Measured Temperature Range Research Articles

Adsorption kinetics and thermodynamics of rare earth on Montmorillonite modified by sulfuric acid

Montmorillonite (Mt), the major clay mineral in the tailings of weathered crust elution-deposited rare earth ores, was modified to improve its adsorption capacity of rare earth ions (RE3+). The effect of initial RE3+ concentration, temperature and solution pH on the adsorption capacity of Mt to La3+ and Y3+ were investigated in this study, and further the adsorption kinetics and adsorption thermodynamics were discussed to analyze the adsorbing behavior of modified Mt to RE3+. The adsorption capacity of RE3+ on modified Mt is related to the initial RE3+concentration and temperature. The pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich models were applied to evaluate the adsorption kinetics. The results show that the adsorption process of RE3+ on modified Mt is more accurately represented by the pseudo-second-order model, and it is controlled by chemisorption rather than diffusion. The Arrhenius activation energy values of Y3+ and La3+ are 14.259 kJ/mol and 22.845 kJ/mol, respectively. The thermodynamics studies indicate that the adsorption process is a spontaneous endothermic process in the measured temperature range.

A highly sensitive optical fiber temperature sensor based on the enhanced Vernier effect

A highly sensitive optical fiber temperature sensor based on enhanced Vernier effect is proposed in this paper. The sensor is a cascaded structure which is composed of fiber optic Sagnac interferometer (FSI) and intermodal Mach–Zehnder interferometer (IMZI). Because the interference fringes of the IMZI and the FSI shift to opposite directions as ambient temperature varies, the enhanced Vernier effect is obtained. Compared to the temperature sensor based on the traditional Vernier effect, the proposed sensor realizes the high sensitivity temperature measurement and doesn’t need any special sensitizing materials, complicated manufacture process or a reference interferometer which need to be desensitized. Experimental results show that the sensitivity of the sensor is 20.86 nm/°C. A good linear responses can be obtained in temperature measurement range from 25 °C to 33 °C.

High sensitivity fiber-optic temperature sensor based on PDMS glue-filled capillary

A high sensitivity fiber-optic sensor based on temperature-sensitive material is proposed and demonstrated experimentally. The sensor consists of single-mode fiber (SMF), silicon capillary tube (SCT) and polydimethylsiloxane (PDMS) film, where the PDMS glue is filled into the SCT and s a temperature-sensitive medium sensing cavity is formed at the end of the SMF. Due to its high thermal expansion and thermo-optic effects, the sensor structure is more sensitive response to the change of ambient temperature. The experiment results demonstrate that the maximum temperature sensitivity of our proposed sensor is 3.449 nm/°C in temperature range of 34–48 °C, and the linearity of fitting curve is 99.9%. Compared with the same structure but filled with ultraviolet (UV) glue, the PDMS-based sensor not only has much higher temperature sensitivity, but also has better stability and repeatability. For the new type of sensor composed of optical fiber microstructure and sensitive material, the proposed sensor structure can increase the measurement temperature range. The sensor structure is simple to fabricate, stable in structure, and possessing good repeatability, which has great potential applications in the temperature sensing fields.

Co-deformation between the metallic matrix and intermetallic phases in a creep-resistant Mg-3.68Al-3.8Ca alloy

The microstructure of Mg-Al-Ca alloys consists of a hard intra- and intergranular eutectic Laves phase network embedded in a soft α-Mg matrix. For such heterogeneous microstructures, the mechanical response and co-deformation of both phases under external load are not yet fully understood. We therefore used nano- and microindentation in combination with electron microscopy to study the deformation behaviour of an Mg-3.68Al-3.8Ca alloy.We found that the hardness of the Mg2Ca phase was significantly larger than the α-Mg phase and stays constant within the measured temperature range. The strain rate sensitivity of the softer α-Mg phase and of the interfaces increased while activation volume decreased with temperature. The creep deformation of the Mg2Ca Laves phase was significantly lower than the α-Mg phase at 170 °C. Moreover, the deformation zone around and below microindents was dependant on the matrix orientation and was influenced by the presence of Laves phases. Most importantly, slip transfer from the α-Mg phase to the (Mg,Al)2Ca Laves phase occurred, carried by the basal planes. Based on the observed orientation relationship and active slip systems, a slip transfer mechanism from the soft α-Mg phase to the hard Laves phase is proposed. Further, we present implications for future alloy design strategies.

Determination of the leakage current transport mechanisms in quasi-vertical GaN–on–Si Schottky barrier diodes (SBDs) at low and high reverse biases and varied temperatures

Temperature-dependent current–voltage characteristics was measured to investigate leakage conduction mechanisms in GaN-on-Si quasi-vertical Schottky barrier diode. At low reverse bias, thermionic emission is dominated. At voltage range from −1 to −20 V, variable range hopping (VRH) is main leakage current mechanism at low temperatures (298–373 K), while at high temperatures (498–573 K), electrons gain enough energy and emit into the trapped states, Frenkel–Poole emission becomes dominant. At a relatively high voltage range, the increased electric field promotes the electron hopping along the threading dislocation in the bulk GaN layers, and VRH becomes the main current mechanism at whole measured temperature range (298–573 K).

Optical temperature sensing characteristics of Sm3+ doped YAG single crystal fiber based on luminescence emission

A series of YAG: x mol%Sm3+ single crystal (SC) materials, in which x is 0.3, 0.5, 1, 2, respectively, have been synthesized through laser heated pedestal growth (LHPG) method. The down-conversion luminescence properties of prepared fluorescent materials were investigated under a 405 nm laser. According to the results, 0.5 mol% was selected as the optimal doping concentration, and the integrated YAG single crystal fiber (SCF) with end Sm3+ doped was further fabricated. Then the optical temperature sensing characteristics were studied by the technique of the fluorescence intensity ratio (FIR) in detail. It shows that 4F3/2 and 4G5/2 of Sm3+ ions are thermally coupled energy levels. The FIR of the 4F3/2/4G5/2 → 6H5/2 increases monotonously as temperature rises, and its temperature measurement range can be extended to 1178 K. The maximum absolute sensitivity and maximum relative sensitivity are 3.046 × 10−4 K−1(1129 K) and 5.033 × 10−3 K−1 (500 K), respectively. Additionally, the FIRs of various emission bands from 4G5/2 → 6H5/2, 7/2 and the FIR of the emission sub-bands from 4G5/2 → 6H9/2 exhibit temperature dependence in 303–1028 K and 303–878 K, respectively. These results indicate that YAG: Sm3+ SC is a very promising high-temperature sensing material.

Up‐conversion and temperature sensing properties of Na2GdMg2(VO4)3:Yb3+,Er3+ phosphors

AbstractIn this paper, Na2GdMg2(VO4)3:Yb3+,Er3+ phosphors were synthesized through high‐temperature solid‐state method. According to X‐ray powder diffractogram, diffuse reflection spectra, scanning electron microscopy, up‐conversion (UC) emission spectra, power‐dependent UC spectra, fluorescent lifetime curves, and temperature‐dependent emission spectra, the crystal structures, UC luminescent characteristics, and the performances of temperature sensing by using fluorescence intensity ratio technique were studied in detail. Heavy‐doped phosphors with 59% (Yb3+ and Er3+) doping content are achieved. In addition, excited by 980nm laser, three characteristic luminescence peaks of Er3+ at 525 nm (2H11/2 → 4I15/2), 550 nm (4S3/2 → 4I15/2) and 660 nm (4F9/2 → 4I15/2) emerge in the UC spectra of Er3+ single‐doped and Yb3+,Er3+ co‐doped phosphors. UC spectra are dominated by green emission and greatly enhanced UC emission over 389 times is realized by introducing Yb3+. In addition, the ratiometric techniques of thermally coupled energy levels of Er3+ (525/550 nm, 2H11/2/4S3/2 → 4I15/2) are used to achieve a wide range of temperature measurement. When the temperature is 303 K, relative sensitivity is as high as 0.976%K–1. The minimal temperature resolution is 0.3 K@303 K. All experimental results show Yb3+,Er3+ co‐doped Na2GdMg2(VO4)3 phosphors might act as optical temperature sensing materials.

Regulation of exciton for high thermoelectric performance in (Bi, Sb)2Te3 alloys via doping with Pb and multi-scale microstructure

Herein, we report a reproducible improvement of the thermoelectric performance in BiSbTe alloy via kinetically and dynamically regulating excitation behavior in the intrinsic excitation regime. Doping with Pb increases the carrier concentration to the optimal value, kinetically pushing the onset temperature for the intrinsic excitation from 350 K for Bi0.46Sb1.54Te3 sample to 450 K for Pb0.01(Bi0.46Sb1.54)0.995Te3 sample. Moreover, the refined grains, nanostructures as well as dense dislocations induced by the melt-spinning process not only lower the lattice thermal conductivity via intensifying the interfacial phonon scattering but also selectively block the migration of minority carrier, modifying the dynamic process of the charge carrier and resulting in a smaller ratio of (μe/μh). This improves the power factor in the measured temperature range and suppresses the bipolar thermal conductivity in the intrinsic excitation regime. Thus, a maximum power factor of 4.44 mW m−1 K−2 and the lowest thermal conductivity of 1.06 W m−1 K−1 are attained for the sample with refined grains and nanostructures. All these contribute to the highest ZT value of 1.31 at 380 K and the highest average ZT value of 1.17 from 300 K to 500 K for Pb0.002(Bi0.46Sb1.54)0.999Te3 sample. This improved thermoelectric property was further verified in a thermoelectric module with the conversion efficiency of 4.38 % under a temperature gradient of 175 K, which is 20 % higher than that of the commercial ZM-based module under the same temperature gradient.

Recommended Values of the Viscosity in the Limit of Zero Density for R134a and Six Vapors of Aromatic Hydrocarbons as Well as of the Initial Density Dependence of Viscosity for R134a. Revisited from Experiment Between 297\xa0K and 631\xa0K

Previously published experimental viscosity data at low density, originally obtained using all-quartz oscillating-disk viscometers for R134a and six vapors of aromatic hydrocarbons in the temperature range between 297 K and 631 K at most, were re-evaluated after an improved re-calibration. The relative combined expanded (k=2) uncertainty of the re-evaluated data are 0.2 % near room temperature and increases to 0.3 % at higher temperatures. The re-evaluated data for R134a as well as for the vapors of mesitylene, durene, diphenyl, fluorobenzene, chlorobenzene, and p-dichlorobenzene were arranged in approximately isothermal groups and converted into quasi-isothermal viscosity data using a first-order Taylor series in temperature. Then, the data for R134a were evaluated by means of a series expansion truncated at first order to obtain the zero density and initial density viscosity coefficients, eta ^{(0)} and eta ^{(1)}. For the six aromatic vapors, the Rainwater–Friend theory for the initial density dependence of the viscosity was used to derive eta ^{(0)} values. Finally, reliable eta ^{(0)} and also eta ^{(1)} values for R134a were selected as reference values in the measured temperature range to be applied when generating a new viscosity formulation.

High-Performance Temperature Sensor by Employing Screen Printing Technology.

In the present study, a high-performance n-type temperature sensor was developed by a new and facile synthesis approach, which could apply to ambient temperature applications. As impacted by the low sintering temperature of flexible polyimide substrates, a screen printing technology-based method to prepare thermoelectric materials and a low-temperature heat treatment process applying to polymer substrates were proposed and achieved. By regulating the preparation parameters of the high-performance n-type indium oxide material, the optimal proportioning method and the post-treatment process method were developed. The sensors based on thermoelectric effects exhibited a sensitivity of 162.5 μV/°C, as well as a wide range of temperature measurement from ambient temperature to 223.6 °C. Furthermore, it is expected to conduct temperature monitoring in different scenarios through a sensor prepared in masks and mechanical hands, laying a foundation for the large-scale manufacturing and widespread application of flexible electronic skin and devices.

Highly-sensitive and wide-range temperature sensor based on polymer-filled micro-cavity in fibre Bragg grating by temperature segmentation

A highly-sensitive and wide-range temperature sensor based on a polymer-filled Mach-Zehnder (MZ) micro-cavity in commercial fibre Bragg grating (FBG) was proposed. The micro-cavity was fabricated rightly across half of the fibre core at the FBG position by using femtosecond laser micromachining, and then it was filled with the polymer with high thermo-optical coefficient. A temperature segmentation demodulation method was presented by monitoring the MZ peak and FBG peak in the transmission spectrum synchronously, which expanded the temperature measurement range to more than 80 °C with ultra-high sensitivity (9.33 nm/°C) and perfect linearity.

Implementation of a Temperature Measurement System for Transferring Image Patterns to Copper Boards in PCB Making

This research has succeeded in implementing a PLC-Based Temperature Control System for Transferring Image Patterns to Copper Boards in PCB (Printed Circuit Board) Manufacturing. This tool is made to simplify and speed up the process of transferring image patterns to copper boards in PCB manufacture. This Regulatory System consists of HMI, PLC, Thermocouple, Transmitter Thermocouple, Heater, as well as iron coating mechanics. HMI serves to display the settings received by the PLC as well as a second controller. While the PLC functions as a data processing center needed by the system and the main controller, the thermocouple functions to issue an output in the form of voltage. Heater as a heater and Mechanics of iron layer as pressure on the copper board. The results of the research on this system are image patterns that can be transferred to the copper board automatically with a measured temperature range of 400C - 1000C.

Influence of Surface Adsorption on the Electrical Transport Properties of Ultrathin Indium Tin Oxide Films

We systematically investigated the temperature-dependent behaviors of the resistivities ρ and carrier concentrations n of a series of ultrathin indium tin oxide (ITO) films with thickness t ranging from ∼5.3 to ∼35.0 nm grown on yttrium-stabilized ZrO2 substrates. For the t ≳ 17.5 nm films, the resistivity versus temperature can be described by the Bloch–Grüneisen formula, and the carrier concentration almost retains constant over the whole measured temperature range. For the t ≃ 5.3 nm (7.0 nm) film, the carrier concentration increases with increasing temperature above ∼300 K, and the resistivity initially increases with increasing temperature and then decreases with further increasing temperature above ∼330 K (∼355 K). By comparison of the transport properties of ITO films depositing on different substrates and exposing the films on different atmospheres, it is found that the enhancement of carrier concentration and reduction of resistivity at high temperature regime originate from the dissociative adsorption of water vapor on the surface of the ITO films.

Ti Addition Effect on the Grain Structure Evolution and Thermoelectric Transport Properties of Hf0.5Zr0.5NiSn0.98Sb0.02 Half-Heusler Alloy.

Compositional tuning is one of the important approaches to enhance the electronic and thermal transport properties of thermoelectric materials since it can generate point defects as well as control the phase evolution behavior. Herein, we investigated the Ti addition effect on the grain growth during melt spinning and thermoelectric transport properties of Hf0.5Zr0.5NiSn0.98Sb0.02 half-Heusler compound. The characteristic grain size of melt-spun ribbons was reduced by Ti addition, and very low lattice thermal conductivity lower than 0.27 W m−1 K−1 was obtained within the whole measured temperature range (300–800 K) due to the intensified point defect (substituted Ti) and grain boundary (reduced grain size) phonon scattering. Due to this synergetic effect on the thermal transport properties, a maximum thermoelectric figure of merit, zT, of 0.47 was obtained at 800 K in (Hf0.5Zr0.5)0.8Ti0.2NiSn0.98Sb0.02.

Scanning Thermal Microscopy and Ballistic Phonon Transport in Lateral Spin Valves.

Using scanning thermal microscopy, we have mapped the spatial distribution of temperatures in an operating nanoscale device formed from a magnetic injector, an Ag connecting wire, and a magnetic detector. An analytical model explained the thermal diffusion over the measured temperature range (2-300K) and injector-detector separation (400-3000nm). The characteristic diffusion lengths of the Peltier and Joule heat differ remarkably below 60K, a fact that can be explained by the onset of ballistic phonon heat transfer in the substrate.

Quantum coherence modulation in bismuth selenide topological insulator thin film by ion irradiation

The robust surface states of bismuth selenide (Bi2Se3) topological insulator (TI) that could potentially be harnessed for quantum computing and spintronics applications are often eclipsed by defect-induced bulk carriers. With the objective of suppressing the electronic transport in the bulk, we explore the effects of ion irradiation-driven isoelectronic doping in thin films of Bi2Se3 with 600 keV antimony (Sb+) ions at 45° oblique incidence. The distribution of Sb+ ions introduced into the system has been mapped using Rutherford backscattering spectroscopy. The heavy Sb+ ion irradiation has been observed to cause a change from parabolic magnetoresistance to linear magnetoresistance behavior in the irradiated films due to mobility fluctuations. Subsequent annealing in selenium environment has been found to reverse the damage produced by the irradiation, but with significant modifications in the quantum coherence signatures. Weak antilocalization behavior has been observed in the weak magnetic field limit and has been analyzed within the purview of the Hikami-Larkin-Nagaoka model. It has been found that the channel-separated Bi2Se3 film becomes completely channel-mixed due to the induced defects, yielding a system with a single coherent channel upon irradiation. In the as-deposited film, the temperature-dependent power law decay of the coherence length has been found to have two different exponents within the measured temperature range. On the other hand, the irradiated-annealed film has a single decay exponent which has been found to tend to − 0.5, indicating that electron-electron interaction is the only de-phasing mechanism involved. This work establishes the effectiveness of ion irradiation in tuning the quantum coherence phenomena in Bi-based TI systems.

Frequency sweep extension using the Kerr effect for static temperature measurement range enhancement in Chirped Pulse φ-OTDR.

In Chirped Pulse φ-OTDR systems used for sensing temperature or strain along an optical fiber, the largest disturbance between two single-shot measurements that can reliably be detected depends on the range of frequencies swept by the chirped pulse. If electrical modulation is used to generate the laser frequency sweep, the achievable sweeping range is limited by the electrical components, leading to a narrow measurement range for static measurements. In this work, we demonstrate the extension of the frequency range of a chirped laser pulse by all-optical means using evenly spaced frequency sidebands generated via the Kerr effect to improve the Chirped Pulse φ-OTDR measurement range. We report chirp extensions by factors up to 13 and apply the effect to achieve a sixfold increase in the measurement range of a Chirped Pulse φ-OTDR system measuring the temperature of a random fiber grating array. The method described in this paper can be applied to other optical systems utilizing chirped laser pulses and allow for variable extension of their chirping range.

Ionic and Thermal Transport in Na-Ion-Conducting Ceramic Electrolytes

We have studied the ionic and thermal transport properties along with the thermodynamic key properties of a Na-ion-conducting phosphate ceramic. The system Na1+xAlxTi2−x(PO4)3 (NATP) with x = 0.3 was taken as a NASICON-structured model system which is a candidate material for solid electrolytes in post-Li energy storage. The commercially available powder (NEI Coorp., USA) was consolidated using cold isostatic pressing before sintering. In order to compare NATP with the “classical” NASICON system, Na1+xZr2(SiO4)x(PO4)3−x (NaZSiP) was synthesized with compositions of x = 1.7 and x = 2, respectively, and characterized with regard to their ionic and thermal transport behavior. While ionic conductivity of the NaZSiP compositions was about more than two orders of magnitude higher than in NATP, the thermal conductivity of the NASICON compound showed an opposite behavior. The room temperature value was about a factor two higher in NATP compared to NaZSiP. While the thermal conductivity decreases with increasing temperature in NATP, it increases with increasing temperature in NaZSiP. However, the overall change of this thermal transport parameter over the measured temperature range from room temperature up to 800 °C appeared to be relatively small.

Rotation of a Charged Spin Probe in Room-Temperature Ionic Liquids.

X-band electron paramagnetic resonance spectroscopy has been used to investigate the rotational diffusion of a stable, positively charged nitroxide 4-trimethylammonium-2,2,6,6-tetramethylpiperidine-1-oxyl iodide (Cat-1) in a series of 1-alkyl-3-methylimidazolium tetrafluoroborate room-temperature ionic liquids (RTILs) having alkyl chain lengths from two to eight carbons. The rotation of Cat-1 is anisotropic with the preferential axis of rotation along the NO• moiety. The Stokes-Einstein-Debye law describes the mean rotational correlation time of Cat-1, assuming that the hydrodynamic radius is smaller than the van der Waals radius of the probe. This implies that the probe rotates freely, experiencing slip boundary condition, which is solvent-dependent. The rotational correlation time of Cat-1 in RTILs can very well be fitted to a power-law functionality with a singular temperature, which suggests that the apparent activation energy of rotation exhibits non-Arrhenius behavior. Compared to the rotation of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDTO), which is neutral, the rotation of Cat-1 is several times slower. The rotational anisotropy, the ratio of the rotational times of pDTO and Cat-1, and the apparent activation energy indicate the transition from a homogeneously globular structure to a spongelike structure when the alkyl chain has four carbons, which is also observed in molecular dynamics computational studies. For the first time, we have been able to show that the rotational correlation time of a solute molecule can be analyzed in terms of the Cohen-Turnbull free volume theory. The Cohen-Turnbull theory fully describes the rotation of Cat-1 in all ionic liquids in the measured temperature range.

Response Comparison of Resistor- and Si FET-Type Gas Sensors on the Same Substrate

The response characteristics of a field-effect transistor (FET)-type gas sensor are compared with those of the resistor-type gas sensor fabricated on the same Si substrate. Both types of gas sensors have the same sensing material prepared by the same process. Indium oxide (In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) film is adopted as a sensing material to sense NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas. The two types of gas sensors have different response characteristics depending on the operating condition. The resistor-type gas sensor shows relatively constant response at all operating currents, and the Si FET-type gas sensor shows high response in the subthreshold region. Both types of sensors have the highest response at 105 °C, and the current of the Si FET-type gas sensor can change up to ~ 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> times at 500 ppb of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas, which is ~8.15 times higher than that of the resistor-type gas sensor. In addition, when the pre-bias method ( V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pre</sub> = -3 V) is applied to the Si FET-type gas sensor, the response of the Si FET-type sensor overwhelms that of the resistor-type sensor over the entire measurement temperature and concentration range.