核磁共振中基于分子间多量子相干理论扩散行为的模拟

本文采用粒子随机行走模型结合分子间多量子相干理论模拟双组分核自旋体系溶液分子的表观扩散行为,将模拟得到溶液分子表观扩散率与溶液分子自扩散系数的关系,与理论预测结果进行比较,发现二者吻合得很好。     

硅钢中Si原子对C原子扩散过程影响的第一性原理研究

使用基于密度泛函理论的第一性原理计算法探究硅钢内部C原子的扩散特性。首先,建立2×2×2的硅钢晶胞;其次,由过渡态搜索(CI-NEB)方法确定C原子在硅钢晶胞中的扩散方式,即C原子通过在第一邻近(Ⅰ)八面体间隙位置之间连续跳跃完成自身扩散;最后,通过设置不同C原子的扩散路径,计算得出C原子扩散激活能及扩散系数。研究结果表明：在硅钢中C原子的占位为八面体间隙位置,硅钢中的硅元素可以减小C原子的扩散激活能,增大C原子扩散系数,使得C原子在铁基合金中更容易发生扩散。综上可知,运用第一性原理探究合金中原子相互作用及扩散特性是准确且可行的。     

氢在无序态和有序态Ni3Fe合金中的扩散行为

采用电解渗氢的方法研究室温下氢在无序态和有序态Ni₃Fe合金中的扩散行为.研究结果表明,在相同渗氢温度下,渗氢后的Ni₃Fe合金的延伸率随渗氢时间的增加而降低,拉伸断口上的沿晶断裂区(IG)的深度随渗氢时间的增加而增加;在相同渗氢时间下,合金拉伸断口上的沿晶断裂区的深度随渗氢温度的增加而增加.沿晶脆性断裂区的深度与渗氢温度和时间的关系符合菲克扩散方程的解.时间滞后法计算结果表明,氢在无序态Ni₃Fe合金中的表观扩散系数高于在有序态合金中的表观扩散系数.氢在无序态和有序态Ni₃Fe合金中的扩散激活能分别为44.9 kJ/mol和29.5 kJ/mol.     

Fe对氢在无序态和有序态Ni3Fe合金中扩散的影响

研究阴极渗氢时Fe的化学计量比对氢原子在无序态和有序态Ni₃Fe合金中扩散的影响.在相同渗氢条件下,随着Fe含量的增加,渗氢后无序态和有序态Ni₃Fe合金的拉伸延伸率逐渐增加,断口上的沿晶断口深度逐渐减小.时间滞后法计算结果表明,在相同渗氢条件下,随着Fe含量的增加,氢在无序态和有序态Ni₃Fe合金中的表观扩散系数和表观扩散激活能逐渐减少.在相同条件下,氢在无序态Ni₃Fe合金中的扩散系数大于氢在有序态Ni₃Fe合金中的扩散系数.     

分子动力学模拟液态硅的扩散性质

运用分子动力学方法模拟液态硅的扩散性质,结果表明液态硅中密度的变化并未引起液态硅扩散常数明显规律变化;液态硅扩散常数随温度的变化则可以用Arrhenius经验式较好地拟合,由此得到的扩散指数前因子为30.8×10-3cm2@s-1,激活能为0.92eV,二者的数值与其它方法的结果相比均偏大,表明由Tersoff势得到的原子间相互作用大于真实系统中硅原子间的相互作用.     

球墨铸铁热浸镀铝的扩散行为

为了提高铸铁模具的抗高温氧化性能,通过制备热浸镀铝试样、对试样进行扩散退火,采用扫描电镜（SEM）观察Al元素的扩散行为,观察700℃下,不同扩散时间和3h下不同扩散温度的试样截面形貌.研究和探讨在不同温度下和不同保温时间条件下Al的扩散情况.结果表明：对热浸镀铝试样进行扩散,温度越高,Al的扩散速度越快;在相同扩散温度时,增加保温时间有利于Al元素在合金层中扩散,随扩散时间的增加,Al层逐渐变薄直至消失,Fe-Al合金层明显增厚.     

Cr,Mo对Cu/Si(100)薄膜体系结构、电阻率及扩散性能的影响

利用简易合金靶材在Si(100)基底单靶磁控溅射制备Cu(Cr)、Gu(Mo)薄膜.研究薄膜在300~500℃退火前后的结构、电学及扩散性能的变化.结果表明,Cr、Mo的加入增强了Cu薄膜的(111)织构,且溅射态薄膜电阻率显著增加.真空退火后,Cu(200)和Cu(220)衍射峰增强,但薄膜保持较强的(111)织构.Cu(1.19%Cr)薄膜电阻率随温度升高先减小后增加,400℃退火后电阻率最小,为2.76μΩ.cm,接近纯Cu薄膜(2.55μΩ.cm);而Cu(1.28%Mo)薄膜的电阻率一直呈下降趋势.Cu(1.28%Mo)薄膜在400℃退火30 min后,薄膜与Si基底间的互扩散深度约60 nm,与纯Cu薄膜(约70 nm)相似.而Cu(1.19%Cr)薄膜的互扩散深度较小为30 nm.Cr显著减小了Cu、Si之间的互扩散.这与Cr在薄膜/基体界面处的偏聚有关.     

长焦距Si微透镜阵列的制作及点扩散函数测量

针对用常规光刻热熔法制作折射型微透镜阵列的过程中,临界角效应严重制约了长焦距微透镜阵列制作问题,提出了曲率补偿法;在经过常规光刻热熔成形和离子束刻蚀技术制成的硅微透镜阵列上再涂敷几层光刻胶,以降低各单元微透镜的曲率,然后再次进行加热固化和离子束刻蚀。扫描电子显微镜（ＳＥＭ）显示微透镜阵列为表面极为平缓的方底拱面阵列,表面探针测试结果显示用补偿刻蚀法制作的微透镜的物方Ｆ数和像方Ｆ‘数分别可达到４９．     

层错几率峰位移测定法及在Fe—Mn—Si合金中的应用

将Ｘ射线衍射峰位移法引入用于测量Ｆｅ－Ｍｎ－Ｓｉ合金的层错几率α，所需要的精确点阵常数由数值计算获得，并评价内应力引起的峰位移对测量结果的影响，内应力引起的α测量值相对误差约４％，因而可忽略不计。研究结果表明，随Ｍｎ含量的减少或训练次数的增加，α增加，值得指出的是，峰位移法可用来测量单一的形变α，而不像峰位移法给出两种层错几率之和，其中β是生长层错几率。     

Modeling decarburization kinetics of grain-oriented silicon steel

A mathematic model has been presented to predict the decarburization kinetics of grain-oriented silicon steel sheet in the gas mixture of N2–H2–H2O during annealing.This model is based on the carbon flux balance between the oxidation reaction at the surface and the carbon diffusion inside the steel sheet.It can be numerically solved to quantify the influences of annealing temperature and atmosphere on decarburization kinetics when the boundary conditions are properly determined.In case that a humid gas mixture is employed during annealing,the most influential process parameter is temperature rather than compositions of the gas mixture,because the diffusion of carbon in ferrite is the rate-limiting step.Therefore,a higher temperature is required for the efficient decarburization of the thicker silicon steel sheet using the industrial continuous annealing production line.     

超薄MoN扩散阻挡层的扩散阻挡性能分析

采用磁控溅射法,制备了超薄MoN扩散阻挡层,并对Cu/MoN/Si体系进行真空退火。用四点探针(FPP)、X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)进行薄膜电性能和微结构表征。分析结果表明,MoN作为Cu扩散阻挡层结构具有良好的热稳定性,失效温度达到600℃,明显优于Mo扩散阻挡层。     

高硅铸铁在多种环境下的腐蚀行为研究

采用失重分析、金相分析等实验方法研究了高硅铸铁的组织及在不同环境下的耐腐蚀性能。实验结果表明,高硅铸铁在各种腐蚀介质中均有良好的耐蚀性,腐蚀溶液的浓度对高硅铸铁的腐蚀速度有较大影响。高硅铸铁在同样浓度的酸性环境中的耐蚀性比在碱性环境中好,在中性盐环境中的耐蚀性则居两者之间。     

Abnormal austenite-ferrite transformation behavior in pure iron

The austenite → ferrite transformation is themost important reaction route in the manufacture ofFe-based materials. Here the austenite (γ) → ferrite (α)transformation of pure iron was systematically explored byhigh-resolution dilatometry. Abnormal transformation ki-netics, multi-peak discontinuous reaction, was recognized inpure iron according to the variation of the ferrite-formationrate. The occurrence the one or the other type of γ→∝ trans-formation strongly depends on the grain size: the transfor-mation type changes from abnormal to normal (single-peakcontinuous reaction) with decreasing grain size. The inherentreason for the occurrence of abnormal transformation couldbe attributed to the repeated nucleation in front of the mov-ing γ/α interface induced by the accumulation of elastic andplastic accommodation energy.     

纯铁粉的温压行为

在Instron热模拟机上对不添加润滑剂的纯铁粉进行温压和冷压的实验比较,用扫描电镜、X射线衍射和金相显微镜对粉末及其压坯进行分析,并对纯铁粉的温压致密化机理进行探讨。结果表明:在不同的压制压力下,纯铁粉在压制时,粉末在加热和保温过程中严重氧化使铁粉的显微硬度提高,铁粉颗粒的加工硬化程度增大,塑性变形能力降低,并最终导致温压压坯中铁粉晶粒(110)面衍射峰的半高宽比室温压制时的低;同时,由于纯铁粉在130℃时被氧化,使得粉末的剪切强度增加,导致粉末之间以及粉末和模壁之间的摩擦增大,温压成形的有效压力降低;在这些因素的综合作用下,使得在130℃压制的温压压坯的密度低于相同压力下纯铁粉冷压压坯的密度,并且其脱模力也要远远大于冷压压坯的脱模力。     

Diffusion behavior and distribution regulation of MgO in MgO-bearing pellets

In this paper, the diffusion behavior between MgO and Fe₂O₃ (the main iron oxide in pellets) is investigated using a diffusion couple method. In addition, the distribution regulation of MgO in MgO-bearing pellets is analyzed via pelletizing experiments. The results illustrate that MgO is prone to diffuse into Fe₂O₃ in the form of solid solution; the diffusion rate considered here is 13.64 μm·min-1. Most MgO content distributes in the iron phase instead of the slag phase. The MF phase {(Mg_1-x Fe_x)O·Fe₂O₃, x ≤ 1} is generated in the MgO-bearing pellets. However, the distribution of MgO in the radial direction of the pellets is inconsistent. The solid solution portion of MgO in the MF phase is larger in the outer layer of the pellets than in the inner layer. In this work, the approximate chemical composition of the MF phase in the outer layer of the pellets is {(Mg_0.35-0.77·Fe_0.65-0.23) O·Fe₂O₃} and in the inner layer is {(Mg_0.13-0.45·Fe_0.87-0.55) O·Fe₂O₃}.     

电动汽车电机用硅钢材料的应用研究进展

电动汽车中的驱动电机铁芯材料主要为无取向硅钢片,除了磁性能外,其机械和物理特性包括加工和装配性能也将影响最终电机的性能和生产成本。结合国内外的研究成果,介绍铁芯材料加工过程及电机运行环境对硅钢性能的影响,并针对不同的影响因素提出优化电机设计的方法。     

取向硅钢脱碳过程的数值模拟分析

通过对硅钢钢带表面的脱碳反应动力学和碳在钢带内部扩散机理的研究,建立取向硅钢脱碳过程的数学模型,模拟分析脱碳气氛、退火温度、钢带的初始碳含量和厚度等因素对脱碳过程的影响,并与试验结果进行对比分析。结果表明,所建模型是可靠的;气氛中的水氢比过高会引起钢带表面过氧化而阻碍脱碳;钢带初始碳含量只在脱碳初期对脱碳过程有所影响;钢带中心部位的碳向外表面的扩散是影响脱碳过程的重要环节;提高退火温度并适当降低露点有利于加快取向硅钢钢带脱碳过程的进行。     

纯铁药型罩材料的动态应力-应变行为

利用Hopkinson杆技术对经930℃下退火2h的纯铁药型罩材料进行了冲击压缩实验,测定了该材料在不同应变率下的动态应力-应变关系.借助光学显微镜对变形后纯铁的组织进行了观察,研究了在不同应变率下变形过程中纯铁的组织演变和动态应力-应变行为.研究表明:在650～3850s-1的应变率范围内,纯铁药型罩材料有显著的孪生变形,发生了明显的应变强化和应变率强化效应,且最大应变也随应变率的提高而增加;在高应变率冲击下,孪生和滑移是纯铁的主要塑性变形机制,也是纯铁高应变率增强增塑的主要机制.     

Corrosion-wear behavior of nanocrystalline Fe88Si12 alloy in acid and alkaline solutions

The corrosion?wear behavior of a nanocrystalline Fe88Si12 alloy disc coupled with a Si3N4 ball was investigated in acid (pH 3) and alkaline (pH 9) aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe88Si12 alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe88Si12 alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe88Si12 alloy under dif-ferent wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si3N4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe88Si12 alloy in the pH 9 aqueous solution.