Actual Sample Temperature Research Articles

Quantitative regulation of electron–phonon coupling

Electron–phonon (e–p) coupling plays a crucial role in various physical phenomena, and regulation of e–p coupling is vital for the exploration and design of high-performance materials. However, the current research on this topic lacks accurate quantification, hindering further understanding of the underlying physical processes and its applications. In this work, we demonstrate quantitative regulation of e–p coupling, by pressure engineering and in-situ spectroscopy. We successfully observe both a distinct vibrational mode and a strong Stokes shift in layered CrBr3, which are clear signatures of e–p coupling. This allows us to achieve precise quantification of the Huang–Rhys factor S at the actual sample temperature, thus accurately determining the e–p coupling strength. We further reveal that pressure efficiently regulates the e–p coupling in CrBr3, evidenced by a remarkable 40% increase in S value. Our results offer an approach for quantifying and modulating e–p coupling, which can be leveraged for exploring and designing functional materials with targeted e–p coupling strengths.

One-pot synthesis of multicolor carbon quantum dots: One as pH sensor, one with ultra-narrow emission as fluorescent sensor for uric acid

In this work, tricolor carbon quantum dots (CQDs) including blue-, green-, and orange-CQDs were prepared in one-pot. Impressively, the full width at half maximum of blue-CQDs narrowed greatly to 8 nm, serving as the narrowest bandwidth emissive CQDs so far, to our knowledge, which even compared to colloidal semiconductor quantum dots. Based on the blue-CQDs exhibited highly selective and sensitive ‘on-off’ response towards Fe3+ and the outstanding antioxidant properties of uric acid, we constructed ‘on-off-on’ switching sensor to achieve quantitative measurement of uric acid. The green-CQDs served as simple pH sensor qualitatively judging acid rain based on ultrasensitive spectral redshift property at pH < 5.6. The sensors based on CQDs withstood actual sample matrix effects, pH and temperature change, and long-term storage. The ultra-narrow bandwidth emissive CQDs and fluorescent sensors based on distinctive optical properties of CQDs are meaningful and attractive research directions.

High-temperature optical and radiative properties of alumina–silica-based ceramic materials for solar thermal applications

Optical and radiative properties of alumina–silica-based ceramic materials are determined in the spectral range of 3–10 μm as a function of temperature in the range of 150−650°C. The investigated materials are commercial CARBO HSP samples and in-house fabricated samples with sintering temperatures of 1400°C and 1500°C. Spectral normal emittance of the samples is measured in the spectral range of 3–20 μm using Fourier transform infrared spectroscopy. A two-step inverse methodology consisting of analytical and numerical solutions to the radiative transfer equation is employed. The analytical solution is based on the modified two-flux approximation and the transport approximation, and is used to determine the transport scattering albedo. The iterative Monte Carlo ray-tracing method is used to obtain the transport extinction coefficient. The spectral normal emittance increases non-monotonically with the thermal treatment temperature of the samples due to the sintering extent increasing with the temperature during the preparation process. The spectral normal emittance of all investigated samples also increases non-monotonically with the increasing actual sample temperature. The maximum difference in total normal emittance at studied temperatures is 7.9%, 22% and 5.5% for the commercial sample and the in-house prepared samples sintered at 1400°C and 1500°C, respectively. With the sample temperature varying in the range of 150–650°C, the spectral normal emittance in the spectral range of 4–20 μm maximally varies by 23.2%, 44.3% and 23.4% for the commercial sample, and in-house prepared samples sintered at 1400°C and 1500°C, respectively. The transport scattering albedo decreases with increasing temperature for all samples in the considered spectral range. For all samples, the absorptive index increases non-monotonically with the increasing sample temperature. The most significant increase in the absorptive index, as the sample temperature increases, is found in the spectral range of 3–5 μm for the commercial material, and it increases by up to 31.6%, 116%, 170%, 186% and 194% when the temperature increases from 150°C to 250°C, 350°C, 450°C, 550°C and 650°C, respectively.

Influence of image analysis strategy, cooling rate, and sample volume on apparent protein cloud-point temperature determination

The protein cloud-point temperature (TCloud) is a known representative of protein–protein interaction strength and provides valuable information during the development and characterization of protein-based products, such as biopharmaceutics. A high-throughput low volume TCloud detection method was introduced in preceding work, where it was concluded that the extracted value is an apparent TCloud (TCloud,app). As an understanding of the apparent nature is imperative to facilitate inter-study data comparability, the current work was performed to systematically evaluate the influence of 3 image analysis strategies and 2 experimental parameters (sample volume and cooling rate) on TCloud,app detection of lysozyme. Different image analysis strategies showed that TCloud,app is detectable by means of total pixel intensity difference and the total number of white pixels, but the latter is also able to extract the ice nucleation temperature. Experimental parameter variation showed a TCloud,app depression for increasing cooling rates (0.1–0.5 °C/min), and larger sample volumes (5–24 μL). Exploratory thermographic data indicated this resulted from a temperature discrepancy between the measured temperature by the cryogenic device and the actual sample temperature. Literature validation confirmed that the discrepancy does not affect the relative inter-study comparability of the samples, regardless of the image analysis strategy or experimental parameters. Additionally, high measurement precision was demonstrated, as TCloud,app changes were detectable down to a sample volume of only 5 μL and for 0.1 °C/min cooling rate increments. This work explains the apparent nature of the TCloud detection method, showcases its detection precision, and broadens the applicability of the experimental setup.

Development of a novel thermoelectric module based device for thermal stability measurement of phase change materials

Abstract A recently developed method for the thermal stability measurement of phase-change materials (PCMs) involves thermal cycling using a thermoelectric module as a heating and cooling element. However, the utility of this approach was found to have some limitations, mainly because the thermoelectric polarity is changed according to time rather than the actual sample temperature. A method for thermal cycling test, where the thermoelectric polarity is automatically changed according to the sample temperature was developed in this study. In addition, a new cartridge design in this device requires a small sample volume (1.53 cm3) and can be easily assembled and disassembled. This proposed device was tested on beeswax as a PCM sample. This is very important for savings PCMs material which usually expensive. The results showed that the apparatus had automatically cycled between the melting and cooling temperatures of beeswax. The thermal data showed that beeswax retains consistent melting and freezing temperatures after 1000 cycles, however, its heat of fusion degrades over repeated thermal cycling. This apparatus can be readily applied to study a wide range of PCMs for such as thermal energy storage materials for energy conservation. To our best knowledge, yet no study has been performed on this kind of equipment so far.

Numerical Modeling of Peroxidase Inactivation in Potato Tubers

Abstract. The properties of peroxidase (POD) inactivation in potato during hot water heating were studied. In the conventional method, the vegetable sample is heated at a constant temperature, and the POD inactivation rate at each temperature is obtained. The activation energy and frequency factor are then calculated from Arrhenius plots of the inactivation rates. Although only the temperature of the hot water is used in the calculation, the actual potato sample temperature is not considered. In this study, unequal temperature distributions in a potato cylinder during hot water heating were simulated by a finite element method using COMSOL Multiphysics. In this simulation, thermal conductivity of the potato tuber was determined to fit best with the measured temperature as λ = (-3.1 x 10-5)T2 + (1.8 x 10-2)T - 1.9. Additionally, POD inactivation was predicted based on the simulated temperature distribution. The activation energy and frequency factor were then determined as 29.2 kJ mol-1 and 2.0 x 102 s-1 to minimize the root mean square error between predicted and measured POD activities. The adequacy of these parameters was confirmed using a validation test with a potato cylinder of a different size. It was concluded that finite element method simulation was valid for determining the POD inactivation property.

Radiation heat transfer enhanced absorber for high temperature solar-thermal applications

A novel design of a solar absorber making use of different optical properties of materials for high temperature solar-thermal applications is proposed. For the two sides of the sample, the solar absorbing surface is designed to absorb sunlight and reduce radiative heat loss, while the high emission surface is aimed at enhancing the heat transfer. The composite samples were prepared by tape casting, alternately laminating and high temperature sintering. Room temperature optical properties and temperature-dependent radiative properties of the composite samples were studied. The results showed that the emittances of the absorbing surface and heat transfer surface were 0.32 and 0.70, respectively. Due to this difference of emittances, the two surfaces exhibited a radiation temperature (read from thermography camera) difference of 140°C when the actual sample temperature is 600°C.

Isoconversional analysis of copper recrystallization

Recrystallization of Cu deformed under compression has been monitored by differential scanning calorimetry (DSC) with experiments carried out at constant heating rate. From these experiments, an isothermal crystallization process has been predicted by the classical Kolmogorov–Johnson–Mehl–Avrami (KJMA) kinetics and by model-free isoconversional analysis. Whereas prediction by KJMA does not match the experimental curve, the isoconversional prediction is successful. The paper also highlights the need to correct the raw DSC curves to obtain the actual sample temperature and to avoid curve distortion due to thermal inertia.

Direct measurements of the magnetic entropy change.

An experimental device that can accurately measure the magnetic entropy change, Δs, as a function of temperature, T, and magnetic field, H, is presented. The magnetic field source is in this case a set of counter-rotating concentric Halbach-type magnets, which produce a highly homogeneous applied field with constant orientation. The field may be varied from 0 to 1.5 T in a continuous way. The temperature stability of the system is controlled to within ±10 mK and the standard range for the current setup is from 230 K to 330 K. The device is under high vacuum and we show that thermal losses to the ambient are negligible in terms of the calorimetric determination of the magnetic entropy change, while the losses cannot be ignored when correcting for the actual sample temperature. We apply the device to two different types of samples; one is commercial grade Gd, i.e., a pure second-order phase transition material, while the other is Gd5Si2Ge2, a first order magnetic phase transition material. We demonstrate the device's ability to fully capture the thermal hysteresis of the latter sample by following appropriate thermal resetting scheme and magnetic resetting scheme.

A Calorimetric Study of Ti-6Al-4V Alloy

Ti-6Al-4V titanium alloy is widely used in industrial applications such as aeronautic and aerospace due to its good mechanical properties at high temperatures. The aim of the work is to determine the heat capacity of the thermal cycled titanium alloy. The cylindrical specimens of dimension 3 ± 0.1 mm in diameter and 2.5 ± 0.1 mm in length were machined from the CNC machine. The specimens were subject to two different types of heat treatments (Solution treated and annealed). First type of heat treatment (annealing) is processed by heating the specimen to a temperature of 7500 C for 4 hours and it is cooled in the furnace to reach the atmospheric temperature. Second type of heat treatment (solution treating) is processed by the specimen is heated to a temperature of 9750 C for 1 hour and it is quenched in a solution containing water with 5% of caustic soda. After quenching (delay of 6 second), aging was done at 4500 C for 4 hours and then it is furnace cooled to reach atmospheric temperature The heat treated specimens were thermal cycled in a specially designed thermal cycling apparatus for different cycles Heat flow and the flow of energy into or out of the sample as a function of temperature was measured by using Differential Scanning Calorimetry (DSC). The heat flow response is recorded as a function of actual sample temperature range from -120˚ C to 380˚ C. The measurements of the heat capacity by DSC with an accuracy of ±2% have been reported. This study restrict the use of DSC as a truly quantitative calorimetric technique and concentrates mainly on the practical set of experimental heat capacity data measured over a temperature range for different aerospace materials being used/developed indigenously for the Indian Space Programme. Keywords: Thermal Analysis, Differential Scanning Calorimeter, Specific Heat, Heat Treatment

A Calorimetric Study of Ti-6AL-4V Alloy

Ti-6Al-4V titanium alloy is widely used in industrial applications such as aeronautic and aerospace due to its good mechanical properties at high temperatures. The aim of the work is to determine the heat capacity of the thermal cycled titanium alloy. The cylindrical specimens of dimension 3 ± 0.1 mm in diameter and 2.5 ± 0.1 mm in length were machined from the CNC machine. The specimens were subject to two different types of heat treatments (Solution treated and annealed). First type of heat treatment (annealing) is processed by heating the specimen to a temperature of 7500°C for 4 hours and it is cooled in the furnace to reach the atmospheric temperature. Second type of heat treatment (solution treating) is processed by the specimen is heated to a temperature of 975°C for 1 hour and it is quenched in a solution containing water with 5% of caustic soda. After quenching (delay of 6 second), aging was done at 450° C for 4 hours and then it is furnace cooled to reach atmospheric temperature The heat treated specimens were thermal cycled in a specially designed thermal cycling apparatus for different cycles heat flow and the flow of energy into or out of the sample as a function of temperature was measured by using Differential Scanning Calorimetry (DSC). The heat flow response is recorded as a function of actual sample temperature range from -120° C to 380° C. The measurements of the heat capacity by DSC with an accuracy of ±2% have been reported. This study restrict the use of DSC as a truly quantitative calorimetric technique and concentrates mainly on the practical set of experimental heat capacity data measured over a temperature range for different aerospace materials being used/developed indigenously for the Indian Space Programme.

Electroresistance and Joule heating effects in manganite thin films

Electroresistance phenomena have been investigated in La2/3Sr1/3MnO3 (LSMO) microbridges through the analysis of I-V characteristic curves. I-V curves are nonlinear in all the range of temperatures explored, but are almost reversible and exhibit origin symmetry which suggest the existence of Joule self-heating effects. However, comparing the resistance determined from the I-V curves (R = V/I) at the actual sample temperature, measured through a Pt thermometer microfabricated on top of the LSMO microbridges, with the resistance measured in thermal equilibrium, i.e., in the low current regime, it is evident that Joule self-heating effects alone cannot account for the experimental results. We demonstrate that oxygen depletion is the cause for the observed increase of resistance and the reduction of TC.

Specific Heat Capacity Measurement of Al / SiC&lt;sub&gt;p&lt;/sub&gt; Composites by Differential Scanning Calorimeter

Various materials are used to achieve a good “Thermal Control System” (TCS) of spacecraft. The performance of the TCS totally depends upon the thermal behaviour of the materials used in the elements of TCS. The measurements of the thermal properties of materials are fundamental for better understanding of the thermal design. Differential Scanning Calorimetry (DSC) is the most widely used thermal technique for obtaining a wealth of information about a material, especially for the specific heat measurement of a material. Stir casting technique was used to fabricate the 7075 aluminum alloy and 7075 Al / SiCp composites. The heat flow response is recorded as a function of actual sample temperature range from -1000 C to 4000 C. Specific heat characteristics of 7075 Al reinforced with different volume fraction of silicon carbide composites fabricated by stir casting method was analyzed.

Instrumentation of a PLC-Regulated Temperature Cycler with a PID Control Unit and Its Use for Miniaturized PCR Systems with Reduced Volumes of Aqueous Sample Droplets Isolated in Oil Phase in a Microwell

We have developed a temperature cycler for polymerase chain reaction (PCR) in a microwell fabricated on a polymer/glass chip. The entire system consisted of three subsystems, which included (1) a thermal conditioner, (2) a proportional-integral-derivative (PID) control signal conditioner and (3) a data acquisition subsystem. The subsystems were regulated coordinately by a ladder logic program written for the programmable logic control (PLC) so that an actual sample temperature could be timed, changed and maintained according to the programmed temperature cycles. The present temperature control system showed high accuracy, stability and minimum overshoot with reduced heating and cooling transition rates. Applicability of the temperature controller to the miniaturized PCR system with reduced volumes of aqueous sample droplets isolated in an oil phase was confirmed by successful amplifications of a target DNA sequence in the microwell.

Robust charge and magnetic orders under electric field and current in multiferroicLuFe2O4

We performed elastic neutron scattering measurements on the charge- and magnetically-ordered multiferroic material LuFe(2)O(4). An external electric field along the [001] direction with strength up to 20 kV/cm applied at low temperature (~100 K) does not affect either the charge or magnetic structure. At higher temperatures (~360 K), before the transition to three-dimensional charge-ordered state, the resistivity of the sample is low, and an electric current was applied instead. A reduction of the charge and magnetic peak intensities occurs when the sample is cooled under a constant electric current. However, after calibrating the real sample temperature using its own resistance-temperature curve, we show that the actual sample temperature is higher than the thermometer readings, and the "intensity reduction" is entirely due to internal sample heating by the applied current. Our results suggest that the charge and magnetic orders in LuFe(2)O(4) are unaffected by the application of external electric field/current, and previously observed electric field/current effects can be naturally explained by internal sample heating.

A calorimetric study of 7075 Al/SiC p composites

Various materials are used to achieve a good “thermal control system” (TCS) of spacecraft. The performance of the TCS totally depends upon the thermal behaviour of the materials used in its elements. The measurements of the thermal properties of materials are fundamental for better understanding of the thermal design. Differential scanning calorimetry (DSC) is the most widely used thermal technique for obtaining a wealth of information about a material. Heat flow and the flow of energy into or out of the sample as a function of temperature can be measured by using DSC. The actual value of heat flow measured depends upon the effect of the reference and is not absolute. The sapphire is used as reference in this study. The specific heat (heat capacity, C p ) of a material can be determined quantitatively using DSC. The measurement was made by heating a very small quantity (milligrams) of the 7075 aluminium alloy and 7075 Al/SiC p composites. Stir casting technique was used to fabricate the 7075 aluminium alloy and 7075 Al/SiC p composites. Three different types of composites (MMC10, MMC15 and MMC20) were prepared by varying volume fractions of SiC p (10%, 15% and 20% volume fractions). The heat flow response is recorded as a function of actual sample temperature range from −100 °C to 375 °C. The measurements of the heat capacity by DSC with an accuracy of ±2% has been reported for each sample of three runs. This study restrict the use of DSC as a truly quantitative calorimetric technique and concentrates mainly on the practical set of experimental heat capacity data measured over a temperature range for different aerospace materials being used/developed indigenously for the Indian Space Program.

The T-lock: automated compensation of radio-frequency induced sample heating

Modern high-field NMR spectrometers can stabilize the nominal sample temperature at a precision of less than 0.1 K. However, the actual sample temperature may differ from the nominal value by several degrees because the sample heating caused by high-power radio frequency pulses is not readily detected by the temperature sensors. Without correction, transfer of chemical shifts between different experiments causes problems in the data analysis. In principle, the temperature differences can be corrected by manual procedures but this is cumbersome and not fully reliable. Here, we introduce the concept of a "T-lock", which automatically maintains the sample at the same reference temperature over the course of different NMR experiments. The T-lock works by continuously measuring the resonance frequency of a suitable spin and simultaneously adjusting the temperature control, thus locking the sample temperature at the reference value. For three different nuclei, 13C, 17O and 31P in the compounds alanine, water, and phosphate, respectively, the T-lock accuracy was found to be <0.1 K. The use of dummy scan periods with variable lengths allows a reliable establishment of the thermal equilibrium before the acquisition of an experiment starts.

Analysis of volumetric changes through melting using a dilatometer

A conventional push-rod dilatometer is modified in order to accurately correlate the measured density to the predicted sample temperature of alloys in the phase-change regime. This new configuration makes use of a standard furnace assembly; however, the specimen is now symmetrically encased in a well-instrumented, graphite cylindrical shell. The combination of system geometry and high-conductivity sample holder material promotes the development of a simplified heat transfer model. The solution of this model properly correlates the measured density to that of the actual sample temperature based on using remote, sample-holder temperature measurements. Preliminary results using aluminum A356 provide insight into the proposed configuration.

Fast transient infrared studies in material science: development of a novel low dead-volume, high temperature DRIFTS cell

A prototype DRIFTS flow reaction chamber was designed and developed in order to find analytical application in the study of heterogeneous catalysts operating at high temperatures under fast transient gas feed conditions. Minimisation of dead-volumes allows gas replacement in 8–10 s at 10 mL min −1 total flow. To overcome problems related to the reactivity of the cell walls under alternating oxidizing/reducing gases, the cell was built with Inconel 600™, which was tested to be very inert even at high temperatures. The sample holder, which was developed to closely resemble a micro plug-flow reactor, poses some problems in terms of heat transfer to the outer body of the cell (limiting then the maximum reachable temperature) and of the correct measurement of the actual sample temperature. These problems were solved with a careful re-design of the upper part of the cell. The second prototype thus derived is able to reach temperatures up to 803 K and allows gas replacement in less than 4 s at 10 mL min −1. The cell is inserted in a MCT-FT-IR, which allows to collect high quality spectra with a 1 s time-resolution. The downstream flow can be analysed by a quadrupole mass spectrometer equipped with an enclosed source and by a commercial GC. The performances of this prototype cell are presented showing some tests carried out with ceria–zirconia (Ce x Zr 1− x O 2) catalysts for CO abatement under real operando conditions.

The enthalpy of sublimation of 5,10,15,20-tetraphenylporphine and 5,10,15,20-tetrakis(4-methoxyphenyl)porphine

The enthalpies of sublimation of 5,10,15,20-tetraphenylporphine (CA registry number 917-23-7, TPP) and 5,10,15,20-tetrakis(4-methoxyphenyl)porphine (CA registry number 22112-78-3, TMPP), were determined by the Knudsen effusion method using a quartz-crystal microbalance in a system designed specially to work at high temperatures. The system includes stainless steel-Pyrex glass joints over one of which the effusion cell holder is welded in such a way that the heating and temperature sensor for measurement and control are accessible without venting the system. The design permits precise measurements of the actual sample temperature under low-pressure conditions. From the experimental results the derived values for this property are:ΔcrgHmo (TPP, 550 K) = ( 171 ± 2) kJ · mol −1andΔcrgHmo (TMPP, 563 K) = (213 ± 10) kJ · mol −1. Combining these values with the previously reported standard molar enthalpies of formation in the condensed phase, the corresponding standard molar enthalpies of formation in the gas state at T= 298.15 K were calculated as ΔfHmo(g) = (839 ± 9) kJ · mol −1for TPP andΔfHmo (g) = (295 ± 14) kJ · mol −1for TMPP. An estimate of these enthalpies by the second-order Benson’s group additivity approach was computed based upon the assumption of total or null aromaticity in the porphyrin macrocycle. Using the enthalpies of formation of the gaseous atoms in their ground states, the enthalpies of atomisation were derived as:ΔatHmo (g) = (39125 ± 22) kJ · mol −1for TPP andΔatHmo (g) = (45277 ± 25) kJ · mol −1for TMPP. Recommended Laidler parameters were used to predict these values, considering a correction for four pyrrole ring strain contribution.