TiB2 Samples Research Articles

Elastoplastic and Electrochemical Characterization of xTiB2 Strengthened Ti Porous Composites for Their Potential Biomedical Applications

The microstructure, elastoplastic properties, and corrosive response of induced porous Ti-TiH2 materials reinforced with TiB2 particles were investigated. Samples were fabricated using CP-Ti Grade1, Titanium Hydride (TiH2), TiB2 powders (0, 3, 10, and 30 vol.%), and ammonium bicarbonate salt (40 vol.%) as a space holder. Composites were fabricated using the Powder Metallurgy technique under high-vacuum conditions (HVS) at 1100 °C. Scanning electron microscopy, X-ray diffraction, nanoindentation tests, and electrochemical assays were used to investigate the pore formation, pore distribution, phase formation, elastoplastic properties, and electrochemical behavior of the compounds, respectively. With a mean pore diameter of 50–900 µm and Young’s modulus of less than 100 GPa, which is close to the properties of human bone, the pore structures of the compounds processed here are shown to be a potential biomaterial for osseointegration. In addition, their H/Er and H3/Er2 ratios for the reinforced samples are higher than those of the unreinforced sample (1.5 and 4 times higher than the unreinforced sample, respectively), suggesting a better wear resistance of the Ti-TiH2/xTiB2 composites. Electrochemical experiments demonstrated that the Ti-TiH2/xTiB2 composites exhibited superior passivation properties compared to the Ti-TiH2 sample. Additionally, the corrosion rates exhibited by the 3 and 10 vol.% of TiB2 samples were found to be within an acceptable range for potential biomedical applications (29.26 and 185.82 E-3 mm·y−1). The elastoplastic properties combined with the electrochemical behavior place the Ti-TiH2/3-10TiB2 composites as potential candidates for the biomedical application of CP-Ti.

Observation of tantalum deposition and growth on TiB2 and ZrB2 from PISCES-RF deuterium and helium plasma exposures

Deuterium and helium plasma exposures on bulk TiB2 and ZrB2 samples were performed using the PISCES-RF linear plasma device. 40 and 90 eV deuterium ion plasma exposures were performed at 240 and 800 °C sample temperatures, and 80 eV helium ion plasma exposures were performed at 800 °C sample temperatures. Following plasma exposures, it was discovered that two plasma conditions (90 eV deuterium and 80 eV helium at 800 °C) resulted in thick (>200 nm) tantalum-rich (>10 at%) surface features on the targets, presumably from tantalum sourced from a tantalum adapter mask or cap used as part of the target holder. This work aims to characterize these tantalum-rich features and examine the mechanisms of impurity deposition.Plasma-induced surface morphology of the tantalum-rich surface layers depends on plasma properties and target temperature and chemistry. Greater titanium sputtering compared to zirconium resulted in more distinct surface features in the TiB2 samples compared to the ZrB2 samples via increased, prompt deposition onto tantalum surface impurities. There is still uncertainty as to why thick tantalum deposition only occurred under some plasma exposure conditions but not others; it is likely due to tantalum sputtering by a combination of boron molecules from the targets and carbon-impurities in the tantalum mask or targets. Impurity driven surface features are a well-documented phenomena in samples exposed to plasma from linear plasma device facilities—this work confirms the occurrence of this and emphasizes the need for chemistry characterization of isolated post-mortem surface features in plasma-exposed samples.

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.

Effect of the Mass Fraction of NiTi-TiB2 SHS-Particles on the Phase Composition, Structure, and Mechanical Properties of Inconel 625-NiTi-TiB2 Composites Produced by Direct Laser Deposition.

This paper studies the impact of the mass fraction of NiTi–TiB2 particles obtained by the method of self-propagating high-temperature synthesis (SHS) on the phase composition, structure, and mechanical properties of composites made by direct laser deposition from an Inconel 625–NiTiz–TiB2 powder mixture. Composites were obtained from a powder mixture with the mass fraction of particles at 5–10 wt%, and they consisted of an Inconel 625 metal matrix wherein ceramic inclusions of titanium diboride TiB2 were distributed. Increasing the mass fraction of SHS-produced NiTi particles from 30 to 95 wt% led to the emergence of a NiTi intermetallide phase in the matrix material as well as an increase in the average TiB2 particle size and formation of their agglomerates. In addition, an increase in the microhardness of the materials was observed. The graph of tensile strength of Inconel 625–NiTi–TiB2 samples has a parabolic shape with a maximum at 1000 MPa (when the mass fraction of SHS-produced NiTi–TiB2 particles is at 30 wt%). A further increase in the mass fraction of NiTi–TiB2 led to a decrease in the tensile strength down to 400 MPa. Here the deformation of samples decreases linearly as the ratio of composite particles in the initial mixture increases. From a comparative analysis of the results obtained, the optimal mass fraction of composite NiTi–TiB2 particles in the Inconel 625-NiTi–TiB2 powder mixture was found to be 5 wt%.

Effects of SiC amount and morphology on the properties of TiB2-based composites sintered by hot-pressing

This investigation intended to assess the influence of SiC morphology on the sinterability and physical-mechanical features of TiB2-SiC composites. For this aim, different volume percentages of SiC particles and SiC whiskers were introduced to TiB2 samples hot-pressed at 1950 °C for 2 h under an external pressure of 25 MPa. The characterization of as-sintered specimens was carried out using X-ray diffraction, optical microscopy, and scanning electron microscopy. The relative density studies revealed that SiCw had a more significant impact on the sinterability of TiB2-based composites. The XRD investigation confirmed the production of an in-situ TiC phase during the hot-pressing; however, some peaks related to the graphitized carbon also appeared in the patterns of SiCw-doped ceramics. The addition of 25 vol% SiCp halved the average grain size of TiB2 while introducing the same content of SiCw decreased this value by just around 20%. Finally, the highest Vickers hardness and fracture toughness were obtained for the sample reinforced with 25 vol% SiCw, standing at 29.3 GPa and 6.1 MPa m1/2, respectively.

Influence of TiB2 content on the properties of TiC–SiCw composites

The impact of various volume percentages of TiB2 additive (0, 10, 20, and 30) on the microstructure, relative density (RD), Vickers hardness, flexural strength, and thermal conductivity of as-sintered TiC-10 vol% SiCw-based composite samples were scrutinized. All four samples were sintered using the SPS method under the following circumstances; sintering temperature of 1900 °C, dwell time of 7 min, and external pressure of 40 MPa. The best relative density of 98.73% was achieved for the sample with no TiB2 additive, indicating the negative effect of TiB2 additive on the RD and formation of porosity. The microstructural observations and XRD results confirmed the chemical interaction of TiO2 and B2O3 oxide layers and SiCw and in-situ formation of the TiSi brittle phase and TiC. The most significant values of flexural strength (511 MPa) and hardness (27.67 GPa) were related to TiC-10 vol% SiCw and TiC-10 vol% SiCw-30 vol% TiB2 samples, respectively. On the contrary, the specimens with 30 vol% and 10 vol% TiB2 as additive presented the poorest qualities of flexural strength (234 MPa) and Vickers hardness (22.12 GPa). Finally, the influence of the TiB2 content on the thermal conductivity was evaluated, indicating the positive impact of this secondary phase on this characteristic, so with adding 30 vol% TiB2 to TiC-10 vol% SiCw, a thermal conductivity of 30.7 W/m.K was obtained.

Effects of Eutectic Modification and Grain Refinement on Microstructure and Properties of PM AlSi7 Metallic Foams

For AlSi7 foams, microstructure modification by variation of solidification rates and addition of Sr, B and TiB2/TiAl3 was investigated and its transfer to powder metallurgical metal foaming processes demonstrated. Microstructural characterization focused on grain size and morphology of the eutectic phase. Cooling rates during solidification were linked to secondary dendrite arm spacing, establishing a microstructure-based measure of solidification rates. Effects of refining and modification treatments were compared and their influence on foam expansion evaluated. Studies on foams focused on comparison of micro- and pore structure using metallographic techniques as well as computed tomography in combination with image analysis. Reference samples without additives and untreated as well as annealed TiH2 as foaming agent allowed evaluation of pore and microstructure impact on mechanical performance. Evaluation of expansion and pore structure revealed detrimental effects of Sr and B additions, limiting the evaluation of mechanical performance to the TiB2 samples. These, as well as the two reference series samples, were subjected to quasi-static compression testing. Stress-strain curves were gained and density-dependent expressions of ultimate compressive strength, plateau strength and tangent modulus derived. Weibull evaluation of density-normalized mechanical properties revealed a significant influence of grain size on the Weibull modulus at densities below 0.4 g/cm3.

Effect of TiB2 particles on microstructure and crystallographic texture of Al-12Si fabricated by selective laser melting

Pronounced crystallographic texture, characteristic for the parts manufactured by selective laser melting, is eliminated upon addition of TiB2 microparticles to Al-12Si powder. Due to the wetting of TiB2 ceramic by Al-12Si melt and a high inoculation efficiency, a homogeneous microstructure consisting of fine equiaxed grains with random crystallographic orientation is formed by SLM processing of the Al-12Si/TiB2 powder mixture. The Al-12Si/TiB2 samples exhibit enhanced yield strength and microhardness, compared to the TiB2-free Al-12Si samples produced at the same SLM conditions.

A corrosion mechanism of titanium diboride in KF−AlF3−Al2O3 melt

TiB2 samples were exposed to molten KF−AlF3−Al2O3: 54.8-42.1-3.1mol% salt, at 680°C for 50, 100 and 200h. The corroded samples of TiB2 were investigated by SEM-EDX, EBSD, XRD, FT-IR and MAS NMR analysis. Corrosion was noted to occur predominantly as pitting attacks on the surface of the investigated materials. An inter-crystal and trans-crystal corrosion were identified on the cross-sections of the samples. A perturbation of TiB bonds was detected (SEM-EDX and NMR analysis), at which a formation of orthorhombic TiO2 was also identified (EBSD analysis). The subsequent NMR, XRD and FT-IR analysis of the behaviour of TiB2 powder in molten KF−AlF3−Al2O3 supports the statement about the formation of orthorhombic TiO2 and mullite type of aluminium borates.

Influence of MoSi2 Addition on Load‐Dependent Fretting Wear Properties of TiB2 Against Cemented Carbide

In an earlier work, it was observed that the use of MoSi2 (up to 10 wt%) enhanced the densification and mechanical properties of TiB2. Therefore, the motivation of this study is three‐fold: (a) to assess whether a small amount of MoSi2 addition can enhance wear resistance property, (b) to study whether the MoSi2 addition will influence the formation of a tribochemical layer, and (c) to correlate the wear resistance with material properties in TiB2–MoSi2 materials. In order to address these issues, a series of fretting experiments were conducted systematically by varying load (2, 5, and 10 N) at an oscillating frequency of 4 Hz and a 100 μm linear stroke, for a duration of 100 000 cycles with a cemented carbide (WC—6 wt% Co cermet) ball as a counterbody. The average coefficient of friction of the TiB2 samples varied within a narrow range (0.50–0.54), without being much affected by either the sintering additive or the load. The wear volume increased with increasing load, while the specific wear rate of all the TiB2 compositions falls within a mild wear regime (1.1–3.4 × 10−6 mm3/Nm). Based on the experimental results, it can be said that the addition of MoSi2 degrades neither the wear resistance properties nor the frictional properties of TiB2, within the investigated load regime. The microcracking‐induced spalling has been found to be the dominant mechanism and, consequently, the wear volume is observed to have a linear dependency on the abrasion parameter. It is noteworthy that the tribo‐oxidation as well as the formation of finer wear debris particles occurs to a limited extent.

Development of High Temperature TiB<sub>2</sub>-Based Ceramics

In view of potentiality of titanium diboride (TiB2) materials for high temperature applications, this paper presents the state of art on the processing, microstructure and properties of TiB2 ceramics. TiB2 ceramics are of interest for applications such as cutting tools, wear resistant parts, armor material and electrode materials in metal smelting because of their excellent combination of properties including high hardness, elastic modulus, better strength to weight ratio, wear resistance, good thermal and electrical conductivity. However, such broader applications of the monolithic TiB2 are inhibited by factors like high sintering temperature and poor toughness. Hence, research efforts are directed towards processing TiB2 at lower sintering temperature as well as to enhance the properties with the use of various metallic and non-metallic sinter-additives. In the above perspective, we review the existing literature in this article. In addition, our recent research results obtained with TiB2-TiSi2 materials are also presented. A review of research results revealed that a combination of room temperature properties, i.e. maximum Vickers hardness of 31 GPa and indentation toughness of 11 MPa m1/2 and flexural strength of 810 MPa is obtainable with optimally sintered TiB2. More importantly, a maximum hardness of 9 GPa (at 900oC) and flexural strength of 471 MPa can be retained upto 1200oC. From the perspective of oxidation resistance, TiB2 samples exhibit parabolic oxidation kinetics below 1000oC as result of the formation of TiO2 (s), and B2O3 (l) and linear oxidation kinetics above 1000oC in the presence of crystalline TiO2 and volatile B2O3.

Self-diffusion of boron in TiB2

Self-diffusion studies of boron in polycrystalline TiB2 were carried out as a function of temperature, using a specially designed experiment with stable B10 tracers, B−enriched11 TiB2 samples, and secondary ion mass spectrometry for depth profiling. The diffusivities were extracted from the isotope depth profiles in the range between 950 and 1600 °C. They obey an Arrhenius behavior with an activation enthalpy of about ΔH=2.2 eV and a preexponential factor of D0=4×10−12 m2/s. Interpolation of the diffusivities to the melting point of 3225 °C reveals a very low value of about D(Tm)≈10−15 m2/s, which reflects the covalent bonds present in the material. A possible explanation for the low values obtained for D0 and ΔH is the assumption of a diffusion mechanism via vacancies, where in addition to thermal vacancies a substantial concentration of structural vacancies are present. The possible influence of grain boundaries and of the anisotropic crystal structure on the results is discussed together with crystallographic diffusion paths.

Effect of SiC on Interfacial Reaction and Sintering Mechanism of TiB2

Compacts of TiB2 with densities approaching 100% are difficult to obtain using pressureless sintering. The addition of SiC was very effective in improving the sinterability of TiB2. The oxygen content of the raw TiB2 powder used in this research was 1.5 wt%. X‐ray photoelectron spectroscopy showed that the powder surface consisted mainly of TiO2 and B2O3. Using vacuum sintering at 1700°C under 13–0.013 Pa, TiB2 samples containing 2.5 wt% SiC achieved 96% of their theoretical density, and a density of 99% was achieved by HIPing. TEM observations revealed that SiC reacts to form an amorphous phase. TEM‐EELS analysis indicated that the amorphous phase includes Si, O, and Ti, and X‐ray diffraction showed the reaction to be TiO2+ SiC → SiO2+ TiC. Therefore, the improved sinterability of TiB2 resulted from the SiO2 liquid phase that was formed during sintering when the raw TiB2 powder had 1.5 wt% oxygen.

ChemInform Abstract: Effect of Iron and Boron Carbide on the Densification and Mechanical Properties of Titanium Diboride Ceramics

Abstractis studied for TiB2 samples sintered at 2000 °C in argon atmosphere.

Transport properties of high purity, polycrystalline titanium diboride

Thermal conductivity data for several TiB2 samples are presented and the results for one sample extend from 80 to 400 K. These results show that the thermal conductivity attains a maximum value of about 130 W/m K at 140 K. An analysis of the results shows that this is caused by the electronic component of the thermal conductivity and that phonon conduction is also probably significant. Seebeck coefficient values agreed with the results of previous studies. The electrical resistivity of one sample was also determined to 1800 K. These results can be described by the Bloch–Grüneisen equation if the effect of thermal expansion is included.

Study of the Kondo effect and intrinsic electrical conduction in titanium diboride

Electrical resistivity data for seven dense polycrystalline TiB2 samples are reported. The data, which extend from 4.2 to 300 K, all show resistivity minima in the 34 – 47 K range and this is attributed to the Kondo effect. Although the residual resistivity values varied by only a factor of about 2, the strength of the Kondo effect changed by a factor of 15. These differences are related to the effects of processing variables. The ideal resistivity of TiB2 was calculated from the measurements and was found to vary about as T5 at low temperatures. These values can be adequately described by the Bloch–Grüneisen equation, and the characteristic temperature obtained from resistivity, 720 K, is in reasonably good agreement with the Debye temperature from specific heat measurements. A comparison of the electronic scattering part of the Bloch–Grüneisen constant shows that TiB2 is a somewhat better conductor than Ti and the electronic band structures of ZrB2 and Zr help to explain this difference.