Byeong Jun Lee

How to optically count graphene layers.

The total thickness of a graphene sample depends upon the number of individually stacked graphene layers. The corresponding surface plasmon resonance (SPR) reflectance alters the SPR angle, depending on the number of graphene layers. Thus, the correlation between the SPR angle shift and the number of graphene layers allows for a nonintrusive, real-time, and reliable counting of graphene layers. A single-layer graphene (SLG) is synthesized by means of chemical vapor deposition, followed by physical transfer to a thin gold film (48 nm) repeatedly, so that multilayer graphene samples with one, three, and five layers can be prepared. Both the measured SPR angles and the entire reflectance curve profiles successfully distinguish the number of graphene layers.

Measurement of gas calorific value using electric substitution method

The calorific value is defined as the amount of heat which would be released by the complete combustion in air, in such a way that the pressure remains constant, all the combustion products except water are gaseous states and all the products returned to the temperature of the reactants. Recently, the mixed fuel like LPG, LNG, hythane, etc., become more popular. But the composition of these fuels changes with time and place where it was produced, which give direct impacts on the calorific value and performance of the heating apparatus. Therefore, the accurate measurements of the calorific value become an issue in the refinery industries and the national standardization fields. So, flame calorimeter was manufactured and characterized to measure calorific value of the gaseous fuel in the flow situations. Electric substitution method initiated by Alexandrov was adopted. Peltier elements were used to emit the heat supplied by a heater and a flame to the cooling water. Freon-11 was used as a heat carrier. To get the accurate calorific value by the experiments conducting in the normal laboratory conditions, correction methods were proposed to count variations in the experimental conditions such as temperatures, electric powers, etc. It was found out that the corrected calorific value of pure methane had 0.36% relative deviation to the standard value.

Investigation of Gas Heating by Nanosecond Repetitively Pulsed Glow Discharges Used for Actuation of a Laminar Methane-Air Flame

ABSTRACT This article reports on the quantification of the heating induced by nanosecond repetitively pulsed (NRP) glow discharges on a lean premixed methane-air flame. The flame, obtained at room temperature and atmospheric pressure, has an M-shape morphology. The equivalence ratio is 0.95 and the thermal power released by the flame is 113 W. The NRP glow discharges are produced by high voltage pulses of 10 ns duration, 7 kV amplitude, applied at a repetition frequency of 10 kHz. The average power of the plasma, determined from current and voltage measurements, is 1 W, i.e., about 0.9% of the thermal power of the flame. Broadband vibrational coherent anti-Stokes Raman spectroscopy of nitrogen is used to determine the temperature of the flame with and without plasma enhancement. The temperature evolution in the flame area shows that the thermal impact of NRP glow discharges is in the uncertainty range of the technique, i.e., ±40 K.