Mechanical Properties Of Ceramic Composites Research Articles

Effect of sintering additives on the properties of alumina toughened zirconia (ATZ)

The effect of small amounts of copper oxide, manganese oxide, and stainless steel as sintering additives on the sintering behavior and mechanical properties of Alumina Toughened Zirconia (ATZ, 3Y-TZP with 20 wt% Al2O3) ceramic composites were evaluated and contrasted with that of undoped ATZ by using microwave sintering (MW) method. Green bodies were sintered at 1250°C, 1350°C, and 1500°C using a holding time of 5 min., with a heating rate of 30°C /min. In general, all ATZ samples exhibited a similar trend, as the results showed that the relative density and mechanical properties increased with increasing sintering temperature regardless of the addition of dopants. It was found that the addition of 0.2 wt% CuO, 0.5 wt% MnO2, and 0.2 wt% SS were beneficial in enhancing the densification and improving the mechanical properties of ATZ without inducing grain coarsening. The ATZ composite samples' relative density, tetragonal phase stability, microstructural evolution, Vickers hardness, and fracture toughness were revealed. The addition of 0.2 wt% CuO was the most beneficial in improving the properties of ATZ at a low sintering temperature of 1250°C since the sample obtained the highest relative density of 97%, Vickers hardness of 13.2GPa and fracture toughness of 6.5 MPa m1/2. In contrast, the undoped ATZ required a high sintering temperature to achieve comparable results to the doped samples. The ANOVA analysis revealed that the CuO-doped ATZ sample exhibited the highest significance and was the most suitable in improving both hardness (H) and fracture toughness (KIc) across all temperature conditions. This study also proved that the microwave sintering technique promotes the densification and mechanical properties of ceramic composites compared to the conventional sintering technique.Graphical abstract

Computational modeling and mechanical properties of 3Y-TZP ceramic composites reinforced by mullite whiskers with different diameters

An accurate characterization of microstructure is essential to realize the performance prediction and design optimization of the ceramic matrix composites (CMCs). In this work, according to the feature of in-situ growth of mullite whiskers in 3 mol% Y2O3 stabilized tetragonal ZrO2 (3Y-TZP) ceramics, 2 vol% whiskers of different diameters formed in the 3Y-TZP ceramics were numerically reconstructed based on Monte Carlo method to explore the mechanical properties of the ceramic composites. The results show that the nanoindentation model of whisker reinforced 3Y-TZP ceramics can effectively predict the hardness of the composite ceramics according to load-depth curves. The stress transfer mechanism between the ceramic matrix and the whiskers can also be found. It is found that the hardness of the composite ceramics decreases gradually with the increase of the whisker diameters. According to three-point bending model, the obtained bending strength and fracture toughness of the composite ceramics increase first and then decrease with increasing whisker diameter. When the diameter of mullite whiskers is 0.12 μm, the bending strength of the composite ceramics reaches the maximum of 826 ± 25 MPa and the fracture toughness reaches the maximum of 10.5 ± 0.2 MPa•m1/2. The toughening mechanism of whisker reinforced 3Y-TZP ceramics was also demonstrated. This work provides a numerical method for the selection and optimization of parameters of reinforcement phase in preparation of 3Y-TZP ceramic composites.

Modeling of the Influence of Graphene Agglomeration on the Mechanical Properties of Ceramic Composites with Graphene

Modeling of the Influence of Graphene Agglomeration on the Mechanical Properties of Ceramic Composites with Graphene

Nano/microstructures and mechanical properties of Al2O3-WC-TiC ceramic composites incorporating graphene with different sizes

Graphene additives with different sizes were employed to strengthen and toughen Al2O3-WC-TiC ceramic composites. The effect of graphene sizes on interfacial characteristics, microstructures and mechanical properties was investigated. The results indicated that the interfacial chemistry reaction products and sizes of the products were subject to graphene sizes. With the increase of graphene thickness, the interfacial reaction products between graphene and Al2O3 changed from Al4O4C to Al4C3 and the sizes of products were increased. Based on first-principles calculation results, it has been found that Al4O4C and Al4C3 interfacial phases contributed to the formation of the strong-weak staggered interfaces in ceramic composites. Graphene with low thickness and large lateral size was more beneficial to improve mechanical properties of ceramic composites. Especially, the flexural strength and fracture toughness of the composite incorporating single layer graphene were increased by 67.59% and 54.10%, respectively, compared to the composite without graphene. The strong-weak staggered interfaces induced by graphene were responsible for the improved flexural strength and fracture toughness.

Mechanical properties of ceramic composites based on ZrO2 co-stabilized by Y2O3–CeO2 reinforced with Al2O3 platelets for dental implants

ObjectivesThe objective of this work was the development and characterization of a ceramic composite based on (Ce,Y)-TZP/Al2O3 aiming an application on dental implants, comparing it with conventional monolithic 3Y-TZP ceramics, currently used for the same type of application. MethodsCeramic samples, 3Y-TZP (n = 40) and (Ce,Y)-TZP/Al2O3 (n = 40), were sintered at 1500 °C - 2h and characterized by relative density, X-Ray diffraction (XRD) and microstructure. Then, the samples of both materials were divided into two groups: 1) samples with original (as sintered) surfaces; 2) samples with conditioned, polished, surfaces. All samples were submitted to hydrothermal degradation tests, on an autoclave (134 °C - 2 bar), for 10 h in artificial saliva. The degraded samples were characterized by XRD and the polished group were also characterized by their elastic moduli, Vickers hardness and fracture toughness (Vickers indentation method). Both groups were also submitted to a flexural strength test, 3B–P testing, for which the data were interpreted using Weibull statistics. ResultsAll sintered specimens presented nearly full densification. After the hydrothermal degradation tests, 3Y-TZP samples presented 16.4% of monoclinic (m)-ZrO2 phase while the composite samples withheld 100% of tetragonal (t)-ZrO2 phase. Both materials presented equiaxial ZrO2 grains with an average size of 0.48 ± 0.17 μm and 0.75 ± 0.22 μm, respectively, for the monolithic and composite ceramics. In the composites, is observed the presence of well distributed Al2O3 grains on the ZrO2 matrix, in two distinct morphologies: equiaxial grains and platelets. The composites (Ce,Y)-TZP/Al2O3 presented average values of elastic moduli, Vickers hardness and fracture toughness of 228.3 ± 6.5 GPa, 1427 ± 46 HV e 11.3 ± 0.4 MPa m1/2, respectively. An inversely proportional relationship is observed between the roughness and the bending strength, since the 3Y-TZP samples presented a average strength of 860.7 ± 81 MPa (as-sintered) and 965.4 ± 93 MPa (polished) while the (Ce,Y)-TZP/Al2O3 composites presented average strength of 810.6 ± 147 MPa (as-sintered) and 952.6 ± 88 MPa (polished). ConclusionsThe composites (Ce,Y)-TZP/Al2O3 showed high resistance to degradation in saliva and adequate properties for use as dental implants. Values of flexural strength (>950 MPa) and Weibull modulus (m > 10) were similar to the conventional 3Y-TZP ceramics. Moreover, its hardness, elastic modulus and fracture toughness were higher than those obtained for 3Y-TZP. The expressive values of KIC obtained for (Ce,Y)-TZP/Al2O3 composites are results of association of different toughening mechanisms acting simultaneously in the material.

Влияние углеродных нанотрубок на микроструктуру и трещиностойкость наноструктурной оксидной керамики

The structure and properties of ceramics based on zirconium dioxide stabilized yttrium oxide with the addition of high-modulus inclusions of carbon nanotubes were investigated. The composite materials were obtained by spark plasma sintering. The introduction of carbon nanotubes provides a slight decrease in the density and grain size of ceramics. Growth of volume fraction of carbon nanotubes leads to increase of mechanical properties of ceramic composites. The highest values of mechanical properties were obtained by the introduction of 5 vol.% of carbon nanotubes and were E = (246±8) GPa, H = (12.7±0.21) GPa, K 1 CI = (12.1±0.35) MPa∙m1/2, K 1 CN = (7.8±0.29) MPa∙m1/2. The increase of fracture toughness when carbon nanotubes are introduced into the ceramic matrix is caused by two dissipative mechanisms - phase transformation from tetragonal to monoclinic modification of ZrO2 and crack bridging. As the amount of introduced additive increases, the contribution of martensitic transformation in fracture resistance decreases, which is associated with a decrease in the grain size of the tetragonal zirconium dioxide phase and, accordingly, its transition to a stable state.

Microstructure and mechanical properties of SPS sintered Al2O3–ZrO2 (3Y)–SiC ceramic composites

Al2O3–ZrO2 (3Y)–SiC ceramic composites were prepared by spark plasma sintering in vacuum under 40 MPa of uniaxial compression between 1300 °C and 1400 °C. The effect of nano-size SiC and sintering temperature on the microstructure and mechanical properties of ceramic composites were investigated. The results showed that SiC particles was uniformly distributed in the composite, mainly within the matrix grains. Sintering temperature and SiC particles caused the shape of alumina grains to be columnar. The flexural strength of 22.3 vol% Al2O3-57.7 vol% ZrO2-20 vol% SiC sintered at 1350 °C composites was 1081 MPa, fracture toughness was 15.18 MPa m1/2 and hardness was 16.42 GPa. The addition of SiC particles leads to grain boundary strengthening, and the change of fracture mode and cracks deflection and bridging are considered to be the main reasons for the increase in material fracture toughness.

Microstructure and Properties of Boron-Carbide Composites Reinforced by Graphene

The influence of graphene oxide on the microstructure and mechanical properties of ceramic composites that are based on boron carbide and produced by spark plasma sintering is considered. For composites produced with the optimal addition of graphene oxide (0.5 vol %), in the given sintering conditions (Tsi = 1950°C, Pmax = 80 MPa, and tres = 10 min), the density and mechanical properties are very good.

Modelling the effect of temperature on the physical and mechanical properties of ceramic composites filled with foundry sand waste

The aim of this research is to describe the temperature effect on the water absorption, linear shrinkage, density and compressive strength of ceramic composites produced by mixing clay with additions of foundry sand waste from 20% to 40% wt. Previous studies have shown that foundry sands can be recycled due to the high content of SiO2 on its chemical composition, therefore, in this research is proposed as an alternative raw material in ceramic bodies. Prototypes were shaped by uniaxial pressing method and fired at three different temperatures (850°C, 950°C and 1,050°C) in order to promote the formation of the ceramic phases. Physical and mechanical properties were measured based on the procedures specified by standard ASTM C373 and ASTM C773-88. It was found that at 1,050°C properties such as mechanical strength and density reach its maximum values, effect that might be associated to the reduction in pore size inside the microstructure during calcination. The main merit of the models obtained is offer a valuable tool to set up a proper thermal process in order to obtain eco-friendly ceramic samples with physical and mechanical properties at its optimum values, reducing environmental problems related to landfill disposal and minimizing costs of manufacturing.

Study of the microstructure and mechanical properties of halloysite–kaolinite/BaCO3ceramic composites

ABSTRACTThe present study examined the microstructure and mechanical properties of ceramic composites based on a kaolin from Djebel Debbagh, northeast Algeria, composed mainly of kaolinite and halloysite with the addition of various amounts of BaCO3. The composites were prepared by high-energy ball milling and sintered at 1100°C and 1200°C for 3 h. The samples sintered at 1200°C without BaCO3were composed mainly of mullite, which disappeared with increasing BaCO3content. X-ray diffraction investigation showed the presence of hexacelsian (BaAl2SiO6and BaAl2Si2O8), which disappeared at BaCO3contents >50 wt.% in favour of barium aluminium and barium silicate phases. At 40 wt.% BaCO3content, the porosity of the composites decreased from 0.7% to 0.1% and the microhardness increased from 7 to 8 GPa, respectively, at 1100°C and 1200°C due to the amorphous phase.

Improvement of White Duekhla Clay properties by using Low-Density Polyethylene Fillers to use it in ceramic industries

The research was summarized in preparation and make samples of the ceramic body that are filled with Low-Density Polyethylene particles.The composite materials were manufactured by using ( Duekhla White Caly with Polymer particles) for purposes of improving the properties of clay for ceramic uses. The samples were prepared from The white Duekhla clay with fixed particle size (150µm) as a matrix and adding polymer powder particles (50µm) as fillers by different ratios in the range (2, 4, 6, 8, 10) %. Some essential materials such as feldspar and the fluvial sand. The results that were obtained from tests showed that higher contents of low-density polyethylene(LDPE) and that were added to the ceramic mixture gave good results and significant improvements for water absorbance resistance and less thermal conductivity. The mechanical properties of ceramic composites were improved by a higher ratio when adding (10%) of LDPE to ceramic composites. For example, the tensile strength was increased by an amount (175.5MPa) for the addition ratio (10%), compared with the pure sample (133MPa). The results of water absorbance and thermal conductivity decreased with increasing of the addition ratio for LDPE fillers. All obtained results indicated to the possibilities of improving the quality of the used clay in the ceramic industry for increasing the plasticity and disappear some disadvantages that were observed during the tests that were obtained on them

Improving Mechanical Properties of Ceramic Composites by Harmonic Microstructure Control

In this research, several ceramic composites such as SiC-ZrO2, Al2O3-ZrO2, and Si3N4-ZrO2 containing nominally equal ratio 1:1 were prepared through high energy mechanical milling and spark plasma sintering. The relationship of microstructure and mechanical properties were investigated. Harmonic microstructures consisting of fine and ultra-fine grains forming a network were obtained by the optimum milling time for 144ks with high mechanical properties. The non-milled powder mixtures and too long milling time powder mixtures have low mechanical properties sintered by spark plasma. The crack propagates through ultra-fine grains and deflected by larger fine grains were obtained on the harmonic microstructure sample resulting in high toughness. Thus, the harmonic microstructure can be considered a remarkable design tool for improving the mechanical properties of SiC-ZrO2, Al2O3-ZrO2, and Si3N4-ZrO2 as well as other ceramic composites.

Изучение механических свойств керамических композитов с разным объемом пластичного наполнителя

Изучение механических свойств керамических композитов с разным объемом пластичного наполнителя

Study of the Mechanical Properties of Ceramic Composites with Different Volume of Plastic Filler

Studying of mechanical properties of brittle heterogeneous materials with different structural parameters, in particular value of porosity and volume of inclusions is very important for both fundamental science and practical applications. Therefore, in this paper a multiscale computer model of mechanical behaviour of ceramic composites with different porosity and filler-containing pore fraction under shear loading was proposed. The model was developed in the framework of movable cellular automaton method. On the basis of numerical calculations an analytical evaluation for the dependence of shear strength and elastic modulus of the material on its total porosity and fraction of pores containing filler was proposed.

Determination of interfacial mechanical properties of ceramic composites by the compression of micro-pillar test specimens

A novel method to determine the fiber-matrix interfacial properties of ceramic matrix composites is proposed and evaluated; where micro-pillar samples containing inclined fiber/matrix interfaces were prepared from a SiC fiber-reinforced SiC matrix composites and then compression-tested using the nano-indentation technique. This new test method employs a simple geometry and mitigates the uncertainties associated with complex stress state in the conventional single-filament push-out method or tensile unloading–reloading hysteresis loop analysis method for the determination of interfacial properties. Based on the test results using samples with different interface orientations, the interfacial debond shear strength and the internal friction coefficient are explicitly determined and compared with values obtained by other test methods. SEM observation showed that micro compression caused an adhesive type of debonding between the fiber and the pyrolytic carbon interface. The results suggest that the debonding/failure behavior of the micro-pillars followed the Coulomb fracture criterion. The determined interfacial debond shear strength is ~100 MPa, which appears to be smaller than that determined from fiber push-out test for similar composite systems. The difference can be explained by the effect of normal stress (clamping stress) on the apparent interfacial debond shear strength.

Microstructure and Mechanical Properties of Ceramic Composites

Ceramic matrix composites reinforced with metals have been developed to overcome the intensive brittleness and lack of reliability of monolithic ceramics, with a view to introduce ceramics in structural parts used in severe environments such as rocket and jet engines, gas turbines for power plants, heat shields for space vehicles, fusion reactor first wall, aircraft brakes, heat treatment furnaces. In view of these the effects of Al-6%Si alloy particles on the ascast microstructure and properties of Tin Tailings ceramics matrix composites produced by powder metallurgy method have been studied. 5-30 weight percent Al-6%Si alloy particles were added. The results revealed that, addition of Al-6%Si alloy reinforcement increased the linear shrinkage, strength and impact energy with a decreased in density, porosity and hardness value. These increases in strength and impact energy are attributed to the uniform distribution and strong bonding of the soft metal phase in the hard ceramic matrix. These results show that better properties are achievable by addition of Al-6%Si alloy to Tin Tailings.

ANALYSES OF INFLUENCE FACTORS ON MECHANICAL PROPERTIES OF CERAMIC COMPOSITES REINFORCED BY NANO-MICRO PARTICLES

The main influence factors on mechanical properties of ceramic composites reinforced by spherical nano-micro particles are investigated in this study. The sizes of the particles vary from micro (0.5 µm) to nano-scale (40 nm). Two kinds of representative volume elements (RVE) are applied to describe different arrays of nano-micro particles. One is the nesting array in which a nano-particle is nested within the microscopic particles, and the other is the enwrapping array in which a micro-particle is enwrapped by some nano-particles. The finite element (FE) analysis is conducted by the global-local homogenization method with precise period boundary conditions. The numerical simulation is performed with the changes of radius ratios of nano-micro particles, volume fractions and the interfacial properties. The results show that the effective Young's modulus of the composites with the enwrapping array has an obvious increase as compared to those with the nesting array for high volume fraction of micro-particles, and it is dependent on the radius ratios of nano-micro particles within certain volume fractions. The interfacial damage between nano-micro particles and their matrix decreases significantly the effective Young's modulus. It is significant to improve the mechanical properties of ceramic materials by mixing some nano- and micro-particles into the matrix with mature interface properties.

Effects of carbon on the microstructure and fracture toughness of composite ceramic materials

In brittle composites, spontaneous microcracking might occur due to the presence of residual stresses. As microcracking has a significant influence on the properties of composite ceramic materials, it is important to understand the mechanism of microcrack formation in order to introduce a controlled amount of microcracking. However, there are fairly few materials where toughening by microcracking has been rigorously verified. Fully validated examples of microcracking toughening are restricted to the composite materials such as zirconia toughened alumina (ZTA) [1], SiC/TiB2 [2] and some of the liquid-phase sintered SiC ceramics [3]. The appropriate addition of additives plays an important role in improving physical and mechanical properties of ceramic composites [4, 5]. Various additives such as the rare earth, the oxide of alkaline metals, metallic elements and carbon, and so on, have got wide applications in both structural and functional ceramics. Specifically, the addition of carbon is beneficial for sintering and improvement of the properties of SiC/TiB2/TiC ceramic composite [6]. Moreover, it was reported by Sigl et al. [7] that the fracture toughness of B4C/TiB2 ceramic was notably increased because of the addition of a certain amount of free carbon. On the other hand, Al2O3/TiC composite is one of the popularly used structural ceramic materials. Since the 1970s, a great deal of research work has been done focusing on the microstructure, mechanical property and engineering performance of Al2O3/TiC composite [5, 8–10]. Sintering aids like MgO, TiO2, Y2O3, TiH2, Ni and Mo, etc. has been adopted in the fabrication of Al2O3/TiC composite for high density and properties [10–14]. In the present study, a certain amount of free carbon is purposely incorporated into Al2O3/TiC ceramic composite. Attempts have been made to investigate its influence on the microstructure and fracture toughness of the material. High purity Al2O3 and TiC powders were used as the starting materials with average sizes of 0.5 and 0.8 μm, respectively. Al2O3 was blended with TiC (30 vol.%) and doped with different amounts of phenolic resins to yield samples with varying amounts of free carbon additives in the as-sintered bodies. The mixtures were subsequently homogenized with alcohol media in a ball

Mechanical properties of ceramic composites

Silicon-nitride-based ceramic materials are strong candidates for structural applications, such as cutting tools, considering their high thermal and mechanical properties. However, such materials can suffer catastrophic failures, because they are very sensitive to flaws. In this work, silicon-nitride-based matrix was reinforced with silicon carbide whiskers, aiming to increase fracture toughness. Monolithic silicon nitride samples were also produced. All compositions were pressureless and hot uniaxial pressed, followed by physical and mechanical properties determination. Fracture toughness of composites showed higher fracture toughness values than those from monolithic materials, probably by the activation of crack and crack-bridging mechanisms.

Fabrication and Properties of Tape‐Cast Laminated and Functionally Gradient Alumina–Titanium Carbide Materials

A tape‐casting process was used to prepare various Al2O3–TiC green tapes, from which laminated and functionally gradient Al2O3–TiC materials (FGM Al2O3–TiC) were produced by cutting, stacking, and laminating the material, removing the binder, and hot‐pressing the green bodies. The bending strength of the FGM Al2O3–TiC composites was not much less than that of the laminated Al2O3–TiC composites. However, the fracture toughness was >50% higher; the fracture toughness of the FGM composite sintered at 1700°C was 9.43 MPa·m1/2. This increased toughness was attributed to the stress distribution that was caused by variations in the composition of the FGM composite layers. The present results demonstrate that the FGM design is a useful method for modifying the mechanical properties of ceramic composites.