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1.
Mei Zhang Xiao Feng Tiechui Yuan Ruidi Li 《International Journal of Applied Ceramic Technology》2019,16(1):389-399
The high sintering temperature of pure B4C considerably limits its widespread application, thus searching an effective sintering aid is critical. In this work, B4C-based ceramic with 1 vol.% nonequiatomic Fe50Mn30Co10Cr10 medium entropy alloy as a sintering aid were fabricated at 1900-2000°C by spark plasma sintering (SPS) under applied pressure, and their mechanical properties were examined and compared with pure B4C ceramic sintered at same condition. The maximal flexural strength of 255.59 MPa, microhardness of 2297.6 Hv0.2 and fracture toughness of 3.62 MPa m1/2 could be obtained at optimized SPS pressure of 50 MPa, which were all higher than those of pure B4C ceramic. To better understand the densification kinetics mechanisms, the densification ratio as a function of SPS temperature and pressure was theoretically analyzed using steady creep model. It was found that densification controlled by grain-boundary sliding at lower pressure transferred to power law creep regime at higher pressure, which were proved by the dislocation net shown in transmission electron microscopy image. 相似文献
2.
Weiping Xuan Yuchun Ji Bingsai Liu Shaofei Li Wenzhuo Chen Zhengdei Li Jilin Wang Guoyuan Zheng Fei Long 《International Journal of Applied Ceramic Technology》2023,20(3):1457-1469
In this paper, the novel boron nitride micron tubes (BNMTs) were used to reinforce commercial boron carbide (B4C) ceramics prepared via spark plasma sintering technology. The effects of the sintering parameters, sintering temperature, the holding time, and the BNMTs content on the microstructure and mechanical properties of B4C/BNMTs composite ceramics were studied. The results indicated that adding a proper amount of BNMTs could inhibit the grain growth of B4C and improve the fracture toughness of the B4C/BNMTs composite ceramics. The prepared composite ceramic sample with 5 wt% BNMTs at 1850°C, 8 min and 30 MPa displayed the best mechanical properties. The relative density, hardness, fracture toughness, and bending strength of the samples were 99.7% ± .1%, 35.62 ± .43 GPa, 6.23 ± .2 MPa m1/2, and 517 ± 7.8 MPa, respectively. Therein, the corresponding value of hardness, fracture toughness, and bending strength was increased by 10.3%, 43.59%, and 61.5%, respectively, than that of the B4C/BNMTs composite ceramic without BNMTs. It was proved that the high interface binding energy and bridging effect between boron carbide and BNMTs were the toughening principle of BNMTs. 相似文献
3.
Xiaoguang Li Dongliang Jiang Jingxian Zhang Qingling Lin Zhongming Chen Zhengren Huang 《Ceramics International》2014
In this work, boron carbide ceramics were sintered in the temperature range of 1400–1600 °C by spark plasma sintering (SPS). The influence of sintering temperature, heating rate, and holding time on the microstructure, densification process and physical property was studied. The heating rate was found to have greater influence than that of the holding time on the microstructure and the densification of boron carbide. The optimal sintering temperature was 1600 °C under the heating rate higher than 100 °C/min. The relative density, flexural strength, Vickers hardness and fracture toughness of the sample synthesized at 1600 °C were 98.33%, 828 MPa, 31 GPa and 2.66±0.29 MPa m1/2, respectively. The densification mechanism was also investigated. 相似文献
4.
Mei Zhang Tiechui Yuan Ruidi Li Siyao Xie Minbo Wang Qigang Weng 《Ceramics International》2018,44(4):3571-3579
Micron-sized boron carbide (B4C) powders were subjected to spark plasma sintering (SPS) under temperature ranging from 1700 °C to 2100 °C for a soaking time of 5, 10 and 20 min and their densification kinetics was determined using a creep deformation model. The densification mechanism was interpreted on the basis of the stress exponent n and the apparent activation energy Qd from Harrenius plots. Results showed that within the temperature range 1700–2000 °C, creep deformation which was controlled by grain-boundary sliding or by interface reaction contributed to the densification mechanism at low effective stress regime (n = 2,Qd = 459.36 kJ/mol). While at temperature higher than 2000 °C or at high stress regime, the dominant mechanism appears to be the dislocation climb (n = 6.11). 相似文献
5.
Yi Zeng Huilin Lun Xiang Xiong Ziming Ye Tianxiao Qian Wei Sun Yalei Wang Zhaoke Chen 《Journal of the American Ceramic Society》2020,103(1):23-27
Multicomponent boron-containing carbide (ie, Zr-Ti-C-B) composites show good ablation resistance. The present work is the first report to introduce the powder fabrication of Zr-Ti-C-B using a new method for solid-state diffusion of boron atoms. First, the nonstoichiometric carbide (ie, Zr0.8Ti0.2C0.8) with carbon vacancies was fabricated by free-pressureless spark plasma sintering. Different boron sources such as B2O3, B, and B4C were used to react with the nonstoichiometric carbide. The Zr0.81Ti0.19C0.86B0.14 can be finally generated through the solid-state diffusion of boron atoms using the B2O3 boron source at 1300°C followed by carbon thermal reduction using the phenolic resins at 1600°C. 相似文献
6.
Harlan J. Brown-Shaklee Eric W. Neuman William G. Fahrenholtz Gregory E. Hilmas 《Journal of the American Ceramic Society》2023,106(3):1932-1944
Boron carbide powders were synthesized from elemental powders and studied using X-ray diffraction (XRD) and UV–visible diffuse reflectance, Raman, and diffuse reflectance IR spectroscopies. Following reaction at 1400°C for 6 h, synthesized powders exhibited possible faulting as suggested by XRD patterns. B3C, B4.3C, and B5C powders contained graphitic carbon whereas the boron carbides with higher B/C ratios contained no residual carbon, suggesting that the carbon rich phase boundary is likely temperature dependent. Analysis by Raman and IR spectroscopy suggested that Raman spectra are influenced by excitation frequency due to resonance. We suggest that measurement of boron carbides with resonant Raman lifts the selection rules to allow measurement of Raman silent modes that are present in the IR spectra. Optical reflectance of the boron carbide powders revealed that the B/C ratio governed the indirect and direct optical band gaps of the faulted powders. B3C and B4.3C powders were light gray in spite of the presence of the carbon, whereas B5C, B6.5C, B10C, and B12C were gray, green, brown, and dark brown, respectively. Increasing carbon content increased the optical indirect band gap from 1.3 eV for B12C to 3.2 eV for B3C, causing the observed color changes. 相似文献
7.
Influence of chemical composition on mechanical properties of spark plasma sintered boron carbide monoliths
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Florian Réjasse Mathias Georges Nicolas Pradeilles Guy Antou Alexandre Maître 《Journal of the American Ceramic Society》2018,101(9):3767-3772
Fully dense boron carbide monoliths exhibiting fine microstructure (i.e., submicrometric grain size) are sintered by Spark Plasma Sintering. Two different commercial powder batches, exhibiting different stoichiometries (i.e., B/C ratio and oxygen content) and various amounts of secondary phases (i.e., boric acid and free carbon), are used. Their chemical composition is well‐defined by coupling different methods (Transmission Electron Microscopy associated with XRD analyses, and Instrumental Gas Analysis), and are correlated with their mechanical properties, characterized from meso‐ to macro‐scopic scales by nano‐indentation and ultrasonic pulse echography. The presence of secondary phases (graphite and boric acid) is evidenced in various proportions in each powder batch. If the boric acid disappears during sintering, the graphite remains. However, for the considered amounts of graphite (lower than 1 wt%), the low variations in graphite content have no significant effect on hardness and elasticity values. At the opposite, the presence of oxygen in boron carbide lattice, leading to a boron oxycarbide phase, induces a decrease in both hardness and elasticity properties. 相似文献
8.
Arezoo Zare Mo-Rigen He Michael Straker M. V. S. Chandrashekhare Michael Spencer Kevin J. Hemker James W. McCauley K. T. Ramesh 《Journal of the American Ceramic Society》2022,105(5):3030-3042
Out-of-plane anisotropy in the mechanical response of boron carbide was studied by performing nanoindentation experiments on four specific crystallographic orientations of single crystals, that is, , , , and . For each orientation of the single crystals, in-plane variations of indentation modulus and hardness were also studied by monitoring the relative rotation between the crystal surface and a Berkovich indenter tip. A significant out-of-plane anisotropy in indentation modulus was observed with ~80 GPa difference between the highest and lowest values. A smaller but measurable out-of-plane anisotropy in indentation hardness was also observed. In-plane anisotropy, on the other hand, was found to be significantly influenced by the scatter in the data and geometrical imperfections of the indenter tip. Investigations of indentation pop-in events suggested that deformation is entirely elastic prior to the first pop-in. Furthermore, quasi-plastic flow along the orientation of the single crystals was found to be more homogeneous than the other tested orientations. For select indents, cross-sectional transmission electron microscopy (TEM) of the indented regions showed formation of a quasi-plastic zone in the form of lattice rotation and various microstructural defects. The quasi-plastic zone grew in size with increasing the indentation depth. The TEM observations also suggested the crystal slip to be a potential mechanism of quasi-plasticity and a precursor for formation of amorphous bands that could eventually lead to cracking and fragmentation. The proposed failure mechanism provides valuable insights for calibrating constitutive computational models of failure in boron carbide. 相似文献
9.
Hans-Peter Martin Bing Feng Alexander Michaelis 《International Journal of Applied Ceramic Technology》2020,17(2):407-412
Boron carbide and Tantalum boride composites were prepared by pressureless sintering of B4C with addition of TaC powder. The effect of TaC addition on the sinterability of boron carbide was studied. High densified ceramic with a relative density of 98.7% was obtained at sintering temperature of 2250°C. The composition and the microstructure of the dense composites are characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). The studies show that the composites contain boron carbide, TaB2, and carbon phases with a homogeneous structure. In addition, the correlation between the composition and the electrical conductivity was investigated. The electrical conductivity of the composite increased with increasing addition of TaC, and a change in conduction behavior from semiconducting to metallic was observed. High hardness value of 28.49 ± 1.33 GPa was obtained by the sample with 30 wt% TaC addition. 相似文献
10.
High thermal conductivity of spark plasma sintered silicon carbide ceramics with yttria and scandia
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Yu‐Kwang Seo Young‐Wook Kim Toshiyuki Nishimura Won‐Seon Seo 《Journal of the American Ceramic Society》2017,100(4):1290-1294
A fully dense SiC ceramic with a room‐temperature thermal conductivity of 262 W·(m·K)?1 was obtained via spark plasma sintering β‐SiC powder containing 0.79 vol% Y2O3‐Sc2O3. High‐resolution transmission electron microscopy revealed two different SiC‐SiC boundaries, that is, amorphous and clean boundaries, in addition to a fully crystallized junction phase. A high thermal conductivity was attributed to a low lattice oxygen content and the presence of clean SiC‐SiC boundaries. 相似文献
11.
《Journal of the European Ceramic Society》2022,42(2):383-391
Using spark plasma sintering (SPS), >98.5 % dense boron carbide (B4C) samples were made from commercially available and lab-synthesised powders made via a low temperature synthesis (LTS) process. The work showed that the LTS powder can be produced in batches of tens to hundreds of grams whilst maintaining a high purity material with lower levels of residual free carbon (20.6–21.3 wt.% C) than commercially available samples (22.4 wt.% C). The LTS material was seen to exhibit higher hardness values (37.8 GPa) than the commercial grade material (32.5 GPa) despite featuring a coarser average grain size (10.8 μm and 2.4 μm respectively). This is largely thought to be due to the influence of ZrO2 and AlB2 impurities introduced to the material during micronising milling of the powder after synthesis, as opposed to the influence of the materials lower carbon content. 相似文献
12.
《Ceramics International》2016,42(6):7001-7013
Dense (95–98.6%) bulk boron carbide prepared by Spark Plasma Sintering (SPS) in Ar or N2 atmospheres were subject to three-point flexural tests at room and at 1600 °C. Eight different consolidation conditions were used via SPS of commercially available B4C powder. Resulting specimens had similar grain size not exceeding 4 µm and room-temperature bending strength (σ25 °C) of 300–600 MPa, suggesting that difference in σ25 °C is due to development of secondary phases in monolithic boron carbide ceramics during SPS processing. To explain such difference the composition of boron carbide and secondary phases observed by XRD and Raman spectroscopy. The variation in intensity of the Raman peak at 490 cm−1 of boron carbide suggests modification of the boron carbide composition and a higher intensity correlates with a higher room-temperature bending strength (σ25 °C) and Vickers hardness (HV). Secondary phases can modify the level of mechanical characteristics within some general trends that are not dependent on additives (with some exceptions) or technologies. Namely, HV increases, σ25 °C decreases, and the ratio σ1600 °C/σ25 °C (σ1600 °C – bending strength at 1600 °C) is lower when fracture toughness (KIC) is higher. The ratio σ1600 °C/σ25 °C shows two regions of low and high KIC delimited by KIC=4.1 MPa m0.5: in the low KIC region, boron carbide specimens are produced in nitrogen. 相似文献
13.
《Journal of the European Ceramic Society》2021,41(15):7543-7551
SiC was densified by spark plasma sintering (SPS) and the effects of surface modification of the powder particles on its sintering behavior were investigated. The pressure and temperature conditions were set to 50 MPa and 2200 °C, respectively. Specific SPS experiments at a lower temperature (i.e. 1600 °C) was performed to analyze the efficiency of the sintering and the early stage of the densification in softer conditions. The surface functionalization was carried out by grafting a thin molecular layer of a preceramic precursor on the grain surface of SiC particles, which acts as a sintering additive without producing contamination by heteroatoms since, in addition to hydrogen, it contained only Si and C in the same ratio 1:1 as silicon carbide. One of the advantages of this surface functionalization is that it reduces the temperature at which the sintering process begins and therefore it facilitates and increases the densification of the final SiC parts. 相似文献
14.
《Journal of the European Ceramic Society》2022,42(3):860-868
To tackle the dissolution problem of boron carbide particles in silicon infiltration process, carbon-coated boron carbide particles were fabricated for the preparation of the reaction-bonded boron carbide composites. The carbon coating can effectively protect the boron carbide from reacting with liquid Si and their dissolution, thus maintaining the irregular shape of boron carbide particles and preventing the growth of boron carbide particles and reaction formed SiC regions. Furthermore, the nano-SiC particles, originated from the reaction of the carbon coating and the infiltrated Si, uniformly coated on the surfaces of boron carbide particles, thus forming a ceramic skeleton of the nano-SiC particles-coated and -bonded boron carbide particles. The Vickers hardness, flexural strength and fracture toughness of the composites can be increased by 26 %, 45 %, and 37 % respectively, by using carbon-coated boron carbide particles as raw materials. 相似文献
15.
Jian Zhao Linkun Shi Malin Liu Jiaxing Chang Youlin Shao Bing Liu Rongzheng Liu 《International Journal of Applied Ceramic Technology》2022,19(5):2514-2522
Dense sintering of SiC nanopowder under low temperature and pressure remains a big challenge, because of the great resistance caused by the severe agglomeration of nanopowder. A novel sintering strategy is proposed to prepare SiC composite ceramics by sintering the mixture of SiC nanopowder and SiC micron powder at low temperature and pressure. The SiC micron powder was in the size of 100 µm with little sintering activity, which was designed as a pressure conductor to promote the densification of SiC nanopowder. Experimental results showed that the SiC micron powder had a significant effect on increasing of the sintering density of nanopowder and improving the mechanical properties of SiC ceramics. An SiC composite ceramic with a relative density of 98%, a Vickers hardness of 22.6 GPa, and a fracture toughness of 5.43 MPa m1/2 could be sintered by spark plasma sintering under 1700°C and 30 MPa by adding 30 wt.% 100 µm SiC micron powder as reinforcements. 相似文献
16.
Jiawei Wu Bo Niu Fan Zhang Liwen Lei Jinyong Zhang Lin Ren Weimin Wang Zhengyi Fu 《Ceramics International》2018,44(13):15323-15330
A novel method, namely flash spark plasma sintering (FSPS), combining flash sintering and electric field assisted sintering, was utilized to densify boron carbide/titanium diboride (B4C/TiB2) composites. Further, sintering homogeneity of the composites with different contents of TiB2 was systematically investigated and theoretical model was built. Results indicated that addition of 50?wt% TiB2 led to the densification of B4C/TiB2 composite by up to 97.7% with regional range 1.9% at 1872?°C under pressure of 4?MPa in 60?s. The preferential pathway of TiB2 network proves to disperse the central current and distribute thermal flow throughout the specimen possibly via tunneling, electronic field emission effect at first stage and lower-resistance composite pathway latter, contributing to the increased homogeneity. 相似文献
17.
《Journal of the European Ceramic Society》2017,37(2):539-547
Titanium carbide ceramics with different contents of boron or B4C were pressureless sintered at temperatures from 2100 °C to 2300 °C. Due to the removal of oxide impurities, the onset temperature for TiC grain growth was lowered to 2100 °C and near fully dense (>98%) TiC ceramics were obtained at 2200 °C. TiB2 platelets and graphite flakes were formed during sintering process. They retard TiC grains from fast growth and reduced the entrapped pores in TiC grains. Therefore, TiC doped with boron or B4C could achieve higher relative density (>99.5%) than pure TiC (96.67%) at 2300 °C. Mechanical properties including Vickers’ hardness, fracture toughness and flexural strength were investigated. Highest fracture toughness (4.79 ± 0.50 MPa m1/2) and flexural strength (552.6 ± 23.1 MPa) have been obtained when TiC mixed with B4C by the mass ratio of 100:5.11. The main toughening mechanisms include crack deflection and pull-out of TiB2 platelets. 相似文献
18.
《Journal of the European Ceramic Society》2020,40(4):1103-1110
Hexagonal boron nitride (h-BN) can reinforce boron carbide (B4C) ceramics, but homogeneous dispersion of h-BN is difficult to achieve using conventional methods. Herein, B4C/h-BN composites were manufactured via the transformation of cubic (c-) BN during spark plasma sintering at 1800 °C. The effects of the c-BN content on the microstructure, densification, and mechanical properties of B4C/h-BN composites were evaluated. In situ synthesized h-BN platelets were homogeneously dispersed in the B4C matrix and the growth of B4C grains was effectively suppressed. Moreover, the c-BN to h-BN phase transformation improved the sinterability of B4C. The sample with 5 vol.% c-BN exhibited excellent integrated mechanical properties (hardness of 30.5 GPa, bending strength of 470 MPa, and fracture toughness of 3.84 MPa⋅ m1/2). Higher c-BN contents did not significantly affect the bending strength and fracture toughness but clearly decreased the hardness. The main toughening mechanisms were crack deflection, crack bridging, and pulling out of h-BN. 相似文献
19.
《Ceramics International》2020,46(7):9136-9144
Grain boundaries, twins, and defects are considered to influence the thermomechanical behavior of any covalent ceramic, as a result, monolithic B4C samples show different curve shapes of bending strength vs temperature and the present theoretical models fail to fit them over the entire temperature range. To overcome these issues, we fabricated a novel high-density boron carbide and evaluated its high-temperature bending strength. The as-obtained ceramic is composed of boron carbide grains and a fine grain-boundary metal Pt framework. The material shows a decreased strength, which is due to a non-linear increase in the volume expansion coefficient of the B4C. Recovery in strength above 1000 °C is due to the presence of twins, their growth and rearrangements. We consider twins rearrangements are the pieces of evidence for a novel ‘micro’ mechanism of high-temperature stress accommodation for the boron carbide bulks. 相似文献
20.
Timothy Holmquist Sidney Chocron Art Nicholls 《Journal of the American Ceramic Society》2021,104(5):2348-2357
This article presents new test data to assess the effect the third invariant has on the strength and failure of two ceramic materials: boron carbide and silicon carbide. Two experimental techniques are used: the Brazilian test that produces a biaxial state of stress, and a new technique that uses a high-pressure confinement vessel to load a specially designed dumbbell specimen in triaxial extension. The dumbbell geometry provides two important advantages over the typically used cylindrical specimen: no adhesive is required to bond the specimen to the load cell because the dumbbell geometry naturally takes the specimen into tension, and any loading asymmetries are essentially eliminated due to the axisymmetric geometry. The results show that when the stress state is on the tensile meridian the equivalent stress at failure is constant, independent of the hydrostatic pressure. The average equivalent stress at failure is for boron carbide and for silicon carbide. The Brazilian test was only performed on boron carbide and failed at , much higher than when on the tensile meridian () indicating that the effect of the third invariant is significant (because of the difference in the failure strength) and must be accounted for to accurately predict when failure will occur. 相似文献