Chapter 194 The Difficulties Encountered by Zhang Yan
After eating, Zhou Yimin stayed with Zhang Yan for a while.
Aunt Zhang pulled Zhang Lu and Zhang Yu out of the way and gave space to her daughter and son-in-law. She was very satisfied with her son-in-law.
Zhang Jianshe went out with the box of mangoes.
"I'm going to go out for a moment."
He planned to use this box of mangoes to buy an old hydroelectric generator for Zhou Yimin and send it to Zhoujiazhuang under a legitimate name.
Let Zhoujiazhuang take it over, not Zhou Yimin.
In this way, even if there is an investigation in the future, it will be traced back to Zhoujiazhuang as a whole, and will have little to do with his son-in-law.
"Be careful."
Knowing that her husband was running around for his son-in-law, she did not stop him, but just reminded him to be careful.
Zhou Yimin and his girlfriend were alone in a room, but it was not the scene that everyone imagined. Influenced by his father, Zhang Yan also majored in science and technology in college.
"Have you started studying these?" Zhou Yimin looked at it for a while and couldn't help asking.
Are you a freshman and you've already started doing research?
Zhang Yan's research subject is electric lights.
Some people may say, wasn't the electric light invented a long time ago? What's there to study?
In fact, the electric lamps currently used in our country are not very good. Not only do they have high energy loss, but their service life is also short.
According to Zhou Yimin, the halogen tungsten lamp was only developed in the United States in 1959, which was last year, and it is estimated that it is not yet available in China.
In ordinary incandescent lamps, the high temperature of the filament causes the evaporation of tungsten, and the evaporated tungsten precipitates on the glass shell, causing the glass shell of the bulb to turn black.
The tungsten halogen lamp eliminates this blackening phenomenon by utilizing the principle of tungsten halogen cycle.
Zhang Yan nodded: "Yes! This is our group's research topic this semester. Don't underestimate this light bulb, it actually contains a lot of knowledge points."
"I know." Zhou Yimin said without denying.
Ordinary electric lamps are mainly composed of glass shell, filament, wire, sensor column, lamp holder and so on.
The glass shell is made of heat-resistant glass, which is spherical and isolates the filament from the air. It can transmit light and protect the filament. When the incandescent lamp is working, the temperature of the glass shell can reach up to 100℃.
The filament is made of tungsten wire, which is much thinner than a hair and is made into a spiral shape.
The filament looks very short, but if this extremely thin spiral tungsten wire is pulled into a straight line, the straight line will be more than 1 meter long.
The two conductors appear simple on the surface, but they are actually composed of three parts: the inner conductor, the Dumet wire, and the outer conductor.
The inner wire is used for conducting electricity and fixing the filament, and is made of copper wire or nickel-plated iron wire; the short red metal wire in the middle is called Dumet wire, which is required to be closely combined with the glass without leaking; the outer wire is copper wire, and its task is to connect the lamp holder for power supply.
The trumpet-shaped glass part is the sensor column, which is connected to the glass shell and serves to fix the metal parts.
The lamp holder is a metal part that connects the lamp holder and the power supply, and is bonded to the glass shell with soldering paste.
"Do you want to replace the filament material now to extend the life of the lamp?" Zhou Yimin asked her.
He looked at what Zhang Yan had recorded and roughly guessed what they were going to do.
"Yes! It not only extends the lifespan, have you noticed? The tungsten filament will evaporate and make the glass shell black. If other materials are replaced, will it be different?" Zhang Yan said.
Replacing the filament material was a research consensus of their group.
So far, they have conducted several experiments and replaced more than a dozen materials, but have not achieved the desired effect.
Afraid that Zhou Yimin didn’t understand, Zhang Yan explained it in detail.
It is said that like carbon filaments, tungsten filaments in incandescent lamps are also afraid of air.
If the glass bulb is filled with air, the temperature of the tungsten filament will rise to over 2000℃ after the power is turned on. The air will attack the tungsten filament mercilessly, causing it to burn out quickly. At the same time, a yellow-white tungsten trioxide will be generated, which will adhere to the inner wall of the glass bulb and the internal parts of the lamp.
"In other words, those black substances are actually tungsten trioxide, which is caused by the air." Zhou Yimin said.
Zhang Yan was stunned for a moment, and felt that what her partner said was correct, so she nodded: "That's right!"
"So, what material are you going to change? Just start with the air! Pump out the air inside." Zhou Yimin continued.
Zhou Yimin tilted his head and said, "To be precise, it's the oxygen in the air that's causing the problem. Just get rid of the oxygen."
Just apply a little red phosphorus on the sensor column of the bulb. Red phosphorus will turn into white phosphorus when heated, and white phosphorus can easily react with oxygen to generate solid phosphorus pentoxide, which "eats up" the oxygen. In this way, the residual oxygen in the glass bulb is also eliminated.
Zhang Yan was stunned.
"Yimin, this is how our current electric lights work. But you have to know that there will always be some residual air, or oxygen, inside the bulb." Zhang Yan said with a smile.
To completely evacuate the air inside a light bulb, current domestic technology and techniques cannot reach that level.
"In order to solve this problem, some people abroad have long tried to inject nitrogen into light bulbs," Zhang Yan continued.
If there is a vacuum in the light bulb, then when the tungsten filament is connected to the power source and the temperature rises, the tungsten molecules will become restless and leave the filament in large numbers, running around everywhere as if in an empty space, until they hit the wall of the glass shell and are sucked.
Once the glass bulb is filled with nitrogen, a thin, stable gas protective layer will form around the incandescent filament.
Each nitrogen molecule is a brave warrior, guarding near the tungsten filament. It is ruthless to those tungsten molecules that attempt to break away from the group and run around, and hits them back fiercely, asking them to return to their jobs and continue to serve the light.
This allowed the tungsten filament to evaporate much more slowly, and the nitrogen-filled incandescent bulb was born.
Insulation slows down the evaporation rate of the tungsten filament, allowing the filament to operate at a higher temperature during the same service life, so the luminous efficiency of a gas-filled bulb is higher than that of a vacuum bulb.
"Can we inject some other elements so that the evaporated tungsten can be reattached to the tungsten filament under high temperature conditions?" Zhou Yimin induced the principle of tungsten halogen lamp and asked Zhang Yan to consider that aspect.
The principle of the tungsten halogen lamp is also simple. Under appropriate temperature conditions, the tungsten evaporated from the filament reacts with the halogen substance in the bulb wall area to form a volatile tungsten halogen compound.
Since the bulb wall temperature is high enough, the halogen tungsten compound is in gaseous state. When the halogen tungsten compound diffuses to the hotter area around the filament, it is decomposed into halogen and tungsten. The released tungsten part returns to the filament, while the halogen continues to participate in the cycle process.
Some so-called technologies, once explained, are just that.
"Tungsten filament again?"
This bold idea shocked Zhang Yan.
They really haven't thought about doing this.
Zhang Yan is also a smart person and quickly realized that this was a feasible direction.
"Yes! Yimin, you have an amazing brain."
(End of this chapter)
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