GB/T 7962.21-2019Test method of colourless optical glass -- Part 21: Resistance to attack by aqueous alkaline solutions (English PDF)

4.1 General

During the test, unless otherwise specified, chemical reagents should be used.

4.2 Water

It shall meet the requirements of secondary water specified in GB/T 6682-2008.

4.3 Test solution

Dilute the sodium hydroxide solution with water to control and adjust the pH value so that the pH value = 12 +/- 0.1.

4.4 Nitric acid (HNO3)

Dilute with analytical grade to pH 4.5+/-0.1.

4.5 Sodium hydroxide solution

Concentration cNaOH~0.1mol/L.

4.6 Isopropanol (C3H7OH)

There is no residue after distillation.

5.1 Stirrer

The stirrer is made of stainless steel or polytetrafluoroethylene (PTFE). The length of the stirrer rod of the stainless steel stirrer is (350.0+/-2.5) mm and the diameter is

(10.0+/-1.0)mm; polytetrafluoroethylene (PTFE) material agitator stirring rod length (350.0+/-2.5)mm, diameter (15.0+/-1.0)mm; horizontal blade

The vertical height of the section is (15.0+/-1.0)mm and the width is (58.0+/-1.0)mm, as shown in Figure 1.

5.2 Reaction tank

A flat-bottomed cylindrical barrel with a closed lid is made of stainless steel. Its inner diameter is (150.0+/-2.5)mm, and the height is (200.0+/-2.5)mm.

Connect the screw and the barrel with the nut, as shown in Figure 2.The lid is made of a wide neck, and there are two hooks at the bottom for hanging the tested sample; the neck

There is a plug with a hole at the mouth to insert the agitator; the allowable deviation of the size without tolerance should meet the minimum requirements specified in Table 1 of GB/T 1804-2000

Rough v grade. The stopper is made of a suitable inert material and should be boiled in sodium hydroxide solution for about 60 minutes.

5.3 Platinum wire or silver wire

Wrap the tested sample with platinum wire or silver wire with a diameter of less than 0.1mm or make a sample frame to support and hold the tested sample.

5.4 Constant temperature bath

The volume is 30L~40L; the thermostatic control is (50.0+/-0.2) degrees C.

5.5 Analytical balance

Minimum graduation value. 0.1mg.

5.6 Drying dish

Use silane mixture (absorbing water) and soda lime (a mixture of CaO and Na2O, absorbing CO2) as desiccants.

5.7 Fixture

It is made of a material that does not scratch the smooth surface of the tested sample, for example, plastic.

5.8 Vernier calipers

Minimum graduation value. 0.02mm.

5.9 Ultrasonic equipment

The cleaning tank is filled with water and can be heated to 50°C.

5.10 Beaker

The capacity is 100mL~500mL.

5.11 pH meter

Minimum graduation value. 0.05.

6.1 Material requirements

The sample to be tested should have no visible stripes or inclusions. The stress birefringence of the rough glass of the tested sample should meet the requirements of GB/T 903.

The central stress birefringence is less than or equal to 6nm/cm.

6.2 Processing quality and quantity

All surfaces of the tested sample are polished, the size is (30.0+/-0.1)mmx(30.0+/-0.1)mmx(2.00+/-0.05)mm, and the surface roughness reaches

Ra=0.012µm, the surface defects reach B/2x0.63 specified in B.1 of GB/T 1185-2006, and the polished chamfer C0.2.Number of tested samples. 6 pieces.

6.3 Calculation of the total surface area

Before cleaning the sample to be tested, perform all size measurements, take three different test positions, and measure the distance and thickness between the two parallel sides.

Degree, whichever is the average value. The measurement accuracy is 0.02mm, and the calculation accuracy of the actual full surface area is 2%. Record the measured value.

6.4 Cleaning pretreatment

The cleaning pretreatment requirements are as follows.

a) The tested sample should be cleaned as soon as possible after polishing. Place three 100mL beakers in an ultrasonic water bath to heat and keep the water

At (45+/-3) degrees C. Each beaker should keep enough isopropanol to make it immersed in the cleaned test sample. Wash throughout

During the process, the sample under test should be clamped and moved by the fixture. To avoid contamination of its surface, such as fingerprints.

b) Immerse the test sample in the first beaker and clean it with ultrasonic for about 1 min; then use tissue paper and soft cloth soaked in isopropyl alcohol

Gently wipe the tested sample; then immerse the tested sample in the second and third beakers, and clean them for about 1 min.

c) Isopropanol should be replaced every time a test sample is cleaned in the first beaker. The isopropanol in the second and third beakers should be cleaned.

Test samples should be less than 10, if any contamination of isopropanol is found, it should be replaced immediately.

d) Place the cleaned tested sample in the air to dry naturally or at (115+/-5) degrees C for about 30min.

e) Before the test, the tested sample should be placed in a dry dish.

7.1 Routine test

7.1.1 The prepared sample to be tested should be used only once. At least two tested samples should be measured at the same time under the same conditions.

7.1.2 Put the reaction tank with 2L test solution into the constant temperature tank, adjust the stirrer to (15+/-1) mm above the bottom of the reaction tank, and

And keep the temperature at (50.0+/-0.2)°C.

7.1.3 Use a clamp to clamp the clean tested sample out of the drying dish, put it into an analytical balance and weigh it, and record the mass as m1.

7.1.4 Wrap the tested sample with platinum wire or silver wire in a cross shape or put the tested sample into the sample frame, hang it on the stirrer and react.

The middle of the tank wall. The bottom surface of the tested sample is (50+/-1.5) mm from the bottom of the reaction tank, as shown in Figure 2.The allowable deviation of the dimension without tolerance in Figure 2

The difference should comply with the roughest v level specified in Table 1 of GB/T 1804-2000.The sample to be tested should not touch the wall of the reaction vessel.

7.1.5 The stirring speed of the stirrer is (100 +/- 2) r/min, and the reaction time is calculated according to the immersion time of the tested sample.

7.1.6 After the test is completed, take the tested sample out of the reaction tank, and clean the tested sample according to the following steps, without stopping between steps. in

A set of 250mL beakers are each filled with.200mL of water, nitric acid, isopropanol and other liquids, and each test sample is immersed in the following cycle sequence for about 1s.

a) Dip into the beaker filled with water 5 times, and the water temperature is (50+/-0.2) degrees C. Change the water when cleaning the next sample to be tested.

b) Dip in nitric acid once at room temperature.

c) Immerse again in water at room temperature.

d) Immerse in isopropanol 3 times at room temperature.

7.1.7 Clamp the tested sample with a clamp, untie the platinum wire or silver wire or take out the tested sample from the sample frame. Immerse the test sample in isopropanol

It is about 1s, then take it out to dry in the air, and then transfer the clean tested sample to a drying dish to cool to room temperature. Weigh and record immediately

The mass is m2.Calculate the time required for the erosion depth of 0.1µm according to the formula in Chapter 8.Under natural light,

Observe the changes on the surface of the tested sample from a direction close to 45° or under a microscope.

7.2 Unknown test time tested sample test

In order to determine the time required for erosion, the six tested samples prepared as specified in Chapter 6 were initially tested in the order given in Figure 3.

a) Immerse a test sample in the test solution for 1h, and calculate the alkali resistance stability level according to the mass loss or continue to the next step of erosion time (4h or 0.25h).

b) After 1h of erosion, the mass loss of the tested sample is between 1mg/block~4mg/block, and the alkali resistance stability grade can be calculated and judged.

c) After 1h of erosion, if the mass loss of the tested sample is more than 4mg/block, the erosion time of the tested sample is adjusted to 0.25h; if the mass loss of the tested sample is less than 1mg/block, the erosion time is adjusted to 4h.

d) After corrosion for 0.25h or 4h, the mass loss of the tested sample is >1mg/piece, and the alkali resistance stability level can be calculated and determined;

After 0.25h, if the mass loss of the tested sample is less than 1mg/piece, the data after 1h of erosion is directly used to calculate the alkali resistance stability, etc.

Grade; after 4h of erosion, the mass loss of the tested sample is less than 1mg/block, and further erosion is required for 16h.

e) After initially determining the test time according to the above steps, follow 7.3.

7.3 Test of the tested sample with known test time

If the integer level of the alkali resistance stability of the optical glass is known or the corrosion time has been determined according to 7.2, the following steps should be used.

a) Immerse two test samples in the same test solution for a specified time (for example, 0.25h, 1h or 4h, etc.). If it is corroded after 4h,

If the weight loss of the tested sample is less than 1mg/block, it will be further eroded for 16h; if the mass loss of the tested sample is still less than 1mg/block after the erosion, the alkali resistance stability level is calculated and judged.

b) If the mass loss of the tested sample is more than 4mg/piece after 1h of erosion, the erosion time needs to be shortened, as shown in Figure 3.

c) If the mass loss of the tested sample is between 1mg/block~4mg/block after 1h of erosion, calculate the alkali resistance stability grade.

d) Either the mass loss of the tested sample after 1h or 4h is greater than 1mg/piece, or the alkali resistance stability grade is calculated and judged according to the test result of 16h erosion.

9.1 Integer grade of alkali resistance stability

According to the time t0.1 required to corrode the 0.1µm surface layer of the tested sample, the integer grade of the alkali resistance stability of the optical glass is judged according to Table 1.

9.2 Alkali resistance stability

The measurement of level m2 after the decimal point is in Chapter 7, and the calculation is in Chapter 8.

Use the naked eye to qualitatively determine the surface change of the tested sample, and determine the grade after the decimal point of the alkali resistance stability of the optical glass according to Table 2.

10.1 The test report should include the following information.

a) The standard number of this part.

b) Glass density (g/cm3).

c) The surface area of the tested sample (cm2).

d) The time (h) required for the test sample to be eroded to a depth of 0.1µm, calculate and determine the integer level of the alkali resistance stability of the glass; and observe the changes on the surface of the test sample,

Determine the decimal point level of the alkali resistance stability of the tested sample.

e) Determine the alkali resistance stability class AR.

f) Record any abnormal characteristics during the test.

10.2 See Table 3 for the format of the alkali resistance stability test report.