Summary
It is commonly known that the carbon micro coil (CMC), a coiled carbon material, has a helical structure and is superior to other carbon materials in radio wave absorbability, tactile and proximity sensitivity, and elasticity. These properties of CMC are attributed to its peculiar coiled structure. However, it is difficult to use CMC as a micro device or functional composite device, because CMC has low mechanical strength and electric conductivity. Thus, the development of highly elastic springs that overcome these disadvantages was sought.
The aim of our research was to provide a method for producing ceramic springs that have a linear spring axis with high elasticity and mechanical strength. In our research we developed single-strand TiN and TiC micro-springs that have high strength, hardness, and melting points as ceramics, as well as high electric conductivity as metals. Our springs also provide mechanical (elasticity) and electrical properties suitable for springs, as well as various other useful properties such as coil chirality and excellent electromagnetic properties. Our research enabled the development of multi-functional ceramic materials for springs for the first time in the world.
Research Achievements
1. Synthesis
The ceramic spring material used in our research was synthesized in large amounts by thermal CVD using iron-based catalysts.
2. Shape
We developed ceramic springs made of helical strands. Unlike conventional double coiled springs, in which two strands entwine around each other, they are single strand springs (dextral or sinistral). Their axis is almost a straight line, their diameter is 0.5 to 4.0 μm, and they have a spring pitch of 0.1 to 3.0 μm. Furthermore, they grow in length to 0.5 to 2.0 mm in just two hours.
3. Physical Properties
The ceramic springs in our research extend to more than 1.5 times their original length. We also developed two types of ceramic springs: the first contains titanium nitride (TiN) and is golden with a metallic luster, has a high melting point, and offers high hardness and electrical conductivity. The second contains titanium carbide (TiC) and is silver-colored with a metallic luster. It also has a high melting point and high hardness and electrical conductivity. The resistivity of the TiN spring is 1.13 ´ 10-5 W∙m while that of the TiC spring is 4.3 ´ 10-5 W∙m. Since these springs are elastic and have strong mechanical strength, they are suitable for use in a wide variety of electronic products. The uniform dispersal of CMSs into elastic resin (such as silicone resin) to form composite materials enables the manufacture of simple-structured functional elastic composite materials. They can easily be made micro-sized and into thin films, and be used as high-performance functional materials in sensors and radio-wave absorbers.
4. Prospective Applications
Our ceramic springs can be applied as bulk bodies to sensors, radio-wave absorbers, actuators, cancer treatment, catalyst holders, and three-dimensional strengthening composite materials.
As spring components, they can be applied to micro springs, micro-electro mechanical systems (MEMS), energy transformers, capacitors, inductors, actuators, and sensors (for detecting force, pressure, and electric and magnetic fields).
