrated that the properties of the SiC–Al2O3 ceramics improved at higher sintering temperatures. Moreover, a high-performance honeycomb ceramic was successfully designed and fabricated with a porosity and compressive strength of 30.8 % and 188 MPa, respectively. Finally, the SiC–Al2O3 honeycomb ceramics were effectively applied in heat insulation and oil-water separation applications, demonstrating their remarkable capabilities.

Effects of refined grains and doped nanoparticles on fabricating Al2O3 ceramics using binder jetting

Adding sintering additives to fabricate alumina ceramics via the binder jetting (BJ) technique effectively enhances material properties. However, it is still limited by the disadvantages of low relative density and poor mechanical properties. This study proposed reducing matrix particle size and adding nanoscale particles using binder jetting to address the poor densification and strength of printed alumina (Al2O3) samples. Additionally, their effects on the mechanical properties and manufacturability of the material were explored. Numerical simulations were carried out before the experiments to predict the impact of particle stacking on the powder bed using the discrete element method (DEM). Then, filler particles with an average 40 μm size replaced the original 106 μm-sized Al2O3 particles. Subsequently, Al2O3 nanoparticle content in the samples was gradually increased, and the relevant properties of the sintered samples with different compositions were tested. Consequently, the size of the Al2O3 particles and the addition of Al2O3 nanoparticles significantly affects the physical and mechanical properties of the samples. The sample with 106 μm-sized particles has a compressive strength of 58 MPa, while reducing the particle size to 40 μm increases its compressive strength by 26 %. Moreover, the sample's compressive strength could reach up to 330 MPa, an increase of 513 %, and the hardness reaches 1215 HV (11.91 GPa) by expanding the Al2O3 nanoparticles content to 30 %. Additionally, using Al2O3 nanoparticles further reduces the sintering temperature, significantly improving the practicality of Al2O3 printing using binder jetting.

Selection strategy of curing depth for vat photopolymerization 3D printing of Al2O3 ceramics

Vat photopolymerization (VPP) 3D printing technology allows the fabrication of complex ceramic structure components through the layer-by-layer stacking strategy. The curing depth is a crucial parameter for the stacking process, as it directly impacts the printing quality. Furthermore, this parameter exerts a profound effect on the final quality of the printed part. However, there is currently a lack of comprehensive research on how the curing depth affects VPP ceramic 3D printing. This study aims to thoroughly evaluate the impact of curing depth parameters on critical aspects of the 3D printing process, including the forming accuracy, surface quality, monomer conversion, resin pyrolysis, interlayer defects, and mechanical properties. The results of our investigation clearly demonstrate the significant influence of curing depth on the precision and performance of VPP 3D printed ceramic parts. Ceramic samples produced with higher curing depth exhibited superior surface quality (Ra<1.6 μm) but lower forming accuracy. Increasing the curing depth improved interlayer adhesion but excessive depth led to a decreased monomer conversion content from 5.2 % to 2.0 % and an internal stress in the green body. Moreover, increasing the curing depth intensified the pyrolysis process and increased the propensity for cracks forming, as confirmed by simultaneous thermal analysis and microstructure observations. The flexural strength of the sintered samples reached its maximum value of 630 MPa at three times the printing layer thickness. This study provides valuable insights for selecting appropriate curing depth parameters in VPP ceramic 3D printing.

Flexible ceramic based ‘paper separator’ with enhanced safety for high performance lithium-ion batteries: Probing the effect of ceramics impregnation on electrochemical performances

Cellulose is now considered as an appealing environment friendly material for the development of sustainable separators for rechargeable batteries. This study thus aims to develop high performance paper based ceramic separators with superior electrolyte wettability (>170 %), high thermal stability (>200 °C) and excellent flame safety. While developing paper based ceramic separator, extensive studies are carried out to understand thenature and functionality of different nano-structured ceramic materials (Al2O3, BaTiO3 and ZrO2) impregnated in paper matrix. Nano-ZrO2 facilitates an effective pathway for Li +-ion transport (tLi+ = 0.51), whereas BaTiO3 and Al2O3 ceramics show moderate Li +-ion transport properties (tLi+ of 0.29 and 0.30 respectively). Electrochemical Impedance Spectroscopy (EIS) measurement clearly reveals that ZrO2 exhibits more interfacial compatibility with the electrodes (MCMB and LiNi1/3Mn1/3Co1/3O2) compared to the other two ceramic separators during full cell operation. The developed paper separators show excellent electrochemical properties in terms of cycling (tested 300 cycles), multi-electrode compatibility and rate capabilities at different current densities of 0.1–1.2 mAcm−2. The pre- and post-electrochemical EIS data reveal that ZrO2 based impregnation offers significantly lower charge transfer resistance compared to the other two separators. The study thus demonstrates a real promise for its successful application in Li-ion battery towards achieving sustainability and safety.

Fabrication of high-performance pure alumina ceramics with defect-rich structures by dynamic sinter forging

In this study, α-Al2O3 was sintered by dynamic sinter forging (DSF). The grain growth, mechanical properties and microstructures of the resultant ceramics were investigated in detail. The results showed that the grain growth during DSF was dominated by a dynamic grain growth process, in which grain size increased with an increase in pressure. The flexural strength of the ceramics increased with increasing pressure and reached 770 MPa in the sample prepared at 1300oC and 100 ± 10 MPa, which was significantly higher than that of the samples prepared by hot pressing and hot oscillatory pressing. The high strength was contributed to the severe plastic deformation induced by the oscillatory pressures, which strengthened both grain boundaries and grains. The current study suggests that DSF is a promising technique for preparation of high-performance Al2O3 ceramics, better than hot pressing and hot oscillatory pressing.

Melting ceramic Al2O3 powder by electron beam powder bed fusion

Electron beam powder bed fusion (PBF-EB) is a known metal additive manufacturing (AM) technology. Processing non-conducting powders such as ceramics has so far been considered as not feasible because of the inherent problems with Coulomb repulsion due to insufficient electrical conductivity. In this study, a method for functionalizing ceramic powder is proposed where particles are electroless coated by a ~ 1 µm Ni layer to decrease the surface resistivity. The feasibility of the suggested approach is tested on Al2O3 powder, and the results show that the coated ceramic powder has a decreased surface resistivity, which enables processing by PBF-EB. Heating and melting parameters were investigated and samples were manufactured at ~ 1600 °C. Sintered and melted powders were analyzed by microscopy and micromechanically tested by nanoindentation. Calculations, visual observation and SEM–EDX suggest that the Ni coating is evaporated during the process, which suggests that the process could be feasible for the manufacturing of pure ceramic parts.

Enhanced microwave dielectric properties of Al2O3 ceramics via a cold sintering assisted two-step sintering route

Enhanced microwave dielectric properties of Al2O3 ceramics via a cold sintering assisted two-step sintering route

Cu metallization of Al2O3 ceramics via CuO reduction: Role of SiO2 additive and sintering atmosphere

A Cu-coated Al2O3 substrates which can be used for power modules are prepared via sintering and reduction of CuO–SiO2 film onto the surface of Al2O3 ceramic without precious metal brazing filler or high-vacuum equipment. This method has a significant cost advantage over the existing technology. Effects of oxygen partial pressure from sintering atmosphere and SiO2 content on microstructure and mechanical properties of Cu/Al2O3 interface are systematically investigated. Phase compositions and morphologies of sintered Cu2O layer, reduced Cu layer and reactive layer are characterized via X-ray diffraction and scanning electron microscopy. In addition, physicochemical changes within CuO–SiO2 during sintering are characterized by thermogravimetry-differential scanning calorimeter. It is found that oxygen and SiO2 can promote the generation of Cu2O–CuO–SiO2 eutectic phase with low melting point upon sintering, which increases the thickness of reaction layer and the densification of Cu layer. The shear strength between the Cu layer and the Al2O3 substrate is enhanced with the increase in Cu layer densification degree, while varying in irregular manner with the thickness of reaction layer. In particular, the highest shear strength of 62.70 MPa is obtained at oxygen partial pressure of 0.02 atm and SiO2 content of 1.5 wt%.

Influence of mechanical properties on material deformation behavior of different ceramics in scratching

To understand the differences in material removal behavior during grinding for different ceramics, scratching of Al2O3, AlN, Si3N4 and ZrO2 (3Y-TZP) ceramics by a cube-corner diamond indenter was investigated in this paper. Scratching characteristics, including material deformation, scratching force, coefficient of friction (COF) and scratching damage of different ceramics were compared and analyzed. Elastic recovery rate model and stress field model were built to analyze the mechanism of material deformation and scratching damage during scratching on different ceramics. The results demonstrated that material deformation behaviors vary significantly, and depend on mechanical properties of the ceramics. Ceramics with higher hardness exhibit shallower penetration depth of scratching, while higher fracture toughness results in shorter maximum surface damage distance. Elastic recovery rate model can predict the extent of material deformation. The ceramic with the highest elastic recovery rate is Al2O3, followed by Si3N4, ZrO2, and finally AlN. Elastic recovery rate decreases with increase in force. In stress field model, AlN exhibits the highest maximum principal stress, followed by Al2O3 and Si3N4, with ZrO2 displaying the lowest stress. These distribution patterns are consistent with the results of scratching damage pattern.

High thermal conductivity and high energy density compatible latent heat thermal energy storage enabled by porous Al2O3@Graphite ceramics composites

Phase change material (PCM) is an ideal heat storage material with huge latent heat and nearly constant phase change temperature, but there are serious problems in application such as leakage and low thermal conductivity. Porous ceramic is widely used in PCM packaging because of its advantages of controllable porosity and high thermal conductivity. Porous Al2O3 ceramics were prepared by foaming injection coagulation method. In order to improve the thermal conductivity of porous ceramic matrix, Porous Al2O3@Graphite Ceramics (PAGC) were prepared by sucrose decomposition. Form-Stable Phase Change Materials (FSPCMs) were prepared by adsorption of Lauric Acid/Myristic Acid (LA/MA) in PAGC by vacuum impregnation method. SEM showed that the prepared PAGC had a three-dimensional interpenetrating structure and high porosity. TEM and XPS showed that alumina skeleton were uniformly coated with graphite. After PAGC impregnated by LA/MA, the maximum PCM storage reached 62.11 wt %. The maximum latent heat of FSPCMs reaches 83.33 J/g. Thermogravimetric analysis, thermal cycling test and Fourier transform infrared spectroscopy show that the prepared FSPCMs has good thermal stability, thermal reliability, chemical stability and compressive strength. More importantly, the thermal conductivity of the prepared FSPCMs is greatly improved, reaching up to 3.73 W/mK. It is 20.72 times the original PCM, mainly due to the synergistic effect of the Al2O3 skeleton and the graphite coating to build a continuous highway for heat transfer. This study provides a practical means to greatly improve the thermal conductivity of FSPCMs, which will promote the practical application of FSPCMs.

Development of a novel bulk metallic glass bonded single-layer diamond wheel

A novel manufacturing process was employed to develop a single-layer diamond wheel using bulk metallic glass (BMG) as the matrix and diamond particles as abrasives. BMG effectively prevented graphitisation and damage to the diamond abrasives because of its lower manufacturing temperature and avoidance of brazing flux. The Titanium (Ti) coating on the surface of diamond abrasives facilitated the formation of an interleaved dissolution-diffusion interface between the two constituents, creating mechanical occlusion at the BMG-diamond interface. The strong and tight bonding interface afforded a diamond abrasive joint strength of up to 112.59 N, with the main shear failure mode being transgranular fracture instead of pull-off failure. Furthermore, the manufactured BMG-bonded single-layer diamond wheel predominantly exhibited attritious wear instead of the exfoliation of abrasives when grinding Al2O3 ceramics. Compared with contemporary electroplated grinding wheels, the developed diamond wheel demonstrated a reduction in the normal and tangential grinding forces of 32.64% and 35.86%, respectively, and a 28.22% increase in the grinding ratio, making it an excellent candidate for grinding hard and brittle materials.

Effect of Radial Directional Vibration-Assisted Ductile-Mode Grinding of Al2O3 Ceramics

Effect of Radial Directional Vibration-Assisted Ductile-Mode Grinding of Al₂O₃ Ceramics