Metal-ceramic Composites Research Articles

Ударное нагружение слоистых композитов ZrО-=SUB=-2-=/SUB=-/Ti и ZrО-=SUB=-2-=/SUB=-/Al с нежесткими границами раздела

The article presents the results of studies of the impact response of ceramic-metal composites ZrO2/Ti and ZrO2/Al with non-rigid fixing of layers. It is shown that as the energy dissipates from layer to layer, there is an increase in the dispersion of the structure of metal foils and ceramic plates. ZrO2/Ti ceramic-metal composites have higher impact strength, and the impact strength of layered ZrO2/Al composites practically did not differ from the impact strength of monolithic ceramics. It was shown that regardless of the distance between the ceramic plates and the point of impact, their destruction occurred with the transformation of the ZrO2 tetragonal modification into a monoclinic one.

Effect of variation of egg-shell particulate reinforcement on ultrasonic pulse velocity, attenuation, and hardness prediction in ceramic-metal composites

In this study, ceramic-metal composite material reinforced with additive prepared from waste egg-shell was produced. Waste egg-shells were cleaned, dried, ground and then sieved. The effects of egg-shell reinforcement ratio (0%, 1.66%, 3.34%, 5%, and 6.66 % by volume) and sintering temperature (1400?C) applications on Fe-B4C ceramic-metal powders were tested. For this purpose, tests such as ultrasonic test, hardness and density were applied to the composite material, and finally, microstructural analysis was performed on the composites by SEM application. The changes in the crystal structure of the egg-shell after sintering were revealed by diffractograms analysis. It was observed that the hardness, ultrasonic longitudinal and transverse wave velocities also increased with the increase in the reinforcement ratios of the egg-shell. Considering the 6.66% egg-shell addition to the ceramic-metal composite mixture, in the light of the numerical data obtained, 5091 m/s longitudinal wave velocity, 2809 m/s transverse wave velocity, 204.12 Hv hardness value, 0.315 dB per mm longitudinal attenuation and 0.214 dB per mm transverse attenuation values with gave the best physical and mechanical properties. According to the test results obtained, it was determined that it would be appropriate to use the egg-shell in the production of composite materials and to characterize it with the ultrasonic test method.

Experimental analysis of Al composites toughened by aluminium oxide and graphite using stir casting progression

Aluminum-Alloy Reinforced among ceramic particles Composites (AMCs) or Hybrid Metal Composites (HMC) is a class of compact, higher production compositions which are aluminum-centric. Due to their superior physcio-mechanical characteristics when compared to their base Al alloy. Aluminum MMCs are extensively utilized in a mixed range of applications. The present work is aimed to study the mechanical properties of composite Al alloy (A356/LM25) reinforced with micro-sized ceramic particles (Al2O3 and graphite) by means of stir casting process. Different sets of composites with invariable 1% weight fraction of graphite and 1, 3, 5 % weight of ceramic particle size of 100–200 μm (Al2O3) and un-reinforced A356/ LM25 samples are prepared by variable speeds of stirring likely be 200 rpm, 300 rpm and 400 rpm sustaining constant temperature. Tensile strength and hardness tests were performed to study the optimum composition.

Computational and experimental studies of penetration resistance of Ceramic-Metal composites

Study of penetration resistance of combinations of different types of materials has important application in design of body armours, vehicle armours, protection from landmines, etc. We report the development of indigenous Material Point Method (MPM3D) and Smoothed Particle Hydrodynamics (SPH3D) codes along with appropriate material strength and failure models and their validation against published results for different impact velocities. Mie-Gruneisen equation of state, Johnson-Cook strength and Johnson-Cook failure models are used for metals. Johnson-Holmquist model is used for ceramics. Comparison and strengths of these codes are discussed. Simulations are also performed independently for indigenous experiments to study the ballistic limit of three targets, viz. (i) Al-6061 plate (ii) Ceramic plate (iii) Ceramic backed by Al, upon impact by a flat nosed steel-4340 projectile accelerated to desired velocities using an electromagnetic coil gun. The residual velocities for given impact velocities are compared. Simulations carried out using commercial FEM software are also reported. The simulation and experimental results agree very well within 3%. Ballistic limit enhances greatly when ceramic plate is used along with Al plate.

PRODUCTION OF FUNCTIONALLY GRADIENT MATERIALS BASED ON SILICON CARBIDE AND HIGH-ALLOY STEEL USING SPARK PLASMA SINTERING TECHNOLOGY

An important scientific task of practical materials science is the production of metal-ceramic composites in the form of functional gradient materials (FGM) for special-purpose products. In this regard, a study was conducted on the application of spark plasma sintering (IPS) technology for the effective diffusion connection of SiC ceramics and high-alloy steel (grade X18R15) to obtain a combined FGM composite. In a comprehensive experimental study, the dynamics of consolidation and changes in the phase composition of dispersed SiC under conditions of different temperatures and heating rates, pressing pressure, and holding time were studied. As a result, the IPS conditions were optimized for obtaining SiC ceramics of high relative density (82%) and microhardness (500 HV) of stable phase composition. The physicochemical foundations of the formation of a strong compound of a two-component SiC-ceramic and steel system under IPS conditions without additives and using a mixture of additives in the form of a binder, a reaction binder and a damper (Ti–Ag, Ti–TiH2, Ti–Ag–TiH2 and Ti–Ag/Mo additive systems) have been studied. The structure, composition of ceramics and intermediate (binding and damping) layers, as well as the diffusion of elements at the boundary of the formed compounds in FGM composites, were studied using XRF, SEM and EMF methods. It was found that the Ti–Ag/Mo additive in the ratio of 30 wt. % Ti–70 wt. % Ag and a dense layer of Mo (thickness ~ 2 mm), acting as a damper to compensate for the temperature coefficient of linear expansion, ensure the formation of a connected FGM composite of an integral shape. The presented studies have been implemented for the first time, are promising and require further development in order to gain scientific knowledge of the manufacture of composite products for special purposes.

The Schottky barrier and charge transport through the Cu/Al2O3 interface

The charge transport through the interface between metal and semiconductor is important for conductive performance. In this work, we systematically studied the Schottky barrier and charge transport properties of the Cu/Al2O3 interface. Using density functional theory plus the nonequilibrium green function method, a 8.8 eV bandgap of Al2O3 is obtained and the Schottky barrier is calculated for the oxygen and aluminium terminated interfaces. The charge transport properties are found to depend sensitively on the combination of the interfaces. The Schottky barrier and charge transport properties found in the Cu/Al2O3 interface can guide its applications in the field of integrated circuits and metal-ceramic composites.

Molecular Dynamics Study of Interdiffusion for Cubic and Hexagonal SiC/Al Interfaces

The mechanical properties of the SiC/Al interface are crucial in estimating the overall strength of this ceramic-metal composite. The present work investigates the interdiffusion at the SiC/Al interface using molecular dynamics simulations. One cubic and one hexagonal SiC with a higher probability of orientations in contact with Al are examined as two samples of metal-matrix nanocomposites with whisker and particulate reinforcements. These reinforcements with the Si- and C-terminated surfaces of the SiC/Al interfaces are also studied. The average main and cross-interdiffusion coefficients are evaluated using a single diffusion couple for each system. The effect of temperature and annealing time are analysed on the self- and interdiffusion coefficients. It is found that the diffusion of Al in SiC is similar in cubic and hexagonal SiC and as expected, the interdiffusion coefficient increases as the temperature and annealing time increase. The model after diffusion can be used to evaluate the overall mechanical properties of the interface region in future studies.

Вплив забрудненості порошку на поріг протікання металокерамічних композитів, що отримуються на основі полідисперсних порошкових сумішей

A theoretical method of finding by simulation computer modeling the percolation limit of composites of powder origin, which are obtained on the basis of polydisperse powder mixtures of the conductive and insulating phase, is proposed. At the same time, the degradation of the conductivity of conductor particles skeleton due to oxidation or other contamination of the surface of the particles is taken into account. To study the flow threshold of materials obtained on the basis of polydisperse powder mixtures, the use of regular packings of particles, which are considered in the classic problems of perco¬lation theory, for example, square or hexagonal packing, is not acceptable even in the first approximation. Because in such packages all particles are the same, or the ratio of particle sizes is fixed. At the same time, as is known from the practice of obtaining metal-ceramic composites, the size distribution of conductor and insulator particles is one of the determining factors. Therefore, a generator of random filling of a polydisperse mixture of round particles into a rectangular hopper was developed using the Fortran programing language. The influence of the particle size ratio of the conductive and insulating phases and the relative contamination of the conductor particles on the percolation limit in the composite was studied. It is shown that in the case when the size of the conductor particles decreases in relation to the size of the insulator particles, the value of the percolation limit decreases, that is, conductivity can be achieved even with asmall content of the conductive phase. In this way, the conductivity of the metal-ceramic composite can be controlled without changing the concentration of the conductive phase, but only by varying the size of the metal and ceramic particles. But as the simulation results showed, this method of controlling the conductivity is very sensitive to the oxidation of the metal powder. Even a relative oxidation of the powder surface of 0,1 doubles the concentration of the metal phase required for percolation. Keywords:bidisperse packaging, percolation limit, ballistic filling, metal-ceramic composites, oxidized metal powders.

Improved Thermal and Mechanical Properties of [Ca24Al28O64]4+(4e−) Electride Ceramic by Adding Mo Metal

The low‐work function material [Ca24Al28O64]4+(4e−)—named as C12A7:e‐ or electride—is a promising candidate to replace established materials such as BaO–W or LaB6 electron emitters because of its good reported electron emission in plasma environments and decent chemical inertness. However, it has poor thermal conductivity and low mechanical behavior. Therefore, cracks due to thermal shock occur in applications under thermal load, when used as a thermionic emitter. The addition of a metal with high thermal conductivity to create a ceramic–metal composite (CerMet) is evident. Molybdenum has a very high thermal conductivity and a coefficient of thermal expansion comparable to C12A7:e‐. This allows the crack‐free sintering of a composite ceramic made of C12A7:e‐ and Mo with improved thermal and mechanical properties as well as still low work function of the C12A7:e‐. Herein, the C12A7:e‐/Mo CerMets are characterized in terms of their thermal conductivity, thermal expansion coefficient (CTE), hardness, toughness K1C, and strength as a function of Mo content. The CerMets have been tested in a plasma‐based cathode with disk‐shaped emitters for electron emission characteristics. An optimal range of the Mo content for the stability of the plasma discharge and the required discharge potential has been evaluated.

Visible Light-Induced Oxidative Degradation of Chloramphenicol by Iron-Containing Ceramic-Metal Composites

Visible Light-Induced Oxidative Degradation of Chloramphenicol by Iron-Containing Ceramic-Metal Composites

Critical Assessment of Two-Dimensional Methods for the Microstructural Characterization of Cemented Carbides

Cemented carbides, or hard metals, are ceramic–metal composites usually consisting of tungsten carbide particles bound by a cobalt-based alloy. They are the backbone materials for the tooling industry, as a direct consequence of the outstanding range of property combinations, depending on their effective microstructural assemblage, i.e., the physical dimensions and relative content of their constitutive phases. Hence, reliable microstructural characterization becomes key for hard metal grade selection and quality control. This work aimed to assess the practical two-dimensional characterization methods for the most important one- and two-phase properties of cemented carbides, i.e., the carbide grain size, phase fraction, carbide contiguity, and binder mean free path. Three different methods—point, line, and area analysis—were implemented to characterize four microstructurally distinct grades. The images were acquired by optical and scanning electron microscopy, with the latter through both secondary and backscattered electrons. Results were critically discussed by comparing the obtained values of properties and the different characterization methodology. Inspection technique combinations were finally ranked based on accuracy, accessibility, and operability considerations. The line method was used to analyze all the properties, the area method, for the one-phase properties, and the point method, for only the phase fraction. It was found that the combination of optical microscopy and the line analysis method was suitable for a direct inspection and rapid estimation for carbides above fine grain size. The most precise results were achieved using line analysis of the images obtained by the backscattered electrons of the scanning electron microscope.

PREPARATION OF A METAL-CERAMIC COMPOSITE BASED ON ALUMINUM OXIDE BY INTERNAL OXIDATION

The possibilities of obtaining metal-ceramic materials of the composition Al2O3–Al by liquid-phase oxidation of aluminum by purging the melt with oxygen are considered. The manufacturability of this process makes it possible to avoid the use of powder materials, which leads to a large variability in the formation of the phase components of the materials obtained and a reduction in the cost of their production in comparison with powder metallurgy methods. It is established that by regulating the oxidation process by changing the speed and supply of the gas mixture, it is possible to obtain metal-ceramic composites with different geometric configurations of the ceramic phase and its quantity. An algorithm is proposed for calculating the kinetics of aluminum oxidation during the production of the ceramic phase of a metal-ceramic composite, taking into account the peculiarities of the thermophysical process.

Physicochemical and Mechanical Studies of Al2O3–Cu Metal-Ceramic Composites Obtained by Spark Plasma Sintering

Physicochemical and Mechanical Studies of Al2O3–Cu Metal-Ceramic Composites Obtained by Spark Plasma Sintering

Advanced ceramics and coatings for erosion‐related applications in mineral and oil and gas production: A technical review

AbstractThe applications of advanced ceramics, composites and coatings in mineral, mining, fuel production, and processing are reviewed. The materials include oxide and non‐oxide ceramics (specifically SiC‐based), ceramic–ceramic, and ceramic–metal composites, coatings on metallic components where functional application properties can be achieved. Some principles of materials selection, specifically for erosion wear and corrosion applications, and manufacturing are considered. The examples of the successful development and processing of ceramics, coatings, and composites with manageable structures and phase compositions, in the erosion‐related applications, particularly conducted by the author, are discussed and reviewed. Specifically, industrially employed types of ceramics and processing routes were focused on the considered applications. Particular demands for advanced materials with high reliability and complex shapes or for protective coatings on complex shape steel components and long tubing with inner surface protection require novel and optimized processing. The factors affecting erosion and erosion–corrosion resistance and the paths for the erosion resistance enhancement of ceramic and coating materials are considered. Ceramic components design, technology, and installation features are reviewed.

Residual elastic strain evolution due to thermal cycling of a ceramic-metal composite (WC-Cu) via high energy X-ray diffraction and analytical modeling

Residual stress, when superimposed with in-service loading, can significantly reduce the lifetime and performance of a component. Ceramic-metal composites are susceptible to residual stresses due to the thermal expansion mismatch of the ceramic and metallic phases. The WC-Cu composite explored in the present study provides a promising combination of thermal conductivity and strength properties, while exhibiting counterintuitive improvements in strength and ductility after thermal cycling. This work quantifies the evolution of the residual elastic strains as a result of processing and cyclic thermal loading in a co-continuous WC-Cu composite through experimental high energy X-ray diffraction and kinetics-based modeling. Both analyses indicate that processing-induced residual tensile stress in the copper phase is relieved upon subsequent thermal cycling, with kinetics modeling revealing the cyclic-dependent nature of the active power-law creep mechanisms. The results indicate that, through stress relaxation, this material system maintains structural stability during thermal cycling. The illustrated kinetics of relaxation can inform general material processors and designers of ceramic-metal composites to minimize detrimental residual stress and improve performance of these material systems.

Dynamic strength, reinforcing mechanism and damage of ceramic metal composites

• We fully study the shock responses of ceramic metal composites via NEMD . • The interaction of shock-wave with the interface affects dislocation strengthening. • An abnormal softening effect is captured under shock loading . • The interface possesses negative effect on damage for composites. Shock tolerance is desirable for ceramic particles-reinforced metal matrix composites in many applications, where the dislocation dynamics evolution under the extreme load is the key but still elusive. Herein, we have investigated the dislocation motion and interaction under shock loading of SiC/Al nanocomposites using molecular dynamics simulations. We have demonstrated that the plastic deformation occurs at an impact velocity (0.5 km/s) lower than the Hugoniot elastic limit of aluminum due to the reflected shear wave effect. The Al/SiC interfaces act as a dislocation emitter to control dislocation multiplication density and slip direction, opening a new pathway to achieve ultrahigh-strength via shock loading. When the impact velocity (1.0 or 1.5 km/s) exceeds the Hugoniot elastic limit, the effect of nanoparticles on dislocation structure has changed from multiplying to retarding dislocations. The spall strength of composites improves due to dislocations pile-up at interface. Instead, the damage in the matrix is exacerbated, owing to the enhanced residual peak stress and interface reflection waves. In addition, the effect of abnormal shock softening determined by atomic velocity is revealed, which could be suppressed by increasing impact energy dissipation. Meanwhile, dynamic compressive strength depends on pressure and dislocation structures evolution. Our atomistic insights might be helpful in designing advanced shock-tolerant materials.

Microstructure and mechanical properties of TiC/multi-principal-component alloy composites with biomimetic micro-laminated structure

Natural biology has inspired the design and development of new synthetic metal-ceramic composites, which have excellent mechanical properties and wear resistance. In the present study, biomimetic micro-laminated structure TiC–CoCrCuFeNi composites with good interfacial binding were prepared. The mechanical properties, i.e., compressive strength and ductility, wear resistance were analyzed. A good combination of strength and ductility was achieved (1270 MPa, 7.1%), which was arisen from the Improvement of work hardening effect and deformation compatibility. The compressive strength is inversely proportional to the engineering strain. The excellent wear resistance of the composites is due to the internal residual compressive stress and the lubrication of the oxide film. The wear mechanism is microcrack, and the lowest specific wear rate is only 1.36 × 10−14 m3/N*m.

Properties of Al2O3/Ti/Ni Composite Obtained by Slip Casting with Different Metal Phase Content.

This work analyzed ceramic-metal composites from the Al2O3/Ti/Ni system produced by the slip casting method. As starting powders, nanometric Al2O3, Ni and Ti of submicron size were used. Three series of composites were obtained and tested with the same solid phase content (50% vol.) and different metallic phase content: 5, 10 and 15% vol. The influence of the metallic phase content on the basic properties of the proposed composites was examined by determining the phase composition of the produced samples using the XRD method, rheological measurements, and microstructural analysis (SEM/EDS). Additionally, before the sintering process, the slip stability was analyzed. A study of the fractography of samples after the sintering process was also carried out. It was shown that the appropriate manufacturing process allowed to obtain NiTi intermetallic phases in the structure of composites.

Toughness mechanism and plastic insensitivity of submicron second phase Ta in a novel Ta–Hf6Ta2O17 composite ceramic

The introduction of metal-second phase can improve the fracture toughness of metal-ceramic composite (MCC) material, but usually degrades the strength and hardness. The pace of exploring the process and materials to both improve the toughness and hardness has never stopped. In this study, a novel Ta–Hf6Ta2O17 composite ceramic is successfully prepared by spark plasma sintering. The effects of Ta content on microstructure and mechanical properties of the as-sintered ceramic are investigated. The fracture toughness of Ta–Hf6Ta2O17 composite ceramic first increases and then decreased slightly with the increase in Ta content, reaching the maximum value of 4.21 ± 0.09 MPa m1/2 at 20 vol% Ta. The improvement of the fracture toughness does not affect the hardness, whose value is stable between 16.74 GPa and 18.43 GPa. Based on the results of Selsing’s model, Raman spectra and TEM, it is confirmed that the toughness mechanism of Ta–Hf6Ta2O17 composite ceramics originates from good inherent interface strength and crack deflection caused by the second phase. The maintenance of hardness comes from the plastic insensitivity of submicron Ta caused by the interfacial tensile stress, which provides a potential mechanism for the design of metal-ceramic composite with excellent strength and toughness.

Novel processing route for design and manufacturing of metal toughened nanoceramics: Al–Al2O3 nanocermets

Monolithic alumina is a highly brittle ceramic with a very low fracture toughness, making it an unreliable material for mechanical and structural applications. Ceramic-metal composites (cermets) are the subject of intensive interest to obtain materials which can address the intrinsic brittleness of ceramics without compromising their high strength and light weight. In the present investigation, aluminium-alumina (Al–Al 2 O 3 ) nanocermets were developed. The nanocermets possessed the toughness of Al phase and the strength of reinforced nano Al 2 O 3 particles. The nanocermets green bodies were prepared such that upon sintering each adjacent Al 2 O 3 grain was conformally coated with a continuous Al film. Mechanical milling via a combination of cryo-milling and ball-milling was used to prepare Al–Al 2 O 3 nano-powder mixture. Spark plasma sintering was used to consolidate the green nanocermets. Results show that specimens prepared from 35 h milled powders exhibited superior mechanical properties as compared to other nanocermets, with an improvement in microhardness, elastic modulus, compressive strength, and flexural strength by 88%, 78%, 69% and 40% with respect to sintered pure Al. The indentation toughness of 35 h milled nanocermet showed an increment of 12.5% with respect to sintered pure Al 2 O 3 . Characterization techniques such as XRD, SEM, HR-TEM, X-ray tomography were employed to investigate the phase evolution and structural morphology, while FEM simulations were performed for understanding the crack propagation mechanisms in nanocermets. Figure Description: A novel processing route devised from the combination of cryo-milling and ball-milling of elemental Al and Al 2 O 3 powders, followed by spark plasma sintering (SPS) for the development of toughened and strengthened Al–Al 2 O 3 nanocermets (metal-ceramic nano-systems). An attempt has been made to utilize the favourable physical and mechanical attributes of ductile metal phase and brittle ceramic phase to fabricate nanocermets with enhanced mechanical properties. These nanocermets will find use in structural applications requiring components with high strength to weight ratio, such as automotive parts, ballistic armours and jet propulsion systems. • Al 0.2 -(Al 2 O 3 ) 0.8 nanocermets possessing the toughness from ductile Al and strength from brittle Al 2 O 3 are developed. • A combination of cryo-milling and ball-milling is used for the preparation of nanosized Al-Al 2 O 3 powder mixtures. • An optimized cryo-milling of 10 h transforms micron-sized Al particles into nanometric thin sheets. • Enhanced wettability of Al and Al 2 O 3 at the grain boundary interface is achieved for metal-ceramic nano-systems. • Toughening of brittle Al 2 O 3 by metallic Al phase transforms the inter-granular fracture into trans-granular mode.