Carbide Materials Research Articles

A Systematic Study on Bio-Based Hybrid Aerogels Made of Tannin and Silica.

Tannin-silica hybrid materials are expected to feature excellent mechanic-chemical stability, large surface areas, high porosity and possess, after carbothermal reduction, high thermal stability as well as high thermal conductivity. Typically, a commercially available tetraethoxysilane is used, but in this study, a more sustainable route was developed by using a glycol-based silica precursor, tetrakis(2-hydroxyethyl)orthosilicate (EGMS), which is highly water-soluble. In order to produce highly porous, homogeneous hybrid tannin-silica aerogels in a one-pot approach, a suitable crosslinker has to be used. It was found that an aldehyde-functionalized silane (triethoxysilylbutyraldehyde) enables the covalent bonding of tannin and silica. Solely by altering the processing parameters, distinctly different tannin-silica hybrid material properties could be achieved. In particular, the amount of crosslinker is a significant factor with respect to altering the materials’ properties, e.g., the specific surface area. Notably, 5 wt% of crosslinker presents an optimal percentage to obtain a sustainable tannin-silica hybrid system with high specific surface areas of roughly 800–900 m2 g−1 as well as a high mesopore volume. The synthesized tannin-silica hybrid aerogels permit the usage as green precursor for silicon carbide materials.

Theoretical calculation and analysis of new rare earth cemented carbide based on first-principles

Cemented carbide is widely used as tool material since it has a series of excellent properties such as high hardness, wear resistance, good strength and toughness. The addition of rare earth elements can improve the high temperature crack resistance and deformation resistance of WC-Co cemented carbide. In this paper, a WC-Co model was established based on the first-principles method. The energy of the structure doped with rare earth elements in four positions is calculated to determine the most stable structure, and then carry out the model optimization. The elastic constants, electronic properties, and thermodynamic properties of WC-Co before and after doping were calculated. Furthermore, the elastic properties of the two materials was analyzed by comparing the parameters of Young's modulus and Poisson's ratio. Their thermodynamic properties were explored by calculating the enthalpy, entropy, free energy and specific heat capacity of the two structures. The results shows that the comprehensive performance of cemented carbide materials doped with rare earth elements is significantly improved.

Models for the behavior of boron carbide in extreme dynamic environments

AbstractWe describe models for the behavior of hot‐pressed boron carbide that is subjected to extreme dynamic environments such as ballistic impact. We first identify the deformation and failure mechanisms that are observed in boron carbide under such conditions, and then review physics‐based models for each of these mechanisms and the integration of these models into a single physics‐based continuum model for the material. Atomistic modeling relates the composition and stoichiometry to the amorphization threshold, while mesoscale modeling relates the processing‐induced defect distribution to the fracture threshold. The models demonstrate that the relative importance of amorphization and fracture are strongly dependent on the geometry and impact conditions, with the volume fraction of amorphized material being unlikely to be significant until very high velocities (~3 km/s) are reached for geometries such as ball impact on plates. These connections to the physics thus provide guidelines for the design of improved boron carbide materials for impact applications.

Effects of Different Substrates on the Formability and Densification Behaviors of Cemented Carbide Processed by Laser Powder Bed Fusion

Cemented carbide materials are widely applied in cutting tools, drill tools, and mold fabrication due to their superior hardness and wear resistance. Producing cemented carbide parts via the laser powder bed fusion (L-PBF) method has the advantage of fabricating complex structures with a rapid manufacturing speed; however, they were underdeveloped due to their low density and crack formation on the blocks. This work studied the effect of different substrates including 316L substrates, Ni200 substrates, and YG15 substrates on the forming quality of WC-17Co parts fabricated by L-PBF, with the aim of finding the optimal substrate for fabrication. The results revealed that the Ni200 substrates had a better wettability for the single tracks formation than other substrates, and bonding between the built block and the Ni200 substrate was firm without separation during processing with a large range of laser energy inputs. This guaranteed the fabrication of a relatively dense block with fewer cracks. Although the high laser energy input that led to fine crack formation on the blocks formed on the Ni200 substrate, it was found to be better suited to restricting cracks than other substrates.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ ЭЛЕКТРОИСКРОВОГО ФОРМИРОВАНИЯ ИЗНОСОСТОЙКИХ ПОКРЫТИЙ НА ОБРАБАТЫВАЕМЫХ ПОВЕРХНОСТЯХ

The article considers a new direction in optimizing the process of plasma hardening of the surfaces of cutting elements of agricultural machines based on the use of electric spark discharge energy. (Research purpose) The research purpose is in optimizing the technological process of hardening the surfaces of cutting elements of agricultural machines by the method of electric spark alloying of carbide material elements. (Materials and methods) A device under RF patent No. 2655420, developed by the scientific supervisor of the subject S. N. Sharifullin, was used for electric spark alloying. A tungsten-cobalt rod with a diameter of 4 millimeters, consisting of 94 percent tungsten and 6 percent cobalt, was used as the electrode material for this case. The processed sample of 65G steel, which is the main material of the working bodies of tillage equipment. The physical and chemical properties of the samples were studied with a scanning electron microscope EVO 50 XVP from Zeiss. (Results and discussion) After the electric spark treatment of the alloyed elements, there were about ten, while their spectra also appear at different irradiation energies. The alloyed elements in the surface layer are not only separate, but also in the form of compounds with other elements. Such alloying elements as carbon, cobalt and tungsten appeared in a noticeable amount in the surface layer. Electric spark treatment allows increasing the microhardness of the surfaces of cutting elements of tillage equipment up to three times. (Conclusions) When developing a mathematical model of the electric spark formation of wear-resistant coatings on the treated surfaces, it is necessary to use the energy conservation equations of the electron gas, the Maxwell equations, the continuity and momentum equations. The complex solution of these equations makes it possible to obtain the required output parameters depending on the input ones.

Recent Advances in Reactive Ion Etching and Applications of High-Aspect-Ratio Microfabrication.

This paper reviews the recent advances in reaction-ion etching (RIE) for application in high-aspect-ratio microfabrication. High-aspect-ratio etching of materials used in micro- and nanofabrication has become a very important enabling technology particularly for bulk micromachining applications, but increasingly also for mainstream integrated circuit technology such as three-dimensional multi-functional systems integration. The characteristics of traditional RIE allow for high levels of anisotropy compared to competing technologies, which is important in microsystems device fabrication for a number of reasons, primarily because it allows the resultant device dimensions to be more accurately and precisely controlled. This directly leads to a reduction in development costs as well as improved production yields. Nevertheless, traditional RIE was limited to moderate etch depths (e.g., a few microns). More recent developments in newer RIE methods and equipment have enabled considerably deeper etches and higher aspect ratios compared to traditional RIE methods and have revolutionized bulk micromachining technologies. The most widely known of these technologies is called the inductively-coupled plasma (ICP) deep reactive ion etching (DRIE) and this has become a mainstay for development and production of silicon-based micro- and nano-machined devices. This paper will review deep high-aspect-ratio reactive ion etching technologies for silicon, fused silica (quartz), glass, silicon carbide, compound semiconductors and piezoelectric materials.

Stacking Sequence, Interlayer Bonding, Termination Group Stability and Li/Na/Mg Diffusion in MXenes

A versatile group of 2D carbide materials from the past decade, MXenes, have attracted attention for their rich chemistry and wide range of properties. The perhaps best known MXene, namely, Ti3C2Tx, has been observed to stack in two distinct ways, and simulations show that this influences interlayer bonding energy and Li diffusion. In this DFT study, six types of Ti3C2T2 interlayer bonds resulting from O, F, and OH termination groups are assessed with respect to stability. It is shown that OH termination groups are highly stable up to 50% coverage, but unstable for higher coverage. A model to predict stacking type based on termination group chemistry shows that the degree of hydrogen bonding is the deciding factor. The model is also tested on V2CT2 and Zr3C2T2, giving similar results to those of Ti3C2T2. By calculating migration barriers for Ti3C2O2, we show that Li, Na, and Mg have orders of magnitude faster diffusion in the stacking favored by hydrogen bonds. XRD patterns calculated for both stackings show they are close to indistinguishable, highlighting the need for caution when classifying stacking.

Erosion wear characteristics of cemented carbide for mud pulser rotor

Mud pulser is the most commonly used Measurement While Drilling(MWD) instrument for downhole data transmission to the surface. The rotor of the key component of the mud pulser is made of cemented carbide material. Under the action of high speed mud erosion containing solid phase, the rotor will produce erosion wear and reduce the quality of signal transmission. To explore the erosion wear mechanism of rotor carbide in mud containing solid phase particles, the influences of different erosion angles and different erosion abrasive sizes on the erosion wear properties of cemented carbides were studied by taking quartz sand as erosion abrasive. By means of surface profilometer, scanning electron microscope (SEM) and energy spectrum analysis (EDS), the erosion wear mechanism of cemented carbide was revealed. The experimental results show that the erosion wear rate increases gradually with the increase of erosion angle. When the erosion angle is 90°, the maximum average erosion rate of WC-5Co, WC-6Co and WC-10Co cemented carbides is 2.39%, 2.42% and 3.22%, respectively. With the increase of the abrasive particle size, the erosion wear rate of the material increases first and then decreases. When 100–200 um, the maximum average erosion rates of WC-5Co, WC-6Co and WC-10Co are 1.84%, 1.98% and 2.48%, showing a significant “particle size effect”. At low erosion angle, the wear mechanism is furrow and cutting mark, while at high erosion angle, the wear mechanism is pit. The erosion wear mechanism of small particle size abrasives is that a large area of surface layer falls off in the erosion area. The erosion wear mechanism of large particle size abrasive is the material loss in the erosion pit in the erosion area.

Optoelectronics of Color Centers in Diamond and Silicon Carbide: From Single‐Photon Luminescence to Electrically Controlled Spin Qubits

AbstractColor centers in diamond, silicon carbide, and related materials have recently emerged as one of the most promising platforms for quantum technology applications. These optically active point defects in the crystal lattice demonstrate outstanding optical and spin properties at room and even higher temperatures, which can hardly be achieved using other quantum systems. For a long time, the host material was considered only as a mechanical carrier of color centers, and the fact that it is a semiconductor and, therefore, can contain high densities of electrons and holes, was ignored. However, recent studies have demonstrated that color centers can exchange electrons and holes with the valence or conduction bands of the host material, which enables novel functionalities, ranging from ultrabright electrically driven single‐photon sources to protected quantum memories. This review summarizes recent advances in understanding this interaction.

Recent Progress in the Nanoskiving Approach: A Review of Methodology, Devices, and Applications

AbstractNanoskiving is a unique nanomanufacturing method that can be used to cut out nanostructures directly with well‐controlled shapes and sizes. Over the past 10 years, nanoskiving techniques have evolved in terms of optimization of the sectioning parameters and development of the transfer and alignment approaches. In addition, the range of compatible materials for nanoskiving is expanding via combination of the technique with other bottom–up and top–down methods; for example, soft materials such as block polymers and hard materials such as cemented carbide and semiconductor materials are now able to be nanosized successfully, despite previously being considered incompatible with nanoskiving technology. The preparation of these structures by the nanoskiving method opens a convenient door to verification of the application of this technique to device miniaturization in fields including optics, electrochemistry, electronics, and biology. This review outlines the advances made in nanoskiving, including those in the fabrication process, the development of suitable applications, and the challenges and opportunities for future exploration of the technology.

Finite-element-method study of tilt mirrors without PZTs using different clamping methods under laser irradiation

Tilt mirrors play a fundamental role in correcting aberrations in adaptive optics systems. To analyze the influence of clamping methods and materials on temperature rising, deformations and high-order aberrations of tilt mirrors without PZTs during the evaluation of laser irradiation of multilayer coatings, a finite-element model of tilt mirror with a diameter of 100 mm and thicknesses of 12.5 mm was constructed. The deformation and high-order aberrations were simulated after applying a laser to the mirrors. The appearance of peak-to-valley and high-order aberrations became more significant as the tilt mirror was supported on the edge at 3 points 120° apart. Using 3 points at the back and 3 points on the side 120° apart with polytetrafluoroethylene (PTFE) protection clamping lessened the effect, and the PV was only 0.0828 µm. The corresponding 65th-order Zernike coefficients were lower, so the clamping approach is ideal for fixing the tilt mirror for evaluating the multilayer coatings. Also, the temperature rising and thermal deformation of tilt mirrors made from various materials under laser irradiation were calculated. The results show that the tilt mirror made of ultra-low expansion microcrystalline glass had the highest temperature rising and the lowest thermal deformation. The temperature rising and PV was 10.56 ℃ and 0.004 µm, respectively. Beryllium and silicon carbide materials are suitable for increasing the resonance frequency and reducing the weight of tilt mirrors. These results are also useful for designing the clamping methods of large size folding mirror, telescope fast steering mirror and small scanner mirror, etc.

Plasma way to obtain ultrafine iron and aluminum oxides

The paper deals with two plasma-chemical synthesis installations based on alternating cur-rent plasma torches with power up to 30 kW, which can be used for production of ultrafine (nanosized) oxide and carbide materials. Some results obtained during experimental studies on the production of ultrafine powders of metal oxides (iron and aluminum) are presented.

Failure analysis and improvement of the tribological performance of sliding bearing tribopair in integrated energy recovery-pressure boost device

Integrated rotary energy recovery-pressure boost device (IERPBD) is the essential component in seawater reverse osmosis (SWRO) desalination systems. And sliding bearing pair is the vital tribopair in the IERPBD, which guarantee the reliability of the device. However, the polyetheretherketone (PEEK) bearing in the IERPBD occurred early failure during the pre-experiment. To solve this problem, this paper firstly analyzed the reasons and mechanisms of sliding bearing early failure, which suggested that it was attributed to the low elasticity modulus and poor tribological performance of PEEK. Moreover, several improved “hard-to-hard” material combinations were proposed and screened through wear and friction experiments, and found that the WC-6Ni (YN6X)/silicon carbide (SiC) material combination has reasonable physicochemical properties and excellent tribological performance. Finally, the sliding bearing made of YN6X/SiC was equipped in IERPBD to carry out experiments under real working conditions to verify the performance of proposed material combination. The results indicated that YN6X/SiC sliding bearing pair could guarantee the continuous and stable operation of IERPBD, and effectively solve the sliding bearing failure problem.

Fermiology of two-dimensional titanium carbide and nitride MXenes

MXenes are a family two-dimensional transition-metal carbide and nitride materials, which often exhibit very good metallic conductivity and are thus of great interest for applications in, e.g., flexible electronics, electrocatalysis, and electromagnetic interference shielding. However, surprisingly little is known about the fermiology of MXenes, i.e., the shape and size of their Fermi surfaces, and its effect on the material properties. One reason for this may be that MXene surfaces are almost always covered by a mixture of functional groups, and studying Fermi surfaces of disordered systems is cumbersome. Here, we study fermiology of four common Ti-based MXenes as a function of the surface functional group composition. We first calculate the effective band structures of systems with explicit mixed surfaces and observe gradual evolution in the filling of the Ti-d band and resulting shift of Fermi level. We then demonstrate that these band structures can be closely approximated by using pseudohydrogenated surfaces, and also compare favorably to the experimental angle-resolved photoemission spectroscopy results. By modifying the pseudohydrogen charge we then proceed to plot Fermi surfaces for all systems and extract their properties, such as the Fermi-surface area and average Fermi velocity. These are in turn used to evaluate the electrical conductivity with the relaxation time fitted to experimentally measured conductivities.

Surface generation of tungsten carbide in laser-assisted diamond turning

The removal mechanism of conventional cutting and in-process-heat laser-assisted cutting (In-LAC) of binderless polycrystalline tungsten carbide (WC) material is studied through systematic numerical analysis and experimental investigation. The proposed In-LAC model considers the accumulated thermal effect and the laser in-process-heat thermal boundary condition simultaneously. Results of molecular dynamics (MD) analysis are remarkably consistent with the experimental results qualitatively. The high-temperature nanoindentation test reveals the improved machinability of WC at an elevated temperature and provides a theoretical basis for cutting force reduction. A small Young's modulus measured at an elevated temperature presents a large elastic recovery value for the In-LAC model. The critical depth of no observed surface cracks of binderless WC increases from 26.6 nm to 106.3 nm, which can be attributed to in-process laser assistance. Furthermore, the In-LAC method is beneficial to avoid subsurface crystal bending and reduce subsurface damage in the MD model and the taper cutting sample subsurface. The existence of the laser annealing effect during the In-LAC process is directly proven by binderless WC cross-section transmission electron microscopy (TEM). According to the simulation analysis results and diamond turning chip morphology, the optimal laser power for polycrystalline WC ranges from 10 W to 15 W, which facilitates obtaining the surface finish of 4.66 nm in Sa and significantly improving the tool life.

Development of W–ZrC composite coating on graphite by a TIG-aided surface cladding process

In this study, a W–ZrC composite coating was applied on graphite substrate by a novel TIG-aided cladding process. The obtained overlay was uniform exhibiting no crack and discontinuity. In-situ reaction between WC and ZrO2 powders promoted by the heat of the TIG source resulted in overlay formation. To investigate and compare the effect of TiC and Co addition on composite microstructure and functionality, TiC and Co powders were added to WC powder. The phase formation, microstructure, adhesion, microhardness and toughness of the coating were the targets of the examinations and characterizations. The cross-sectional image of the coatings indicated a desired metallurgical bonding at the clad/substrate interface. The examined microhardness and toughness values of the composite coating with pure WC were 1700 HV and 4.7 MPam, respectively. These values were 2500 HV and 4 MPam for the sample containing TiC and Co additives. Extensive formation of solid solution between carbide materials and liquid phase formation by W and Co in the composite coating containing TiC and Co led to enhancement of the mechanical performance of the latter. Meanwhile, the improved resistance of the graphite against the oxidation and ablation is expected in presence of the composite clad layer in contrast to the bare graphite sample.

Analysis of the impact factors from the friction stir welding process for dissimilar butt joints between semi-solid cast aluminum 356 and AISI 1018 carbon steel

This research aimed to study the impacts of three different rotation speeds of 710, 1000, and 1400 rpm and three welding speeds of 40, 56, and 80 mm·min-1, on dissimilar butt joints between semi-solid aluminum 356 and AISI 1018 carbon steel. Welding tools were made from tungsten carbide material, and the offset was 0 mm. It was found that an increase in the rotation speed and welding speed caused accumulated heat, which led to the appropriate changes in the metallurgical structure. The rotation speed and welding speed factors had the impact on the greater blending of the two metals at the SZ zone. A larger amount of semi-solid aluminum 356 infiltrated into the AISI 1018 carbon steel when the rotation speed and welding speed increased. The findings showed that the most influencing factors on the average tensile strength at the weld lines were the rotation speed of 1000 rpm and the welding speed of 56 mm·min-1. The experiment in this study showed the maximum average tensile strength of 139.9 MPa and the average hardness value of 264.5 HV as the highest hardness value at the welding rotation speed of 1400 rpm and the welding speed of 80 mm·min-1.

Grinding efficiency and profile accuracy of diamond grinding wheels dressed with wire electrical discharge conditioning (WEDC)

Super abrasive diamond grinding wheels are the most promising tools for the precision machining of advanced ceramics and carbide materials. However, the efficiency of conventional conditioning of these tools is limited owing to high dressing tool wear, long process time, low form flexibility, and induced damage to the abrasive grains. Wire electrical discharge machining (WEDM) is an alternative method for conditioning of superabrasive grinding wheels with electrically conductive bonding materials. In this study, cylindrical plunge grinding of an alumina ceramic with a resin-bonded diamond grinding wheel is investigated. The assigned type of resin bond contains copper particles and is accordingly electrically conductive for wire electrical discharge conditioning (WEDC). Conventional (mechanical) and WEDC methods are used for generating the same profile on two similar diamond grinding wheels. As a result, the specific grinding energy was reduced up to 26% and 29% during rough and finish plunge grinding, respectively. Reduced specific grinding energy and forces, along with more effective grain protrusion and sharpness by using WEDC for profiling of grinding wheels, have contributed positively to the ground surface conditions despite the relatively rougher wheel surface topography in comparison to the conventional profiling. The more considerable reduction in the mean roughness depth (Rz) than in the arithmetical mean roughness value (Ra) (11% smaller Rz values in WEDC versus mechanical conditioning) verifies that the workpiece surface underwent less surface degradation in case of WEDC because of smaller grinding forces. Furthermore, the profile wear behavior of the workpiece ground with the WED conditioned grinding wheel was superior to the conventionally conditioned one.

Selective laser sintering in reactive atmospheres: Towards in-situ synthesis of net-shaped carbide and nitride ceramics

Selective laser reaction sintering techniques (SLRS) were investigated to produce near net-shape non-oxide ceramic materials that were previously incompatible with powder-bed fusion additive manufacturing (AM) methodologies. Specifically, reaction-bonded layers of carbide and nitride materials (Cr3C2 and CrN) were fabricated using SLRS from a model system of Cr and Cr2O3 precursor materials. Varied particle sizes (<5–45 µm) were simultaneously chemically-converted and reaction bonded into layers during selective laser processing in 100 vol% CH4 or NH3 gas. For each precursor material, factors such as particle size, chemistry, optical properties, and microstructure were investigated using quantitative phase characterization and microstructural imaging to understand important aspects of carbide and nitride phase formation within an AM context. SLRS processing of metal or metal oxide precursor systems produced yields up to 100 wt% total for carbide formation and 100 wt% total for nitrides during reactive processing. However, when either metal or metal oxide precursor was processed by itself, the simultaneous synthesis and reaction bonding approach resulted in volumetric changes during in-situ gas-solid conversion that adversely affected layer microstructure. To circumvent the internal stresses that accompanied volumetric changes induced from conversion of the metal (which expands during conversion) and the metal oxide (which contracts), we demonstrate an alternative method for the production of near-net shape carbide and nitride materials for AM. By combining optimized ratios of metal/metal oxide precursors for processing in CH4 or NH3 reactant gas, the novel precursor formulations produced undistorted, crack-free refractory ceramic layers with sub-millimeter spatial resolution and viable layer thickness for powder bed fusion-AM. The results not only demonstrate the formation of near net-shape carbides and nitrides using AM-compatible techniques but suggest that transition metal carbide and nitrides may be compatible with AM processing even though they cannot be processed using more traditional laser-assisted AM approaches.

Behavior of Silicon Carbide Materials under Dry to Hydrothermal Conditions.

Silicon carbide materials are excellent candidates for high-performance applications due to their outstanding thermomechanical properties and their strong corrosion resistance. SiC materials can be processed in various forms, from nanomaterials to continuous fibers. Common applications of SiC materials include the aerospace and nuclear fields, where the material is used in severely oxidative environments. Therefore, it is important to understand the kinetics of SiC oxidation and the parameters influencing them. The first part of this review focuses on the oxidation of SiC in dry air according to the Deal and Grove model showing that the oxidation behavior of SiC depends on the temperature and the time of oxidation. The oxidation rate can also be accelerated with the presence of H2O in the system due to its diffusion through the oxide scales. Therefore, wet oxidation is studied in the second part. The third part details the effect of hydrothermal media on the SiC materials that has been explained by different models, namely Yoshimura (1986), Hirayama (1989) and Allongue (1992). The last part of this review focuses on the hydrothermal corrosion of SiC materials from an application point of view and determine whether it is beneficial (manufacturing of materials) or detrimental (use of SiC in latest nuclear reactors).