A method for preparing samples for PPMS specific heat measurement

Abstract

The present invention discloses a method for preparing samples for PPMS specific heat measurement, which can improve the efficiency of sample preparation for PPMS specific heat measurement and shorten the experiment time. The method of the present invention rolls copper used for increasing the thermal conductivity of the sample and improving the heat transfer efficiency into concentric copper strips of non-equal diameter and puts them into a copper cup for holding the sample. Compared with the existing method for preparing samples for PPMS specific heat measurement, the method of the present invention is more convenient and efficient in the sample preparation process, can simplify the preparation process, and the specific heat test result of PPMS is consistent with the prior art, and does not affect the accuracy of the experiment.

Description

Technical Field

[0001] The invention belongs to an improved design of a specific heat measurement method in calorimetry, and specifically is a method for preparing a sample for PPMS specific heat measurement, which simplifies the PPMS sample preparation process and improves experimental efficiency. Background Art

[0002] Heat capacity is one of the thermodynamic properties of matter. The definition of heat capacity of any system is the ratio of the heat added to the system to the temperature change caused by the system in any process. The heat capacity data obtained from the experiment are mathematically processed to obtain various standard thermodynamic functions of the substance at different temperatures, such as enthalpy change, entropy change and Gibbs free energy change. The measurement of heat capacity can also obtain microscopic information such as the structure of the substance, the mechanism of phase change and the purity of the substance.

[0003] PPMS is a calorimetric instrument that measures the specific heat of samples based on the relaxation method. It has the advantages of high measurement accuracy and high measurement automation. However, the sample preparation process required for PPMS to measure specific heat is relatively complicated. In order to improve the thermal conductivity of the sample, a certain amount of copper needs to be added to the sample. Therefore, to obtain accurate specific heat data, accurately weighing the sample mass and the mass of copper is a prerequisite for correct experimental results. In order to evenly enhance the overall thermal conductivity, the existing sample preparation technology generally cuts copper into copper chips and mixes them into the sample. This means that during multiple weighing processes, once the copper cup containing the sample and copper chips is tipped over, it will cause the loss of small copper chips and affect the final experimental results. In order to avoid large errors in the results, the sample needs to be re-prepared. Summary of the invention

[0004] Based on the problems existing in the current sample preparation process, the sample preparation method of the present invention is proposed. The rolled copper strip is used, and there will be no copper loss in the sample preparation, which reduces the risk of repeated sampling and improves the experimental efficiency. Compared with the existing PPMS specific heat measurement sample preparation method, the method of the present invention is more convenient and efficient in the sample preparation process, can simplify the preparation process, and the PPMS specific heat test results are consistent with the prior art, and do not affect the accuracy of the experiment.

[0005] The technical solution of the present invention is: a method for preparing a sample for PPMS specific heat measurement, characterized in that it comprises:

[0006] Preferably, the purity of the copper strip is not less than 99.99%.

[0007] Preferably, the length of the copper strip is 2.7-3 mm, the width is 0.7-1 mm, the weight of the copper strip is 2.5-5 m, and the pitch is 1 / 5-1 / 10 of the height of the copper cup.

[0008] The copper strip is rolled into non-uniform diameter, with the maximum diameter not greater than the diameter of the copper cup used for sample loading, preferably 2-3 mm, and the height being 4 / 5-6 / 5 of the height inside the copper cup.

[0009] The method of the present invention rolls the copper used to increase the thermal conductivity of the sample and improve the heat transfer efficiency into concentric copper strips of non-uniform diameter and puts them into a copper cup containing the sample. Compared with the existing PPMS specific heat measurement sample preparation method, the method of the present invention can improve the efficiency of PPMS specific heat measurement sample preparation, shorten the experiment time, and is more convenient and efficient in the sample preparation process, and can simplify the preparation process. The PPMS specific heat test result is consistent with the existing technology and does not affect the accuracy of the experiment.

[0010] The present invention has the following beneficial effects:

[0011] (1) There is no need to cut copper into small copper scraps, which saves experimental time and improves experimental efficiency;

[0012] (2) The copper strips are rolled into non-uniform diameters, with the widest circle attached to the bottom of the copper cup, which can enhance the stability of the copper cup and reduce the risk of the copper cup tipping over due to instability during the experiment;

[0013] (3) Copper bars with different diameters are rolled to reduce the overlap of the copper bars in the vertical area during sheeting, so that the copper bars can have more complete contact with the sample, which is beneficial to heat transfer.

[0014] (4) The rolled copper strip can be weighed together with the prepared copper cup. Compared with the prior art method of first weighing the copper cup and then weighing the total mass of the copper cup and copper chips, the one-step method directly measures the total mass of copper, which can reduce the experimental steps and weighing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of sample preparation according to the present invention.

[0016] Figure 2 Copper filings and copper strips were used for the present invention to measure and certify benzoic acid values.

[0017] Figure 3 The deviation of the measured values ​​of benzoic acid from the standard values ​​was determined for the present invention using copper filings and copper strips.

[0018] Figure 4 For the present invention, copper chips and copper strip α-Al2O3 measured values ​​and standard values ​​were used.

[0019] Figure 5 For the present invention, the deviations of the measured values ​​of α-Al2O3 from the standard values ​​were used for copper chips and copper strips. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0021] Example

[0022] 1. Select the American NIST standard benzoic acid for specific heat measurement:

[0023] 1. Use 99.999% pure copper from Alfa Aesar to make a copper cup for sample storage, with a bottom diameter of 3 mm.

[0024] 2. Use Alfa Aesar's 99.999% pure copper to cut a 2.8mm long and 0.7mm wide copper strip.

[0025] 3. Roll the copper strip into a non-uniform diameter spiral (conical spiral), with the widest section having a diameter of 3 mm and the thinnest section having a diameter of 0.2 mm. The pitch is 1 / 7 of the height of the copper cup and the height is 9 / 10 of the height inside the copper cup.

[0026] 4. Place the rolled copper strip with the wide end facing down into the bottom of the copper cup.

[0027] 5. Weigh the total weight of the copper cup and copper bar, weigh them 6 times, and take the average value as the mass of the copper.

[0028] 6. Pour the powder or fine particle sample into a copper cup and press it into a tablet to make a sample block for PPMS specific heat measurement.

[0029] 7. Weigh the total weight of the sample (such as benzoic acid) and copper, weigh 6 times, and take the average value as the total weight of the sample and copper.

[0030] 8. Place the prepared sample into the PPMS sample holder, start measuring, and perform relevant data processing to obtain the specific heat value of benzoic acid.

[0031] 2. Select the American NIST standard sample α-Al2O3 for specific heat measurement:

[0032] 1. Use 99.999% pure copper from Alfa Aesar to make a copper cup for sample storage, with a bottom that is a circle with a diameter of 3 mm.

[0033] 2. Use Alfa Aesar's 99.999% pure copper to cut a 3mm long and 1mm wide copper strip.

[0034] 3. Roll the copper strip into a non-uniform diameter spiral (conical spiral), with the widest section having a diameter of 3 mm and the thinnest section having a diameter of 0.1 mm. The pitch is 1 / 8 of the height of the copper cup and the height is 9 / 10 of the height inside the copper cup.

[0035] 4. Place the rolled copper strip with the wide end facing down into the bottom of the copper cup.

[0036] 5. Weigh the total weight of the copper cup and copper bar, weigh them 6 times, and take the average value as the mass of the copper.

[0037] 6. Pour the powder or fine particle sample into a copper cup and press it into a tablet to make a sample block for PPMS specific heat measurement.

[0038] 7. Weigh the total weight of the sample and copper, weigh 6 times, and take the average value as the total weight of the sample and copper.

[0039] 8. Place the prepared sample into the PPMS sample holder, start measuring, and perform relevant data processing to obtain the specific heat value of α-Al2O3.

Claims

1. A method for preparing samples for PPMS specific heat measurement, characterized in that: A conical spiral copper strip coil made of copper strips is placed in a copper cup for holding the sample to be measured, and then the PPMS specific heat of the sample is measured; The specific process is: 1) Wind the copper strip into a conical spiral line one circle at a time, and gradually reduce the spiral diameter from bottom to top to form a spiral line with the same axis and unequal diameter. 2) Place the rolled copper strip with the wide end facing downward into the bottom of the copper cup, so that the widest circle of the spiral is attached to the bottom of the copper cup; 3) Pour the sample into a copper cup and press it into a sample block for PPMS specific heat measurement; 4) Place the prepared sample into the PPMS sample holder and start measuring to obtain the specific heat value of the sample.

2. The method according to claim 1, characterized in that The purity of the copper strip is not less than 99.99%.

3. The method according to claim 2, characterized in that The length of the copper strip is 2.7-3 mm, the width is 0.7-1 mm, the weight of the copper strip is 2.5-5 mg, and the pitch is 1 / 5-1 / 10 of the height of the copper cup.

4. The method according to claim 1, characterized in that When the bottom diameter of the copper cup is a circle of 3 mm, the copper strip is rolled into a non-uniform diameter roll, the maximum bottom diameter is not greater than the diameter of the copper cup used for sample loading, and the height is 4 / 5-6 / 5 of the height of the copper cup.

5. The method according to claim 4, characterized in that The maximum diameter of the bottom of the copper strip coil is 2-3 mm.

Images