自蔓延高温合成新型碳化钛磨料

采用自蔓延高温合成技术制备碳化钛磨料。考察了合成过程中钛粉粒度、C与Ti摩尔比率、稀释剂添加量、初始样品密度对燃烧温度、燃烧速率及产物化学组成的影响,测试和比较和碳化钛和其他磨料的研磨性能,并通过SEM分析了碳化钛、金刚石颗粒及相应被磨工件的表面形貌。结果表明：碳化钛的研磨能力可与人造金刚石相媲美,大大超过氧化铝、碳化棚和碳化硅。而碳化钛的高研磨能力是由颗粒的强切削力所致,人造金刚石则由颗粒的高硬度所致。     

B掺杂辅助自蔓延高温合成AlN晶须材料研究

采用Al粉、B粉和一种CNx前驱物粉体为原料,通过自蔓延高温合成技术,制备了AlN材料.研究结果表明,B的掺杂促进原料自蔓延反应合成AlN.当原料中Al含量较高(Al∶B∶CNx=2∶1∶1)时,产物中Al为主相,AlN含量较少;当原料配比(Al∶B∶CNx=1∶1∶1)合适时,生成B固溶的AlN材料.产物中AlN相存在两种形貌,一种是片状AlN晶粒,另一种为AlN晶须.     

机械合金化制备碳化钛纳米粉体的合成机理研究

本研究中,以金属钛（Ti）粉与环己烷为原料,利用机械合金化制备了碳化钛（TiC）纳米粉体。利用X射线衍射并结合Rietveld精修对球磨产物进行定性与定量分析;借助透射电子显微镜对产物进行形貌与元素以及结晶性进行分析;对球磨过程中TiC的合成机理进行了研究。结果表明,球磨产物中主相为TiC,另有少量残留的氢化钛（TiH2）与Ti;所制备TiC粉体易于团聚、颗粒度均匀、结晶性良好;TiC合成机理属于扩散型机制。     

自蔓延燃烧合成工艺因素对钛镍黄颜料呈色的影响

以金属钛、TiO2、NiO、Sb2O3为主要原料，用自蔓延燃烧法合成了钛镍黄颜料；采用XRD、DTA及CIE色度分析手段探讨了自蔓延法合成钛镍黄颜料中原料配比和保温时间对颜料呈色效果的影响。     

自蔓延高温合成软磁Ni-Zn铁氧体的研究

采用自蔓延高温合成法合成了 Ni0 .4 Zn0 .6 Fe2 O4 ,研究了反应温度、燃烧波速率与放热系数 k值之间的关系。并通过 XRD、SEM、VSM等测试手段对产物的形貌、物相、结构及性能进行了分析 ,结果表明当放热系数 k=0 .6时 ,反应比较完全 ,合成产物颗粒大小均匀 ,产物具有较高的比饱和磁化强度和低的矫顽力     

类钙钛矿型La_(1-x)Sr_xMnO_3超磁电阻材料的自蔓延燃烧合成研究

采用自蔓延燃烧合成法成功合成了具有类钙钛矿型结构的复杂金属氧化物材料La_(1-x)Sr_xMnO_3。结果表明,通过控制KMnO4掺量可以有效地控制燃烧合成过程中的反应温度、速度,并影响反应的进行和产物相的形成。在La1-x SrxMnO3超磁电阻材料的燃烧合成过程中,液相Mn的产生能影响反应温度和燃烧波传播速度。对合成材料的性能表征,发现自蔓延高温合成的La_(1-x)Sr_xMnO_3在210 K附近会出现金属-绝缘体转变,一定温度范围内材料的磁电阻绝对值可达到13%。     

燃烧合成一维纳米结构AlN及其生长机理研究

以铝粉(Al)和NH4F为主要原料,Nb为添加剂,在N2压力小于0.5 MPa的条件下采用高温自蔓延燃烧法(SHS)合成了一维纳米结构的AlN粉体,并通过差热分析(TG/DSC)分析了Al-N2 体系的热力学机理,运用X-射线衍射仪、场发射扫描电子显微镜(SEM)分析了所合成一维纳米结构AlN的物相组成和显微结构.结果表明,当Al∶NH4F为4∶1(wt%)时,在添加剂Nb的作用下,合成的产物主要为一维纳米结构六方长针状AlN,该粉体纯度高、晶体结构完整,且沿(100)存在明显择优取向;所合成的一维纳米结构AlN的生长机理属于SLS生长机理.     

TiC/Ti-Al基复合材料的燃烧合成

为了改善Ti-Al金属间化合物的脆性,利用SHS/PHIP工艺制备了TiC/Ti-Al基复合材料.理论分析表明,绝热温度随C质量分数的增加而呈升高趋势,当体系中碳的质量分数≥2%时,该体系能完成自蔓延过程.采用电子扫描显微镜,X射线衍射仪对合成产物进行了分析.结果表明,合成产物中除存在基体相Ti3Al和TiAl和增强相TiC外,还存在许多三元相Ti3AlC和Ti2AlC相;随着Al质量分数的增加,增强相的形貌由颗粒状逐渐变成棒状或片状;复合材料的硬度和压缩强度随C质量分数的增加逐渐增加,但密度及相对密度随C质量分数的增加呈先增加后降低的趋势.当C的质量分数达到4%时,其实际密度和相对密度均达到最大.     

原材料对原位合成强化相结晶状态的影响

钛合金表面耐磨性能差限制了电厂重要成品部件的寿命。采用激光熔覆方法,研究了不同原料状态和稀土添加对原位合成复合TiB/TiN钛基涂层强化相粒度以及分布均匀性的影响。采用X射线衍射分析(XRD)、扫描电子显微分析(SEM)和高分辨投射分析(TEM)技术等方法研究了强化相组织形貌,得出以下结论:分别采用h-BN和纯硼酸、尿素为原料形成的Core-shell结构为原料,涂层中均原位合成TiB/TiN强化颗粒,采用非晶态BN有利于获得细小强化相组织,但强化相含量相对较少;添加CeO2有利于强化相晶粒细化以及均匀分布。     

LiFePO4表面碳包覆方法中碳源的碳化研究

采用热重分析(TG-DTA)和扫描电子显微镜(SEM)研究了磷酸铁锂碳包覆工艺中不同碳源的碳化过程以及碳化产物的形貌特征.实验选取了抗坏血酸、蔗糖、葡萄糖、醋酸纤维、环糊精,以及酚醛树脂等几种有机物作为碳源,根据测试结果结合不同类型碳源的物理、化学性质,分析了不同类型碳源的碳化过程及其碳化产物的形成.围绕磷酸铁锂的电极过程的需要,对碳源的选择作了分析讨论.     

Al-Ti-C grain refiner made by ultrasonic levitation

An electrostrictive uniaxial ultrasonic levitation reaction system was designed to perform TiC synthesis reaction by suspending graphite powder in Al-3Ti melt and an Al-3Ti-0.15C grain refiner alloy was obtained. The results show that sound pressure node in which graphite suspends is formed in the melt between radiation block and reflecting board by ultrasonic and TiAl3 particles congregate around C powder. Meanwhile, due to ultrasonic cavitation, dissolved TiAl3 provides better surface condition for the synthesis reaction of TiC. The reaction route is that C and dissolved Ti react to form TiC. Ultrasonic cavitation has a thermal activation effect on TiC particles and Al-3Ti-0.15C refiner has excellent microstructural refining effect on α-Al.     

石墨配比对钨极氩弧熔敷层TiC增强相含量及分布形态的影响

利用钨极氩弧熔敷预涂在碳钢表面的钛铁和石墨粉末能够在碳钢表面获得性能优异的TiC增强涂层.预涂粉末Ti、C元素配比及含量对增强相的数量、形态和分布方式有重要影响：一方面,随着预涂粉末中含碳量的增加,熔敷层中Fe2Ti有害相降低,但出现了极少量的石墨相;另一方面,熔敷层中原位合成TiC增强相的含量增加,颗粒尺寸也随之增加,TiC颗粒的树枝状分布形态也由细枝状向粗枝状转化.     

Wetting behavior of graphite and CFC composites by Cu-Ti compacts

The wetting behavior of Cu-Ti powder compacts with 22 wt %Ti and 50 wt %Ti on carbon materials, including graphite and carbon fiber reinforced carbon composites(CFC), has been investigated in a vacuum using the sessile drop method. The equilibrium contact angles of Cu-22Ti(containing 22 wt%Ti) on the graphite and the CFC substrates at 1 253 K are 32 o and 26 o, respectively, whereas the equilibrium contact angle of 9° is obtained for Cu-50Ti(containing 50 wt%Ti) on both the graphite and the CFC substrates at 1 303 K.Microstructural analysis of the wetting samples shows that a thin TiC reaction layer is developed at the interfacial area and Ti-Cu intermetallic compounds are formed over the reaction layer. The investigation on the spreading kinetics of Cu-Ti compacts on carbon materials substrates at fixed temperatures reveals that the spreading is controlled by the interfacial reactions in the first stage and then by the diffusion of the active Ti from the drop bulk to the triple line in the later stage. The spreading is promoted by the intense reaction at higher Ti concentrations.     

Precipitation characteristic of high strength steels microalloyed with titanium produced by compact strip production

Transmission electron microscopy (TEM) and physics-chemical phase analysis were employed to investigate the precipitates in high strength steels microalloyed with Ti produced by compact strip production (CSP). It was seen that precipitates in Ti microalloyed steels mainly included TiN, Ti4C2S2, and TiC. The size of TiN particles varied from 50 to 500 nm, and they could precipitate during or before soaking. The Ti4C2S2 with the size of 40-100 nm might precipitate before rolling, and the TiC particles with the size of 5-50 nm precipitated heterogeneously. High Ti content would lead to the presence of bigger TiC particles that precipitated in austenite, and by contrast, TiC particles that precipitated in ferrite and the transformation of austenite to ferrite was smaller. They were less than 30 nm and mainly responsible for precipitate strengthening. It should be noted that the TiC particles in higher Ti content were generally smaller than those in the steel with a lower Ti content.     

Preparation of porous silicon carbide by combustion synthesis

Porous silicon carbide ceramics were prepared by combustion synthesis technique. SiC/TiC composite was gained by combustion reaction of Si, C and Ti. Thermodynamics analysis of Si-C-Ti system indicates that the content of TiC in products should be larger than 30%. The experimental results show that the content of Ti C should be larger than 25% to achieve a complete combustion reaction. The X-ray diffractometry results show that the final products with a relative density of 45%-64% are composed of a-SiC,β-SiC, TiC and a small quantity of Si. The images of scanning electron microscopy show that the structures of grain in SiC based porous ceramics consist of particles with a few microns in size.     

Ag-Cu-Ti钎料在金刚石表面的润湿状况

针对金刚石的钎焊问题,利用扫描电镜和电子探针分析、Ｘ射线能谱分析、Ｘ射线结构分析等方法,对Ａｇ－Ｃｕ－Ｔｉ钎料在金刚石表面的润湿状况进行了试验研究。,结果,含Ｔｉ量对钎料的湿着状况有一定的影响界央间Ｃ,Ｔｉ元素的扩散及ＴｉＣ的形成有助于改善钎料的润湿状况。     

Kinetics of Combustion Synthesis in Ti-C-3Ni-Al System

The Kinetics and mechanisms of the combustion reaction in theTi-C-3Ni-Al system were studied. Samples were prepared by igniting compacts of elemental Ti, C, Ni and Al powders with a heating tungsten coil under an inert argon atmosphere. The activation energies of Ti+C+50wt%(3Ni+Al)→TiC+50%Ni3Al and Ti+C+80wt%(3Ni+Al) →TiC+80%Ni3Al exothermic reactions were determined by measuring the combustion wave velocity and the combustion temperature, which are 129kJ.mol-1 and 79kJ*mol-1, respectively. The mechanism of formation of products for Ti-C-3Ni-Al system was found:metal phases (Ti-3Ni-Al) are melted in combustion process,and carbon dissolves into the liquid metal and TiC is subsequently precipitated out of solution, and Ni3Al is crystallized during the cooling process. The mechanism is fairly similar with that of Ti+C→TiC and Ti+C+Ni→TiC+Ni. There are two reactions (Ti+C→TiC, 3Ni+Al→Ni3Al) in the Ti+C+3Ni+Al system, and the wave velocity is mainly controlled by the velocity of Ti + C→TiC, but the velosity of 3Ni+Al→Ni3Al may play a significant role when Ni3Al contents are higher than 70wt%.     

As-cast microstructures of Ti-11 Al- xC alloys

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基于FPGA的四翼超混沌系统同步及其保密视频通信

对广义增广Lü四翼超混沌系统进行分析,采用非线性控制同步方法实现该超混沌系统的自同步，理论分析所设计的非线性同步控制器的正确性和有效性。对该超混沌系统及其非线性控制同步进行FPGA硬件电路设计与实现,硬件试验结果和数值仿真结果及理论分析结果一致。提出一种基于该超混沌系统非线性同步的混沌掩盖保密视频通信方案,并对该保密通讯方案进行field programmable gate array硬件试验,试验结果表明:该保密通信方案有效、可行,并具有良好的保密性。     

Synthesis of Ti3SiC2/TiB2 Composite by In-situ Hot Pressing (HP) Method

Ti3SiC2/TiB2 composite was successfully obtained by hot pressing Ti/TiC/Si/B4C power mixtures.Volume fraction of TiB2 in Ti3SiC2/TiB2 composite can not exceed 10%.Incorporation of excessive TiB2 will affect the reactions process.TiC and Ti5Si3 were two important intermediate phases during the whole reactions.The microstructure characteristics of the Ti3SiC2/TiB2 composites were analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The experimental results show that the grains of Ti3SiC2/TiB2 composite are structured in a layered form,and the formation of TiB2 particles as reinforcements with elongated or equiaxed shape distributes in Ti3SiC2 matrix.