Strength Of Ceramics Research Articles

Microstructure and Properties of Pressureless-Sintered Zirconium Carbide Ceramics with MoSi2 Addition.

Zirconium carbide (ZrC) ceramics have a high melting point, low neutron absorption cross section, and excellent resistance to the impact of fission products and are considered to be one of the best candidate materials for fourth-generation nuclear energy systems. ZrC ceramics with a high relative density of 99.1% were successfully prepared via pressureless sintering using a small amount of MoSi2 as an additive. The influence of the MoSi2 content on the densification behavior, microstructure, mechanical properties, and thermal properties of ZrC ceramics was systematically investigated. The results show that the densification of ZrC was significantly enhanced by the introduction of MoSi2 due to the formation of a liquid phase during sintering. In addition, the ZrC grains were refined due to the pinning effect of the generated silicon carbide. The flexural strength and Vickers hardness of ZrC ceramics with 2.5 vol% MoSi2 sintered at 1850 °C were 408 ± 12 MPa and 17.1 GPa, respectively, which were approximately 30% and 10% higher compared to the samples without the addition of MoSi2. The improved mechanical properties were mainly attributed to the high relative density (99.1%) and refined microstructure.

Digital light processing‐based additive manufacturing of orientation‐controlled Al2O3 ceramics with improved damage tolerance

AbstractDigital light processing (DLP) provides a promising avenue for constructing ceramic parts with high precision and complex shapes, yet the inherent brittleness and strength‐toughness trade‐off hinder their wide applications. Here, according to DLP 3D printing, the textured alumina ceramic components with horizontally aligned textured microstructure were successfully created by adding anisotropically shaped platelets. As a critical process in the preparation of textured ceramics, the alumina platelets were aligned horizontally during printing by using the special shear fields and forming capabilities of DLP technology. The shrinkage, density, microstructure, mechanical performance, and damage‐tolerance behavior of alumina parts with different platelet concentrations were examined, and the toughening mechanisms were investigated. The strength and toughness of ceramics with 5 vol.% platelet addition are increased by 22% and 43%, respectively, as compared with those without platelets. The improved damage tolerance capabilities were primarily ascribed to the collaborative toughening mechanisms stimulated by the platelet addition, including crack branching, crack deflection, uncracked‐ligament bridging, and platelet pull‐out, which increased the crack tortuosity and consumed more fracture energy. The strategy opens up new opportunities to design complex 3D ceramic geometries with bio‐inspired layered or textured architectures, providing optimized damage tolerance.

Enhancement of Flexural Strength by Slip Casting Cordierite Ceramics with h-BN Nanoparticles

In this study, we enhanced the flexural strength of cordierite ceramics by incorporating h-BN (hexagonal boron nitride) nanoparticles, facilitated by the slip casting process. Initially, commercial cordierite powder with an average particle size of 10 mm underwent a ball-milling process to reduce the size to 2.5 mm and simultaneously achieve a narrower particle size distribution. The resulting slurry, composed of 67% solid content, exhibited improved stability during the slip casting process for both pristine cordierite and the mixture containing 1 – 2 wt% h-BN nanoparticles. After sintering, the bulk material containing 2wt% h-BN nanoparticles demonstrated a remarkable flexural strength of 174.8 MPa, a significant improvement compared to the initial 119.5 MPa obtained without the addition of h-BN. It is worth noting that the introduction of h-BN nanoparticles did not induce substantial changes in dielectric constant and thermal conductivity, indicating that the desired mechanical enhancement did not compromise other crucial material properties. This research demonstrates a successful approach to concurrently optimize the flexural strength, dielectric constants, and thermal conductivity of cordierite ceramics. This breakthrough opens up new avenues for advanced applications in a wide range of fields, from electronics to aerospace, where high-strength, thermally stable materials are in demand.

Influence of Different Surface Treatments on the Bond Strength of Yttria-Stabilized Tetragonal Zirconia Ceramic.

Objective: This in vitro study evaluates the shear bond strength (SBS) of yttria-stabilized tetragonal zirconia (Y-TZP) and resin cement after different surface treatments. Materials and methods: Forty-eight ceramic cubes were divided into four groups (n = 12): G1 (control) sandblasting with Al2O3; G2-sandblasting with silica-coated Al2O3 (Rocatec); G3-Rocatec + CO2 laser; and G4-CO2 laser + Rocatec. A metallic primer was applied to the pretreated ceramic. A rubber ring was adapted on the central area, and then, the resin cement was inserted into the matrix and photoactivated. The samples were evaluated regarding surface roughness (Ra), SBS, failure type, and qualitatively with scanning electron microscopy (SEM). The data were analyzed by one-way analysis of variance followed by Tukey's test (p < 0.05). Results: The mean values of Ra (μm) were as follows: G1-4.52a, G2-4.24a,b, G3-4.10a,b, and G4-2.90b and the mean values of SBS (MPa) were as follows: G1-7.84a , G2-4.41b , G3-4.61b and G4-6.14a,b. SEM analyses showed superficial irregularities for all groups, being more prominent for G1. The presence of silica deposits was observed for G2, G3, and G4, but in the last two groups there were some linear areas, promoted by the fusion of silica, due to the thermomechanical action of the CO2 laser. Conclusions: The surface treatment with CO2 laser + Rocatec, using one MDP-based cement, can be an alternative protocol for the adhesion cementation of Y-TZP ceramic since it was as effective as the conventional pretreatment with aluminum oxide sandblasting.

Robust, thermally insulating, and high-temperature resistant phosphate-enhanced mullite fiber porous ceramic composites

Porous mullite ceramics with high porosity and low thermal conductivity are urgently required as high-temperature thermal insulators in harsh environments. How to improve the strength of Porous mullite ceramics dramatically under the premise of no sacrificing its thermal insulating properties has remained an extremely challenging. Inspired by the freezing rain phenomenon in nature, high-strength and high-temperature resistant phosphate coatings were applied to the surface of mullite fibers, which significantly improved the mechanical properties of porous mullite ceramics without significantly increasing their thermal conductivity. The Al(H2PO4)3 solution concentration significantly affected the mechanical and thermal properties of the composite material, where the mechanical performance improved with an increasing Al(H2PO4)3 solution concentration. The phosphate coating phase stabilized with an increasing calcination temperature. The mechanical properties of the ceramics were improved by the excellent interfacial bonding strength between the coating and mullite fiber, and the forms of phosphate in the porous ceramics. The optimum composite preparation process increased its compressive strength by approximately nine-fold to 4.1 MPa and resulted in a thermal conductivity of only approximately 0.09 W/(m·K), demonstrating that the composite exhibited a significantly higher comprehensive performance than other previously reported porous ceramics and aerogels. Such new composites with excellent mechanical and thermal insulation properties exhibit excellent potential for high-strength thermal insulation in the chemical, metallurgical, pharmaceutical, aerospace, and other fields.

Effect of graphite content on the microstructure and mechanical properties of SLS-based RB-SiC ceramics

In this study, reactive bonded (RB)-SiC ceramics were fabricated using a combination of selective laser sintering (SLS) and reactive melt infiltration (RMI). The microstructure and mechanical properties of RB-SiC ceramics were optimized by adjusting the graphite content. The sintered bodies were found to consist of α-SiC, β-SiC, Si and C. The addition of graphite prolonged the reaction time between carbon and silicon, resulting in a greater infiltration of molten silicon and an increased formation of β-SiC. Furthermore, a correlation was observed between the proportion of graphite content and the bulk density and bending strength of RB-SiC ceramics. In the range of 0–10 wt%, the bulk density initially increased and then decreased as the graphite content increased. The maximum density was found to be 2.74 ± 0.15 g/cm3. The flexural strength reached the maximum value at 217.9 ± 16.9 MPa when the graphite content was 5 wt%. However, beyond this point, the flexural strength decreased rapidly. The present research demonstrates the promising potential of utilizing SLS additive manufacturing to fabricate SiC ceramics with exceptional mechanical properties.

Dense and high flexural strength cordierite ceramics doped with Li2O

High-strength cordierite ceramics with Li2O were fabricated by non-pressure sintering. The results showed that the addition of Li2O significantly reduced the sintering temperature and expanded the sintering range. Additionally, the mechanical strength of the samples clearly increased after Li2O doping. In particular, the sample with 0.5 wt% Li2O sintered at 1250 °C showed the best properties, with a flexural strength of 178.6 MPa and a thermal expansion coefficient of 2.1 × 10−6 °C−1. Its flexural strength is much higher than samples without Li2O and the cordierite ceramics prepared by non-pressure sintering reported in the literature. The high density of the sample (2.52 g cm−3) is the main reason for its excellent mechanical properties. Furthermore, first-principles calculations verify that Li+ dopants insert at the vacant channel of α-cordierite crystal with six-fold coordination, which may reduce the anisotropy of the thermal expansion coefficient of α-cordierite, thus improving the strength of ceramics.

Study of the Influence of Doping Efficiency of CeO2 Ceramics with a Stabilizing Additive Y2O3 on Changes in the Strength and Thermophysical Parameters of Ceramics under High-Temperature Irradiation with Heavy Ions

The article outlines findings from a comparative analysis of the effectiveness of doping CeO2 ceramics with a stabilizing additive Y2O3 on alterations in the strength and thermophysical parameters of ceramics under high-temperature irradiation with heavy ions comparable in energy to fission fragments of nuclear fuel, which allows, during high-temperature irradiation, to simulate radiation damage that is as similar as possible to the fission processes of nuclear fuel. During the studies, it was found that the addition of a stabilizing additive Y2O3 to the composition of CeO2 ceramics in the case of high-temperature irradiation causes an increase in stability to swelling and softening because of a decrease in the thermal expansion of the crystal lattice by 3–8 times in comparison with unstabilized CeO2 ceramics. It has been determined that the addition of a stabilizing additive Y2O3 leads not only to a rise in the resistance of the crystal structure to deformation distortions and swelling, but also to a decrease in the effect of thermal expansion of the crystal structure, which has an adverse effect on the structural ordering of CeO2 ceramics exposed to irradiation at high temperatures.

Digital precision in engineered ceramics: Tailoring toughness and flexibility through interlocking strategies

Precise material architectures and interfaces can render conventional ceramics tough, deformable and damage-resistant, offering a wide range of possibilities beyond those provided by conventional ones. This study explores the mechanical properties of topologically interlocked ceramic panels by systematically varying architectural parameters (i.e., interlocking angles and building block sizes) using a combination of experimental testing and finite element modeling based on COMSOL Multiphysics®. Three distinct designs were fabricated using digital laser manufacturing, categorized as designs with constant interlocking angles and tile sizes, constant interlocking angles and variable tile sizes, and variable interlocking angles and tile sizes and subjected them to out-of-plane quasi-static loads. The results show substantial enhancements in toughness (up to 110%) and strength (up to 120%) for ceramics with varying building block sizes, compared to those with constant block sizes. Additionally, these ceramics exhibit increased flexibility (up to 130%) compared to plain ceramics. Larger interlocking angles contribute to superior mechanical properties, fostering increased energy absorption and stability. The study also investigates post-failure behavior, revealing that increasing length ratios consistently augment the energy absorption. This research highlights the potential of these materials for flexible protection and the importance of controlling architectural parameters based on the interlocking angle and building block size to optimize performance while minimizing damage.

Comparative evaluation of shear bond strength to dentin with three different aesthetic chemically bonded restorative materials – an In-vitro study

The use of glass ionomer cements (GIC) as a restorative material was limited to areas of low masticatory forces due to their low mechanical properties which were also affected by the powder/liquid mixing ratio of this material. Bond strength is important for the clinical success of adhesive material. The shear bond strength (SBS) is the maximum force that an adhesive joint can tolerate before fracture which is tested by SBS tests. The high bond strength helps the adhesive to resist stresses caused by resin contraction and forces for a longer time and thus prevents the problems of bond failure such as recurrent caries, tooth sensitivity and restoration failure. GIC as a restorative material has the capacity to release fluoride and shows good bonding ability. The use of GIC in anterior applications appears to be satisfactory, but they have limitations for use in permanent posterior teeth, particularly with regard to large restorations. Zirconia-reinforced GI (Zirconomer, Shofu Inc, Japan) is a new class of restorative material containing reinforced glass ionomer with special zirconia fillers that promises the strength and durability of amalgam with the protective benefits of glass ionomer while eliminating the hazards of mercury. Amalgomer CR (Advanced Health Care, Tonbridge, Kent, UK), a novel ceramic-reinforced GIC, was introduced, which combines the benefits of GIC with the high strength of ceramics. In the present study, shear bond strength to the dentin with Zirconomer, Amalgomer CR and Fuji type IX GIC (GC Tokyo) are compared.

Comparative evaluation of shear bond strength to dentin with three different aesthetic chemically bonded restorative materials – an In-vitro study

The use of glass ionomer cements (GIC) as a restorative material was limited to areas of low masticatory forces due to their low mechanical properties which were also affected by the powder/liquid mixing ratio of this material. Bond strength is important for the clinical success of adhesive material. The shear bond strength (SBS) is the maximum force that an adhesive joint can tolerate before fracture which is tested by SBS tests. The high bond strength helps the adhesive to resist stresses caused by resin contraction and forces for a longer time and thus prevents the problems of bond failure such as recurrent caries, tooth sensitivity and restoration failure. GIC as a restorative material has the capacity to release fluoride and shows good bonding ability. The use of GIC in anterior applications appears to be satisfactory, but they have limitations for use in permanent posterior teeth, particularly with regard to large restorations. Zirconia-reinforced GI (Zirconomer, Shofu Inc, Japan) is a new class of restorative material containing reinforced glass ionomer with special zirconia fillers that promises the strength and durability of amalgam with the protective benefits of glass ionomer while eliminating the hazards of mercury. Amalgomer CR (Advanced Health Care, Tonbridge, Kent, UK), a novel ceramic-reinforced GIC, was introduced, which combines the benefits of GIC with the high strength of ceramics. In the present study, shear bond strength to the dentin with Zirconomer, Amalgomer CR and Fuji type IX GIC (GC Tokyo) are compared.

Damage mechanisms of Ti3AlC2 ceramics in pulsed laser processing

The damage mechanisms of Ti3AlC2 ceramics during laser processing in air and water were studied using the pulsed laser. The focused high-energy laser induced the melting of surface of Ti3AlC2 ceramics, causing the decomposition of Ti3AlC2 into TiC and Al with Al rapidly evaporating. During the laser processing in the air, oxygen diffused inward to form a solid solution of TiCxOy, and the rapidly heating and cooling of resolidified layer generated high thermal tensile stresses to result in a large amount of microcracks. When processing in the water, the thermal stresses were greatly weakened, and the outward diffusion of Al steam resulted in the voids on the sample surface. Additionally, it is determined that after treating in the air and water, the residual flexural strengths of Ti3AlC2 ceramics could retain the high values of 292 MPa and 484 MPa, and the Weibull moduli were kept at 7.2 and 16.0, respectively, exhibiting the excellent damage tolerance and high reliability.

Penetration resistance of corrugated hybrid structures with ceramic insertions against steel projectile impact

Ceramic-metal corrugated structures have attracted extensive attention because of their strong penetration resistance. In this study, the effects of geometric features and boundary constraints on corrugated structures consisting of a TC4 frame and five SiC ceramic prisms were explored by performing a series of ballistic tests. Deformation results were obtained using a three-dimensional scanner, and the dynamic response was observed using a high-speed imaging system. Numerical models of these tests were established and validated using experimental results. The results suggest that increasing the support and confining strength of ceramics delay their failure and increase their degree of breakage, thereby increasing the internal energy conversion ratio of the projectile and the energy absorption ratio of ceramics by 14% and 10%, respectively. Notably, a reasonable reduction in the strength of the frame partition expands the plastic deformation range of the frame and increases its energy absorption ratio by 10%. The conclusions of this study provide a reference for designing corrugated composite structures.

Effect of La2O3 adding on Properties of SiC Porous Ceramic Support

In this paper, 80-90 grains of SiC as the main raw material, doped La2O3 into the binder composed of potassium feldspar, kaolinite and quartz, and then graphite and activated carbon as pore-making agents to prepare silicon carbide porous ceramic carrier. The effects of doped La2O3 content on the bending strength, porosity and filtration pressure drop of porous SiC ceramics were studied. The results show that the formation of mullite phase and the bending strength of SiC porous ceramics can be improved by adding proper amount of La2O3. Under the sintering temperature of 1300°C for 90 minutes, when the content of La2O3 in the binder is 2.5wt%, the comprehensive performance is the best, the porosity is 21.5%, the bending strength is 53.5MPa, and the filtration pressure drop is low.

Effects of Various Laser Treatments on Surface Characterization and Repair Bond Strength of Zirconia-Reinforced Lithium Silicate Ceramics.

To evaluate the effects of two different lasers and their use in combination with hydrofluoric acid (HF) etching on the surface roughness of zirconia-reinforced lithium silicate (ZLS) ceramics and their shear bond strength (SBS) to composite resin. The five study groups were as follows: (1) Group H = HF etching; (2) Group N = Nd:YAG (neodymium: yttrium-aluminum-garnet) laser; (3) Group NH = Nd:YAG laser + HF gel; (4) Group E = Er:YAG (erbium: yttrium-aluminum-garnet) laser; and (5) Group EH = Er:YAG laser + HF gel. Surface roughness was assessed using a noncontact profilometer, and SBS tests were conducted with a universal testing machine. The mean SBS values were 16.23 ± 1.77 MPa for Group H, 17.1 ± 1.65 MPa for Group N, 16.65 ± 1.11 MPa for Group NH, 8.08 ± 1.12 MPa for Group E, and 11.58 ± 0.82 MPa for Group EH. There were significant differences between groups E and EH (P < .001) but no significant differences (P > .05) among the other groups. Clinicians may prefer Nd:YAG laser or the combination of Nd:YAG and HF to intraorally repair fractured areas.

Preparation, microstructure and properties of cordierite-mullite-corundum porous ceramics for high-temperature gas-solid separation

In order to obtain ceramic materials for high-temperature gas-solid separation, the cordierite-mullite-corundum porous ceramics were prepared by particle stacking and pore-forming agent method, with bauxite as aggregate and in-situ synthesized cordierite as binder. Designed four-factor four-level orthogonal experiments for the first time to improve the porosity of the samples. The phase composition and microstructure of the samples were studied by XRD, SEM and other testing methods. The results show that: X6 sample (firing temperature of 1340 °C, 50 wt% binder, aggregate coarse, medium and fine mass percentage 30:50:20, plus 20 wt% charcoal powder, 10 wt% graphite) has the best comprehensive performance, with porosity of 41.51 % and bending strength of 17.88 MPa. Pore size distribution range from 10 to 40 μm. Corundum and mullite, with excellent high-temperature properties formed by the aggregate, are tightly bonded together by cordierite, contributing to the strength of the porous ceramics. The addition of pore-forming agent improves the porosity and forms a stable and uniform pore structure in the porous ceramics. The high porosity and large connected pore size reduce the viscous resistance of the porous ceramics to the gas, improve the filtration performance of the material, and make it expected to be applied in the field of hot gas clean-up.

Microstructure and dielectric properties of Na and Ni co-substituted CaCu3Ti4O12 ceramics with high dielectric constant and low loss

Preparation of Na and Ni co-substituted CaCu3Ti4O12 (CCTO) ceramics through sol-gel method is carried out to enhance the dielectric properties. On the morphology and dielectric properties of CCTO ceramic, the effects of Na and Ni co-substitution are investigated. The results demonstrate that at room temperature, Na and Ni co-substituted Ca0.993Na0.007Cu2.95Ni0.05Ti4O12 exhibits significantly increased grain size and consequently a high dielectric constant exceeding 12000 across a broad frequency range (1–105 Hz). Meanwhile, its dielectric loss is reduced to 0.016 at 1 kHz, a phenomenon that can be ascribed to the raised resistance and activation of grain boundary. Furthermore, Ca0.993Na0.007Cu2.95Ni0.05Ti4O12 also yields a breakdown field strength of 2.3 kV/cm. The giant dielectric response can be explained by the internal barrier layer capacitor model. These excellent comprehensive performances not only contribute to obtain simultaneously low dielectric loss and high breakdown strength for CCTO ceramics with high dielectric constant, but also can facilitate the practical application of CCTO ceramics in advanced capacitors.

Effect of Addition of ZrO2 on Biaxial Flexural Strength of Calcium Phosphate Ceramics

The aim of this study is to investigate the effect of addition of ZrO2 on the biaxial flexural strength (BFS) of ceramics fabricated using a conventional powder technology. Various compositions of hydroxyapatite (HAp) Ca10(PO4)6(OH)2 and zirconia powder ZrO2, ranging from 10 to 90 wt% ZrO2, were prepared using a wet mixing process. Ten compacts (13.5mm3mm) were made for each group, pressed and sintered in air at sintering temperatures from 1100 to 1450oC for up to 12 hours. The bulk density, porosity, linear shrinkage and BFS. The porosity reduced and linear shrinkage increased with increasing sintering temperature and amounts of zirconia, whereas the sintering time had little effect. The highest mean value achieved for the BFS was 26920 MPa for a composition of 70% ZrO2 and 30% HAp fired at 1450oCfor 6 hours. From the experimental results can be conclude that sintering temperature and composition affect densification behaviour of calcium phosphate/ ZrO2 composites. The BFS increases with a reduction of porosity and increases with both sintering temperature and additions of ZrO2. It was noted that there is considerable scope for improvement in the BFS values by reducing the porosity of these composites.

Mechanical properties and forming conditions optimization of SiC ceramics using Camellia oleifera shell as carbon source

AbstractUsing Camellia oleifera shell as raw materials to preparative SiC ceramics by warm‐press forming and sintering is proposed in this paper. Warm‐press forming before preparing for the C. oleifera shell‐based SiC ceramics is beneficial to obtain the internal uniform and suitable pore structure of the cylindrical sample. Thermogravimetric analysis with differential scanning calorimetry was applied to analyze the pyrolysis behavior of C. oleiefra shell and phenolic resin. The scanning electron microscope and X‐ray diffraction were used to investigate the properties of C. oleifera shell‐based SiC ceramics. Then, the response surface method was applied to establish a multivariate prediction model based on the process parameters of warm‐press forming. And the regression equations of porosity and bending strength of COS‐SiC are obtained. The result demonstrated that the predicted and experimental values can be in good agreement for the model. By comparing the F‐value, it is found that the forming temperature and pressure during the process of warm‐press forming have a more significant influence on the porosity and bending strength of SiC ceramics. The optimization process parameters were obtained as follows: forming temperature 153°C, pressure 35 MPa, and holding time 30 min.

Effect of BPO4-B2O3 Composite Additive on Crystallization and Sintering of Silica Ceramics

BPO4-B2O3 composite additive enhanced silica ceramics were successfully prepared by solid phase sintering. The effects of BPO4-B2O3 addition and sintering temperature on the microstructure and phase composition and mechanical properties of silica ceramics were analysed by scanning electron microscopy and X-ray diffraction techniques. The results showed that at 1200°-1400°C, BPO4-B2O3 composite additive formed a glass phase in the sample, filled the pores, and improved the sintering densification of the sample. In addition, the addition of 9 wt% BPO4-B2O3 successfully inhibited the crystallization of fused silica, which significantly improved the mechanical strength of silica ceramics. After sintering at 1200°C for 3 h, the apparent porosity of silica ceramics with 9 wt% BPO4-B2O3 was only 1.33%, and the cold modulus of rupture reached a maximum of 60.99 MPa, which was about 35 times that of pure silica ceramics. It is shown that adding BPO4-B2O3 composite additive provides a feasible method for preparing silica ceramics with good mechanical properties.