Chapter 113: Why are we all problems in front of Director Gao? (3k)
Gao Zhendong did not expect the arrival of comrades from the Carbon Research Institute. As far as he knew in his previous life, the first generation SRM rocket throat lining material of the Carbon Research Institute was developed in the early 1960s. There should be some results now. The Research Institute can just ask the Northeast Carbon Research Institute directly for the results.
The first generation SRM rocket throat liner is a copy of the C-17δ graphite from Northern Da Maozi. It has average performance, but it is usable and was successfully applied to the launch vehicle of the first domestic satellite.
But I didn’t expect them to come over. It is said that the Carbon Research Institute is much more professional than me in this regard.
But forget it, let’s make peace with it now that it’s here, and it’s also good to have some exchanges.
After a few words, the exchange between the two parties got down to business.
Zeng Gong’s classmate’s surname is Duan, and he is also the leader of this trip, so the communication is mainly between him and Gao Zhendong.
"Director Gao, I heard Lao Zeng say that last time when you were communicating with them about the missile nozzle, you mentioned silicon infiltration of polycrystalline graphite?"
Gao Zhendong said: " Is there such a thing? Are you doing polycrystalline graphite siliconization? ”
“Yes, Director Gao, we are indeed doing polycrystalline graphite siliconization. We want to strengthen the graphite, but the effect is not satisfactory. As expected.”
Gao Zhendong thought for a while and didn't know what to say. These units, including himself, were full of secrets, so he could only try to ask: "Duan Gong, is it convenient to speak?"
This time Duan I came here prepared. I had already drawn red lines on the unit, and the object of imitation was C-17δ, which is someone else’s product, so I can say quite a lot.
"It's nothing inconvenient. We're here to ask for help. If we don't say this or that, it will be difficult for you, Director Gao."
Duan Gong took out a After reading the information, I turned to a picture. This is an enlarged image of the graphite surface, and there are some data tables next to it.
"Director Gao, look, this is our material test record after siliconization. The thermal cracking phenomenon is serious and the strength is not good."
Gao Zhendong carefully observed Duan Gong's pictures and data records. To be honest, he didn't know much about this stuff, but he was bored in his previous life and read a lot of papers in order to compete with others on the forum.
In order to compete with others, he even spent his own money to buy the papers he needed on various knowledge websites. So boredom is a terrible thing. It will damage your spirit and impact your wallet.
Gao Zhendong looked at Duan Gong's information, held his chin with his hand, and said nothing for a long time. This made people at the Carbon Research Institute think that he was thinking, analyzing, and summarizing, but in fact he was just thinking about it.
After a while, Gao Zhendong asked: "Duan Gong, could you please tell me about your siliconizing method?"
Gao Zhendong has seen some methods of siliconizing polycrystalline graphite. Liquid phase silicon infiltration method, in-situ reaction method, dip coating method, chemical vapor deposition method, hot press sintering method, reactive infiltration method, etc. He must first know what method they use for the section work.
Duan Gong did not hide anything and explained the silicon infiltration method used by his unit.
After listening carefully, Gao Zhendong felt that it was a bit like the in-situ reaction method, except that it might be in the Carbon Research Institute, and it is not called this name now.
He did not dwell on the name and asked: "Is alumina added to the carburizing material?"
When Duan Gong heard this sentence, he was overjoyed to be able to ask this sentence. , proving that Director Gao really understands graphite siliconization. He nodded: "Yes, it has been added. As a sintering aid, the addition of alumina can refine the silicon carbide grains and make the silicon carbide layer denser."
Gao Zhendong was noncommittal and asked: "What is the size of the carbon particles?"
"0.xx mm, high density."
Gao Zhendong said: "Have you considered that small particle size and high density carbon raw materials can increase density and strength?"
Dian Gongdian Head: "Director Gao is right, that's how he considered it."
After asking a few more questions, Gao Zhendong organized the papers he had read in his head and said with a smile: "Duan Gong, I have a few suggestions that you can consider appropriately."
Duan Gong was overjoyed. He actually had several more suggestions. This trip was not in vain: "Director Gao, you say it."
"The siliconization method you used is indeed not the most suitable method for this situation. If you use this method, the siliconized graphite silicon carbide layer has a large number of pores, the SiC particles are loosely packed, and the strength is naturally not particularly good."
< br>"At the same time, with your method, after the silicon carbide concentration in the liquid silicon reaches saturation, it will grow rapidly and eventually form a thicker silicon carbide layer on the surface of the graphite matrix."
Why Gao Zhendong So sure? Because he had seen the SEM (scanning electron microscope) and XRD (X-ray diffraction) results of products produced using this method in his previous paper. Both technologies can observe the microstructure of the sample. There is no doubt that the current Carbon Research Institute , there is no such condition.
Hearing that Gao Zhendong found the problem, Duan Gong was happy at first, and then worried. Just finding the problem is not enough without any method: "Director Gao, what method is good?" Gao Zhendong said : "My suggestion is to use liquid phase silicon infiltration. In my opinion, this method is the same as the method you are using now. It has the advantages of simple operation, low equipment cost, and is suitable for mass production. Compared with other methods, , this method can also retain the graphite matrix to a large extent, which is beneficial to maintaining the self-lubricating and thermal conductivity properties of graphite.”
“But compared with the method you are using now, the biggest difference is that the silicon carbide of siliconized graphite mainly exists in the gaps of the graphite, instead of having a thicker silicon carbide layer on the surface of siliconized graphite like the method you are using. This thicker silicon carbide layer should be the culprit of the serious thermal cracking situation.”
Gao Zhendong also has basis for this statement. In the public paper on domestic SRM materials, imitation C was mentioned. In the -17δ process, the biggest problem to be solved is the thermal cracking problem caused by the excessive thickness of the siliconized layer, but it is not said what method is used.
In Gao Zhendong's view, different paths lead to the same goal, and the plan he proposed should also be able to solve this problem.
When Duan Gong heard that there was a new craft method, he quickly asked: "Director Gao, what do you mean? How is this liquid phase siliconization method performed? "
Gao Zhendong is not secretive at all: "The ratio of silicon carbide and silicon is 3:2 as the silicon source raw material, the reaction temperature is 1600°C, and it is in a vacuum environment. The reaction takes 0.5 hours. Look, isn’t it very simple? ”
As soon as these words came out, Duan Gong almost threw a stick at him. Yes, yes, you are right, it is very simple.
But think about it, this method is really simple. I can’t even think of anything simpler than this. If it works, that would be great. The cost is really low. .
Gao Zhendong did not give Duan Gong a chance to throw his pen at him, and continued: "In this way, we can solve your second problem, the use of alumina."
"Alumina? ”
“Yes, although aluminum oxide can theoretically refine SiC grains and make the silicon carbide layer denser, in fact, when the aluminum oxide is excessive, the reaction will produce a large amount of gas, and when these gases escape , will destroy the compactness of the silicon carbide layer and adversely affect the performance of the siliconized graphite, which will also reduce the performance of your finished product.”
Now the people at the Carbon Research Institute understood that Director Gao was a real master. The other technical staff at the Carbon Research Institute had little stars in their eyes as they watched the two bosses communicating with each other and their writing skills were flying.
What Gao Zhendong said next made the people at the Carbon Research Institute a little embarrassed: "Next, let me talk about the third question."
Ah, do we have so many problems with our technology? ? There are problems everywhere, and this is the third one. I’m so ashamed.
Duan Gong looked ashamed: "Director Gao, please continue."
Gao Zhendong pointed to the carbon particle parameters on the record and said: "I suggest you increase the diameter of the carbon particles. , mentioned 1.x mm, at the same time, do not use compact high-density carbon particles, use looser ones.”
A bunch of technicians from the Carbon Research Institute had doubts in their minds, but they didn't dare to speak, so Duan Gong asked: "Isn't this reducing the density and strength?"
Gao Zhendong shook his head: "No. , you have to consider that the liquid phase siliconization method generates silicified graphite inside the graphite. These loose gaps are exactly the best place for silicon carbide to stay, which is conducive to the uniform distribution of silicified graphite in the product, and the graphite particle size The decrease will weaken the overall strength of the product, increase wear, and increase the wear rate."
It goes without saying that the people at the Carbon Research Institute were excited after hearing Gao Zhendong's words.
Every suggestion made by Director Gao sounds reasonable and goes straight to the point, and the solution is also very clear. This solution even reduces the difficulty and cost.
Although there have been no tests yet, it cannot be said that what Director Gao said is correct, but at least in the eyes of the people at the Carbon Research Institute, the chance is very high.
There is a way to go, but it is much more comfortable than groping in the dark.
After recording Gao Zhendong’s words one by one, Duan Gong said embarrassedly: "Director Gao, let me ask another presumptuous question. Last time you seemed to have mentioned graphite infiltrated with copper?"
Gao Zhendong smiled. He knew why Duan Gong was embarrassed. He felt that they had taken away all Gao Zhendong's achievements here.
Actually, Gao Zhendong doesn't care about this. He has a lot of things in his head and in the lottery. If he wants to realize them one by one, I'm afraid it will take the foolish old man to move mountains. It's better to take them out and let the capable and capable people do it. Get it out.
He nodded: "Yes, that's right, I've said this. Graphite and copper infiltration can not only be used alone, but can also be used in combination with silicon infiltration. Silicon infiltration improves strength, and copper infiltration improves heat resistance. With your current material, you can infiltrate silicon first and then copper to further improve the ablation resistance.”
In the future, someone has done research and found that using the first imitation SRM material mentioned above, infiltrating silicon and then infiltrating copper can reduce the ablation rate of this material by about 30%. The effect is very obvious, although it is still not enough. The performance of the second- and third-generation domestic graphite throat linings is already a big surprise for now.
Hearing this, Duan Gong was greatly surprised and asked cautiously: "Director Gao, can you."
Regarding the relevant statements about the graphite silicon infiltration and copper infiltration process of the Carbon Research Institute, they are all the same. I'm talking nonsense.
Today Chapter 2
(End of this chapter)