添加石墨烯或碳纳米管对Si3N4结合SiC陶瓷强度的影响

以Si3N4结合SiC材料为基础,通过添加不同形态的碳纳米材料来改善其力学性能.采用Si和SiC为主要原料,添加不同含量（1wt％和3wt％）的石墨烯（GPL）和碳纳米管（CNT）,氮气气氛下,在1600℃烧结制备Si3N4结合SiC复合陶瓷材料.对试样的气孔率、体积密度和耐压强度等基本烧结性能进行了测试.借助XRD和SEM等方法对试样的物相组成和显微结构进行了表征.实验结果表明,当石墨烯含量为1wt％时,Si3N4/SiC的耐压强度为207MPa,试样的体积密度及显气孔率较好.当碳纳米管含量为3wt％时,力学性能增强,耐压强度达到了247MPa.     

Improving the electrical and microwave absorbing properties of Si3N4 ceramics with carbon nanotube fibers

Carbon nanotube fibers (CNTFs) reinforced Si₃N₄ ceramics has been prepared by incorporating CNTF preforms into ceramic precursor and followed by the sintering process. A SiC interface layer is formed due to the chemical reaction between Si and CNTs, leading to a good bonding between CNTs and Si₃N₄ matrix. Due to the ceramic deposition, the oxidation resistance is increased of 200 °C. Furthermore, the CNTs have well orientation and high-volume distribution (7 wt%) in the hybrid composites. Obvious improvements of the electrical conductivity (up to 103 S/m) and the microwave absorbing performance (up to 6 dB at 15 GHz) are obtained for the composites containing CNTFs. Our work provides a meaningful way to fabricate multifunctional ceramics possessing high electrical and microwave absorbind properties.     

Cup-stacked carbon nanotubes hybridized Si3N4/Si3N4 composite ceramics for high-effciency microwave absorption with excellent thermal stability

Hybridization between carbon nanotubes (CNTs) and Si₃N₄ is a promising strategy for developing high-temperature microwave absorption (MA) materials for military application. Toward long-life services, it's important to achieve strong MA at a filler loading as low as possible on account of antioxidant protection against CNTs wastage. Herein, cup-stacked CNTs (CSCNTs) have been prepared in porous Si₃N₄ ceramics by chemical vapor deposition (CVD) and then CVD Si₃N₄ has been coated on them, forming CSCNT-Si₃N₄/Si₃N₄ composite ceramics. Results show that CSCNTs possess abundant exposed atomic edges on the outer surface and in the inner channel. Such unique defects not only benefit the impedance match but also cause considerable conductive loss, which helps CSCNT-Si₃N₄/Si₃N₄ with a filler content of only 0.79 wt% to achieve an effective absorption bandwidth (EAB) of 3.74 GHz in the X band at a thickness of 3.5 mm coupled with a minimum reflection loss of ?43.3 dB and an EAB covering the entire Ku band at a thickness of 2.25 mm. The ultralow filler loading generates a high efficiency of CVD Si₃N₄ in protecting CSCNTs against high-temperature oxidation, leading to a steady MA performance for CSCNT-Si₃N₄/Si₃N₄ during 23–1200 °C thermal shock tests in air.     

Synthesis of Si3N4/SiC reaction-bonded SiC refractories: The effects of Si/C molar ratio on microstructure and properties

Si₃N₄/SiC reaction-bonded SiC refractories have been fabricated on the basis of the microstructure design concept by introducing a binary-phases binding system. The influence of Si/C molar ratio on phase transformation, microstructure and mechanical properties was studied systematically. Thermodynamic analysis result proved the microstructure design was feasible under 0.03 MPa pressure of N₂ and the selected sintering temperature. In-situ grown SiC nano-whiskers/granule and lamellar Si₃N₄ were both observed in the matrix. The specimen with 2:1 Si/C molar ratio possessed highest cold modulus of rupture (28.27 MPa) but showed low toughness. The strength and toughness of such materials were controlled by two main factors, such as SiC grain boundary binding morphology and in situ grown of SiC in the matrix. The different mechanisms occurred predominantly to meet diverse practical cases and caused to various mechanical properties of final products. The corresponding strengthening and toughening mechanisms were explained in this paper.     

反应烧结形成氮化硅/碳化硅材料

介绍了反应烧结形成氮化硅／碳化硅材料的制备工艺，对该材料的微观结构、性能及其影响因素进行了阐述，并介绍了该材料的应用背景。     

SiC原料颗粒级配对Si3N4结合SiC复合陶瓷材料的影响

采用SiC粉和Si粉高温氮化反应烧结制备Si3N4结合SiC复合陶瓷材料。研究四种SiC原料粉体(0-1mm、74μm、44μm、和0.5μm)中三种不同粒度不同含量颗粒级配对Si3N4结合SiC复合陶瓷材料的影响。通过X射线衍射仪和扫描电子显微镜对试样的物相和显微结构进行表征,并对试样的耐压强度等力学性能进行测试。结果表明:采用三种SiC较细粉体颗级配且如下组成:74μm的含量为5 wt%,44μm的含量为10 wt%,0.5μm的含量为35 wt%,所制备的Si3N4结合SiC陶瓷材料的基本烧结性能较好,其体积密度为2.43g/cm3,耐压强度为324MPa。     

氮化硅结合碳化硅管状制品的研制

简介了氮化硅结合碳化硅管状制品研制的必要性 ,确定了原材料及粒度配比 ,选择了合适的成型方法及添加剂 ,介绍了氮化烧成机理。研制出的制品其质量和使用性能接近同类进口产品 ,具有良好的市场前景和广泛的推广应用价值。     

氮化硅结合碳化硅材料的生产与应用

阐述了氮化硅结合碳化硅窑具材料的生产技术、生产工艺流程及使用情况。指出作为现代窑具的替代产品,它具有较好的市场前景     

利用硅废料燃烧合成碳化硅/氮化硅复合粉体

对在太阳能等行业生产过程中产生的硅废料进行回收或重复利用具有重要的经济价值,但目前的回收方法普遍存在成本较高等问题.本文利用商业硅粉和硅废料为原料,通过高温自蔓延合成方法合成复合Si3N4/SiC陶瓷粉体.结果显示产物的显微形貌与原料配比和氮气压力有较大关系.随着氮气压力的升高,β-Si3N4的比例增加.在较低温度的临界状态下,会形成片状Si3 N4晶体.     

Nitrogen-doped-CNTs/Si3N4 nanocomposites with high electrical conductivity

Novel highly electrically conducting nanocomposites consisting of a silicon nitride (Si₃N₄) ceramic matrix containing up to 13.6 vol.% of nitrogen-doped multi-walled carbon nanotubes (CNx) were fabricated. As-synthesized CNx were treated with hydrogen peroxide in order to efficiently detach/isolate the nanotubes from bundles, then they were mixed with the ceramic powders and fully densified using the spark plasma sintering (SPS) technique. Composites containing 13.6 vol.% CNx reached an electrical conductivity of 2174 S m⁻¹ that is the highest value reported hitherto for carbon nanotubes/Si₃N₄ nanocomposites. The nitrogen doping also favored a strong mechanical interlocking between the nanotubes and the Si₃N₄ matrix; when compared to the undoped carbon nanotubes. These novel nanocomposites could be used in devices associated to power generation or telecommunications.     

Pressure‐less joining of C/SiC and SiC/SiC by a MoSi2/Si composite

A MoSi₂/Si composite obtained in situ by reaction of silicon and molybdenum at 1450°C in Ar flow is proposed as pressure‐less joining material for C/SiC and SiC/SiC composites. A new “Mo‐wrap” technique was developed to form the joining material and to control silicon infiltration in porous composites. MoSi₂/Si composite joining material infiltration inside coated and uncoated C/SiC and SiC/SiC composites, as well as its microstructure and interfacial reactions were studied. Preliminary mechanical strength of joints was tested at room temperature and after aging at service temperatures, resulting in interlaminar failure of the composites in most cases.     

Developing high performance in titanium carbide nanocomposites containing hybrid SiC nanowire and CNT

Lightweight titanium carbide (TiC) has garnered considerable engineering applications in various advanced manufacturing industries. However, the intrinsic brittleness of TiC significantly limited its further applications. High-toughness and damage-tolerance TiC is always highly desirable for industry. Herein, we developed high-performance TiC nanocomposites reinforced by hybrid carbon nanotube (CNT) and SiC nanowire (SiC_nw) through two-step spark plasma sintering, highlighting the synergic role of CNT and SiC_nw on the microstructure and properties of the TiC matrix. Specifically, CNT was helpful in maintaining the high aspect ratio of SiC_nw during the sintering process, while SiC_nw contributed to the homogeneous distribution of CNT throughout the TiC matrix. The flexural strength and fracture toughness were simultaneously enhanced by 48.1% and 56.9% in case of CNT/SiC_nw ratio of 1:2 comparing with pure TiC, respectively. This study provided the new insight on developing high-performance TiC materials.     

Si3N4结合SiC板材及其标准

简介了Si_3N_4结合SiC板材制品的生产过程,较为详细地介绍了该项标准制订情况,叙述了标准中产品的形状及代号、规格尺寸、技术要求和产品检验等内容,并对标准的应用情况进行了说明,使标准的应用者正确理解。     

Wet chemical deposition of BN,SiC and Si3N4 interphases on SiC fibers

Fiber coatings based on BN, BN/SiC and BN/Si₃N₄ were deposited on Hi Nicalon type S SiC fibers. The coating parameters were optimized using a design of experiments study. With optimized parameter sets, the coatings exhibited a high degree of coverage on the fibers and almost no fiber bridging could be observed. The coated fiber bundles are flexible and can be processed further by techniques such as filament winding. In comparison to a non-processed reference sample, the maximum tensile load of the fiber bundles with BN, BN/SiC and BN/Si₃N₄ coatings was reduced by only 5 %, 13 % and 10 %, respectively. The coated fiber bundles retained their tensile strength after thermal annealing up to 1650 °C in a nitrogen atmosphere for 0.5 h. SiC_f/SiC samples with BN/SiC fiber coatings exhibited higher values of bending strength and strain-to-failure as a reference sample without fiber coating indicating the functionality of the fiber coatings.     

Investigation on The Properties of Fe-Si3N4 Bonded SiC Composite

The mechanical properties of pressureless sintering Fe-Si3N4 bonded SiC and Si3N4 bonded SiC with same manufacture process have been compared in this paper.The oxidizing mechanism of Fe-Si3 N4 bonded SiC ceramic matrix composite has been investigated especially through TG-DSC (thermo gravimetric analysis-differential scanning calorimeter) experiment. During oxidation procedure the main reaction is the oxidation of SiC and Si3 N4, SiO2 which form protecting film to prevent further oxidizing. And residual iron in the samples become Fe2O3 and Fe3O4, the oxidation kinetics at 1100 - 1300℃ of Fe-Si3N4 bonded SiC has been studied especially. The weight gain per unit area at initial stage changes according to beeline rule, in the middle according to conic, and in the last oxidation period follows parabola rule,     

ZnCo2O4/CNT composite for efficient supercapacitor electrodes

Due to their combination of enhanced electrical conductivity and high-performance electron and ion transport channels, binary metal oxides with well-morphological optimized electrode materials have been attracted the greatest research attention for high-performance supercapacitor applications. An easy co-precipitation method is used to synthesize ZnCo₂O₄ nanoparticles using NaOH and Urea as precipitation agents. To facilitate electrical conductivity, suitable carbon material such as carbon nanotube (CNT) has been added to make a composite material. The three-electrode system was preferred for estimating specific capacitance of prepared material and optimally efficient ZnCo₂O₄/CNT electrode delivered a moderate 888 F/g capacitance at 1 A/g in 3 M KOH and after 5000 charge discharge cycles 94.72% of cycling stability retained at 5 A/g. This paper presents a little price and simple procedure for preparation of ZnCo₂O₄/CNT electrode that promotes creative sprit for energy storage applications.     

氮化硅铁结合SiC复合材料的氧化行为

以工业SiC和硅铁粉为原料,二者的配料组成(质量分数)分别为90%和10%,外加2%的黄糊精为暂时结合剂,采用半干法机压成型后在氮化炉中于1380℃5h氮化烧成制备出氮化硅铁结合SiC复合材料,在变温(常温~1400℃)氧化试验的基础上,分别在1100℃、1200℃和1300℃进行了等温氧化试验,并且分析了1300℃3h氧化后试样的显微结构和相成分。结果表明,氮化硅铁结合SiC复合材料在1100~1300℃范围内的氧化规律为:氧化初期,试样单位面积的质量变化符合直线规律;氧化中期,近似符合二次曲线;氧化后期,符合抛物线规律。与气孔较多的内部相比, 1300℃3h氧化后试样的表面生成了一层较致密的氧化层,检测后认为,表面含有较多的SiO2,在高温下弥合了表面气孔,阻止了试样的进一步氧化。     

SiC表面处理对Si3N4-SiC材料显微结构的影响

摘要在用反应烧结法制备Si3N4结合SiC复合材料时,如在反应前对SiC原料进行高温表面处理,可使SiC颗粒表面生成一层SiO2氧化层,该氧化层在高温、氮气气氛中会生成Si3N4颗粒或纤维,从而有效连接各SiC颗粒。     

影响Si3N4结合SiC制品烧结的各因素及机制

探讨了各因素如SiC尺寸及数量、原料颗粒级配，硅粉添加量，添加剂，氮气纯度及最终反应温度对反应烧结Si3N4结合SiC制品性能的影响及其作用机理。     

In-situ formation of Ti3SiC2 interphase in SiCf/SiC composites by molten salt synthesis

Titanium silicon carbide (Ti₃SiC₂) film was synthesized by molten salt synthesis route of titanium and silicon powder based on polymer-derived SiC fibre substrate. The pre-deposited pyrolytic carbon (PyC) coating on the fibre was utilized as the template and a reactant for Ti₃SiC₂ film. The morphology, microstructure and composition of the film product were characterized. Two Ti₃SiC₂ layers form the whole film, where the Ti₃SiC₂ grains have different features. The synthesis mechanism has been discussed from the thickness of PyC and the batching ratio of mixed powder respectively. Finally, the obtained Ti₃SiC₂ film was utilized as interphase to prepare the SiC fibre reinforced SiC matrix composites (SiC_f/Ti₃SiC₂/SiC composites). The flexural strength (σ_F) and fracture toughness (K_IC) of the SiC_f/Ti₃SiC₂/SiC composite is 460 ± 20 MPa and 16.8 ± 2.4 MPa?m^1/2 respectively.