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1.
In this paper, TiO2 was introduced into boron carbide and B4C-based ceramic composites were obtained by uniaxial hot pressing. The mechanical properties, relative density and erosion behaviour of B4C-based ceramic composites were investigated. X-ray analysis showed that the fabricated composites were composed of B4C, TiB2 and C phases. SEM technique was employed to observe the original polished surfaces and the eroded surfaces of B4C-based ceramic composites. The effect of impingement angle, impact velocity of SiC erodent particle, relative density and phase ratio on the erosion rate of B4C-based ceramic composites was determined. It was found that the erosion rate of B4C-based ceramic composites increased with increasing of impingement angle and erodent particle velocity. The relative density and phase ratio influenced the erosion rate of B4C-based ceramic composites significantly by influencing their mechanical properties. 相似文献
2.
In order to enhance the mechanical properties of B4C without density increase, the short carbon fibers M40, M55J and T700 reinforced B4C ceramic composites were fabricated by hot-pressing process. The addition of the carbon fibers accelerates the densification of the B4C, decreases their densities, and improves their strength and toughness. The enhancement effects of the three kinds of carbon fibers were studied by investigating the density, Vickers hardness and the mechanical properties such as flexural strength, flexural modulus and fracture toughness of the composites. The fiber type has a great influence on the mechanical properties and enhancement of the short carbon fiber reinforced B4C composites. The flexible carbon fiber with high strength and low modulus such as T700 is appropriate to reinforce the B4C matrix ceramic composites. 相似文献
3.
S.G. HuangK. Vanmeensel O. Van der BiestJ. Vleugels 《Journal of the European Ceramic Society》2011,31(4):637-644
B4C composites with 15 and 30 vol% TiB2 were pulsed electric current sintered from B4C-TiO2-carbon black mixtures in vacuum at 2000 °C. Full densification could be realised when applying an optimized loading cycle in which the maximum load is applied after completion of the B4C-TiB2 powder synthesis, allowing degassing of volatile species. The influence of the sintering temperature on the phase constitution and microstructure during synthesis and densification was assessed from interrupted sintering cycles. The in situ conversion of TiO2 to TiB2 was a complex process in which TiO2 is initially converted to TiB2 with B2O3 as intermediate product at 1400-1700 °C. At 1900-2000 °C, B2O3 reacted with C forming B4C and CO. The B4C and TiB2 grain size in the fully densified 30 vol% TiB2 composite was 0.97 and 0.63 μm, combining a Vickers hardness of 39.3 GPa, an excellent flexural strength of 865 MPa, and modest fracture toughness of 3.0 MPa m1/2. 相似文献
4.
Dense Ti3AlC2/TiB2 composites were successfully fabricated from B4C/TiC/Ti/Al powders by spark plasma sintering (SPS). The microstructure, flexural strength and fracture toughness of the composites were investigated. The experimental results indicate that the Vickers hardness increased with the increase in TiB2 content. The maximum flexural strength (700 ± 10 MPa) and fracture toughness (7.0 ± 0.2 MPa m1/2) were achieved through addition of 10 vol.% TiB2, however, a slight decrease in the other mechanical properties was observed with TiB2 addition higher than 10 vol.%, which is believed to be due to TiB2 agglomeration. 相似文献
5.
Song Zhang Wenzhong LuChuanbin Wang Qiang ShenLianmeng Zhang 《Ceramics International》2012,38(2):895-900
Approximately 400 nm grain sized boron-carbon ceramic was synthesized by the pulsed electric current sintering (PECS) method using boron and carbon powders. Relative density of up to 95% was achieved at sintering temperature of 1900 °C. This ceramic was composed with B13C2 as major phase and few B4C and C, which were characterized by X-ray diffraction (XRD) and Rietveld refinement quantitative analysis and chemical analysis (CA) and electron probe microanalysis (EPMA). The microstructure was also observed via transmission electron microscope (TEM). 相似文献
6.
Boron carbide ceramics used as neutron absorbing materials in fast breeder reactor were fabricated with boron carbide powders and different rare-earth oxide additives by pressureless sintering. The effects of rare-earth oxide as well as phenolic resin on densities and mechanical properties of the composites were studied. The addition of Dy2O3, Eu2O3, and Sm2O3 was found to be beneficial in the densification of B4C ceramics. B4C with 4 wt% rare-earth oxide and 18 wt% phenolic resin, exhibiting bulk density of 90–96% T.D., flexural strength of 276–358 MPa, could be prepared by pressureless sintering at 1960–2080 °C, which are capable of meeting the requirement of fast breeder reactor. 相似文献
7.
《Journal of the European Ceramic Society》2023,43(9):4215-4218
Highly densified Al4SiC4 ceramics with a relative density of 96.1% were prepared by pressureless sintering using 2 wt% Y2O3 as additives. The densification mechanism, phase composition, microstructures and mechanical properties of Al4SiC4 ceramics were investigated. Y2O3 in-situ reacted with the oxygen impurities in Al4SiC4 powder to form a yttrium aluminate liquid phase during sintering, which promoted the densification and anisotropic grain growth. The final Al4SiC4 ceramics were composed of equiaxed grains and columnar grains, and presented a bimodal grain distribution. The mechanical properties of the pressureless sintered Al4SiC4 ceramics were better than those reported for hot pressed Al4SiC4, including a flexural strength of 369 ± 24 MPa, fracture toughness of 4.8 ± 0.1 MPa m1/2 and Vickers hardness of 11.3 ± 0.2 GPa. Pressureless sintering of Al4SiC4 ceramics is of great significance for the development and practical application of Al4SiC4 ceramic parts, especially with big size and complex shape. 相似文献
8.
Silicon carbide whisker (SiCw) toughened B4C composites have been prepared by pressureless infiltration of B4C–SiCw–C preforms with molten silicon under vacuum at 1500 °C. The effect of SiCw addition on bulk density, hardness, bending strength, fracture toughness and microstructure of SiCw/B4C composites is discussed. It is revealed that the addition of SiCw improves the fracture toughness of B4C ceramic, but reduces its bending strength at the same time. The maximum fracture toughness for SiCw/B4C composite with 24 wt% SiCw addition is 4.88 MPa m1/2, which is about 9% higher than that of the one without SiCw, but at the same time, the bending strength reduces to the minimum value 243 MPa, reduced by 25%. XRD analysis shows that the phase composition of reaction bonded SiCw/B4C composites is B4C, SiC, Si, and B12 (C, Si, B)3, with no residual C. And the main toughening mechanism of SiCw is whisker pulling up. 相似文献
9.
《Journal of the European Ceramic Society》2020,40(12):4354-4360
Superhard composites of B4C reinforced with randomly-oriented reduced graphene oxide (rGO) nanoplatelets are manufactured by a near-net-shape fabrication route based on three successive steps. Firstly, aqueous colloidal processing is used for the environmentally-friendly preparation of a semi-concentrated multi-component slurry (B4C as main component, Ti-Al as sintering additive, and rGO as toughening reinforcement), whose suitability for wet shaping is demonstrated by rheological measurements. Secondly, slip casting is used to produce robust green parts with shapes on demand and microstructures free of macro- and micro-defects. And thirdly, pressureless spark-plasma sintering (PSPS) is used for the ultrafast and energy-efficient densification of the green parts with shape retention. Measurements of shrinkage and hardness, as well as the microstructural observations, are used to identify suitable PSPS temperatures leading to obtaining isotropic B4C/rGO composites that are superhard and almost twice as tough as the monolithic B4C ceramics. 相似文献
10.
High density bulk zirconium diboride was successfully produced by pressureless sintering with the Ni additive as sintering aid. Microstructure and phase formation were investigated by using scanning electron microscopy and X-ray diffractometry respectively. Microhardness, fracture toughness and compressive strength of the sintered samples were measured. Results showed that the higher Ni content led to higher densification, fracture toughness and hardness and lower compressive strength. A significant grain growth was observed during sintering at 2000°C, which may be due to the oxygen impurity in the surface of particles. The addition of 1 wt-%C led to oxygen removing and smaller grains after sintering. 相似文献
11.
Mechanical properties of different compositions obtained from the additions of 5, 10, 20 and 30 wt.% zircon (ZrSiO4) into the MgO-spinel composite refractories and ZrO2 into MgO have been examined, the variations that occurred have been determined, and the parameters affecting those factors have been investigated with the reasons. The density, strength, Young's modulus, fracture toughness, fracture surface energy and work of fracture were measured and evaluated. Microstructural variations and fracture surfaces have been examined and the formation of new phases has been identified depending on the additive type and quantity. The relationships between mechanical properties and structural variations for different compositions have been examined. In MgO-spinel materials, strength, Young's modulus and fracture toughness values decrease up to 20% spinel addition and stay almost constant for further loads. ZrO2 addition displays same trend but not as effective as spinel. Besides, since ZrO2 is stable in cubic form, it does not show any toughening mechanism. Forsterite formation is the most important factor for 2-fold improvement in the mechanical properties of MgO-spinel-zircon refractories. The more the zircon addition, the more the mechanical properties improve. The generation of natural bonding between matrix particles with forsterite formation, on the other hand, causes the fracture path to turn to transgranular fracture with an increase in fracture surface energy and a decrease in work of fracture, among which the latter is considered as an indicator of thermal shock resistance of the materials being high. 相似文献
12.
Huan-ping Wang Shi-qing Xu Shui-qin Lu shi-long Zhao Bao-ling Wang 《Ceramics International》2009,35(7):2715-2718
The effects of B2O3 additives on the sintering behavior, microstructure and dielectric properties of CaSiO3 ceramics have been investigated. The B2O3 addition resulted in the emergence of CaO–B2O3–SiO2 glass phase, which was advantageous to lower the synthesis temperature of CaSiO3 crystal phase, and could effectively lower the densification temperature of CaSiO3 ceramic to as low as 1100 °C. The 6 wt% B2O3-doped CaSiO3 ceramic sintered at 1100 °C possessed good dielectric properties: r = 6.84 and tan δ = 6.9 × 10−4 (1 MHz). 相似文献
13.
Preparation and microwave dielectric properties of 3ZnO·B2O3 ceramics with low sintering temperature
Yunxiang HuDongmei Wei Qiuyun Fu Jun ZhaoDongxiang Zhou 《Journal of the European Ceramic Society》2012,32(3):521-524
The preparation and dielectric properties of 3ZnO·B2O3 ceramics were investigated. Dense 3ZnO·B2O3 ceramics were obtained as sintered in the temperature range from 950 to 1000 °C for 3 h. The X-ray diffraction showed that the obtained ceramics were of a monoclinic 3ZnO·B2O3 structure. The ceramic specimens fired at 955 °C for 1 h exhibited excellent microwave dielectric properties: ?r ∼ 6.9, Q × f ∼ 20,647 GHz (@6.35 GHz), and τf ∼ −80 ppm/°C. The dependences of relative density, ?r, and Q × f of ceramics sintered at 955 °C on sintering soaking time showed that they all reached their plateaus as the soaking time was up to 60 min. Meanwhile, 3ZnO·B2O3 ceramics had no reaction with silver during cofiring, indicating it is a potential candidate for low-temperature cofired ceramic (LTCC) substrate. 相似文献
14.
Hao-Tung LinPramoda K. Nayak Bo-Zon LiuWei-Hsio Chen Jow-Lay Huang 《Journal of the European Ceramic Society》2012,32(1):77-83
The fine grains of Al2O3-Cr2O3/Cr-carbide nanocomposites were prepared by employing recently developed spark plasma sintering (SPS) technique. The initial materials were fabricated by a metal organic chemical vapor deposition (MOCVD) process, in which Cr(CO)6 was used as a precursor and Al2O3 powders as matrix in a spouted chamber. The basic mechanical properties like hardness, fracture strength and toughness, and the nanoindentation characterization of nanocomposites such as Elastics modulus (E), elastic work (We) and plastic work (Wp) were analyzed. The microstructure of dislocation, transgranular and step-wise fracture surface were observed in the nanocomposites. The nanocomposites show fracture toughness of (4.8 MPa m1/2) and facture strength (780 MPa), which is higher than monolithic alumina. The strengthening mechanism from the secondary phase and solid solution are also discussed in the present work. Nanoindentation characterization further illustrates the strengthening of nanocomposites. 相似文献
15.
Ipek AkinElif Yilmaz Filiz SahinOnuralp Yucel Gultekin Goller 《Ceramics International》2011,37(8):3273-3280
Alumina (Al2O3) and alumina-yttria stabilized zirconia (YSZ) composites containing 3 and 5 mass% ceria (CeO2) were prepared by spark plasma sintering (SPS) at temperatures of 1350-1400 °C for 300 s under a pressure of 40 MPa. Densification, microstructure and mechanical properties of the Al2O3 based composites were investigated. Fully dense composites with a relative density of approximately 99% were obtained. The grain growth of alumina was inhibited significantly by the addition of 10 vol% zirconia, and formation of elongated CeAl11O18 grains was observed in the ceria containing composites sintered at 1400 °C. Al2O3-YSZ composites without CeO2 had higher hardness than monolithic Al2O3 sintered body and the hardness of Al2O3-YSZ composites decreased from 20.3 GPa to 18.5 GPa when the content of ZrO2 increased from 10 to 30 vol%. The fracture toughness of Al2O3 increased from 2.8 MPa m1/2 to 5.6 MPa m1/2 with the addition of 10 vol% YSZ, and further addition resulted in higher fracture toughness values. The highest value of fracture toughness, 6.2 MPa m1/2, was achieved with the addition of 30 vol% YSZ. 相似文献
16.
BaTiO3/xCu composite ceramics with x = 0-30 wt.% were fabricated by the traditional mixing method in nitrogen gas. The mechanical properties and electric properties of the obtained composites were investigated as a function of the Cu mass fraction using a three bending test and impedance spectroscopy. The results indicated that the relative density of the sintered composites reached above 91%, the Cu-dispersed BaTiO3 composites enhanced the mechanical properties, particularly the high fracture toughness (∼3.9 MPa m1/2) and bending strength (∼134 MPa), compared to the monolithic BaTiO3. Furthermore, the percolation threshold of BaTiO3/Cu composites was x = 25 wt.%. The permittivity (?r) markedly increased from ∼2000 for monolithic BaTiO3 to ∼9000 with increasing Cu up to 30 wt.%. Additionally, the temperature coefficient of this system was less than 5% in the temperature range of 25-115. 相似文献
17.
TiO2 based ceramic/glass composites were prepared by a non-reactive liquid phase sintering (NLPS) using zinc borosilicate (ZBS) glass having the deformation temperature of 588 °C. The compounds of Zn2SiO4 and Zn4B6O13 were formed after the sintering process, indicating that the ZBS glass was a non-reactive one in this system. For TiO2/50 vol% ZBS glass composite, the two-stage sintering behavior was conducted as the sintering temperature increased. The former might be correlated to the NLPS process and the latter appeared to be related to the crystallization. The dielectric constant (?r) was mainly affected by the porosity and obeyed the logarithmic mixing rule. The quality factor (Q × f0) showed an increase and then a steep decrease after the maximum at 850 °C. TiO2/50 vol% ZBS glass composite sintered at 900 °C demonstrated 36 in the dielectric constant (?r) and 7500 GHz in the quality factor (Q × f0) for an application to LTCC filters. 相似文献
18.
The current study reports on the improvement of mechanical properties of 3?mol% Y2O3 stabilized tetragonal ZrO2 (3Y-TZP) by introduction of tourmaline through ball milling and subsequent densification by pressureless sintering at 800, 1200, 1300, 1400?°C. Findings demonstrate that no matter which sintering temperature the 3Y-TZP ceramic containing 2?wt% tourmaline reach a maximum value in flexural strength and fracture toughness as compared to other composite ceramics. As the tourmaline content is 2?wt% and the sintering temperature is 1300?°C, the flexural strength and fracture toughness of the composite ceramics are the highest, increases of 36.2% and 36.6% over plain 3Y-TZP ceramic respectively. The unique microstructure was systematically investigated through X-ray diffraction, scanning electron microscopy, energy dispersive spectrum, and flourier transform-infrared. The strengthening and toughening mechanism of tourmaline in 3Y-TZP ceramic were also discussed. 相似文献
19.
《Ceramics International》2017,43(3):3448-3452
Ti/Al2O3 composites with different volume percentages of Pr6O11 added (0–12.0 vol.%) were prepared by pressureless sintering at 1600 °C for 1.5 h. The influences of Pr6O11 on the composition, microstructure and mechanical properties of the composites were characterized and investigated. The results showed that Pr6O11 could promote the sintering of the composites by generating some new interfacial reaction products, such as AlTiO2, Pr2Ti2O7 and PrAlO3. Pr6O11 could also inhibit the production of TiAl and Ti3Al by the same mechanism. Additionally, Pr6O11 changed hexagonal alumina to tetragonal alumina. The latter could improve the mechanical properties of the composites by the effects of crack deflection and particle pullout when it was present in proper amounts. Composites showed satisfactory comprehensive properties when the content of Pr6O11 was no more than 3.0 vol.%. 相似文献
20.
TiC and Mo were introduced into B4C-based ceramic nozzles, which were obtained by hot-press sintering. The effect of TiC content on mechanical properties and erosion behavior of B4C-based ceramic nozzles were analyzed. XRD analysis showed that chemical reactions took place during the sintering process, which resulted in B4C/Mo/TiB2 ceramic nozzle with high density and improved mechanical properties compared with B4C/Mo ceramic nozzle. The sintering temperature was decreased from 2150 °C for B4C/Mo ceramic nozzle to 1950 °C for B4C/Mo/TiB2 ceramic nozzle. Results of erosion wear tests indicated that the hardness and toughness were the key factors influencing the erosion rate of B4C/Mo/TiB2 ceramic nozzle. Analysis of the eroded bore surfaces of B4C/Mo/TiB2 ceramic nozzle showed that the entry bore section exhibited a brittle fracture induced material removal process, and the center bore section showed plowing and polishing of material removal. Fracture and plowing of material removal occurred at the exit bore section. 相似文献