甲烷体积分数对纳米金刚石薄膜形貌的影响

目的研究不同甲烷体积分数对纳米金刚石(NCD)薄膜生长的影响,实现较小晶粒尺寸、高平整度的NCD薄膜的制备。方法采用微波等离子体增强化学气相沉积的方法制备NCD薄膜,以CH4/H2为气源,在生长阶段控制其他条件不变的前提下,探讨不同甲烷体积分数对NCD晶粒尺寸、表面形貌以及表面粗糙度的影响。采用SEM、XRD等观测NCD薄膜的表面形貌和晶粒尺寸大小,并利用Raman对NCD薄膜的不同散射峰进行分析。结果随着甲烷体积分数的增加,薄膜晶粒尺寸有减小的趋势。甲烷体积分数较低时,晶形比较完整,但致密度较小;甲烷体积分数较高时,晶形杂乱无章,但致密度较好。当甲烷体积分数为9%时NCD薄膜平均粒径达到最小,为21.3 nm,表面粗糙度较好,但非晶金刚石成分开始大量生成,NCD薄膜质量开始变差;当甲烷体积分数为8%时其形貌最好,且此时最小表面粗糙度小于20 nm。通过Raman分析可知NCD薄膜中出现了硅峰和石墨烯特征峰。结论甲烷体积分数对NCD薄膜形貌有较大影响,甲烷体积分数为8%时是表面平整度由较差变好再逐渐变差的分界点,且平均晶粒尺寸为23.6 nm,薄膜表面具有较好的平整度。     

碳化硅衬底沉积高取向金刚石薄膜

采用直流辉光放电等离子体设备在单晶碳化硅表面沉积高晶取向金刚石薄膜,研究了预处理方法、基片温度以及甲烷浓度(甲烷与氢气的体积比)对金刚石薄膜晶粒取向的影响。用SEM、Raman等测试方法对金刚石薄膜进行表征。结果表明:研磨处理可以提高金刚石形核密度,高的形核密度有利于金刚石薄膜的沉积;过高或过低的基片温度会使得金刚石薄膜表现出(111)面生长的趋势;高甲烷浓度和低甲烷浓度也会使得金刚石薄膜晶粒取向发生改变。最终采用850℃以及5%甲烷浓度这一沉积参数进行金刚石薄膜的沉积,制备出了取向度非常好的(100)面金刚石薄膜。     

MPCVD快速制备(100)面金刚石薄膜

利用实验室自主研发的10 kW微波等离子体装置,在直径为75 mm的(100)硅片上快速沉积高质量(100)面金刚石薄膜。实验中,甲烷浓度由1%提高至5%,金刚石薄膜的沉积速率由1μm/h增至8.2μm/h。随着金刚石薄膜生长速率的增加,薄膜质量下降,晶型杂乱,非金刚石相含量增加。在气源中加入氧气以提高高速生长下金刚石薄膜的质量。不同氧气浓度对金刚石薄膜的半高宽(Full Width at Half Maximum,FWHM)有较大影响:氧气浓度为0.1%～0.5%时,金刚石薄膜的FWHM随着氧气浓度的增加而减小;0.6%～1.2%时,薄膜FWHM值随着氧气浓度的增加而增大;浓度大于1.2%时,FWHM值保持不变。在H2流量为300 cm3/min,CH4浓度为5%,O2浓度为0.5%的条件下,制备出了(100)面完整,晶型完整,有台阶生长状的金刚石薄膜。     

低浓度氮气对MPCVD法制备金刚石膜的影响

利用微波等离子体化学气相沉积(MPCVD)法,在CH4/H2的混合反应气源中加入N2进行了金刚石膜的沉积实验,详细研究了N2浓度对金刚石膜生长的影响规律。使用扫描电子显微镜、激光拉曼光谱仪和X射线衍射仪等设备,表征了金刚石薄膜的表面形貌、相组成及晶面取向。实验结果表明:随着N2体积分数的增加(由0%增加到6%),薄膜中的非金刚石相含量逐渐增大,金刚石晶粒尺寸逐渐减小,晶面取向也由较大的晶面(111)转变成较小的晶面(100);当N2体积分数为4%时,沉积的金刚石膜表面为"菜花"状结构;低体积分数(2%)的N2有利于获得高度取向(100)的金刚石膜。     

硼掺杂金刚石薄膜的制备和性能研究

通过热丝化学气相沉积法,在硅基上沉积硼掺杂金刚石薄膜,研究硼源流量对硼掺杂金刚石薄膜的导电性能、晶粒尺寸、晶面方向及残余应力等的影响。结果表明:随硼流量增加,金刚石薄膜电阻迅速降低;超过一定流量后,薄膜的缺陷和杂质增多,阻碍了电阻的进一步下降。硼流量在0~25 mL/min内逐渐升高时,金刚石薄膜平均晶粒尺寸从3.5 μm增长到8.3 μm,硼元素促进了（111）晶面的生长;硼流量继续增大到35 mL/min时,对（111）晶面的促进作用减弱,晶粒尺寸减小且晶粒表面缺陷增多而失去完整性。X射线衍射分析表明:随硼流量增加,金刚石薄膜（111）晶面和（110）晶面的衍射峰面积比,呈先增加后减少的趋势,在硼流量为20 mL/min时达到最大值;且硼掺杂金刚石薄膜残余应力为压应力。在硼源流量小于10 mL/min时,应力随流量的增加而减小;当硼流量大于30 mL/min时,应力随流量的增加而增大。      

氮气对DC-PCVD法制备金刚石薄膜影响的研究

采用直流热阴极等离子体化学气相沉积方法,用甲烷、氢气、氮气的混合气体在Mo基底上成功制备了金刚石薄膜.分别采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、拉曼光谱仪(Raman)对不同流量氮气氛下生长金刚石薄膜的形貌、取向、质量进行了表征.结果表明:适量氮气的加入,不仅可以促进金刚石薄膜的生长速率,还可以促进金刚...     

沉积参数对Mo-Re合金基体上沉积金刚石薄膜的影响

采用热丝化学气相沉积法(HFCVD),以甲烷和氢气为反应气体,在综合性能良好的Mo-40%Re(摩尔分数)合金基体上沉积金刚石薄膜.采用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)和显微激光拉曼光谱仪(Raman)分别对金刚石薄膜相组成、表面形貌、晶粒大小和质量等进行检测分析,研究CVD沉积参数,如基体温度(θs)、碳源浓度(R,Cn4的体积分数)和沉积压强(p),对金刚石形核、生长和金刚石成膜的影响.结果表明在合适的基体预处理条件下,当θs=750℃,R=-3%,p=3.5kPa时,薄膜平均线生长速率高达1μm/h,得到的金刚石膜完整致密,晶粒大小均匀,纯度较高,具有明显的(111)织构.     

直流溅射沉积CrN薄膜组织结构与摩擦性能分析（英文）

采用直流反应溅射在304不锈钢表面沉积CrN薄膜。利用X射线衍射仪(XRD),扫描电子显微镜(SEM),原子力显微镜(AFM),显微硬度计,磨损试验机与三维轮廓仪等表征氮气流量对CrN薄膜组织结构与摩擦性能的影响。结果表明,随着氮气流量的增加,CrN(200)晶面呈择优取向,薄膜的沉积速率随着氮气流量的增加逐渐降低。另外,薄膜的表面粗糙度随着氮气流量的增加呈先降低后增加的趋势。随着氮气流量从15 cm~3/min增加至30 cm~3/min时,薄膜的显微硬度HV先从5273 MPa增加至10422 MPa,当氮气流量再增加至35 cm~3/min时,薄膜的显微硬度却降低至9180 MPa。磨损试验表明,当氮气流量为30 cm~3/min时薄膜具有最小的摩擦系数0.93和磨损率2.02×10-15 m~3·(N·m)~(-1),显示最佳的磨损性能。     

磁控溅射基片负偏压对Ti/TiN复合纳米薄膜择优取向的影响

采用中频反应磁控溅射技术,以高纯Ti(99.99%)为靶材,以高纯氮气(99.99%)为反应气体,在铝合金基片上沉积Ti/TiN复合纳米膜层。通过XRD、SEM、EDS等分析Ti/TiN复合纳米膜层微观组织和物相结构,研究基片负偏压对Ti/TiN复合纳米薄膜择优取向生长的影响。研究表明,将片加上-150 V负偏压时,Ti/TiN薄膜优先沿(111)面生长;将基片加上-200 V负偏压时,Ti/TiN薄膜优先沿(220)面生长;将基片加上-350 V负偏压时,Ti/TiN薄膜优先沿(200)面生长。继续增大基片负偏压时,由于薄膜中Ar离子浓度大幅增长,高能离子长时间轰击破坏晶粒取向性,使薄膜呈无择优取向。     

磁过滤等离子体制备TiN薄膜中沉积条件对薄膜织构的影响

在室温条件下,利用自行设计的平面"S"形磁过滤等离子体设备,在(111)面单晶硅上制备TiN薄膜,通过改变基底偏压和反应气体成分,即通过改变氮气和氩气的气体流量来改变沉积离子的能量和密度,从离子轰击的角度研究了沉积条件对TiN薄膜织构的影响.对薄膜的表面形貌进行观察,用(θ～2θ)和1.5°掠入射2种X射线衍射方法对薄膜晶体结构和晶面取向进行了分析,对薄膜进行了电子衍射研究.结果显示磁过滤等离子制备的TiN薄膜表面平整光滑,颗粒尺寸为20～70 nm,且基底偏压和氩气流量的增大促使薄膜发生(111)面的择优取向,且(111)晶面与膜表面平行,而在高氩气流量的情况下,(200)和(220)面在薄膜平面也发生了定向排列.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.