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1.
《Journal of the European Ceramic Society》2017,37(12):3721-3729
The thermal conductivity (κ) of AlN (2.9 wt.% of Y2O3) is studied as a function of the addition of multilayer graphene (from 0 to 10 vol.%). The κ values of these composites, fabricated by spark plasma sintering (SPS), are independently analyzed for the two characteristic directions defined by the GNPs orientation within the ceramic matrix; that is to say, perpendicular and parallel to the SPS pressing axis. Conversely to other ceramic/graphene systems, AlN composites experience a reduction of κ with the graphene addition for both orientations; actually the decrease of κ for the in-plane graphene orientation results rather unusual. This behavior is conveniently reproduced when an interface thermal resistance is introduced in effective media thermal conductivity models. Also remarkable is the change in the electrical properties of AlN becoming an electrical conductor (200 S m−1) for graphene contents above 5 vol.%. 相似文献
2.
《应用陶瓷进展》2013,112(3):99-102
AbstractThe applicability of electrophoretic deposition (EPD) for the fabrication of single layer and multilayer ceramic coatings on dense ceramic composite materials has been examined. Al2O3/Y-tetragonal zirconia polycrystal (TZP) functionally graded composites of tubular shape were successfully coated with a two layer coating comprising porous alumina and dense reaction bonded mullite layers. The dual layer coating structure was designed to eliminate the numerous cracks caused by volume shrinkage during sintering of the individual EPD formed layers. In another example, mullite fibre reinforced mullite matrix composites were coated with a thin layer of nanosized silica particles using EPD. The aim was to achieve a compressive residual stress field in the silica layer on cooling from sintering temperature, in order to increase composite fracture strength and toughness. The EPD technique proved to be a reliable method for rapid preparation of single layer and multilayer ceramic coatings with reproducible thickness and microstructure on ceramic composite substrates. 相似文献
3.
Xianhua Tian Qihang Sun Xiaodong Yang Qingqing Wang Lei Wang Kun Wu 《International Journal of Applied Ceramic Technology》2024,21(3):2519-2530
Al2O3/TiN/graphene ceramic tool materials were prepared by spark plasma sintering technology and the strengthening and toughening mechanisms were studied. The influence of monolayer graphene content on the mechanical properties and microstructure of the composite material were analyzed and the strengthening and toughening mechanisms were researched. The results showed that with an addition of .5 vol.% graphene the mechanical properties of the material reached the best. The bending strength, hardness, and fracture toughness were 624 MPa, 23.24 GPa, and 6.53 MPa·m1/2, respectively. Graphene existed in the forms of few-layer and multilayer. The toughening mechanism of few-layer graphene was mainly graphene breaking, and that of multilayer graphene included graphene breaking and pulling-out. Graphene could contribute to the uniform growth of grains due to the excellent electrical conductivity and the high thermal conductivity. The addition of nano-TiN introduced many endocrystalline structures and graphene promoted this phenomenon. Micro-TiN grains made the crack extension show a combination of transgranular fracture, intergranular fracture, crack bridging, and crack deflection, while graphene introduced weak grain interfaces and made the crack appear more branches. The layered graphene made the material fracture change from two-dimension to three-dimension. 相似文献
4.
Shuichi Funahashi Hanzheng Guo Jing Guo Amanda L. Baker Ke Wang Kosuke Shiratsuyu Clive A. Randall 《Journal of the American Ceramic Society》2017,100(8):3488-3496
Cold‐sintered ZnO and Ca3Co4O9 polycrystalline materials were shown to have thermoelectric properties comparable to those of conventionally sintered ceramics. Extending these processing conditions into a cold sintering co‐fired ceramic (CSCC) technology, we integrated n‐type and p‐type thermoelectric oxides and a separating insulating layer to demonstrate functional multilayer thermoelectric generator devices. A co‐fired structure with an insulating 8 mol% yttria‐stabilized zirconia (8YSZ) layer enabled multilayer thermoelectric generators (TEG) to be fabricated with a 5 n‐p junction device (20 layers). A transmission electron microscopy analysis of the interfaces between the various materials under the co‐firing cold sintering showed some interdiffusion of chemical constitutes in a 2.0 μm interface region between the respective ceramic phases. The co‐firing of multilayer ceramic and polymer structures were also shown to be possible using insulation layers of polytetrafluoroethylene (PTFE) thermoplastic layers. This demonstrated the feasibility of a single‐step process for new structures with both ceramics and polymers, opening up new directions for many new device designs. 相似文献
5.
Silicon nitride based nanocomposites have been prepared with different amount (1 and 3 wt%) of multilayer graphene (MLG) as well as exfoliated graphite nanoplatelets (xGnP) and nano graphene platelets (Angstron) in comparison. The microstructure and mechanical properties of the graphene reinforced silicon nitride based composite materials have been investigated. Homogeneous distribution of the MLG additives have been observed on the fracture surface of the sintered material. The scanning electron microscopy examinations showed that graphene platelets are inducing porosity in matrix. The bending strength and elastic modulus of MLG/Si3N4 composites showed enhanced values compared to the other graphene added silicon nitride ceramic composites. These observations may be explained by the different type and quality of the starting materials and by the dispersion grade of graphene platelets having direct impact to the resulting density of the sintered samples. 相似文献
6.
《Carbon》2013
Graphene/silicon nitride (Si3N4) composites with high fraction of few layered graphene are synthesized by an in situ reduction of graphene oxide (GO) during spark plasma sintering (SPS) of the GO/Si3N4 composites. The adequate intermixing of the GO layers and the ceramic powders is achieved in alcohol under sonication followed by blade mixing. The reduction of GO occurs together with the composite densification in SPS, thus avoiding the implementation of additional reduction steps. The materials are studied by X-ray photoelectron and micro-Raman spectroscopy, revealing a high level of recovery of graphene-like domains. The SPS graphene/Si3N4 composites exhibit relatively large electrical conductivity values caused by the presence of reduced graphene oxide (∼1 S cm−1 for ∼4 vol.%, and ∼7 S cm−1 for 7 vol.% of reduced-GO). This single-step process also prevents the formation of highly curved graphene sheets during the thermal treatment as the sheets are homogeneously embedded in the ceramic matrix. The uniform distribution of the reduced GO sheets in the composites also produces a noticeable grain refinement of the silicon nitride matrix. 相似文献
7.
《Ceramics International》2016,42(12):14066-14070
Ultrahigh temperature ZrB2-SiCw-Graphene ceramic composites are fabricated by hot pressing ZrB2-SiCw-Graphene oxide powders at 1950 °C and 30 MPa for 1 h. The microstructures of the composites are characterized by Scanning electron microscopy, Raman spectroscopy and X-ray diffraction. The results show that multilayer graphene nanosheets are achieved by thermal reduction of graphene oxide during sintering process. Compared with monolithic ZrB2 materials, flexural strength and fracture toughness are both improved due to the synergistic effect of SiC whisker and graphene nanosheets. The toughening mechanisms mainly are the combination of SiC whisker and graphene nanosheets crack bridging, pulling out. 相似文献
8.
Eszter Bódis Ildikó Cora Péter Németh Orsolya Tapasztó Miklós Mohai Sára Tóth Zoltán Károly János Szépvölgyi 《Ceramics International》2019,45(4):4810-4816
Silicon nitride (Si3N4) ceramics have superior mechanical properties allowing their broad application in many technical fields. In this work, Si3N4-based composites with 1–5?wt% multilayer graphene (MLG) content were fabricated by spark plasma sintering at different temperatures and holding time in order to improve the fracture resistance of the Si3N4 ceramic. Our investigation focused on understanding the relationships between the microstructure and mechanical properties with special attention to the intergranular phases between Si3N4 matrix and MLG reinforcement.We have found that nanopores developed at the Si3N4-MLG interface due to a reaction between carbon and the oxygen available in the topmost layer of the Si3N4 particles. Interface porosity has an optimum for the toughening effect. In 1?wt% MLG/Si3N4 composites nanopores are local, but separated at the Si3N4-MLG interface, which promote the MLG pull-out mechanism imparting a significant toughening effect on the composite. Beyond the optimal 1?wt% MLG content, MLG platelets agglomerate and excessive porosity are developed at the Si3N4-MLG interfaces, leading to weaker matrix- graphene adhesion and thus lower fracture toughness. 相似文献
9.
Titanium diboride (TiB2) is a metal-based refractory ceramic material that has been investigated in industrial applications ranging from cutting tools to wear parts, and for use in the aerospace industry. The unique properties which make this material so fascinating are its high hardness, high melting point and its corrosion resistance. TiB2 is prevented from wider mainstream use because of its inherent brittle nature. With a view to overcome this in coating form and with the aim of providing in addition inherent lubricity, in this study, 50-layer TiB2/C multilayer stacks have been fabricated, with varying volume fractions of ceramic whereby the interfaces of the layers limit crack propagation in the TiB2 ceramic.TiB2 has been multilayered with carbon to make use of the unique and hybrid nature of the bonding in carbon coatings. DC magnetron sputtering with substrate bias was the preferred route for the fabrication of these coatings. AISI tool steel has been used as the substrate material. By varying the amount of TiB2 ceramic from 50% to 95%, the hardness of the coating is seen to increase from 5 to 17 GPa. The hardness is observed to decrease as a function of increasing carbon content, agreeing with other studies that the carbon layers are not load bearing. The graphitic nature of the sp2 bond, however, acts as a lubricant layer. 相似文献
10.
《Carbon》2015
By unzipping multi-walled carbon nanotubes (MWCNTs) it is possible to obtain graphene nanoribbons (GNRs) that could then be used as fillers in ceramic composites. Here we report the fabrication of silicon nitride (Si3N4) ceramics with different contents of GNRs by spark plasma sintering. The GNR fillers confer electrical conductivity to the Si3N4 composites, following a semiconducting-like behavior at relatively low volume filler concentrations (0.04). In addition, a toughening effect, produced by GNRs bridging the cracks was observed. GNRs appear to be an efficient alternative to graphene-based composites, useful in the fabrication of novel multifunctional ceramic composites. 相似文献
11.
《Journal of the European Ceramic Society》2017,37(6):2473-2479
This paper presents a study on graphene-reinforced Al2O3-SiCw ceramic composites and the relationship between graphene oxide (GO) loading and the resulting mechanical and electrical properties. Well-dispersed ceramic-GO powders were fabricated using a colloidal processing route. Dense composites were obtained via spark plasma sintering, a technique that has the ability to reduce GO to graphene in situ during the sintering process. The mechanical properties of the sintered composites were investigated. The composite with only a small amount of graphene (0.5 vol.%) showed the highest flexural strength (904 ± 56 MPa), fracture toughness (10.6 ± 0.3 MPa·m1/2) and hardness (22 ± 0.8 GPa) with an extremely good dispersion of graphene within the ceramic matrix. In addition to these exceptional mechanical properties, the sintered composites also showed high electrical conductivity, which allows the compacts to be machined using electrical discharge machining and thus facilitates the fabrication of ceramic components with sophisticated shapes while reducing machining costs. 相似文献
12.
《Ceramics International》2021,47(22):31222-31228
Inherent brittleness and low mechanical reliability usually inhibit the application of ceramic materials in many structural applications. In this work, we demonstrate that integrating crystallographic texture and second-phase toughening strategies can effectively improve fracture resistance and mechanical reliability in alumina multilayer composites. Composites consisted of equiaxed (1-x)Al2O3-xZrO2 and highly [0001]-textured Al2O3 layers were fabricated, and effects of ZrO2 amount on fracture behavior and mechanical properties of the composites were studied. Increasing ZrO2 amount x results in larger thermal expansion difference between equiaxed and textured layers. The composites with equiaxed layers containing 30 vol% ZrO2 exhibit high apparent fracture toughness Kapt, c ~11.7 MPa·m1/2 and work of fracture γWOF ~1540 J/m2, which correspond respectively to about 260% and 410% enhancements relative to those without ZrO2 addition. Moreover, adding ZrO2 remarkably reduces sensitivity of failure stress to flaw size in the multilayer composites, and the failure stress substantially increases with increasing ZrO2 content. The greatly enhanced mechanical performance achieved here can be mainly attributed to higher magnitude of compressive stresses, more crack bifurcations and longer crack deflection paths within the textured layers. This work can provide important guidelines for developing novel “bio-inspired” materials with improved fracture resistance and flaw tolerance behavior. 相似文献
13.
Alternating pyrolytic carbon/boron nitride (PyC/BN)n multilayer coatings were applied to the KD–II silicon carbide (SiC) fibres by chemical vapour deposition technique to fabricate continuous SiC fibre-reinforced SiC matrix (SiCf/SiC) composites with improved flexural strength and fracture toughness. Three-dimensional SiCf/SiC composites with different interfaces were fabricated by polymer infiltration and pyrolysis process. The microstructure of the coating was characterised by scanning electron microscopy, X–photoelectron spectroscopy and transmission electron microscopy. The interfacial shear strength was determined by the single-fibre push-out test. Single-edge notched beam (SENB) test and three-point bending test were used to evaluate the influence of multilayer interfaces on the mechanical properties of SiCf/SiC composites. The results indicated that the (PyC/BN)n multilayer interface led to optimum flexural strength and fracture toughness of 566.0?MPa and 21.5?MPa?m1/2, respectively, thus the fracture toughness of the composites was significantly improved. 相似文献
14.
Grigor'ev O. N. Koroteev A. V. Klimenko A. V. Mayboroda E. E. Prilutskii E. V. Bega N. D. 《Refractories and Industrial Ceramics》2000,41(11-12):390-395
The influence of the structure and residual stresses on the strength of multilayer composite ceramic materials in the SiC – MeB2 system is studied. The composites are produced using slip casting of thin films, stacking and rolling of packets, and hot pressing. The use of β-SiC makes it possible to obtain SiC layers with a porous arch structure reinforced with columnar crystals. The high relaxation capacity of such structures eliminates the formation of cracks in fabrication of the material and provides a high strength. A thermal shock causes progressive local spalling with formation of spit-outs without macroscopic fracture of the material. A pilot process for fabricating multilayer ceramic composites is described. 相似文献
15.
W.S. Yang L. FusoS. Biamino D. VasquezC. Vega Bolivar P. FinoC. Badini 《Ceramics International》2012,38(2):1011-1018
Silicon carbide multilayer composites containing short carbon fibres (Csf/SiC) were prepared by tape casting and pressureless sintering. C fibres were dispersed in solvents and then mixed with SiC slurry to make green Csf/SiC tape. Triton X-100 was found to be the best one for Toho Tenax HTC124 fibres (with water soluble coating) among BYK-163, BYK-410, BYK-2150, BYK-9076, BYK-9077 and Triton X-100 dispersants. Csf/SiC multilayer composites containing 5 vol.% fibre (mean fibre length of 3, 4.5, and 6 mm) were obtained. Addition of short C fibres seems to worsen the densification process in the Csf/SiC multilayer composites, whereas anisotropy shrinkage in Csf/SiC was also observed. Open pores size was increased slightly after the addition of C fibre but it decreased with the mean fibre length. Mechanical properties were affected by high residual porosity. The addition of short C fibre has not changed the crack deflection at weak interfaces. Csf/SiC multilayer composites containing longer fibres (4.5 and 6 mm) presented higher elastic modulus, bending strength and Vickers hardness as compared to shorter fibres (3 mm). Improved sintering performance and fibre content are necessary to improve mechanical properties. 相似文献
16.
With the aim of improving the toughness of ceramic materials, laminated composites have been successfully developed since Clegg et al. (1990) inserted weak interfaces using very thin graphite layers between silicon carbide sheets and obtained a composite that exhibited non-catastrophic fracture characteristics. The weak interface must allow the crack to deviate either by deflection or delamination; in other words, the interface must exhibit a fracture resistance that is lower than that of the matrix layer. In parallel, ceramic laminated composites with strong interfaces were developed in which the residual tensile and compressive stresses appeared in alternate layers during cooling after sintering. These composites are prepared by stacking ceramic sheets produced by lamination or tape casting or by the sequential formation of layers by slip casting, centrifugation or electrophoretic deposition. The techniques may be combined to obtain a composite with the most adequate configuration. This work presents a review about the obtainment of multilayered ceramic composites as a toughening mechanism of ceramic plates. 相似文献
17.
Linjiang Tang Yanlong Bian Jiwei Zhai Haijun Zhang 《Journal of the American Ceramic Society》2014,97(3):862-867
The correspondence between the theoretical model and the experimental results of the dielectric response in two‐phase composites of Ba0.5Sr0.5TiO3 and Mg2AO4 (A = Ti, Si)was studied. The Ba0.5Sr0.5TiO3 (BST50)/Mg2AO4 composites in 2‐2 model structure consisting of BST50 layers and Mg2AO4 layers were fabricated by tape casting and multilayer technique. The 3‐0 model of the two‐phase composites is fabricated by conventional ball mill mixing and solid‐state reaction process. The ceramics samples with dense structure were obtained because the coefficient of thermal expansion (CTE) of Mg2SiO4 (12.84 ppm/°C) and Mg2TiO4 (12.11 ppm/°C) ceramic specimens are close to the pure BST50(13.15 ppm/°C) ceramic. The microstructure, dielectric, and tunable properties of 2‐2 and 3‐0 model composites were investigated. The experimental results agree well with the theoretical prediction in 2‐2 model. An important feature of 2‐2 model composites is that the DC field is efficiently applied to the high‐permittivity ferroelectric phase. With the increase in Mg2AO4 volume fraction q, the tunability of the composite remains almost unchanged whereas the permittivity greatly reduced in the 2‐2‐//model. These results show that the 2‐2‐//model sample is good candidates for the tunable devices. 相似文献
18.
《Journal of the European Ceramic Society》2017,37(12):3731-3739
This paper reports on anisotropy of functional properties of different silicon carbide-graphene composites due to preferential orientation of graphene layers during sintering. Dense silicon carbide/graphene nanoplatelets (SiC/GNPs) and silicon carbide/graphene oxide (SiC/GO) composites were sintered in the presence of yttria (Y2O3) and alumina (Al2O3) sintering additives at 1800 °C in vacuum by the rapid hot pressing (RHP) technique. It is found that electrical conductivity of SiC/GNPs and SiC/GO composites increases significantly in the perpendicular direction to the RHP pressing axis, reached up to 1775 S/m in the case of SiC/GO (for 3.15 wt.% of rGO). Also, thermal diffusivity was found to increase slightly by the addition of GNPs in the SiC/GNPs composites in the perpendicular direction to the RHP pressing axis. But, in the parallel direction, the addition of GNPs showed a negative effect. The formation of graphene domains was observed in reference sample SiC-Y2O3-Al2O3 sintered by RHP, without any addition of graphene. Their presence was confirmed indirectly by increasing electrical conductivity about three orders of magnitude in comparison to the reference sample sintered by conventional hot press (HP). Raman, SEM and TEM analysis were used for direct evidence of presence of graphene domains in RHP reference sample. 相似文献
19.
《Journal of the European Ceramic Society》2019,39(12):3491-3497
Hierarchical tantalum-graphene flakes reinforced zirconia (3Y-TZP) ceramic matrix composites were fabricated by wet processing route and freeze drying followed by spark plasma sintering (SPS). The microstructures and mechanical properties were investigated. The results show that graphene and Ta particles are homogeneously dispersed in the ceramic matrix and the optimum sintering temperature for complete densification of composites and thermal reduction of the graphene oxide is 1500 °C. The addition of dual reinforcements of tantalum microflakes and graphene nanoflakes results in significant improvement in the mechanical properties of the ZrO2 matrix. Approximately a 30% increase in flexural strength vs the zirconia-Ta composite and a 175% increase in fracture toughness vs the monolithic zirconia have been achieved by introducing 0.5 vol% GO and 20 vol% Ta particles. 相似文献
20.
《Ceramics International》2020,46(6):7001-7008
The SiBCN ceramic aerogel/graphene composites were synthesized by combining a simple sol-gel infiltration process with CO2 supercritical drying technology and polymer-derived ceramics route. In order to select the best preceramic sample for sintering, the micromorphology of PSNB aerogel/graphene composites fabricated with different graphene oxide solution concentrations were investigated. The microstructure evolution of the prepared SiBCN ceramic aerogel/graphene composites and phase composition were studied by SEM, TEM and XRD, the pore structure of the preceramic composites pyrolyzed at 1200 °C was tested by specific surface area and pore size analyzer. Furthermore, the compressive strain-stress curve and toughening mechanisms of composites were also investigated in detail. The results showed that all the preceramic composites and obtained ceramic aerogel composites possessed the mesoporous structure. The basic structure of SiBCN aerogel network changed from the initial spherical particles accumulation to the nanowires lapping with the sintering temperature increased from 800 °C to 1200 °C. After pyrolyzing at 1200 °C, the specific surface area and pore volume for the sample were 101.61 m2 g−1 and 1.43 cm3 g−1, respectively, and a small amount of β-SiC crystalline phases were formed in amorphous ceramic matrix and had an relatively uniform distribution. Moreover, the paepared ceramic aerogel composites possessed a certain degree of toughness, the toughening mechanisms of composite samples mainly included the crack deflection, graphene pull-out, graphene bridging and graphene crumpling. 相似文献