GB/T 38712-2020Test method for thermal conductivity of ultrathin glass—Heat flow method (English PDF)

1 Scope

This Standard specifies the terms and definitions, test device, environmental conditions, sample requirements, test steps, result calculation and expression, instrument calibration, and test reports for measuring the thermal conductivity of ultrathin glass by the heat flow method.

This Standard applies to the test of the thermal conductivity of ultrathin glass.

1.5 W/(m·K); bond and overlay the cleaned glass pieces; the thermal silicon grease between the glass pieces shall be applied evenly;

e) Use a pressure that is not less than 200 N to compact the superimposed samples; then, wipe off the thermal silicone grease that overflows the edge of the sample;

f) Use a Vernier caliper that meets the requirements of GB/T 21389 to measure the thickness of the compacted sample; measure it three times at 120° rotation; take the average value, and record it as d. It is required that the thickness of the thermal silicon grease between the glass laminations is not more than 20% of the thickness d of the sample.

2 Normative references

The following documents are indispensable for the application of this document.

For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 5598, Test method for thermal conductivity of beryllium oxide ceramics

GB/T 21389, Vernier, dial and digital display calipers

GB/T 34171, Test method for flexural property of thin and ultrathin glass - Three-point bending method

3 Terms and definitions

Terms and definitions determined by GB/T 5598, GB/T 34171 and the following ones are applicable to this document.

4 Test device

The test device mainly consists of heating source, cold pole, hot pole, pressurization system, cooling system, thermocouple, as shown in Figure 1; the specific requirements of the test device are as follows:

a) The heater is made of a metal material of a large thermal conductivity (brass is recommended); it adopts an internal heating structure; the temperature is controlled by a digital display temperature-controlled meter, to provide a stable heat source for the hot pole; the temperature deviation is less than 0.2 °C;

b) The cold pole and the hot pole shall be materials of the same diameter and have a thermal conductivity greater than 50 W/(m·K); the diameter shall be preferably 30 mm ~ 40 mm; the surface shall be flat and smooth;

c) The pressurization system is mainly composed of a pressure sensor and a motor, which pressurizes the sample; the pressing force is adjustable at 0 N ~ 1000 N;

d) The cooling system includes a constant temperature water tank and a cooler. The cooler is made of brass, and is equipped with a water tank inside, which is connected to the outer constant temperature water tank through a pipe. Use the water circulation of the external constant temperature water tank and the cooler to provide a stable temperature for the cold pole; the temperature deviation is less than 0.2 °C;

e) The thermocouple shall be a thermocouple whose division value is 0.1.

Place two thermocouples on the cold pole and the hot pole, respectively.

The temperature deviation of the same pole shall not exceed 0.2 °C. The cold end shall be placed in the ice-water mixture (0 °C) for temperature compensation.

b) Use a Vernier caliper that meets the requirements of GB/T 21389 to measure the thickness of the glass pieces; calculate the number of glass pieces whose stack thickness is greater than 2 mm;

c) Wash and dry the small glass pieces; ensure that the surface is clean;

d) Use thermal silicone grease whose thermal conductivity is greater than […]

6 Sample requirements

7 Test steps