鎳-磷-鑽石奈米複合材料之複合效應於材料特性差異上的研究

Abstract

先前我們已經發表過在鎳基材中摻入如二氧化矽、鑽石、碳管等奈米微粒可以改變鎳金屬的機、電特性。這些特性的改善使得奈米複合材料在微機電的應用上具有很大的發展性。為了更進一步的應用這些奈米複合材料、有效控制材料特性來製作元件，我們必需對複合材料特性做更深入的研究，了解在奈米微粒不同粒徑、外型及在基材中不同的分怖情形時所造成的特性差異。到目前為止，只有少數的研究針對這些問題去做探討。在本篇論文中將報告一個在鎳-磷-鑽石奈米複合材料中觀察到的有趣現象，即在摻雜相同的二相材料進入不同微結構的鎳基材時將產生不同的材料特性變化。奈米壓痕儀的量測結果指出，在奈米鑽石微粒體積百分比4%含量下且微結構為非晶型態的鎳-磷-鑽石複合材料薄膜其硬度值從純鎳-磷薄膜的6.7GPa提升到7.5GPa，反觀微結構由非晶及奈米晶粒所組成的鎳-磷-鑽石薄膜其硬度值隨著奈米鑽石微粒含量的增加能下降。同時，量測每公升鍍液裡有2克的奈米鑽石微粒溶液中鍍出來的鎳-磷-鑽石複合材料薄膜電性可以發現，非晶結構的鎳-磷-鑽石複合材料比微結構為非晶及奈米晶粒所組成的鎳-磷-鑽石複合材料有更好的導電性，其相對應的量測電阻率分別為1.125*10-6Ω-m及1.561*10-6Ω-m。另一方面，由鎳-磷-鑽石複合材料所製成的電熱式微致動器，無論在何種微結構下其最大位移量均比由純鎳-磷材料所製成的微致器來的大，此外，非晶型態的鎳基材電熱式微致動器比微結構為非晶及奈米晶粒所組成的鎳基材微致動器有更佳的電源效率。我們相信這些觀察到的現象將引起材料學者及元件工程師在複合材料的理論研究及應用上的興趣。

Previously, we have reported that incorporating nanoparticles, such as SiO2, diamond, and carbon nanotube (CNT) into a nickel matrix can change the mechanical and electrical properties of pure nickel. The property modifications have shown a great potentiality of the nanocomposites for MEMS applications. However, for the advancement of the applications, it is required to further investigate on the material property modification resulted by nanocomposite effects, such as particle size, shape, and distribution effects on the matrix, from which the material properties can be well engineered for designated device fabrication. So far, few researches have been worked on the related issues. In the thesis, an interesting phenomenon is observed and reported in Ni-P-Diamond nanocomposite system, in which the microstructure difference of Ni matrix would result in distinct property modifications even though the same second phase material is added. The nanoindentation measurement shows that the Young’s modulus and harness of the amorphous crystallization of the Ni-P films can increase from 6.7Gpa to 7.5Gpa while 4% volume fraction of nano-diamonds are incorporated. In contrast, the modulus and hardness of the Ni-P films with a mixed microstructure of nanocrystalline and amorphous phase decrease with the incorporation of the nano-diamonds. Meanwhile, from the electrical measurements of the 2g/L Ni-P-Diamond nanocomposite films, it is found that the resistivities of these two Ni-P-Diamond nanocomposites are 1.125*10-6Ω-m and 1.561*10-6Ω-m, respectively for an amorphous matrix and a matrix with the mixtures of nanocrystalline and amorphous phase, which indicating the Ni-P-Diamond nanocomposite with amorphous Ni matrix has better electrical conductivity than the other. Since it is found that the electrothermal microactuator made of both Ni-P-Diamond nanocomposites can exhibit a larger ultimate elongation than that made of pure Ni-P and the actuator made of the nanocomposite with fully amorphous Ni matrix can have a better power-efficient performance as compared, it is our belief that the observations would lead a great interest to material scientists and device engineers in the future development of nanocomposite synthesis and theory.