Thermal characteristic evolution of lithium-ion batteries during the whole lifecycle

This work extensively investigates the thermal characteristic evolution of lithium-ion batteries under different degradation paths,and the evolution mechanism through multi-angle characterization is revealed.Under different degradation paths,the evolution trend of temperature rise rate remains unchanged with respect to depth of discharge during the adiabatic discharge process,albeit to varying degrees of alteration.The temperature rise rate changes significantly with aging during the adiabatic discharge process under low-temperature cycling and high-rate cycling paths.The total heat generation rate,irreversible heat generation rate,and reversible heat generation rate exhibit similar evolution behavior with aging under different degradation paths.The interval range of endothermic process of reversible electrochemical reactions increases and the contribution of irreversible heat to the total heat increases with aging.To further standardize the assessment of different degradation paths on the thermal characteristics,this work introduces the innovative concept of“Ampere-hour temperature rise”.In low-temperature cycling and high-rate cycling paths,the ampere-hour temperature rise increases significantly with aging,particularly accentuated with higher discharge rates.Conversely,in high-temperature cycling and high-temperature storage paths,the ampere-hour temperature rise remains relatively stable during the initial stages of aging,yet undergoes a notable increase in the later stages of aging.The multi-angle characterization reveals distinct thermal evolution behavior under different degradation paths primarily attributed to different behavior changes of severe side reactions,such as lithium plating.The findings provide crucial insights for the safe utilization and management of lithium–ion batteries throughout the whole lifecycle.

Effect of loading rates on the characteristics of thermal damage for mudstone under different temperatures

The uniaxial compression tests for mudstone specimens are carried out with four different loading rates from room temperature to 400℃ by using the Rock Mechanics Servo-controlled Testing System MTS810 and high temperature furnace MTS652.02.The mechanical properties of mudstone with various loading rates are studied under different temperature conditions.The results show that when temperature increases from room temperature to 400℃ and loading rate is less than 0.03 mm/s,the peak strength of mudstone specimen decreases as loading rate increases,while the various peak strengths show significant differences when loading rate exceeds 0.03 mm/s.At room temperature,the elastic modulus decreases at the first time and then increases with loading rate rising.When the temperature is between200 and 400℃,the elastic modulus presents a decreasing trend with increasing loading rate.With increasing the loading rate,the number of fragments in mudstone becomes larger and even the powder is observed in mudstone with higher loading rate.Under high loading rate,the failure mode of mudstone specimens under different temperatures is mainly conical damage.

Climate adaptive thermal characteristics of envelope of residential passive house in China

Passive house has been constructed in China on a large-scale over the past couple years for its great energy saving potential.However,research indicates that there is a significant discrepancy in energy performance for heating and cooling between passive houses in different climate zones.Therefore,this research develops a comparative analysis on the energy saving potential of passive houses with the conventional around China.A sensitivity analysis of thermal characteristics of building envelope(insulation of exterior walls and windows,and airtightness)on energy consumption is further carried out to improve the climate adaptability of passive house.Moreover,the variation of energy consumption under different heat gain intensity is also compared,to evaluate the effects of envelope thermal characteristics comprehensively.Results suggest that the decrease of exterior wall insulation leads to the greatest increase in energy consumption,especially in severe cold zone in China.However,the optimal insulation may change with the internal heat gain intensity,for instance,the decrease of insulation(from 0.4 to 1.0 W/(m^(2)·K))could reduce the energy consumption by 4.65 kW·h/(m^(2)·a)when the heat gain increases to 20 W/m^(2)for buildings in Hot Summer and Cold Winter zone in China.

CFD-Based Numerical Analysis of the Thermal Characteristics of an Electric Vehicle Power Battery

Towards the end to solve the problem of temperature rise in the power battery of electric vehicles,a method based on the coupling of electrochemical,thermal and hydrodynamic aspects is implemented.The method relies on the COMSOL Multiphysics software,which is used here to simulate the thermal behaviour,the related fluid-dynamics and the life attenuation of the power battery.A 3D battery model is built assuming a cylindrical geometry.The diameter of the battery is 18 mm,and its length is 65 mm.The battery charges and discharges at 3C,and the initial temperature is 25°C.Intake flow is set to 0.5 m/s after the air of the battery is cooled.The results show that:(1)The highest temperature of the battery unit increases significantly from 1.14°C of the original nylon heat pipe to 0.17°C of the hot pipe core shaft;(2)When the short circuit of the battery is simulated,the temperature rise of the single battery is close to 20°C,the minimum rise is about 12°C,and their difference reaches 8°C.

Investigation on thermal characteristics and desensitization mechanism of improved step ladder-structured nitrocellulose

Nitrocellulose,or cellulose nitrate,has received considerable interest due to its various applications,such as propellants,coating agents and gas generators.However,its high mechanical sensitivity caused many accidents during its storage and usage in ammunition.In this work,two kinds of insensitive step ladderstructured nitrocellulose(LNC)with different nitrogen contents were synthesized.The products were characterized by FT-IR,Raman,XRD,SEM,elemental analysis,TGA,DSC,accelerating rate calorimeter analysis(ARC),and drop weight test to study their molecular structure,thermal characteristics and desensitization performance.Compared with raw nitrocellulose,LNC has a sharper exothermic peak in the DSC and ARC curves.The H50values of the two kinds of LNC increased from 25.76 to 30.01 cm for low nitrogen content and from 18.02 to 21.84 cm for high nitrogen content,respectively.The results show that the ladder-structure of LNC which provides regular molecular arrangement and a soft buffer made with polyethylene glycol could affect the energy releasing process of LNC and reduce the sensitivity of LNC.Insensitive LNC provides an alternative to be used as a binder in insensitive propellants formulation.

Experimental study on thermal characteristics of LiFePO_4 power batteries

As an important high-energy chemical power source, lithium-ion power batteries come up to application problems of thermal performance, such as extended temperature range and high power charge ＆ discharge. LiFeP04 battery is applied and developed well recently, its charge and discharge experiment at different temperatures and hybrid pulse power characterization （HPPC） test are analyzed, and the optimal temperature range of LiFeP04 battery is put forward. In order to provide experimental suggestion of power battery application and its thermal management, internal resistance, influencing factor of electromotive force and entropy change state of charge （SOC）, battery thermal characteristic of different charge ＆ discharge rates are summarized.

Martensite Aging Effect and Thermal Cyclic Characteristics in Ti-Pd and Ti-Pd-Ni High Temperature Shape Memory Alloys

The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M, and Af temperatures in Ti50Pd50-xNix (x=10, 20, 30) alloys, but no obvious thermal cycling effect was observed in Ti50Pd50Pd40Ni10 alloys and the aging effect shows a curious feature, i.e., the Af temperature does not saturate even after relatively long time aging, which is considered to be due to the occurrence of recovery recrystallization during aging.

An Experimental Study on Thermal Characteristics of Laurie Acid as a Latent Heat Storage Material during Melting Process

The objective of this study was to establish the thermal characteristics of the lauric acid (95% purity) as a latent heat storage material filled in the annulus of vertical concentric double pipe during its melting process,The temperature data were used to determine the thermal characteristics,including the temporal temperature variations and the effects of the mass flow rate and the inlet temperature of the heat transfer fluid on the heat transfer coefficient and the heat charging fraction during the melting process,The results indicated that the time to reach to heat charging fraction of 1.0 could be altered by changing the mass flow rate and the inlet temperature of the heat transfer fluid.

Welding thermal characteristics analysis with numerical simulation for thin-wall parts assembly under different conditions

In order to analyze the welding thermal characteristics problem,the multiscale finite element(FE)model of T-shape thin-wall assembly structure for different thicknesses and the heat source model are established to emphatically study their welding temperature distributions under different conditions.Simultaneously,different welding technology parameters and welding directions are taken into account,and the fillet weld for different welding parameters is employed on the thin-wall parts.Through comparison analysis,the results show that different welding directions,welding thicknesses and welding heat source parameters have a certain impact on the temperature distribution.Meanwhile,for the thin-wall assembly structure of the same thickness,when the heat source is moving,the greater the moving speed,the smaller the heating area,and the highest temperature will decrease.Therefore,the welding temperature field distribution can be altered by adjusting welding parameters,heat source parameters,welding thickness and welding direction,which is conducive to reducing welding deformation and choosing an appropriate and optimal welding thickness of thin-wall parts and relative welding process parameters,thus improving thin-wall welding structure assembly precision in the actual large-size welding structure assembly process in future.

Analysis of Thermal Characteristics for a High Speed Motorized Spindle Based on the ANSYS Workbench

The high-speed motorized spindle, as the key component of machining centers and other high-end CNC machine tools, has performance directly affecting machining accuracy. According to the internal motor character- istics of the high speed motorized spindle in the paper, two major heat sources are analyzed and quantity of heat is calculated. The finite element analysis model of motorized spindle thermal characteristics is built through ap- plying the ANSYS Workbench. The thermal steady state, heat-structure coupling characteristics is carried out based on the cooling coefficient of thermal boundary conditions, and taking heating value of the bearing and mo- tor as thermal load, the temperature field distribution and thermal deformation of the spindle system are obtained, which prepare fox＂ the next thermal error modeling

Thermal Characteristics of PVA-PANI-ZnS Nanocomposite Film Synthesized by Gamma Irradiation Method

Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases corresponding to ZnS nanoparticles, PVA and PANI. Field emission scanning electron microscopy shows the formation of agglomerated PANI along the PVA backbone, within which the ZnS nanoparticles are dispersed.UV-visible spectroscopy is conducted to measure the transmittance spectra of samples revealing the electronic absorption characteristics of ZnS and PANI nanoparticles. Photo-acoustic（PA） setup is installed to investigate the thermal properties of samples. The PA spectroscopy indicates a high value of thermal diffusivity for samples due to the presence of ZnS and PANI nanoparticles. Moreover, at higher doses, the more polymerization and formation of PANI and ZnS nanoparticles result in enhancement of thermal diffusivity.

Thermal Characteristics of Gel Grown Lanthanum Heptamolybdate crystals

Thermal characteristics of Ianthanum heptamolybdate crystals grown by gel technique, employing thermoanalytical techniques, viz. TG, DTA and DSC, are reported. It is established that the rare-earth lanthanum heptamolybdate crystals are associated with thirty water molecules;the composition being La2Mo7O24.3OH2O. It is shown that all the thirty water molecules associated with lanthanum heptamolybdate crystal are lost during its decomposition, leading to its anhydrous form. Results obtained on application of TG based models, viz. Horowitz-Metzger,Coats-Redfern and Piloyan-Novikova and of DSC based methods viz. Roger-Morris-Smith and Barret, regarding solid state reaction kinetics are also reported. The random nucleation model is shown to be the one that is relevant to the decomposition of lanthanum heptamolybdate. The kinetic parameters, viz.the order of reaction. frquency factor, energy of activation and entropy using above mentioned models are computed and shown to bear reasonably good agreement

Numerical Calculation of Transient Thermal Characteristics of Nozzle Flowmeter

This article aims to reveal the transient thermal characteristics of the solid domain in a nozzle flowmeter when measuring fluids of varying temperatures.Based on finite element method,the transient numerical calculation of the thermal characteristics of each component of the nozzle flowmeter has been conducted.The research shows that:as the fluid passes through the flowmeter,the high heat flux area inside the nozzle flowmeter gradually transfer from the center of the nozzle to the inlet and outlet,as well as the pressure tapping points upstream and downstream;High thermal stress zones are present near the upstream and downstream pressure tapping points and inlet and outlet area;High thermal deformation zones occur near the upstream and downstream pressure tapping points and eight slot nozzle.

Field and Thermal Characteristics of Magnetizing Fixture

This paper describes field modeling and thermal modeling for magnetizing fixture. As the detailed characteristics of magnetizing fixture can be. obtained, the efficient design of magnetizer which produce desired magnet will be possible using our modeling. For field modeling finite-element analysis is used as part of the design and analysis process for magnetizing fixture. The thermal modeling method of magnetizing fixture resistor uses multi-lumped model with equivalent thermal resistance and thermal capacitance.

Effect of Metal Contact and Rapid Thermal Annealing on Electrical Characteristics of Graphene Matrix

Development of graphene field effect transistors （GFETs） faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1-5 kΩ/□. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 kΩ/□ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process anneMing on its electrical fabrication.

Experiments and Simulation of Thermal Behaviors of the Dual-drive Servo Feed System

The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the current research of the thermal characteristics of machines mainly focuses on steady simulation. To explore the influence of thermal characterizations on the precision of a jib boring machine assembled dual-drive feed system, the thermal equilibrium tests and the research on thermal-mechanical transient behaviors are carried out. A laser interferometer, infrared thermography and a temperature-displacement acquisition system are applied to measure the temperature distribution and thermal deformation at different feed speeds. Subsequently, the finite element method （FEM） is used to analyze the transient thermal behaviors of the boring machine. The complex boundary conditions, such as heat sources and convective heat transfer coefficient, are calculated. Finally, transient variances in temperatures and deformations are compared with the measured values, and the errors between the measurement and the simulation of the temperature and the thermal error are 2 ~C and 2.5 pm, respectively. The researching results demonstrate that the FEM model can predict the thermal error and temperature distribution very well under specified operating condition. Moreover, the uneven temperature gradient is due to the asynchronous dual-drive structure that results in thermal deformation. Additionally, the positioning accuracy decreases as the measured point became further away from the motor, and the thermal error and equilibrium period both increase with feed speeds. The research proposes a systematical method to measure and simulate the boring machine transient thermal behaviors.

Resistivity and thermal infrared precursors associated with cemented backfill mass

The stability of cemented backfill mass is important to keep miners and equipment safe in underground backfill miming.The stress-strain behavior, resistivity and thermal infrared(TIR) characteristics of backfill mass under uniaxial compression were investigated. The monitoring system consisted of a TIR observation system, a stress-strain monitoring system and a resistivity measurement system. Precursory information for impending failure of cemented backfill mass was collected, including TIR, strain and resistivity precursors. The sensitivity and difference of different monitoring information to the same failure event were compared.The results show that the time-space evolution process of the resistivity and TIR is basically the same as the whole process from compression deformation to failure of backfill mass, and the time variation of resistivity and TIR is obviously characterized by stage.The resistivity precursor turns out earlier than the TIR and the strain. The resistivity relation with loading compression is anti-symmetry, decreasing as the compression stress increases before the peak strength of backfill mass. However, when the backfill mass enters into the phase of failure, the resistivity starts to increase as the stress increases. The change of the resistivity growth direction can be regarded as the resistivity-caution-point for the failure of backfill mass under uniaxial compression. It is also indicated that the TIR information mainly represents the surface temperature evolution in the process of compression before the backfill enters into the plastic-yield state. It can be a valuable tool to obtain the precursors for failure of cemented backfill mass for backfill mines.

Structural, microstructural, and thermal characterizations of a chalcopyrite concentrate from the Singhbhum shear zone, India

The structural and morphological characterizations of a chalcopyrite concentrate, collected from the Indian Copper Complex, Ghatshila, India, were carried out by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The con- centmte powder was composed mainly of free chalcopyrite and low quartz in about 3：1 weight ratio. The particle size was about 100 μm. Spectroscopic studies （FTIR, Raman, UV-visible） of the concentrate supported the XRD findings, and also revealed a marginal oxidation of the sulfide phase. The energy band gap of the sulfide was found to be 3.4 eV. Differential thermal analysis and thermogravimetry of the con- centrate showed a decomposition of chalcopyrite at 658 K with an activation energy of 208 kJ-mol 1, and two successive structural changes of silica at 848 K and 1145 K.

Thermal analysis of an innovative flat heat pipe radiator

An innovative flat heat pipe radiator was put forward, and it has the features of high efficiency of heat dissipation, compact construction, low thermal resistance, light weight, low cost, and anti-dust-deposition. The thermal analysis of the flat heat pipe radiator for cooling high-power light emitting diode （LED） array was conducted. The thermal characteristics of the flat heat pipe radiator under the different heat loads and incline angles were investigated experimentally in natural convection. An electro-thermal conversion method was used to measure the junction temperature of the LED chips. It is found that the integral temperature distribution of the flat heat pipe radiator is reasonable and uniform. The total thermal resistance of the flat heat pipe radiator varies in the range of 0.38-0.45 K/W. The junction temperatures of LED chips with the flat heat pipe radiator and with the aluminum board at the same forward current of 0.35 A are 52.5 and 75.2 ℃, respectively.

DC Characteristics of Lattice-Matched InAlN/AlN/GaN High Electron Mobility Transistors

Lattice-matched InAlN/AlN/GaN high electron mobility transistors (HEMTs) grown on sapphire substrate by using low-pressure metallorganic chemical vapor deposition were prepared, and the comprehensive DC characteristics were implemented by Keithley 4200 Semiconductor Characterization System. The experimental results indicated that a maximum drain current over 400 mA/mm and a peak external transconductance of 215 mS/mm can be achieved in the initial HEMTs. However, after the devices endured a 10-h thermal aging in furnace under nitrogen condition at 300 ℃, the maximum reduction of saturation drain current and external transconductance at high gate-source voltage and drain-source voltage were 30% and 35%, respectively. Additionally, an increased drain-source leakage current was observed at three-terminal off-state. It was inferred that the degradation was mainly related to electron-trapping defects in the InAlN barrier layer.