Chapter 434

Let R be the minimum average radius of ultrafine powder, o be the surface tension of molten metal, o be the dielectric constant in vacuum, μ be the coefficient related to field strength, G be the droplet amount formed in unit time, u be the DC high voltage, I be the field emission current. The relationship between the average radius of superfine powder and the parameters such as DC high voltage is: r = 6 ε 0g σ√ ε 0 μ IU + 2 σ (3 ε 0gi μ U)]

[let the resistance along the capillary tube be p, λ be the resistance coefficient, D be the pipe diameter, l be the capillary length of the melt flowing through, v be the average flow velocity, p be the density of the melt. Laminar flow often occurs when viscous liquid flows in capillary. Let the flow of alloy melt in capillary tube be stable laminar flow. According to Darcy formula, the resistance along the way of alloy melt flowing in capillary is P1 = λ ldpv ^ 22, then 】

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Cheng Nuo listed the relationship between the experimental independent variables and the particle size of the ultrafine powders.

With the listing of a formula, Cheng Nuo's ideas become more and more clear.

"When the DC voltage remains constant, the size of nano ultrafine powder should be nonlinear attenuation with the increase of droplet emission frequency, but when the droplet emission frequency increases to 57 Hz, the size increases linearly and slowly."

"But the pressure of conveying melt is different. When the pressure of alloy melt flowing in the capillary increases, the additional pressure generated on the surface will also increase when the melt forms a liquid cone at the front end of the quartz glass capillary. The relationship between the two conforms to the formula of C curvature. In this way, then... "

While talking to himself, Cheng Nuo's eyes become more and more bright.

Looking down at the experimental data record table at hand, Cheng Nuo's mouth slightly tick.

"I think I already know what the problem is." Cheng Nuo said in silence.

On the other hand, seeing that Cheng Nuo has not moved for a long time, the elder Professor no longer pays attention to Cheng Nuo.

Even if Cheng Nuo really has the strength to help them solve the current dilemma, he does not think Cheng Nuo can do it in an hour.

Now that I have time to calm down, the elder Professor gradually feels that his words are indeed a little extreme.

How to say, Cheng Nuo is also a gifted young man. It is common for him to be competitive. As forerunners, they should not be aggressive.

Fortunately, I didn't say what to do if Cheng Nuo failed. Otherwise, he was in a dilemma.

This is just right. When time goes by, I will go up to comfort him, and then gently tell him that it is difficult for him to be such a big responsibility, so that the director can change his face and try not to hurt Cheng Nuo's face.

The mind has been so well planned, the picture has come to mind.

As soon as the elder professor was about to pour himself a cup of tea to moisten his throat, he saw that the teapot on the table was empty, and he was ready to get up and make another pot.

Just half up, a turn around, see the body side is very abrupt appearance of the figure, was scared to directly sit on the chair, the teapot also clang to fall on the ground.

"Cheng Nuo, when did you come here? Why didn't you have a sound?"

"I've been here for a while, professor. I just saw that you were in a trance. I didn't have the heart to disturb you."

The old professor coughed and blushed slightly.

Of course, he can't tell Cheng Nuo. What he fantasizes about is how to "teach" Cheng Nuo in a senior posture later.

Avoiding this topic, the old professor picked up the teapot on the ground and asked, "isn't Mr. Cheng Nuo checking the experimental data over there? Has he found out the problem by coming to me so quickly?"

The old professor's tone was full of laughter.

Less than 40 minutes later, he didn't think Cheng Nuo had discovered the problems in the experiment.

You know, although he and the younger professor are both physicists, they are not separated from each other in mathematics. If they can achieve such high attainments in physics, their mathematical level will not be too bad. At least compared with the doctoral students majoring in Mathematics in the top universities, it is absolutely true.

But even so, this question two people pondered for three or four days, Leng did not think out any clue.

As for Cheng Nuo, it took 40 minutes to figure out

He didn't think he was that bad.

The elder Professor guessed that Cheng Nuo probably saw the end of time and had no hope of winning, so he came here to make a light of it.

If that's the case, I don't mind selling Cheng Nuo a face, when it never happened.

Anyway, according to Mr. clay, Cheng Nuo will probably stay in the Research Institute for some time. Later, if you don't see what you see when you look down, you don't have to be vicious.

However, all this is only the elder professor's own guess.

Under the old professor's slightly dull sight, Cheng Nuo nodded slowly, pushed the manuscript paper to the elder professor and grinned, "yes, I have found out the reason why you failed the experiment."Seeing that the elder professor did not respond, Cheng Nuo continued to explain, "I have derived all the independent variables that affect the particle size of nano ultrafine powder by formula derivation, and finally obtained eight calculation formulas, as well as their respective application scope."

"Then I compared the data you gave me and found the problem."

Cheng Nuo pressed his finger on the words that were circled on the rough paper.

"Vacuum?" At last the old professor responded.

Cheng Nuo nodded, "yes, it's vacuum. After calculation, I found that although the direct effect of the vacuum degree in the vacuum chamber on the process of alloy melt dripping into nano ultrafine powder can be almost ignored, but the vacuum degree can indirectly affect the nozzle pressure and dielectric constant of the capillary in the vacuum chamber Wait for seven or eight variables. "

Vacuum degree, simply put, is the degree of rarefaction of a gas in a vacuum state.

"We really didn't notice that." The senior professor pondered over Cheng Nuo's words, "that is to say, the reason why we failed before is because we neglected the influence factor of vacuum."

"So to speak."

"Now that you have found the problem, you must have found the right solution?"

"According to my calculation, as long as the vacuum in the vacuum chamber is adjusted to 1.3 MPa ~ 1.5 MPa, nanometer ultra-fine powder can be prepared according to the specification."

"Really?" The elder professor has already begun to believe Cheng Nuo's words.

"Yes or no, don't you know by experiment?" Cheng Nuo said with a gentle smile.

The old professor nodded his head.

Ask the young professor to borrow a vacuum pump from the next laboratory. After adjusting the vacuum degree in the vacuum chamber to 1.3 MPa, the remaining values are input according to the normal values.

With the sparkle of electric spark, the molten alloy is decomposed into fine particles.

The average particle size is 84, which is in line with the standard of nano ultrafine powder.

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