Search

Graphene sheets are synthesized by a simple method starting from graphitic oxide as a precursor. Reaction of graphitic oxide at 250 °C with a combustion mixture of urea and ammonium nitrate results in the formation of thin graphene sheets. Graphene formation is characterized by XRD, TGA, XPS and TEM. Graphene materials synthesized by this method are investigated as an ultracapacitor material. Specific capacitance values of about 70 F/g are obtained at a current density of 100 mA/g by using KOH as an electrolyte. [ABSTRACT FROM AUTHOR]

Gallium nitride cantilevers with metal-insulator-semiconductor capacitors were fabricated and characterized as a function of strain to determine the effective piezoelectric constant. These cantilevers were tested at room temperature through a combination of cantilever bending experiments, strain gauge measurements, and finite element modeling. By measuring the shift in flatband voltage to applied strain the magnitude of the piezoelectric charge induced is determined. The effective piezoelectric constant e31′ was determined from these measurements to be -0.57±0.03 C/m2. [ABSTRACT FROM AUTHOR]