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《Ceramics International》2022,48(20):30376-30383
In this study, α/β-Si3N4 composite ceramics with high hardness and toughness were fabricated by adopting two different novel ternary additives, ZrN–AlN–Al2O3/Y2O3, and spark plasma sintering at 1550 °C under 40 MPa. The phase composition, microstructure, grain distribution, crack propagation process and mechanical properties of sintered bulk were investigated. Results demonstrated that the sintered α/β-Si3N4 composite ceramics with ZrN–AlN–Al2O3 contained the most α phase, which resulted in a maximum Vickers hardness of 18.41 ± 0.31 GPa. In the α/β-Si3N4 composite ceramics with ZrN–AlN–Y2O3 additives, Zr3AlN MAX-phase and ZrO phase were found and their formation mechanisms were explained. The fracture appearance presented coarser elongated β-Si3N4 grains and denser microstructure when 20 wt% TiC particles were mixed into Si3N4 matrix, meanwhile, exhibited maximum mean grain diameter of 0.98 ± 0.24 μm. As a result, the compact α/β-Si3N4 composite ceramics containing ZrN–AlN–Y2O3 additives and TiC particles displayed the optimal bending strength and fracture toughness of 822.63 ± 28.75 MPa and 8.53 ± 0.21 MPa?m1/2, respectively. Moreover, the synergistic toughening of rod-like β-Si3N4 grains and TiC reinforced particles revealed the beneficial effect on the enhanced fracture toughness of Si3N4 ceramic matrix. 相似文献
14.
Aniruddha Nag Mohammed Asif Ali Jiabei Zhou Makoto Ogawa Tatsuo Kaneko 《大分子材料与工程》2021,306(11):2100459
Aromatic and functional polymers with processibility derived from biobased starting materials are prerequisite considering sustainable society. Poly(2,5-benzimidazole)s are rigid-rod polymers to show ultrahigh thermal stability such as flame retardance, while usually suffer from poor solubility. Here, poly(benzimidazole-co-amide)s are synthesized from two biobased monomers, 3,4-diaminobenzoic acid and a semirigid comonomer, 4-aminohydrocinnamic acid. The copolymers with an amide composition of 80 mol% and higher are soluble in widely used polar solvents to fabricate the films keeping high flame retardance, which is comparable with popular high-performance polymers such as aromatic polyimides, polyetheretherketone, polyphenylene sulfide, etc. 相似文献
15.
This paper reports an investigation on the structure-properties correlation of trivalent metal oxide (Al2O3)-doped V2O5 ceramics synthesized by the melt-quench technique. XRD patterns confirmed a single orthorhombic V2O5 phase formation with increasing strain on the doping of Al2O3 in place of V2O5 in the samples estimated by Williamson-Hall analysis. FTIR and Raman investigations revealed a structural change as [VO5] polyhedra converts into [VO4] polyhedra on the doping of Al2O3 into V2O5. The optical band gap was found in a wide semiconductor range as confirmed by UV–visible spectroscopy analysis. The thermal and conductivity behavior of the prepared samples were studied using thermal gravimetric analysis (TGA) and impedance analyzer, respectively. All the prepared ceramics exhibit good DC conductivity (0.22–0.36 Sm-1) at 400 ?C. These materials can be considered for intermediate temperature solid oxide fuel cell (IT-SOFC)/battery applications due to their good conductivity and good thermal stability. 相似文献
16.
《Ceramics International》2022,48(8):10733-10740
Multivalent ion-conducting ceramics are required for the manufacture of high-safety, high-capacity rechargeable batteries. However, the low ionic conductivity of solid electrolytes and discrepancies in the thermal expansion between the battery components limit their widespread application. Furthermore, anisotropic thermal expansion in crystals during battery manufacturing and the charge-discharge cycles causes the formation of microcracks, which degrade the battery performance. The physical properties of ceramic materials with anisotropic crystal structures can be modified by varying the crystallographic orientation of their grains. In this study, a co-precipitation approach was used to synthesize an Mg2+-conducting (Mg0.1Hf0.9)4/3.8Nb(PO4)3 solid electrolyte, and the grain orientation in the bulk sample was controlled using strong magnetic fields during the slip casting process. The results showed that inducing an orientation along the c-axis enhanced the apparent ionic conductivity of the bulk sample. It was also observed that (Mg0.1Hf0.9)4/3.8Nb(PO4)3 crystal has a negative volumetric thermal expansion despite a positive linear thermal expansion along its c-axis. By adjusting the c-axis orientation of the grains, (Mg0.1Hf0.9)4/3.8Nb(PO4)3 electrolytes with negative or positive linear thermal expansion coefficient have been produced. The findings of this study suggest that solid-electrolytes with negative, positive, or zero linear thermal expansion can be produced to create more compatible and higher-performance solid-state devices. 相似文献
17.
《Ceramics International》2021,47(23):33353-33362
High thermal conductivity Si3N4 ceramics were fabricated using a one-step method consisting of reaction-bonded Si3N4 (RBSN) and post-sintering. The influence of Si content on nitridation rate, β/(α+β) phase rate, thermal conductivity and mechanical properties was investigated in this work. It is of special interest to note that the thermal conductivity showed a tendency to increase first and then decrease with increasing Si content. This experimental result shows that the optimal thermal conductivity and fracture toughness were obtained to be 66 W (m K)-1 and 12.0 MPa m1/2, respectively. As a comparison, the nitridation rate and β/(α+β) phase rate in a static pressure nitriding system, i.e., 97% (MS10), 97% (MS15), 97% (MS20) and 8.3% (MS10), 8.3% (MS15), 8.9% (MS20), respectively, have obvious advantages over those in a flowing nitriding system, i.e., 91% (MS10), 91% (MS15), 93% (MS20) and 3.1% (MS10), 3.3% (MS15), 3.3% (MS20), respectively. Moreover, high lattice integrity of the β-Si3N4 phase was observed, which can effectively confine O atoms into the β-Si3N4 lattice using MgO as a sintering additive. This result indicates that one-step sintering can provide a new route to prepare Si3N4 ceramics with a good combination of thermal conductivity and mechanical properties. 相似文献
18.
Lindsey Yue Alicia Bayon Wojciech Lipiński 《American Institute of Chemical Engineers》2021,67(8):e17267
The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size. 相似文献
19.
华治国 《混凝土与水泥制品》2020,(6):70-72
选择了几份典型的外墙外保温系统标准,通过对这几份标准中胶粘剂和抹面胶浆的成型和检测方法的比较,分析了现有检测技术的优劣,并结合工作实践提出了建议。 相似文献
20.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献