Study On Transient High Temperature Measurement And Temperature Stabilization Characteristics Of Carbothermal Pulse Process

The carbothermal pulse process is a novel high entropy alloy nanoparticle preparation process,which was first proposed in 2018,the process temperature conditions of this process are very strict: the process temperature span is large(room temperature ～ 3000K),the heating/annealing time is short(ms ～ s),the heating/annealing rate is fast(10^3 ～ 10^5k/s)and the temperature control accuracy is required to be high(full range ≤5%).For such occasions where the temperature rises and falls instantaneously and the temperature varies greatly,conventional temperature measurement methods(thermocouple,CCD image temperature measurement,etc.)cannot meet the requirements in terms of response speed and accuracy at the same time.In addition,due to the process was proposed for a short period of time,the temperature of the process is mainly obtained by passive temperature measurement,the steady-state temperature change law of the carbon carrier under different process parameters is still unclear,without the guidance of the research on the steady-state temperature variation of the process,the temperature prediction and the process temperature controllable adjustment can not be realized.This paper focuses on rapid and accurately obtaining temperature changes in the carbothermal pulse process through multi-spectral radiation temperature measurement techniques and the steady-state temperature characteristics of the process through experiments and simulation,specific research contents:(1)An improved strategy for the "Improved Single Target + Improved Sparrow Algorithm" is proposed to achieve high-precision fast solving temperature.First,based on the constraint optimization,a multi-spectral radiation thermometry single target constraint optimization mathematical model based on minimum mean square error is constructed,and the solution effects of the interior point penalty function method and the classical sparrow algorithm on the singleobjective model are studied respectively by using six typical emissivity distribution models.Although the interior point penalty function method has high solution accuracy,the solution speed is slow,and it cannot realize the rapid temperature measurement in the carbothermal pulse process.Although the classical sparrow algorithm has a fast calculation speed,the solution accuracy is low and the solution stability is poor.Then,the reasons for the low solution accuracy and poor solution stability of the classical sparrow algorithm are analyzed,and the improvement is made from two aspects of the single objective function and the sparrow algorithm.The improved strategy has a certain improvement in calculation stability,calculation accuracy and solution efficiency.The average calculation time of each temperature value is 0.5s,which can realize the rapid detection of the temperature in the carbothermal pulse process.(2)Carry out experimental research on the steady-state temperature characteristics of the carbothermal pulse process.Firstly,a simulation experiment system of the carbothermal pulse process was built,in which the spectral information sampling interval of the optical path system was 1.35 ms per piece of spectral information on average,and more than 1500 pieces of effective spectral information could be collected in the process lasting 2s,with high sampling accuracy.Then,the carbothermal pulse process experiment under typical process parameters was carried out.Based on the improvement strategy proposed above,the temperature change of the carbothermal pulse process was successfully obtained and analyzed.(3)A series of carbothermal pulse process experiments were carried out under different process parameters(voltage,normal temperature resistance)to study the variation law of steady temperature-voltage-normal temperature resistance,a series of conclusions can be used to guide the follow-up research of carbothermal pulse process.(4)According to the analysis,the experimental method is not a good way to study the steady-state temperature characteristic,so the steady-state temperature characteristic of the process of carbothermal pulse is studied by means of simulation based on COMSOL Multiphysics.In order to make the COMSOL simulation results more accurate,the experiment of measuring the conductivitytemperature relationship of carbon nanofiber film was carried out and the conductivity-temperature data were fitted to a sigmoid function for COMSOL simulation.The temperature simulation analysis of the carbothermal pulse process under typical process parameters was carried out.The area correction coefficient = 3.7 was obtained by using the experimental data to correct the simulation results,the rationality of the area correction coefficient is verified by the temperature experiment data under other process parameters.(5)The steady-state temperature simulation study of the carbothermal pulse process under different voltages and room temperature resistances was carried out,and the simulation analysis results were in good agreement with the experimental results;the reasons for the poor fitting effect of four low-precision mechanism models were analyzed.To obtain the T(U,R)prediction model,first of all,the parameter range of the simulation analysis was broadened,and the T(U,R)prediction model was obtained by using the polynomial model Poly2 D in the numerical fitting and the neural network respectively.The goodness of fit is greater than 0.99,indicating that the model has high prediction accuracy and a wide application range.The experimental data is used to verify the accuracy of the two models in predicting temperature.