Microreactors for Thin-Film Calorimetry

2002 ◽  
Vol 741 ◽  
Author(s):  
J. Rodríguez-Viejo ◽  
M. Chacón ◽  
A.F. Lopeandía ◽  
M.T. Clavaguera-Mora ◽  
Leonel R. Arana ◽  
...  
Keyword(s):  
Heat Capacity ◽  
High Vacuum ◽  
Transient State ◽  
High Sensitivity ◽  
Symmetric Design ◽  
Input Power ◽  
Cdse Nanocrystals ◽  
Thermal Mass ◽  
Heating Rates ◽  
Calorimetric Measurements

ABSTRACTWe have designed and developed a calorimeter that is capable of measuring the heat released by ultrathin films in the temperature range from 77 to 1050 K. Semiconductor processing techniques are used to fabricate the microreactors. The symmetric design of the Pt heaters in the microreactor channel provide a good temperature profile across the active region of the membrane making it suitable for accurate calorimetric measurements. The low thermal mass of our system allows for a high sensitivity. The effective heat capacity of the microcalorimeters with a 200 nm SixNy membrane is 0.14 μJ/K at room temperature. In high vacuum heating rates of 2×106 K/s have been achieved. Under these conditions the microcalorimeter works as an adiabatic scanning calorimeter and therefore heat capacity is directly obtained from the input power. A thermal characterization of the microcalorimeters in the transient state and calorimetric measurements on indium thin films and films made of CdSe nanocrystals are briefly discussed to show the potentiality of the microreactors.

An Ultrafast Thin-Film Microcalorimeter with Monola Yer Sensitivity (J/m2)

1995 ◽  
Vol 398 ◽  
Author(s):  
S.L. Lai ◽  
P. Infante ◽  
G. Ramanath ◽  
L.H. Allen
Keyword(s):  
Thin Film ◽  
Heating Rate ◽  
Current Pulse ◽  
High Sensitivity ◽  
Melting Process ◽  
Thermal Mass ◽  
Calorimetric Measurements ◽  
Calorimetric Technique ◽  
Dc Current ◽  
Thin Film Membrane

ABSTRACTWe introduce a high-sensitivity (∼1 J/m2) scanning microcalorimeter that can be used to perform direct calorimetric measurements on thin film samples at ultrafast heating rate (∼104 °C/s). This novel microcalorimeter is fabricated by utilizing SiN thin-film membrane technology, resulting in dramatically reduced thermal mass of the system. Calorimetric measurements are accomplished by applying a dc-current pulse to the thin-film metal (Ni) heater which also serves as a thermometer, and monitoring the real-time voltage and current of the heater. The temperature of the system and the energy delivered to the system are then determined. This calorimetric technique has been demonstrated by measuring the melting process of thin Sn films with thickness ranging from 13 to 1000 Å, and shows potential for calorimetric probing of irreversible reactions at interfaces and surfaces, as well as transformations in nanostructured materials.

scholarly journals Thermoelectric Photosensor Based on Ultrathin Single-Crystalline Si Films †

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1427 ◽  
Author(s):  
Gustavo Gonçalves Dalkiranis ◽  
Pablo Ferrando-Villalba ◽  
Aitor Lopeandia-Fernández ◽  
Llibertat Abad-Muñoz ◽  
Javier Rodríguez-Viejo
Keyword(s):  
Phonon Scattering ◽  
Ambient Pressure ◽  
High Vacuum ◽  
Laser Diodes ◽  
Argon Laser ◽  
High Sensitivity ◽  
Open Circuit ◽  
Thermal Mass ◽  
Slight Reduction ◽  
Si Films

Ultrathin Si films have a reduced thermal conductivity in comparison to Si bulk due to phonon scattering at the surfaces. Furthermore, the small thickness guarantees a reduced thermal mass (in the µJ/K range), which opens up the possibility of developing thermal sensors with a high sensitivity. Based on these premises, a thermoelectric (TE) microsensor based on ultrathin suspended Si films was developed and used as a thermal photosensor. The photoresponse of the device was evaluated with an argon laser (λ = 457 nm) with a variable power ranging from 0 to 10 mW in air at atmospheric pressure, with laser diodes at 406 nm, 520 nm and 638 nm wavelengths, and fixed powers in high vacuum conditions. The responsivity per unit area, response time (τ) and detectivity (D*) of the device were determined in air at ambient pressure, being 2.6 × 107 V/Wm2, ~4.3 ms and 2.86 × 10 7   c m H z ( 1 / 2 ) W − 1 , respectively. Temperature differences up to 30 K between the central hot region and the Si frame were achieved during open-circuit voltage measurements, with and without laser diodes. During illumination, the photogeneration of carriers caused a slight reduction of the Seebeck coefficient, which did not significantly change the sensitivity of the device. Moreover, the measurements performed with light beam chopped at different frequencies evidenced the quick response of the device. The temperature gradients applied to the thermoelectric Si legs were corrected using finite element modeling (FEM) due to the non-flat temperature profile generated during the experiments.

Recent Developments In Monochromatic Microprobe X-Ray Fluorescence (MMXRF)

1998 ◽  
Vol 4 (S2) ◽  
pp. 378-379
Author(s):  
Z. W. Chen ◽  
D. B. Wittry
Keyword(s):  
Materials Science ◽  
High Vacuum ◽  
Three Dimensional ◽  
High Sensitivity ◽  
X Rays ◽  
Fluorescence Excitation ◽  
X Ray ◽  
Quantitative Microanalysis ◽  
Recent Developments ◽  
Fifth Order

A monochromatic x-ray microprobe based on a laboratory source has recently been developed in our laboratory and used for fluorescence excitation. This technique provides high sensitivity (ppm to ppb), nondestructive, quantitative microanalysis with minimum sample preparation and does not require a high vacuum specimen chamber. It is expected that this technique (MMXRF) will have important applications in materials science, geological sciences and biological science.Three-dimensional focusing of x-rays can be obtained by using diffraction from doubly curved crystals. In our MMXRF setup, a small x-ray source was produced by the bombardment of a selected target with a focused electron beam and a toroidal mica diffractor with Johann pointfocusing geometry was used to focus characteristic x-rays from the source. In the previous work ∼ 108 photons/s were obtained in a Cu Kα probe of 75 μm × 43 μm in the specimen plane using the fifth order reflection of the (002) planes of mica.

scholarly journals Relationship Between Dynamic Thermal Properties, Energy Consumption and Comfort with Different Building Envelopes in a Canadian Building

2020 ◽  
Author(s):  
Alexandre Pépin ◽  
Louis Gosselin ◽  
Jonathan Dallaire
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Energy Consumption ◽  
Important Variable ◽  
Office Building ◽  
Quebec City ◽  
Thermal Mass ◽  
Building Envelopes ◽  
Heating And Cooling ◽  
Energy Intensities

An office building located in Quebec City (Canada) with different envelope assemblies has been simulated in order to determine the energy consumption and thermal comfort that they provide. The resistance, thermal mass, and materials (concrete, cross-laminated timbers (CLT), and light-frame) are varied in a series of 164 different scenarios and the energy intensities for heating and cooling determined in each case, along with the discomfort index. Results show that the materiel used to provide thermal mass has a larger impact on comfort and energy consumption than the value of the thermal mass thickness itself. It was also attempted to correlate the performance of the envelope and its thermal mass with three dynamic thermal properties (i.e., dynamic transmittance, areal heat capacity, and decrement factor). Apart from thermal resistance, the internal areal heat capacity appeared to be the most important variable to explain variations of performance of the envelope.

Measurement of the Thermal Properties of Innovative Highly-Insulating Non-Structural Concretes

2019 ◽  
Vol 390 ◽  
pp. 41-52 ◽  
Author(s):  
Milena Kušnerová ◽  
Marta Harničárová ◽  
Jan Valíček ◽  
Zuzana Palková ◽  
Zdenko Tkáč ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Mass Parameter ◽  
Thermal Characteristic ◽  
Cementitious Composites ◽  
Thermal Mass ◽  
Volumetric Heat Capacity ◽  
Materials Selection ◽  
Material Parameters ◽  
Measurement Results

Thermal characteristic of insulation concretes is one of the key components in materials selection especially in civil constructions. In this article, non–tabulated material parameters of some innovative highly-insulating non-structural concretes are presented. The specific volumetric heat capacity, specific heat capacity, parameter of temperature diffusivity and thermal mass parameter of the innovative highly-insulating cementitious composites were determined. The experiments were conducted using a prototype automated calorimetric chamber. The measurement results are compared with those obtained by using a commercial multifunctional instrument (Isomet 2114) and are accompanied by the measurement of other significant thermal parameters of the cementitious composites under investigation. The results indicated that there is potential of using the newly created types of concrete for insulation purposes.

scholarly journals Application of Differential Scanning Calorimetry (DSC) and Modulated Differential Scanning Calorimetry (MDSC) in Food and Drug Industries

Polymers ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 5 ◽  
Author(s):  
César Leyva-Porras ◽  
Pedro Cruz-Alcantar ◽  
Vicente Espinosa-Solís ◽  
Eduardo Martínez-Guerra ◽  
Claudia I. Piñón-Balderrama ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Thermomechanical Analysis ◽  
Mechanical Analysis ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Accuracy And Precision ◽  
Wide Range ◽  
Transition Issues

Phase transition issues in the field of foods and drugs have significantly influenced these industries and consequently attracted the attention of scientists and engineers. The study of thermodynamic parameters such as the glass transition temperature (Tg), melting temperature (Tm), crystallization temperature (Tc), enthalpy (H), and heat capacity (Cp) may provide important information that can be used in the development of new products and improvement of those already in the market. The techniques most commonly employed for characterizing phase transitions are thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), and differential scanning calorimetry (DSC). Among these techniques, DSC is preferred because it allows the detection of transitions in a wide range of temperatures (−90 to 550 °C) and ease in the quantitative and qualitative analysis of the transitions. However, the standard DSC still presents some limitations that may reduce the accuracy and precision of measurements. The modulated differential scanning calorimetry (MDSC) has overcome some of these issues by employing sinusoidally modulated heating rates, which are used to determine the heat capacity. Another variant of the MDSC is the supercooling MDSC (SMDSC). SMDSC allows the detection of more complex thermal events such as solid–solid (Ts-s) transitions, liquid–liquid (Tl-l) transitions, and vitrification and devitrification temperatures (Tv and Tdv, respectively), which are typically found at the supercooling temperatures (Tco). The main advantage of MDSC relies on the accurate detection of complex transitions and the possibility of distinguishing reversible events (dependent on the heat capacity) from non-reversible events (dependent on kinetics).

The Effects of Power Level on the Microwave Heating of Selected Chemicals and Minerals

1988 ◽  
Vol 124 ◽  
Author(s):  
S. L. McGill ◽  
J. W. Walkiewicz ◽  
G. A. Smyres
Keyword(s):  
Microwave Heating ◽  
Power Level ◽  
Processing Parameters ◽  
Inert Atmosphere ◽  
Input Power ◽  
Heating Rates ◽  
Alumina Crucible ◽  
Quartz Beaker ◽  
Lossy Materials ◽  
Power Microwave

ABSTRACTThe effect of power level on the microwave heating characteristics of a variety of reagent-grade chemicals and minerals has been determined in a Bureau of Mines study. Heating rates of the powdered samples are presented for incident power ranging from 500 to 2,000 W at 2.45 GHz. The apparatus consisted of a WR 975 waveguide-applicator mounted to WR 284 waveguide sections and connected to a 3-kW power source. Tests were conducted in an alumina crucible enclosed in a fused-quartz beaker that was fitted with a Teflon lid to allow for a controlled inert atmosphere and thermocouple insertion. In general, heating rates increased as input power increased. Exceptions to this were some very high-lossy (microwave receptive) and very low-lossy materials that showed negligible changes with increased power. Microwave data collected should provide insight as to possible chemical and mineral processing applications as well as to assist in predictions of processing parameters.

Eine Methode zur Messung geringster Ölbedeckungen in Vakuumsystemen

1967 ◽  
Vol 22 (4) ◽  
pp. 549-553 ◽  
Author(s):  
R. Dobrozemsky ◽  
W. K. Huber ◽  
F. Viehböck
Keyword(s):  
High Vacuum ◽  
High Sensitivity ◽  
Radioactive Tracer ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
First Results ◽  
Tracer Isotope ◽  
Radioactive Tracer Method ◽  
Vacuum Systems

To get information on extremely small organic deposits in ultra high vacuum systems the sensitivity of most of the conventional methods for thickness measurements is not high enough. On the other hand the radioactive tracer method has shown its high sensitivity and wide versatility in many fields. Tritium with a half life of 12.3 γ and a mean β-energy of 5.4 keV was choosen as tracer isotope. A method is described for Tritium-labelling diffusion pump oils with specific activities up to 100 mC/g. Using the liquid scintillation counting technique one can detect deposits down to below 1010 molecules/cm2. First results with this Tritium labelled pump fluid are given under different operating conditions in an all metal ultra high vacuum system.

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