Changes In Sample Temperature Research Articles

A high resolution dilatometer using optical fiber interferometer.

We introduce a high-performance differential dilatometer based on an all-fiber Michelson interferometer at cryogenic temperature with 10-10 resolution in δL/L. It resolves the linear thermal expansion coefficient by measuring the oscillating changes of sample thickness and sample temperature with the interferometer and in situ thermometer, respectively. By measuring the linear thermal expansion coefficient α near the antiferromagnetic transition region of BaFe2As2 as a demonstration, we show that our dilatometer is able to measure thin samples with sub-pm-level length change resolution and mK-level temperature resolution. Despite the residual background thermal expansion of a few nm/K in the measurement results, our new dilatometer is still a powerful tool for the study of phase transition in condensed matter physics, especially has significant advantages in fragile materials with sub-100 μm thickness and being integrated with multiple synchronous measurements and tuning thanks to its extremely high resolution and contactless nature. The prototype design of this setup can be further improved in many aspects for specific applications.

Sudden adiabaticity signals reentrant bulk superconductivity in UTe2.

There has been a recent surge of interest in UTe due to its unconventional magnetic field (H)-reinforced spin-triplet superconducting phases persisting at fields far above the simple Pauli limit for . Magnetic fields in excess of 35 T then induce a field-polarized magnetic state via a first-order-like phase transition. More controversially, for field orientations close to and above 40 T, electrical resistivity measurements suggest that a further superconducting state may exist. However, no Meissner effect or thermodynamic evidence exists to date for this phase making it difficult to exclude alternative scenarios. In this paper, we describe a study using thermal, electrical, and magnetic probes in magnetic fields of up to 55 T applied between the [010] (b) and [001] (c) directions. Our MHz conductivity data reveal the field-induced state of low or vanishing electrical resistance; our simultaneous magnetocaloric effect measurements (i.e. changes in sample temperature due to changing magnetic field) show the first definitive evidence for adiabaticity and thermal behavior characteristic of bulk field-induced superconductivity.

Study on the Feasibility of the TG Method for Maximum Water Content Measurement of Waterlogged Archaeological Wood

ABSTRACT Thermogravimetry (TG) is used to measure the change of sample mass versus temperature or time under a program controlling temperature. It is a common thermal analysis tool with a precise built-in balance, and accurate data can be obtained through a small amount of sample at the level of milligrams. The feasibility of the TG method for determining maximum water content (MWC) measurement of waterlogged archaeological wood was studied. Simulated waterlogged wood and waterlogged archaeological wood were used to determine the test condition for the TG method. MWC data obtained through the oven-dry and TG methods with different mass gradients from 0–10 mg to >50 mg were analyzed statistically. Deviation, error bar, and coefficient of variation were evaluated. According to the results, when sample mass is no less than 30 mg, and holding time at 105°C is no less than 40 min, data deviation between these two methods is less than 5%. Effect of sampling depth and presence of inorganic deposits were also investigated. Specimens were taken from an archaeological wood with a sampling depth from 2 to 6 mm, then MWC was measured through the TG method. The results indicate MWC of the samples taken from a depth of 2–4 mm is higher than that taken from a depth of 0–2 mm and is lower than that taken from a depth of 4–6 mm, which is related to inorganic deposits. The presence of deposits was verified through SEM-EDX. MWC of three archaeological wood samples from China and five archaeological wood samples from Italy were measured to verify the effectiveness of the TG method when wood species and degradation degree are different.

Unusual microwave heating of water in reverse micellar solution

Microwaves (MWs) are widely used for heating food, accelerating chemical reactions, drying materials, therapies, and so on. Water molecules absorb MWs and produce heat because of their substantial electric dipole moments. Recently, increasing attention has been paid to accelerating various catalytic reactions in water-containing porous materials using MW irradiation. Here, a critical question is whether water in nanoscale pores generates heat in the same way as liquid water. Is it valid that MW-heating behaviors of nanoconfined water are estimated solely by a dielectric constant of liquid water? There are almost no studies regarding this question. Here, we address it using reverse micellar (RM) solutions. Reverse micelles are water-containing nanoscale cages formed by self-assembled surfactant molecules in oil. We measured real-time temperature changes of liquid samples within a waveguide under MW irradiation at 2.45 GHz and at MW intensities of ~ 3 to ~ 12 W/cm2. We found that the heat production and its rate per unit volume of water in the RM solution are about one order of magnitude larger than those of liquid water at all the MW intensities examined. This indicates that water spots that are much hotter than liquid water under MW irradiation at the same intensity, are formed in the RM solution. Our findings will give fundamental information to develop effective and energy-saving chemical reactions in nanoscale reactors with water under MW irradiation, and to study MW effects on various aqueous mediums with nanoconfined water. Furthermore, the RM solution will serve as a platform to study the impact of nanoconfined water on MW-assisted reactions.

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.

Analysis of influencing factors on displacement sampling performance of deep-sea gas-tight sampler

The collection and research of deep sea water has always been a hot and key topic in the field of marine research. Collecting seawater samples that can truly reflect the in-situ water composition information through a deep-sea sampler is an important technical means in the field of deep-sea exploration. The deep-sea water sampler designed in this subject samples deep-sea water by displacement sampling. According to the jet theory, the method of numerical calculation combined with experiment is adopted, the influence of indirect displacement, shape and diameter of sampling inlet, Coanda distance, sampling rate and other factors on the displacement effect is analyzed in this paper. The results of the study demonstrate that at low speed, multiple displacements can improve the displacement effect. In the high-speed sampling state, a single displacement method should be adopted. The design of making the sampling port as close as possible to the wall of the sampling cavity helps to strengthen the plane jet to improve the displacement efficiency. The displacement efficiency can be slightly improved by using the rectangular sampling inlet and outlet. As the extraction speed increases, the liquid mixing area becomes larger. Through discussion and comparison with similar research at home and abroad, the sampler has good performance and high sampling purity. The analysis of the effect of changes in sample temperature on the sampling displacement efficiency will be performed in the future. The research on the thermal insulation performance of the sampling channel will be put on the agenda.

Changes of sample temperature inside a cryo storage robot

Changes of sample temperature inside a cryo storage robot

Experimental and modeling study on centimeter pine char combustion in fast-heating Macro TGA

Biomass energy is an important renewable resource, and thermochemical conversion, including pyrolysis and combustion, is one of the main methods of biomass energy utilization. In industrial reactors, the biomass particles will experience a fast heating (∼1000 °C/min) process during pyrolysis. The particle size of biomass applied in industry has a wide range (from millimeter to centimeter scale). The study of the reaction characteristics of biomass pyrolysis and combustion is helpful for optimizing furnace design and working condition selection. In this research, the combustion of centimeter-scale pine char was studied with a newly built fast-heating Macro Thermal Gravimetric Analyzer (Macro TGA). This Macro TGA is able to conduct the pyrolysis and combustion of large biomass samples (up to 40 mm) with a fast heating rate (∼1000 °C/min), which is able to reflect the working conditions in industrial-scale reactors such as grate furnaces and dual fluidized beds. This Macro TGA can measure the online sample weight, temperature and sample size simultaneously during pyrolysis and combustion experiments. The combustion characteristics of different sizes of pine chars were investigated at various temperatures and oxygen concentrations. A zero-dimensional model was established to predict the sample weight loss, temperature change and sample shrinkage during the pine char combustion process. Three kinetic parameters α, A and E were applied in the model, and the values of the kinetic parameters were optimized by a genetic algorithm. The model prediction and experimental results are consistent with each other. Compared with previous studies, this study developed a new experimental method to measure the reaction characteristics (including sample weight, temperature and size) of centimeter-scale biomass under similar pyrolysis and combustion reaction conditions compared to industrial reactors, and a zero-dimensional model was established to describe the pine char combustion process.

Study of the aluminum ablation features and spectral intensity at a various sample temperature in vacuum environment

For the LIBS in-situ wall-analysis in the tokamak devices, the detection is under a vacuum environment and the sample temperature changes in real time. The influence of the sample temperature (Ts) on the LIBS spectral intensity and ablation features could be paid much attention to ensure the LIBS analysis accuracy. In this study, an aluminum sample was chosen as a proxy of beryllium, which has been selected as the first wall in ITER device. A comparison was performed between the obtained emission in vacuum and in air whilst the sample was heated. The emission intensification as a function of Ts in vacuum is quite different from that in air at atmospheric pressure. To study the Ts on the intensification process in vacuum, plasma properties (temperature T, electron number density ne and plasma size) and laser ablation features (the ablated crater depth and volume) were investigated. The experimental results indicate that an increase in Ts leads to a significant enhancement in the spectral intensity of Al. The electron density ne of plasma increases with Ts, but the plasma temperature T almost does not change with Ts. Plasma plume images also remained nearly unchanged with Ts in the detecting time window. However, it was found that the laser ablated crater features (diameter, depth and volume) depend significantly on Ts. Increasing Ts results in a larger and deeper ablation crater and a higher ridge around the crater for the same laser fluence. Net ablated mass also increases with increasing Ts. The results should be helpful to improve the accuracy of the LIBS analysis for the first wall composition in the tokamaks such as EAST and ITER.

Twisted light Michelson interferometer for high precision refractive index measurements.

Using orbital angular momentum beams in a Michelson interferometer opens the possibility for non-invasive measurements of refractive index changes down to 10-6 refractive index units. We demonstrate the application of a twisted light interferometer to directly measure the concentration of NaCl and glucose solutions label-free and in situ and to monitor temperature differences in the mK-µK range. From these measurements we can extract a correlation of the refractive index to concentration and to temperature from a liquid sample which is in good agreement with literature. Applying this type of twisted light interferometry yields a novel, robust, and easily implementable method for in situ monitoring of concentration and temperature changes in microfluidic samples.

Influence of thermoinduced magnetoelastic effect on domain structure of planar Ni microparticles

Results of studying the domain structure of planar Ni microparticles formed on single-crystal substrates from the lithium niobate and from the potassium titanyl phosphate at different temperatures are presented. The dependence of domain sizes on the sample temperature was studied. It is shown the observed change of the domain structure is caused by the magnetoelastic effect, which arises due to the difference in the thermal expansion coefficients of the substrate and microparticles as the sample temperature changes. It is shown, the sizes of magnetic domains, up to the creation of a state with a quasi-homogeneous magnetization may be set by the substrate temperature during the microparticles formation. Keywords: magnetoelastic effect, magnetic force microscopy, remagnetization, lithium niobate, potassium titanyl phosphate, temperature.

Влияние термоиндуцированного магнитоупругого эффекта на доменную структуру планарных Ni-микрочастиц

Results of studying the domain structure of planar Ni microparticles formed on single-crystal substrates from the lithium niobate and from the potassium titanyl phosphate at different temperatures are presented. The dependence of domain sizes on the sample temperature was studied. It is shown the observed change of the domain structure is caused by the magnetoelastic effect, which arises due to the difference in the thermal expansion coefficients of the substrate and microparticles as the sample temperature changes. It is shown, the sizes of magnetic domains, up to the creation of a state with a quasi-homogeneous magnetization may be set by the substrate temperature during the microparticles formation.

Computational study for natural convection effects on temperature during batch and continuous industrial scale radio frequency tempering/thawing processes

Radio frequency (RF) processing have been used for tempering and thawing. There have been significant experimental and mathematical model based studies for this process especially in the last two decades. The modeling studies applied the convective boundary condition with effective heat transfer coefficient and constant medium temperature in through field flat plate RF systems. The objective of this study was first to develop a mathematical model for conjugate heat transfer (natural convection) in a staggered through field electrode RF system and to use this model for natural convection effects in industrial scale processes. For this purpose, the developed comprehensive mathematical model was experimentally validated using the data from frozen tuna samples. The air temperature variation was also used for validation. Then, the developed model was used in industrial scale process simulations with the presence of natural convection. The industrially preferred flat plate systems were used in this part to determine the temperature and electric field evolutions. The results demonstrated the significant effect of the natural convection on sample surface temperature distribution and temperature change of air within the cavity. The evolved natural convection resulted in the variation of the heat transfer coefficient along the sample surfaces with significant changes in temperature. Based on these results, it might be concluded that the effect of air temperature change within the cavity during an RF processes should also be controlled and considered for industrial system design and process optimization.

Experimental Research on the Law of Energy Conversion during CO2 Sequestration in Coal

CO2 sequestration in coal is mainly attributed to adsorption. The adsorption experiments of CO2 were conducted at injection pressures ranging from 1 to 3 MPa on coal samples with five kinds of particle sizes. The fitting degree of four classical adsorption models to experimental adsorption data was systematically compared. The adsorption properties of CO2 were comprehensively discussed. The temperature changes of coal samples at different positions during CO2 adsorption were measured by using the improved adsorption tank, and then the energy conversion law was obtained. The results showed increasing gas injection pressure can effectively increase the adsorption capacity of CO2 on coal samples. The BET equation had the best fitting accuracy for CO2 adsorption on various size coal samples. There was a significant exothermic effect during CO2 adsorption and storage. With the rise of injection pressure, the peak value of the rising temperature of coal samples increased, but the change rate decreased. The maximum temperature rise of coal samples was up to 13.6 °C at 3 MPa, which should be of great concern for the prevention of coal spontaneous combustion. During the sequestration process of CO2, the adsorption resulted in a decrease in coal surface free energy and then partial conversion to heat, leading to the rise of coal temperature. In addition, the CO2 adsorption on the pore surface caused the expansion and deformation of coal.

Effects of Microwave Heating Paths on Pores and Cracks in Bituminous Coal.

To follow the effect of the microwave heating path on the structure of coal, eight 50 mm diameter, 30 mm long dry coal cores from the same coal seam with similar pore structure characteristics were microwave-treated using 4 pathways. The T2 spectrum, pore-volume, temperature, mass, and visual changes of coal samples were analyzed before and after microwave heating. The microwave heating path affected the macropores and microcracks and the crack development mode. When the same microwave energy was applied, microwave heating on the coal was mainly manifested by the opening of closed pores, before the pyrolysis temperature of the coal was reached. Increasing the energy density caused the water vapor to move from constant pressure expansion to constant volume expansion. This resulted in an exponential growth of the mesopore and macropore volumes. Meanwhile, the micropore volume increased due to the collapse of pore structures. As a result, high-power microwave heating could accelerate the vaporization rate of water. The rapid expansion of water vapor volume brought about a microwave heating effect similar to the “steam explosion”. The resulting local tensile stress enabled the cracks to develop, expand, and connect to others continuously. Thus, it formed a complex crack network leading to the outside of the coal sample.

Unusual magnetization process and magnetocaloric effect in α-CoV2O6 driven by pulsed magnetic fields

In low-dimensional Ising spin systems, an interesting observation is the presence of step magnetization at low temperatures. Here we combine both DC and pulsed magnetic fields to study the 1/3 magnetization plateau and multiple steps in the Ising spin-chain material α-CoV2O6. Magnetization in pulsed fields is quite different from that in DC fields, showing multiple steps in an intermediate range of 4.2–6 K, inverted hysteresis below 4.2 K and asymmetric magnetization in negative fields below 11 K. We demonstrate that these unusual behaviors in magnetization are caused by the spin dynamics and the anomalous magnetocaloric effect (MCE) in α-CoV2O6, i.e., abrupt changes of sample temperature in adiabatic conditions. We successfully separate the influence between the intrinsic slow spin dynamics and the quasi-extrinsic temperature change. From the MCE, we find that some irreversible behavior is originated from the slow spin dynamics. Two different slow dynamics associated with the metastable steps are observed: one is sensitive to the slow field sweep rate at the order of ∼mT s−1 and weakly depends on temperature, while the other responds to the rapid field sweep rate of ∼kT s−1 and dominates at lowest temperature. We also distinguish that the metastable transition at H 4 is the first order and crucial for the ferrimagnetic to ferromagnetic transition. This study is useful to the understanding of multistep magnetization in α-CoV2O6 and sheds light on recent experimental findings of related compounds.

Temperature-Dependent Solid-State NMR Proton Chemical-Shift Values and Hydrogen Bonding.

Temperature-dependent NMR experiments are often complicated by rather long magnetic-field equilibration times, for example, occurring upon a change of sample temperature. We demonstrate that the fast temporal stabilization of a magnetic field can be achieved by actively stabilizing the temperature of the magnet bore, which allows quantification of the weak temperature dependence of a proton chemical shift, which can be diagnostic for the presence of hydrogen bonds. Hydrogen bonding plays a central role in molecular recognition events from both fields, chemistry and biology. Their direct detection by standard structure-determination techniques, such as X-ray crystallography or cryo-electron microscopy, remains challenging due to the difficulties of approaching the required resolution, on the order of 1 Å. We, herein, explore a spectroscopic approach using solid-state NMR to identify protons engaged in hydrogen bonds and explore the measurement of proton chemical-shift temperature coefficients. Using the examples of a phosphorylated amino acid and the protein ubiquitin, we show that fast magic-angle spinning (MAS) experiments at 100 kHz yield sufficient resolution in proton-detected spectra to quantify the rather small chemical-shift changes upon temperature variations.

Temperature evaluation of colloidal nanoparticles by the thermal lens technique.

The use of highly sensitive thermometric methods is essential for the evaluation of nanoplatforms for photothermal therapy. In this study, the thermal lens technique was introduced to assess the optically induced temperature changes in colloidal samples of gold nanoparticles. Thermal lens measurements also allowed the acquisition of the nanoparticle absorption cross-section value, regardless of knowing the nanostructure scattering properties. The developed thermometric system exhibited 0.2 °C-1 sensitivity and was capable of measuring temperature variations of metallic colloidal samples with a resolution of 0.01 °C. Measuring colloidal temperature changes allows for the estimation of the localized temperature variation reached by each nanoheater, before thermalization of the excitation volume. Our results establish a practical and effective method to evaluate optically induced temperature changes on metallic colloids.

Capacitive detection of magnetostriction, dielectric constant, and magneto-caloric effects in pulsed magnetic fields.

We report on the development of a capacitance measuring system that allows measurements of capacitance in pulsed magnetic fields up to 61 T. By using this system, magnetic-field responses of various physical quantities, such as magnetostriction, magnetic-field-induced change in complex dielectric constant, and magneto-caloric effect, can be investigated in pulsed-magnetic-field conditions. Here, we examine the validity of our system for investigations of these magnetic-field-induced phenomena in pulse magnets. For the magnetostriction measurement, magnetostriction of a specimen can be measured through a change in the capacitance between two aligned electrodes glued on the specimen and a dilatometer. We demonstrate a precise detection of valley polarization in semimetallic bismuth through a magnetostriction signal with a resolution better than 10-6 of the relative length change. For the magnetic-field-induced change in complex dielectric constant, we successfully observed clear dielectric anomalies accompanied by magnetic/magnetoelectric phase transitions in multiferroic Pb(TiO)Cu4(PO4)4. For the measurement of magneto-caloric effect, a magnetic-field-induced change in sample temperature was verified for Gd3Ga5O12 with a capacitance thermometer made of a non-magnetic ferroelectric compound KTa1-xNbxO3 (x = 0.02) whose capacitance is nearly field-independent. These results show that our capacitance measuring system is a promising tool to study various magnetic-field-induced phenomena, which have been difficult to detect in pulsed magnetic fields.

Study of the thermal field of a mixture of soil and PCM materials with simulation of the warming effect during a phase change

Phase-change materials (PCM) possess an ability to accumulate and generate a lot of heat during the substance change from one phase to another. Such materials can be used with soil as an alternative type of thermal regulation of the subgrade during construction in cold regions. This paper reviews the impact of two types of PCM (PCMf-hybrid liquid and PCMm- microencapsulated paraffin) on the soil temperature. An experiment was conducted with three groups of samples: (1) samples with PCMm or PCMf added at a ratio of 2% and 4% of the dry weight of the soil; (2) samples reinforced with 4% of cement with an addition of PCMm or PCMf; and (3) samples with PCMf added after drying and re-adding water up to the optimal amount. PCMf and PCMm have been tested in DSC at various scanning speed levels. The results showed that, compared to that of the PCMm sample, PCMf has a greater enthalpy both during freezing and thawing, as well as the temperature peak during freezing is closer to zero. The study of temperature changes in soil samples with PCMm, PCMf, and cement added at the change of the ambient temperature T0=10°C→(-10°C)→(10°C) showed that the soil samples with various PCM additions have a lower temperature change rate than the soil samples without PCM additions. The results of the Scanning Electron Microscope (SEM) microfilming confirmed satisfactory components concentration in the soil mixture. There is also a noticeable number of craters and less porosity in the samples containing liquid PCMf and cement. A two-dimensional model of PCMm microcapsule per unit volume of soil was analyzed with the help of Comsol Multiphysics software (a powerful software product for modeling heat transfer and phase change in porous medium). It was determined that, during the phase change, the PCMm microcapsule has a thawing effect on the soil. During the examination of a three-dimensional model of eight PCMm capsules per unit volume of soil, it was noted that the thawing effect extends to 18.2% of the calculated area.