复相化处理对S135钻杆钢组织和性能的影响

采用金相显微镜(OM)、扫描电镜(SEM)及力学性能测试等方法,研究了复相化处理对S135钻杆钢显微组织及力学性能的影响。结果表明:在760～800℃进行复相化处理,获得铁素体+马氏体的双相组织。随着复相化处理温度的升高,马氏体体积分数不断增加,铁素体体积分数不断减少,材料的硬度和强度升高,塑性和韧性下降,材料由韧性断裂向脆性断裂转变,其微观断口形貌由最初的韧窝转变为解理。复相化处理后,材料的应变硬化指数n升高,且由原来的一个n值变为两个n值。

复相增强增韧碳化硼陶瓷的研究

碳化硼是一种非常坚硬的材料,硬度可达到5000MPa(即50GPa),在1000℃可以抵抗空气的腐蚀,具有较高的抗酸性和抗碱性,可以用作磨料、切削刀具、耐磨零件喷嘴、轴承、车轴等,利用它导热性好,热膨胀系数低、能吸收热中子的特性,可以制造高温热交换器,核反应堆的控制剂。利用它耐酸碱性好的特性,可以制作化学器皿,熔融金属坩埚等。通过B4C和TiC的化学反应、Si和C的化学反应,在碳化硼基体内原位反应生成TiB2和SiC晶相,生成的TiB2晶粒粒径:0.5~1μm,SiC晶粒粒径: 3μm以下,且两种晶相均匀分布在碳化硼基体中。当加入20wt%TiC粉末和 14wt%Si粉末时,复相碳化硼陶瓷的断裂韧性KIC值达到 6.08 MPa.M1/2,维氏硬度HV值达到32.5Gpa,分别比纯碳化硼性能提高19.8%、10.9%;当加入26wt%TiC粉末和18wt%Si粉末时,则复相碳化硼陶瓷断裂韧性KIC值达到6.48 MPa.M1/2和维氏硬度HV值达到 32.63 Gpa,分别比纯碳化硼性能提高33%、11.4%。在复相陶瓷中B4C、TiB2和SiC这3种晶相热膨胀系数的不匹配产生残余应力,从而产生应力偏转和微裂纹增韧,同时裂纹沿着B4C、TiB2和SiC的晶界扩展,避免出现穿晶出现,是陶瓷增韧增强的主要机理,同时产生的游离碳和游离硅反应生成SiC晶相,能进一步延长裂纹在晶界处扩展速率。

原位合成碳化硅-硼化钛复相陶瓷的高温摩擦性能及其磨损机理

以SiC为基体,用TiC和B4C为原料反应生成TiB2,原位合成了SiC TiB2复相陶瓷。通过测试SiC和SiC TiB2的高温摩擦系数和比磨损率与温度、外加载荷的关系,研究了SiC TiB2复相陶瓷的高温摩擦学性能。在空气中,外加载荷为0.2 MPa,摩擦速度为0.3 m/s时,SiC TiB2复相陶瓷自对偶(SiC TiB2/SiC TiB2)高温摩擦呈现较好的高温自润滑性能。温度对SiC TiB2/SiC TiB2摩擦系数和比磨损率的影响与载荷有关。载荷为0.4 MPa时,比磨损率最大。用X射线衍射测试了SiC TiB2/SiC TiB2磨屑的组成,用扫描电子镜观察了SiC TiB2/SiC TiB2磨损断面,发现高温摩擦氧化是TiB2SiC/SiC TiB2磨损的主要机理。磨损断面包含摩擦氧化层、过渡层和基体亚表面3层,氧化层和过渡层接触紧密。磨屑具有典型包裹结构,其主要氧化物是无定形氧化硅。平滑的氧化层改进了摩擦表面的塑变性能,缓冲了摩擦应力,减小了高温比磨损率。

硼化锆基碳化硅复相陶瓷

以钇铝石榴石(yttriumaluminumgarnet,YAG)为烧结助剂,通过无压烧结工艺制备了ZrB2-SiC复相陶瓷。研究了复相陶瓷的相组成、抗烧蚀性能以及烧结助剂含量、烧结温度对复相陶瓷力学性能和显微结构的影响。结果表明:复相陶瓷的物相组成主要为ZrB2,SiC和少量玻璃相;添加YAG或提高烧结温度能使材料的晶粒显著长大,并显著提高材料的相对密度和力学性能。当YAG含量为9%(质量分数),烧结温度为1800℃时陶瓷的相对密度为97.1%、Rockwell硬度HRa为88、弯曲强度为296MPa、断裂韧性为5.6MPa·m1/2。复相陶瓷具有优异的超高温抗烧蚀性能,在2800℃烧蚀30min,烧蚀率仅为0.001mm/s,烧蚀后的显微结构呈现复杂的多层结构。

高强度螺栓形变调质复相强韧化工艺探讨

一、前言 30CrMnSiA钢有较高强度、良好塑性、材料来源广、价格较低等特点,用它制造的高强度螺栓广泛应用于航空、化工、兵器、桥梁、重型机械等承受高强度受力结构连接件。传统工艺是调质热处理,虽能达到技术条件,但时而存在强度、韧性偏下限值或不足,返修重复淬火后力学性能满足要求,但使用中有滑牙、堆牙等早期失效现象,经检测发现,

ZrB_(2)–SiC–Zr_(2)Al_(4)C_(5)复相陶瓷烧结反应机理与高温氧化行为

ZrB_(2)基复相陶瓷在超高温领域有着重大应用潜力,但其韧性低、抗氧化性差限制了其实际应用。以Zr、B4C、Al、C和Si粉为原料,采用反应放电等离子体烧结制备出ZrB_(2)–SiC–Zr_(2)Al_(4)C_(5)复相陶瓷,研究了反应过程和反应机理,探究了Zr_(2)Al_(4)C_(5)含量和氧化温度对复相陶瓷高温氧化行为的影响,揭示了其抗氧化机制。结果表明:900℃时,B4C和Zr反应开始生成ZrB_(2);1100℃开始生成SiC;1400℃时反应初期形成的Zr3Al3C5与ZrC及Al4C3生成了Zr_(2)Al_(4)C_(5);但随着温度继续升高Zr_(2)Al_(4)C_(5)则会转化为Zr3Al4C6。复相陶瓷氧化后主要物相为ZrO_(2)、ZrSiO_(4)和铝硅酸盐以及SiO_(2)玻璃相;随着Zr_(2)Al_(4)C_(5)含量的增加,氧化层表面呈现出凹凸不平、疏松多孔,存在明显的长条状晶粒和不均匀分布的玻璃相。本工作为深化对ZrB_(2)–SiC基复相陶瓷的高温氧化行为的理解提供了实验依据,为开发高性能ZrB_(2)–SiC基高温复相陶瓷提供了实验与理论支持。

强韧化热处理对模具材料性能的影响因素

介绍了模具损伤的基本形式,影响模具使用寿命的基本因素,分析了模具失效的形式与原因,评述了热处理对模具使用寿命的影响。针对模具的失效原因,提出用强韧化热处理与工艺优化提高模具材料的性能以提高模具寿命。通过试验将强韧化工艺与传统工艺进行了对比,测出了经两种工艺处理过试件的硬度、断裂韧性等直接影响模具寿命的性能参数。研究表明:经强韧化工艺处理后的模具,综合性能得到了大幅度的提高,基本上避免了开裂的发生。

新一代钢铁材料的研究开发现状和发展趋势

阐述了国内外新一代钢铁材料开发的现状,指出了新一代钢铁材料的发展趋势。即:继续坚持细晶化的技术路线,加强复相化的研究,重视材料的使用性能的开发和纳米析出的利用,努力开发与环境协调、友好的新一代钢铁材料,促进钢铁工业和国民经济的可持续发展。

新一代TMCP的实践和工业应用举例

介绍以超快速冷却为核心的新一代TMCP技术在钢材生产中的广泛应用和由此而导致的钢材性能的提升。这些应用包括棒线材控轧控冷技术突破和应用、轴承钢的轧后超快速冷却控制碳化物分布、利用超快速冷却技术进行热轧带钢组织复相化控制,以及热轧带钢轧机实施超快速冷却装置的改造和中厚板轧机实施超快速压力喷射式冷却+ACC的新式冷却系统的建立。

Characterization of SiC nanowires prepared on C/C composite without catalyst by CVD

SiC nanowires were prepared on C/C composite surface without catalyst by chemical vapor deposition（CVD） using CH3 SiCl3 as precursor.SEM images of the CVD-product reveal that some long nanowires have grown to tens of micrometers with some gathered as a ball.Some short nanowires agglomerate like chestnut shell with many thorns accompanied by some deposited nano-particles.XRD,Raman-spectrum and FTIR patterns indicate that the product is a typical β-SiC.TEM images show that the nanowires have a wide diameter range from 10 to 100 nm,and some thin nanowires are bonded to the thick one by amorphous CVD-SiC.A SiC branch generates from an amorphous section of a thick one with an angle of 70° between them,which is consistent with the [111] axis stacking angle of the crystal.SAED and fast Fourier transform（FFT） patterns reveal that the nanowires can grow along with different axes,and the bamboo-nodes section is full of stacking faults and twin crystal.The twisted SiC lattice planes reveal that the screw dislocation growth is the main mechanism for the CVD-SiC nanowires.

Preparation, characterization, and catalytic performance of high efficient CeO_2-MnO_x-Al_2O_3 catalysts for NO elimination

A series of CeO2‐MnOx‐Al2O3 mixed oxide catalysts （Ce：Mn：Al mole ratio=6：4：x, x=0.25, 0.5, 1, 2） were prepared by a simple one‐step inverse co‐precipitation method to investigate the influence of the incorporation of Al3＋ into CeO2‐MnOx mixed oxides. CeO2‐MnOx, CeO2‐Al2O3, and MnOx‐Al2O3 mixed oxides, and CeO2 were prepared by the same method for comparison. The samples were characterized by XRD, Raman, N2 physisorption, H2‐TPR, XPS, and in situ DRIFTS. The catalytic re‐duction of NO by CO was chosen as a model reaction to evaluate the catalytic performance. The incorporation of a small amount of Al3＋into CeO2‐MnOx mixed oxides resulted in a decrease of crys‐tallite size, with the increase of the BET specific surface area and pore volume, as well as the in‐crease of Ce3＋and Mn4＋. The former benefits good contact between catalyst and reactants, and the latter promotes the adsorption of CO and the desorption, conversion and dissociation of adsorbed NO. All these enhanced the catalytic performance for the NO＋CO model reaction. A reaction mecha‐nism was proposed to explain the excellent catalytic performance of CeO2‐MnOx‐Al2O3 catalysts for NO reduction by CO.

Bending properties and fracture mechanism of C/C composites with high density preform

C/C composites with banded structure pyrocarbon were fabricated by fast chemical vapor infiltration（CVI）,with C3H6 as carbon source,N2 as carrier gas,and three-dimensional（3D） 12K PAN-based carbon fabric with high density of 0.94 g/cm3 as preform.Experimental results indicated that the fracture characteristics of C/C composites were closely related to the frequency of high-temperature treatment（HTT） at the break of CVI process.According to the load？displacement curves,C/C composites showed a pseudoplastic fracture after twice of HTT.After three times of HTT,load？displacement curves tended to be stable with a decreasing bending strength at 177.5 MPa.Delamination failure and intrastratal fiber fracture were observed at the cross-section of C/C composites by scanning electronic microscope.Because the content of pyrocarbon and fibers has a different distribution in layers,the C/C composites show different fracture characteristics at various regions,which leads to good toughness and bending strength.

Preparation and characterization of diamond film on Cu substrate using Cu-diamond composite interlayer

Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition （HFCVD）. The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with （111） apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.

Preparation and mechanical properties of carbon/carbon composites with high textured pyrolytic carbon matrix

Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon （C/C） composites was 1.89 g/cm3 after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.

Heterogeneous catalytic activation of peroxymonosulfate for efficient degradation of organic pollutants by magnetic Cu^0/Fe_3O_4 submicron composites

Magnetic Cu^0/Fe3O4 submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate（PMS） and the degradation of organic pollutants.The as-prepared magnetic Cu^0/Fe3O4 submicron composites were composed of Cu^0 and Fe3O4 crystals and had an average size of approximately 220 nm.The Cu^0/Fe3O4 composites could efficiently catalyze the activation of PMS to generate singlet oxygen,and thus induced the rapid degradation of rhodamine B,methylene blue,orange Ⅱ,phenol and 4-chlorophenol.The use of0.1 g/L of the Cu^0/Fe3O4 composites induced the complete removal of rhodamine B（20 μmol/L） in15 min,methylene blue（20 μmol/L） in 5 min,orange Ⅱ（20 μmol/L） in 10 min,phenol（0.1mmol/L） in 30 min and 4-chlorophenol（0.1 mmol/L） in 15 min with an initial pH value of 7.0 and a PMS concentration of 0.5 mmol/L.The total organic carbon（TOC） removal higher than 85%for all of these five pollutants was obtained in 30 min when the PMS concentration was 2.5 mmol/L.The rate of degradation was considerably higher than that obtained with Cu^0 or Fe3O4 particles alone.The enhanced catalytic activity of the Cu^0/Fe3O4 composites in the activation of PMS was attributed to the synergistic effect of the Cu^0 and Fe3O4 crystals in the composites.Singlet oxygen was identified as the primary reactive oxygen species responsible for pollutant degradation by electron spin resonance and radical quenching experiments.A possible mechanism for the activation of PMS by Cu^0/Fe3O4 composites is proposed as electron transfer from the organic pollutants to PMS induces the activation of PMS to generate ^1O2,which induces the degradation of the organic pollutants.As a magnetic catalyst,the Cu^0/Fe3O4 composites were easily recovered by magnetic separation,and exhibited excellent stability over five successive degradation cycles.The present study provides a facile and green heterogeneous catalysis method for the oxidative removal of organic pollutants.

In-situ homogeneous synthesis of carbon nanotubes on aluminum matrix and properties of their composites

Using nickel catalyst supported on aluminum powders, carbon nanotubes （CNTs） were successfully synthesized in aluminum powders by in-situ chemical vapor deposition at 650 ℃. Structural characterization revealed that the as-grown CNTs possessed higher graphitization degree and straight graphite shell. By this approach, more homogeneous dispersion of CNTs in aluminum powders was achieved compared with the traditional mechanical mixture methods. Using the in-situ synthesized CNTs/Al composite powders and powder metallurgy process, CNTs/Al bulk composites were prepared. Performance testing showed that the mechanical properties and dimensional stability of the composites were improved obviously, which was attributed to the superior dispersion of CNTs in aluminum matrix and the strong interfacial bonding between CNTs and matrix.

Aromatic Compounds Production from Sorbitol by Aqueous Catalytic Reforming

The rules on regulating aromatic compounds production was investigated by aqueous cat- alytic reforming of sorbitol. It was found that aromatics, ketones, furans, organic acids were main compounds in organic phase. The obvious effect of metal content showed that the highest carbon selectivity of aromatics was 34.36% when 3wt% Ni content was loaded on HZSM-5 zeolite modified by MCM-41. However, it was decreased only to 4.82% when Ni content was improved to 20wt%. Meanwhile, different reaction parameters also displayed important impacts on carbon selectivity. It was improved with the increase of temperature, while it was decreased as liquid hourly space velocity and hydrogen pressure was increased. The results showed that appropriate higher temperature, longer contact time and lower hy- drogen pressure were in favor of aromatics information, which suggested a feasible process to solve energy crisis.

Evolution of COP9 Signalosome and Proteasome Lid Complex

The COP9 signalosome and the regulatory lid of the 26S proteasome are both eight-subunit protein complexes which are present in most eukaryotes. There is a one-to-one relationship between the corresponding subunits of the two protein complexes in terms of their size and amino acid sequences. Eight groups of subunits from the COP9 signalosome and the proteasome lid complex of different organisms are collected from all the databases at the NCBI website. The corresponding subunits of COP9 signalosome and proteasome lid complex share at least 12% amino acid identity and some conserved regions, and the conserved sites spread evenly over the entire length of the subunits, suggesting that the two complexes have a common evolutionary ancestor. Phylogenetic analyses based on the amino acid sequences of the corresponding subunits of two protein complexes indicate that every tree consists of two clades. The subunits from one of the two protein complexes of different organisms are grouped into one of the two clades respectively. The sequences of single-cell organisms are always the basal groups to that of multi-cell animal and plant species. These results imply that the duplication/divergence events of COP9 signalosome and regulatory lid of the proteasome genes have occurred before the divergence of single-cell and multi-cell eukaryotes, and the genes of the two complexes are independently evolved. The analyses of dN/dS correlation show significant Pearson's correlations between 21 and 15 pairs of subunit-encoding sequences within the COP9 signalosome and the proteasome lid complex respectively, suggesting that those subunits pairs might have related functions and interacted with one another, and resulted in co-evolution.

Fe添加对自蔓延离心熔铸TiC–TiB--_2复相陶瓷结构和性能的影响

在(Ti+B_4C)燃烧体系中引入Fe添加剂,釆用自蔓延离心熔铸技术制备出含有不同质量分数Fe的TiC–TiB_2复相陶瓷。结果表明:TiC–TiB_2凝固陶瓷以大量细小TiB_2片晶、不规则TiC晶粒及分布于晶间的断续网状Fe黏结相组成。适量Fe的添加,可以加快反应体系组元之间的扩散,促进复相陶瓷内部气体排出与成分均匀化,促使陶瓷致密化、基体晶粒细化、组织均匀性改善,同时作为韧性相,在裂纹扩展过程中又可诱发延性相增韧机制,提高陶瓷的致密度与力学性能,但是过多引入Fe添加剂,将促使TiB_2初生相异常长大,劣化陶瓷组织均质性。

TiB_(2)对无压烧结B4C–TiB_(2)复相陶瓷结构和性能的影响

以碳化硼(B_(4)C)、二硼化钛(TiB_(2))、碳化钛(TiC)为原料,采用无压烧结法在2 130℃制备了含20%(质量分数)和30%TiB_(2)的B_(4)C基复相陶瓷,分析所制样品的密度、硬度、弯曲强度和断裂韧性。结果表明:在2 130℃,直接加入30%的TiB_(2)亚微米颗粒,复相陶瓷的抗弯强度和断裂韧性分别达到277.6 MPa和5.38 MPa·m^(1/2)。陶瓷中颗粒拔出和裂纹微桥接对复相陶瓷增韧作用显著。B_(4)C–TiB_(2)复相陶瓷的增韧机理主要是由于TiB_(2)与B_(4)C热膨胀系数不匹配产生的残余应力导致的微裂纹增韧和裂纹偏转增韧。