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1.
The mechanical properties and amorphization response of a carbon nanotube (5 wt.%) boron carbide (CNT-B4C) composite with 1 μm grain size are investigated, and compared to those of coarse-grained (10 μm grain size) and ultrafine-grained (0.3 μm grain size) monolithic boron carbides. The quasi-static and dynamic uniaxial compressive strengths for CNT-B4C were statistically the same as those of the ultrafine-grained ceramic and higher than the coarse-grained material, contradicting the expected grain size hierarchy (Hall-Petch-type relationship). Addition of CNTs to B4C resulted in decreased quasi-static hardness compared to the large grain size material; however, dynamic hardness was substantially improved compared to quasi-static values. CNT pullout and crack bridging were observed to be possible toughening mechanisms. Finally, Raman spectroscopy was used to quantify amorphization, and it was concluded that addition of CNTs to boron carbide does not alter the propensity for amorphization, but does improve mechanical properties by enhanced toughening. 相似文献
2.
Oleg Vasylkiv 《Journal of the American Ceramic Society》2016,99(7):2436-2441
The in situ synthesis/consolidation of B4C–TaB2 eutectic composites by spark plasma sintering (SPS) is reported. Samples for the evaluation of bending strength were cut from specimens with diameters of 30 mm. The sample prepared for the three‐point flexural strength test had fibers of tantalum diboride with diameter of 1.3 ± 0.4 μm distributed in the B4C matrix, thereby reducing composites brittleness and yielding an indentation fracture toughness of up to 4.5 MPa·m1/2. Furthermore, the Vickers hardness of B4C–TaB2 eutectics formed by SPS was as high as 26 GPa at an indentation load of 9.8 N. The flexural strength of the B4C–TaB2 system has been reported for the first time. Some steps were identified in the load–displacement curve, suggesting that micro‐ and macrocracking occurred during the flexural test. Ceramic composites with a eutectic structure exhibited a room‐temperature strength of 430 ± 25 MPa. Compared with other eutectic composites of boron carbide with transition‐metal diborides, room‐temperature strength the B4C–TaB2 was 40% higher than that of B4C–TiB2 ceramics, demonstrating advantage of the in situ synthesis/consolidation of eutectic composites by SPS. 相似文献
3.
Titanium diboride–silicon carbide–boron carbide ceramics with super‐high hardness and strength
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Eric W. Neuman Harlan J. Brown‐Shaklee Gregory E. Hilmas William G. Fahrenholtz 《Journal of the American Ceramic Society》2018,101(2):497-501
Triplex particulate composites composed of boride and carbide ceramics were found to have high strength, hardness, and fracture toughness values. Two compositions consisting of 70:15:15 and 1:1:1 volume ratios of TiB2, SiC, and B4C were produced from commercially available powders by hot‐pressing. The 70:15:15 ceramic exhibited a strength of ~1.3 GPa, while the 1:1:1 ceramic had a strength of ~0.9 GPa. These strengths are comparable to super‐strong Y2O3‐PSZ and β‐SiAlON based composites. The Vickers’ hardness values of these ceramics were ~32 GPa for indent loads of 9.8 N. Hardness increased as indentation load decreased. The 1:1:1 ceramic had a hardness of ~53 GPa at an indentation load of 0.49 N, higher than values reported for so‐called “super‐hard” ceramics, and comparable to c‐BN. 相似文献
4.
Gregory Parsard Ghatu Subhash Phillip Jannotti 《Journal of the American Ceramic Society》2018,101(6):2606-2615
The residual pressure surrounding quasistatic and dynamic Vickers indentations in boron carbide was quantitatively mapped in 3 dimensions using Raman spectroscopy. These maps were compared against similar maps of amorphization intensity and optical micrographs of deformed regions to determine the roles of amorphization and damage upon indentation‐induced residual stress. Stress relaxation was observed near radial cracks, spalled regions, and graphitic inclusions. A positive correlation was found between high levels of residual stress and the number of amorphized sites detected. Finite element simulations were conducted to model the indentation‐induced residual stress fields in the absence of amorphization and cracking. The simulations underpredicted the average residual pressure observed through Raman spectroscopy, implying that amorphization contributes to increased pressure in the material. This pressure is interpreted as potential evidence of volumetric expansion of the amorphized material which is less ordered and hence exerts compressive forces on the surrounding crystalline matrix. 相似文献
5.
Matan Cafri Alon Malka Helen Dilman Moshe P. Dariel Nahum Frage 《International Journal of Applied Ceramic Technology》2014,11(2):273-279
Reaction‐bonded boron carbide was manufactured by infiltrating porous boron carbide preforms at 1273 K with a Mg‐Si eutectic alloy. The resulting composite material consists, in addition to the original B4C, of SiC, Mg2Si, and a Mg‐rich complex boride/carbide Mgx(Al,Si)y(B,C)z phase. The composites display high hardness (1700 HV), Young's modulus (356 MPa) and a moderate bending strength (230 MPa). The ballistic efficiency (of about 6.7), as determined by the depth of penetration method, is much higher than that of alumina and similar to that of silicon‐infiltrated reaction‐bonded composites. 相似文献
6.
Zeynep Ayguzer Yasar Matthew M. Koelle Richard A. Haber 《International Journal of Applied Ceramic Technology》2024,21(3):2263-2272
Boron carbide is a notable ceramic, with its high hardness and low density. However, it suffers a sudden loss in strength under high shear stress. Doping boron carbide with Si/B is widely used to increase its resistance to amorphization. High purity boron and silicon hexaboride precursor powders are used for doping boron carbide, but these materials have high costs and supply chain constraints. This research investigated the effect of substituting lower purity B or using pure Si powder instead of SiB6 on materials’ properties such as elastic and mechanical properties, microstructure, and amorphization resistances. It was observed that using lower-purity boron or pure Si powder instead of SiB6 did not significantly affect critical properties, such as fracture toughness, hardness, or amorphization resistance. However, Young's modulus values decreased as B purity decreased and as Si was used instead of SiB6. These findings demonstrate that substituting precursor materials in Si/B co-doped B4C is possible with little change in the material's properties. This facilitates the use of easier-to-access, cheaper production routes to be used for silicon-doped boron carbide products. 相似文献
7.
《Journal of the European Ceramic Society》2020,40(3):612-621
A self-assembly polymerization process was used to prepare graphene oxide/boron carbide (GO/B4C) composite powders, spark plasma sintering (SPS) was used to fabricate reduced graphene oxide/boron carbide (rGO/B4C) composites at 1800 °C and 30 MPa with a soaking time of 5 min. The effects of rGO addition on mechanical properties of the composites, such as Vickers hardness, flexural strength and fracture toughness, were investigated. The results showed that GO/B4C composite powders were successfully self-assembled and a network structure was formed at high GO contents. The flexural strength and fracture toughness of rGO/B4C composites were 643.64 MPa and 5.56 MPa m1/2, respectively, at 1 and 2.5 wt.% rGO content, corresponding to an increase of 99.11% and 71.6% when compared to B4C ceramics. Uniformly dispersed rGO in rGO/B4C composites played an important role in improving their strength and toughness. The toughening mechanisms of rGO/B4C composites were explained by graphene pull-out, crack deflection and bridging. 相似文献
8.
Xiaorong Zhang Zhixiao Zhang Bin Nie Huanyu Chen Yanming Wang Liyun Zheng Yongmei Bai Weimin Wang 《Ceramics International》2018,44(9):10766-10772
Dense and fine-grained boron carbide (B4C) ceramics were fabricated via high-pressure hot pressing (100?MPa) using powders, which are prepared by high-energy ball milling. These powders were sintered at a low temperature (1800?°C) without any sintering aid. The dense and fine-grained B4C ceramics demonstrate super high hardness, outstanding fracture toughness and modern flexure strength. The milled powders were characterised by disordered crystal structure and ultrafine particle size that ranges from a few nanometres to a few hundred nanometres. The combined contributions of high pressure and the characteristic of the milled powders guaranteed that the dense fine-grained microstructure was achieved at only 1800?°C. The grain size distribution of the ceramics was inhomogeneous and ranged from 70?nm to 1.6?µm. However, the average grain size was fine at only 430?nm, which partially contributed to the super high hardness of the B4C ceramics. The locally concentrated areas of the small grains changed the fracture mode of the B4C ceramics from the complete transgranular fracture to a mixture of transgranular and intergranular fractures, thereby enhancing the toughness of the B4C ceramics. The relative density, Vickers hardness, flexure strength and fracture toughness of the obtained B4C ceramics reached up to 99.5%, 41.3?GPa, 564?MPa and 4.41?MPa?m1/2, respectively. 相似文献
9.
Mustafa Karaman N. Aslı Sezgi H. Önder Özbelge 《American Institute of Chemical Engineers》2009,55(11):2914-2919
β‐rhombohedral boron carbide (B4C) was deposited on a tungsten substrate from a BCl3? H2? CH4 gas mixture in a dual impinging‐jet chemical vapor deposition reactor. On‐line FTIR analysis of the product stream proved the formation of BHCl2 and HCl as by products, in a competing parallel reaction. A maximum of 13% chemical yield of boron carbide was observed, and the yield was found to have increasing trend with an increase in temperature. XRD analysis proved the existence of rhombohedral B4C phase at 1300°C without any other B4C phases or impurities. At this temperature, the formation of 5‐fold icosahedral boron carbide crystals up to 30 micron sizes was observed. Such highly symmetric crystalline regions were observed to have a very high hardness value of 4750 kg/mm2 as revealed from the microhardness analysis. The change in product morphology at low substrate temperatures resulted in a decrease in the hardness values. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
10.
Xiaoguang Li Dongliang Jiang Jingxian Zhang Yunzhou Zhu Zhongming Chen Zhengren Huang 《International Journal of Applied Ceramic Technology》2016,13(3):584-592
Reaction‐bonded B4C (RBBC) was fabricated through molten Si infiltrating porous B4C preforms. A preform with a 75% relative green density was obtained by mixing two different sized B4C powders. Carbon black added to the preform slightly reduces average pore size, but increases porosity. RBBC ceramics showed a dense and homogeneous microstructure. Vickers hardness was about 15 GPa for RBBC fabricated from a single type of B4C powder and could reach 22–23 GPa for the carbon‐added samples after infiltration. Morphological evolution and the influence of the microstructure on the Vickers hardness were investigated and discussed. 相似文献
11.
《Journal of the European Ceramic Society》2022,42(15):6795-6801
Three phase boride and carbide ceramics were found to have remarkably high hardness values. Six different compositions were produced by hot pressing ternary mixtures of Group IVB transition metal diborides, SiC, and B4C. Vickers’ hardness at 9.8 N was ~31 GPa for a ceramic containing 70 vol% TiB2, 15 vol% SiC, and 15 vol% B4C, increasing to ~33 GPa for a ceramic containing equal volume fractions of the three constituents. Hardness values for the ceramics containing ZrB2 and HfB2 were ~30% and 20% lower than the corresponding TiB2 containing ceramics, respectively. Hardness values also increased as indentation load decreased due to the indentation size effect. At an indentation load of 0.49 N, the hardness of the previously reported ceramic containing equal volume fractions of TiB2, SiC and B4C was ~54 GPa, the highest of the ceramics in the present study and higher than the hardness values reported for so-called “superhard” ceramics at comparable indentation loads. The previously reported ceramic containing 70 vol% TiB2, 15 vol% SiC, and 15 vol% B4C also displayed the highest flexural strength of ~1.3 GPa and fracture toughness of 5.7 MPa·m1/2, decreasing to ~0.9 GPa and 4.5 MPa·m1/2 for a ceramic containing equal volume fractions of the constituents. 相似文献
12.
Effect of graphite content on properties of B4C‐W2B5 ceramic composites by in situ reaction of B‐Gr‐WC
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Deng Pan Shufeng Li Xin Zhang Bo Pan Shengyin Zhou Yabo Fu Katsuyoshi Kondoh 《Journal of the American Ceramic Society》2018,101(8):3617-3626
Strip‐shaped W2B5 reinforced B4C ceramic composites were prepared via in situ reaction of boron(B)‐graphite(Gr)‐WC system by powder metallurgy (P/M). In order to study the effect of the graphite content on the properties of the as‐fabricated ceramic composites, the powder mixture of B‐Gr‐WC with various amounts of Gr powder were blended and consolidated by spark plasma sintering (SPS). The sintering parameters were shown as following: sintering pressure was set as 30 MPa; The three‐step sintering temperature was 1100‐1550‐1700°C and the duration time was set as 5‐5‐6 minutes, respectively. In situ formed strip‐shaped W2B5 particles were dispersed homogeneously in B4C matrix, which resulted in a remarkable improvement on the fracture toughness and mechanical properties. Appropriate 5vol% residual Gr in the composite shows positive effect on the mechanical properties which achieved an optimal counter‐balance of fracture toughness and hardness, the relative density was 99.8%, the Vickers hardness can reach 30.2 GPa, and the fracture toughness was 11.9 MPa·m1/2 when the sintering temperature was set at 1700°C. 相似文献
13.
《Journal of the European Ceramic Society》2023,43(4):1295-1302
Square-shaped monolithic B4C and B4C-ZrB2 composites were produced by spark plasma sintering (SPS) method to investigate the effect of 5, 10, 15 vol% ZrB2 addition on the densification, mechanical and microstructural properties of boron carbide. The relative density of B4C increased with the increasing volume fraction of ZrB2 and density differences in different regions of the sample narrowed down. Homogeneous density distribution and microstructure were accomplished with the increasing holding time from 7 to 20 min for the B4C-15 vol% ZrB2 composites, and the highest overall relative density was achieved as 99.23%. The hardness and fracture toughness of composites were enhanced with the addition of ZrB2 compared to monolithic B4C. The enhancement in fracture toughness was observed due to the crack deflection, crack bridging and crack branching mechanisms. The B4C-15 vol% ZrB2 composite exhibited the combination of superior properties (hardness of 33.08 GPa, Vickers indentation fracture toughness of 3.82 MPa.m1/2). 相似文献
14.
Ji Zou Shui‐Gen Huang Kim Vanmeensel Guo‐Jun Zhang Jef Vleugels Omer Van der Biest 《Journal of the American Ceramic Society》2013,96(4):1055-1059
A carbide boronizing method was first developed to produce dense boron carbide‐ zirconium diboride (“B4C”–ZrB2) composites from zirconium carbide (ZrC) and amorphous boron powders (B) by Spark Plasma Sintering at 1800°C–2000°C. The stoichiometry of “B4C” could be tailored by changing initial boron content, which also has an influence on the processing. The self‐propagating high‐temperature synthesis could be ignited by 1 mol ZrC and 6 mol B at around 1240°C, whereas it was suppressed at a level of 10 mol B. B8C–ZrB2 ceramics sintered at 1800°C with 1 mole ZrC and 10 mole B exhibited super high hardness (40.36 GPa at 2.94 N and 33.4 GPa at 9.8 N). The primary reason for the unusual high hardness of B8C–ZrB2 ceramics was considered to be the formation of nano‐sized ZrB2 grains. 相似文献
15.
Kelvin Y. Xie Muhammet F. Toksoy Kanak Kuwelkar Binwei Zhang Jessica A. Krogstad Richard A. Haber Kevin J. Hemker 《Journal of the American Ceramic Society》2014,97(11):3710-3718
Uniform densification of relatively thick (~7 mm) consolidated boron carbide plates at relatively low temperatures (e.g. 1800°C) and low facture toughness are two of the primary challenges for further development of boron carbide applications. This work reports that these two challenges can be overcome simultaneously by adding 5 wt% alumina as a sintering aid. Nearly fully dense (97%), fine grained boron carbide (B4C) samples were produced using spark plasma sintering at 1700°C and above in the B4C‐5 wt% Al2O3 system. The alumina and boron carbide matrix reacted to form an Al5O6BO3 (a mullite‐like phase) during sintering. The Al5O6BO3 phase facilitated uniform densification via liquid phase sintering. This secondary phase is dispersed throughout the intergranular pores, providing obstacles for crack propagation and resulting in tougher boron carbide ceramics. 相似文献
16.
Junfeng Gu Mingyu Xiang Wei Ji Weimin Wang Hao Wang Zhengyi Fu 《Journal of the American Ceramic Society》2018,101(12):5400-5410
The usual way to prepare TaC‐TaB2 ceramics by adding B4C to TaC leads to formation of residual C, which degrades samples’ mechanical properties. To eliminate the residual C, we suggest incorporating Si together with B4C into TaC ceramics, resulting in new ultrahigh‐temperature ceramics (TaC‐TaB2‐SiC). Dense ceramics (>99%) with SiC volume fraction ranging from 15.86% to 41.04% were fabricated by reactive spark plasma sintering at 1900°C for 5 minutes. The formation of SiO2‐based transient liquid phase was evidenced by the “film” in intermediate products, which can promote densification. The fine‐grained microstructure in final products was found to be associated with the in situ formed SiC, which impeded TaC and TaB2 grains from coarsening by the pinning effect. Besides, ultrafine TaB2 grains (~100 nm) produced during the reaction and then rearranged in liquid also contributed to grain refinement. Compared to TaC‐TaB2(‐C) ceramics prepared from TaC and B4C, the acquired composites exhibit better mechanical properties, due to their fine‐grained microstructures and the elimination of residual C. 相似文献
17.
Synthesis of Boron Carbide by Reactive‐Pulsed Electric Current Sintering in the Presence of Tungsten Boride
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Dimitar Radev Ivalina Avramova Daniela Kovacheva Devendraprakash Gautam Ivan Radev 《International Journal of Applied Ceramic Technology》2016,13(6):997-1007
The method of pulsed electric current sintering (PECS) has been used to obtain dense boron carbide (B4C) and B4C‐based composite materials containing tungsten boride (W2B5). To elucidate the role of the sintering additives and the mechanism of reactive densification, three types of materials have been obtained by PECS at 1850°C and 1900°C: “pure” B4C, B4C doped with 10 wt% W2B5, and B4C doped with 10 wt% tungsten carbide (WC). X‐ray diffraction and X‐ray photoelectron spectroscopy have been used to determine crystallite size, phase changes, and the peculiarities of the chemical bonds of the densified materials. Structural and mechanical properties of the materials have been investigated using scanning electron microscopy, optical microscopy, ultrasound velocity measurements, and hardness tests. The electrochemical impedance spectra have been used to investigate the electrical properties of the PECS‐ed materials. 相似文献
18.
ABSTRACTThe results of the study of the production technology, phase composition, structure and physico-mechanical properties of metal-ceramic materials based on boron carbide and their components are presented. Boron carbide was obtained by direct synthesis from chemical elements using amorphous boron and carbon black. By mechanical dispersion, solid reagents were converted into an ultrafine state. Using a chemical method, nanoscale (70–80?nm) boron carbide was synthesised from suspension solutions of amorphous boron and liquid hydrocarbons. Boron carbide-based metal-ceramic composite powder B4C–(Co–Ni–Ti) was obtained by mechanical dispersion of the constituent components. Based on results of studying of the temperature-dependence of wetting angle of boron carbide with Co–Ni–Ti metallic alloy, the compacting modes of metal-ceramic composite powders by plasma-spark sintering and hot pressing have been developed. The influence of the component content of the binder metal (alloy) on some physico-mechanical properties (linear expansion coefficient, hardness, and bending strength) of hardmetal-ceramic materials based on boron carbide was studied. It was found that the optimum content of the metal component in the composite is ~ 25?wt-%. In the temperature range 300–600°C, the materials obtained are characterised by stable dimensional factors, since in this temperature range the thermal conductivity coefficient does not depend much on temperature. At room temperature, their bending strength is about 1?GPa. A new method of chemical synthesis of nanocrystalline ceramic compositions of boron carbide and titanium diboride using suspension solutions for the preparation of powders and their spark plasma sintering was also developed to obtain a compacted material of composition B4C+30?wt-%TiB2, which has a high hardness of 95 HRA (with maximum microhardness 45.6?GPa) and sufficient strength (with a bending strength of 834?MPa). 相似文献
19.
《Ceramics International》2017,43(5):4062-4067
The resorcinol-formaldehyde (RF) gel-casting system is employed for the first time to fabricate a hierarchical porous B4C/C preform, which was subsequently used for the fabrication of reaction bonded boron carbide (RBBC) composites via a liquid silicon infiltration process. The effect of the carbon content and carbon structures of this perform on the microstructures and mechanical properties of B4C/C preform and the resultant RBBC composites is reported. The B4C/C preform (16 wt% carbon) exhibit a strength of 34±1 MPa. The obtained RBBC composites shown uniform microstructure is consisted of SiC particles bonded boron carbide scaffold and an interpenetrating residual silicon phase. The Vickers hardness, flexural strength and fracture toughness of the RBBC composites (16 wt% carbon) are 24 GPa, 452 MPa and 4.32 MPa m1/2, respectively. 相似文献
20.
High‐Temperature Strength of Boron Suboxide Ceramic Consolidated by Spark Plasma Sintering
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The spark plasma sintering (SPS) of B6O ceramics using a highly crystalline boron suboxide powder with a low oxygen deficiency level is reported. The monolithic boron suboxide ceramic exhibited a room‐temperature strength of 300 ± 20 MPa, which is comparable to the strength of monolithic boron carbide. With increasing flexural test temperature, the strength of the boron suboxide ceramics increased to 450 MPa at 1400°C. The increase in strength with the temperature is associated with the unique microstructure of boron suboxide grains, which allows intergranular “brittle” fracture along subgrains even at 1400°C. This suggests that even higher strengths can be achieved. 相似文献