Chapter 437

[Let r be the minimum mean radius of ultrafine powder, o be the surface tension of the molten metal, £ o be the dielectric constant under vacuum, μ be the coefficient related to the field strength, G be the amount of droplets formed per unit time, U be the DC high voltage, and I be the field-induced emission current. The formula relationship between the average radius of ultrafine powder and the relevant parameters such as DC high voltage is as follows: r=6ε0Gσ/√ε0μIU+2σ(3ε0GI/μU).]

[Let the resistance along the flow of the melt in the capillary be P, λ is the resistance coefficient along the flow, d is the diameter of the pipe, is the average flow velocity, and P is the density of the melt.] Laminar flow occurs when viscous liquids flow in capillaries. Let the flow of the alloy melt in the capillary be a stable laminar flow, and according to the Dar c y formula, the resistance P1 along the flow of the alloy melt in the capillary is: P1=λl/dpv^2/2, then ......]

............

Cheng Nuo listed the relationship between the experimental independent variables and the particle size of the obtained ultra-nano powder on the paper.

With the listing of formulas one by one, Cheng Nuo's thinking became clearer and clearer.

"Under the condition that the size of the DC high voltage remains the same, the size of the nano ultrafine powder should be nonlinearly attenuated with the increase of the droplet emission frequency, but when the droplet emission frequency increases to 57 Hz, the size increases slowly in a linear relationship. ”

"However, the pressure at which the melt is transported is different, and when the pressure at which the alloy melt flows in the capillary increases, the additional pressure generated on the surface when the melt forms a liquid cone at the front end of the quartz glass capillary also increases, and the relationship between the two is in accordance with the C curvature formula. So, then ......"

While talking to himself, Cheng Nuo's eyes became brighter and brighter.

Looking down at the experimental data record sheet in his hand, the corners of Cheng Nuo's mouth hooked slightly.

"I think I already know what the problem is. Cheng Nuo said silently in his heart.

On the other side, the older professor saw that Cheng Nuo had not moved for a long time, so he no longer paid attention to Cheng Nuo's side.

Even if Cheng Nuo really had the strength to help the two of them solve the current predicament, he didn't think that Cheng Nuo could do it in an hour.

Now that there is time to calm down, the older professor gradually feels that what he just said is indeed a bit excessive.

How to say, Cheng Nuo is also a talented young man, and it is common to be competitive. As seniors, the two of them really shouldn't be aggressive to this point.

Fortunately, I didn't say what to do if Cheng Nuo failed, otherwise it would be impossible for him to do it, and it would not be impossible not to do it, and he would be in a dilemma.

That's just right. As soon as the time passed, he went up to offer kind condolences, and then tactfully told him that it was difficult to take on this big responsibility, and let the director come over with another person, trying not to hurt Cheng Nuo's face.

It has been planned in my mind, and a picture has already appeared in my mind.

The older professor was just about to pour himself a cup of tea to moisten his throat when he saw that the teapot on the table was empty, and he was about to get up and make another pot.

As soon as he got up halfway, he turned his head and saw a very sudden figure on his side, so he was so frightened that he sat directly on the chair, and the teapot fell to the ground with a clatter.

"Cheng Nuo, when did you come over, why didn't you make any sound at all?"

"It's been a while, Professor, and I just saw that you were in a daze, and I didn't know what you were thinking, so I couldn't bear to disturb you. ”

The older professor coughed lightly, blushing slightly.

Of course, he couldn't tell Cheng Nuo, what he fantasized about was how to "teach" Cheng Nuo as an elder in the future.

Avoiding this topic, the older professor picked up the teapot on the ground and asked, "Didn't Mr. Cheng Nuo check the experimental data over there, and came to me so quickly, did he already find the problem?"

The older professor's tone was full of smiles.

Less than forty minutes had passed, and he didn't think that Cheng Nuo had discovered the problems in the experiment.

You must know that although he and the younger professor are both physicists, mathematics and physics are not separated, and the physics level of the two can reach such a high level, and the mathematical level will not be too bad. At least that's not bad for Ph.D. students majoring in mathematics at top universities.

But even so, the two of them pondered this question for three or four days, but they didn't figure out any clue.

As for Cheng Nuo, it took forty minutes to figure it out......

He didn't think he was that bad.

The older professor guessed that Cheng Nuo saw that time was running out and there was no hope of winning, so he came to understate the matter.

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

Anyway, listening to Mr. Clay, Cheng Nuo is going to stay in the institute for a while. In the future, if you look up and don't see what you look down, there is no need to deliberately make enemies.

However, all this is just speculation on the part of the older professor himself.

Under the slightly dull gaze of the older professor, Cheng Nuo nodded slowly, pushed the scratch paper in front of the older professor, and grinned, "That's right, the reason for the failure of your experiment has been found by me." ”

Seeing that the older professor did not react, Cheng Nuo continued to explain, "I have derived all the independent variables that affect the particle size of nano ultrafine powder by formula, and finally obtained eight calculation relations, as well as their respective application ranges. ”

"Then I checked the data you gave me with the experiment records and found the problem. ”

Cheng Nuo pressed his fingers on the words circled in circles on the scratch paper.

"Vacuum?" the older professor finally reacted.

Cheng Nuo nodded, "That's right, 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 melting droplets into nano ultrafine powder is almost negligible, the vacuum degree can indirectly affect the nozzle pressure and dielectric constant of the capillary in the vacuum chamber,...... and so on seven or eight variables. ”

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

"We really didn't notice that. The older professor pondered for a moment and pondered Cheng Nuo's words carefully, "In other words, the reason why we failed before was because we ignored the influencing factor of vacuum. ”

"So to speak. ”

"Now that you've figured out what's wrong, you must have found a solution, right?"

"After my calculations, as long as the vacuum degree in the vacuum chamber is adjusted to the range of 1.3mPa~1.5mPa, nano ultrafine powder that meets the specifications can be produced. ”

"Is that really the case?" the older professor had already begun to believe Cheng Nuo's words.

"Yes or no, don't you know after experimenting?" Cheng Nuo smiled lightly.

The older professor nodded approvingly.

Let the young professor go to the next laboratory to borrow a vacuum pump, adjust the vacuum level in the vacuum chamber to 1.3mPa, and enter the rest of the values according to the normal value.

As the electric spark shines brightly, the alloy melt is broken down into fine particles.

After some busy observation under the electron microscope, the average particle size was finally 84, which fully met the standard of nano ultrafine powder.