Field Application Effects in Rapid Sintering of Activated Powders by a Manufacture Friendly Consolidation Process

9532072格罗扎在美国国家科学基金会以前资助的研究中，研究人员已经证明，通过以特定方式施加电场和压力，金属和陶瓷粉末可以快速固化到非常高的密度。这一过程被称为“等离子活化烧结”。潜在的假设是，放电在颗粒之间产生等离子体，导致表面局部变化，这有助于在随后的加压电阻加热中快速烧结。然而，确切的机制还没有得到验证。在目前的研究中，研究人员将使用光纤来观察粒子之间是否真的存在等离子体。电场的作用将被研究，因为这一过程似乎既适用于高导电性金属(镍)，也适用于导电性较差的陶瓷(氧化铝)。虽然先前的工作表明氮化铝中原子水平的界面结合具有干净的无氧化物晶界，但粒子表面发生了什么还没有被了解。这项研究还将包括开发和验证现场辅助固结下的烧结模型。由此产生的微观结构将与开发从粉末材料制造有用部件所需的控制措施相关联。粉末固结是制造几类先进结构陶瓷以及工业中使用的许多粉末金属部件的核心。从非常细的粉末开始是最大化材料性能的理想方法。然而，在加工细粉时，要消除颗粒之间的气孔而不失去起始细粉尺寸的固有优势是非常困难的。由于气孔会削弱零件的强度，所以这里描述的任何可以快速固结粉末的工艺都提供了一种新的制造途径。这项研究将为该工艺从研究阶段放大到开发和最终商业化所需的大型设备奠定基础。几家工业粉末加工制造商对这一新工艺表现出了兴趣。

9532072 Groza In the prior NSF funded research, the investigators have demonstrated that metals and ceramics powders can be rapidly consolidated to very high density by applying electric fields as well as pressure in a specified manner. The process is termed "Plasma Activated Sintering." The underlying hypothesis is that electric discharge creates plasma between particles causing local changes on the surface which facilitates the rapid sintering in the subsequent resistant heating under pressure. However, the exact mechanism has not been verified. In the current research, the investigators will use fiber optics to see whether there is indeed plasma between particles. The role of electric field will be studied since the process appears to work on both highly conductive metals (nickel) as well as less conductive ceramics (aluminum oxide). While prior work has suggested atomic level interfacial bonding with clean oxide free grain boundaries in aluminum nitride, what is going on at the particle surface has not yet been understood. The research will also include developing and verifying sintering models under field assisted consolidation. The resultant microstructures will be correlated to the process to develop controls needed to make useful parts from powder materials. Powder consolidation is central to the manufacture of several classes of advanced structural ceramics as well as many powder metal parts used in the industry. Starting from very fine powders is the desired approach to maximize the material properties. However, in processing fine powders, elimination of pores between particles is very difficult without losing the intrinsic advantage of the starting fine particle size. Since pores weaken the parts, any process such as the one described here which can rapidly consolidate the powders offers a new manufacturing avenue. This research will lay the foundation for the necessary large scale equipment needed for the process to be scaled up from the research stage to deve lopment and final commercialization. Several industrial powder processing manufactures have shown interest in this novel process.