The heating equipment often used in laboratories includes common heating equipment such as muffle furnace, high temperature furnace, tube furnace, etc. Most of the research on metal, ceramics, polymer and other raw materials must be vacuumed to carry out experiments, and the tube furnace is vacuumed. Performance indicators are stronger. However, the operating procedures of most laboratory staff are not necessarily reasonable, which may cause the internal vacuum value of the tube furnace to be low, and excessive residual air, etc., which may reduce the accuracy of the experiment and fail to reach the test. Standard conditions.
In response to this kind of phenomenon, Zhengzhou Nuotai technical staff summarized the vacuum phenomenon of tube furnace, and listed the key issues and reasonable practical operation methods.
In order to improve the accuracy of vacuuming, we first summarize the meaning and function of vacuuming the tube furnace. First of all, the meaning of vacuuming is to reduce the air inside the tube furnace, so that the test raw materials are in an oxygen-free environment, and then the test raw materials Redox reactions.
Why is the vacuum value low? Why is the experiment not up to the ideal situation?
The low vacuum value has the following phenomena:
First, the vacuum pump is aging, and the original vacuum value is low;
Second, the vacuum pipeline is aging, the pipeline is leaking, and the interface is leaking;
The sealing ring of the third tube furnace is aging and the assembly method is wrong.
The solution is as follows. Firstly, replace the aging pipeline and sealing ring, and check whether the interface part is leaking. In particular, many manufacturers use the quick-connect air pipe interface to fail to meet the vacuum requirements, and there is hidden air leakage, which is not easy to check. Secondly, apply vacuum silicone grease to the sealing ring to improve the sealing performance of the sealing ring part, and focus on checking the sealing effect of the sealing ring assembled at the flange part.
Tube furnace vacuum pumps have poor vacuum performance indicators, and can be replaced with higher precision vacuum pumps to carry out experiments. Commonly used vacuum pumps for tube furnaces range from 1,000 to 3,000, and molecular pumps cost tens of thousands.
However, in order to save costs, we are based on the meaning of vacuuming to exclude oxygen. We can fill the tube furnace with inert gases such as nitrogen and argon to reduce the oxygen concentration so that the experimental raw materials are not prone to oxidation and reduction. The operation process is as follows;
First, we connect the tube furnace to the vacuum pump and nitrogen cylinder, then close all valves, turn on the vacuum pump and vacuum valve, observe the pressure gauge and wait until the vacuum value of the vacuum pump is stable, then close the vacuum valve and vacuum pump; then turn on the gas cylinder to start the air intake After the pressure gauge returns to normal pressure, close the intake valve. At this time, the air concentration in the tube furnace decreases, but the air still remains. We repeat the steps to obtain higher purity nitrogen and eliminate the air, such as For experiments requiring higher purity, the steps can be repeated multiple times. Pay attention to the sequence of opening and closing the pump valve cylinder.
Some laboratory tube furnaces must be tested in vacuum. The precision of the vacuum pump is very high, but it does not meet the experimental regulations. It may be that the vacuum pump is closed directly after the vacuum is pumped and the vacuum valve is not closed. Because the vacuum pump is not working, air will flow back, which may cause Air enters the tube furnace tube, we only need to close the vacuum valve after vacuuming to completely solve this kind of phenomenon.