新型复相陶瓷刀具材料JX—2—Ⅰ协同增韧补强机理的研究

本文研制成功了一种新型陶瓷刀具材料－ＳｉＣ晶须增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具ＪＸ－２－Ⅰ，     

几类典型结构陶瓷材料的冲蚀磨损行为研究

研究了几类典型结构陶瓷材料，如Ａｌ２Ｏ３，ＳｉＣ，Ｓｉ３Ｎ４陶瓷，Ａｌ２Ｏ３－ＺｒＯ２系相变增韧陶瓷（ＺＴＡ，ＴＺＰ）和ＳｉＣｗ／Ｓｉ３Ｎ４系晶须补强陶瓷（ＷＲＳＮ）有９０ｍ／ｓ下的冲蚀磨损性能，以及其与材料性能（硬度，断裂韧性）和冲蚀条件（粒子硬度，冲击角度）之间的关系，分析了冲蚀磨损机制。陶瓷材料的低角冲蚀磨损机制主要包括：研磨状损伤，犁沟状微切削损伤和晶粒剥落。低角冲蚀磨损率随材料硬度的增加     

新型复相陶瓷刀具材料Jx-2-I协同增韧补强机理的研究

本文研制成功的新型陶瓷刀具材料—ＳｉＣ晶须（ＳｉＣｗ）增韧和ＳｉＣ颗粒弥散增韧Ａｌ２Ｏ３陶瓷刀具Ｊｘ－２－Ｉ,该刀具材料具有高的抗弯强度和断裂韧性等优点;对比Ａ（Ａｌ２Ｏ３）、ＡＰ（Ａｌ２Ｏ３／ＳｉＣｐ）、ＡＷ（Ａｌ２Ｏ３／ＳｉＣｗ）、Ｊｘ－１（Ａｌ２Ｏ３／ＳｉＣｗ）和Ｊｘ－２－１（Ａｌ２Ｏ３／ＳｉＣｐ／ＳｉＣｗ）等陶瓷材料的力学性能可以看出,在Ｊｘ－２－Ｉ材料中具有明显的增韧补强叠加效应;本文在热失配分析和微观结构观察的基础上详细研究了Ｊｘ－２－Ｉ刀具材料的增韧补强机理,系统研究了Ｊｘ－２－Ｉ中各种增韧补强机理之间的协同效应。     

AIN在SiC—AIN—Y2O3复相陶瓷中的作用

氮化铝相在ＳｉＣ－ＡＩＮ－Ｙ２Ｏ３复相陶瓷中起着至关重要的作用。在２０５０℃高温时，ＡＩＮ颗粒表面发生固相蒸发现象，并聚集到ＳｉＣ颗粒周围最终形成固溶体，改善了ＳｉＣ颗粒周围最终形成固溶体，改善了ＳｉＣ陶瓷的晶界结构，使该复相材料具有良好的机械性能，其室温抗折强度为６１０ＭＰａ，这一强度可持续至１４００℃高温，断裂韧性达到８．１ＭＰａ．ｍ＾１／２。     

ZTM／SiCp复相陶瓷的力学性能与显微结构分析

本文采用热压工艺制备莫来石一氧化锆一碳化硅复相陶瓷；研究了分散相ＳｉＣ粒子的添加量和粒径对氧化锆增韧莫来石陶瓷力学性能的影响。实验结果表明：ＳｉＣ添加量在１０－３０ｖｏｌ％范围之内，材料力学性能有显著提高，其断裂韧性比ＺＴＭ材料要提高８９％，达８．５ＭＰａｍ＾１／２，弯曲强度要提高９１％左右，达６８０ＭＰａ；通过对断口进行观察，细ＳｉＣ粒子强韧ＺＴＭ陶瓷主要是通过裂纹钉扎和偏转来实现的，当添加一定     

陶瓷复合体中晶须的作用研究

研究了ＳｉＣ，ＴｉＮ晶须增韧Ａｌ２Ｏ３＋ＴｉＣ，Ｓｉ３Ｎ４＋ＴｉＣ基陶瓷复合体的力学行为，验证和讨论了Ｐ．Ｆ．Ｂｅｃｈｅｒ提出的晶须增韧方程，并通过实验对晶须增韧陶瓷复合体的机械性能和切削性能进行了研究。     

Al2O3／SiCW陶瓷刀具材料中晶须的取向对其力学和切削性能的影响

Ａｌ２Ｏ３／ＳｉＣＷ陶瓷刀具材料由于热压过程的影响，造成晶须在基体中定向排布于垂直热压方向的平面上，因此不同方向的补强、增韧效果有所差异。本工作测量了Ａｌ２Ｏ３／ＳｉＣＷ陶瓷刀具材料不同方向上的断裂韧性和抗弯强度，分析了晶须的取向对该陶瓷刀具材料力学性能的影响。切削试验表明晶须的取向对晶须增韧陶瓷刀具材料的磨损和破损性能有较好的影响。根据切削加工过程中刀具的受力特点，提出了有利于切削加工的刀具前、     

SiC—Al2O3基复相陶瓷的N2—HIP研究

通过对热压ＳｉＣ－Ａｌ２Ｏ３复合材料进行了Ｎ２－ＨＩＰ后处理，制备得到Ｓｉ３Ｎ４－ＡｌＮ＝ＳｉＣ－Ａｌ２Ｏ３梯度材料，经Ｎ２－ＨＩＰ处理后，材料抗弯强度提高３５％－９５％，并得到经强度达１０３０ＭＰａ的ＳｉｅＮ４－ＡｌＮ／ＳｉＣｐ－ＳｉＣＷ－Ａｌ２Ｏ３复合材料。     

SiCw增韧Al2O3／TiB2陶瓷复合材料的研究

根据对晶须与基体材料的热胀失配的分析，计算得出了Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ三元复合材料中ＳｉＣｗ的临界体积分数。采用ＴｉＢ２颗粒增韧和ＳｉＣｗ增韧两种途径来改善Ａｌ２Ｏ３的脆性，得到此复合材料的抗弯强度为７４０ＭＰａ，断裂韧性为７．７ＭＰａ·ｍ＾１／２。分析表明：当ＳｉＣｗ含量大于临界体积分数时，强度大幅降低的主要原因是由于致密度的降低和热残余拉应力的增大。     

添加剂对AIN陶瓷力学性能及抗氧化性能的影响

本文研究了Ａｌ２Ｏ３、Ｙ２Ｏ３、Ｌａ２Ｏ３、Ｙ２Ｏ３＋ＳｉＯ２几种类型的添加剂对ＡＩＮ陶瓷力学性能和高温抗氧化性能的影响。结果表明：Ｙ２Ｏ３＋ＳｉＯ２为一种较好的ＡＩＮ陶瓷添加剂，材料在烧结过程中由于２Ｈ＾５Ｓｉａｌｏｎ及８Ｈ－Ｓｉａｌｏｎ等纤维状的Ｓｉａｌｏｎ相形成，对材料起到一种自补强作用，ＳｉＯ２的存在使用ＡＩＮ陶瓷在氧化工程中形成Ｍｕｌｌｉｔｅ保护层，故使ＡＩＮ陶瓷肯有良好的力学性能及高温     

无压烧结碳化硅复合材料的制备与性能研究

以部分碳化钛为增强相投入到碳化硅基体材料中,并投入微量炭黑和碳化硼为烧结活化剂,利用无压固相烧结技术制造了碳化硅基陶瓷复合材料。评测了其力学性能,凭借扫描电镜(SEM)观测了试样的断口形貌与表观形貌,并探讨了其氧化行为。结果表明:在碳化硅中投加部分碳化钛,对复合材料的力学性能有非常大地益处,于9 wt%时达到顶峰,弯曲强度497 MPa,相对密度98.9%,断裂韧性4.79 MPa·m^1/2。复合材料的显微组织构造紧致密实,TiC颗粒在SiC材料中的离散作用而激发的钉扎效果和裂纹偏移转向为其主要的增韧原理。在设定的氧化条件下(1200℃保温2 h),试样表面形成了一层较为致密并可以弱化氧化进程的氧化膜层。     

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.     

Decomposition of NO on Tungsten Carbide and Molybdenum Carbide Surfaces

The decomposition of ¹⁵NO on C/W(111), C/W(110), and on monolayer and bulk C/Mo/W(111) surfaces is compared based on temperature-programmed desorption (TPD) and Auger electron spectroscopy (AES) measurements. Our results indicate that the decomposition of ¹⁵NO occurs readily over all surfaces, and the only ¹⁵N-containing reaction products are ¹⁵N₂ and ¹⁵N₂O under our experimental conditions. Much higher surface reactivity for ¹⁵NO decomposition was observed over the more open-structured C/W(111) surface, with a value of 0.68 ¹⁵NO/W, in contrast to the surface reactivity of 0.24 ¹⁵NO/W over the close-packed C/W(110) surface. The selectivity of these two ¹⁵N-containing reaction products depends on the structure of the substrates as well. The more open-structured C/W(111) surface favors the production of ¹⁵N₂, with a product selectivity of ¹⁵N₂ being approximately 87%. In contrast, the selectivity to ¹⁵N₂ is only about 52% on C/W(110). In addition, we have investigated the decomposition of ¹⁵NO on C/Mo surfaces that were epitaxially grown on W(111). The selectivity of ¹⁵N₂ on C/Mo/W(111) surfaces is 88%, which is very similar to that observed on C/W(111). Finally, the general similarity between the DeNOx chemistry on carbides and on Pt-group metals will also be discussed.     

国产化干法乙炔装置运行总结

总结了国产化干法乙炔装置2次开车情况,给出了装置的实际运行指标,并详述了开车过程中发现的问题及改进办法。     

Effect of Carbon Containing Materials on Pure Carbon Reaction-bonded SiC

Petroleum coke, graphite, gas carbon and lower sulfur carbon black were used to prepare reaction-bonded silicon carbide. The influences of different carbon containing materials on properties of carbonaceous precursors, sintering process, and microstructure of the prepared SiC were researched. The results show that ： （ 1 ） With the density of carbon containing materials increasing, the porosity of carbonaceous precursors decreases and the infiltrating process of liquid silicon is more difficult. （2） The reaction between carbon containing materials and liquid silicon, the volume effect is more obvious with the density of carbon containing materials increasing. （3） As the carbon containing materials density decreasing, residual carbon in reaction bonded SiC also decreases.     

电石法生产PVC需要注意的问题

叙述了电石法PVC的生产工艺及目前国内电石生产的现状,着重指出电石法生产PVC工艺中需要重视的要点。     

Comparison between tungsten carbide and molybdenum carbide for the hydrodenitrogenation of carbazole

The activity of molybdenum and tungsten carbides in hydrodenitrogenation (HDN) of carbazole was studied. Transition metal carbides (Mo₂C and W₂C) were synthesized using the temperature-programmed reaction of the appropriate oxide precursor (MoO₃ and WO₃) with the following gas mixture: 10 vol.% CH₄/H₂. The structure of the catalysts was characterized using X-ray diffraction, CO chemisorption, high resolution transmission electron microscopy (HRTEM) and BET surface area measurements. From the HRTEM analysis, it could be concluded that the tungsten carbide was thioresistant in our operating conditions (50 ppm of S, pressure = 6 MPa, 553 < T < 653 K, H₂/feed volumic ratio = 600). In the case of Mo₂C, molybdenum sulphide was observed as single slabs. The activity of catalysts was determined during the hydrodenitrogenation of carbazole at the wide range of temperature (553–653 K) and under a 6 MPa total pressure of H₂. The comparison of tungsten carbide and molybdenum carbide has shown higher activity of Mo₂C than W₂C at the same condition. However, W₂C leads to higher amount of isomers of main products, and have higher hydrogenation activity.     

Comparison of molybdenum carbide and tungsten carbide for the hydrodesulfurization of dibenzothiophene

The molybdenum and tungsten carbides (Mo₂C and W₂C) were synthesized, characterized and tested in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The phase purity of these catalysts was established by X-ray diffraction (XRD), and the surface properties were determined by N₂ BET specific surface area (Sg) measurements, CO chemisorption and high-resolution transmission electron microscopy (HRTEM). The activities of catalysts were determined during the HDS of DBT at a temperature of 613 K and under a 6 MPa total pressure. Both molybdenum and tungsten carbides were active in HDS of DBT. The reactivity studies showed that molybdenum carbide was more active than tungsten carbide related to weight. However, W₂C was shown to possess stronger hydrogenating properties.     

The effect of the third invariant on the strength and failure of boron carbide and silicon carbide

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.     

Seamless joining of silicon carbide ceramics through an sacrificial interlayer of Dy3Si2C2

A ternary carbide Dy₃Si₂C₂ coating was fabricated on the surface of SiC through a molten salt technique. Using the Dy₃Si₂C₂ coating as the joining interlayer, seamless joining of SiC ceramic was achieved at temperature as low as 1500 °C. Phase diagram calculation indicates that seamless joining was achieved by the formation of liquid phase at the interface between Dy₃Si₂C₂ and SiC, which was squeezed out under pressure and continuously consumed by the joining interlayer. This work implies the great potential of the family of ternary rare-earth metal carbide Re₃Si₂C₂ (Re = Y, La-Nd) as the sacrificial interlayer for high-quality SiC joining.