Thermodiffusion phenomena

Costesèque, P.; Mojtabi, Abdelkader

doi:10.1016/j.crme.2011.03.001

Cited by 30 publications

(21 citation statements)

References 35 publications

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“…In the empirical description of transport by thermal diffusion, because of the complexity of this process when the temperature gradient (▽ T ) creates an additional driving force to the concentration gradients (▽ C ), the Ludwig–Soret effect can be taken into account. In this case, the formulae can be used to express the flux linking to thermal diffusion:

J = - ρ D \nabla C - ρ F (C) D_{T} \nabla T or J = - D {\nabla C + C (Q / k T) (\nabla T / T)}

i.e., two temperature gradient‐driven phenomena can be outlined: D ▽ C – flux of depositing and diffusing atoms caused by their non‐uniform spatially distributed concentration due to temperature spatial non‐uniformity; DC ( Q/kT )(▽ T/T ) – clear expression of the Ludwig–Soret effect in crystalline solids.

J = - s D [\partial C_{normali} / \partial x + k_{normals} \partial (\ln (T - T^{normalz})) / \partial x + k_{normalp} \partial P / \partial x],

where D ( C , T , t ) is the diffusivity, s ( T , t ) is the solubility, k s ( C , T , t ) is the “Soret effect” factor providing diffusion because of temperature gradient, and k p ( c , T , t ) is the pressure stress factor. The temperature gradient can be created at thermal treatment resulting in the independent driving force for the concentration gradient.…”

Section: Thermal Diffusion Boronizing Process For the Coatings Formationmentioning

confidence: 99%

Formation of Corrosion‐Resistant Thermal Diffusion Boride Coatings

Medvedovski¹

2015

Adv Eng Mater

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The corrosion related issues in oil production can be significantly reduced using the coatings based on the compounds from the metals of the IVb-VIb and VIII groups and the non-metallic elements of the IIIa-Va groups with strong covalent bonds and high thermodynamic potentials. Iron boride-based coatings with consolidated structures are successfully applied through the thermal diffusion process to protect large production components from steels and ferrous alloys. The principles of the thermal diffusion coating formation are reported. The Fe-B-based coatings successfully withstand high temperaturehigh pressure water steam contained H 2 S, CO þ CO 2 , hydrocarbons, chlorides in simulating oil field conditions tested in the autoclave and in the pressurized Atlas cell, and in strong acidic environments.

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J = - ρ D \nabla C - ρ F (C) D_{T} \nabla T or J = - D {\nabla C + C (Q / k T) (\nabla T / T)}

J = - s D [\partial C_{normali} / \partial x + k_{normals} \partial (\ln (T - T^{normalz})) / \partial x + k_{normalp} \partial P / \partial x],

Section: Thermal Diffusion Boronizing Process For the Coatings Formationmentioning

confidence: 99%

Formation of Corrosion‐Resistant Thermal Diffusion Boride Coatings

Medvedovski¹

2015

Adv Eng Mater

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“…By contrast, recently developed ionic thermoelectric sensors 26 can provide self-generated open-circuit voltages that are stable over time. A drawback is that ionic thermoelectric voltages do not correspond only to the temperature of a single target sensor spot, but they are induced by a temperature gradient between two different positions 27 . No signal is obtained upon uniform heating of the whole material or device.…”

Section: Introductionmentioning

confidence: 99%

Ultrasensitive electrolyte-assisted temperature sensor

et al. 2020

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Heat sensors form an important class of devices that are used across multiple fields and sectors. For applications such as electronic skin and health monitoring, it is particularly advantageous if the output electronic signals are not only high, stable, and reproducible, but also self-generated to minimize power consumption. Here, we present an ultrasensitive heat sensing concept that fulfills these criteria while also being compatible with scalable low-cost manufacturing on flexible substrates. The concept resembles a traditional thermocouple, but with separated electrodes bridged by a gel-like electrolyte and with orders of magnitudes higher signals (around 11 mV K−1). The sensor pixels provide stable and reproducible signals upon heating, which, for example, could be used for heat mapping. Further modification to plasmonic nanohole metasurface electrodes made the sensors capable of also detecting light-induced heating. Finally, we present devices on flexible substrates and show that they can be used to detect human touch.

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“…The first term of this equation comes from Fick's law and the second term describes the Soret effect (thermodiffusion). VC is the mass fraction gradient induced by the temperature gradient, VT, [3]. Although, the assumption C(1 À C)z C 0 (1 À C 0 ), where C 0 is the initial value of the mass fraction, is widely used, it remains valid within the limits of very small variations of the mass fraction around C 0 .…”

Section: Introductionmentioning

confidence: 99%