碳化硅材料热扩散系数的外推法应用研究

随着计算机技术、微电子技术和激光技术的快速发展,为实现非稳态法中的激光闪光法测量提供了良好的技术支持。本文利用NETZSCH LFA 427设备在室温环境下,通过改变电压强度和脉冲宽度的值,得到一系列碳化硅材料的等效热扩散系数,通过外推法得到样品的固有热扩散系数。其次,探究了碳化硅样品厚度对热扩散系数测量结果的影响,从热穿透深度的角度解释了不同厚度样品测量结果偏差的原因,并给出了样品厚度的选择原则。同时解释了在高脉冲积分下,测得样品热扩散系数结果偏小的原因,由此可说明,通过实验测量和理论外推相结合的方法,得到了更准确的热扩散系数结果。     

激光闪射法测量耐火材料的热物理性能

介绍了应用激光闪射法测量耐火材料比热容、热扩散系数以及导热系数等热物理性能的原理,列举应用实例说明了测试方法,并且讨论了影响实验数据准确性的因素。     

氧氮化硅结合碳化硅窑具材料研究

利用热力学分析了氧氮化硅结合相的生成机理。探讨了硅粉加入量对氧氮化硅生成量、材料的各项理化性能以及抗氧化性能的影响。结果表明：氧氮化硅的含量随Ｓｉ含量的增加而增加,制品的常温耐压强度和荷重软化温度相应提高     

氮化硅结合碳化硅窑具材料的研制

本文研究了最终氮化温度以及硅加入量对氮化对反应结合碳化硅对材料性能的影响，通过Ｘ射线衍射仪对材料进行物相分析，发现反应温度对材料的机械性能起差重要作用，若温度过低则反应不完全，而温度过高则生成大量β－Ｓｉ３Ｎ４，导致强度降低。实验结果还表明，随着硅加入量的增加，在一定范围内材料的强度和断裂韧性也同步提高。     

氮化硅结合碳化硅喷嘴的成形工艺研究

通过对比分析普通石膏模注浆成形、微压注浆成形、振动注浆成形3种成形工艺在氮化结合碳化硅脱硫喷嘴成形过程中的优缺点,以及3种成形工艺坯体密度和试样抗弯强度变化,确定了氮化硅结合碳化硅最佳成形工艺.同时深入研究了振动时间对振动注浆成形密度的影响,确定了最佳振动时间.     

高炉用氮化硅结合碳化硅制品化学分析方法的研究

确定了高氧化铝含量（０．５％－２０％）的高炉用氮化硅结合碳化硅制品中Ｓｉ３Ｎ４、ＳｉＣ、ｆＳｉ、ＳｉＯ２、Ｆｅ２Ｏ３、Ａｌ２Ｏ３六种化学成分的化学分析方法试验条件．并按条件试验选择了分析方法，进行了精密度、准确度和实际工作的考核，证明了本分析方法可靠、切实可行，能满足科研工作和生产的要求。     

氮化硅结合碳化硅树料的抗渣侵蚀性

借助光学显微镜、扫描电子显微镜和Ｘ射线衍射分析等手段，研究了矿渣侵蚀后的氮化硅结合碳化硅材料的显微结构和物相组成．探讨了氮化硅结合碳化硅材料的损坏机理。     

氧氮化硅结合碳化硅制品的生产与使用

以工业用黑色碳化硅砂、硅粉为主要原料，研制出了导热性能优良、抗热震性好、耐高温、耐侵蚀及耐磨损，且生产工艺较简单、成本较低的氧氮化硅结合的碳化硅制品．该产品已广泛应用于冶金炉、化工设备及发电用锅炉的内衬，并取得了较满意的效果。     

提高氮化硅结合碳化硅窑具使用性能的研究

氮化硅结合碳化硅窑具的抗热震性能被破坏、不合理的支撑方式、承重变形因素导致其使用性能降低,影响了氮化硅结合碳化硅窑具的使用寿命。本研究制备了氮化硅结合碳化硅窑具,并结合生产实际主要研究了如何提高材料的抗氧化性、抗热震性以及其他高温理化性能,使氮化硅结合碳化硅窑具使用寿命延长。     

氮化硅结合碳化硅的重烧结研究

对氮化烧成后的氮化硅结合碳化硅试样进行了不同温度下的重烧结研究。实验结果表明，重烧结后的试样的常温三点抗弯强度平均提高约69％，HRA硬度值平均也有14％的提升，相组织含量发生微量变化，微观组织气孔由不规则形状遂渐趋圆．氮化生成物微颗粒之间产生成片连接。经过重烧结的材料。更适合于高温下的使用。     

氮化硅结合碳化硅耐火材料在钢水中的腐蚀行为

运用扫描电镜（ＳＥＭ）技术，研究了氮化硅结合碳化硅耐火材料在钢水中的腐蚀行为。结果表明，金属与氮化硅结合碳化硅材料之间的界面清晰，基体内部无任何金属渗入，但氧化的材料表面有氧化物粘附。     

氮化物结合碳化硅耐火材料的研究现状

分别概述了以氮化硅、赛隆和氧氮化硅作为结合相 的SiC材料的结构特点、理化性能、生产工艺和应用情况,详细 介绍了国内这3种材料的研究现状,并对今后氮化物结合SiC 材料的研究内容提出了自己的观点。     

Direct laser sintering of reaction bonded silicon carbide with low residual silicon content

Additive manufacturing (AM) techniques are promising manufacturing methods for the production of complex parts in small series. In this work, laser sintering (LS) was used to fabricate reaction bonded silicon carbide (RBSC) parts. First, silicon carbide (SiC) and silicon (Si) powders were mixed in order to obtain a homogeneous powder. This powder mixture was subsequently laser sintered, where the Si melts and re-solidifies to bind the primary SiC particles. Afterwards, these SiSiC preforms were impregnated with a phenolic resin. This phenolic resin was pyrolysed yielding porous carbon, which was transformed into secondary reaction formed SiC when the preforms were infiltrated with molten silicon in the final step. This resulted in fully dense RBSC parts with up to 84?vol% SiC. The optimized SiSiC combined a Vickers hardness of 2045?HV, an electrical conductivity of 5.3?×?10³?S/m, a Young's modulus of 285?GPa and a 4-point bending strength of 162?MPa.     

Improvement of toughness of reaction bonded silicon carbide composites reinforced by surface-modified SiC whiskers

To improve the reliability, especially the toughness, of the reaction bonded silicon carbide (RBSC) ceramics, silicon carbide whiskers coated with pyrolytic carbon layer (PyC-SiC_w) by chemical vapor deposition (CVD) were introduced into the RBSC ceramics to fabricate the SiC_w/RBSC composites in this study. The microstructures and properties of the PyC-SiC_w/RBSC composites under different mass fraction of nano carbon black and PyC-SiC_w were investigated methodically. As a result, a bending strength of 550 MPa was achieved for the composites with 25 wt% nano carbon black, and the residual silicon decreased to 11.01 vol% from 26.58 vol% compared with the composite of 15 vol% nano carbon black. The fracture toughness of the composites reinforced with 10 wt% PyC-SiC_w, reached a high value of 5.28 MPa m^1/2, which increased by 39% compared to the RBSC composites with 10 wt% SiC_w. The residual Si in the composites deceased below to 7 vol%, resulting from the combined actively reaction of nano carbon black and PyC with more Si. SEM and TEM results illustrated that the SiC_w were protected by PyC coating. A thin SiC layer formed of outer surface of whiskers can provide a suitable whisker-matrix interface, which is in favor of crack deflection, SiC_w bridging and pullout to improve the bending strength and toughness of the SiC_w/RBSC composites.     

Preparation of reaction bonded silicon carbide (RBSC) using boron carbide as an alternative source of carbon

RBSC composites are fully dense materials fabricated by infiltration of compacted mixtures of silicon carbide and carbon by molten silicon. Free carbon is usually added in the form of an organic resin that undergoes subsequent pyrolysis. The environmentally unfriendly pyrolysis process and the presence of residual silicon are serious drawbacks of this process. The study describes an alternative approach that minimizes the residual silicon fraction by making use of a multimodal particle size distribution, in order to increase the green density of the preforms prior infiltration. The addition of boron carbide provides an alternative source of carbon, thereby eliminating the need for pyrolized organic compounds. The residual silicon fraction in the RBSC composites, prepared according to the novel processing route, is significantly reduced. Their mechanical properties, in particular the specific flexural strength is by 15% higher than the value reported for RBSC composites prepared by the conventional approach.     

Evaluation of tribological behavior of silicon carbide and silicon nitride ceramics under different conditions

A comparative analysis of the tribological behavior of commercially available sintered silicon carbide (SiC) and three different types of silicon nitride (Si₃N₄) ceramics have been carried out using the ball-on-disk method in dry and lubrication (deionized [DI] water and ethanol) environment. Scanning electron microscopy (SEM) was used to understand the morphology and chemical composition of the tribo-surfaces. Sintered SiC (Hexoloy-SA) had the highest friction coefficient during dry sliding with an average of ∼0.34. Deionized water showed a minor improvement in friction (∼0.27) while ethanol reduced the friction greatly to ∼0.18 compared to dry sliding. During dry sliding, the presence of an abrasive third body was responsible for the high wear rates (WRs) in these compositions. Hexoloy-SA showed a lower WR during ethanol and DI water lubrication due to the formation of stable tribofilms as well as higher hardness which resisted the formation of third bodies. In comparison, Si₃N₄ samples showed a lower WR in DI water and ethanol. The samples also showed composition-dependent behavior which indicates that grain structure and grain boundary chemistry are playing a vital role in the tribological process.     

Robocasting of reaction bonded silicon carbide structures

A novel shaping method for the fabrication of reaction bonded silicon carbide structures was investigated in this work. A paste consisting of silicon carbide as inert filler and carbon powder was developed and printed by robocasting technology. Layer by layer deposition of the ceramic paste facilitates the printing of complex shaped structures. Different structures such as lattices, hollow cylinders, bending bars and gyroids were printed using nozzles with diameter of 0.5 mm and 1.5 mm. After pyrolysis at 700 °C and further heat treatment at 1850 °C the samples were infiltrated using the liquid silicon infiltration technique to obtain dense near-net shape RBSC structures. The robocasted structures showed a hardness of approximately 20 GPa, a thermal conductivity of ～112 W/m*K, Young’s modulus of ～356 GPa, flexural strength of ～224 MPa and an amount of residual silicon of approximately 23%. These measured properties are comparable with those of traditionally fabricated RBSC.     

Corrosion behavior of silicon nitride bonded silicon carbide refractory material by molten copper and copper slag

Silicon Carbide refractories may be used in contact with copper and copper slags. The object for the investigation of corrosion by the melt of copper and the copper slag was SiC siphon block of the slag collector in the runner of the cathode shaft furnace. It is exposed to the permanent flow of copper with small amount of slag. Slag on the surface of the melt is stopped by siphon block and it suffers the most extensive corrosion wear, but the same time it is a good object for investigation, because different parts of this plate are exposed to intensive corrosion by different corrosive agents.General observations show, that the corrosion of Si₃N₄-SiC by slag is sufficiently more extensive and the wear is about 3 mm per month, while the wear by the flowing copper is below 1 mm per month.The observation of the cross section of the exposed Si₃N₄-SiC plate on macro level shows 4–5 zones of different color. Microstructural observations show almost no changes of the material in direct contact with molten copper without exposure of air, that suggests slow dissolution of Silicon Carbide and Silicon Nitride in the flowing melt of copper (physical dissolution in case of permanent removal of reactants). The most severe wear of Si₃N₄-SiC refractory is by slag, because the chemical erosion takes place.