凝固科学技术与材料发展——香山科学会议第211次学术讨论会综述

以“凝固科学技术与材料发展”为主题的香山科学会议第211次学术讨论会于2003年9月23～25日在北京香山饭店举行。会议聘请西北工业大学傅恒志院士和清华大学柳百成院士担任执行主席，我国著名材料学家师昌绪院士和中国工程院院长徐匡迪院士参加了本次会议并作了报告。会议的中心议题是：定向凝固与晶体生长及材料发展；快速凝固理论与技术；超常条件下凝固过程与新材料；材料熔体结构与多学科交叉研究。     

超急速传热对材料结构性能的影响

以金属快速凝固为例,概述超急速传热对金属材料结构与性能的重要影响,指出由超常传热引起的非平衡相变过程是造成材料结构性能显著变化的主要原因,分析了对材料高热流短脉冲加热与快速凝固过程的超常传热特点,其主要表现为传热过程的非平衡特性。为了探索超急速传热对材料结构性能的影响机理,需要将这种非平衡传热过程与材料的非平衡相变过程耦合起来。     

铸件凝固方式和砂型铸造方法

由于金属铸造是由液态凝结成固态的过程,因此,具有成形方便且适应性强、成本较低、成形的组织性能较差等特点。铸件的凝固方式可分为逐层凝固、糊状凝固和中间凝固三种方式。砂型铸造包括砂型铸造的工艺过程,造型材料。     

非平衡凝固若干理论问题及其应用

本文介绍国家自然科学基金重大项目“非平衡凝固若干理论问题及其应用”研究的重要性及其理论意义和应用价值、介绍项目的主要研究目的、内容、进展状况、已取得的结果和进一步研究方向。新材料是高技术发展的突破口和支柱,对未来经济技术发展有决定性作用,而合金以至新型超导材料等新材料的制备与质量,是与凝固结晶,尤其是与非平衡凝固过程紧密相关。因此,非平衡凝固过程中界面行为,输运过程,凝固前沿动力学与形态选择,非稳态过渡阶段中的变化,相形成规律和溶质再分配及结晶特性等都是十分重要的研究方向。这些研究成果可为研制新型低偏析抗热腐蚀定向结晶和单晶高温合金、超细定向柱晶材料、可加工永磁合金和高T_c超导材料提供理论依据。     

为发展凝固理论与技术作贡献

我1950年毕业于清华大学机械系,1953年入原苏联莫斯科钢铁学院冶金系攻读研究生,1957年获技术科学副博士学位后回国。我在40年前即认识到凝固理论与凝固过程控制对材料科学与工程的重要性,以后又看到随着凝固理论与凝固技术的发展,它们不但是提高传统材料性能的重要手段,而且也是开发新材料的一条途径,所以一直从事这一领域的科学研究,主要在以下几方面作了一些工作。     

“钢亚快速凝固机理、控制方法及对材料性能的影响”通过验收

金属所和北京科技大学、宝钢研究院承担的国家自然科学基金重点项目“钢亚快速凝固机理、控制方法及对材料性能的影响”近期通过了结题验收。     

快速凝固过程中的溶质分配问题研究

本文就快速凝固过程中的溶质分配机制与规律进行了分析研究,从而对认清快速凝固现象、发展凝固理论和研制具有优异性能的快速凝固合金均具有重要意义。     

刘让苏教授：著名材料物理专家

刘让苏,男,1935年生,汉族,湖南省衡阳县人。湖南大学应用物理系教授,著名的材料物理专家,长期从事金属物理、位错理论、相变理论的教学和研究工作,特别是专注于“非晶态合金”和“液态金属凝固过程”的理论和实验研究。近日,记者采访了这位成绩卓著的材料物理专家。     

科学基金重大项目“超常条件下材料凝固理论研究”通过结题验收

由西北工业大学、清华大学、哈尔滨工业大学、山东大学和中国科学院金属研究所等单位共同承担的国家自然科学基金重大项目“超常条件下材料凝固理论研究”经过4年的运行,于2007年10月通过了结题验收。     

合金凝固过程中的溶质再分配与成分偏析

在平衡凝固、近平衡凝固、非平衡凝固3个层次上讨论了凝固过程的 溶质分配因数,综述了平界面凝固过程和枝晶凝固过程的溶质再分配规律,提出了宏观偏析 的控制参数,并以合金钢 为例,导出了该控制参数与合金成分的关系。     

Bakelite,a condensation product of phenols and formaldehyde,and its uses

Bakelite is a liquid compound of phenol and formaldehyde which on solidification resembles amber in appearance and when used in combination with wood, paper, asbestos, graphite and other substances produces a solid non-resistant, non-inflammable insulating material which promises to have many applications in various industries.     

Investigation on CO(2) laser irradiation inducing glass strip peeling for microchannel formation

The study investigates the use of CO₂ laser to induce glass strip peeling off to form microchannels on soda lime gass substrate. The strip peeling exhibits a strong dependence on the energy deposition rate on the glass surface. In spite of the vast difference in the combination of laser power and scanning speed, when the ratio of the two makes the energy deposition rate in the range 3.0-6.0 J/(cm² s), the temperature rising inside glass will be above the strain point and reach the softening region of the glass. As a result, glass strip peeling is able to occur and form microchannels with dimensions of 20-40 μm in depth and 200-280 μm in width on the glass surface. Beyond this range, higher energy depsotion rate would lead to surface melting associated with solidification cracks and lower energy deposition rate causes the generation of fragment cracks.     

Droplet based microfluidic fabrication of designer microparticles for encapsulation applications

Developing carriers of active ingredients with pre-determined release kinetics is a main challenge in the field of controlled release. In this work, we fabricate designer microparticles as carriers of active ingredients using droplet microfluidics. We show that monodisperse droplet templates do not necessarily produce monodisperse particles. Magnetic stirring, which is often used to enhance the droplet solidification rate, can promote breakup of the resultant microparticles into fragments; with an increase in the stirring time, microparticles become smaller in average size and more irregular in shape. Thus, the droplet solidification conditions affect the size, size distribution and morphology of the fabricated particles, and these attributes of the microparticles strongly influence their release kinetics. The smaller the average size of the microparticles is, the higher the initial release rate is. The release kinetics of drug carriers is strongly related to their characteristics. The understanding of this relationship enables the fabrication of tailor-designed carriers with a specified release rate, and even programmed release to meet the needs of applications that require a complex release profile of the active ingredients.     

Shape-tunable wax microparticle synthesis via microfluidics and droplet impact

Spherical and non-spherical wax microparticles are generated by employing a facile two-step droplet microfluidic process which consists of the formation of molten wax microdroplets in a flow-focusing microchannel and their subsequent off-chip crystallization and deformation via microdroplet impingement on an immiscible liquid interface. Key parameters on the formation of molten wax microdroplets in a microfluidic channel are the viscosity of the molten wax and the interfacial tension between the dispersed and continuous fluids. A cursory phase diagram of wax morphology transition is depicted depending on the Capillary number and the Stefan number during the impact process. A combination of numerical simulation and analytical modeling is carried out to understand the physics underlying the deformation and crystallization process of the molten wax. The deformation of wax microdroplets is dominated by the viscous and thermal effects rather than the gravitational and buoyancy effects. Non-isothermal crystallization kinetics of the wax illustrates the time dependent thermal effects on the droplet deformation and crystallization. The work presented here will benefit those interested in the design and production criteria of soft non-spherical particles (i.e., alginate gels, wax, and polymer particles) with the aid of time and temperature mediated solidification and off-chip crosslinking.     

建筑职业院校音乐欣赏教育初探

建筑是凝固的艺术,在建筑职业院校推广普及音乐艺术教育,对提高建筑专业大学生综合素质和探索培养高素质人才的方法和途径有重要意义.本文从在建筑职业院校开设此课程的重要性、必要性等方面展开探讨,结合教学提出建筑职业院校开设音乐欣赏课程需要注意的事项和建议.     

楼顶防水工艺施工技术

保护层施工,必须待密封材料表面干燥后才能进行,以免影响密封材料的固化过程及损坏密封防水部位。保护层的施工应根据设计要求进行,设计无具体要求时,一般可采用密封材料稀释后作为涂料,加铺胎体增强材料。     

失败创新是市场优胜劣汰的自然选择？——创新企业新产品商业化战略研究

技术优势并不必然导致新产品成功,创新企业能否获得创新收益在很大程度上取决于其商业化战略的效率.在辨析了技术创新研究的四个模糊认识后发现,市场失灵、非优技术强化、消费者固化是阻碍新产品成功的主要因素.在此基础上.建立了新产品商业化战略的主要框架.     

DS80C400在网络通讯中的应用

研究的目的是使得用串口接口进行通信的电子设备可与以太网连接,给出了用C语言编程访问DS80C400的固化程序实现以太网通讯的方法,使得两个串行设备通过以太网进行数据交换,通过DS80C400可以实现串行电子设备与以太网的连接。     

The 2007 Benjamin Franklin medal in materials engineering, Presented to Merton C. Flemings, Sc.D., Massachusetts Institute of Technology, Cambridge, Massachusetts

The second half of the twentieth century marked the emergence of metal casting, also known as solidification processing, as a field for scientific and engineering inquiry. Merton C. Flemings is recognized internationally for his pioneering work in this field resulting in the development of fundamental understanding and novel processes of commercial importance. Amongst his work is semi-solid metalworking (SSM), an environmentally friendly process, which has led to the development of a new world-wide industry providing lightweight, affordable metallic castings for applications ranging from aerospace, to sporting goods, to consumer electronics.     

组织导向、信息技术类型与组织知识管理模式的关系研究

先进的信息技术可以提高知识管理的成效，但如何营造知识分享的组织文化、建立适宜的激励制度，进而使组织成员乐于创造知识和贡献知识，则是企业知识管理的关键所在。以组织导向和信息技术类型为维度构建知识管理模式，分析不同组合对知识管理过程中知识的创造、固化与扩散的影响，旨在为企业成功实施知识管理提供参考。