Hybrid Nanocomposites of Hydroxyapatite,Eu2O3, Graphene Oxide Via Ultrasonic Power: Microstructure,Morphology Design and Antibacterial for Biomedical Applications

Post-implantation infections are regarded as a major issue in the biomedical field. Further, many investigations are continuous towards developing antibacterial biocompatible materials. In this regard, hydroxyapatite (HAP), erbium oxide (Eu₂O₃), and graphene oxide (GO) were introduced in nanocomposites combinations, including single, dual, and triple constituents. The nanoparticles of HAP, Eu₂O₃, and nanosheets of GO are synthesized separately, while dispersed in the nanocomposites simultaneously. The morphological investigation showed that HAP was configured in a rod-like shape while the nano ellipsoidal shape of Eu₂O₃ was confirmed. The particle size of the ternary nanocomposite containing HAP/Eu₂O₃/GO reached the length of 40 nm for the rods of HAP and around 28 nm for the length axis of ellipsoidal Eu₂O₃ nanoparticles. The roughness average increased to be about 54.7 nm for HAP/GO and decreased to 37.9 nm for the ternary nanocomposite. Furthermore, the maximum valley depth (R_v) increased from HAP to the ternary nanocomposite from 188.9 to 189.8 nm. Moreover, the antibacterial activity was measured, whereas the inhibition zone of HAP/Eu₂O₃/GO reached 13.2?±?1.1 mm for Escherichia coli and 11.4?±?0.8 mm for Staphylococcus aureus. The cell viability of the human osteoblast cell lines was evaluated to be 98.5?±?3% for the ternary composition from 96.8?±?4% for the pure HAP. The existence of antibacterial activity without showing cytotoxicity against mammalian cells indicates the compatibility of nanocomposites with biomedical applications.

     

Nanoarchitectonics of Hydroxyapatite/Molybdenum Trioxide/Graphene Oxide Composite for Efficient Antibacterial Activity

Nanocomposites based on hydroxyapatite (HAP), including MoO₃, HAP/MoO₃, HAP/GO and HAP/MoO₃/GO have been studied to be suggested for biological usage. The different compositions were investigated using FTIR, XRD, EDS, and XPS analysis. The tight relation between morphological features and composites' chemical ingredients was also studied. According to TEM micrographs, it was mentioned that the disappearance of well-defined grains after the combinations of HAP and MoO₃, while graphene oxide (GO) caused a reduction in size and maintaining the particles’ shape. The combination between HAP/MoO₃ declines the roughness of both HAP and MoO₃ individually, recording 27.5 nm, while HAP/GO and HAP/MoO3/GO exhibit in-between roughness average (Ra) value among its raw constituents with 34.7 and 33.5 nm, respectively. Furthermore, SEM micrographs and roughness results show how to tailing the proper features for the proposed application by changing the type and amount of additives into HAP. Thus, the composite (HAP/MoO₃/GO) displays the uppermost cell viability compared with the rest compositions with 97.8?±?3.0%. Additionally, this triple composite hits the peak germicidal behavior with 17.9?±?1.2 and 16.5?±?0.9 mm against both E.coli and S.aureus, respectively.

     

Optimizing Graphene Oxide Encapsulated TiO2 and Hydroxyapatite; Structure and Biological Response

Nanocomposites based on hydroxyapatite (HAP) are fabricated with/without combining titanium oxide (TiO₂) and graphene oxide. Structure investigation was done for all compositions using X-ray diffraction (XRD), Fourier-transform infrared in addition to X-ray photoelectron to study the chemical compositions of the obtained nanocomposites. The surface morphology investigation was done with the scanning electron microscope and transmission electron microscope. In this regard, TiO₂ nanoparticles were exhibited in spherical shapes, while HAP was detected as nanorods. The dimensions of HAP have been decreased from 53 and 18 to 27 and 10 nm for length and diameter, respectively. The crystallite sizes obtained from XRD data are around 15 and 33 nm for HAP and TiO₂ respectively. Moreover, the diameter of TiO₂ reached 80 nm. Further, the average roughness parameter (R_a) improved from 9.2 to 11.1 nm from HAP to TNC. Besides, the root mean square (R_q), maximum height of the roughness (R_t), and maximum roughness valley depth (R_v) increased to 14.7, 104, and 55.9 nm, respectively. Furthermore, cell viability enhanced from 96.3?±?3 to 102.4?±?3%. Besides, the antibacterial behavior improved to be 15.3?±?1.3 and 14.2?±?0.9 mm for TNC against E. coli and S. aureus respectively.

     

Ternary hydroxyapatite/chitosan/graphene oxide composite coating on AZ91D magnesium alloy by electrophoretic deposition

In this work, ternary HA/chitosan/graphene oxide (GO) coating was applied via electrophoretic deposition on AZ91D magnesium alloy as bone implants, successfully. Subsequently, phase composition, surface morphology, hardness, corrosion behavior, bioactivity and antibacterial of the composite coatings were studied. Hardness and Young's modulus of the composite coatings increased from 40 ± 1.5 MPa and 3.1 ± 0.42 GPa to 60 ± 3.12 MPa and 8 ± 0.53 GPa for composite coatings with 0 and 2 wt% GO, respectively. The results of the SBF solution soaking of the composites after 24 days, indicated the improvement of HA growth due to the increasing of the GO addition in composite coating. New HA grains with leaf-like morphology grew uniformly at higher amounts of GO (1 and 2 %wt) in a perfectly balanced composition. Rate of the substrate corrosion significantly decreased from 4.3 to 0.2 (mpy), when the amount of GO increased from 0 to 2 wt% due to reduction of the surface cracks at the presence of the GO reinforcement. Also, there was no Escherichia coli and Staphylococcus aureus bacteria growth in broth medium after 24 h and OD₆₀₀ results at 24 h post inoculation for the 2%wt GO addition in coating.     

Experimental Phase Diagram Determination and Thermodynamic Assessment of the CeO2‐Gd2O3‐CoO System

New phase diagram data and a thermodynamic assessment of the CeO‐Gd₂O₃‐CoO system using the CALPHAD approach are presented. This information is needed to understand the surprisingly low sintering temperature (950°C–1050°C) of CeO₂‐based materials doped with small amounts of transition metal oxide (e.g., CoO). Experimental phase equilibria between 1100°C and 1300°C are reported based on the analysis of annealed and molten samples. No isolated compound exists in the ternary. At 1300°C the Co solubility in the ternary compounds Ce_1?x?yGd_xCo_yO_2?x/2?y (fluorite) is 2.7 mol% and is less than 1 mol% in the Gd_2?xCe_xO_3+x/2 (bixbyite). The Ce solubility in the perovskite GdCoO_3?δ was found to be 1 mol%. The lowest temperature eutectic melt in the ternary has a composition of 57.2 mol% Co and 41.1 mol% Gd melting at an onset temperature of 1303 ± 5°C, which is close to the binary eutectic in the Gd₂O₃‐CoO system at 60 ± 2 mol% Co and 1348 ± 1°C.     

Microstructure and mechanical properties of α/β-Si3N4 composite ceramics with novel ternary additives prepared via spark plasma sintering

In this study, α/β-Si₃N₄ composite ceramics with high hardness and toughness were fabricated by adopting two different novel ternary additives, ZrN–AlN–Al₂O₃/Y₂O₃, and spark plasma sintering at 1550 °C under 40 MPa. The phase composition, microstructure, grain distribution, crack propagation process and mechanical properties of sintered bulk were investigated. Results demonstrated that the sintered α/β-Si₃N₄ composite ceramics with ZrN–AlN–Al₂O₃ contained the most α phase, which resulted in a maximum Vickers hardness of 18.41 ± 0.31 GPa. In the α/β-Si₃N₄ composite ceramics with ZrN–AlN–Y₂O₃ additives, Zr₃AlN MAX-phase and ZrO phase were found and their formation mechanisms were explained. The fracture appearance presented coarser elongated β-Si₃N₄ grains and denser microstructure when 20 wt% TiC particles were mixed into Si₃N₄ matrix, meanwhile, exhibited maximum mean grain diameter of 0.98 ± 0.24 μm. As a result, the compact α/β-Si₃N₄ composite ceramics containing ZrN–AlN–Y₂O₃ additives and TiC particles displayed the optimal bending strength and fracture toughness of 822.63 ± 28.75 MPa and 8.53 ± 0.21 MPa?m^1/2, respectively. Moreover, the synergistic toughening of rod-like β-Si₃N₄ grains and TiC reinforced particles revealed the beneficial effect on the enhanced fracture toughness of Si₃N₄ ceramic matrix.     

High quality factor microwave dielectric ceramics in the (Mg1/3Nb2/3)O2–ZrO2–TiO2 ternary system

Novel high quality factor microwave dielectric ceramics (1?x)ZrTiO₄?x(Mg_1/3Nb_2/3)TiO₄ (0.325≤x≤0.4) and (ZrTi)_1?y(Mg_1/3Nb_2/3)_yO₄ (0.2≤y≤0.5) with the addition of 0.5 wt% MnCO₃ in the (Mg_1/3Nb_2/3)O₂–ZrO₂–TiO₂ ternary system were prepared, using solid‐state reaction method. The relationship between the structure and microwave dielectric properties of the ceramics was studied. The XRD patterns of the sintered samples reveal the main phase belonged to α‐PbO₂‐type structure. Raman spectroscopy and infrared reflectivity (IR) spectra were employed to evaluate phonon modes of ceramics. The 0.65ZrTiO₄?0.35(Mg_1/3Nb_2/3)TiO₄?0.5 wt% MnCO₃ ceramic can be well densified at 1240°C for 2 hours and exhibits good microwave dielectric properties with a relative permittivity (ε_r) of 42.5, a quality factor (Q×f) value of 43 520 GHz (at 5.9 Ghz) and temperature coefficient of resonant frequency (τ_f) value of ?5ppm/°C. Furthermore, the (ZrTi)_0.7(Mg_1/3Nb_2/3)_0.3O₄?0.5 wt% MnCO₃ ceramic sintered at 1260°C for 2 hours possesses a ε_r of 31.8, a Q×f value of 35 640 GHz (at 6.3 GHz) and a near zero τ_f value of ?5.9 ppm/°C. The results demonstrated that the (Mg_1/3Nb_2/3)O₂–ZrO₂–TiO₂ ternary system with excellent properties was a promising material for microwave electronic device applications.     

Structures and Properties of Pb(Zr0.5Ti0.5)O3−Pb(Zn1/3Nb2/3)O3− Pb(Ni1/3Nb2/3)O3 Ceramics for Energy Harvesting Devices

Piezoelectric ceramics with large energy density coefficient d₃₃·g₃₃ value have been found suitable for piezoelectric energy harvesting applications. In this study, the phase structures and piezoelectric properties of xPb(Zr_0.5Ti_0.5)O₃?yPb(Zn_1/3Nb_2/3)O₃?(1?x?y)Pb(Ni_1/3Nb_2/3)O₃ (xPZT?yPZN?(1?x?y)PNN) ceramic were investigated with systematically varying PZN and PNN components. The ternary phase diagram of PZT?PZN?PNN system was illustrated and the composition region of morphotropic phase boundary (MPB) was determined. Piezoelectric and dielectric measurements verify that the materials in MPB region all present large d₃₃ and d₃₃·g₃₃ values. In particular, very high d₃₃·g₃₃ coefficients of 20162.2 × 10^?15 m²/N and 21026.3 × 10^?15 m²/N are observed from samples 0.75PZT?0.15PZN?0.1PNN and 0.8PZT?0.05PZN?0.15PNN with compositions located on the rhombohedral phase side near MPB because the dielectric coefficient ε₃₃^T/ε₀ decreases faster than the d₃₃ coefficient at this side.     

Microstructure,mechanical properties and toughening mechanisms of graphene reinforced Al2O3-WC-TiC composite ceramic tool material

The low fracture toughness of Al₂O₃-based ceramics limited their practical application in cutting tools. In this work, graphene was chosen to reinforce Al₂O₃-WC-TiC composite ceramic tool materials by hot pressing. Microstructure, mechanical properties and toughening mechanisms of the composite ceramic tool materials were investigated. The results indicated that the more refined and denser composite microstructures were obtained with the introduction of graphene. The optimal flexural strength, Vickers hardness, indentation fracture toughness were 646.31?±?20.78?MPa, 24.64?±?0.42?GPa, 9.42?±?0.40?MPa?m^1/2, respectively, at 0.5?vol% of graphene content, which were significantly improved compared to ceramic tool material without graphene. The main toughening mechanisms originated from weak interfaces induced by graphene, and rugged fractured surface, grain refinement, graphene pull-out, crack deflection, crack bridging, micro-crack and surface peeling were responsible for the increase of fracture toughness values.     

Mullite-bonded SiC-whisker-reinforced SiC matrix composites: Preparation,characterization, and toughening mechanisms

A novel mullite-bonded SiC-whisker-reinforced SiC matrix composite (SiCw/SiC, SiC whisker-to-SiC powder mass ratio of 1:9) was designed and successfully prepared. Before preparing the composite, the inexpensive lab-made SiCw was first modified by an oxidation/leaching process and then coated with Al₂O₃. The kinetics results indicate that the oxidation process can be described by improved shrinking-cylinder models. The aspect ratio of SiCw improved after modification. Subsequently, raw materials with a SiC–SiO₂–Al₂O₃ triple-layered structure were obtained after the Al₂O₃-coating process and used as feedstocks during the subsequent hot-pressing sintering. Finally, the characterization of the composites indicates that the mullite-bonded sample performs better (relative density of 93.8?±?1.4%, flexural strength of 533.3?±?18.2?MPa, fracture toughness of 13.6?±?2.1?MPa?m^1/2, and Vickers hardness of 20.6?±?2.5?GPa) than the reference sample without the mullite interface. The improved toughness could essentially be attributed to the moderately strong interface bonding and effective load transfer effects of the mullite interface.     

The effect of antimony trioxide on poly (vinyl alcohol)-lithium perchlorate based polymer electrolytes

A new type of inorganic filler antimony trioxide (Sb₂O₃) is used to prepare composite polymer electrolytes based on poly (vinyl alcohol) (PVA) and lithium perchlorate (LiClO₄) by solution casting technique. The incorporation of Sb₂O₃ enhances the ionic conductivity at ambient temperature and exhibits the highest ionic conductivity value of 9.51×10^?5 S cm^?1 upon the addition of 6 wt% Sb₂O₃. Thermogravimetric analyses (TGA) reveal that the second weight loss is reduced. This shows the improvement in thermal stability of electrolyte film upon addition of Sb₂O₃. Differential scanning calorimetry (DSC) analyses show that the glass transition temperature (T_g) value decreases with incorporation of Sb₂O₃. X-ray diffraction (XRD) studies show that the addition of Sb₂O₃ decreases the degree of crystallinity whereas scanning electron microscope (SEM) studies reveal the surface morphology of the prepared composite polymer electrolytes.     

SrCo1−xSbxO3−δ cathode materials prepared by Pechini method for solid oxide fuel cell applications

In this study, SrCo_1?ySb_yO_3?δ powders were prepared by a modified Pechini method. According to the study results, the cubic Pm3m phase of the SrCo_1?ySb_yO_3?δ ceramics was obtained as 10% of cobalt ions were substituted by antimony ions. Doping of Sb³⁺ ions appeared both to stabilize the Pm3m phase of the SrCo_1?ySb_yO_3?δ ceramics and to enhance densification and retard grain growth. The coefficient of thermal expansion of the SrCo_1?xSb_xO_3?δ ceramics increased with the content of the antimony ions, ranging from 10.17 to 15.37 ppm/°C at temperatures lower than the inflection point (ranging from 450 °C to 550 °C) and from 22.16 to 29.29 ppm/°C at higher temperatures. For the SrCo_0.98Sb_0.02O_3?δ ceramic, electrical conductivity reached a maximum of 507 S/cm at 450 °C. The ohmic and polarization resistances of the single cell with the pure SrCo_0.98Sb_0.02O_3?δ cathode at 700 °C read respectively 0.298 Ω cm² and 0.560 Ω cm². The single cell with the SrCo_0.98Sb_0.02O_3?δ-SDC composite cathode appeared to reduce the impedances with the R₀ and R_P at 700 °C reading respectively 0.109 Ω cm² and 0.127 Ω cm². Without microstructure optimization and measured at 700 °C, the single cells with the pure SrCo_0.98Sb_0.02O_3?δ cathode and the SrCo_0.98Sb_0.02O_3?δ-SDC composite cathode, demonstrated maximum power densities of 0.100 W/cm² and 0.487 W/cm². Apparently, SrCo_1?ySb_yO_3?δ is a potential cathode for use in IT-SOFCs.     

Mechanical properties of low-pressure sintered WC-6Co cemented carbide doped with graphene oxide/alumina composite particles

The mechanical properties of WC-6Co cemented carbides with different contents of graphene oxide (GO)/nanoalumina (Al₂O₃) composite particles were investigated. The results showed that some of the GO/Al₂O₃ composite particles were tightly wrapped in WC grains through boundary deformation, but some of them existed in the cobalt phase, which gradually decreased the cobalt phase lattice constant and caused different degrees of grain refinement. When the content was 0.05 wt%, the cobalt phase dissolved more W; thus, the solid solution strengthening effect was improved. In addition, the superior dispersion of the composite particles aided in particle refinement. The relative alloy density increased as the GO/Al₂O₃ composite particle content increased. The mechanical properties first increased and then decreased with increasing additive amounts. When the content was 0.05 wt%, the alloy had the best performance. The hardness was 2021 HV₃₀, the strength was 2480.4 MPa, and the toughness was 11.5 MPa?m^1/2.     

The influence of different SiC amounts on the microstructure,densification, and mechanical properties of hot-pressed Al2O3-SiC composites

The hot pressing process of monolithic Al₂O₃ and Al₂O₃-SiC composites with 0-25 wt% of submicrometer silicon carbide was done in this paper. The presence of SiC particles prohibited the grain growth of the Al₂O₃ matrix during sintering at the temperatures of 1450°C and 1550°C for 1 h and under the pressure of 30 MPa in vacuum. The effect of SiC reinforcement on the mechanical properties of composite specimens like fracture toughness, flexural strength, and hardness was discussed. The results showed that the maximum values of fracture toughness (5.9 ± 0.5 MPa.m^1/2) and hardness (20.8 ± 0.4 GPa) were obtained for the Al₂O₃-5 wt% SiC composite specimens. The significant improvement in fracture toughness of composite specimens in comparison with the monolithic alumina (3.1 ± 0.4 MPa.m^1/2) could be attributed to crack deflection as one of the toughening mechanisms with regard to the presence of SiC particles. In addition, the flexural strength was improved by increasing SiC value up to 25 wt% and reached 395 ± 1.4 MPa. The scanning electron microscopy (SEM) observations verified that the increasing of flexural strength was related to the fine-grained microstructure.     

Microwave-assisted one-pot synthesis of SnC2O4/graphene composite anode material for lithium-ion batteries

Currently, SnC₂O₄ is considered as one of the most promising anode materials for high-energy lithium-ion batteries (LIBs) because its charge capacity is higher than that of metal oxides. Herein, a facile microwave-assisted solvothermal method was employed to obtain SnC₂O₄/GO composites within only 30?min, which is time-efficient. The amount of SnC₂O₄ was increased to 95.3?wt% to improve the capacity of the composite. Pure SnC₂O₄ with a high specific surface area of 19.6?m² g^?1 without any other tin compound was used for fabrication. The SnC₂O₄/GO composite exhibited excellent electrochemical performance, with reversible discharge/charge capacity of 657/659?mA?h?g^?1 after 100 cycles at 0.2?A?g^?1. Furthermore, at high current densities of 1.0 and 2.0?A?g^?1, the SnC₂O₄/GO composite anode exhibited high reversible discharge/charge capacities of 553/552 and 418/414?mA?h?g^?1, respectively, after 200 cycles at room temperature. These improvements were likely obtained because SnC₂O₄ was well composited with graphene, which not only offered rapid electron transfer but also released the tension produced by the volumetric effect during repeated lithiation/delithiation. Cyclic voltammetry (CV) was also performed to further study the electrochemical reactions of SnC₂O₄/GO. The facile microwave-assisted solvothermal method used herein is considered as a highly efficient method to fabricate metal oxalate/graphene composites for use as anode materials in LIBs.     

Mechanical property and adhesion strength of carbon nanofillers reinforced alumina single splats using in-situ picoindentation and nanoscratch test

Current study deals with the effect of carbon nanotube (CNTs) and graphene nanoplatelets (GNPs) reinforcement on the mechanical properties and the adhesion strength of plasma sprayed alumina (Al₂O₃) single splats, using in-situ picoindentation and nanoscratch test, respectively. The hardness of the Al₂O₃ splat was measured as 18 ± 5.3 GPa which increased to 34.22 ± 8.44 GPa on 1 wt% CNTs addition and to 42.5 ± 9.06 GPa on 0.5 wt% GNPs addition. Hybrid addition of CNTs and GNPs provided the maximum hardness value of 51.25 ± 8.76 GPa to the Al₂O₃ splat. Similar trend in the elastic modulus has been reported with a minimum value for Al₂O₃ splat, i.e. 159 ± 35.40 GPa, and maximum for the Al₂O₃ splat mixed synergistically with CNTs and GNPs (269 ± 43.12 GPa). Adhesion strength of the Al₂O₃ splat (0.21 ± 0.11 MPa) also showed a nearly 5-fold increase on hybrid addition of CNTs and GNPs with a maximum value of 1.08 ± 0.38 MPa. This improvement in the properties were due to the extremely high mechanical properties of CNTs and GNPs and better melting of the splats, which not only improved the densification but also provided a better interlocking between the splat and the substrate.     

Preparation and gas-sensing performance of GO/SnO2/NiO gas-sensitive composite materials

In this study, a SnO₂/NiO composite material was prepared via a co-precipitation method. After calcination at 400 °C for 2 h, a binary composite material (SnO₂/NiO) with good crystallization was obtained. Then, a graphene oxide (GO)/SnO₂/NiO ternary composite material was prepared using a hydrothermal method, in which SnO₂/NiO performed secondary growth on the GO surface. The XRD results showed that SnO₂/NiO exhibited good crystallinity and proved the existence of a chemical bond, Sn–O–C, which was due to the formation of a chemical bond between GO and SnO₂/NiO. Lastly, GO/SnO₂/NiO was successfully prepared and coated on the surface of a gold electrode for gas sensitivity test. A good response to acetone gas in the concentration range of 10–500 ppm at 350 °C was determined. Compared with SnO₂/NiO, GO/SnO₂/NiO showed remarkable improvements in response time, recovery time, and sensitivity. At 350 °C, the sensitivity of acetone with a concentration of 50 ppm was 21.11, the response time was only 5 s, and the recovery time was 150 s. GO/SnO₂/NiO comprised two structures, chemical bond and p-n junction, which exerted a synergistic effect. GO/SnO₂/NiO indicated an excellent application prospect in acetone gas detection.     

Fine grained Al2O3/SiC composite ceramic tool material prepared by two-step microwave sintering

Fine-grained Al₂O₃/SiC composite ceramic tool materials were synthesized by two-step microwave sintering. The effects of first-step sintering temperature (T1), content and particle size of SiC on the microstructure and mechanical properties were studied. It was found that the sample with higher content of SiC was achieved with finer grains, and the incorporation of SiC particles could bridge, branch and deflect the cracks, thus improving the fracture toughness. Higher T1 was required for the densification of the samples with higher content of SiC (>5?wt%). The sample containing 3?wt% SiC particles with the mean particle size of 100?nm, which was sintered at 1600?°C (T1) and 1100?°C (T2) for 5?min had the fine microstructure and optimal properties. Its relative density, grain size, Vickers hardness and fracture toughness obtained were 98.37%, 0.78?±?0.31?μm, 18.40?±?0.24?GPa and 4.97?±?0.30?MPa?m^1/2, respectively. Compared to the sample prepared by single-step microwave sintering, although near full densification can be achieved in both two methods, the grain size was reduced by 36% and the fracture toughness was improved by 28% in two-step microwave sintering.     

Preparation of mullite from alumina/aluminum nitrate and kaolin clay through spark plasma sintering process

In the present study, the in-situ synthesized mullite has been prepared successfully by mixing kaolinite with alumina and aluminum nitrate nonahydrate (ANN) powders through high energy milling followed by spark plasma sintering (SPS). Using a high-energy ball-mill, the stoichiometric compositions of the starting powders, considering their final transformation to Al₂O₃ and SiO₂, have been mixed. The SPS process has been performed at 1400 and 1375?°C for the specimens containing Al₂O₃ and ANN, respectively. XRD patterns of the milled powders after 30?h showed the formation of quartz from kaolinite for both starting batches. The displacement-temperature-time (DTT) curves and the corresponded vacuum changes indicated the dehydration and phase transformation of ANN and kaolinite at different stages of the sintering process. The XRD patterns of the sintered samples revealed the formation of mullite alongside un-reacted Al₂O₃ and crystobalite for the batches containing Al₂O₃ and ANN, respectively. The results of the physical and mechanical properties tests showed higher amounts of bending strength (397?±?18?MPa), Vickers hardness (16.32?±?0.21?GPa) and fracture toughness (3.81?±?0.24?MPa?m^?1/2) alongside a lower porosity (0.070?±?0.02%) for the prepared sample containing Al₂O₃, than those of the sample containing ANN.     

Spark plasma sintering of multi-cation doped (Yb,Sm) α/β-SiAlON ceramic tool materials: Effects of cation type,composition, and sintering temperature

The multi-cation doped α/β-SiAlON composite ceramics tool materials were prepared via spark plasma sintering. The effects of cation type (Yb, Sm, Yb/Sm), composition, and sintering temperature on densification behavior, phase formation, microstructural evolution, and mechanical properties of α/β-SiAlON were studied. Results showed that the addition of Sm₂O₃ in Yb/Sm-SiAlON could decline the shrinkage temperature and accelerate the densification process due to the increased liquid phase volume and decreased viscosity. The Sm₂O₃ played the role of both sintering additives and stabilizing cation of α-SiAlON, which could promote the formation of α-SiAlON and the elongation of β-SiAlON, thus acquired refined α grains and large aspect ratio of β grains. The SPS-sintered multi-cation doped Yb/Sm-SiAlON with 2 wt% additional Sm₂O₃ possessed excellent comprehensive mechanical properties (3.40 g/cm³, 18.53 ± 0.18 GPa, and 6.13 ± 0.23 MPa m^1/2).