• Journal of Mechanical Science and Technology
• /
• 제17권12호
• /
• pp.2078-2086
• /
• 2003

As technology advances with development of new materials, it is important to measure the thermal diffusivity of material and to predict the heat transfer in the solid subject to thermal processes. The measurement of thermal properties can be done in a non-contact way using photothermal displacement spectroscopy. In this work, the thermal diffusivity was measured by analyzing the magnitude and phase of deformation gradient. We proposed a new data analysis method based on the real part of deformation gradient as the pump-probe offset value. As the result, compared with the literature value, the measured thermal diffusivities of materials showed about 3 % error.

• 대한기계학회논문집B
• /
• 제27권6호
• /
• pp.804-812
• /
• 2003

This paper introduces optical methods for in-situ measurement of surface temperature and pressure transient in thermal processes having nanosecond time scales. In the temperature measurement, a p -Si thin film whose refractive index is calibrated as a function of temperature is embedded beneath the sample surface and the photothermal reflectance is monitored for estimating the surface temperature. The pressure transients are measured using the photoacoustic optical deflection method. The experimental technique is used to analyze the nanosecond laser induced vaporization process that is central to numerous engineering and bio-medical applications. Based on the experimental results, discussions are made on the experimental technique and the physical mechanisms of laser-driven explosive vaporization phenomena.

• 대한기계학회논문집B
• /
• 제26권12호
• /
• pp.1747-1755
• /
• 2002

A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of the parameters, such as radius and modulation frequency of the heating beam and the thermal diffusivity, was studied. Usually, thermal diffusivity was determined by the deformation angle and phase angle as the relative position between the heating and probe beams. In this study, we proposed the simple analysis method based on the real part of deformation gradient as the relative position between two beams. It is independent in the parameters such as power of heating beam, absorption coefficient, reflectivity, Poisson's ratio, and thermal expansion coefficient.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.132-137
• /
• 2000

A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in solid materials. The influence of parameters - radius and modulation frequency of pump beam and thickness of material - on the phase lag was studied. The phase decreases up to a certain position, then starts to increase and does have an asymptotic value. The position, where phase has the minimum value, is a function of thermal diffusion length thickness of sample, and radius of pump beam. A new method based on minimum phase lag is described to determine the thermal diffusivity of solid material.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.138-143
• /
• 2000

A new method of measuring the thermal diffusivity of solid material at room temperature with photothermal displacement method is proposed. The influence of the parameters on phase lag was studied. From the minimum position of phase of measured deflection with respect to the pump beam the thermal diffusivity of the materials can be obtained. The minimum position of phase is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying new method are in good agreement with the literature values.

• 대한기계학회논문집B
• /
• 제29권1호
• /
• pp.27-34
• /
• 2005

We analyze in detail axially symmetric theoretical study for the photothermal pulsed radiometry of a cylindrical model. The theoretical solutions describe the transient infrared radiation from the sample heated by short-duration pulsed heating. In the conventional transmission radiometry technique, the excitation source and the detector are on opposite sides of the sample, otherwise in the new single ended radiometry technique, the excitation source and the detector are on same sides of the sample. The analytical solution described for photothermal radiometry in this study would not need to cut or polish samples to measure the thermal diffusivity. Therefore the radial area and axial thickness of samples are not limited. The effects of excitation pulse duration and the area of heat source are discussed.

• Medical Lasers
• /
• 제8권2호
• /
• pp.97-100
• /
• 2019

Facial pores are a visible topographic feature of skin surfaces and are generally the enlarged openings of pilosebaceous follicles. Enlarged facial pores can be a significant cosmetic problem, particularly for women. Recently, gold nanoshell-mediated photothermal therapy (PTT) has been reported to be effective in treating recurrent acne. The treatment of enlarged facial pores with gold nanoshell-mediated PTT produced excellent results with no side effects. The two cases reported here demonstrate the possibility of gold nanoshell-mediated PTT as a safe and effective treatment for enlarged facial pores.

• 전기전자학회논문지
• /
• 제22권1호
• /
• pp.213-215
• /
• 2018

본 연구에서는 실리콘 기판 위에 DC 스퍼터링 방법을 이용하여 비정질 탄소박막을 제작하고, 흡광특성과 광발열 특성을 조사하였다. 비정질 탄소박막은 1000 nm 파장에서 97%의 흡광도를 보였으며, 백색광이 조사됨에 따라 비정질 탄소박막의 온도는 $21.1^{\circ}C$에서 $24.1^{\circ}C$로 상승하여 약 $3^{\circ}C$의 온도가 증가하였다. 또한, 백색광이 50초 동안 조사되는 동안 비정질 탄소박막에서는 기판에 비해 4배 빠른 온도상승속도로 온도가 증가하였다.

• 대한기계학회논문집B
• /
• 제27권9호
• /
• pp.1220-1228
• /
• 2003

The mirage technique is proved to be powerful in measuring the thermal diffusivity of materials. In particular, its contactless nature makes it suitable for delicate samples and microscale structures. In this study, thermal-wave-coupling method is developed in a general form for both thermally thin and thick samples. In the suggested measuring scheme, the probe beam can be positioned close to the pump beam and the absolute position need not be measured. Therefore the new scheme provides a relatively simple yet effective way to determine the thermal diffusivity of thermally thick samples. Thermal diffusivities of bulk samples like Ni and Al were measured and the characteristics of mirage signal for a thin film were observed by using the mirage experimental setup. The apparent thermal diffusivity was measured by varying such parameters as probe beam height, size of pump beam, power of pump beam, and surface condition of sample. From the practical standpoint, it is shown that the size of the pump beam is the most important factor for accurate thermaldiffusivity measurement. Experiments using thin-film samples show that the thermal diffusivity of a substrate covered with thin film can be measured by photothermal mirage signals.

• 대한기계학회논문집B
• /
• 제25권3호
• /
• pp.296-304
• /
• 2001

A new method of measuring the thermal diffusivity of solid material at room temperature using photothermal displacement is proposed. The influence of the parameters, such as radius and modulation frequency of the pump beam and the sample thickness, was studied. From the minimum position of phase of measured deflection with respect to the pump beam, the thermal diffusivity of the materials can be obtained. The position where phase has the minimum value is determined using multiparameter least-square regression fitting. The experimental values for different samples obtained by applying the new method are in good agreement with the literature values.