Phase transformation and interface segregation behavior in Si3N4 ceramics sintered with La2O3–Lu2O3 mixed additive

Microstructure and mechanical property of silicon nitride (Si₃N₄) ceramic are strongly dependent on the selection of sintering additives. When rare‐earth (RE) oxide is used as the sintering additive, segregation of RE ions at interface between Si₃N₄ grain and intergranular glassy film (IGF) is believed to play a critical role. Although the ionic radius of RE ion is known to be an empirical parameter to modify the mechanical property, the correlation between the segregated ions and their ionic radii is still under controversy. In order to address this issue, (i) rate of α‐β phase transformation and (ii) segregation behavior at the interface were studied for Si₃N₄ ceramics sintered using mixture of La₂O₃ and Lu₂O₃ as additives in this study. Specimens of Lu content 30% and higher exhibited lower activation energies for the α‐β phase transformation as compared with those of Lu content 20% and lower. In terms of the segregation behavior, La was preferably segregated at one site and Lu at the other site along β‐Si₃N₄/IGF interface in the specimens of Lu content 30% and higher. It is understood from these results that Lu segregation site should be more closely related with grain growth.     

Socio-spatial differentiation and residential segregation in the Chinese city based on the 2000 community-level census data: A case study of the inner city of Nanjing

Socio-spatial differentiation and residential segregation have been studied extensively in numerous cities and have contributed significantly to the understanding of urban spatial and social structures. Analyses of diverse data sets at varied spatial scales have supported the development of theoretical frameworks. However, the majority of Chinese case studies published in recent decades were dominantly based on either non-spatial data or population census data at sub-district (or jiedao in Chinese) level. These analyses have been limited through using low-resolution aggregate data resulting in incomplete or biased findings. This paper aims to examine the fine-scale socio-spatial structure of the inner city of Nanjing using the fifth population census data of 2000 at the lowest spatial scale – community (or juweihui in Chinese) level. Our findings reveal that the policies of the socialist era and the initial outcomes of the introduction of a free market, particularly with regard to the creation of new elite spaces within the inner city, have shaped a complex pattern of socio-spatial differentiation and residential segregation.     

Alloying and surface composition of model Pd–Ag films synthesized by electroless deposition

PdAg model films and real composite membranes were prepared by sequential electroless deposition on top of porous stainless steel supports. Their surface properties were investigated by X-ray photoelectron spectroscopy (XPS), Angle resolved XPS and sputtering depth profile. It was shown that the surface of the alloy was strongly enriched in silver after the annealing treatment up to 500 °C on hydrogen stream. A relationship between the Ag 3d_5/2 core-level binding energy shift and the silver surface composition was observed from the XPS data obtained with the model samples. The surface composition of real membranes after both hydrogen permeation and reaction experiments showed silver enrichment, in agreement with the data obtained from the model sample.     

EA4T车轴钢中斑点状偏析的原因分析

采用宏观检验、化学成分分析、金相检验、工艺分析以及炉数统计等手段对EA4T车轴钢中存在斑点状偏析的原因进行了分析。结果表明:该斑点状偏析为合金成分正偏析,原料粒度、模温、钢液过热度以及钢锭锥度等冶炼参数不合理是主导因素。     

Q345E热轧中厚板探伤不合格原因分析

通过低倍检验、金相检验和断口分析等方法分析了Q345E热轧中厚板探伤不合格的原因。结果表明:探伤不合格的原因是在热轧板中心区域偏析带存在硫化锰和碳氮化铌夹杂物,并通过控制和调整工艺解决了该问题。     

莱钢新二区265m2烧结机降低固体燃耗的措施

莱钢股份炼铁厂4号265m2烧结机自投产以来通过加强工艺操作和参数的控制、强化生产管理和技术攻关等一些列措施,使得烧结固体燃耗由原来的57.86kg/t降低到2010年的52.85kg/t,取得了较好的效果.     

八钢板坯连铸动态轻压下技术的工业应用

经过近一个月时间紧张的现场调试,CISDI板坯连铸轻压下成套技术已成功地在八钢第二炼钢厂三号板坯连铸机上投入了工业化应用,整个系统算法理念先进、平台构建合理、控制功能完善、运行稳定可靠,引入了全新的辊缝标定方法,具有良好的辊缝控制精度和合理的油缸压力反馈,通过对多个钢种铸坯试样的低倍检测对比分析表明,实施动态轻压下功能...     

无取向电工钢XG800WR连铸电磁搅拌试验研究

采用铸坯低倍组织检验和化学分析的方法,研究板坏连铸机二冷区电磁搅拌器电流和频率参数对无取向电工钢XG800WR板坯中心偏析和等轴晶率的影响,结果表明:铸坯等轴晶率随着搅拌器电流强度和电流频率的增大而增加.采用二冷区电磁搅拌可减小中心易偏析元素S的偏析,试验得出:减小铸坯S偏析效果最好的电磁搅拌参数为电流380～400A...     

09CuPCrNi-A热轧钢板剪切后开裂原因分析

通过扫描电镜、能谱分析、金相检验等手段,分析了造成09CuPCrNi-A钢板剪切后横断面上出现中心开裂及钢板冲击韧性波动的原因。确认钢板剪切后中心开裂是由P及S偏析所致,这也是导致钢板冲击韧性波动的原因。     

高强船板中心偏析产生的原因分析及预防措施

从工艺及设备两个方面分析中心偏析产生的原因,结合生产现场存在的主要问题,采取控制钢水过热度、恒定拉速、优化二冷配水、加大凝固末端辊缝收缩量等措施,改善铸坯内部质量,取得了良好效果,高强船板断口分层改判率由原来的3.09%下降为1.09%。