Temperature Coefficient Research Articles

Particle size effect on surface/interfacial tension and Tolman length of nanomaterials: A simple experimental method combining with theoretical.

Surface tension and interfacial tension are crucial to the study of nanomaterials. Herein, we report a solubility method using magnesium oxide nanoparticles of different radii (1.8-105.0nm, MgO NPs) dissolved in pure water as a targeted model; the surface tension and interfacial tension (and their temperature coefficients) were determined by measuring electrical conductivity and combined with the principle of the electrochemical equilibrium method, and the problem of particle size dependence is discussed. Encouragingly, this method can also be used to determine the ionic (atomic or molecular) radius and Tolman length of nanomaterials. This research results disclose that surface/interfacial tension and their temperature coefficients have a significant relationship with particle size. Surface/interfacial tension decreases rapidly with a radius <10nm (while the temperature coefficients are opposite), while for a radius >10nm, the effect is minimal. Especially, it is proven that the value of Tolman length is positive, the effect of particle size on Tolman length is consistent with the surface/interfacial tension, and the Tolman length of the bulk does not change much in the temperature range. This work initiates a new era for reliable determination of surface/interfacial tension, their temperature coefficients, ionic radius, and Tolman length of nanomaterials and provides an important theoretical basis for the development and application of various nanomaterials.

Operation up to 225°C of NiO/ β-(Al0.21Ga0.79)2O3 /Ga2O3 Heterojunction Lateral Rectifiers

The characteristics of NiO/ β-(Al0.21Ga0.79)2O3 /Ga2O3 heterojunction lateral geometry rectifiers with the epitaxial layers grown by Metal Organic Chemical Vapor Deposition were measured over the temperature range from 25-225°C. The forward current increased with temperature, while the on-state resistance decreased from 360 Ω•cm2 at 25°C to 30 Ω.cm2 at 225°C. The forward turn-on voltage was reduced from 4 V at 25°C to 1.9 V at 225°C. The reverse breakdown voltage at room temperature was ~4.2 kV, with a temperature coefficient of -16.5 V/K. This negative temperature coefficient precludes avalanche being the breakdown mechanism and indicates that defects still dominate the reverse conduction characteristics. The corresponding power figures-of-merit were 0.27-0.49 MW.cm-2. The maximum on/off ratios improved with temperature from 2105 at 25°C to 3107 at 225°C when switching from 5 V forward to 0 V. The high temperature performance of the NiO/ β-(Al0.21Ga0.79)2O3 /Ga2O3 lateral rectifiers is promising if the current rate of optimization continues.

Semiconductor Nanoparticle Anchored Single-Walled Carbon Nanotubes for a Bolometer.

The bolometer is developed using single-walled carbon nanotubes (SWCNT) anchored with semiconductor nanoparticles of cadmium sulfide, stannous disulfide, and zinc oxide (ZnO). The bolometric responses were recorded at varying temperatures from 10 K to room temperature. The anchored SWCNTs provided a higher temperature coefficient of resistance (TCR) than pristine SWCNTs. The largest TCR is recorded from SWCNTs/ZnO (-0.11%/K) at room temperature, which is 200% higher than pristine SWCNTs. The largest photoresponsivities of SWCNTs/ZnO under near-infrared (NIR) and wide wavelength source (200-1200 nm) illuminations are 5.06 and 37.51 mV/W, respectively. The extraordinary performance of SWCNTs/ZnO stands out at ∼17 × 104% under IR illumination. The study presents a significant advancement in the development of high-performance SWCNT bolometric materials by anchoring with semiconductor nanoparticles.

Design and Analysis of Mode-Matched Decoupled Mass MEMS Gyroscope with Improved Thermal Stability

Abstract This paper presents an efficient design approach for microelectromechanical systems (MEMS) gyroscope considering the design constraint of MEMSCAP's Silicon-on-Insulator Multi-User MEMS Processes (SOIMUMPs). A design for a decoupled mass MEMS resonant gyroscope with tuning electrodes is presented to minimize cross-axis coupling and optimize the gyroscope's performance. The device features a size of 1.8 ×2.772 mm^2. A decoupled mass MEMS gyroscope has been designed using a novel mechanical beam configuration that optimizes the structural design to reduce unwanted interactions between drive and sense axes motions. Mode order has been achieved by obtaining the first two modes as drive and sense modes at 9946.3 Hz and 10202.7 Hz, respectively. Parallel plate electrostatic tuning electrodes have been added to adjust and match the drive and sense modes at the resonant frequencies of 9946 Hz. This mode matching is crucial for optimizing gyroscope performance, accuracy, and sensitivity. The effects of temperature variation on the performance of the designed decoupled mass MEMS gyroscope have been investigated, particularly in terms of its mode-matched operation achieved using tuning electrodes. Finite Element Method (FEM) simulations were conducted, demonstrating that thermal stability was achieved, and mode-matched operation was maintained within the temperature range of -40 ºC to 80 ºC. The gyroscope exhibits enhanced performance compared to existing MEMS gyroscopes under mode-matched conditions, featuring a lower temperature coefficient of frequency (TCF) at 0.0415 Hz/ºC in the drive mode and 0.0165 Hz/ºC in the sense mode. FEM analysis for the fabrication process tolerances has been done, where MEMS gyroscope’s resonant frequencies, output capacitance, output displacement, and sense mode quality factor have shown negligible changes to fabrication process tolerances. Transient analysis was conducted using CoventorWare MEMS+ 3D schematic, which was integrated with MATLAB Simulink to measure the MEMS gyroscope’s output response, which corresponded with the varying input angular velocity signal.

Tensile and compressive properties of bamboo scrimber under different temperature conditions

AbstractBamboo scrimber demonstrates vulnerability to environmental temperature fluctuations, such as exposure to cold or fire, when deployed in structural applications. Consequently, its mechanical properties can substantially diverge from the intended design values under varying thermal conditions. This study aims to study the tensile and compressive properties of bamboo scrimber under different temperatures to provide data support for studying bamboo scrimber under low and high temperatures. The compressive properties of bamboo scrimber under temperatures ranging from −30°C to 250°C and the tensile properties under −20°C to 250°C were determined by a series of tests with a total of 125 specimens. The results show that the mass loss of bamboo scrimber increases gradually with the increase in temperature, and the increasing trend intensifies after 120°C. With the increase of temperature, the failure mode of the specimens under compression changes from the bottom compression cracking damage to the local destabilization of longitudinal fibers, while the tensile damage modes aren't influenced by temperature, and both “straight‐line” and “folded‐line” types of damage modes occur at different temperatures. The tensile and compressive strengths and elastic modulus of the specimens decreased with the increase in temperature, and the strength was more susceptible to the temperature than the elastic modulus: a rise in temperature from 20°C to 250°C resulted in a reduction of compressive strength and tensile strength by 80.80% and 84.11%, respectively, the compressive modulus and tensile modulus experienced decreases of 49.51% and 53.28%. Furthermore, equations of temperature influence coefficients of strength and elastic modulus were established based on the test results.Highlights Bamboo scrimber's mechanical properties under different temperatures are studied. Tendency and explanation of temperature influence coefficients are analyzed. Temperature coefficient equations for strength and elastic modulus are proposed.

Linear Expansion Temperature Coefficient of Glass Ceramic Materials Based on MoSi2

Linear Expansion Temperature Coefficient of Glass Ceramic Materials Based on MoSi2

High-performance GeSi/Ge multi-quantum well photodetector on a Ge-buffered Si substrate.

This work demonstrates a high-performance photodetector with a 4-cycle Ge0.86Si0.14/Ge multi-quantum well (MQW) structure grown by reduced pressure chemical vapor deposition techniques on a Ge-buffered Si (100) substrate. At -1 V bias, the dark current density of the fabricated PIN mesa devices is as low as 3 mA/cm2, and the optical responsivities are 0.51 and 0.17 A/W at 1310 and 1550 nm, respectively, corresponding to the cutoff wavelength of 1620 nm. At the same time, the device has good high-power performance and continuous repeatable light response. On the other hand, the temperature coefficient of resistance (TCR) of the device is as high as -5.18%/K, surpassing all commercial thermal detectors. These results indicate that the CMOS-compatible and low-cost Ge0.86Si0.14/Ge multilayer structure is promising for short-wave infrared and uncooled infrared imaging.

Characterization of Magnetoresistive Shunts and Its Sensitivity Temperature Compensation

The main purpose of the paper is to show how a magnetoresistive (MR) element can work as a current sensor instead of using a Wheatstone bridge composed by four MR elements, defining the concept of a magnetoresistive shunt (MR-shunt). This concept is reached by considering that once the MR element is biased at a constant current, the voltage drop between its terminals offers information, by the MR effect, of the current to be measured, as happens in a conventional shunt resistor. However, an MR-shunt has the advantage of being a non-dissipative shunt since the current of interest does not circulate through the material, preventing its self-heating. Moreover, it provides galvanic isolation. First, we propose an electronic circuitry enabling the utilization of the available MR sensors integrated into a Wheatstone bridge as sensing elements (MR-shunt). This circuitry allows independent characterization of each of the four elements of the bridge. An independently implemented MR element is also analyzed. Secondly, we propose an electronic conditioning circuit for the MR-shunt, which allows both the bridge-integrated element and the single element to function as current sensors in a similar way to the sensing bridge. Third, the thermal variation in the sensitivity of the MR-shunt, and its temperature coefficient, are obtained. An electronic interface is proposed and analyzed for thermal drift compensation of the MR-shunt current sensitivity. With this hardware compensation, temperature coefficients are experimentally reduced from 0.348%/°C without compensation to −0.008%/°C with compensation for an element integrated in a sensor bridge and from 0.474%/°C to −0.0007%/°C for the single element.

A Study of the Thermal Management and Discharge Strategies of Lithium-Ion Batteries in a Wide Temperature Range

The performance of lithium-ion batteries is greatly influenced by various factors within their operating environment, which can significantly impact their overall efficiency and effectiveness. In this paper, a multi-physics field electrochemical thermal model is established to measure the physical parameters of a battery module during the charge/discharge process. The effects of working temperature, current rate, and convective heat transfer coefficient are investigated by establishing an electrochemical and thermal model. The results are obtained by conducting numerous parameterized scans to analyze the system’s state across various operating conditions, enabling the determination of its temperature and the selection of appropriate cooling measures accordingly. Based on the internal and external conditions of battery operation, parameter selection corresponding to the operating range is divided into several stages, with thermal management strategies provided for each stage. The existing framework facilitates the design of battery packs equipped with efficient thermal management strategies, thereby enhancing the battery systems’ reliability and performance. Furthermore, it aids in establishing optimal operational and safety boundaries for batteries.

Evaluation of in-plane architecture in a thermo-electrochemical cell with nanostructured and porous Sb:SnO2 electrodes

Thermo-electrochemical cells (TECs) are able to convert heat into electricity. They are formed by two electrodes (typically Pt) separated by a redox electrolyte (usually 0.4 M aqueous ferro/ferricyanide). The widely adopted architecture of TECs consists of the two electrodes separated by an electrolyte channel. To our knowledge, no studies have been reported exploring a different architecture. Here, we evaluate an alternative configuration, which comprises a substrate with the two electrodes at its ends and with the electrolyte added on the top contacting both electrodes, forming a planar configuration. We explore first the use of the standard Pt electrodes deposited on top of a conductive glass substrate. Then, we replace the Pt by nanostructured and porous Sb-doped SnO2. The planar configurations are compared with their corresponding typical architectures using the common ferro/ferricyanide electrolyte. It was found that the planar TEC with Sb:SnO2 reached a temperature coefficient of 1.76 mV/K, higher than the value obtained in the standard configuration with Sb:SnO2 (1.21 mV/K), and also higher than the planar architecture with Pt electrodes, which showed the typical value for the ferro/ferricyanide electrolyte (1.45 mV/K). As a consequence of this significantly larger value, a 29.7 % higher maximum power output than the planar TEC with Pt was observed. Our study identifies for the first time interesting new features when a planar architecture is employed, opening the door to explore in more detail this alternative configuration in TECs.

A theory and analysis of the impact of gas in the dynamical behavior of the molten salt research reactor leading to the computation of the "gas coefficients of reactivity"

Background Molten salt reactors, and other types of circulating, liquid fueled, nuclear reactors contain a certain amount of gas entrained in their liquid nuclear fuel. This gas induces an effect on the nuclear and dynamical behavior of the reactor as a whole. Gas voids respond to variation in temperature and pressure differently than liquids. When the gas voids in the reactor working fluid expand, the nuclear fuel is pushed from the core. Likewise, when the gas voids contract, more nuclear fuel enters into the core. Methods This paper examines the interplay of gas void fraction and reactivity in a molten salt reactor, and attempts to elucidate the dynamical response of the void fraction and the reactivity of the system to perturbation in system temperature, pressure, and gas quantity. A theory is presented that aims at describing the relationship between reactivity and gas behavior. This theory is then applied to the Molten Salt Research Reactor (MSRR) design, a facility currently under construction at Abilene Christian University campus. Results A result of this paper is the temperature and void fraction parameterized gas coefficients of reactivity for the Molten Salt Research Reactor. Conclusions The presence of voids accounts for 5-30% of the total temperature coefficient of reactivity, demonstrating their non-trivial contribution. Additionally, the study emphasizes the importance of considering gas content in MSR physics, especially in the context of pressure transients and system reactivity during pump trips. The initial system pressure, particularly in designs like the MSRR operating at sub-atmospheric pressures, is crucial due to its influence on reactivity changes during rapid pressure increases.

Insight into the Physical Properties of the Chalcogenide XZrS3 (X = Ca, Ba) Perovskites: A First-Principles Computation

AbstractThis study investigates the structural, mechanical, optical, thermal, and electronic properties of the ionic semiconducting materials XZrS3 (X = Ca, Ba) within the framework of density functional theory (DFT). Here, the elastic constants, modulus (bulk, shear, Young's), ratios (Pugh, Poisson) and elastic anisotropy for XZrS3 (X = Ca, Ba) are studied. Furthermore, the electronic, optical, and thermal properties for XZrS3 (X = Ca, Ba) are regenerated and designed using the values obtained with Cambridge Serial Total Energy Package (CASTEP) software. The calculated lattice parameters show excellent agreement with theoretical and experimental values. The elastic stiffness constants confirm the mechanical stability of both compounds. Although XZrS3 (X = Ca, Ba) is elastically anisotropic, it has little optical anisotropy. The electronic band structures of the material exhibit direct-bandgap semiconducting behavior, with values of 1.3 eV (CaZrS3) and 1.1 eV (BaZrS3) using the generalized gradient approximation (GGA), respectively, which is ideal for solar cell (0.9–1.56 eV) and optoelectronic device applications. Bandgap values of 1.9 eV and 1.6 eV are found for CaZrS3 and BaZrS3, respectively, using the Heyd–Scuseria–Ernzerhof HSE06 functional, which is consistent with previous theoretical and experimental bandgap results. The optical properties including dielectric function, refractive index, absorption coefficient, reflectivity, and loss function are characterized using the GGA of Perdew–Burke–Ernzerhof (GGA-PBE) and HSE06 methods and are discussed in detail. Because of the relatively low Debye temperature (D), thermal conductivity of the lattice (kph), and minimum thermal conductivity (Kmin), the studied materials can be used as thermal barrier coating (TBC) materials. The capacity of heat, Debye temperature, and thermal coefficient of expansion are all computed.

Temperature effects on the structure of lead metasilicate glass, supercooled liquid, crystal, and liquid: Vibrational anharmonicity and configurational transformations analyzed by molecular dynamics and Raman scattering

Raman spectroscopy and Molecular Dynamics (MD) simulations were employed to explore in detail the effects of temperature on the four stages of the PbO∙SiO2 system: glass, supercooled liquid, crystalline phases, and liquid. The Qn distribution up to 1153 K and the wavenumber temperature coefficients derived from vibrational anharmonicity were determined from the Raman data, whereas the structural transformation reflected in changes in the Qn population distribution up to 2400 K was inferred from MD simulations. The results indicate that reversible configurational transformations occur only in the higher temperature ranges of the supercooled liquid and more notably in the liquid state. During these transformations, the increase in the Q0 and Q1 populations occurs at the expense of the Q3 and Q4 populations. On the other hand, only vibrational anharmonicity was observed in the glass and crystalline states.

A Systematic Study of the Temperature Dependence of the Dielectric Function of GaSe Uniaxial Crystals from 27 to 300 K

We report the temperature dependences of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose–Einstein statistical factor and the temperature coefficient to describe the electron–phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and pz orbitals at the Γ-point.

Optimization of electrical transport and magnetoresistance of La0.72Ca0.28-xPbxMnO3 ceramics by Pb2+ doping

Here, La0.72Ca0.28-xPbxMnO3 (LCPMO, 0 ≤ x ≤ 0.06) polycrystalline ceramics are prepared by the sol-gel method and the influence of Pb2+ doping on microstructure, chemical composition, and electrical transport properties of LCPMO ceramics is systematically investigated. The study was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and four-probe method. The four-probe test shows that all samples have MIT (metal-insulator transition) behavior, and the peak resistance gradually decreases with the increase of Pb2+ doping amount. With the increase of Pb2+ doping amount, the temperature coefficient of resistance (TCR) and magnetoresistance (MR) first increased and then decreased, the TCR increased from 24.6 % to 36.5 %·K−1, and the MR value increased from 47 % to 71.5 %, and both corresponded to high temperature direction. Referring to previous studies, higher TCR and MR values near room temperature are what researchers have been pursuing for a long time. it can be seen that the LCPMO ceramics prepared in this article can have good application prospects in infrared detection and magnetic storage.

Printed Thick Film Resistance Temperature Detector for Real-Time Tube Furnace Temperature Monitoring

Accurately acquiring crucial data on tube furnaces and real-time temperature monitoring of different temperature zones is vital for material synthesis technology in production. However, it is difficult to achieve real-time monitoring of the temperature field of tube furnaces with existing technology. Here, we proposed a method to fabricate silver (Ag) resistance temperature detectors (RTDs) based on a blade-coating process directly on the surface of a quartz ring, which enables precise positioning and real-time temperature monitoring of tube furnaces within 100–600 °C range. The Ag RTDs exhibited outstanding electrical properties, featuring a temperature coefficient of resistance (TCR) of 2854 ppm/°C, an accuracy of 1.8% FS (full scale), and a resistance drift rate of 0.05%/h over 6 h at 600 °C. These features ensured accurate and stable temperature measurement at high temperatures. For demonstration purposes, an array comprising four Ag RTDs was installed in a tube furnace. The measured average temperature gradient in the central region of the tube furnace was 5.7 °C/mm. Furthermore, successful real-time monitoring of temperature during the alloy sintering process revealed approximately a 20-fold difference in resistivity for silver-palladium alloys sintered at various positions within the tubular furnace. The proposed strategy offers a promising approach for real-time temperature monitoring of tube furnaces.

A 1.65‐nW 11.14‐ppm/°C self‐biased subthreshold CMOS voltage reference with temperature compensation circuit

SummaryThis paper presents a subthreshold CMOS voltage reference (VR) that utilizes self‐biased circuits. This voltage reference includes temperature compensation circuits to expand its operating temperature range and reduce its temperature coefficient. The proposed CMOS voltage reference is designed using a standard 0.18‐μm CMOS process and has a small area of only 0.005 mm2. Post‐layout simulation results demonstrate that the power consumption of the circuit at room temperature (25°C) is only 1.65 nW at a power supply voltage of 1 V. In this case, the voltage reference output is 316.56 mV, with an average temperature coefficient (TC) of 11.14 ppm/°C in a wide temperature range from −40°C to 140°C. Furthermore, the line sensitivity (LS) of the circuit is 0.024%/V, and the power supply rejection ratio (PSRR) of the circuit is −86.5 dB at 10 Hz. In summary, the subthreshold CMOS voltage reference structure proposed in this paper demonstrates excellent performance characteristics, such as low power consumption, a small area, and high‐temperature stability. These features make it a promising candidate for voltage reference for low‐power applications with significant changes in environmental temperature.

Study on Mn3O4 - La1-xCaxMnO3 composite ceramics with high temperature coefficient of resistance in large temperature range

Study on Mn3O4 - La1-xCaxMnO3 composite ceramics with high temperature coefficient of resistance in large temperature range

Performance analysis of a battery thermal management system based on phase change materials with micro heat pipe arrays

Lithium-ion battery packs generate high-level heat under harsh and rigorous conditions. The inadequate heat dissipation results in high pack temperature above the safe operating range. This study investigates an efficient and cost-effective battery thermal management system based on phase change materials and a micro heat pipe array. The battery is treated as a single domain. A battery pack with six series stacked batteries is analyzed using the Newman-Tiedemann-Gu-Kim model. The thermal performance of a battery thermal management system is analyzed using phase change materials with various melting temperature values, ambient temperature, and convective heat transfer coefficients of micro heat pipe arrays. Results show that the maximum temperature of the cooling system with micro heat pipe arrays and phase change materials is 33.8 °C, which is reduced by 22.3 % and 7.8 % compared to the air-cooled and cooling system with micro heat pipe arrays. At forced convection of 50 W·m−2·K−1, the maximum battery temperature values for the phase change material RT31, RT35, and RT42 are reduced by 11.8 %, 8.9 %, and 5.4 % compared to those at forced convection of 5 W·m−2·K−1. Under short-circuit conditions, the cooling system with micro heat pipe arrays and cooling system with micro heat pipe arrays − phase change materials reduce the maximum battery temperature by 12.4 % and 29.9 % compared to the air-cooled system. Results show that the developed model for the battery thermal management system provides a reference for designing phase change materials with micro heat pipe arrays.

Diamond with Sp2-Sp3 composite phase for thermometry at Millikelvin temperatures

Temperature is one of the seven fundamental physical quantities. The ability to measure temperatures approaching absolute zero has driven numerous advances in low-temperature physics and quantum physics. Currently, millikelvin temperatures and below are measured through the characterization of a certain thermal state of the system as there is no traditional thermometer capable of measuring temperatures at such low levels. In this study, we develop a kind of diamond with sp2-sp3 composite phase to tackle this problem. The synthesized composite phase diamond (CPD) exhibits a negative temperature coefficient, providing an excellent fit across a broad temperature range, and reaching a temperature measurement limit of 1 mK. Additionally, the CPD demonstrates low magnetic field sensitivity and excellent thermal stability, and can be fabricated into probes down to 1 micron in diameter, making it a promising candidate for the manufacture of next-generation cryogenic temperature sensors. This development is significant for the low-temperature physics researches, and can help facilitate the transition of quantum computing, quantum simulation, and other related technologies from research to practical applications.