阅读说明：本技术 基于量热学测试的玻璃化转变脆性因子分析方法 (Glass transition brittleness factor analysis method based on calorimetric test ) 是由 余建星 刘欣 余杨 王彩妹 王华昆 李昊达 于 2020-12-28 设计创作，主要内容包括：本发明提供一种基于量热学测试的玻璃化转变脆性因子分析方法,其特征在于,为玻璃态材料设计量热学实验测试方法,利用差示量热扫描仪对物质进行热流测试,在在每次样品升温热流曲线测量中,变化不同的降温速率,控制相同的升温速率得到不同玻璃态,在确定标准玻璃态之后,为不同的玻璃态构建焓差,从而得到在不同降温速率下制备玻璃态的结构温度和激活能,最终获得物质玻璃化转变动力学参数脆性因子的数值。(The invention provides a glass-transition brittleness factor analysis method based on calorimetric test, which is characterized in that a calorimetric experimental test method is designed for a glassy material, a differential calorimetric scanner is used for carrying out heat flow test on a substance, different cooling rates are changed in each sample heating heat flow curve measurement, the same heating rate is controlled to obtain different glassy states, enthalpy difference is constructed for the different glassy states after standard glassy states are determined, so that the structural temperature and activation energy for preparing the glassy states at different cooling rates are obtained, and the numerical value of the glass-transition dynamic parameter brittleness factor of the substance is finally obtained.)

1. A glass-transition brittleness factor analysis method based on calorimetric test is characterized in that a calorimetric experimental test method is designed for a glassy state material, a differential calorimetric scanner is used for carrying out heat flow test on a substance, different cooling rates are changed in each sample heating heat flow curve measurement, the same heating rate is controlled to obtain different glassy states, and enthalpy difference is constructed for the different glassy states after standard glassy states are determined. Thereby obtaining the structural temperature and the activation energy of the prepared glass state at different cooling rates, and finally obtaining the numerical value of the brittle factor of the glass transition kinetic parameter of the substance.

2. The method for analyzing glass transition brittleness factor according to claim 1, wherein the method for analyzing glass transition brittleness factor based on calorimetric test comprises the following steps:

(1) placing the test sample in an aluminum pan and sealing the aluminum pan;

(2) calibrating a differential calorimetric scanner;

(3) measuring a sample temperature rise heat flow curve: determining a temperature testing range, changing different cooling rates in each sample heating heat flow curve measurement, and controlling the same heating rate to obtain different glass states of the tested sample, wherein the heating rates are fixed; keeping the temperature for a period of time after each temperature change to stabilize the measurement;

(4) baseline measurement: after scanning the temperature rise heat flow curve of the tested sample, taking the same aluminum plate as a test object, and testing and obtaining base line heat flow, wherein the measured temperature process is consistent with that of the sample measurement;

(5) calculating the heat capacity curve of the sample: a two-line method is utilized to make a difference between the sample heating heat flow curve and the base line ordinate so as to obtain a sample heat capacity curve;

(6) selecting standard cooling rate and standard glass state from each sample heating heat flow curve measurement, and calculating the standardStandard structure temperature corresponding to quasi-heating heat flow curveThe formula used is as follows:

in the formula, T^*-any temperature in the supercooled liquid region;

C_p-liquid-liquid phase heat capacity;

C_p-glass-glass state heat capacity;

(7) calculating the structural temperature T corresponding to the glass state obtained at other cooling rates_fThe method comprises the following steps: the enthalpy difference between the glass state heat capacity curve and the standard heat capacity curve is obtained under the condition of constructing other different cooling rates, the structural temperature of the glass state under other cooling speeds is solved by the area integral between the heat capacity curves under different cooling rates and taking the standard heating heat flow curve as the basis, and the formula is as follows:

in the formula, delta H is the enthalpy difference between the glass states obtained at a certain cooling rate and a standard cooling rate;

△C_p-the difference in heat capacity between the glassy states obtained at a certain cooling rate and the standard cooling rate;

(8) obtaining the structural temperature corresponding to the glass state at different cooling rates, and calculating the value of the activation energy h:

q＝q₀exp(-h/RT_f)

wherein R is a gas constant;

q₀-a constant;

q-cooling rate;

(9) the brittleness factor m is obtained through the glass transition activation energy and the structure temperature.

3. The method for analyzing the glass transition brittleness factor according to claim 1, wherein in the step (2), the instrument precision calibration is performed by selecting indium at a temperature range of 0-200 ℃ and selecting cyclohexane at a temperature range of-165-0 ℃.

Technical Field

The invention relates to the technical field of a novel material, namely a glass state material, in particular to a glass transition brittleness factor analysis method based on calorimetric test.

Background

Glassy materials, also known as amorphous materials, are materials with irregular arrangement of internal atoms, disordered long-range structure, and ordered short-range structure. Along with the rapid development of the material field, the glassy state material is used as a novel green material, and due to the high strength, high hardness, corrosion resistance and good photoelectric conversion efficiency of the glassy state material, the glassy state material is applied to multiple fields such as biomedicine, energy transmission, military industry, electronic communication and the like and has a value which cannot be used for producing crystalline state materials, and the application of energy-saving and environment-friendly materials such as iron-based amorphous transformers, amorphous silicon solar cells and the like at present makes a great contribution to the green sustainable economic development of China.

The preparation of crystalline materials into glassy materials must undergo a glass transition process. When the liquid is cooled to below the theoretical crystallization temperature, the liquid may select two different paths at different cooling rates, and if the liquid is cooled at a small cooling rate, the liquid is crystallized and is transformed into ordered crystals, for example, ice is formed by water solidification; if a large enough cooling rate is given to the liquid, the liquid can be prevented from forming crystals and directly changing into supercooled liquid, the molecular movement rate of the liquid is reduced along with the rapid cooling, the viscosity of the liquid can be rapidly increased and changed by more than 10 orders of magnitude within 100s, and the viscosity can reach 10 instantly¹²Pa.s, the liquid is continuously cooled, passes through a glass transition region and is finally frozen into a disordered glass state, the whole process is the glass transition behavior, and the corresponding temperature is the glass transition temperature T of the substance_g。

Due to their different structures, the rate of change of viscosity of different substances upon cooling from a high temperature region to the glass transition temperature is different, usually by a brittleness factorTo indicate how fast the viscosity of the material changes with temperature. Glass transition temperature (T) when glass transition occurs_g) The greater the rate of change of viscosity, the greater the value of m. The brittleness factor of the material is greatly related to the amorphous forming capability of the material, and the smaller the m value is, the stronger the amorphous forming capability of the material is; meanwhile, the brittleness factor is also closely related to the melting entropy and the glass transition temperature of the material. In view of the accurate measurement of the m-value, for amorphous composition design, the amorphous behaviorThe analysis has important scientific research significance, and the invention provides a method for accurately obtaining the brittleness factor by combining calorimetric measurement with fitting analysis.

In the conventional technology, the glass transition temperature of most substances is low, and the instantaneous viscosity change rate (namely, brittleness factor) at low temperature is difficult to measure and analyze by direct viscosity measurement. And in the past, using formulas for glassy materialsStructural temperature (T) for different glass states_f) And (4) calculating separately. Because the T is calculated_fIn the process, linear fitting needs to be carried out on liquid state and glass state heat capacity curves, each curve generates a certain error, and glass state calculation obtained by all cooling rates is finally accumulated into a large error. In addition, for curves cooled down at high temperature, there is an undershoot phenomenon, which makes the linear fitting of the glass state more difficult to determine. In the prior art, a more accurate and more convenient method for testing the glass transition brittleness factor is lacked.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to solve the technical problem of providing a glass transition brittleness factor analysis method based on calorimetric test. The invention adopts differential calorimetric scanning technology, provides a new method for analyzing the brittleness factor at the glass transition of the material, improves the experimental measurement precision of the brittleness factor, effectively solves the problems that the physical quantity of the brittleness factor is difficult to measure and has low precision, and provides scientific technical guidance for the accuracy of experimental measurement. In order to achieve the purpose, the invention adopts the following technical scheme:

a glass-transition brittleness factor analysis method based on calorimetric test is characterized in that a calorimetric experimental test method is designed for a glassy state material, a differential calorimetric scanner is used for carrying out heat flow test on a substance, different cooling rates are changed in each sample heating heat flow curve measurement, the same heating rate is controlled to obtain different glassy states, and enthalpy difference is constructed for the different glassy states after standard glassy states are determined. Thereby obtaining the structural temperature and the activation energy of the prepared glass state at different cooling rates, and finally obtaining the numerical value of the brittle factor of the glass transition kinetic parameter of the substance.

Further, the glass transition brittleness factor analysis method based on the calorimetric test comprises the following operation steps:

(1) placing the test sample in an aluminum pan and sealing the aluminum pan;

(2) calibrating a differential calorimetric scanner;

(3) measuring a sample temperature rise heat flow curve: determining a temperature testing range, changing different cooling rates in each sample heating heat flow curve measurement, and controlling the same heating rate to obtain different glass states of the tested sample, wherein the heating rates are fixed; keeping the temperature for a period of time after each temperature change to stabilize the measurement;

(4) baseline measurement: after scanning the temperature rise heat flow curve of the tested sample, taking the same aluminum plate as a test object, and testing and obtaining base line heat flow, wherein the measured temperature process is consistent with that of the sample measurement;

(5) calculating the heat capacity curve of the sample: a two-line method is utilized to make a difference between the sample heating heat flow curve and the base line ordinate so as to obtain a sample heat capacity curve;

(6) selecting a standard cooling rate and a standard glass state from each sample heating heat flow curve measurement, and calculating a standard structure temperature corresponding to the standard heating heat flow curveThe formula used is as follows:

in the formula, T^*-any temperature in the supercooled liquid region;

C_p-liquid-liquid phase heat capacity;

C_p-glass-glass state heat capacity;

(7) calculating the structural temperature T corresponding to the glass state obtained at other cooling rates_fThe method comprises the following steps: the enthalpy difference between the glass state heat capacity curve and the standard heat capacity curve is obtained under the condition of constructing other different cooling rates, the structural temperature of the glass state under other cooling speeds is solved by the area integral between the heat capacity curves under different cooling rates and taking the standard heating heat flow curve as the basis, and the formula is as follows:

in the formula, delta H is the enthalpy difference between the glass states obtained at a certain cooling rate and a standard cooling rate;

△C_p-the difference in heat capacity between the glassy states obtained at a certain cooling rate and the standard cooling rate;

(8) obtaining the structural temperature corresponding to the glass state at different cooling rates, and calculating the value of the activation energy h:

q＝q₀exp(-h/RT_f)

wherein R is a gas constant;

q₀-a constant;

q-cooling rate;

(9) the brittleness factor m is obtained through the glass transition activation energy and the structure temperature.

The invention solves the problems of difficult measurement and low precision of the physical quantity of the brittleness factor, and compared with the prior art, the invention has the following advantages:

1. the method can be used for carrying out brittleness factor analysis on the material which has low glass transition temperature and can not be subjected to direct viscosity measurement.

2. The experiment difficulty and the data analysis difficulty are reduced, and the brittleness factor is simply and easily measured.

3. Repeated linear fitting of multiple heat capacity curves is avoided, experiment errors of brittleness factors are reduced, and data reliability is improved.

The glass-transition brittleness factor analysis method based on calorimetric test has strong applicability and simple and convenient operation. The heat capacity measurement is carried out by using a differential calorimetric scanning technology, the glass-transition brittleness factor of different materials is calculated through the correlation between the heat capacity and the enthalpy of the materials and the correlation between the structure temperature and the activation energy and the brittleness factor, the calculation advantage of the enthalpy difference method is embodied, and scientific technical guidance is provided for the experimental measurement of the physical quantity, namely the glass-transition kinetic brittleness factor of the amorphous forming material.

Drawings

FIG. 1 is a temperature versus time course of a differential calorimetric scanner for calorimetric measurements of a sample;

FIG. 2 is a graph showing five heat capacity curves obtained by measuring a sample by a differential calorimeter at 5, 10, 20, 40, and 60K/min cooling rates, and at 20K/min heating rates, according to the temperature control plan shown in FIG. 1.

FIG. 3 is a graph showing the heat capacity difference between a temperature-increasing heat capacity curve obtained at a temperature-decreasing rate of 5, 10, 40, 60K/min and a temperature-increasing curve obtained at a temperature-decreasing rate of 20K/min;

FIG. 4 is a graph of the enthalpy difference between the glassy state at a cooling rate of 5, 10, 40, 60K/min and the glassy state at a cooling rate of 20K/min;

FIG. 5 is a graph of the inverse of the structure temperature versus cooling rate.

Detailed Description

The invention is further illustrated with reference to the following figures and examples.

The invention relates to a glass transition brittleness factor analysis method based on calorimetric test, which comprises calorimetric test of a glass forming material and fitting treatment of glass transition parameters to obtain the glass transition brittleness factor of a substance. The method designs an indirect experimental test method for the glassy state material, a differential calorimetric scanner is used for carrying out calorimetric test on a substance, five different glassy states are obtained by respectively heating the same substance at cooling rates of 5K/min, 10K/min, 20K/min, 40K/min and 60K/min, and heating heat flow curves of the different glassy states are obtained by heating the five different glassy states at the same heating rate of 20K/min. Fitting treatment and theoretical calculation are carried out on a glass state temperature-rising heat capacity curve obtained at a temperature-reducing rate of 20K/min to obtain the standard structure temperature of the substance, the glass state and the glass state standard glass state constructed enthalpy difference obtained at the temperature-reducing rate of 20K/min are obtained at the temperature-reducing rates of 5, 10, 40 and 60K/min, so that the structure temperature and the activation energy of the prepared glass state at five different temperature-reducing rates are obtained, and finally, the numerical value of a glass transition kinetic parameter brittleness factor of the substance is obtained to represent the viscosity change rate of the substance at the glass transition temperature.

The glass transition brittleness factor analysis method based on calorimetric test comprises the following operation steps:

(1) placing a test sample (in the embodiment, a 2-ethylpyridine sample) in an aluminum tray, wherein the mass of the test sample is 6-8mg, the internal heat conduction rate of the test sample is reduced due to excessive test sample, 6-8mg is used for ensuring that the test sample is uniformly heated, and the aluminum tray is sealed by a special crimping sample press after the sample is loaded, (the test sample is suitable for non-metal materials such as small molecules, macromolecules, inorganic substances and the like);

(2) calibrating an instrument: calibrating the precision of the instrument, namely selecting indium (with a standard melting point of 156.6 ℃) at a temperature range of 0-200 ℃ and cyclohexane (with a standard melting point of-87.06 ℃) at a temperature range of-165-0 ℃ to calibrate the precision of the instrument;

(3) measuring a sample heating heat flow curve: the test uses the power compensation type differential calorimeter, the apparatus has two independent heating furnaces and two independent sample chambers, the left sample chamber puts the test sample in the test process, the right sample chamber empties the aluminum disc as the reference substance; the instrument is equipped with a liquid nitrogen refrigerating system, and the testing temperature range is-170 ℃ to +200 ℃. The measurement process is shown in FIG. 1, and the selected temperature test range is T_g+50K～T_g-30K. Selecting cooling rates of 5, 10, 20, 40 and 60K/min, wherein the heating rates are all fixed at 20K/min, and through the temperature change process in the graph 1, firstly cooling the substance at the cooling rate of 5K/min to obtain the glass state at the cooling rate, and at T_gWhen the temperature reduction of 30K is stopped, the temperature is kept for one minute to stabilize the measurement, and then the glass state is heated to T by the heating rate of 20K/min_gAnd stopping heating at the temperature of 50K, keeping the temperature for one minute to stabilize the measurement, and obtaining a glass-state heating heat flow curve of the test sample at the cooling rate of 5K/min in the heating process. Cooling the substance at a cooling rate of 10K/minTo the glass state at the cooling rate, at T_gWhen the temperature reduction of 30K is stopped, the temperature is kept for one minute to stabilize the measurement, and then the glass state is heated to T by the heating rate of 20K/min_gAnd stopping heating at the temperature of 50K, keeping the temperature for one minute to stabilize the measurement, and obtaining a glass-state heating heat flow curve of the test sample at the cooling rate of 10K/min in the heating process. Cooling the material at a cooling rate of 20K/min to obtain a glass state at the cooling rate, T_gWhen the temperature reduction of 30K is stopped, the temperature is kept for one minute to stabilize the measurement, and then the glass state is heated to T by the heating rate of 20K/min_gAnd stopping heating at the temperature of 50K, keeping the temperature for one minute to stabilize the measurement, obtaining a glass state heating heat flow curve of the test sample at the cooling rate of 20K/min in the heating process, and defining the glass state obtained at the cooling rate of 20K/min as a standard glass state, wherein the standard glass state heating heat flow curve is the standard heating heat flow curve. Then cooling the substance at a cooling rate of 40K/min to obtain a glass state at the cooling rate, T_gWhen the temperature reduction of 30K is stopped, the temperature is kept for one minute to stabilize the measurement, and then the glass state is heated to T by the heating rate of 20K/min_gAnd stopping heating at the temperature of 50K, keeping the temperature for one minute to stabilize the measurement, and obtaining a glass-state heating heat flow curve of the test sample at the cooling rate of 40K/min in the heating process. Finally, cooling the substance at a cooling rate of 60K/min to obtain a glass state at the cooling rate, T_gWhen the temperature reduction of 30K is stopped, the temperature is kept for one minute to stabilize the measurement, and then the glass state is heated to T by the heating rate of 20K/min_gAnd stopping heating at the temperature of 50K, keeping the temperature for one minute to stabilize the measurement, and obtaining a glass-state heating heat flow curve of the test sample at the cooling rate of 60K/min in the heating process.

(4) Baseline measurement: after the temperature rise heat flow curve of the sample is scanned, the base line heat flow needs to be measured, hollow aluminum plates with equal mass are placed in the left furnace cavity and the right furnace cavity, and the measured temperature change process is as shown in figure 1 and is consistent with that when the temperature rise heat flow curve of the sample is measured in the step 3;

(5) obtaining a temperature rise heat capacity curve of a test sample: by using a two-line method, the ordinate of the temperature-rise heat flow curve of the test sample is subtracted from the ordinate of the baseline temperature-rise heat flow curve, so as to obtain temperature-rise heat capacity curves of glass states prepared by cooling at five different cooling rates as shown in fig. 2.

(6) Obtaining a standard heat capacity curve of the standard glass state heated at the speed of 20K/min through the cooling speed of 20K/min, and calculating the standard structure temperature of the standard glass state of the test sampleThe formula is as follows:

in the formula, T^*-any temperature in the supercooled liquid region;

C_p-the test sample is tested for heat capacity at any temperature

C_p-liquid-liquid phase heat capacity;

C_p-glass-glass state heat capacity;

(7) calculating different cooling rates to obtain the structural temperature corresponding to the glass state: obtaining standard glass state constructed enthalpy difference by using cooling rates of 5, 10, 40 and 60K/min to obtain glass state and cooling rate of 20K/min, as shown in figure 3, namely obtaining difference between a heating heat capacity curve obtained by obtaining glass states at the heating rate of 20K/min and a vertical coordinate of a standard heating heat capacity curve for cooling and heating at 20K/min under the cooling rates of 5, 10, 40 and 60K/min in figure 2 to obtain heat tolerance delta Cp, carrying out area integration on the heat tolerance in figure 3 to obtain the standard glass state enthalpy difference of different glass states and 20K/min in figure 4, wherein five glass state heat capacities on the right side in figure 3 are equal, the integrated glass state enthalpy difference is a platform area on the right side in figure 4, each glass state enthalpy difference is not increased any more, and the glass state structure temperature is obtained under the cooling rate of 5, 10, 40 and 60K/min through a formula.

In the formula (I), the compound is shown in the specification,obtaining a standard structure temperature corresponding to the glass state at a standard cooling rate of 20K/min;

delta H is the enthalpy difference between the glass states obtained at a certain cooling rate and the standard cooling rate of 20K/min;

△C_p-the heat capacity difference between the glassy states obtained at a certain cooling rate and the standard cooling rate of 20K/min;

(8) obtaining structural temperatures corresponding to glass states by using different cooling rates, establishing association with the cooling rates, as shown in fig. 5, wherein the abscissa is the reciprocal of the structural temperature, the ordinate is the cooling rate, the slope of the association diagram is a constant multiple of the activation energy h of the glass state substance, the structural temperatures of five glass states are obtained through the steps 6 and 7, and the activation energy values of the five glass states are calculated by the following formula:

q＝q₀exp(-h/RT_f)

wherein R is a gas constant;

q₀-a constant;

q-cooling rate;

(9) the brittle factor of the substance is related to the glass transition activation energy h, and the brittle factor m of the substance can be obtained through the glass transition activation energy obtained in the step 8 and the structure temperatures of the five glassy states obtained in the steps 6 and 7:

h＝ln(10)RT_fm

wherein R is a gas constant.

The core innovation point of the application is to provide a glass-transition brittleness factor analysis method based on calorimetric test, the method aims to highlight that a differential calorimetric scanner of a thermodynamic instrument is utilized to carry out calorimetric test on an amorphous forming material, the temperature reduction and the temperature rise of the same material, the same sample, the same temperature range and the same temperature rise rate are designed to be a standard curve by taking 20K/min as a standard curve, the temperature reduction rates of 5K/min, 10K/min, 40K/min and 60K/min are respectively selected from the upper part and the lower part of 20K/min to obtain different glass states, the structural temperatures and enthalpy values of the different glass states of the same material are obtained by constructing enthalpy difference, and finally the glass-transition brittleness factor of the material is obtained by calculation, so that the speed of the.