【作者】 郑日升；

【导师】 王大伟； 方啸虎； 余佐军；

【作者基本信息】 中南大学 ， 矿产普查与勘探， 2011， 博士

【摘要】 叶蜡石是一种层状结构的粘土矿物,在层状结构硅酸盐矿物中叶蜡石含水最少,这一结构和组成决定了它优良的物理化学性质,内摩擦系数小,耐火度高,导热系数小,在加热过程中脱水温度范围宽、体积稳定,内摩擦系数随承受压力增大而增大等特点。叶蜡石是一优良的固态传压介质。、叶蜡石在冶金、建材、轻工、化工、石油、电器工业部门和农业上都有广泛应用。论文通过研究叶蜡石在六面顶超高压下的流变规律,系统探讨了叶蜡石在六面顶超高压装置中对实现传压和密封的作用机理,系统总结近五十年来六面顶超高压技术的研究成果,对超高压设备、超高压模具和传压介质的设计提供了科学依据。论文提出了六面顶超高压技术“终态对称”理论,完善了超高压腔体与传压介质结构的设计方法,并在高温高压工业化合成金刚石方面得到了成功应用。研究成果对开发新的传压介质,充分挖掘六面顶超高压设备的潜力,研究新的高温高压超硬材料合成技术有着重要的指导意义。论文研究的主要工作和取得的创新成果如下：1.首次对六面顶超高压腔体进行分区域研究,测定叶蜡石在超高压条件下的压力-位移曲线和压力-流变量关系曲线,分析叶蜡石在六面顶超高压腔体内的流动和压缩过程,揭示了叶蜡石在六面顶超高压条件下的塑性流变和高压等静压压缩规律。2.首次建立了叶蜡石内摩擦系数、流变量等参数与硬质合金顶锤结构尺寸的关系模型,分析了各参数的功能和作用,为六面顶超高压腔体结构设计提供了科学依据和具体计算方法；3.实验发现在六面顶超高压腔体内,叶蜡石在较低压力下首先完成塑性变形,随即进入弹性压缩过程。在超高压条件下叶蜡石的密度大于常压下的矿石密度。六面顶锤面尺寸对叶蜡石的密封效果影响最大,从理论和实验两个方面证明了大腔体具有更好的密封性能。这一结论为超高压腔体结构设计提供了实验支持和可供参考的理论依据。4.首次用数学语言表达了六面顶超高压模具设计的形状补强原理和应力补强原理。深入研究了“三心合一”原理,对六面顶超高压装置设计、加工、使用和维护具有指导作用。5.通过研究叶蜡石流变规律,提出了“终态对称”理论。超高压腔体结构应有利于传压和满足密封等合成条件的要求。同时,为了满足静力平衡条件,超高压腔体工作的初始状态可以不对称。但最终状态必须是对称的。“终态对称”理论为建立硬质合金顶锤和叶蜡石块结构尺寸配合关系,及设计新型六面顶超高压腔体结构提供了理论依据和具体计算方法。6.系统阐述了六面顶超高压技术的“终态对称”理论,为传压介质和超高压腔体的结构设计提供了理论基础,并按照新的理论设计金刚石合成腔体结构,取得了良好的应用效果。按照“终态对称”理论,用Φ560mm缸径的六面顶压机,将超高压腔设计从Φ42mm扩大到Φ48mm,提高产能30%以上,顶锤消耗降低至合成每万克拉金刚石消耗0.5公斤硬质合金的水平,不仅让设备的潜能得到了充分挥发,而且保证了超高压腔体工作更稳定。更多还原

【Abstract】 Pyrophyllite, a kind of phyllosilicate minerals with least water content exhibits alayered structure, this special structure and composition determine its physical and chemical properties. This mineral was characterized by small internal friction coefficients, low expansion coefficient, high refractoriness, low thermal conductivity and wide dewatering temperature, volume stability, internal friction coefficients increases with confining pressure etc. Pyrophyllite is a excellent pressure transmitting medium. It is widely used in metallurgy, building materials, light industry, petroleum, chemical industry, electrical appliance industry and agriculture.Through the study of the flow and deformation pattern of pyrophyllite under high pressure, the author analyzes its mechanism of sealing and pressure transmitting performance in cubic press, and systematically summarizes the researches on technology of cubic press in the past few decades. This paper put forward "the final state symmetry" theory of ultrahigh pressure technique about cubic press, which has improved the process design about ultrahigh pressure cell and pressure transmitting medium and acquired succeed application in dimond synthsis. This research results play a significant role in the development of new pressure transmitting medium and potentials of cubic press. Also, this study is instructive in new synthetic technology of superhard material.The most significant innovations of this research are as follows: 1. For the first time, the ultrahigh pressure cell of cubic press is divided into two regions, and their role is discussed respectively. The pressure-distance curve and pressure-flow weight curve of pyrophyllite under ultrahigh pressure was determined. Also these two curves has been used to study the rheology of pyrophyllite, which revealed the law of plastic flow and static compression of pyrophyllite under ultrahigh pressure.2. For the first time, the relationship between internal friction coefficient and flow weight of pyrophyllite and the structure size of cemented carbide anvil was established, this research analyzes these parameter, providing theory basis and scientific calculation method to design structure of cell in cubic press.3. It was found that pyrophyllite accomplished plastic deformation in the lower pressure, and then entered the elastic compression process. Under the ultrahigh pressure, the density of pyrophyllite is greater than the density under atmospheric pressure. The anvil top size has the greatest influence on sealing of pyrophyllite. Results obtained from the study of flow law of pyrophyllite under the ultrahigh pressure can be used to find the right way for the realization of seal and effective pressure transmission. From theoretical and experimental aspects, it was demonstrated that large cell has a better sealing performance.4. Expressing the principle of shape reinforcement theory and stress reinforcement theory of ultrahigh pressure mold design in a concis mathematical language. And "three centre-in-one point" principle of was studied, whuch offer guidance on equipment design, process, usage and maintenance of cubic press.5."The final state symmetry" theory was raised through the study of pyrophyllite flowing deformation law. The final work state of ultrahigh pressure cell must be able to keep tight and able totransmit pressure. At the same time, in order to meet the needs of static equilibrium, the final work state ultrahing pressure cell must be exactly symmetric, while the initial state might not be symmetric."The final state symmetry" theory serves as theoretical basis for a new ultrahigh pressure cell structure design."The final state symmetry" gave theoretical basis of theory for the design of a new ultrahigh pressure cell structure. And the relationship established between carbide anvil and pyrophyllite structure size provided a calculating method for the design of them.6. Systematically explaination of "the final state symmetry" theory of the cubic ultrahigh pressure technology. This research lays a theoretical fundation for structural design of the pressure transmitting medium and ultrahigh pressure cell. According to this new theory, enlarging the diameter of ultrahigh pressure cell from Φ42mm to Φ48mm, the capacity would increased by30%with the cubic press which cylinder diameter is Φ560mm. Also, the anvils consume was obviously decreased. In this case a new cell designed by this theory is a revolutionary change for the reason that not only it reaches the device potential but also maintain its stability.更多还原