Transient Temperature During the Vaporization of Liquid on a Pulsed Laser-Heated Solid Surface

1996 ◽  
Vol 118 (3) ◽  
pp. 702-708 ◽  
Author(s):  
H. K. Park ◽  
X. Zhang ◽  
C. P. Grigoropoulos ◽  
C. C. Poon ◽  
A. C. Tam
Keyword(s):  
Thin Film ◽  
Solid Surface ◽  
Elevated Temperatures ◽  
Bubble Nucleation ◽  
Transient Temperature ◽  
Specular Reflectance ◽  
Transient Temperature Field ◽  
Excimer Laser Pulse ◽  
Nanosecond Time Resolution ◽  
Laser Heated

The thermodynamics of the rapid vaporization of a liquid on a solid surface heated by an excimer laser pulse is studied experimentally. The transient temperature field is measured by monitoring the photothermal reflectance of an embedded thin film in nanosecond time resolution. The transient reflectivity is calibrated by considering a temperature gradient across the sample based on the static measurements of the thin film optical properties at elevated temperatures. The dynamics of bubble nucleation, growth, and collapse is detected by probing the optical specular reflectance. The metastability behavior of the liquid and the criterion for the onset of liquid–vapor phase transition in nanosecond time scale are obtained quantitatively for the first time.

Study on Embedding and Integration of Microsensors Into Metal Structures for Manufacturing Applications

2006 ◽  
Vol 129 (2) ◽  
pp. 416-424 ◽  
Author(s):  
Xudong Cheng ◽  
Arindom Datta ◽  
Hongseok Choi ◽  
Xugang Zhang ◽  
Xiaochun Li
Keyword(s):  
Thin Film ◽  
Real Time ◽  
Temporal Resolution ◽  
Elevated Temperatures ◽  
Transient Temperature ◽  
Manufacturing Processes ◽  
Metal Structures ◽  
Metal Tooling ◽  
Critical Locations

Real time monitoring, diagnosis, and control of numerous manufacturing processes is of critical importance in reducing operation costs, improving product quality, and shortening response time. Current sensors used in manufacturing are normally unable to provide measurements with desired spatial and temporal resolution at critical locations in metal tooling structures that operate in hostile environments (e.g., elevated temperatures and severe strains). Microsensors are expected to offer tremendous benefits for real time sensing in manufacturing processes. Rapid tooling, a layered manufacturing process, could allow microsensors to be placed at any critical location in metal tooling structures. However, a viable approach is needed to effectively integrate microsensors into metal structures during the process. In this study, a novel batch production of metal embedded microsensor units was realized by transferring thin-film sensors from silicon wafers directly into nickel substrates through standard microfabrication and electroplating techniques. Ultrasonic metal welding (USMW) was studied to obtain optimized process parameters and then used to integrate nickel embedded thin-film thermocouple (TFTC) units into copper workpieces. The embedded TFTCs successfully survived the welding tests, validating that USMW is a viable method to integrate microsensors to metallic tool materials. Moreover, the embedded microsensors were also able to measure the transient temperature in situ at 50μm directly beneath the welding interface during welding. The transient temperatures measured by the metal embedded TFTCs provide strong evidence that the heat generation is not critical for weld formation during USMW. Metal embedded microsensors yield great potential to improve fundamental understanding of numerous manufacturing processes by providing in situ sensing data with high spatial and temporal resolution at critical locations.

Transient Optical Transmission Measurement in Excimer-Laser Irradiation of Amorphous Silicon Films

1993 ◽  
Vol 115 (1) ◽  
pp. 178-183 ◽  
Author(s):  
H. K. Park ◽  
X. Xu ◽  
C. P. Grigoropoulos ◽  
N. Do ◽  
L. Klees ◽  
...  
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Amorphous Silicon ◽  
Laser Irradiation ◽  
Excimer Laser ◽  
Optical Transmission ◽  
Elevated Temperatures ◽  
Transient Temperature ◽  
Transmission Measurement ◽  
Excimer Laser Irradiation

The transient temperature field development during heating of an amorphous silicon (a-Si) film, deposited on a fused quartz substrate, by pulsed excimer laser irradiation is studied. Static reflectivity and transmissivity measurements are used to obtain the thin film optical properties at elevated temperatures. Experimental in-situ, transient, optical transmission data are compared with heat transfer modeling results. The variation with temperature of the material complex refractive index across the thin film thickness is taken into account. The effects of the film thickness and thermal diffusivity, as well as of the laser pulse shape, are discussed.

Transient Temperature and Heat Flux Measurement in Ultrasonic Joining of Battery Tabs Using Thin-Film Microsensors

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Hang Li ◽  
Hongseok Choi ◽  
Chao Ma ◽  
Jingzhou Zhao ◽  
Hongrui Jiang ◽  
...  
Keyword(s):  
Thin Film ◽  
Heat Flux ◽  
Heat Generation ◽  
Welding Process ◽  
Ultrasonic Welding ◽  
Transient Temperature ◽  
Monitoring And Control ◽  
Change Rate ◽  
Flux Change ◽  
And Control

Process physics understanding, real time monitoring, and control of various manufacturing processes, such as battery manufacturing, are crucial for product quality assurance. While ultrasonic welding has been used for joining batteries in electric vehicles (EVs), the welding physics, and process attributes, such as the heat generation and heat flow during the joining process, is still not well understood leading to time-consuming trial-and-error based process optimization. This study is to investigate thermal phenomena (i.e., transient temperature and heat flux) by using micro thin-film thermocouples (TFTC) and thin-film thermopile (TFTP) arrays (referred to as microsensors in this paper) at the very vicinity of the ultrasonic welding spot during joining of three-layered battery tabs and Cu buss bars (i.e., battery interconnect) as in General Motors's (GM) Chevy Volt. Microsensors were first fabricated on the buss bars. A series of experiments were then conducted to investigate the dynamic heat generation during the welding process. Experimental results showed that TFTCs enabled the sensing of transient temperatures with much higher spatial and temporal resolutions than conventional thermocouples. It was further found that the TFTPs were more sensitive to the transient heat generation process during welding than TFTCs. More significantly, the heat flux change rate was found to be able to provide better insight for the process. It provided evidence indicating that the ultrasonic welding process involves three distinct stages, i.e., friction heating, plastic work, and diffusion bonding stages. The heat flux change rate thus has significant potential to identify the in-situ welding quality, in the context of welding process monitoring, and control of ultrasonic welding process. The weld samples were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to study the material interactions at the bonding interface as a function of weld time and have successfully validated the proposed three-stage welding theory.

Mechanisms for Defect Creation and Removal in Hydrogenated and Deuterated Amorphous Silicon Studied using Thin Film Transistors

2006 ◽  
Vol 910 ◽  
Author(s):  
Andew Flewitt ◽  
Shufan Lin ◽  
William I Milne ◽  
Ralf B Wehrspohn ◽  
Martin J Powell
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Threshold Voltage ◽  
Thin Film Transistors ◽  
Elevated Temperatures ◽  
Chemical Vapour ◽  
Rf Plasma ◽  
Gate Bias ◽  
Removal Process ◽  
Defect Creation

AbstractIt has been widely observed that thin film transistors (TFTs) incorporating an hydrogenated amorphous silicon (a-Si:H) channel exhibit a progressive shift in their threshold voltage with time upon application of a gate bias. This is attributed to the creation of metastable defects in the a-Si:H which can be removed by annealing the device at elevated temperatures with no bias applied to the gate, causing the threshold voltage to return to its original value. In this work, the defect creation and removal process has been investigated using both fully hydrogenated and fully deuterated amorphous silicon (a-Si:D) TFTs. In both cases, material was deposited by rf plasma enhanced chemical vapour deposition over a range of gas pressures to cover the a-g transition. The variation in threshold voltage as a function of gate bias stressing time, and annealing time with no gate bias, was measured. Using the thermalisation energy concept, it has been possible to quantitatively determine the distribution of energies required for defect creation and removal as well as the associated attempt-to-escape frequencies. The defect creation and removal process in a-Si:H is then discussed in the light of these results.

A New Postulation of Viscosity and Its Application in Computation of Film Thickness in TFL1

2002 ◽  
Vol 124 (4) ◽  
pp. 811-814 ◽  
Author(s):  
Chaohui Zhang ◽  
Jianbin Luo ◽  
Shizhu Wen
Keyword(s):  
Thin Film ◽  
Experimental Data ◽  
Film Thickness ◽  
Solid Surface ◽  
Contact Area ◽  
Elastohydrodynamic Lubrication ◽  
Thin Film Lubrication ◽  
Lubrication Film ◽  
Viscosity Modification ◽  
Film Lubrication

In this paper, a viscosity modification model is developed which can be applied to describe the thin film lubrication problems. The viscosity distribution along the direction normal to solid surface is approached by a function proposed in this paper. Based on the formula, lubricating problem of thin film lubrication (TFL) in isothermal and incompressible condition is solved and the outcome is compared to the experimental data. In thin film lubrication, according to the computation outcomes, the lubrication film thickness is much greater than that in elastohydrodynamic lubrication (EHL). When the velocity is adequately low (i.e., film thickness is thin enough), the pressure distribution in the contact area is close to Hertzian distribution in which the second ridge of pressure is not obvious enough. The film shape demonstrates the earlobe-like form in thin film lubrication, which is similar to EHL while the film is comparatively thicker. The transformation relationships between film thickness and loads, velocities or atmosphere viscosity in thin film lubrication differ from those in EHL so that the transition from thin film lubrication to EHL can be clearly seen.

scholarly journals Simulating Convective-Radiative Heat Sinks Effect by means of FEA-based Gaussian Heat Sources and Its Approximate Analytical Solutions for Semi-Infinite Body

2021 ◽  
Author(s):  
Ninh The Nguyen ◽  
John H Chujutalli
Keyword(s):  
Temperature Field ◽  
Heat Source ◽  
Analytical Solutions ◽  
Radiative Heat ◽  
Source Model ◽  
Heat Sinks ◽  
Transient Temperature ◽  
Measured Temperature ◽  
Heat Source Model ◽  
Transient Temperature Field

Abstract FEA-based Gaussian density heat source models were developed to study the effect of convective and radiative heat sinks on the transient temperature field predicted by the available approximate analytical solution of the purely conduction-based Goldak’s heat source. A new complex 3D Gaussian heat source model, incorporating all three modes of heat transfer, i.e., conduction, convection and radiation, has been developed as an extension of the Goldak heat source. Its approximate transient analytical solutions for this 3-D moving heat source were derived and numerically benchmarked with the available measured temperature & weld pool geometry data by Matlab programming with ~5 to 6 times faster than FEA-based simulation. The new complex 3D Gaussian heat source model and its approximate solution could significantly reduce the computing time in generating the transient temperature field and become an efficient alternative to extensive FEA-based simulations of heating sequences, where virtual optimisation of a melting heat source (i.e. used in welding, heating, cutting or other advanced manufacturing processes) is desirable for characterisation of material behaviour in microstructure evolution, melted pool, microhardness, residual stress and distortions.

scholarly journals The Effects of Surfactant on the Evolution of a Thin Film under a Moving Liquid Drop

2020 ◽  
Vol 5 (1) ◽  
pp. 75-85
Author(s):  
Kartika Yulianti ◽  
Agus Yodi Gunawan ◽  
Edy Soewono
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Solid Surface ◽  
Surfactant Concentration ◽  
Liquid Drop ◽  
Nonlinear Partial Differential Equations ◽  
Normal Pressure ◽  
Lubrication Approximation ◽  
Moving Liquid

The effect of surfactant on the thickness of a thin film bounded by a solid surface and a moving liquid drop was investigated. We proposed a model so that parameters from the liquid drop can be stated in a parameter that acts as normal pressure to the thin film. Using the lubrication approximation, the model was reduced to a set of nonlinear partial differential equations in terms of the film thickness and surfactant concentration. Since we were interested in the role of the surfactant in lifting up the drop, we assumed that the density of the drop is higher than the density of the thin film. Numerically, the results show that the presence of the surfactant tends to delay the decrease of the film thickness insignificantly. However, when the surfactant was added into the system, it tends to significantly increase the film thickness for a certain range value of the normal pressure.

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