Thin TiC Research Articles

Thermal properties of diamond/Cu composites enhanced by TiC plating with molten salts containing fluoride and electroless-plated Cu on diamond particles

To improve the thermal properties of diamond/Cu composites for thermal management applications, we designed dual-coated diamond particles for preparing composites. A thin TiC coating is formed on diamonds using molten salt with NaCl-KCl-NaF, then electroless plating of Cu is applied. The effects of salt bath temperature on the formation of TiC coating and the percentage of modified diamonds on the thermal performance of the composites were investigated. At temperature as low as 700 °C, Ti and diamond particles forms a TiC coating with a thickness of 1 μm in molten salt containing fluoride. In response to an increase in temperature, the thickness of the formed TiC coating increases and is prone to cracking and flaking. Cu coating well coats the TiC/diamond by electroless plating. The hot-pressing diamond/Cu composite with 60 vol% modified diamonds exhibits the best thermal conductivity of 495.5 W·m−1·K−1, slightly below the values predicted by the model H-J and DEM, and lower thermal expansion coefficient of 5.86 × 10−6 K−1, corresponding to the Kerner model.

Effect of micro-oxidation and Cu modification of C/C composite on microstructure and mechanical properties of C/C|Ti3Al joints

In order to form the strong mechanical interlocking and improve the compatibility between interlayer and C/C composite, a porous structure with a series of annular gaps and Cu coating on C/C composite surface were designed and prepared by micro oxidation in the muffle furnace and magnetron sputtering, respectively. The C/C composite |Ti3Al joints were prepared by transient liquid phase (TLP) diffusion bonding. During the bonding process, the liquid phase flowed into the gaps, and the infiltration layer is formed between C/C composite and core interlayer. The infiltration layer mainly consists of C/C matrix, TiC and Ag (s, s), and the CTE of infiltration layer between that of C/C composite and interlayer. Therefore, the mismatch of thermal deformation between C/C composite and interlayer can be reduced, which can avoid high stress in the joint. After surface modification of C/C composite with micro-oxidation at 630 °C for 30min and Cu film, the wettability of liquid phase on C/C composite increased, and Ti–Cu phase formed in the core interlayer of the corresponded joints, which consumes the Ti atoms in liquid phase and causes a thin TiC layer. The shear strength of the joints increases from 34.58 MPa (the original joints) to 44.23 MPa (the pretreated C/C|Ti3Al joints) under optimized process (i.e. 880 °C, 10min), and the fracture not occurs in C/C composite but in joint area after pretreatment of C/C composite.

Bioinert TiC ceramic coating prepared by laser cladding: Microstructures, wear resistance, and cytocompatibility of the coating

Recent advance in biological applications such as artificial joint replacement are focused towards fabricating reliable bearing surface to extend their service life. Given this perspective, incremental attempts have been made to enhance the wear resistance of titanium alloys used widely in artificial joint and mechanical reliability of brittle TiC ceramic, but plan often don't go along with reality. It is proposed that both high mechanical reliability and wear resistance can be hold if a thin TiC ceramic coating is formed onto high toughness Ti6Al4V alloy used widely in biological applications. In this paper, bioinert TiC ceramic coating was fabricated on Ti6Al4V substrate surfaces through laser cladding using preplaced TiC nanoceramic powders on the substrate surfaces. The microstructural characteristics of the TiC ceramic coating were investigated in detail. Further, the rapid melting mechanism of the TiC nanoparticles and the microstructural formation mechanism of the coating were revealed. Moreover, the wear mechanism and cytocompatibility of the coating were identified. The results showed that the original TiC nanoparticles completely melted and solidified to form dendritic TiC ceramic coating owing to the small size effect of the nanoparticles and the thermodynamic effect of the high-energy laser beam . The wear resistance of the TiC ceramic coating fabricated by laser cladding was three times higher than that of the Ti6Al4V substrate, and the coating had the same good cytocompatibility as that shown by Ti6Al4V. Microstructure-phase-property relationships in TiC ceramic coating were revealed and discussed according to our research findings. The designed TiC coating and Ti alloy hybrid might be potential application in artificial joint surfaces and other implants with strong wear-resistance requirements. • Bioinert TiC ceramic coatings on Ti6Al4V substrate was fabricated by laser cladding using preplaced TiC nanoparticles. • TiC dendrites were generated owing to the high-temperature diffusion of carbon atoms and Ostwald ripening mechanism. • The formation mechanism of ceramic coatings fabricated by laser cladding using TiC ceramic nano particles was proposed. • The coating showed comparable cytocompatibility to Ti alloy and did not affect cell adhesion, spreading, and proliferation.

Atomically thin titanium carbide used as high-efficient, low-cost and stable catalyst for oxygen reduction reaction

Addressed herein, a highly effective, low-cost and stable TiC nanocatalyst was successfully synthesized through ultrasonic exfoliation of commercial TiC in deionized water and its application as a catalyst in the oxygen reduction reaction is outlined. A facile ultrasonic exfoliation was applied to fabricate atomically thin TiC. The structure, morphology, composition and catalytic properties of atomically thin TiC were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), and electrochemical methods. Atomically thin TiC possesses superior ORR activity in terms of catalytic performance, methanol tolerance, and long-term durability. This work has been provided a low-cost, efficient and stable substitute catalyst for Pt/C to promote the industrialization for energy storage and conversion devices.

Wettability and joining of SiC by Sn-Ti: Microstructure and mechanical properties

Reliable SiC/Sn-Ti/SiC joints were obtained by brazing (950 °C/10 min) and soldering (250 °C/2 min) following premetallization depend on the wettability of Sn-Ti on SiC. The microstructures of Sn-Ti/SiC interface were characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy, and the mechanical properties of joints were evaluated by shear tests. Active Ti enhanced the wettability of Sn on SiC with the decrease of contact angle from 150° to 20°. Ti direct reacted with SiC to produce TiC and combines with released Si forming Ti5Si3. Much lower Ti concentration per contacting area in brazing and metallization, compared to wetting, resulted in defective bonding of Sn-Ti/SiC and few amounts of interfacial products (thin TiC layer or partial covered TiC layer with Ti5Si3). All of the SiC/SiC joints possess a similar shear strength of 27–32 MPa and rupture through β-Sn matrix in ductile fracture.

Solid-state joining of SiC using a thin Ti3AlC2, TiC, or Ti filler

SiC monoliths containing 5 wt.% Al2O3-Y2O3 additive were joined using a thin Ti3AlC2, TiC, or Ti filler. After joining at 1900 °C for 5 h under 3.5 MPa, the joint properties were compared in terms of the microstructure, phase evolution, joining strength, and possible elimination of the joining layer. Although all samples showed a sound joint, the microstructure differed according to the filler. SiC joined with Ti3AlC2 filler showed an indistinguishable joining interface due to the filler decomposition followed by solid-state diffusion into the SiC base, whereas TiC filler remained at the interface without showing decomposition or diffusion. In contrast, the Ti filler showed a possible elimination of the joining layer because of the diffusion of Ti and the formation of TiC. The mean joining strengths for the Ti3AlC2, TiC, and Ti fillers were 300, 234, and 248 MPa, respectively, which were comparable to that of the base SiC material (250 MPa).

Joining of Graphite to Ti6Al4V Alloy Using Cu‐Based Fillers

Joining of graphite to Ti6Al4V (TC4) alloy is achieved with three Cu‐based fillers (Cu‐22TiH2, Cu‐50TiH2, and Cu‐30TiH2‐5Ni). Microstructural characterizations reveal that a thin TiC layer and a diffusion layer containing Ti solid solution (Ti(ss)) with Ti2Cu are developed at the graphite/filler layer and filler layer/TC4 interfaces, respectively. For the joint obtained with Cu‐22TiH2 filler, the filler layer consists of TiCu and Ti2Cu, whereas it is composed of Ti2Cu, TiCu, and Ti(ss) for the joint with Cu‐50TiH2 filler. In the case of the joint with Cu‐30TiH2‐5Ni filler, the filler layer mainly contains Ti(Cu,Ni) and Ti2(Cu,Ni). The microhardness of the interfacial area in the joints is highly related to the microstructure of joints. The filler layer of the joint with Cu‐50TiH2 filler exhibits higher microhardness than those with Cu‐22TiH2 and Cu‐30TiH2‐5Ni fillers, owing to the high content of Ti2Cu phase with relatively high microhardness and the increase in hardness of Ti‐Cu intermetallics at higher brazing temperatures. The high shear strength of joints reveals favorable bonding of Cu‐based fillers with substrates.

Interaction of Graphite with a Ti–Al Melt during Self-Propagating High-Temperature Synthesis

We have studied in detail the structuring of combustion products in the Ti–Al–C system at low carbon concentrations (96 wt % (Ti + Al) + 4 wt % graphite) prepared by self-propagating high-temperature synthesis and compared the results to those for carbon-free samples prepared by the same method. A thin (~500 nm) TiC carbide layer has been shown to be formed on the surface of unreacted graphite particles, followed by the growth of the Ti2AlC MAX phase, which has a laminate structure. The presence of the Ti2AlC phase in the synthesized samples has been confirmed by X-ray diffraction and energy dispersive analysis. TiC has not been detected by X-ray diffraction, presumably because it is present in a small amount.

Dissimilar joining of carbon/carbon composites to Ti6Al4V using reactive resistance spot welding

A 2D C/C composite with a high porosity (low strength) and a 3D C/C composite with a low porosity (high strength) were investigated for dissimilar joining to Ti6Al4V via reactive spot welding. It was determined that infiltration of melted metal into the composite and formation of a continuous thin TiC layer at the interface of the joints were the dominant joining mechanisms. The 2D C/C composite with a flat surface was successfully joined to Ti6Al4V due to the infiltration of the melted Ti6Al4V into its porous content. On the other hand, it was necessary to drill rectangular grooves onto the surface of the 3D C/C composite to facilitate the infiltration of the melted Ti into the composite, which produced high-strength joints. Surface patterning was determined to be necessary to join the components with mismatching coefficients of thermal expansion. The strength of the 2D C/C composite and Ti6Al4V joints was found to be 7 MPa, while the maximum strength of the groove-patterned 3D C/C composite and Ti6Al4V joints reached 46 MPa.

Effects of carbon content and size on Ti-C reaction behavior and resultant properties of Cu-Ti-C alloy system

TiC-strengthened Cu alloys with various nominal compositions were prepared by a high-energy ball-milling process, followed by consolidation using spark plasma sintering (SPS), and a subsequent heat treatment. The results indicated that the lower atomic ratio of C/Ti, the more residual Ti in copper matrix, resulting in a lower electrical conductivity but higher microhardness of alloy. The optimal atomic ratio was found to be close to1.0. The reaction behavior of Ti-C in the Cu-Ti-C system during this process was investigated. Microstructural results suggested that TiC formation is through a diffusion-controlled mechanism. A thin TiC layer was formed at the surface of C particles, and the growth of TiC layer was controlled by interdiffusion of C and Ti atoms across the TiC layer. An incomplete chemical reaction between Ti and C, characterized by a core-shell structure, was observed when the initial C particles were large, and the TiC particle size was found to strongly depending on the C particle size.

Study of reaction sequences during MSR synthesis of TiC by controlled ball milling of titanium and graphite

During reactive ball milling of Ti and C, mechanically induced self-propagating reaction (MSR) synthesis of TiC is reported to occur via a process including initial formation of small amounts of TiC prior to exothermic ignition, followed by MSR and the formation of stiochiometric TiC (Dorofeev et al., 2011; Oghenevweta et al., 2016 [1, 2]). However, both the chemical evolution and mechanisms of reaction and growth of TiC both prior to, during and after ignition are not fully understood. This research focuses on fundamental understanding of the reaction sequences during MSR synthesis of TiC from elemental Ti and C (graphite).Magnetically controlled ball milling of stoichiometric (1:1) powder mixtures of titanium (Ti) and graphite (C) was performed under He gas with the exothermic ignition point by determined via in-situ temperature measurement. X-ray diffraction, Scanning Transmission Electron Microscopy (STEM) with electron energy loss spectroscopy (EELS), Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were employed to interpret the reaction sequences.The reaction sequence involved the following: During milling prior to ignition, severely deformed Ti, spheriodised graphite and amorphous carbon forms, and minor amounts of off-stiochiometric nano-TiC1−x crystals. In addition to the formation of TiC1−x, XPS revealed the formation of oxide skins coating the surface regions of the milled powders. There is also an evolution towards stiochiometric TiC with increasing milling time. Immediately after ignition, a reacted product comprising a mixture of multi-layer stacks of thin TiC plates form, in addition to a matrix comprising large TiC particles which have been liquid phase sintered under the high local heat of reaction by thin layers of unreacted Ti. MSR occurs via a dual mechanism involving rapid growth of existing TiC, plus nucleation and growth of new TiC. High spatially resolved EELS combined with STEM revealed additional information about the inhomogeneous chemical environment of the milled powders.

Wetting behavior of graphite and CFC composites by Cu-Ti compacts

The wetting behavior of Cu-Ti powder compacts with 22 wt % Ti and 50 wt % Ti on carbon materials, including graphite and carbon fiber reinforced carbon composites (CFC), has been investigated in a vacuum using the sessile drop method. The equilibrium contact angles of Cu-22Ti (containing 22 wt% Ti) on the graphite and the CFC substrates at 1 253 K are 32° and 26°, respectively, whereas the equilibrium contact angle of 9° is obtained for Cu-50Ti (containing 50 wt% Ti) on both the graphite and the CFC substrates at 1 303 K. Microstructural analysis of the wetting samples shows that a thin TiC reaction layer is developed at the interfacial area and Ti-Cu intermetallic compounds are formed over the reaction layer. The investigation on the spreading kinetics of Cu-Ti compacts on carbon materials substrates at fixed temperatures reveals that the spreading is controlled by the interfacial reactions in the first stage and then by the diffusion of the active Ti from the drop bulk to the triple line in the later stage. The spreading is promoted by the intense reaction at higher Ti concentrations.

Laser-induced exothermic bonding of carbon fiber/Al composites and TiAl alloys

In this paper, a highly-efficient method for bonding Carbon Fiber (Cf)/Al composites and TiAl alloys was developed by means of laser-induced exothermic reaction of a Ni-Al-Ti interlayer. To examine the interlayer exothermic performance, the adiabatic temperature was calculated and the reaction temperatures were measured. Based on SEM, XRD and TEM, the interfacial reactions between carbon fiber and interlayer products were investigated. Results show that the addition of Ti enhanced the interfacial reactions between carbon fibers and interlayer products. The resulting formation of a 300–400nm thin Ti-C layer at the NiAl3/carbon fiber interface was identified as a key player in improving the joining quality on the Cf/Al side. The typical interfacial structure of the joint is (Cf/Al)/Ti-C/NiAl3/Ni2Al3/(NiAl+Al3NiTi2)/Al3NiTi2/TiAl. The joint formation mechanism was discussed. In addition, the effect of Ti content on the microstructure and mechanical properties of joints were investigated in detail. The optimum value of Ti content was found to be 5wt.%, leading to a defect-free joint and a maximum shear strength of 45.8MPa.

Cutting Characteristics of Binderless Diamond Tools in High-Speed Turning of Ti-6Al-4V – Availability of Single-Crystal and Nano-Polycrystalline Diamond –

In this study, the tool performance of two types of binderless diamond tools – single-crystal diamond (SCD) and nano-polycrystalline diamond (NPD) – is investigated in the high-speed cutting of titanium alloy (Ti-6Al-4V) with a water-soluble coolant. The NPD tool allows for a larger cutting force than the SCD tool by dulling of the cutting edge, despite NPD being harder than SCD. This large cutting force and the very low thermal conductivity of NPD yield a high cutting temperature above 500°C, which promotes the adhesion of the workpiece to the tool face, thereby increasing tool wear. Based on the morphology of the tool edge without scratch marks and the elemental analysis by energy-dispersive X-ray spectroscopy (EDX) of both the flank face and the cutting chips, diffusion-dissolution wear is determined to be the dominant mechanism in the diamond tool. A thin TiC layer seems to be formed in the boundary between the diamond tool and the titanium alloy at high temperatures; this is removed by the cutting chips.

Brazing of graphite to Cu with Cu50TiH2 + C composite filler

Brazing of graphite to Cu has been successfully realized with Cu50TiH2 (containing 50 wt% Cu)-based fillers (including Cu50TiH2 filler and Cu50TiH2 + C composite filler) in vacuum at 1223 K. The average shear strength is 10.8 MPa for the joints brazed with Cu50TiH2 filler. Microstructure observation of the joints shows the crack-free interfaces both at the graphite and the Cu sides. The filler layer mainly consists of Cu base solid solution and Ti–Cu intermetallics. Furthermore, a thin TiC reaction layer is developed close to the graphite substrate. With regard to the joints brazed with Cu50TiH2 + C composite filler, the average shear strength of the joints increases to 18.0 MPa. Microstructural characterization reveals that TiC particles have been synthesized in situ in the filler layer. Cu base solid solution and Ti–Cu intermetallics together with TiC particles are detected in the filler layer. The TiC particles synthesized in situ distribute uniformly in the filler layer, which may act as reinforcements and consequently benefit the improvement of the graphite/Cu joints.

Processing of metal-diamond-composites using selective laser melting

Purpose – The purpose of this paper is a feasibility study that was performed to investigate the basic processability of a diamond-containing metal matrix. Powder-bed-based additive manufacturing processes such as selective laser melting (SLM) offer a huge degree of freedom, both in terms of part design and material options. In that respect, mixtures of different powders can offer new ways for the manufacture of materials with tailored properties for special applications such as metal-based cutting or grinding tools with incorporated hard phases. Design/methodology/approach – A two-step approach was used to first investigate the basic SLM-processability of a Cu-Sn-Ti-Zr alloy, which is usually used for the active brazing of ceramics and superhard materials. After the identification of a suitable processing window, the processing parameters were then applied to a mixture of this matrix material with 10-20 volume per cent artificial, Ni-coated mono-crystalline diamonds. Findings – Even though the processing parameters were not yet optimized, stable specimens out of the matrix material could be produced. Also, diamond-containing mixtures with the matrix material resulted in stable specimens, where the diamonds survived the layer-wise build process with the successive heat input, as almost no graphitization was observed. The diamond particles are fully embedded in the Cu-Sn-Ti-Zr matrix material. The outer part of the diamonds partly dissolves in the matrix during the SLM process, forming small TiC particles and most likely a thin TiC layer around the diamond particles. Originality/value – The feasibility study approved the SLM processing capabilities of a metal-diamond composite. Although some cracking phenomena sill occur, this seems to be an interesting and promising way to create new abrasive tools with added value in terms of internal and local lubrication supply, tooling temperature control and improved tooling durability.

Thermal conductivity enhancement in Cu/diamond composites with surface-roughened diamonds

Cu/diamond composites have potential as a heat spreading material in small-scale devices. In this study, we show that the use of surface-roughened diamonds obtained by heat treatment under N2 atmosphere and subsequently coated with a thin layer of Ti coating is a feasible method to effectively improve the interfacial bonding and thermal conductivity of Cu/diamond composites. The diamond surface state and prepared composites were investigated by the combination of X-ray diffraction, Raman spectroscopy and microstructure analysis. It is found that the surface-roughened diamonds are in favor of the formation of effective chemical bonds between diamonds and Ti coating through the formation of thin TiC layer and simultaneously provide increased Cu/diamond contact area, which are beneficial to largely decrease the interfacial thermal resistance and thus to greatly enhance the thermal conductivity of Cu/diamond composites.

Deformation Properties of TiC-Mo Eutectic Composite at High Temperature

Abstract The deformation properties of a TiC-Mo eutectic composite were investigated in a compression test at temperaturesranging from room temperature to 2053 K and at strain rates ranging from 3.9×10 −5 s −1 to 4.9×10 −3 s −1 . It was found that thismaterial shows excellent high-temperature strength as well as appreciable room-temperature toughness, suggesting that thematerial is a good candidate for high-temperature application as a structure material. At a low-temperature, high strength isobserved. The deformation behavior is different among the three temperature ranges tested here, i.e., low, intermediate and high.At an intermediate temperature, no yield drop occurs, and from the beginning the work hardening level is high. At a hightemperature, a yield drop occurs again, after which deformation proceeds with nearly constant stress. The temperature- andyield-stress-dependence of the strain is the strongest in this case among the three temperature ranges. The observed high-temperature deformation behavior suggests that the excellent high-temperature strength is due to the constraining of thedeformation in the Mo phase by the thin TiC components, which is considerably stronger than bulk TiC. It is also concludedthat the appreciable room-temperature toughness is ascribed to the frequent branching of crack paths as well as to the plasticdeformation of the Mo phase.Key wordsplastic deformation, TiC-Mo, eutectic composite, compression test, high temperature strength.

Joining mechanism between Al2O3–Ag–Cu–Ti composite coating and GCr15 substrate

Using a mixture of Al2O3, Ag, Cu, and Ti particles, an Al2O3–Ag–Cu–Ti composite coating was fabricated on GCr15 substrate by plasma spraying. To obtain strong joining between the composite coating and substrate, samples were heated at 700–1000°C for 10min in a vacuum chamber. The microstructure and composition of the coating were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). SEM images revealed that the shapes of the Ag and Cu particles in the coating changed because of a eutectic reaction when the joining temperature exceeded 800°C. SEM and XRD results showed that a thin TiC and Ti2Fe composite layer was formed at or close to the interface when the joining temperature was above 900°C. In addition, an obvious reaction layer with a concentration of elemental Ti between the Ag–Cu–Ti alloy and the Al2O3 particle was formed when the joining temperature exceeded 800°C. Evaluation of the mechanical properties of the join between the composite coating and the substrate was performed using an impact tester, and the sample joined at 900°C showed excellent adhesion strength and toughness.

Formation and growth mechanism of TiC terraces during self-propagating high-temperature synthesis from a FeTiC system

TiC terraces were prepared in situ through self-propagating high-temperature synthesis (SHS) reaction with 10wt.% FeTiC elemental powder mixtures. The formation and growth mechanism of TiC during the SHS process were explored. The results of combustion wave quenching experiment showed that the formation mechanism of TiC could be ascribed to the dissolution of C into FeTi melt and the precipitation of TiC from the saturated melt. The X-ray diffraction, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses revealed that TiC terraces grew through the layer-by-layer mechanism along [100] direction, while thin TiC monolayer was formed by two-dimension (2D) nucleation growth mode.