Study of shrinkage porosity in spheroidal graphite cast iron

This study aims at identifying the relationship between the shrinkage cavities and the solidification structure in spheroidal graphite cast iron. Cast samples specially designed to contain shrinkage cavities were used. The solidification macrostructure was revealed using the Direct Austempering After Solidification method, while the solidification microstructure was revealed by using colour etching. At the midsection of the pieces, the shrinkage cavities and the solidification structure were observed jointly. The study showed that the classification of shrinkage porosity found in literature does not correspond to the ductile iron solidification model recognized by most of the scientific community. Early solidification models, and therefore shrinkage formation mechanisms, were proposed in instances when there was not a thorough knowledge of the morphology of the solid phases during solidification. Nowadays, defects formation mechanisms can be described with higher accuracy. Therefore, an updated classification of shrinkage porosity for spheroidal graphite iron is proposed.     

铁铝阻抗匹配靶的精密扩散连接

为了获得某些材料在在高压条件下的物态方程,制备了用于激光驱动状态方程实验的铁铝阻抗匹配靶,研究了铁铝薄膜的精密热扩散连接技术。以冷轧铁薄膜和超精密加工铝薄膜为原料,研究了热复合工艺条件对其表面形貌、结晶性能、连接界面等参数的影响。利用白光干涉共焦显微镜、X射线衍射仪、膜厚测量仪、扫描电镜等仪器对靶件的表面形貌、厚度、结晶特性、残余应力及界面成分分布等进行分析表征,掌握了相关参数的变化趋势。据此优化工艺参数,制备了高质量的铁-铝阻抗匹配靶。对成靶的测试结果显示,其表面粗糙度小于100nm、厚度一致性控制在100nm以内、界面扩散层厚度约为200nm,且未观测到显微缺陷,满足物理实验的具体要求。     

Hepcidin-Induced Iron Deficiency Is Related to Transient Anemia and Hypoferremia in Kawasaki Disease Patients

Kawasaki disease (KD) is a type of systemic vasculitis that primarily affects children under the age of five years old. For sufferers of KD, intravenous immunoglobulin (IVIG) has been found to successfully diminish the occurrence of coronary artery lesions. Anemia is commonly found in KD patients, and we have shown that in appropriately elevated hepcidin levels are related to decreased hemoglobin levels in these patients. In this study, we investigated the time period of anemia and iron metabolism during different stages of KD. A total of 100 patients with KD and 20 control subjects were enrolled in this study for red blood cell and hemoglobin analysis. Furthermore, plasma, urine hepcidin, and plasma IL-6 levels were evaluated using enzyme-linked immunosorbent assay in 20 KD patients and controls. Changes in hemoglobin, plasma iron levels, and total iron binding capacity (TIBC) were also measured in patients with KD. Hemoglobin, iron levels, and TIBC were lower (p < 0.001, p = 0.009, and p < 0.001, respectively) while plasma IL-6 and hepcidin levels (both p < 0.001) were higher in patients with KD than in the controls prior to IVIG administration. Moreover, plasma hepcidin levels were positively and significantly correlated with urine hepcidin levels (p < 0.001) prior to IVIG administration. After IVIG treatment, plasma hepcidin and hemoglobin levels significantly decreased (both p < 0.001). Of particular note was a subsequent gradual increase in hemoglobin levels during the three weeks after IVIG treatment; nevertheless, the hemoglobin levels stayed lower in KD patients than in the controls (p = 0.045). These findings provide a longitudinal study of hemoglobin changes and among the first evidence that hepcidin induces transient anemia and hypoferremia during KD’s acute inflammatory phase.     

Accumulation and Toxicity of Superparamagnetic Iron Oxide Nanoparticles in Cells and Experimental Animals

The uptake and distribution of negatively charged superparamagnetic iron oxide (Fe₃O₄) nanoparticles (SPIONs) in mouse embryonic fibroblasts NIH3T3, and magnetic resonance imaging (MRI) signal influenced by SPIONs injected into experimental animals, were visualized and investigated. Cellular uptake and distribution of the SPIONs in NIH3T3 after staining with Prussian Blue were investigated by a bright-field microscope equipped with digital color camera. SPIONs were localized in vesicles, mostly placed near the nucleus. Toxicity of SPION nanoparticles tested with cell viability assay (XTT) was estimated. The viability of NIH3T3 cells remains approximately 95% within 3–24 h of incubation, and only a slight decrease of viability was observed after 48 h of incubation. MRI studies on Wistar rats using a clinical 1.5 T MRI scanner were showing that SPIONs give a negative contrast in the MRI. The dynamic MRI measurements of the SPION clearance from the injection site shows that SPIONs slowly disappear from injection sites and only a low concentration of nanoparticles was completely eliminated within three weeks. No functionalized SPIONs accumulate in cells by endocytic mechanism, none accumulate in the nucleus, and none are toxic at a desirable concentration. Therefore, they could be used as a dual imaging agent: as contrast agents for MRI and for traditional optical biopsy by using Prussian Blue staining.     

轨道式铁钻工旋扣钳动态特性分析

旋扣钳是轨道式铁钻工的重要组成部分,其受力和运动特性对整机性能有重要影响。提出一种新型轨道式铁钻工旋扣钳,建立旋扣钳力学模型,利用ADAMS软件对其进行力学特性分析。随后,利用机构的结构分析与综合方法对旋扣钳关键铰点进行运动学分析。研究结果表明：旋扣钳在旋扣过程中的接触力与驱动力均在允许范围内,证明旋扣钳结构设计的合理性;建立旋扣钳关键铰点的位移方程、速度方程以及加速度方程,继而得到偏转角α₂的活动范围为5°～76°、α₃的活动范围为14°～85°以及α₄的活动范围为0°～65°。     

蠕墨铸铁加工研究现状

蠕墨铸铁因为其优秀的力学性能越来越多地被应用在工业当中,特别是在汽车工业中制造高性能和轻质量的柴油发动机方面,已经成为替代灰铸铁的理想材料。然而,蠕墨铸铁优秀的力学性能,使得蠕墨铸铁加工成为一个难题,加工过程存在速度过快刀具过早失效或速度过慢表面质量不达标等问题。基于存在的问题和目前的研究进展,综述了蠕墨铸铁切削机制、内部成分、切削刀具等对加工蠕墨铸铁的影响,并进一步对刀具角度、表面涂层、切削参数、冷却方法等研究进行了介绍,指出了蠕墨铸铁的未来研究方向和发展趋势。     

基于灰色聚类方法的加工中心进给系统可靠性评价

应用MTALAB软件对加工中心进给系统的故障数据进行分析,得到平均首次故障时间(MTTFF)和平均故障间隔时间(MTBF)的点估计值和区间估计值。采用灰色聚类方法划分可靠性指标可拓区间灰数等级,并通过建立白化权函数得到等级区间权重矩阵。再结合构建比较判断矩阵确定的两种可靠性指标权重,最终建立了灰色聚类综合评价模型,对该加工中心进给系统可靠性水平进行评价。     

低Cr钢在CO2/H2S环境中的腐蚀行为研究

目的研究低Cr钢(3%～9%)在60℃的CO_2/H_2S环境中的腐蚀行为。方法将三种低Cr钢(3Cr-H、5Cr-H、9Cr-H)加热到900℃之后,保温40min,进行水冷。对热处理之后的钢试样(依次编号3Cr-H、5Cr-H、9Cr-H)进行高温高压CO_2/H_2S腐蚀模拟实验,通过扫描电子显微镜(SEM)、能谱分析仪(EDS)和X射线衍射仪(XRD)对腐蚀产物膜的微观形貌和成分以及物相组成进行分析。结果 3Cr、5Cr、9Cr钢的腐蚀速率分别为0.0443、0.0372、0.0060 mm/a,且腐蚀速率随着Cr含量的增加而降低。3Cr-H、5Cr-H、9Cr-H钢的腐蚀速率分别为0.1527、0.0445、0.0070mm/a,其腐蚀速率也是随着Cr含量的增加而降低。其中,3Cr-H钢的腐蚀速率是3Cr钢的3.4倍,耐蚀性能变化明显。5Cr-H钢的腐蚀速率是5Cr钢的1.19倍。9Cr-H钢的腐蚀速率与9Cr钢相比,几乎没有差别。六种材料的腐蚀产物均为FeS化合物,并没有发现典型的FeCO_3晶体(CO_2腐蚀产物)。3Cr、5Cr、3Cr-H、5Cr-H钢的腐蚀产物均为双层膜结构,9Cr、9Cr-H钢的腐蚀产物为单层膜结构。结论热处理未影响腐蚀速率随Cr含量的变化趋势,基体中Cr含量越高,腐蚀产物膜中的Cr富集量越大,从而有助于降低其腐蚀速率。热处理对3Cr钢的显微组织及其腐蚀行为影响最为显著,不仅加剧了其均匀腐蚀,而且促进了点蚀的发生,这是因为热处理后,显微组织中析出第二相含Cr的碳化物,使部分区域出现了贫Cr的现象。     

基于低共熔溶剂电沉积铁纳米晶体：过电位、氢键给体对形貌的影响

系统研究铁在3种低共熔溶剂中的电沉积行为以及过电位和氢键给体对铁沉积物形貌的影响。结果表明,在DES1和DES2中,过电位对铁沉积物形貌没有明显影响,但在DES3中过电位对铁纳米粒子的形貌有显著影响。此外,研究结果还证实了氢键给体的种类对铁沉积物的形成有着密切的联系:尿素氢键给体有助于片状网络结构铁膜的形成;乙二醇氢键给体有助于准球形铁纳米粒子的形成;而乙二醇和丙二酸氢键给体的协同作用有助于空心球和类毛线球状等纳米粒子的形成。