Strain Gauge Based on Graphene

In this paper, graphene grown by Chemical vapor deposition (CVD) on a Cu foil in a cold-wall furnace was used to fabrication the graphene strain gauge. The graphene membrane was patterned to wire grid shape on the Cu substrate by photolithography method in the clean room. The pattern was transferred to PDMS substrate and seal by it also to make graphene in a stable surroundings. Through the standard calibration, it was calculated that the linearity and multiplicity of the graphene strain gauge both were 0.0076%F.S.. Which indicated the good quality of the gauge. The gauge factor was 2.4, as the highest value as that of the alloy strain gauge. We also find the graphene strain gauge output increase proportionally with increasing curvature of its deformation.

In Vitro Bioactivity of Atomic Layer Deposited Titanium Dioxide on Titanium and Silicon Substrates

A non-bioactive implant device can easily be changed to in vitro bioactive with a thin coating of crystalline TiO2. This crystalline coating can be deposited very thin with great step coverage at a low temperature with Atomic Layer Deposition (ALD). An anatase TiO2 coating was built up atomic layer by atomic layer using TiI4 and H2O as precursors in a hot wall furnace. Several hundreds of cycles resulted in a 10-30nm well defined TiO2 of anatase phase on both Si and Ti substrates. These coatings were shown to be bioactive when immersed in simulated body fluid in vitro, as hydroxyapatite (HA) formed on the surface. The surface roughness of the substrates affected the adhesion of the HA. The adhesion was low on the smooth Si but much better on the 100 times rougher Ti. The ALD technique is promising for coating substrates of all shapes with bioactive crystalline TiO2 at a low temperature.

Numerical Modeling of a Double Fired Process Heater With Different Internal Wall Configurations

A double fired process heater with combination oil/gas burners has been modeled with computational fluid dynamics (CFD). The process heater was simulated with two configurations: 1) with internal walls, and 2) without internal walls. The purpose of this study is to understand the effect of the internal walls on flame shape and process tube heat flux. As a result of removing the internal wall, furnace currents are allowed to have a large influence on the flame patterns and the flames lean toward the tubes. It is also shown that higher localized heat fluxes occur on the process tubes with the walls removed. This study demonstrates that the primary function of the internal walls is to isolate cells within the furnace which create satisfactory process tube heat fluxes.

Rapid Thermal Oxidation of Silicon in Mixtures of Oxygen and Nitrous Oxide

Oxidation in nitrous oxide by conventional hot wall furnace processing and by rapid thermnal oxidation (RTO) has been a subject of much interest in recent years. RTO is a fundamentally different process than furnace oxidation, however, and the full effects of this type of processing on the oxidation kinetics are not well understood. Oxidation of silicon by RTO at a variety of pressures, temperatures, and oxidation gas mixtures has been studied. Although at lower temperatures (<850°C) the atmospheric pressure oxidation rate in nitrous oxide is very close to that in oxygen, at higher temperatures the oxidation rate in nitrous oxide is much lower than that in oxygen. At lower pressures in a RTO process, the oxidation rate in nitrous oxide is higher than that in oxygen. The effect of the nitrogen incorporated in the oxide acting as a diffusion barrier has been proposed as the mechanism of temperature dependence for atmospheric pressure oxidation in nitrous oxide. This does not explain the effects seen at lower pressures, however. We propose that some of the intermediate species produced in the decomposition of nitrous oxide into molecular nitrogen, molecular oxygen, and nitric oxide play a role in the initial stages of oxidation by RTO in nitrous oxide.