Carbide Layer Research Articles

Impact of fiber surface gas treatments on interfacial bonding in SiC/BN/SiC minicomposites

AbstractBN interphases with different microstructures and a structural gradient were prepared by chemical vapor deposition (CVD) within SiC/SiC minicomposites. The interfacial shear stress (ISS) measured by the fiber push‐out test and the debonding location in the fiber/matrix interface zone during mechanical loading depends on the BN interphase structure. The ISS is higher when the structural organization of the BN interphase is poor, in which case debonding occurs on the fiber side. The Hi‐Nicalon S fiber surfaces were gas‐treated to strengthen the bond with the interphase. BCl3‐based reactive CVD treatments have produced a thin boron carbide layer on the fiber surface, resulting in a 30% increase in ISS. However, the minicomposites are brittle in tensile tests due to fiber bridging by parasitic boron clusters. Short‐time CVD of SiC increases the fiber surface roughness and doubles the ISS, but again the minicomposites are brittle, indicating the need to better modulate the resulting roughness and adjust the interphase. Finally, ammonia treatments have nitrided the fiber surface and increased the ISS by 12%. While the increase in interfacial bonding measured at the microscopic scale was small, this nitriding treatment did not embrittle the minicomposites at the macroscopic scale.

CURRENT LEADS FOR RESISTIVE CCCM HEATERS

The article justifies the necessity of taking into account the transient electrical resistance of the welding contact between the titanium current lead and the resistive element of the heater made of carbon-carbon composite material (CCCM) during its manufacturing.
 Carbon-carbon composite material possesses a unique set of technical characteristics that make it suitable as a structural material for manufacturing resistive heaters operating in the temperature range from 400°C to 2500°C in a vacuum or protective atmosphere. The use of CCCM heaters in the thermal chambers of electrothermal engines to convert electrical energy into thermal energy allows them to be employed for temperature measurement inside the engine's thermal chamber. The utilization of an integrated temperature assessment of the CCCM heater, which relies on the resistance change of the heater with increasing temperature and essentially involves measuring the electrical current passing through the heater, requires ensuring accurate values of both the electrical resistance of the heater itself and the electrical resistance at the point of contact with the current lead.
 The design of the heater has a particular feature, which is the need to supply electrical current to two lamellas of the resistive element of the CCCM heater, located on one side of the heater. For welding the joints between the titanium wire and the resistive element of the heater, TIG welding with a surface arc in an argon environment was applied, with argon being supplied between the welding point and the non-consumable tungsten electrode.
 Laboratory tests revealed that detachable connections of the titanium wire to the resistive element of the CCCM heater and separable connections (such as bolts, screws, and wedges) cannot meet the requirements for contact resistance stability for various reasons. Among non-detachable connections, only welded joints demonstrated stable electrical contact resistance characteristics.
 The electrical resistance of the heater with current leads should be 3.8±0.2 Ohms. The tolerance value for resistance is determined by several factors, including the physical properties of CCCM, the technology of mechanical processing, the method of applying protective coatings, the resistance of the welding joint, and others.
 During mechanical tests of the welding joint between the titanium wire and the heater, it was observed that the wire detachment from the heater occurs with residues of CCCM and a transitional layer of titanium carbide, which forms during welding and can contribute to additional electrical resistance of the heater. Thermal deformation of the CCCM heater in the welding zone does not occur.
 The results of the conducted research demonstrate that the installation of titanium current leads by welding increases the resistance value of the resistive element of the CCCM heater due to the chemical reaction between the titanium alloy and the resistive element, leading to the formation of an additional layer of titanium carbide. Therefore, the electrical resistance of the resistive element of the CCCM heater during its manufacturing, before welding two titanium wires for current leads, should be reduced, taking into account the transitional electrical resistance of the two welding contacts.

Highly selective and ultra-sensitive gas sensor based on Fe2O3/Ti3C2Tx MXene heterostructure for ppb-level n-butanol detection

The sensitive and rapid detection of toxic gases, particularly at concentrations as low as parts per billion (ppb), is crucial in preventing explosion and gas leakage accidents. Herein, we have developed a ppb-level n-butanol sensor by constructing a heterojunction structure through in situ growth of n-type oxide semiconductor Fe2O3 nanoparticles on two-dimensional layered carbide materials Ti3C2Tx MXene. The obtained results from that the Fe2O3/MXene-1% sensors display ultra-low detection limit, exhibiting a 1.31 response towards 70 ppb n-butanol. In addition, the Fe2O3/MXene-1% sensors show a remarkable response of 83.7 towards 100 ppm n-butanol at 150 °C, which represents a 22-fold improvement when comparison with the pure Fe2O3 sensors. The sensors also exhibit brilliant selectivity, reproducibility and excellent long-term stability. The remarkable enhancement in gas sensitive performance depends on Schottky heterojunctions formed between metal oxides and Ti3C2Tx MXene and the synergistic effect. The incorporation of MXene decreases materials’ resistance and enhances the carrier transfer rate. The design of this study provides a novel approach for achieving ppb-level n-butanol detection.

Comparative study on induction brazing of diamond with rare earth Nd-doped crystalline and amorphous Ni-based filler alloy

This essay aims to comparatively study the microscopic morphology and grinding properties of brazed diamonds with amorphous and crystalline filler alloy in the case of rare-earth Nd-doped modified Ni-based filler alloy. The results show that at the same content of Nd, Cr7C3 is mainly generated at the brazing interface of crystalline samples. In contrast, Cr27C6 is mainly generated at the brazing interface of amorphous samples. Amorphous solder material achieves a robust chemical metallurgical union, producing a dense and homogeneous carbide layer. The bonding strength between amorphous solder material and diamond is further enhanced. The addition of rare earth element Nd contributes greatly to the forming ability of amorphous filler alloy. Nd atoms in the amorphous solder material readily bond with Ni atoms, reducing the chemical corrosion of Ni atoms on diamonds and resulting in a lower degree of graphitization. When the amount of Nd added is 1.0 wt%, the morphology of amorphous filler alloy brazing diamond is more complete than the effect of the crystalline state, the degree of thermal damage is lower, and the surface of amorphous filler alloy brazing is smoother. Frictional wear experiments show that the amorphous filler alloy holds diamond better than the crystalline filler alloy, and the diamond specimens prepared with the amorphous filler alloy demonstrate a significantly superior grinding performance in comparison to the diamond specimens prepared with the crystalline filler alloy.

Accelerated thermal property mapping of TRISO advanced nuclear fuel

TRistructural ISOtropic (TRISO) fuel is a leading-edge nuclear fuel form representing a departure from the more traditional nuclear fuel forms utilized in the reactor fleet of today. Rather than a monolithic fuel pellet of uranium dioxide, integral fuel forms containing TRISO fuel are composed of thousands of microencapsulated uranium-bearing fuel kernels and individually coated with multiple layers of pyrolytic carbon and silicon carbide. These multilayered ceramic coatings serve as an environmental barrier to ensure radioactive and chemically reactive fission products are contained within the reactor fuel elements, but also participate in the transfer of heat generated in the nuclear fuel to the coolant – the primary purpose of a nuclear reactor. Since traditional thermal property measurement techniques, such as laser flash analysis, would be unable to resolve the thermal properties of the individual TRISO coating layers, a simplified frequency-domain thermoreflectance technique has been developed to rapidly map the thermal properties of TRISO particles. Using this technique, the thermal properties of TRISO particles have been mapped from room temperature up to 1000 °C to examine the spatial variation and temperature-dependency of the thermal properties within each layer. Additionally, spatial-domain thermoreflectance was used to examine the anisotropy of the thermal properties for each layer at different locations within a single TRISO particle, and across multiple TRISO particles to assess the intra- and inter-particle uniformity of thermal properties, respectively. To elucidate the underlying causes for the measured variations in thermal properties, scanning electron microscopy and Raman spectroscopy were used to examine variations in microstructure and chemical bonding within the different coating layers. Results from this work are then compared with previous examinations of TRISO fuel particles and microstructurally driven mechanisms for the variations in the measured thermal properties of the different carbonaceous layers are discussed.

Characterization of ductile nano-TiC dispersed V4Cr4Ti/RAFMs solid diffusion joint for nuclear fusion reactor application

Reduced activation ferrite/martensite (RAFM) steel and V4Cr4Ti alloy are candidate structural materials applicable for blankets with various coolants for fusion reactor. In order to combine their advantages, a solid-state diffusion bonding bimetallic plate was designed to provide for high-temperature strength and neutron-irradiation resistance from the vanadium alloy and corrosion-resistance from the steel. However, brittle intermetallic and carbide layers can be formed during the high-temperature diffusion process, which is detrimental to the mechanical properties of the joint. To understand the mechanisms for a ductile joint, the diffusion bonding was performed at different temperatures by hot isostatic pressing (HIP). Various methods were used for the interfacial analysis, together with shear mechanical test and Vickers hardness test across the interface. The interfacial intermetallics differ significantly from each other with different bonding temperatures. Brittle σ-(Fe, V) intermetallic and continuous V2C carbide layer could be avoided by optimizing the diffusion parameters. The joint bonded at 850 °C shows the optimal ductility with highest shearing strength value of 240 MPa, resulting from the synergetic effects. The dispersed TiC nanoparticles formed at interface would play an important role to improve the mechanical performances of the V4Cr4Ti/CLF-1 joint. Besides, no continuous thick carbides or σ- (Fe, V) layer, finer grains in the decarburization layer and the ultra-fine recrystallization grains of the vanadium alloy around the interface are all helpful for joint performance improvement.

Study on the structure and thermal properties of graphite/copper laminated composites assembled by Ti-containing active filler metals

The development of high-power and small-sized electronic components requires the emergence of heat management materials with high heat flux. Hence, Ti-containing filler was used to braze graphite film/Cu high heat flux composites. The microstructure and forming mechanism of joints were studied, the influence of temperature on joint formation was analyzed, and the influence of graphite volume fraction on the thermal properties of the composites were discussed. The results show that the main microstructure of graphite/copper joints are Cu(s,s), Ti6Sn5 and CuTi2. As the brazing temperature increases, the carbide layer (TiC) that affects the connection gradually thickens, from <0.5 μm at 800 °C to 3 μm at 850 °C, which deeply improve heat transfer of composite materials. The tensile properties of composites also increase with increasing temperature, maximum tensile strength 31.94 MPa can be obtained at 850 °C. Furthermore, the composites are proved to possess high heat flux during process of heat transfer, and the transfer rate was 1.77 times that of Cu, 3.72 times of Al. The temperature rise test carry out in hot bench intuitively demonstrating that the composites have faster heating rate. Al used 197 s to raise from 25 °C to 50.5 °C, Cu used 140 s, while 76.92 % graphite-contained composites only took 75 s in the same volume and experimental condition.

Microstructural and Mechanical Characterizations of Mo/W and Mo/Graphite Joints with BNi2 Paste

Brazing of Mo to W and to graphite is achieved using BNi2 paste (containing Ni, Cr, Si, and B). For the Mo/W or Mo/graphite joint, the joining area consists of a diffusion area and a brazing area. The diffusion area is composed of MoNi and Mo, which is formed by diffusion of the Mo substrate into the braze during brazing. The brazing area of the Mo/W joint contains Ni(ss) (solid solution), Cr(ss), Ni3B, CrB, and Ni4W, while the brazing area of the Mo/graphite joint mainly comprises Ni(ss), MoNi, Ni3B, and CrB. A continuous chromium carbide layer is formed at the brazing area/graphite interface in the Mo/graphite joint due to the reaction of Cr in the BNi2 braze with the graphite. Nanoindentation measurements of the joints show that the diffusion area exhibits the highest hardness and elastic modulus in the joints. The shear strengths of the Mo/W and Mo/graphite joints are 58.1 ± 16.0 and 13.0 ± 4.0 MPa, respectively. The Mo/W and Mo/graphite joints fracture after the shear tests in the W and graphite sides, respectively, near the joining area, indicating that both fractures are caused by the stress concentration in the corresponding areas.

Design of smart transforming metal ceramic multilayers

Novel metal ceramic multilayer composites with the ability to phase transform into a single phase ultra-high temperature ceramic are described. These materials offer enhanced low-temperature fracture toughness and reliability without sacrificing high-temperature mechanical properties by eliminating the metal reinforcement layers upon reaching temperatures sufficient for the activation of carbon diffusion. At low temperatures, these materials are practically indefinitely stable because of the high activation energy for carbon diffusion in the carbide layers that control the phase transformation kinetics. Here, knowledge of the overall thermodynamics, i.e., carbon content, is combined with prediction of phase transformation kinetics and toughening in the limit of small-scale yielding to characterize the design space of these novel composites. It is proposed that the ability to control thermodynamic and mechanical properties of the post-transformation ceramic via selection of metal-to-ceramic layer ratios makes these novel composites an excellent alternative to current methods for reinforcement of ultra-high temperature ceramics.

Magnetic MXene: A Machine-Learning Model With Small Data

MXenes, comprising of atomically thin layers of transition metal nitrides, carbides, and carbonitrides, exhibit properties which are not found in their corresponding bulk materials. Interestingly, because of the presence of transition metal, MXenes may also provide the candidate materials for observing low-dimensional magnetism. This can be of interest to various applications such as data storage, electromagnetic interference shielding, and spintronic devices. Here, we focus on the magnetic MXenes, which are only a few in number out of known MXenes. We propose machine learning models to predict the magnetic moments of the MXenes and to classify the MXenes based on their chemical stability. Using these models, we propose four new chemically stable MXene materials having a potentially high magnetic moment.

Investigations of Nanoscale Columnar AlxGa1-xN/AlN Heterostructures Grown on Silicon Substrates with Different Modifications of the Surface

The growth of nanoscale columnar AlxGa1-xN/AlN heterostructures on the surface of silicon substrates using plasma-activated nitrogen molecular-beam epitaxy was investigated in this work. Silicon substrates include atomic-smooth cSi substrate, Si substrate with a transition layer of porous silicon porSi/cSi and a hybrid substrate involving a silicon carbide layer grown with matched substitution of the atoms on the surface of porous silicon SiC/porSi/cSi. A complex analysis performed using a set of structural and spectroscopic techniques demonstrated that the epitaxial growth of the nuclear AlN layer on all types of the substrates in a N-enriched environment resulted in the formation of AlxGa1-xN/AlN heterostructures with a Ga-polar surface, which was realized only on the SiC/porSi/cSi substrate. The layer of AlxGa1-xN on cSi and porSi/cSi substrates was in the state of disordered alloy with an excess of gallium atom content. It was shown that a great difference in the lattice parameters of a substrate–film pair resulted not only in the appearance of a number of various defects but also in a considerable effect on the chemical process of the formation of the alloys, in our case, the AlxGa1-xN alloy. It was shown that nanoscale columns of AlxGa1-xN formed on SiC/porSi/cSi substrate were inclined relative to the c-axis, which was connected with the features of the formation of a SiC layer by the matched substitution of the atoms on the porous Si substrate, resulting in the formation of the inclined (111) SiC facets at the boundary of the (111) Si surface and pores in Si. Optical studies of the grown samples demonstrated that the optical band-to-band transition for the AlxGa1-xN alloy with Eg = 3.99 eVB was observed only for the heterostructure grown on the SiC/porSi/cSi substrate. A qualitative model is proposed to explain the difference in the formation of AlxGa1-xN layers on the substrates of cSi, porSi/cSi and SiC/porSi/cSi. The results obtained in our work demonstrate the availability of using SiC/porSi/cSi substrates for the integration of silicon technology and that used for the synthesis of nanoscale columnar AlxGa1-xN heterostructures using plasma-activated molecular-beam epitaxy with a nitrogen source.

Effective Thermal Properties of a HTS Transition Edge Bolometer for High‐Flux Neutron Detection

AbstractMany applications require monitoring of increasingly high neutron flux levels. Pre‐neutron characterization is performed of a superconducting transition edge bolometric device, sensitive to neutrons by an enriched boron carbide (10B4C) layer. Heat from the absorption of neutrons is simulated using an attenuated laser, while the detector is cooled to the critical temperature, Tc. Frequency dependent (4–25 Hz) and constant input power measurements are performed on a 10B4C‐coated and a non‐coated pixel. Results are used to fit a two lumped element thermal model. The effective specific heat is highly dependent on the input pulse duration due to the interconnected stack structure. For modulated pulses, the active volume in the thermal circuit is the full depth of the substrate in the area under the pixel. For constant power input, a large portion of the substrate is heated and the interface conductivities to the cold finger are found to be important. The detectivity is D* = 3.5 × 108 , and is only slightly lower than similar detectors. Understanding the dynamics of the detector better and using neutron excitation, it is expected that optimizations can lead to an equally good detector for cold to thermal neutrons at flux levels &gt;106 n cm−2s−1.

Comparative studies of nanoscale columnar AlxGa1-xN/AlN heterostructures grown by plasma-assisted molecular-beam epitaxy on cSi, porSi/cSi and SiC/porSi/cSi substrates

Problems of the growth of nanoscale columnar AlxGa1-xN/AlN heterostructures on hybrid substrates involving porous silicon and silicon carbide layers by molecular beam epitaxy technique with plasma-activated nitrogen are discussed in this study. The epitaxial growth of nanoscale columnar AlxGa1-xN/AlN heterostructure is shown to be specified by the layer of silicon carbide, which is formed by atomic substitution technique, and a porous silicon sublayer predetermines the oriented growth of SiC. The performed complex of structural-spectroscopic analysis demonstrated that epitaxial growth of the nuclear AlN layer on all types of the substrates in N-enriched conditions resulted in the formation of AlxGa1-xN/AlN heterostructures with Ga-polar surface. At the same time it was found that the layer of ordered AlxGa1-xN alloy was formed only on the hybrid SiC/porSi/cSi substrate. The layer of AlxGa1-xN on the substrates of cSi and porSi/cSi is present in the state of disordered alloy with an excess content of gallium atoms. Nanocolumns of AlxGa1-xN/AlN grown on the hybrid SiC/porSi/cSi substrate have two types of preferential azimuthal orientation that affects not only their structural and optical properties but also the value of elastic deformation in the heterostructure nanoscale layers. For the first time, azimuthal dependence of intensity of E1(TO) and E2high photon modes was detected in the Raman spectra. The observed periodicity angle in micro-Raman scattering coincides with the characteristic swivel of nanoscale columns of AlxGa1-xN/AlN around c-axis according to the data of XRD pole figure measurements. Results obtained in our work show promising capabilities in the use of SiC/porSi/сSi substrates for integration of silicon technology and technology of synthesis of the nanoscale columnar AlxGa1-xN heterostructures by molecular-beam epitaxy with plasma-activated nitrogen.

Effects of Interfacial Electron Transport on Field Electron Emission from Carbon Nanotube Paste Emitters.

Field electron emission from carbon nanotubes (CNT) is preceded by the transport of electrons from the cathode metal to emission sites. Specifically, a supporting layer indispensable for adhesion of CNT paste emitters onto the cathode metal would impose a potential barrier, depending on its work function and interfacial electron transport behaviors. In this paper, we investigated the supporting layer of silicon carbide and nickel nanoparticles reacted onto a Kovar alloy (Fe-Ni-Co) cathode substrate, which has been adopted for reliable CNT paste emitters. The X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and electrical conductivity measurements showed that the reaction of silicon carbide and nickel nanoparticles on the Kovar metal strongly depends upon the post-vacuum-annealing conditions and can be classified into two procedures of a diffusion-induced reaction (DIR) and a diffusion-limited reaction (DLR). The prolonged annealing at 750 °C for 5 h before the main annealing of the CNT paste emitters at 800 °C for 5 min led to the DIR that has enhanced the Ni silicide phase and a lower potential barrier for the interfacial electron transport, resulting in increased and weakly temperature-dependent field electron emission from the CNT paste emitters. On the other hand, the DLR with only the main anneal of the CNT paste emitters at 800 °C for 5 min gave rise to a higher potential barrier for the electron transport and so lower and strongly temperature-dependent field electron emission. From the results of the interfacial electron transport for the DIR and DLR mechanisms in the CNT paste emitters, we concluded that the ambient temperature dependency of field electron emission from CNT tips in the moderate range of up to 400 °C, still controversial, is mainly attributed to the supporting layer of the CNT emitter rather than its intrinsic electron emission.

Mechanism of Formation of Vanadium Carbide Layers on Carbon Steel by Powder Packed Method

Mechanism of Formation of Vanadium Carbide Layers on Carbon Steel by Powder Packed Method

Tribological Properties of Several Surface-Modified Piston Rings Under Extreme Conditions

Abstract This article explores the performance of different commercial piston rings when matched with a boron-phosphorus (BP) alloy cast iron cylinder liner, specifically in high-power density diesel engines. The focus is on the friction, wear, and scuffing characteristics. An interrupted wear test was conducted under lean oil conditions to study the scuffing behavior of plated Cr-diamonds coating (GDC) and diamond-like carbon coating (DLC). The findings reveal that DLC coatings exhibit superior tribological properties, displaying low friction coefficients and wear loss at temperatures of 150 °C and 240 °C. In contrast, GDC coatings demonstrate relatively poor performance. Additionally, the DLC coating demonstrates excellent scuffing resistance, as no material transfer was observed for up to 77 min, even without lubrication. The interrupted scuffing test reveals that the scuffing process undergoes a stable wear stage, followed by a sudden drop and subsequent increase in friction force, ultimately resulting in scuffing when the BP cylinder is paired with GDC. On the other hand, although the frictional force of DLC initially increases after a brief decline, no significant adhesive wear is observed. This can be attributed to the formation of a tribo-chemical layer of carbides, which effectively prevents scuffing. In comparison to traditional methods of postwear morphology and analysis, our proposed interrupted scuffing tests offer enhanced capabilities for evaluating the wear condition of friction pairs at various time intervals during the oil depletion process. This novel approach introduces a new paradigm for investigating wear patterns in different friction pairs.

Effects of WC ratios on bead size and crack initiation in forming WC-Co cemented carbides by the laser metal deposition

Enhancing the durability of molds, jigs, and tools is crucial for the industry, and one approach to achieve this is by forming a metallic layer with high hardness on their surfaces. Metallic layers with high hardness can be formed through laser metal deposition (LMD), which is one of the additive manufacturing processes, using cemented carbide powder. However, crack initiation typically occurs inside cemented carbide layers formed by the LMD. Therefore, achieving a cladding process for cemented carbide layers without cracks is desired for practical applications. In this study, the effects of tungsten carbide (WC) ratios in WC-Co cemented carbide granulated powder on formed bead size and crack initiation during the LMD processing were investigated. The number of cracks generated during the LMD processing was evaluated using an acoustic emission (AE) technique. The number of burst-type AE signals generated was counted as the number of cracks. Seven types of WC-Co cemented carbide granulated powders with WC ratios ranging from 30.5 to 92 mass% were prepared. Beads were formed using each powder through the LMD, with AE signals being measured. In the case of a WC ratio of 42.9 mass% or less, no crack was observed. On the other hand, cracks were observed when the WC ratio was 53.9 mass% or greater, and the number of cracks increased with an increase in the WC ratio.

Effect of a silicon dioxide diffusion barrier layer and its sublimation on the migration of strontium implanted into SiC

Thin film diffusion barriers are inevitable in nuclear reactors for preventing the release of radioactive waste products. The combination of chemical stable silicon carbide (SiC) and silicon oxide (SiO2) layers has been considered being beneficial, thus, we studied the migration and stability of strontium implanted SiC upon annealing, owing an additional SiO2 surface layer. Our investigations show that annealing at 1100 and 1200 °C retained the Sr atoms in comparison to pure SiC and induced strong strontium segregation at the SiO2/SiC interface and SiO2 surface. However, this enhanced the sublimation of the SiO2 layer, while pure SiO2 layers (i.e., without impurities) showed no sublimation after annealing under the same conditions. On the other hand, higher temperatures at 1300 and 1400 °C, resulted also in significant sublimation of the pure SiO2 layer.

Wetting and spreading of NiTi melt on graphite and carbon felt

Experiments were carried out on the wetting and spreading of the nitinol melt over the polished surface of high-density pure graphite. The furnace heater and the dispenser from which the melt was extruded were also made of graphite of the same quality. The measurements were carried out in vacuum of 10−3 Pa at a temperature close to the melting point and higher, up to 1430 °C. High-speed filming of the transferred drop was used simultaneously with high-speed thermal imaging. As a result, the kinetics of the spreading of the nitinol melt over the graphite surface was obtained, and the surface tension was also measured by the pendant drop method. The dissolution of carbon in the melt prevents the formation of a barrier layer of titanium carbide. Electron microscopic studies confirmed the formation of a dense layer of titanium carbide on the contact surface. An experiment was carried out on the melting of nitinol on carbon felt at a temperature of 1350 °C. It is shown that nitinol's drop on felt with a density of about 100 kg/m3 (porosity 93%) does not impregnate into the felt, retains volume and shape for more than 15 min. This indicates that carbon felt or cloth may be good candidates for lining materials.

Adhesive and tensile properties of diamond(001)/TiC(111) interfaces: A first-principles investigation

Since a nanometer-thick carbide layer will be indispensably produced on diamond to ensure wettability with metallic parts, the interfacial properties of diamond/carbide directly affect the service performance of diamond devices. Herein, first-principles calculations were performed to investigate the interfacial properties and tensile responses of diamond(001)/TiC(111) interfaces. Taking into account Ti- and C-termination of TiC(111), and interfacial stacking of hollow- and top-site, four interface models were established. The results showed that Ti-termination could only be stacked by hollow-site. The analysis of energy and electronic structure suggested that hollow-site or C-termination favored to produce a more stable interface, attributing to stronger interfacial C-C covalent bonds and even the additional ionic attraction from Ti atoms, which enhanced the bonding strength significantly. Furthermore, the tensile simulations indicated cleavage always ignited from Ti-C bonds, of which along the interface for Ti-termination and within the TiC for C-termination. Growing C-terminated TiC could greatly improve interfacial stability, but at the expense of mechanical strength. This owed to the homogenization of C-termination by diamond surface. The results provided an atomic insight to characterize the structure and bonding of diamond/TiC interfaces, laying the foundation for developing high-performance diamond devices.