Analysis of the contact electrification in metal-metal, metal-dielectric and dielectric-dielectric contacts applying broadband ultra-sensitive charge detection

应用宽带超灵敏电荷检测分析金属-金属、金属-电介质和电介质-电介质接触中的接触起电

• 批准号: 518939313
• 负责人: Professor Dr. Rolf Möller
• 金额: --
• 依托单位: Forschungsgruppe Experimentalphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/518939313?language=en
• 关键词: Analysis; contact; electrification; metal; dielectric

Despite the fact that contact electrification and triboelectricity has been observed for more than 2000 years the underlying physics are still unclear. However, it is not only of academic interest, it is of major importance in applications. On the one hand discharges following contact electrification may cause severe explosions of flammable liquids or dust. On the other hand, there are many useful purposes, like exhaust gas cleaning etc. We have developed a novel experimental technique which enables us to study the charge transfer between a free-falling spherical particle and a surface with unprecedented precision. It relies on self-built charge amplifiers providing a resolution < 1 fC and < 1 µs. Experiments performed for the contact between metals reveal that the particles are discharged during the contact but regain within less than a microsecond unexpectedly high charge when the electric contact breaks. Depending on the impact velocity the charge is much higher than predicted by the generally accepted model by Harper and Lowell. An extended model was proposed which explains the findings based on the deformation of the two objects brought into contact. Preliminary experiments including a ring electrode in proximity to the bottom plate demonstrate an even enhanced charge resolution. In addition, the extended setup allows to detect shifts between the center-of-mass and the center-of-charge of the sphere. The goal of this project is to analyze the key processes of contact electrification between metals (e.g. Au, Cu, Pt) and between metals and dielectrics (e.g. Si, InP, Al2O3, ZrO2) as well as between two dielectric materials. The study will be focused on semiconductors and inorganic insulators to address the role of intrinsic electronic states for the charge transfer at well-defined surfaces and at the contact interface. The experiment will be redesigned in a customized UHV chamber which allows to study the contact electrification under vacuum as well as defined gaseous atmospheres. Using low-energy electron beams or ultraviolet light the surface potential of insulating dielectric particles prior to contact is adjusted. The capability of the new setup to measure how the charge evolves in subsequent contacts shall be used to analyze the charge transfer as a function of impact velocity and charge before the contacts. By varying the materials, the effect of the contact potential, the surface band bending, the polarizability of the materials and the existence of adlayers (e.g. H2O) on the transferred charge will be investigated. The novel implementation of the ring electrode will be used to determine any asymmetric charge distribution on an insulating sphere before and after contact. Impingement induced damage and wear are investigated by chemical analysis microscopy in the analysis core facility on campus. The results are expected to gain a more profound insight into the mechanisms of contact electrification between inorganic materials.

尽管接触起电和摩擦起电已经被观察了2000多年，但其背后的物理机制仍然不清楚。然而，它不仅具有学术意义，而且在应用中具有重要意义。一方面，接触带电后的放电可能导致易燃液体或粉尘的严重爆炸。另一方面，有许多有用的目的，如废气净化等，我们已经开发出一种新的实验技术，使我们能够研究自由落体的球形颗粒和表面之间的电荷转移，具有前所未有的精度。它依靠自建电荷放大器提供< 1 fC和< 1 µs的分辨率。对金属之间的接触进行的实验表明，颗粒在接触期间放电，但当电接触断开时，在不到一微秒的时间内重新获得意想不到的高电荷。取决于撞击速度，电荷比哈珀和洛厄尔的普遍接受的模型预测的要高得多。提出了一个扩展模型，解释了基于接触的两个物体的变形的研究结果。包括接近底板的环形电极的初步实验证明了甚至增强的电荷分辨率。此外，扩展设置允许检测球体的质心和电荷中心之间的偏移。本计画的目标是分析金属（例如Au、Cu、Pt）之间、金属与氧化物（例如Si、InP、Al 2 O 3、ZrO 2）之间以及两种介电材料之间的接触起电的关键过程。该研究将集中在半导体和无机绝缘体，以解决在定义明确的表面和接触界面的电荷转移的内在电子状态的作用。该实验将在一个定制的UHV室中重新设计，该室允许研究真空下的接触带电以及定义的气体气氛。使用低能量电子束或紫外光，在接触之前调节绝缘电介质颗粒的表面电势。新设置测量电荷在后续接触中如何演变的能力应用于分析作为接触前冲击速度和电荷函数的电荷转移。通过改变材料，将研究接触电位，表面能带弯曲，材料的极化率和吸附层（如H2O）的存在对转移电荷的影响。环形电极的新实现将用于确定接触前后绝缘球上的任何不对称电荷分布。利用化学分析显微镜在校园分析中心设备上对冲击损伤和磨损进行了研究。研究结果有望对无机材料间的接触起电机理有更深刻的认识。