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1.
Teng-Teng Xu Su Cheng Lai-Zhen Jin Kun Zhang Tao Zeng 《International Journal of Applied Ceramic Technology》2020,17(2):438-448
Silicon carbide (SiC) ceramics, as a kind of candidate material for aero-engine, its high-temperature performance is a critical factor to determine its applicability. This investigation focuses on studying the high-temperature properties of SiC ceramics fabricated by using additive manufacturing technology. In this paper, SiC ceramics were prepared by combining selective laser sintering (SLS) with precursor infiltration and pyrolysis (PIP) technique. The microstructure, phase evolution, and failure mechanism after high-temperature tests were explored. SiC ceramic samples tested at room temperature (RT), 800°C, 1200°C, 1400°C, and 1600°C demonstrated bending strengths of 220.0, 226.1, 234.9, 215.5, and 203.7 MPa, respectively. The RT strength of this material can be maintained at 1400°C, but it decreased at 1600°C. The strength retention at 1400°C and 1600°C were 98% and 92%, respectively. The results indicate that the mechanical properties of SiC ceramics prepared using this method have excellent stability. As the temperature increases, the bending strength of the specimens increased slightly and reached the peak value at 1200°C, and dropped to 203.7 MPa at 1600°C. Such an evolution could be mainly due to the crack healing, and the softening of the glassy phase. 相似文献
2.
《Journal of the European Ceramic Society》2007,27(2-3):575-579
Ceramic materials with a perovskite related structures such as non-doped and doped barium titanate ceramics are attracting much interest for their application as capacitor dielectrics, resistors, thermal sensors, etc. Since mechanical activation can be used in order to modify properties of these materials, in this study microstructure evolution and electric properties of mechanically activated BaTiO3 have been analyzed. The sintering process of high purity non-doped mechanically activated BaTiO3 was monitored using a sensitive dilatometer with a heating rate of 10 °C/min. Investigation of the microstructure evolution of mechanically activated BaTiO3 was performed using scanning electron microscope (SEM) and digital pattern recognition (DPR) methods. A dielectric study of the paraelectric–ferroelectric phase transition in the barium titanate ceramics was performed by recording the temperature dependence of dielectric permittivity. 相似文献
3.
《Journal of the European Ceramic Society》2020,40(8):3222-3234
A novel phenomenon is found that the grain growth of aluminum-rich magnesium aluminate is suppressed to 5 μm, despite of high-temperature hot-isostatic-press at 1750 °C. For the transparent MgO-nAl2O3 (n = 1.2, 1.5, 2.0), the transmittance and strength tended to be enhanced with increasing Al2O3 content, having the highest values 80 % at 550 nm and 214.3 MPa for n = 2.0. This is due to the different microstructural evolution depending on the composition. When the excessive Al2O3 was small, the inhomogeneous microstructure with bimodal grain size and lots of rod-shaped particles were observed. However, as the Al2O3 amount increased, the microstructure became homogeneous with reducing the grain size and the rod-shaped particles. The microstructural and compositional analysis revealed that the rod-shaped particle were generated due to the trace potassium impurity as well as the different cationic diffusion rate, and the suppression of grain growth was induced by the severe Al segregation at the grain-boundaries. 相似文献
4.
《Ceramics International》2020,46(14):22127-22133
In the present study, we incorporated AlN (5 wt%) with TiB2 ceramic and consolidated the mixture by relatively low temperature sintering method, resulting in a near fully dense composite. Monolithic TiB2 and TiB2–AlN (5 wt%) were manufactured by spark plasma sintering (SPS) at 1900 °C for 7 min under 40 MPa. The prepared composites were precisely characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analyses. In addition, possible chemical reactions during the sintering process were thermodynamically assessed using the HSC Chemistry software. The addition of AlN influenced the sinterability of titanium diboride, yielding a relative density of 99.7%. XRD results revealed the in-situ formation of h-BN during the sintering, whereas thermodynamic studies suggested the formation of both Al2O3 and h-BN. Furthermore, the microstructural investigation verified the synthesis of both Al2O3 and h-BN phases. Finally, the fractographical study revealed the effective role of AlN additive for refining the microstructure of TiB2. 相似文献
5.
Zhiheng Xing Daoping Xiang Yanping Ma 《Journal of the European Ceramic Society》2018,38(15):4842-4849
In this paper, porous SiC ceramics (PSCs) were fabricated from photovoltaic waste at low temperatures. The effects of different additives and sintering temperatures on PSCs were studied in detail. The temperature of PSCs preparation can be reduced to 850?°C by adding MoO3 as catalyst. The PSCs are reinforced by mullite rods grown in-situ, they also have a high permeability coefficient due to their network structure. From 850?°C to 1200?°C, the open porosity of PSCs changed slightly, and was within 45.32?±?0.6%. The PSCs produced at 1000?°C had the highest gas permeability coefficient of 8.24?×?10–11?m2 and the highest flexural strength of 50.17?MPa. However, the same PSCs could not be fabricated at 850?°C when Y2O3 or CeO2 were used as sintering aids. This study provides an environment-friendly method for reusing photovoltaic waste and reducing the cost of preparing PSCs. 相似文献
6.
Processing and properties of porous SiC ceramics prepared by yttrium aluminum garnet infiltration
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Sanchita Baitalik Nijhuma Kayal Omprakash Chakrabarti 《International Journal of Applied Ceramic Technology》2017,14(4):652-664
Oxide bonded porous SiC ceramics were synthesized by infiltrating a liquid precursor of yttrium aluminum garnet into porous powder compact of SiC followed by sintering at 1300‐1500°C in air. Infiltration rate was estimated using weight gain by the liquid precursor sol into porous SiC powder compact as a function of time and was explained by Darcy's and Ficks's laws. The effects of SiC particle sizes and sintering temperatures on the formation of bonding phases, microstructure, SiC oxidation degree, flexural strength, porosity, and pore size distribution of porous SiC ceramics were studied. Various crystalline oxide phases were detected by XRD analysis. Depending on the starting SiC powder sizes and sintering temperatures, the porosity of the final ceramics varied nearly in the range of ~29‐41 vol. % with the variation of average pore diameter between ~5 and 30 μm. Flexural strength varied from 41 to 8 MPa depending on porosity. The effect of corrosion on oxide bond phases was investigated in strong acidic and basic medium at 90°C. The ceramics showed better corrosion resistance in acidic medium compared to basic medium. In basic medium, significant reduction in flexural strength (~42%) was arisen. 相似文献
7.
《Ceramics International》2020,46(11):18924-18932
This investigation intends to study the influence of titanium nitride (TiN) additive on the sintering behavior, mechanical features and microstructural development of TiC-based substances. For this objective, two different samples, namely monolithic TiC and TiC-5 wt% TiN, were sintered at 1900 °C using the SPS method. The specimens were held at the ultimate temperature for 10 min under 40 MPa. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were implemented to characterize the as-produced specimens. Introducing TiN increased the relative density of TiC by around 1.5%, standing next to 97%. The assessments revealed the creation of non-stoichiometric TiC1-x along with some graphitized carbon phases in the undoped ceramic. By contrast, TiN additive completely dissolved into the TiC matrix in the composite sample and a new in-situ phase (C3N4) appeared. Finally, a Vickers hardness of ~2750 HV0.1 and a flexural strength of ~450 MPa were achieved for the TiN-doped specimen. 相似文献
8.
Huaxin Li Weijian Shen Fuquan Yang Chuanyang Lu Wenjian Zheng Yinghe Ma Sendong Ren Yanming He Jianguo Yang 《International Journal of Applied Ceramic Technology》2022,19(6):3376-3391
Nitrogen (N)-doped conductive silicon carbide (SiC) of various electrical resistivity grades can satisfy diverse requirements in engineering applications. To understand the mechanisms that determine the electrical resistivity of N-doped conductive SiC ceramics during the fast spark plasma sintering (SPS) process, SiC ceramics were synthesized using SPS in an N2 atmosphere with SiC powder and traditional Al2O3–Y2O3 additive as raw materials at a sintering temperature of 1850–2000°C for 1–10 min. The electrical resistivity was successfully varied over a wide range of 10−3–101 Ω cm by modifying the sintering conditions. The SPS-SiC ceramics consisted of mainly Y–Al–Si–O–C–N glass phase and N-doped SiC. The Y–Al–Si–O–C–N glass phase decomposed to an Si-rich phase and N-doped YxSiyCz at 2000°C. The Vickers hardness, elastic modulus, and fracture toughness of the SPS-SiC ceramics varied within the ranges of 14.35–25.12 GPa, 310.97–400.12 GPa, and 2.46–5.39 MPa m1/2, respectively. The electrical resistivity of the obtained SPS-SiC ceramics was primarily determined by their carrier mobility. 相似文献
9.
《Journal of the European Ceramic Society》2007,27(6):2521-2527
Effect of the content of the intergranular phase (Y3Al5O12 or yttrium aluminum garnet or YAG) on the room-temperature contact-mechanical properties of pressureless, liquid-phase-sintered (LPS) α-SiC ceramics has been studied. An increase in YAG vol.% is found to result in the expected degradation of the elastic modulus and the indentation yield strength in LPS SiC. However, with increasing YAG vol.% the degradation in the hardness and the sliding-wear resistance is found to be severe, while the indentation toughness first increases and then decreases. These results are analyzed, and discussed in the context of providing guidelines for the design and fabrication of low-cost LPS SiC ceramics with tailored contact-mechanical properties. 相似文献
10.
SiCpowder/Simatrix composites represent a new class of microstructurally toughened materials. The interactions between molten silicon and submicronic SiC powder have been considered since it could originate some limitations on the final properties of the material. Experiments putting in interaction a SiC powder and molten Si were performed while heating up to final values ranging between 1450 and 1600?°C for duration up to 8?h. The volume ratio of SiC and silicon was equal to one and SiC particles were freely dispersed within the liquid. X-ray diffraction analyses demonstrated that the apparent crystallites size increase of SiC powder followed a ripening law corresponding to a limitation either by volume diffusion or by dissolution into the liquid. Depending on the relevant mechanism, the activation energy of the crystallites’ growth has been found equal to 357?±?50?kJ?mol?1 or 441?±?57?kJ?mol?1. An agglomeration-coarsening process of SiC particles was also identified which promoted a quick formation of larger particles. 相似文献
11.
《Journal of the European Ceramic Society》2002,22(14-15):2669-2675
Silicon carbide ceramics incorporating sintering additives from the system AlN–Y2O3 can be gas-pressure sintered to theoretical density. While commonly a combination of sesquioxides is used such as Al2O3–Y2O3, oxynitride additives offer the advantage that only a moderate nitrogen overpressure is required instead of a powder bed for thermochemical stabilization at the sintering temperature. In the present study aspects of the fracture behavior of these materials are addressed, namely the influence of anisotropic grain growth and processing flaws, additional toughening at high temperatures and thermal shock characteristics. They are correlated with microstructural data obtained by scanning electron microscopy. 相似文献
12.
A.L. Ortiz O. Borrero-LópezM.Z. Quadir F. Guiberteau 《Journal of the European Ceramic Society》2012,32(4):965-973
A colloidal processing route has been developed for the pressureless sintering of dense SiC with a low content of sintering additives. In this route, a sol-gel solution precursor of the sintering additives is deposited onto the surface of the SiC particles, achieving a uniform distribution of the sintering additives in the green compact. This in turn promotes complete densification at short sintering times, which is not otherwise achievable when the batch is prepared by the standard method of mechanically mixing powders. It is also shown that the resulting ceramic has improved sliding-wear resistance compared to its counterpart prepared by the classical method, with essentially the same rate of mild and severe wear but a notably delayed transition from the mild to the severe wear regimes. This improvement is attributed to the reduction in the microstructural defect size achieved by the colloidal processing. Implications for the fabrication of low-cost SiC ceramics for wear-resistance applications are discussed. 相似文献
13.
《Ceramics International》2016,42(3):4526-4531
Porous SiC ceramics were prepared by freeze-casting process. In order to enhance the mechanical properties of the porous SiC, poly(vinyl alcohol) (PVA) was added as binder and pore morphology controller in this work. The results indicated that high porosity (>60%) SiC ceramics was obtained although the sintering temperature was over 2000 °C. The pore structure could be divided into two kinds: macropores generated by sublimation of large ice crystals, and micropores in the ceramic matrix caused by sublimating of small ice crystals, stacking of SiC particles, and burning out of PVA. With the increase of the sintering temperature, the specimens exhibited higher density, thus resulted in higher strength. Porous SiC ceramics sintered at 2100 °C showed a good flexural strength of 11.25 MPa with an open porosity as high as 66.46%. 相似文献
14.
《Journal of the European Ceramic Society》2007,27(13-15):3991-3995
The abnormal grain growth (AGG) behavior of undoped and SiO2-doped CaCu3Ti4O12 (CCTO) ceramics were investigated. With the addition of 2 wt.% SiO2, the AGG-triggering temperature decreased from 1100 to 1060 °C, and the temperature for obtaining a uniform and coarse microstructure decreased from 1140 to 1100 °C. The lowering of the AGG temperature by SiO2 addition was attributed to the formation of a CuO-SiO2-rich intergranular phase at lower temperature. The apparent dielectric permittivity of coarse SiO2-doped CCTO ceramics was ∼10 times higher than that of fine SiO2-doped CCTO ceramics at the frequency of 103–105 Hz. The doping of SiO2 to CCTO ceramics provides an efficient route of improving the dielectric properties via grain coarsening. The correlation between the microstructure and apparent permittivity suggests the presence of a barrier layer near the grain boundary. 相似文献
15.
《Journal of the European Ceramic Society》2020,40(9):3380-3390
A novel TiB2-based ultra-high-temperature ceramic containing 60 vol.% TiB2, 20 vol.% TiC, and 20 vol.% SiC was fabricated by hot pressing and subsequently joined using the brazing technique. Ti-based filler was used as the brazing alloy by taking advantage of the reaction between Ti and TiB2-TiC-SiC. The effects of the brazing temperature on the microstructure and mechanical properties of the brazed joint were investigated. The results showed that Ti in the filler reacted with the TiB2-TiC-SiC ceramics and formed a reaction layer I that comprised TiB and TiC. The brazing seam was composed of TiB, TiC, Ti5Si3, Ti2Ni, and TiNi. When the brazing temperature was increased, the reaction between TiB2-TiC-SiC ceramics and the filler was observed to become vigorous; this led to an increase in the growth of the reaction layer I. Meanwhile, the continuous Ti2Ni layer in the brazing seam gradually disappeared; it was replaced by TiB and Ti5Si3. The room temperature shear strength reached a maximum value of 168 MPa when the joint was brazed at 1040 °C for 30 min; while it was 104 and 81 MPa at test temperature of 600 °C and 800 °C, respectively. In addition, the effects of TiB whiskers on the coefficient of thermal expansion of the brazing seam and fracture of the brazed joint were discussed. 相似文献
16.
α- and β-SiC starting powders of similar particle sizes were used to investigate the effect of initial α-phase content on the electrical, thermal, and mechanical properties of pressureless solid-state sintered (PSS) SiC ceramics with B4C and C additives. For β-SiC starting powders, a coarse-grained microstructure with elongated platelet grains was formed by the transformation of 3C to 6H and finally to 4H-SiC phase. In contrast, materials prepared from α-SiC powders exhibited a fine-grained microstructure with platelet grains. This study revealed the beneficial effect of α-SiC starting powders in achieving low electrical resistivity and high thermal conductivity in PSS SiC ceramics, which was attributable to their higher sinterability, lower impurity content, and lower 6H to 4H-SiC phase transformation rate compared with β-SiC powders. The electrical resistivity decreased by an order of magnitude and the thermal conductivity increased by 32% with an increase in initial α-phase content from 0 to 100%. The flexural strength increased by approximately 16% with increasing initial α-phase content due to a decreased flaw size with decreasing grain size. However, the fracture toughness and hardness were insensitive to the change in initial α-phase content. 相似文献
17.
《Journal of the European Ceramic Society》2017,37(6):2459-2463
Cr (0.2 at.%) and Nd (0.8 at.%) co-doped Lu3Al5O12 ceramics were fabricated with MgO as the sintering additive. The addition of a small amount of MgO can affect the grain boundary mobility and influence the number and location of micropores in ceramics during the sintering process. The results show that when the MgO content is 0.02 wt.%, high-transparency Cr,Nd:LuAG ceramics can be obtained by vacuum sintering at 1670 °C for 5 h followed by hot isostatic pressing (HIP) post-sintering at 1750 °C in an argon atmosphere (P = 200 MPa) for 5 h. The optimum in-line transmittance of the HIPed Cr,Nd:LuAG ceramics (3 mm thick) is 83.5% at a wavelength of 840 nm and 84.0% at 710 nm. 相似文献
18.
《Journal of the European Ceramic Society》2017,37(13):4217-4221
Si3N4-ZrB2 ceramics were hot-pressed at 1500 °C using self-synthesized fine ZrB2 powders containing 2.0 wt% B2O3 together with MgO-Re2O3 (Re = Y, Yb) additives. Both Si3N4 and ZrB2 grains in the hot-pressed ceramics were featured with elongated and equiaxed morphology. The presence of elongated Si3N4 and ZrB2 grains led to the partial texture of the ceramics under the applied pressure. Vickers hardness and fracture toughness of Si3N4-ZrB2 ceramics with MgO-Re2O3 additives prepared at low temperature were about 19–20 GPa and 9–11 MPa m1/2, respectively, higher than the reported values of Si3N4-based ceramics prepared at high temperature (1800 °C or above) under the same test method. 相似文献
19.
《Journal of the European Ceramic Society》2023,43(13):5446-5457
Complex silicon carbide (SiC) ceramic components are difficult to fabricate due to their strong covalent bonds. Binder jetting (BJ) additive manufacturing has the outstanding advantages of high forming efficiency and no thermal deformation, especially suitable for printing complex structure SiC components. This study tried to obtain low silicon content silicon carbide ceramics by binder jetting followed by phenolic resin impregnation and pyrolysis (PRIP) and liquid silicon infiltration (LSI). BJ was used for the SiC green parts fabrication, and the highest compressive strength (7.7 ± 0.3 MPa) and lowest dimensional deviations (1.2–1.6 mm) were obtained with the printing layer thickness of 0.15 mm. Subsequently, PRIP treatments were introduced to increase the carbon content for the following LSI process. As the number of PRIP cycles increased, the carbon density of SiC/C preform increased and the porosity decreased. After the LSI treatment, the final Si-SiC composites processed with 2 PIRP cycles reached the highest flexural strength (257 ± 14.26 MPa) and the best wear resistance. This was attributed to the low residual silicon content (10.2 vol%) and almost no residual carbon. Furthermore, several complex structural components were fabricated using these methods. The preparation of complex components verifies the feasibility of BJ and LSI for manufacturing high-strength and high-precision SiC ceramics. Besides, this work hopes to provide technical guidance for the preparation of complex SiC composites in the future. 相似文献
20.
S.V. Amrut Raj Dulal Chandra Jana Prasenjit Barick Bhaskar Prasad Saha 《Ceramics International》2018,44(8):9221-9226
The densification and phase formation of 6?wt% Y2O3 containing SiC compacts infiltrated by aluminium vapour were investigated. The densification occurred through infiltration of aluminium vapour that formed through a reaction between alumina and carbon powders at 2000?°C. Infiltrated specimens were evaluated concerning the density, phase, microstructure and mechanical properties including hardness and fracture toughness. X-ray diffraction studies showed the presence of yttrium aluminium garnet (YAG) and Al2O3 as the secondary phases along with other minor phases. Sectioning of the infiltrated specimen showed two regions: a dense layer starting from the surface of about 1?mm thickness followed by a relatively porous structure at the core. The effect of infiltration depth on densification and evolution of microstructure are studied. Also, the changes in Vickers’ hardness and fracture toughness with the increase in specimen depth are discussed. 相似文献