Measurement of heat capacity of al thin film using a micro bridge calorimeter

A microcalorimeter was fabricated with combination of IC technology and silicon surface micro-fabrication technology. The device has good manufacturing yield and precisely controlled pattern size compared to the bulk micro-machined one. In vacuum with heating power of 5.5 mW, the temperature of the micro calorimeter rises from 300 K to 400 K in 0.5 ms, and the heating rate is up to 2 × 10⁵K/s. According to the characteristics of small thermal mass and fast heating rate of the microcalorimeter, pulse calorimetry was introduced to measure the heat capacity of thin films. Heat capacity of Al thin film with thickness of (430 ± 20)nm was measured from 300 K to 420 K. Result shows that heat capacity of the Al film is 9.2 nJ/K at room temperature. If the density of the film is 2700 kg/m³, then the specific heat capacity of the film is about 1096.8 J/(kg·K). It is 21.9% larger than the specific heat capacity of the bulk Al of 900 J/(kg·K), which indicates the enhancement of specific heat capacity of nanocrystalline metals

Investigation on measurement of micro gas sensor stability

The stability of a series of micro hotplate based gas sensors were investigated and the descriptive methods were discussed in focus. From the point of statistics, the general feature parameters to denote gas sensors' stability were compared and an optimal parameter set was extracted. The variation coefficient of parameters was adopted to describe the stability. By using this approach, the influences of preheating time on gas sensors' stability were investigated

Assembly of centimeter long silica coated FePt colloid crystals with tailored interstices by magnetic crystallization

A bottom-up approach for the first synthesis of centimeter long magnetic colloidal crystals, which have adjustable internal interstices for potential use in magnetic gradient separation of chemical or biochemical entities was investigated. The large colloidal crystals were composed of three-dimensional regular arrays of superparamagnetic FePt nanoparticle encapsulated in a protective hydrophilic silica shell with controllable thickness. The powder sample was washed four times in pure ethanol to remove impurities. It was then placed in an ultrasonic bath for 1 hour with 100 mL of ethanol in a 150 mL beaker at 55°C for controlled crystallization. It was observed that the ability to assemble silica coated magnetic nanoparticles into high quality colloid crystals from the bottom-up construction approach through magnetic crystallization could open up a new avenue for preparing new porous magnetic crystals with high surface area for potential separation of chemicals or biochemicals of a wide range of interests