TiB2 Ceramics Research Articles

Effect of Ti–Al content on the microstructure and mechanical properties of B6.5AlC–TiB2 ceramics fabricated via reactive hot pressing

In this study, different amounts of Ti–Al were introduced into the B6.5C(B4C+B) matrix, and their effects on the structure and properties of the composites were investigated. The phases and interface compositions were regulated by changing the compositions of the composites. For a Ti–Al content of 3 wt%, the B6.5AlC–TiB2 composite exhibited the best mechanical properties while maintaining a low density of 2.51 g/cm3. The Vickers hardness, fracture toughness, and bending strength were 36.3 ± 0.45 GPa, 4.75 ± 0.33 MPa·m1/2, and 470 ± 18 MPa, respectively, which increased by 24, 85, and 183% compared with pure B4C. The effect of the solution of B and Al atoms on the crystal structure of B4C led to the formation of nanotwins and stacking faults, and the resulting compressive stress was conducive for improving the mechanical properties. Further, the mismatch of the thermal expansion coefficient between the B4C matrix and TiB2 reinforcement induced crack deflection, crack branching, and crack bridging toughening mechanisms.

The comparison of densification mechanisms and microstructure evolution among TiB2 ceramics sintered under different levels of high pressure

TiB2 shows significant advantages in high-tech industry but it is hard to fulfill densification. High pressure sintering is an effective method to obtain TiB2 ceramics. This study reports the sintering condition of TiB2 ceramics under different levels of high pressure from 150 MPa to 15 GPa. The results show that the densification temperature reduced with the applied pressure. The densification mechanism of TiB2 ceramics sintered under 150 MPa during the final holding time at 1900℃ was dominated by the mixture of dislocation motion and grain boundary sliding. When the applied pressure achieves at 1.5 GPa, the densification mechanism was transformed into the plastic deformation of grains and grain boundary diffusion, a number of small angle grain boundaries, dislocation cells, substructures and straight grain boundaries were observed. Finally, the densification mechanism was transformed into plastic deformation of grains and grain boundary while the driving force increased to 15 GPa. The dislocation and substructures density increased with pressure, leading to the grain refinement. Our study compared the densification and microstructure evolution of TiB2 ceramics sintered under high pressure, proving the high pressure sintering could regulate the microstructure and refine grains.

Structural-Phase State and Mechanical Properties of a Laser Cladding Titanium Matrix Composite Based on Ti64 Alloy and TiB2 Ceramics

Structural-Phase State and Mechanical Properties of a Laser Cladding Titanium Matrix Composite Based on Ti64 Alloy and TiB2 Ceramics

TiB2 effects on the AlMgB14–TiB2 ceramics structure and properties

This paper studied titanium diboride (TiB2) effects on the structure and properties of AlMgB14 ceramics. AlMgB14–TiB2 samples with 30 wt% and 50 wt% TiB2 were obtained by the self-propagating high-temperature synthesis. The addition of 30 wt% TiB2 did not significantly change the phase composition of the AlMgB14 ceramics, which remained comparable with the initial powder mixture composition. However, increasing the TiB2 amount to 50 wt% resulted in the MgAl2O4 spinel phase appearance. The addition of TiB2 significantly increased the microhardness of AlMgB14 from 7 GPa to 19.9 GPa, compared to the initial material, and also increased its flexural strength to 314 MPa.

Core-rim microstructure formation and mechanical properties of TiB2 ceramics with TiC, B4C, Co, and Mo sintering aids

This research investigates titanium diboride (TiB2) ceramics, renowned for their exceptional properties: high hardness, chemical inertness, and thermal stability. The challenge lies in achieving dense structures through pressureless sintering, given TiB2 ceramics' high melting point and low self-diffusion coefficient. To address this, a combined method of liquid phase and reactive sintering is employed, focusing on the influence of metallic cobalt (Co) and molybdenum (Mo) as sintering aids to enhance microstructural and mechanical properties. Vacuum sintering at 1900 °C facilitates the reaction between TiC and B4C, forming TiB2, with Co improving wettability and Mo inhibiting high-temperature grain growth. The matrix of 90TiB2+10(TiC + B4C + Co + Mo) recipe achieved 94.7 % relative density and a hardness of 31.97 GPa. Moreover, adding polyvinyl butyral (PVB) assists in creating gas evacuation channels during the sintering process. The research also reveals the reaction between TiC and B4C, forming (TiMoB)C with molybdenum, while the eutectic Co–Mo alloy dissolves into borides, promoting densification and forms dense core-rim structures.

Effect of particle size and sintering additive on densification and mechanical properties of titanium diboride (TIB2) ceramic

This research paper investigates the impact of particle size on the densification and mechanical properties of TiB2 ceramics. The study compares the behavior of as-received TiB2 powder with a particle size of 6.5 ± 3.5 μm to ball-milled TiB2 powder with a particle size of 1.1 ± 0.6 μm. The addition of a B4C sintering additive was employed to enhance densification. The results reveal that full densification was not achieved with the as-received powder, even with the addition of the B4C sintering additive. However, the ball-milled powder demonstrated complete densification. The microstructure analysis of the fully dense TiB2 ceramic showed a core-shell type structure with the shell composed of (Ti, W)B2 and the core composed of TiB2, as observed through compositional analysis. However, electron backscattered diffraction analysis did not differentiate between the core and shell regions. Furthermore, the fully dense TiB2 ceramic exhibited exceptional mechanical properties. It demonstrated a high hardness value of 30 GPa, and a fracture toughness of 5.7 MPa m1/2.

In-situ synthesized phases during the spark plasma sintering of g-C3N4 added TiB2 ceramics: A thermodynamic approach

In this study, in situ composite was manufactured by using TiB2 matrix and C3N4 additive through spark plasma sintering. The optimum SPS parameters were considered and the process was carried out at a temperature of 1900°C for 7 minutes by applying an external pressure of 40 MPa. The thermodynamics of possible reactions during the process were investigated. The products of the chemical reactions were identified. The complementary XRD investigations, the EDAX analysis and SEM microscopy were used to confirm the in-situ formation of new phases. The results showed that the used carbon nitride was decomposed into its constituents, i.e. carbon and nitrogen, and the BN phase has been formed as a result of chemical reactions.

In-situ synchrotron x-ray diffraction and thermal expansion of TiB2 up to ∼3050 °C

There is an increasing interest in understanding the performance and properties of ultra-high temperature ceramics due to their high melting points (<3000 °C) that make them promising for extreme environment applications. In-situ high temperature X-ray diffraction experiments were performed on TiB2 beads up to ∼3050 °C. For these experiments, TiB2 powders were fabricated into spherical beads via gel casting methods and densified in a high temperature graphite furnace. These sample beads were then levitated in a conical nozzle levitator with reducing atmosphere (3% H2 -Ar) while being heated using a 400 W CO2 laser. During levitation a collimated synchrotron X-ray source was used to perform in-situ, temperature-dependent structural characterizations. The anisotropic coefficients of thermal expansion of TiB2 were characterized as a function of temperature up to ∼3050 °C. Elucidation of these properties are critical for the advancement of TiB2 ceramics and other transition metal di-borides for use in high temperature applications such as hypersonic platforms, nuclear reactors, and atmospheric re-entry.

STRUCTURAL-PHASE STATE AND MECHANICAL PROPERTIES OF A TITANIUM MATRIX COMPOSITE BASED ON TI64 ALLOY AND TIB2 CERAMICS OBTAINED BY LASER CLADDING

The paper presents experimental studies on the synthesis of a titanium matrix composite based on Ti64 titanium alloy and TiB2 ceramic particles by laser surface cladding. The weight percentage of TiB2 ceramics in the composite was 5, 10, and 15%. The phase composition of the resulting materials was analyzed by standard X-ray diffraction and synchrotron X-ray diffraction. It was found that the structure of the titanium matrix composite with 5 wt % ceramics consists of TiB nanowhiskers, and that of samples with higher ceramics content exhibits TiB whiskers with a width of several micrometers. The addition of TiB2 ceramics leads to an increase in Young’s modulus and nano-/microhardness of composite samples compared to Ti64 alloy. The indentation method was used to study the formation of a phase that does not correspond to TiB2 ceramics and microscale TiB whiskers and has elastic properties exceeding the elastic properties of the original Ti64 matrix phase. Analytical predictions showed an increase in the effective elastic properties of the formed heterogeneous material with the predicted new phase. It was also found that a lower friction coefficient can be achieved by forming a structure with nanowhiskers, while higher Young’s modulus and microhardness can be obtained by forming a structure with microwhiskers.

Comparison of the effects of MoSi2 and CrSi2 on sintering and properties of titanium diboride (TiB2)

Titanium diboride (TiB2) is a typical material classified as structural ceramics. However, sintering of TiB2 ceramics is difficult mainly because of a significant fraction of covalent bonds in the structure. In order to obtain dense TiB2 ceramics various additives are used to improve its sinterability. In this study, we investigated effects of MoSi2 and CrSi2 additions on sintering and properties of TiB2 prepared by hot-pressing technique. The sintered materials were characterized in terms of apparent density and microstructure. Their mechanical properties (bending strength, Vickers hardness and fracture toughness) and oxidation resistance were determined. It was found that the obtained composites are characterized by high density and microstructure characteristic for cermets (TiB2-MoSi2). The activators used for sintering did not deteriorate mechanical properties of TiB2 sintered bodies. The oxidation resistance of the polycrystals with chromium silicide addition reaches 1400?C. Based on the carried-out studies, CrSi2 was found to be a promising sintering additive.

The Electrochemical and Microstructure Effects of TiB2 and SiC Addition to AA5052/Al2O3 Surface Composite Coatings in 0.5 M H2SO4 Solution

In this work, Al2O3, SiC, and TiB2 ceramic coatings with different formulations were produced on the surface of AA5052 matrix by gas tungsten arc welding (GTAW). The corrosion behavior of the composites and the base metal (BM) was evaluated in a solution of 0.5 M H2SO4 with electrochemical techniques such as open circuit potential (OCP) monitoring, potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The morphology of the cladded surfaces was monitored by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). Based on the PDP and EIS results, BM had the lowest corrosion rate in the 0.5 M H2SO4 solution. All composite coatings shifted to higher corrosion rate values than that of BM, indicating that AA5052 composites had lower corrosion resistance compared to the BM. SEM images of the corroded surface of BM exhibit minimum pitting corrosion in sulfuric acid media. According to electrochemical studies, AA5052/Al2O3 + SiC + TiB2 composite had the lowest corrosion resistance due to the formation of micro-galvanic sites on the aluminum matrix surface. However, the AA5052/Al2O3 + TiB2 composite showed the best corrosion performance compared to other composites. In general, by adding SiC and TiB2 ceramics to Al2O3 and fabricating binary composites, the corrosion resistance of AA5052/Al2O3 composite is improved. Although the corrosion resistance of AA5052 composites is lower than the BM, their higher surface hardness makes their use justified in applications where high mechanical properties are required if the environment is not too aggressive.Graphical Abstract

Effect of TiB2 particles on microstructure and mechanical properties of B4C–TiB2 ceramics prepared by hot pressing

B4C-20 wt% TiB2 ceramics were fabricated by hot pressing B4C and ball-milled TiB2 powder mixtures. The effects of the TiB2 particle size on the microstructure and mechanical properties were investigated. The results showed that the TiB2 particle size played an important role in the mechanical properties of the B4C–TiB2 ceramics. In addition, SiO2 introduced by ball milling was beneficial for densification but detrimental to the mechanical properties of the B4C–TiB2 ceramics. The typical values of relative density, hardness, flexural strength, and fracture toughness of the ceramics were 99.20%, 35.22 GPa, 765 MPa, and 7.69 MPa m1/2, respectively. The toughening mechanisms of the B4C–TiB2 ceramics were explained by crack deflection and crack branching. In this study, the effects of high pressure and temperature caused liquefying SiO2 to migrate to the surface of B4C–TiB2 and react with diffused carbon source in the graphite foil to form a 30 μm thick SiC layered structure, which improved the high-temperature oxidation resistance of the material. The unique SiC layered structure overcame the insufficient oxidation resistance of B4C and TiB2, thereby improving the oxidation resistance of the ceramics under high-temperature service conditions.

Low-temperature densification of high entropy diboride based composites with fine grains and excellent mechanical properties

High entropy diborides require high temperature (>2000 °C) for densification, leading to grain coarsening and deteriorated mechanical properties. Herein, fully dense and fine-grained (Hf, Zr, Ta, Nb, Ti)B2 ceramics were successfully fabricated by spark plasma sintering at 1500 °C using metallic cobalt as additives. The result showed that the relative density of (Hf, Zr, Ta, Nb, Ti)B2 increased tremendously from 49.3% to 99.5% as 5 vol% cobalt (HEB5C-15) were introduced. The Co–B based liquid phase was reactively formed during sintering, accelerating the densification by wetting grain boundaries and resulting the presence of Co segregation. Due to the significantly reduced sintering temperature, sluggish diffusion characteristic of the high entropy matrix and the segregation drag effect, the resulting (Hf, Zr, Ta, Nb, Ti)B2 grain size was as small as 0.5 μm. Vickers hardness of HEB5C-15 densified at 1500 °C was 24.90 ± 1.39 GPa, at least 20% higher than the corresponding value in the cobalt free counterpart densified at 2000 °C.

Thermal and electrical properties of spark plasma sintered (Ti,Cr)B2 ceramics

AbstractThermal and electrical properties were measured for TiB2 ceramics containing varying CrB2 contents up to 33 mol%. The room‐temperature thermal diffusivity decreased with increasing Cr content from 0.330 ± 0.003 cm2/s for pure TiB2 to 0.060 ± 0.003 cm2/s for (Ti0.66Cr0.33)B2. The amount of anisotropy in the coefficients of thermal expansion increased with increasing Cr content and the c‐axis had the greatest dependence on Cr addition, with an increase of more than 25% in the thermal expansion for 33 mol% CrB2 compared to TiB2, whereas the a‐axis only increased by about 8%. The electrical conductivity was the lowest for (Ti0.66Cr0.33)B2 at ∼8.5 × 103 S/cm compared to ∼106.1 × 103 S/cm for nominally pure TiB2. Overall, the addition of CrB2 as a sintering aid for TiB2 was shown to have a significant effect on the thermal and electrical properties of TiB2 for additions as small as 5 mol% CrB2.

Integrated high strength and high toughness induced by elongated TiB2 grains in reactive sintered TiB2–TiC–SiC ceramics

AbstractAlthough the addition of other phases into TiB2 matrix to form ceramic composites has been widely used to improve the mechanical properties of monolithic TiB2 ceramics, it is still difficult to greatly enhance the flexural strength and fracture toughness simultaneously. In this work, TiB2–TiC–SiC composites were successfully prepared by reactive spark plasma sintering of Ti3SiC2–B4C–Ti powder mixtures. During the sintering process, TiB2 grains grew into an elongated morphology, endowing the composites with integrated high strength and high toughness. The growth mechanism of TiB2 grains was attributed to the evaporation–condensation kinetics induced by the presence of B2O3. These findings can accelerate the exploration of ceramic composites with excellent comprehensive properties.

Superhard single‐phase (Ti,Cr)B2 ceramics

AbstractA nominally pure and dense (Ti0.9Cr0.1)B2 ceramic was produced by spark plasma sintering of powders synthesized by boro/carbothermal reduction of oxides. The synthesized powders were a single phase and had an average particle of 0.4 ± 0.1 μm and an oxygen content of 1.2 wt%. Average Vickers hardness values of the resulting ceramics increased from 25.9 ± 0.8 GPa at a load of 9.81 N, to 46.3 ± 0.8 GPa at a load of 0.49 N. Compared to the nominally pure TiB2 ceramic obtained under the same processing conditions, the (Ti0.9Cr0.1)B2 ceramic had higher values under the same load due to the finer average grain size (2.4 ± 1.0 μm), higher relative density, and solid solution hardening. The results indicated that the Cr addition promoted densification, suppressed grain growth, and improved the hardness of TiB2 ceramics. This is the first report for dense and single‐phase (Ti,Cr)B2 ceramics as superhard materials.

Elastic-plastic response of TiB2 under shock compression

Particle velocity profiles of a TiB2 ceramics under one-dimension plate impact were measured up to 45 GPa. The Hugoniot-elastic limit of TiB2 was determined to be 8–9 GPa. Mechanical damage induced three-wave structures were only observed for shock stress above ∼31 GPa. TiB2 sustains large shear strength beyond the Hugoniot-elastic limit, which leads to the abnormal downward bending of Hugoniot in the plastic region.

Исследование структуры и свойств металломатричных композиционных материалов, полученных методом прямого лазерного выращивания

Due to mechanical properties, Inconel family alloys are proven to be functional materials that are used at elevated temperatures in chemically aggressive environments and under high loads. Development of additive technologies has revealed a potential of these alloys as an initial powder raw material for additive manufacturing machines. In this work, the application of metal matrix composite materials in a direct laser growing technology is studied. The technology of self-propagating high-temperature synthesis is used to manufacture the composite material. The study results show that the application of metal matrix materials in the technology of direct laser growing allows one to increase wettability of ceramic particles by a matrix metal. As a result, the quality of particle-matrix borders is improved, the porosity is decreased, and the uniformity of the distribution of particles in the matrix is increased. The structure of the obtained materials is represented by Inconel 625 matrix alloy and inclusions of TiB2 ceramics. The average size of the ceramic particles is less than 300 nm. It is shown that adding to Inconel 625 powder of a composite metal matrix SHS powder of NiTi-TiB2 in an amount of 5 wt% leads to an increase in the microhardness of the material by 1.5 times relative to the materials obtained from pure Inconel 625. At the same time, there is an increase in the ultimate strength of the materials up to 920 MPa and a decrease in the ductility by 15% relative to the samples made of pure Inconel 625 alloy.

Comparative investigation of the properties of graphene nanoplatelet reinforced titanium diboride and niobium diboride ceramics

In this study, the effect of GNP concentration on the mechanical properties of spark plasma sintered TiB2 and NbB2 ceramics was investigated. GNP reinforced TiB2 and NbB2 specimens were aimed to produce with nearly full densification. Herein, SEM investigations, Raman analysis, and oxidation behavior of the samples were reported. GNP addition into the TiB2 and NbB2 matrices showed a different effect on various properties of the composites. GNP loading tends to enhance densification by removing native oxides of both TiB2 and NbB2 matrices. GNPs were more effective in the oxygen removal mechanism for TiB2 composites than NbB2. The highest relative density was obtained for TiB2-GNP and NbB2-GNP composites as 98.6% with 7 vol% and 5 vol% GNP additions, respectively. The Vickers microhardness decreased with increasing GNPs loading for both matrices. NbB2-GNP composites possessed higher fracture toughness and better oxidation resistance than TiB2-GNP composites.

Thermal properties of ZrB2-TiB2 solid solutions

Zirconium diboride ceramics were prepared with additions of up to 50 vol.% TiB2. The resulting (Zr,Ti)B2 ceramics formed complete solid solutions based on x-ray diffraction. The addition of TiB2 resulted in grain size decreasing from 22 μm for nominally pure ZrB2 to 7 μm for ZrB2–50 vol.% TiB2. The thermal conductivity at 25°C ranged from 93 W/m⋅K for nominally pure ZrB2 to 58 W/m⋅K for ZrB2–50 vol.% TiB2. Thermal conductivity was as high as 67 W/m⋅K for nominally pure ZrB2 at 2000°C, but dropped to 59 W/m K with the addition of 50 vol.% TiB2. Electrical resistivity measurements were used to calculate the electron contribution to thermal conductivity, which was 76 W/m⋅K for nominally pure ZrB2 decreasing to 57 W/m⋅K when 50 vol.% TiB2 was added. The phonon contribution to thermal conductivity did not change significantly for ≤10 vol.% TiB2. Additions of ≥25 vol.% TiB2 reduced the phonon contribution to nearly zero for all temperatures.