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This study focuses on conducting an ab initio evolutionary investigation to search for stable polymorphs of iron diborocarbides with the formula FeB 2 C 2. We also examined other forms of C contents, including FeB 3 C and FeBC 3. Our findings reveal that the lowest energetic structure of FeB 2 C 2 is a semimetallic monoclinic phase with a space group (s.g.) of C2/m and a metastable metallic phase of FeB 2 C 2 is an orthorhombic structure with s.g. of Pmmm. In addition, structural and relative properties of FeB 3 C and FeBC 3 are performed and discussed to compare with FeB 2 C 2. All predicted structures are dynamically and elastically stable, verified without negative phonon frequency and Born criteria, respectively. We also analyzed the energetic stability through calculated cohesive and formation energies, which showed that C2/m- FeB 2 C 2 is stable at low pressure. Interestingly, the C2/m and Pmmm phases of FeB 2 C 2 are hard materials with Vickers hardness ( H v) of 22.40 and 27.52 GPa, respectively. Additionally, we examined the electron–phonon coupling of both FeB 2 C 2 phases. Unexpectedly, we found that the semimetallic C2/m- FeB 2 C 2 phase is a superconductor with a significant superconducting temperature ( T c) exceeding 6 K. These findings provide some novel results for the Fe–B–C system and pave the way for investigating other metal borocarbides and related ternary compounds. [ABSTRACT FROM AUTHOR]

Five high entropy carbide ceramics, (Hf0.2,Nb0.2,Ta0.2,Ti0.2,Zr0.2)C, (Cr0.2,Hf0.2,Ta0.2,Ti0.2,Zr0.2)C, (Hf0.2,Mo0.2,Ta0.2,Ti0.2,Zr0.2)C, (Hf0.2,Ta0.2,Ti0.2,W0.2,Zr0.2)C, and (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C, were synthesized by carbothermal reduction of oxides and direct current sintering. The five high entropy carbide ceramics were determined to be nominally phase-pure with relative densities of more than 98.9% and mean grain sizes of less than 5 μm. Average Vickers hardness values ranged from 19.2 ± 0.4 GPa for (Hf0.2,Nb0.2,Ta0.2,Ti0.2,Zr0.2)C at a load of 2 kgf to 43.5 ± 0.4 GPa for (Hf0.2,Mo0.2,Ti0.2,W0.2,Zr0.2)C at a load of 0.05 kgf. Hardness generally increased with increasing the valence electron concentration and strain as measured by the Williamson–Hall analysis. However, neither correlation was conclusive enough to be a clear indicator of hardness. Instead, it was determined that a combination of effects that includes the valence electron concentration, lattice strain, and grain size all contribute to the hardness of high entropy carbide ceramics. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the biaxial flexural strength of zirconia materials with different translucency before and after aging procedures and to evaluate the effects of aging on hardness and surface characteristics. Materials and Methods: A total of 90 disc-shaped specimens (n = 30 each) were prepared from translucent (Upcera-ST, Upcera Dental), high translucent (Katana HT, Kuraray Noritake), and ultra high translucent (Katana UTML, Kuraray Noritake) zirconia materials to a Ø16 x 1.2 mm thickness. The different translucency discs were then divided into three subgroups; one group was subjected to aging in a chewing simulator (n = 10), one group was aged with thermocycling (n = 10), and one was a control group (n = 10). Biaxial flexural strength, Vickers hardness, and surface characteristics were examined for all discs. The data were analyzed using the Shapiro-Wilk (P = .05), Mann-Whitney U, and Kruskal-Wallis H tests. Fracture strength was determined using biaxial bending strength tests, and Weibull analysis was used to analyze the resulting data. Results: A statistically significant difference was found among zirconia materials with different translucency in terms of fracture strength. On average, fracture strength was highest in the Upcera ST group (1,932.87 MPa) and lowest in the Katana UTML group (1,073.6 MPa; P = .001). The results of Weibull analysis showed a statistically similar distribution for all groups. Conclusions: Aging procedures did not cause significant differences in fracture strength and hardness. The fracture strength of the zirconia materials with different translucency was considered acceptable for intraoral use. [ABSTRACT FROM AUTHOR]

Boron-based compounds have triggered substantial attention due to their multifunctional properties, incorporating excellent hardness and superconductivity. While tetragonal metal borides LiB4 and NaB4 with BaAl4-type structure and striking clathrate boron motif have been induced under compression, there is still a lack of deep understanding of their potential properties at ambient pressure. We herein conduct a comprehensive study on I4/mmm-structured LiB4 and NaB4 under ambient pressure via first-principles calculations. Remarkably, both LiB4 and NaB4 are found to possess high Vickers hardness of 39 GPa, which is ascribed to the robust boron framework with strong covalency. Furthermore, their high hardness values together with distinguished stability make them highly potential superhard materials. Meanwhile, electron–phonon coupling analysis reveals that both LiB4 and NaB4 are conventional phonon-mediated superconductors, with critical temperatures of 6 and 8 K at 1 atmosphere pressure (atm), respectively, mainly arising from the coupling of B 2p electronic states and the low-frequency phonon modes associated with Li-, Na-, and B-derived vibrations. This work provides valuable insights into the mechanical and superconducting behaviors of metal borides and will boost further studies of emergent borides with multiple functionalities. [ABSTRACT FROM AUTHOR]

Boron-based compounds have triggered substantial attention due to their multifunctional properties, incorporating excellent hardness and superconductivity. While tetragonal metal borides LiB4 and NaB4 with BaAl4-type structure and striking clathrate boron motif have been induced under compression, there is still a lack of deep understanding of their potential properties at ambient pressure. We herein conduct a comprehensive study on I4/mmm-structured LiB4 and NaB4 under ambient pressure via first-principles calculations. Remarkably, both LiB4 and NaB4 are found to possess high Vickers hardness of 39 GPa, which is ascribed to the robust boron framework with strong covalency. Furthermore, their high hardness values together with distinguished stability make them highly potential superhard materials. Meanwhile, electron–phonon coupling analysis reveals that both LiB4 and NaB4 are conventional phonon-mediated superconductors, with critical temperatures of 6 and 8 K at 1 atmosphere pressure (atm), respectively, mainly arising from the coupling of B 2p electronic states and the low-frequency phonon modes associated with Li-, Na-, and B-derived vibrations. This work provides valuable insights into the mechanical and superconducting behaviors of metal borides and will boost further studies of emergent borides with multiple functionalities. [ABSTRACT FROM AUTHOR]

Radioisotope thermoelectric generators (RTGs) are deal energy supply devices for deep space and deep-sea exploration, and it is also the energy core of the operation of the working equipment. Except for 238Pu (Plutonium), 241Am (Americium) was also used as a nuclide in the radioactive energy system for future space exploration missions. In this work, neodymium oxide (Nd 2 O 3) was used as analogues for Am 2 O 3. Cold-press-and-sinter methods was used. Different particle parameters (morphology, size, and crystal structure) and synthesized parameters of Nd 2 O 3 were investigated. The synthesized powders contained lath-shaped particles, and batches with different particle sizes and microscopic topography were made and sintered. The results show that the optimal precipitation temperature of Nd 2 O 3 is 25 °C. The optimal thermal decomposition temperature range is 900 °C to 1100 °C, and the optimal thermal decomposition heating rate is 10 °C min−1. The samples of Nd 2 O 3 pellets without cracking is obtained with relative density of 85%–90 %. The Vickers hardness of Nd 2 O 3 pellets was also studied. This paper provides an important scientific guiding significance for the cold-press-and-sinter of radioisotope 241Am batteries in the future. [ABSTRACT FROM AUTHOR]

The effects of carbon content on microstructure and mechanical properties of the (TiTaNbZrMo)C-Co cermets were investigated in details. Uniform high-entropy carbide powders with different carbon contents were obtained through carbothermal reduction and mixed with a Co binder phase via ball milling for fabricating cermets at the elevated temperature. The increased carbon content makes the hardness of cermets initially rose and then decreased, while the fracture toughness demonstrates an overall decline. Among all high-entropy ceramic based cermets, (TiTaNbZrMo)C 0.9 -Co cermet (C1) exhibited the optimal combination of hardness and fracture toughness properties, with a Vickers hardness (HV 30) of 15.83 GPa and a fracture toughness of 7.74 MPa m1/2. Furthermore, the presence of graphite phases accompanied by the excess carbon content could enhance the wear resistance of cermets. (Ti,Ta,Nb,Zr,Mo)C-Co high-entropy ceramic based cermets have potential applications in the fields of cutting tools and wear-resistant components. [ABSTRACT FROM AUTHOR]

NbC-Ni cermets have emerged as promising alternatives to the conventional WC-Co due to their superior hot hardness and fracture toughness. However, the recent increase in Ni and Co prices necessitates substituting these binders with economical alternatives for cermet formulations. The Fe-Ni binary alloy shows promise as a binder due to its superior mechanical properties, low cost, and reduced toxicity compared to Co and Ni. This study demonstrated the potential of Fe-Ni as a promising binder material for NbC cermets, offering a balance between cost-effectiveness and properties suitable for various high-performance applications. The NbC-Fe-Ni cermets were fabricated via vacuum Liquid Phase Sintering (LPS) at 1440 °C for 1h and compared to NbC-Ni cermets. Microstructural analysis (SEM + EDX) revealed a continuous decrease in D90 values up to NbC-35Ni-65Fe (65 wt% Fe), indicating that Fe-Ni effectively suppressed grain growth; additionally, it increased the contiguity of NbC grains. Vickers hardness tests revealed that the hardness of the cermets increased with higher Fe content in the binder, reaching a peak value of 1487 ± 15 HV 30 for NbC-35Ni-65Fe, marking a remarkable 34 % improvement over NbC-Ni. However, fracture toughness decreased marginally due to the increased contiguity of NbC grains, which reduced crack inhibition. Nanoindentation hardness tests of the binder phase revealed that partial substitution of Ni with Fe enhanced binder hardness, contributing to the overall improvement in NbC-Fe-Ni cermets' hardness values. A 3-point bend test demonstrated a maximum strength of 649 ± 16 MPa for NbC-35Ni-65Fe cermet, indicating a 19 % improvement over NbC-Ni cermet. These findings highlight Fe-Ni's potential as a cost-effective binder for NbC cermets, suitable for high-performance applications. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of nanostructured composite powders (WC-Ni), nickel binder content, and sintering techniques on the morphology and mechanical properties of tungsten carbide. An alternative low-temperature gas-solid reaction route with a short reaction time was employed to produce nanostructured composite powders with 5 and 15 wt% Ni. The powders were consolidated using spark plasma sintering (SPS) and conventional vacuum furnace sintering at temperatures of 1350 °C and 1450 °C. The composite powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and particle size measurements. The expansion/contraction of the compacted nanocomposite powders was studied through dilatometric analysis. The composite powders exhibited a uniform distribution of Ni, in both compositions. For the WC-5 wt% Ni nanocomposite powders, the average crystallite sizes for WC and Ni were 41.6 nm and 46.2 nm, respectively. While, for the WC-15 wt% Ni nanocomposite, the crystallite sizes for WC and Ni were 45.6 and 38.4 nm. The sintered composites were evaluated through XRD, SEM, measurements of density and Vickers hardness. The enhanced sinterability of the nanostructured powders enabled their consolidation into (WC-Ni) hard metal with densities approaching the theoretical relative density of 96.07 %, even with low binder content (5 wt% Ni). This is attributed to the uniform distribution of Ni and an extensive Ni-WC interface present prior to sintering. The SPS process at 1350 °C produced sintered bodies (WC-5 wt% Ni and WC-15 wt% Ni) with higher Vickers hardness (2322 HV and 1512 HV, respectively) and superior microstructural quality compared to samples produced by conventional vacuum furnace techniques. These results demonstrated that the mechanical properties of the system WC-Ni processed by SPS are superior to those obtained by vacuum furnace. Therefore, WC-Ni hard metals processed by this approach is a promising alternative to conventional hard metals (WC-Co) for a wide range of applications. [Display omitted] • Impact of the preparation technique on the characteristics of WC-Ni composite powders. • WC-Ni nanocomposite prepared by gas-solid reaction at low temperature and short reaction time. • WC-Ni composites with relative density of 97.67 % and Vickers hardness of 2322 HV. [ABSTRACT FROM AUTHOR]

This paper studied the densification, phase composition, microstructure and properties of polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulks prepared by SPS. The dense specimen (98.9 % in relative density) with the average grain size of 15.46 μm has been determined to be a CsCl-type single-phase substitutional solid solution without any impurities or other secondary phases. The homogenous elemental distributions of La, Ce and Pr have been confirmed by both microscale and nanoscale. The room temperature (RT) Vickers hardness (H v), indentation fracture toughness (K IC) and flexure strength of the dense specimen have been measured to be 23.0 GPa, 2.04 MPa m1/2 and 305.1 MPa, respectively. The Berkovich hardness (H B) and elastic modulus (E) of the dense specimen have been measured to be 30.0 GPa and 376.0 GPa, respectively, by nanoindentation tests at a maximum load of 40 mN. In comparison with the polycrystalline LaB 6 bulk, the lower work function Φ of 2.64 eV evaluated by UPS and the larger thermionic emission current densities measured at the same operating condition suggest that the polycrystalline La 0.6 Ce 0.3 Pr 0.1 B 6 bulk is a superior-performance thermionic cathode material. [ABSTRACT FROM AUTHOR]

Binary aluminosilicate glasses containing 20–50 wt% Al 2 O 3 were successfully densified through a cold sintering process (CSP) using 1–10 M NaOH solutions. The investigation focused on densification and structural unit changes in the cold-sintered binary aluminosilicate glasses. Specifically, the binary aluminosilicate glass with 40 wt% Al 2 O 3 , cold-sintered at 180 °C using 1–10 M NaOH solutions, achieved a relative density of up to 90 % at 10 M NaOH. This was attributed to an enhanced dissolution-precipitation process facilitated by an increased concentration of the NaOH solution. In aluminosilicate glasses with 20–50 wt% Al 2 O 3 , the relative densities approached 90 % after CSP at 180 °C using a 10 M NaOH solution. Al(OH) 3 formation in the cold-sintered glasses was confirmed, particularly at higher concentrations of NaOH solution (>10 M) and higher contents of Al 2 O 3 (>40 wt%). Changes in Si structural units were observed during CSP, with Al-rich Si units becoming dominant as the concentration of the NaOH solution increased. The higher substitution of Si-O-Si bonds by Si-O-Al bonds led to the precipitation of Al(OH) 3 , as well as an increased Vickers hardness and biaxial flexural strength of the cold-sintered glasses. These findings demonstrate that the Al 2 O 3 content and NaOH concentration play important roles in the densification and enhancement of the mechanical property in the cold-sintered alumina-rich binary aluminosilicate glasses and offer insights into the optimal conditions for obtaining desirable aluminosilicate materials through CSP. [ABSTRACT FROM AUTHOR]

A novel α/β SiC-(Ti, Nb)B 2 toughened (Ti, Nb)C-based composites was fabricated by reactive hot pressing with TiC, NbB 2 and Si powders at 1500 °C and 1600 °C, respectively. The influence of NbB 2 , Si content, and sintering temperature on the microstructure and mechanical properties of the composite was investigated. The intermediate product NbC reacts with Si to form NbSi 2 and β-SiC phases. With addition of 10 mol% NbB 2 , a toughening phase α-SiC was formed. During the reaction process, insufficient diffusion of Nb atoms in TiC leads to the formation of a specific "core-shell" microstructure, which improves the flexural strength of the composite ceramics. The (Ti, Nb)C has a specific crystallographic orientation relationship with NbSi 2 and α-SiC. The high-density stacking faults and ordered structures in β-SiC crystals enhances its hardness. The rod-shaped α-SiC and plate-like (Ti, Nb)B 2 by in situ reactions effectively improve the fracture toughness of the composites. TiC-32 mol% Si-10 mol% NbB 2 (raw powder composition) sintered at 1600 °C has excellent comprehensive mechanical properties, with fracture toughness, flexural strength, and Vickers hardness of 5.45 MPa·m1/2, 665 MPa, and 22 GPa, respectively, which provide a new insight into the optimization strength and toughness of TiC-based composites. In addition, under high temperature oxidation of 1000∼1200 °C, the 30NB (54 mol% TiC-16 mol% Si-30 mol% NbB 2) sample has better high-temperature oxidation resistance than the 30ZB (54 mol% TiC-16 mol% Si-30 mol% ZrB 2) sample. [ABSTRACT FROM AUTHOR]

Monazite ceramic is one of the potential waste forms to incorporate actinides in planned nuclear waste repositories. Inspired by recent progress on the low-temperature sintering and enriching radionuclides by wet-chemistry, the sintering processes of monazite ceramic with/without pre-sintering are investigated by spark plasma sintering and pressureless sintering using La 0.8 Sr 0.1 Th 0.1 PO 4 ·nH 2 O rhabdophane as raw materials. Some specific issues such as the behavior of dissociation, structural evolution, and physicochemical properties affected by SPS and PLS are discussed in detail. The results reveal that a low-temperature appears to be a prevailing factor for SPS under 40 MPa with a suggested 1050 °C for 15 min process to prepare La 0.8 Sr 0.1 Th 0.1 PO 4 monazite ceramic without forming Th(PO 3) 4 phase, and the relative density and Vickers hardness of ceramic are more than 98 % and 600 (HV10). The dissolution experiment based on the ASTM-1220 method indicates that La 0.8 Sr 0.1 Th 0.1 PO 4 monazite ceramics is a typical example of an incongruent reaction, associated with Sr2+ is more likely to be dissolved out form monazite lattice compared with Th4+ and La3+. [ABSTRACT FROM AUTHOR]

The complex thermal-mechanical coupling among Ti(C, N)-based cermet tool, workpiece and chip affects immensely the tool life, machining quality and costs during high-speed cutting, which makes the investigation on wear mechanisms of tools quite important. In this work, submicron and ultrafine Ti(C, N)-based cermet tools were prepared by vacuum sintering technology, and the cutting performance of the tools was evaluated by continuous dry cutting. The aim of this work is to unravel the wear mechanisms of submicron and ultrafine Ti(C, N)-based cermet tools based on the cutting performance and wear characteristics of both the cutting tools and chips generated during high-speed cutting. The Vickers hardness, flexural strength and tool lifespan of ultrafine Ti(C, N)-based cermets are significantly superior to those of submicron Ti(C, N)-based cermets because of grain refinement strengthening and the improved distribution of metal phases. Tool wear depends to a large extent upon the contact states and heat transfer ability at different locations of the tool edge, which are characterized by simultaneous action and mutual transition from abrasive, adhesion, surface fatigue and oxidative wear. Overall, ultrafine Ti(C, N)-based cermet tools with excellent comprehensive properties exhibit a distinctly reduced tool wear at different wear regions. [ABSTRACT FROM AUTHOR]

The synthesis of forsterite can be challenging because the initial oxides react slowly and undesirable compounds like enstatite (MgSiO 3) can form instead of forsterite (Mg 2 SiO 4). Although several methods have been developed to overcome these challenges, the synthesis of forsterite using the solid-state reaction of nanopowders has not been investigated. This study aims to explore the possibility of producing forsterite by reacting MgO and SiO 2 nano-powder. The initial oxides were wet ball milled, dried, and reaction sintered. Spectroscopy and microscopy methods were used to analyze the formed phases and study the formation kinetics. The density, coefficient of thermal expansion (CTE), and hardness of sintered samples were measured using a densimeter, a dilatometer, and a hardness tester, respectively. The results demonstrated that it is possible to synthesize forsterite by solid state reaction of pure MgO and SiO 2 nano-powders. The reaction between the two compounds begins at a temperature as low as 860 °C and leads to the formation of forsterite by a two-step formation mechanism. The first reaction involves the reaction of MgO and SiO 2 to form enstatite, and the second one produces forsterite as a result of enstatite reacting further with MgO. The activation energy values ranged from 1028.89 to 1105.655 kJ/mol for the formation of forsterite, and from 456.316 to 488.08 kJ/mol for the formation of enstatite. Monolithic forsterite was completely formed at a low temperature of 1200 °C for a relatively short duration of 2 h. The sample sintered at 1400 °C for 2 h, had a density of 2.96 g/cm3, a Vickers hardness of 7.64 GPa, and a coefficient of thermal expansion of 10.24 × 10−6/K measured in the temperature range of 200–1300 °C. [ABSTRACT FROM AUTHOR]

In this work, SiC–AlN–TiB 2 –VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 °C-2100 °C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y 2 O 3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al 2 O 3 (on the surface of AlN) and Y 2 O 3 , which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB 2 , and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB 2 , and between TiB 2 and VC. Al 5 C 3 N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B 2 O 3 on the surface of TiB 2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 °C, SiC multiphase ceramics with added Y 2 O 3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa. [ABSTRACT FROM AUTHOR]

High fracture toughness and low erosion wear play key roles in improving the working reliability and service life of erosion-resistant ZTA ceramic parts (ZTA-CPs). To reconcile the hardness, fracture toughness and erosion wear resistance, the Y 2 O 3 content of ZTA-ceramics with 20 wt% ZrO 2 (Z20TA) was successfully controlled by adjusting the mass ratio of commercially available m -ZrO 2 and 3Y–ZrO 2 powders in the initial compositions in this paper. Significantly, the fracture toughness and Vickers hardness of Z20TA bulk ceramics with different Y 2 O 3 content can reach up to 5.35 MPa m1/2 and 15.82 GPa, and the erosion wear volume can be reduced to as low as 0.019 cm3, higher than those of Z20TA-ceramic parts by 5∼22 %, 12–19 % and 24–47 %, respectively. This novel Y 2 O 3 content adjustment method is feasible for the industrial level mass production of anti-erosion wear high-performance ZTA parts, promoting the industrial development and wider application of erosion-resistant ceramic parts. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP) technology shows promise in addressing the challenges of preparing high-strength, precise, and complex SiC ceramic structural parts. However, the low strength of DLP-printed SiC ceramic parts remains a persistent issue. To address this, a nano-ZrO 2 particle enhancement strategy is proposed. This study systematically investigates the effects of ZrO 2 content on slurry viscosity, curing depth, microscopic morphology, and the mechanical properties of SiC ceramics. The results indicate that increasing the ZrO 2 content raises the viscosity of the SiC slurry and decreases the curing depth, which can adversely affect the printing quality of SiC ceramic green bodies. However, a higher ZrO 2 content significantly reduces pore defects in the sintered parts, improving densification and mechanical properties. This underscores the importance of optimizing ZrO 2 content. The SiC sintered parts reinforced with ZrO 2 particles exhibited outstanding properties, including a relative density of 91.1 ± 3.2 %, Vickers hardness of 996.4 ± 93.8 HV, and a flexural strength of 201.5 ± 11.4 MPa. This study provides a straightforward and effective method for producing high-strength SiC ceramics via DLP. [ABSTRACT FROM AUTHOR]

MgO-Al 2 O 3 -SiO 2 -ZnO-TiO 2 -ZrO 2 glass with the addition of 8 mol% Na 2 O as flux has been prepared by the melt-casting method, and transparent glass-ceramics (GCs) with spinel (MgAl 2 O 4 and ZnAl 2 O 4) as the main crystalline phases were prepared by controlled crystallization. The optimum nucleation temperature was determined through DSC method, which is conducted on the glass with different preheating temperatures. The type and size of crystals in MAS glass-ceramics are highly dependent on the heat treatment. As the nucleation time increased to over 25 h, the formation of spinel was hindered due to the increasing formation of Na 2 TiSiO 5 in the glass, which consumed most of the Ti4+ ions during the long-term nucleation. When the nucleation time is up to 35 h, there is only Na 2 TiSiO 5 crystalline phase in the GCs. The nucleation time have a significant effect on the ion-exchange process through changing the crystals type and microstructure of GC. Both the Na + ions in Na 2 TiSiO 5 crystals and glassy phase can participate ion-exchange with K+ ions in molten salts, facilitating to form compressive stress. While, the formation of spinel consumed a lot of [AlO 4 ] in glassy phase, which decreasing the ion-exchange channel and thus hindering the ion-exchange. When heat treated at 700 °C/25 h + 830 °C/1 h, the MAS glass-ceramic showed transparency over 78 % at 550 nm, and its Vickers hardness reached ∼845 kgf/mm2 after ion-exchange. [ABSTRACT FROM AUTHOR]

SiC whiskers (SiC w)-reinforced α/β-SiAlON ceramic tool materials were synthesized via spark plasma sintering (SPS). A comprehensive study was conducted on densification mechanism, phase composition, microstructure, mechanical properties, and wear resistance of the SiC w /α/β-SiAlON composites. The results indicated that SiC w constrained the densification process and impeded the growth of SiAlON grains, and the introduction of SiC w significantly enhanced mechanical properties of the α/β-SiAlON ceramic. The composite containing 28 wt% SiC w synthesized at 1700 °C showed well mechanical properties, with a density of 3.35 g/cm³, Vickers hardness of 19.38 ± 0.33 GPa, and fracture toughness of 7.35 ± 0.27 MPa m1/2.The principal toughening mechanisms of SiC w /α/β-SiAlON included crack deflection, branching, bridging, as well as transgranular fracture and whisker pullout. The addition of SiC w improved the wear resistance of α/β-SiAlON ceramic. Compared to those without whiskers, the wear volume and wear rate were decreased by 38.8 %. [ABSTRACT FROM AUTHOR]

Residual stresses and anisotropic structures characterize laser powder bed fusion (L-PBF) products due to rapid thermal changes during fabrication, potentially leading to microcracking and lower strength. Post-heat treatments are crucial for enhancing mechanical properties. Numerous dental technology laboratories worldwide are adopting the new technologies but must invest considerable time and resources to refine them for specific requirements. Our research can assist researchers in identifying thermal processes that enhance the mechanical properties of dental Co-Cr alloys. In this study, high cooling rates (quenching) and annealing after quenching were evaluated for L-PBF Co-Cr dental alloys. Cast samples (standard manufacturing method) were tested as a second reference material. Tensile strength, Vickers hardness, microstructure characterization, and phase identification were performed. Significant differences were found among the L-PBF groups and the cast samples. The lowest tensile strength (707 MPa) and hardness (345 HV) were observed for cast Starbond COS. The highest mechanical properties (1389 MPa, 535 HV) were observed for the samples subjected to the water quenching and reheating methods. XRD analysis revealed that the face-centered cubic (FCC) and hexagonal close-packed (HCP) phases are influenced by the composition and heat treatment. Annealing after quenching improved the microstructure homogeneity and increased the HCP content. L-PBF techniques yielded superior mechanical properties compared to traditional casting methods, offering efficiency and precision. Future research should focus on fatigue properties. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is an ultrafast sintering method for the preparation of ceramics and ceramic composites with simple geometrical shapes, with the combined application of uniaxial pressure. This study aims to propose an SPS densification method for Si3N4 ceramic balls without necessitating alterations to tools and equipment. The Si3N4 ceramic balls intended for sintering are positioned within a SiC powder bed inside the conventional die used in SPS. The study systematically investigates the effects of presintering temperature (1400°C, 1500°C, and 1600°C) and SPS temperature (1600°C, 1700°C, and 1800°C) on the sphericity, relative density, phase composition, microstructure, and mechanical properties of Si3N4 ceramic balls. Experimental findings reveal that Si3N4 ceramic balls exhibiting an optimal combination of sphericity (0.94 ± 0.02), relative density (98.4%), and mechanical properties (Vickers hardness: 17.5 ± 0.4 GPa, fracture toughness: 6.4 ± 0.1 MPa·m1/2) were successfully achieved at a pre‐sintering temperature and SPS temperature of 1600°C, coupled with the use of a SiC powder bed and SPS method. Consequently, the SPS method demonstrates its capability to fabricate Si3N4 ceramic balls with excellent performance. [ABSTRACT FROM AUTHOR]

LaB6–HfB2 composites with the different HfB2 contents (10 wt.%, 30 wt.%, 50 wt.%, 70 wt.%, and 90 wt.%) were densified by spark plasma sintering (SPS). Results showed that the densification mechanism of the composite transformed from the grain boundary diffusion into the dislocation climbing mechanism as the holding time was extended from 0 to 15 min under temperature range of 1750–1900°C. The HfB2 phase could effectively limit the grain growth of LaB6 phase, and the dynamic growth of the grain was governed by grain boundary diffusion. Both the Berkovich hardness and Vickers hardness obeyed the normal indentation size effect. LaB6–70 wt.% HfB2 composite had the highest fracture toughness of 3.98 ±.43 MPa m.5, whereas the highest current density of 18.34 A/cm2 belonged to LaB6–30 wt.% HfB2 composite. All the results demonstrated that LaB6–HfB2 composite was a promising material with the excellent structural and functional performance. [ABSTRACT FROM AUTHOR]

Liquid‐phase laser irradiation technology was utilized to synthesize graphene‐coated tungsten carbide (WC@G) core–shell composite materials with regular spherical morphology. Characterization via scanning electron microscopy, transmission electron microscopy (TEM), X‐ray diffraction, and Raman spectroscopy revealed the evolution of WC particle microstructure from sharp edges to regular spherical shapes post‐laser irradiation. High‐resolution TEM displayed a tightly knit core–shell structure. Raman spectroscopy confirmed graphene presence through D, G, and 2D peaks. Incorporation of WC@G into a titanium diboride matrix, followed by discharge plasma sintering, yielded TiB2/WC@G composite ceramic materials. Compared to TiB2/WC/G composite ceramic materials, the WC@G core–shell structure significantly enhanced sintering performance. Optimal mechanical properties were achieved with 6 wt.% WC@G, exhibiting a relative density of 99.6%, Vickers hardness of 18.5 GPa, flexural strength of 696.9 MPa, and fracture toughness of 8.5 MPa m1/2. Characterization identified graphene detachment, pull‐out, and fracture deflection as key mechanisms enhancing toughness in TiB2/WC@G composite ceramic materials. [ABSTRACT FROM AUTHOR]

To confer light‐blocking properties upon the Al2O3 encapsulation material, this study employed a one‐step method using α‐Al2O3 as the main raw material to synthesize CaCu3Ti4O12(CCTO)–MnO2–Co2O3 series black Al2O3 ceramics. The research investigated their coloring effect, sintering behavior, dielectric, and mechanical properties. The results indicate that the CCTO–MnO2–Co2O3 series colorants successfully dyed the Al2O3 ceramics black, while their introduction resulted in the formation of various spinel‐type compounds and facilitated the sintering of Al2O3 ceramics. The sintering mechanism and performance effects of black Al2O3 ceramics were thoroughly investigated, revealing that with an increase in the colorant content, all properties of the samples improved. When the colorant content reached 15.0 wt.%, the coloring effect reached its optimum, with a relative density of 96.7%, a dielectric constant of 12.5, a dielectric loss of.0081, a flexural strength of 314.4 MPa, and a Vickers hardness of 1254.5 Hv. [ABSTRACT FROM AUTHOR]

Dysprosium (Dy)‐doped (Y1−xDyx)3Si2C2 (x = 0, 0.1, 0.3, 0.5) solid solution ceramics were successfully fabricated using an in situ reaction spark plasma sintering technology, for the first time. The effect of various Dy doping contents (x) on the microstructure, mechanical, and thermal properties of (Y1−xDyx)3Si2C2 ceramics was investigated. The (0 2 0) crystal plane spacing of (Y0.5Dy0.5)3Si2C2 was 7.813 Å, which was smaller than that of Y3Si2C2, due to the fact that the atomic radius of Dy is smaller than that of Y. The Dy doping facilitated the consolidation of (Y1−xDyx)3Si2C2, thus a highly dense (Y0.5Dy0.5)3Si2C2 ceramic material with a low open porosity of 0.14% was successfully obtained at a relatively low temperature of 1 200°C. As the content of Dy doping (x) increased from 0 to 0.5, the purity of (Y1−xDyx)3Si2C2 ceramics increased from 88.3 to 90.7 wt.%, while the grain size of (Y1−xDyx)3Si2C2 ceramics decreased from 0.59 to 0.46 µm. As a result, the Vickers hardness and thermal conductivity of the (Y0.5Dy0.5)3Si2C2 material was 7.1 GPa and 9.8 W·m−1·K−1, respectively. [ABSTRACT FROM AUTHOR]

The effect of LaB6 on the densification and microstructure of pressure‐less sintered 0.4B4C–0.4SiC–0.2ZrB2 ternary ceramic with eutectic composition was investigated. The Vickers hardness, bending strength, and fracture toughness of the quaternary ceramic were discussed based on the microstructural characteristics. The densification of the 0.4B4C–0.4SiC–0.2ZrB2 ceramic was enhanced with increasing LaB6 content from 0 to 70 mol% (the proportion to B4C–SiC–ZrB2). When the LaB6 content was 50 mol%, the densification rate of the composite ceramic reached a peak. The 0.27B4C–0.27SiC–0.13ZrB2–0.33LaB6 quaternary composite ceramic has reached a density of over 95% after being sintered at 2 100°C for 1 h. The B4C and SiC phases had refined grains of 1–3 µm with intragranular structures in the as‐sintered ceramics. The hardness and strength reached 17.9 ±.8 GPa and 307 ± 38 MPa, respectively. Crack deflection and branching were ascribed to the improved fracture toughness of 3.78 ±.26 MPa·m1/2. This study provides new ideas for fabricating dense non‐oxide ceramic composites with enhanced properties. [ABSTRACT FROM AUTHOR]

Recently multielements solid solution has shown significant improvement to the mechanical properties of parent MAX phases. Therefore, in this work, five elements with different radii were incorporated to check the effect on properties of MAX phases. (Nb0.8Ti0.05Zr0.05Mo0.05Hf0.05)4AlC3 (MAXHf) and (Nb0.8Ti0.05Zr0.05Mo0.05Ta0.05)4AlC3 (MAXTa) ceramics were successfully synthesized using the spark plasma sintering technique. The microstructure and elemental map analysis results further confirmed that the five transition metals were successfully solid soluted at the M‐sites of the hexagonal M4AlC3 unit cell. The mean elemental compositions for M‐site elements were achieved as Nb0.85Ti0.052Zr0.035Mo0.027Hf0.036 and Nb0.847Ti0.051Zr0.043Mo0.025Ta0.033 for MAXHf and MAXTa ceramics, respectively. The electrical and thermal conductivities of multielement solid solution MAX phases were decreased compared to pure Nb4AlC3. However, Mechanical properties were significantly increased with the solid solution of five transition metals. The fracture toughness, flexural strength, compressive strength and Vickers hardness (10 N) of MAXHf and MAXTa ceramics were achieved as 8.87 MPa m1/2, 448 MPa, 867 MPa, 6.5 GPa and 10.36 MPa m1/2, 557 MPa, 1039 MPa, 8.2 GPa, respectively. The enhanced mechanical properties suggest the effectiveness of the solid solution strengthening effect and provide new opportunities to further tailor the mechanical properties of the MAX phase ceramics. [ABSTRACT FROM AUTHOR]

In this study, TiB 2 –TiC, TiB 2 –TiC-GNP, and TiB 2 -TiC-BN composites were produced via spark plasma sintering (SPS). The densification and sintering behavior, phase and Raman spectroscopy analyses, microstructural properties, Vickers microhardness, and wear behavior of the binary and ternary composites were investigated. The addition of various amounts of TiC to TiB 2 resulted in nearly complete densification. The TiB 2 –TiC-GNP specimens exhibited a relative density of more than 99 %; in contrast, the addition of BN did not contribute to the densification. The Vickers hardness of the GNP-added composites was ∼25 GPa, whereas hBN addition to the matrix decreased the hardness to ∼22 GPa (∼9 % decrease). According to the wear test, the addition of GNPs did not result in a significant change in the TiB 2 –TiC matrix; however, the addition of hBN increased the specific wear rate of the matrix by ∼100 %. The GNPs did not have a negative effect on the densification, microstructural, or mechanical properties, such as the Vickers hardness and wear resistance. Hence, they were determined to be a more suitable sintering aid for matrix composition than hBN. [ABSTRACT FROM AUTHOR]

Inorganic oxide ceramics are essential for microwave applications due to their stable structure and exceptional performance. LiZnMgGaTi 2 O 8 ceramics were prepared using the solid-phase method. XRD and TEM confirmed that the ceramics possess spinel structures. The ceramics had a maximum relative density of 94.57 % and a Vickers hardness of 8.58 GPa when sintered at 1220 °C. The ionic polarizability of Ti4+ in the ceramics exceeds the Shannon value, leading to a 20.3 % deviation between ε th and ε r. The activation energy of the impedance spectrum fitting is 1.302 eV, indicating a low concentration of oxygen vacancies in the ceramic. Hence, the Q × f value of the ceramics is primarily influenced by relative density. The optimal microwave dielectric properties of LiZnMgGaTi 2 O 8 ceramics are ε r = 15.68, Q × f = 66,620 GHz, and τ f = −30.9 ppm/°C. The test curves of ε r and dielectric loss remain nearly parallel to the x-axis from −80 °C to 80 °C, demonstrating the excellent stability of LiZnMgGaTi 2 O 8 ceramics. [ABSTRACT FROM AUTHOR]

Recycling of metals is becoming crucial from an economic and environmental point of view. The solid-state recycling process Continuous Friction Stir Extrusion was used to produce wires out of A356-T6 chips. The mechanical properties of the produced wires were explored by varying the main process parameters. Characterization involved Vickers hardness tests, tensile tests, grain size measurements, and fracture surface analysis. It has been found that it is possible to achieve 77 % of the Ultimate Tensile Strength (UTS) and 92 % of Vickers hardness with respect to the as-fabricated A356 alloy. The average grain size increases with the tool rotational with values ranging from about 9 µm to about 11 µm. A 3D dedicated numerical model was used to predict the distributions and histories of primary field variables, and to calculate the Piwnik-Plata parameter, fostering a more in-depth understanding of the process mechanics. This allows for the precise prediction of unacceptable product quality of the bonding when the Plata and Piwnik parameters are low. Predicted temperature close to the rotating tool should reach 400 °C while the cochlea temperature should be below 100 °C for sound wires production thus avoiding early chip bonding and process failure. [ABSTRACT FROM AUTHOR]

The effect of Cr additions ON the coarsening of β′(NiAl) precipitates in (Fe,Cr)‐α matrix is studied using Fe–10%Ni–15%Al–15%Cr (FAN15Cr) and Fe–10%Ni–15%Al–22%Cr (FAN22Cr) alloys. Specimens are homogenized and subsequently aged at 850, 900, and 950 °C for different periods of time. The characterization is carried out with conventional and high‐resolution scanning electron microscopy, transmission electron microscopy, and Vickers hardness tests. Results indicate that the addition of Cr leads to an increase in the activation energy and the coarsening kinetics at high temperatures. The precipitate morphology during aging evolves from spheres with a random distribution, followed by cuboids aligned in preferential orientations and the formation of clusters. As aging progresses further, the morphology changes to semirounded precipitates with a polyhedral surface as revealed by the etching process. Transmission electron microscopy results reveal the formation of a dislocation network indicating a state of semicoherency in the precipitate–matrix interface. The activation energy for the coarsening process is determined from the coarsening kinetic constants. While the activation energy for the coarsening in FANCr15 is close to similar alloys, the value for FAN22Cr is unusually high and probably related to the dislocation networks observed. [ABSTRACT FROM AUTHOR]

The electrolytic cell is the main equipment for electrolytic aluminum production. The visual electrolytic cell can observe and study the production process and mechanism of aluminum electrolysis. The effects of Y2O3 addition and sample thickness on the densification behavior and transmittance of Magnesium-aluminate spinel (MAS) were studied. The relative density, porosity, phase composition, microstructure, Vickers hardness, and transmittance of the sintered samples were characterized using the Archimedes method, x-ray diffraction analysis, scanning electron microscopy, Vickers hardness tester, and UV-visible near-infrared diffuse reflection. The results show that the appropriate amount of Y2O3 can enhance the transmittance of MgAl2O4 and the optimum Y2O3 content is 2 wt.%. At this time, the relative density of Magnesium-aluminate spinel (MAS), the maximum hardness, and the maximum transmittance are 96.19%, 18.18 GPa, and 36.3%, respectively. Under the optimum conditions, when the mass of the sample is 0.2 g, the relative density and maximum hardness of the Magnesium-aluminate spinel (MAS) sample are 97.28% and 18.18 GPa, respectively. Although the transmittance is not the highest, it is only lower than the transmittance of 0.15 g sample. The optimum sintering additive content and sample thickness jointly promote the densification, hardness, and transmittance of Magnesium-aluminate spinel (MAS). [ABSTRACT FROM AUTHOR]

Currently in steel enterprises, the mass and heat of hot blast furnace slag (BFS) are not fully recovered, and the produced chrome-containing sludge (CCS) poses a significant threat to the ecological environment. In this work, CCS together with other ingredients is added into hot BFS to produce high value-added glass-ceramic (GC), after the mixed molten slag is cooled down. The obtained GC shows excellent physical and chemical properties (bulk density: 2.76 g cm−3, water absorption: 0.059 %, compressive strength: 78 MPa, Vickers hardness: 7.54 GPa, acid resistance: 98.63 %, alkali resistance: 99.84 %, thermal conductivity: 1.049 W m−1 °C−1, and thermal expansivity: 6.56 × 10−6 m m−1 °C−1). These excellent physical and chemical properties render the as-prepared GC a high value-added building material. In addition, the leaching concentrations of total Cr element and Cr(VI) in the as-prepared GC are 1.6 mg L−1 and 1.03 mg L−1, respectively, which are below the standard threshold for hazardous waste extraction toxicity. Compared with the traditional sintering method, the sensible heat of the hot BFS can be used as the thermal source in the molten slag cooling method, which can save a lot of energy. The use of hot BFS and CCS to produce high value-added GC not only fully utilizes the mass and heat of hot BFS but also fixes the Cr element in the CCS within the crystalline phase of GC, thereby eliminating the pollution of CCS to the environment. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to achieve low-temperature densification of SiC ceramic, β-SiC nanopowder was doped with Li 2 O together with Y 2 O 3 –Al 2 O 3 –MgO as sintering aids, and then spark plasma sintered at temperatures ranging from 1450 °C to 1600 °C for 30 min under 30 MPa pressure in argon. The densities, microstructures and mechanical properties of SiC ceramics were systematically investigated, in comparison to the counterparts sintered with Y 2 O 3 –Al 2 O 3 –MgO additives. Since Li 2 O has a low melting point, Li 2 O addition effectively decreased the formation temperature of liquid secondary phase, enabling SiC ceramics to obtain higher density and lower porosity after low-temperature sintering (T ≤ 1550 °C). Besides, Li 2 O addition was found to decrease the viscosity of liquid phase and enhance grain growth of SiC through dissolution-reprecipitation process. When sintered at 1550 °C, Li 2 O addition led to a remarkable increase of density from 3.03 g/cm3 to 3.21 g/cm3 for SiC ceramic. Meanwhile, the SiC ceramic with Li 2 O addition exhibited a high Vickers hardness of 22.75 ± 0.35 GPa and a good fracture toughness of 3.83 ± 0.27 MPa m1/2. The research results are expected to benefit the low-cost fabrication of SiC ceramics based on pressure-assisted sintering and alleviate the thermal damage of SiC fiber in hot-pressed SiC f /SiC composites. [ABSTRACT FROM AUTHOR]

Al 2 O 3 -based ceramic tool materials synergistically reinforced by SiC whiskers (SiC w) and SiC particles (SiC p) were prepared via spark plasma sintering (SPS) technique. The densification behavior, sintering kinetics and optimal ratios of SiC w and SiC p on Al 2 O 3 -based ceramic tool materials were investigated. Results indicated that densification mainly occurred from 1200 to 1450 °C. Grain boundary sliding or grain boundary diffusion was the primary cause of densification at 1200–1350 °C. Whereas, dislocation climbing was the main densification mechanism at 1400–1450 °C. W25P5 sintered at 1450 °C had a large relative density, small grain size and the best mechanical properties with the fracture toughness of 7.35 ± 0.19 MPa m1/2, Vickers hardness of 21.79 ± 0.21 GPa, and relative density of 98.86 ± 0.15 %. The synergistic toughening mechanisms included crack deflection, whisker bridging and whisker pull-out. [ABSTRACT FROM AUTHOR]

Background: Glass ionomer cements with extended setting time and inferior mechanical properties present significant challenges for dentists in clinical practice. Thus, various alterations aimed to enhance their properties. Aim of the study: To study the effect of adding TiO2 and SiO2 nanoparticles on properties of conventional glass ionomer cement. Methods: 2.5 wt% TiO2 and 2.5 wt% SiO2 were added to the glass ionomer cement (GC Gold Label Luting & Lining Cement, Japan). Microhardness, compressive strength, setting time and color changes were evaluated using Vickers hardness tester, Universal testing machine, Gillmore needle apparatus and spectrophotometer, respectively. Results: Data were analyzed using SPSS 18. Mean, SD, and confidence intervals were reported. Normality was checked using Kolmogorov–Smirnov test. The experimental group revealed a higher hardness value than the control group. Meanwhile, Compressive strength results revealed a higher value of the control group than experimental group. Setting time was longer for the experimental group, in the meantime no perceptible color change for the experimental group was recorded. Conclusions: Adding 2.5 wt% TiO2 and 2.5 wt% SiO2 to conventional glass ionomer had a positive effect on microhardness without affecting the perceptible color. [ABSTRACT FROM AUTHOR]

In the present work, WB2–SiC composite powders containing 20 vol.% of SiC were in situ synthesized by the boro/carbothermal reduction with WO3, SiO2, B4C, and carbon black as raw materials at 1400°C, 1500°C, and 1600°C, respectively. The as‐synthesized composite powders were then consolidated by spark plasma sintering (SPS) technique to obtain WB2–SiC composite bulk samples. The experimental results showed that the relative density of the WB2–SiC composite ceramic samples achieved in this study was higher than 97.5%. Also, electronic microscopy observations showed that SiO2 had reacted completely during the preparation process, and the SiC grains were homogenously embedded among the WB2 grains with the formation of a three‐dimensional structure. The Vickers hardness and fracture toughness values of the composite ceramic fabricated by powder heat treated at 1400°C were 24.6 ± 0.7 GPa and 5.4 ± 0.7 MPa·m1/2, respectively, which were the highest among three samples prepared in this study. [ABSTRACT FROM AUTHOR]

Information on the sintering activation energy is currently focused on evaluation of single-phase ceramic systems. This work shows the results of high-temperature dilatometry measurements of layered and particle composites based on alumina and zirconia. Layered composites with different layer thickness ratios and particle composites with variable composition in the entire concentration range were prepared by electrophoretic deposition allowing manufacturing composites with precious design and strongly bonded interfaces. The phenomena observed during the high-temperature dilatometry measurements are discussed, and the data were used to calculate the sintering activation energies of composites using the modified Master Sintering Curve concept. By covering a wide range of composite designs, it was possible to determine differences in activation energies and to show their dependence on the direction in the case of laminate composites given by the directionally dependent sintering behaviour. Sintering activation energies of layered composites were always higher than for monoliths due to constrained sintering showing maximum sintering activation energies at lower volumes of zirconia in the layers for longitudinal and transversal orientation of the samples. A similar trend was identified in particle composites due to slowed down alumina densification by the pinning effect. Additionally, mechanical properties represented by Vickers hardness and indentation elastic modulus were related to the microstructure developed during sintering. The effects of interconnectivity of phases present in the composites together with other parameters of the microstructure were described. [ABSTRACT FROM AUTHOR]

Overcoming the hardness‐toughness trade‐off in diamonds attracts much interest in physics, chemistry, materials science, and engineering. Recently synthesized nanotwinned diamond composite exhibits massive enhancement in fracture toughness without sacrificing its unprecedented Vickers hardness [Y. Yue et al., Nature 582, 370 (2020)]. Several mechanisms for the toughness enhancement are unveiled based on the edge‐cracked models while the mechanism from Vickers indentation has remained elusive. Here, the energy of nanotwinned diamonds, diamond polytypes, and diamond composites is systematically investigated from Vickers indentation simulation. The results show diamond structures dissipate energy by interface migration, accompanied by the phase transformation from diamond polytypes to the cubic diamond (3C diamond). By tuning the density and distribution of interfaces, the dissipated energy of the diamond is increased to more than twice that of a single‐crystal 3C diamond. This work complements the established mechanisms and provides a universal strategy for toughening diamonds and related materials. [ABSTRACT FROM AUTHOR]

Transparent glass–ceramics (GCs) with excellent mechanical properties is a growing demand in the field of optoelectronic devices. In this work, Mg2SiO4 nanocrystals embedded transparent GCs were prepared using the melt‐quenching method. The effects of the TiO2 content on the structural and crystallization properties of glass were examined, and the influence of Mg2SiO4 crystallization on the depth of layer (DOL) for K–Na ion‐exchange was also investigated. The introduction of TiO2 was advantageous for the enhanced bulk crystallization of Mg2SiO4 nanocrystals within the glass matrix. With an increase in the TiO2 content, the size of Mg2SiO4 nanocrystals decreased, leading to an improvement in the transmittance of the GCs. Crystallization of Mg2SiO4 nanocrystals promoted the increase in Vickers hardness and ion‐exchange DOL obviously, and the Vickers hardness can further be improved by ion‐exchange. Ion‐exchange resulted in the transformation of NaAlSiO4 into KAlSiO4. Results reported here are valuable for the design and preparation of GCs with excellent mechanical and ion‐exchange properties. [ABSTRACT FROM AUTHOR]

Aluminum‒magnesium alloys are widely used in the shipbuilding and railcar industries because of their high specific strength and corrosion resistance. However, the welding of aluminum–magnesium alloys to steel poses a number of significant issues, mainly due to the formation of brittle intermetallic compounds (IMCs) and adiabatic shear bands (ASBs). The effects of IMCs on the mechanical properties of joints have been well researched, but there is a limited understanding of how ASBs and magnesium affect these properties. In this work, the effects of ASBs and Mg2Al3 on the mechanical properties of explosive-welded bimetals are studied. Optical microscopy, electron microscopy, confocal laser scanning microscopy, and electron backscatter diffraction (EBSD) were performed. Additionally, Vickers hardness tests, tear strength tests, and bending tests were carried out to determine the mechanical properties of the specimens. The results of the study revealed that at the weld interface after explosive welding, a zone of fine dark-etching Mg2Al3 phase accumulation up to 10 µm thick and an ASB zone up to 400 µm thick formed. The thickness and included volume of both zones increase from 3 to 20 vol.% with increasing detonation velocity. The tear strength also increases (from 80 to 230 MPa). After heat treatment at 200 °C for 1 h, the specimens survived at twice the bending angle, indicating good plastic properties. Thus, the results help elucidate the influence of Mg2Al3 and ASBs on the properties of bimetals with AlMg6 alloys obtained via explosive welding. [ABSTRACT FROM AUTHOR]

The effect of SiC content (10 vol%, 20 vol% and 30 vol%) and sintering temperature (1800 °C, 1900 °C and 2000 °C) on the microstructure and mechanical properties of high entropy boride-silicon carbide (HEB-SiC) composites were systematically investigated in this work. The densification was gradually increased with the increase of SiC content and sintering temperature. More specially, the densification of HEB-30 vol% SiC composite obtained at 2000 °C was as high as 99.1 %. As for the mechanical properties, the dense HEB-30S-2000 composite possessed the highest fracture toughness (5.24 MPa m1/2) and Vickers hardness (28.5 GPa). The above significantly enhanced fracture toughness was closely pertained to the fracture modes adjusting. In details, after the addition of SiC, the branching and bridging of crack, the rupture of large SiC grain, and the deflection of crack existing near the HBE matrix and SiC particles jointly promote the improvement of fracture toughness. Besides, the Vickers hardness increased linearly with the relative density increasing. A simplified equation was established, which could effectually reflect the linear connection between the Vicker hardness and relative density (SiC content) of HEB-SiC composites. It will certainly play an important guiding role in the further development of HEB-SiC composites. [ABSTRACT FROM AUTHOR]

In this paper, we propose an effective method for doping WC into Ta-Hf-C ceramics to significantly enhance their densification and mechanical properties. An increasing WC doping amount from 0 to 20 at.%, enhances the densification of Ta-Hf-C ceramics from 92.4 % to 99.1 %. This is mainly due to the fact that the doping of WC effectively removes the harmful oxygen impurities from the ceramics, thereby increasing their sintering activity. Furthermore, the doping of WC plays an active role in the mechanical properties of the ceramics. The Ta-Hf-C doped with 15 at.% WC has the highest value of 36.41 GPa for nano-hardness due to the solid solution strengthening mechanism, while the highest Vickers hardness (38.75 GPa) and fracture toughness (3.76 MPa m1/2) appear in Ta-Hf-C doped with 20 at.% WC. The main toughness mechanism is W segregation at the grain boundary, enhancing grain boundary strength. [ABSTRACT FROM AUTHOR]

The presence of α casing in beta titanium can be detrimental to various forming applications and can be eliminated through chemical milling. The effect of the chemical milling process on the removal of alpha casing from the surface of beta titanium has been investigated extensively. Chemical milling is performed at different solution concentration ratios, and the specimens are characterized using Vickers hardness and surface roughness. The optimum results for chemical milling with a high material removal rate of 3.85 mm3/min are obtained with HF (10%) and HNO3 (10%). The effect of chemical milling on the mechanical strength of beta titanium is studied through tensile tests at room temperature and at increased temperature (200 °C). The maximum percentage of elongation obtained after chemical milling is around 24.4%, compared to 1.7% observed with the as-received specimen. Comprehensive analysis through optical microscopy, XRD, and EBSD confirmed the successful removal of the α casing from the β-Ti alloy at both 0.7- and 0.5-mm chemical milling depths. The effectiveness of the chemical milling process is further investigated through fractography analysis of the tensile-tested specimens. Chemical milling with the specified solution proves to be an effective method for enhancing α casing removal and mechanical performance of β-Ti alloys, making it a promising technique for various industrial applications. [ABSTRACT FROM AUTHOR]

Based upon the Al-Cu-Mn system, aluminum hypoeutectic heat resistant aluminum alloy of the Al4Cu2Mn0.5Ca0.2Zr (wt. %) (P2) composition is developed, synthesized, and studied. An effect of increasing thermal stability is achieved due to nanosize dispersed intermetallics Al20Cu2Mn3 and Al3Zr, and also with addition of eutectic-forming elements, whose role is played by calcium. It is established that reserves of alloying an aluminum matrix within piston silumin is almost exhausted by the limit of silicon, copper and manganese solubility within aluminum solid solution. In order to substantiate the piston silumin P1 chemical composition a calculation is made for the phase composition of the Al-Si-Cu-Mg-Ni-Fe-Mn system by means of Thrmoclac software. Welded alloy microstructure is studied by means of electron microscopy (SEM) and X-ray microanalysis (XRMA). Vickers hardness of the alloy proposed P2 and equivalent piston silumin P1 is compared in the original condition and after annealing at 250 and 400 °C with a step of 50 °C, as a result of which alloy P2 developed retains more effectively hardness on heating, than for alloy P1, being potentially more heat resistant. [ABSTRACT FROM AUTHOR]

This study investigates the impact of cooling rate and alloy composition on phase formations and properties of (CoCrCuTi)100−xFex (x = 0, 5, 10, 12.5, 15) high-entropy alloys (HEAs). Samples were synthesized using arc-melting and electromagnetic levitation, followed by quenching through the use of a Cu chill or V-shaped Cu mold. Cooling rates were evaluated by measuring dendrite arm spacings (DASs), employing the relation DAS = k ɛ−n, where constants k = 16 and n = ½. Without Fe addition, a microstructure consisting of BCC1 + BCC2 phases formed, along with an interdendritic (ID) FCC Cu-rich phase. However, with the addition of 5–10% Fe, a Cu-lean C14 Laves phase emerged, accompanied by a Cu-rich ID FCC phase. For cooling rates below 75 K/s, alloys containing 10% Fe exhibited liquid phase separation (LPS), characterized by globular Cu-rich structures within the Cu-lean liquid. In contrast, for the same composition, higher cooling rates of 400–700 K/s promoted a dendritic/interdendritic microstructure. Alloys with 12.5–15 at. % Fe displayed LPS irrespective of the cooling rate, although an increase in uniformity was noted at rates exceeding 700 K/s. Vickers hardness and fracture toughness generally increased with Fe content, with hardness ranging from 444 to 891 HV. The highest fracture toughness (5.5 ± 0.4 KIC) and hardness (891 ± 66 HV) were achieved in samples containing 15 at. % Fe, cooled at rates of 25–75 K/s. [ABSTRACT FROM AUTHOR]

The article presents the results of an experimental study of the strength properties of samples obtained by laser melting from powder compositions of a lunar regolith simulant based on gabbro-diabase. The powder compositions have been obtained by sieving with a fraction range of 50–100 and 100–140 μm from a simulant with a grain-size distribution similar to that of natural regolith. Their properties have been studied on experimental samples with characteristic dimensions of 7.5 × 5 × 6 mm3: apparent density, hardness, and compressive strength in different melting modes. Dependences of these properties on the energy density were obtained in the range from 12 to 25 J/mm3. The measured Vickers hardness of samples fused from a composition of 50–100 μm had a range of 691–830 HV, and samples from a composition of 100–140 μm had a wider range: 330–830 HV. The maximum values of compressive strength for samples from both compositions reached 17–20 MPa with median values of 12 and 17 MPa for the first and second compositions, respectively. These values are quite consistent with those that could be obtained by the process of in situ resource utilization. [ABSTRACT FROM AUTHOR]

Aiming at the issues of small critical size and low glass forming ability of Fe-based amorphous alloys, this work focuses on solving the problem of preparing both large size and excellent properties. The highly dense FeCrMoBC bulk metallic glasses with diameter of 20 mm were prepared by spark plasma sintering, and the key role of heat treatment on the microstructure and properties of Fe-based bulk metallic glasses was investigated. The microstructure of Fe-based bulk metallic glasses was adjusted by annealing treatment, and the effects of annealing on the hardness and wear resistance of Fe-based bulk metallic glasses were studied. The results show that annealing induces partial crystallization of the alloy to construct in-situ amorphous nanocrystalline composites. After annealing at 650 °C for 1 h, Fe-based bulk metallic glasses precipitated Cr23C6 and B6Fe23 hard nanocrystalline phases. The highest Vickers hardness, highest fracture toughness, lowest friction coefficient, wear volume and wear rate were obtained, with values of 1514.68Hv, 2.81 MPa·m1/2,0.59, 4.72 × 10− 3mm3 and 2.62 × 10− 6mm3·N− 1·m− 1, respectively. Abrasive wear is the main form of wear, and the wear resistance is superior to that of GCr15. FeCrMoBC bulk metallic glasses exhibit outstanding hardness and wear resistance, providing new material options for the manufacture of high-performance advanced equipment. [ABSTRACT FROM AUTHOR]

This paper outlines the TIG welding process without using active flux for 4 mm-thick plates of duplex stainless steel (DSS 2205) and austenitic stainless steel (SS 304L). It also provides the properties and behavior analysis of weldments. Complete penetration is achieved with multi-pass welding. The microstructure is examined using an optical microscope (OM) and a scanning electron microscope (SEM). It was used to report on the differences between the unpolished zone and the heat-affected zone (HAZ) in weldments. A Vickers hardness tester (HV scale 10) was used to assess the weldment's hardness. Tensile and bend failure were among the mechanical properties exhibited by the parent metals of DSS2205, SS304L, and dissimilar junctions. The findings demonstrated shallow gaps in the surface area and a greater ultimate tensile strength of 600 MPa for DSS similar welding. However, compared to other similar weldments, dissimilar weldments exhibit superior performance in bending conditions. [ABSTRACT FROM AUTHOR]