介电泳辅助水溶解抛光过程中微水滴分布的仿真与实验研究

目的 为解决KDP晶体无损表面的制造难题,进一步提升水溶解抛光方法的抛光质量和效率,研究介电泳效应对水溶解抛光液的影响.方法 提出一种介电泳辅助水溶解的抛光方法,最终获得超光滑表面,采用有限元软件模拟极化后微水滴的运动行为,并搭建验证性平台观测介电泳力作用下抛光液的吸附行为,验证抛光原理.之后数值模拟不同的电极形状对微水滴受到介电泳力的影响规律,优化得到最优电极形状参数.最后搭建试验平台,验证介电泳对水溶解抛光效率和质量的提升效果.结果 微水滴会在介电泳力作用下发生形变,并聚集在晶体表面附近,从而提高抛光过程中参与溶解的微水滴数量,加快溶解去除速率.同时,上电极也会对抛光液产生"吸附"作用,延长抛光液在晶体表面的作用时间,减小抛光液甩出率,进一步提高抛光效率.双螺旋结构电极具有最大的电场梯度,能够使水滴受到最大的介电泳力而向晶体表面聚集.经过20 min抛光后,采用传统水溶解抛光的KDP晶体表面粗糙度Ra由抛光前的590 nm降低至1.637 nm,而采用介电泳辅助水溶解抛光的KDP晶体,表面粗糙度降至1.365 nm,表面质量更高.与传统水溶解抛光相比,介电泳辅助水溶解抛光效率提升24％,同时能够更快地获得光滑表面.结论 在介电泳效应的辅助作用下,KDP晶体水溶解抛光质量和效率均得到了提升.     

介电泳抛光方法及其电极形状的实验研究

目的验证介电泳抛光方法的有效性,研究电极形状对介电泳抛光方法均匀性、抛光效率和去除率的影响。方法选取直径76.2 mm的单晶硅片为实验对象,进行传统化学机械抛光(CMP)实验和使用4种电极形状的介电泳抛光实验,每隔30 min测量硅片不同直径上的表面粗糙度以及硅片的质量,然后对测量的数据进行处理和分析。结果与传统CMP方法比较,使用介电泳抛光方法抛光的硅片,不同直径上的表面粗糙度相差小,粗糙度下降速度快,使用直径60 mm圆电极形状介电泳抛光时相差最小,粗糙度下降最快。介电泳抛光方法去除率最低能提高11.0%,最高能提高19.5%,最高时所用电极形状为内径70 mm、外径90 mm的圆环。结论介电泳抛光方法抛光均匀性、效率和去除率均优于传统CMP方法。     

磁流变微结构动压平面抛光试验研究

为提高集群磁流变平面抛光效率,在抛光盘表面增加微结构,以增强加工过程中的流体动压作用。使用平面抛光盘和表面加工有孔洞、V形槽、U形槽、矩形槽等不同微结构的抛光盘进行抛光试验及抛光压力特性试验,研究了加工间隙和工件转速对加工效果的影响。结果表明:抛光盘表面微结构对工件材料去除率影响较大,不同微结构盘材料去除率从大到小顺序为V形盘>U形盘>平面盘>孔洞盘>矩形盘,其中V形盘的材料去除率比平面盘高25%以上;所有抛光盘均能获得纳米级（R_a在8 nm以内）表面。当加工间隙为0.9~1.0 mm、工件转速为550 r/min时,加工效果较好。      

磁流变抛光技术的工艺试验

本文研究了利用自行配制的水基磁流变抛光液和抛光样机,进行了以抛光去除效率和表面粗糙度为考核指标的工艺实验,试验中所用工件为直径12mm的BK7玻璃零件,其初始表面粗糙度的均方根值为RMS1．41nm,经抛光后得到理想的表面粗糙度的均方根值为RMS0．61nm的玻璃工件,结果表明：随着磁流变抛光磁场强度的增加,抛光去除效率逐渐提高,但表面粗糙度的值随之降低;抛光盘转速的提高能促进抛光效率的提高,降低表面粗糙度值;抛光盘与工件间的间隙的减小有利于提高抛光效率但同时使表面粗糙度变差。     

CP4研抛晶片时非均匀性和材料去除速率研究

建立了CP4研抛晶片时,晶片上任一点相对于研抛盘的运动方程。通过对其运动轨迹的分析,建立了工件材料研抛非均匀系数的函数模型和相对研抛材料去除速率的函数模型。运用Matlab软件,模拟分析了各个参数变化对研抛非均匀系数和相对研抛效率的影响。结果表明:对材料去除效率影响最大的参数是偏心距e的大小,其次是从动系数λ1;对晶片非均匀性影响最大参数是从动系数λ1,其次是偏心距e;当λ1=1,λ20.3,e取工艺允许的最大值时,工件研抛的均匀性最好。     

基于介电泳微流控技术的碳纳米管分离

介电泳微流控分离碳纳米管是利用在外加特定频率非均匀交变电场的流动介电液中,金属型和半导体型碳纳米管由于自身电学性能不同受到不同介电泳力,进而向不同方向运动实现分离。建立了分离碳纳米管的介电泳数学模型和微流控分离通道及电极几何模型,并对分离过程进行了仿真研究。依据碳纳米管及介电液的电导率和介电常数,确定分离所用的电场频率为1010Hz,由此获得了分离通道内的电场、流场分布和碳纳米管分离运动轨迹。通过研究入口流速和电压变化对分离结果的影响,得出了使碳纳米管成功分离的入口流速和电压的合理参数组合,可指导碳纳米管实际分离过程以缩短分离时间,有利于推进基于单一电学特性碳纳米管在微纳器件中的应用进程。     

集群磁流变效应微磨头平面研抛加工参数研究

本文实验研究了磁感应强度、研抛压力、加工速度及加工时间等几个加工参数对集群磁流变效应微磨头平面研抛加工效果的影响。实验结果发现,随着磁感应强度的增强,材料去除率增大,而表面粗糙度略有提高;研抛压力及加工速度与材料去除率成正比,表面粗糙度随加工速度的提高逐渐变大,而随着研抛压力的增大先降低后增加,当压力为6898Pa时到达最小;随着加工时间的增加,材料去除量线性增大,而粗糙度先迅速降低后逐渐趋于稳定。在此基础上,提出了集群磁流变效应微磨头平面研抛加工的材料去除模型,其加工特征介于游离磨料研磨抛光和固着磨料研磨抛光之间,是一种全新的平面研抛加工技术,有着较好的应用前景。     

型孔电解加工阴极优化试验研究

为解决电解加工型孔的加工稳定性和形状精度等问题,建立了异形孔电解加工稳定过程中加工间隙数学模型,分析了工具阴极结构对加工区域和非加工区域的电场及其均匀性以及其对电流密度与加工效果的影响,通过优化工件结构改善了加工间隙内的电场分布,使工件形状精度显著提高,并进行相关试验对仿真结果进行验证。得出结论:在相同的电解加工参数下,工具电极的结构对工件的形状精度有着显著的影响,通过优化工具电极结构,改善加工间隙内的电场分布与电流密度,让加工间隙内的流场更为稳定,使工件侧壁垂直度提高,提高了电解加工的形状精度与加工稳定性。     

磨粒类型对K9玻璃剪切增稠抛光的影响

目的 采用剪切增稠抛光方法对K9玻璃进行抛光,以工件表面粗糙度Sa为评价指标,研究不同磨粒抛光液对K9玻璃的抛光效果。方法 采用金刚石、CeO2、Al2O3和SiO2等4种单一磨粒,以及金刚石+SiO2混合磨粒,制备了不同的剪切增稠抛光液,并测试其流变特性。以?20 mm K9玻璃圆片为工件,首先在相同磨粒浓度下,进行4种单一磨粒抛光液的抛光实验,观测在抛光时间不同时工件表面粗糙度Sa的变化情况,比较4种抛光液的抛光效果。然后,对比CeO2抛光液与金刚石+SiO2混合磨粒抛光液的抛光效果,并分析讨论混合磨粒抛光液的材料去除过程。结果 使用CeO2抛光液抛光35 min后,将工件的表面粗糙度Sa从(233.1±15.2)nm降至(1.6±0.2)nm;金刚石抛光液次之,在抛光55 min后工件的表面粗糙度Sa达到(1.86± 0.2)nm;Al2O3抛光液的效果相对最差。采用SiO2(质量分数10%)+金刚石(质量分数5%)抛光液,在抛光5 min后工件的表面粗糙度Sa比CeO2抛光液的低53.3%;在抛光35 min后,工件的表面粗糙度Sa从(230.7±10.5)nm降至(1.43±0.9)nm。在金刚石(质量分数5%)抛光液中添加不同浓度SiO2磨粒的抛光实验中发现,在抛光初始阶段,抛光效率随着SiO2磨粒浓度的增加而增大。结论 CeO2抛光液和SiO2(质量分数10%)+金刚石(质量分数5%)抛光液的抛光效果相对最优,后者在低表面质量时的抛光效率更高。     

CMP抛光半导体晶片中抛光液的研究

本文分析了化学机械抛光(CMP)半导体晶片过程中抛光液的重要作用,总结了抛光液的组成及其化学性能(氧化剂、磨料及pH值等)和物理性能(流速、粘性及温度)对抛光效果的影响规律,研究发现:酸性抛光液常用于抛光金属材料,pH最优值为4,碱性抛光液常用于抛光非金属材料,pH最优值为10～11.5;氧化剂能有效提高金属材料的抛光效率和表面平整度;磨料的种类、浓度及尺寸会影响抛光效果;分散剂有助于保持抛光液的稳定性;抛光初始阶段宜采用较低流速,然后逐渐提高;抛光液的粘性会影响晶片与抛光垫之间的接触模式、抛光液的均布、流动及加工表面的化学反应;抛光液温度的升高有助于提高抛光效率.最后本文指出了抛光液循环使用的重要意义及常用方法.     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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).     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.