Chapter 11: Glove box

"I'm back."
　　 Chen Wanqing returned from Teacher Wei’s office with a smile on her face and looked in a good mood.
　　 "Senior sister, what is so happy?" Xu Qiu said.
　　"It’s been almost a year since I came here, and this time it is finally about to open. A work I did recently has now established the main framework.
　　 After showing the repaired picture to Teacher Wei, he was quite satisfied and asked me to start writing the article. However, I guess I can only post a small article. "Chen Wanqing said.
　　 "Congratulations, senior sister." Xu Qiu said.
　　 "By the way, I have almost mastered the operation of cleaning the substrate now. Can you teach me some new experimental operations?" Xu Qiu pointed to the petri dish containing the substrate.
　　 "Okay, just recently I may need to fill up some data. After I teach you, you know..." Chen Wanqing stared at Xu Qiu with her eyes wide open.
　　 "Understand, the school sister’s business is my business." Xu Qiu hurriedly responded.
　　 "Okay, it's settled, let me teach you how to use the glove box first." Chen Wanqing smiled.
　　 [Detected glove box skills, whether to record? 】
　　 "Record."
　　…………
　　"This huge box is the glove box. It has very good airtightness. The front is a transparent explosion-proof glass, surrounded by iron sheets.
On the 　　 explosion-proof glass are two rubber gloves protruding outwards. The operator can use these two rubber gloves to extend into the box to perform experimental operations in the box. "Chen Wanqing said.
　　 Xu Qiu noticed that on the diagonally opposite side of the glove box, there was a larger glove box with three rubber gloves outside, and asked:
　　 "Senior sister, there is also a glove box over there, it should be used to make solar cell devices, why do you want to separate them, is there any particularity?"
　　 "In fact, it is best to put them together, but our laboratory has insufficient space, so we can only put them like this." Chen Wanqing said.
　　 Xu Qiu nodded, and then carefully looked at the box in front of him. It was about one meter six long, two meters high, and about one meter two meters deep.
　　 He roughly estimated the price of the glove box in his mind.
　　 iron sheet, explosion-proof glass, rubber gloves, the combined material cost is up to several thousand yuan less.
　　 But after the finished product is made, the price will definitely have to be doubled, it must be tens of thousands, so just ask.
　　 "Senior sister, how much is this glove box?"
"The total cost of the two sets is more than 380,000. Teacher Wei and the owner of the manufacturer know and give a discount. Now there are not many domestic manufacturers that can make glove boxes. This one happens to be local to the magic city." Chen Wanqing said .
　　 "It costs 200,000 per unit, I thought it would cost tens of thousands. It seems that when I evaluate the price in the future, I add 0 after the estimate, which is almost close to the real price." Xu Qiu sighed.
　　 "Scientific research, just burn money like this, and you will get used to it." Chen Wanqing chuckled lightly, and then went on to introduce:
　　"The atmosphere inside the glove box is nitrogen, argon and other inactive gases. We use nitrogen atmosphere. If it is a lithium battery, argon must be used.
　　The use of nitrogen is to create anhydrous and oxygen-free conditions. The experimental results obtained in this way are highly reliable and repeatable, because some of the materials in the battery devices we make are sensitive to oxygen and water.
　　You can see the numerical control panel here. There are real-time content of water and oxygen in the box, which are now less than 0.1ppm.
　　During the experiment, it may increase to about 10ppm, which is not a big problem.
　　 But if it is kept above 100ppm for a long time, it will have a great influence on the experimental results. "Chen Wanqing said.
　　 Xu Qiu knows that ppm represents the concentration of parts per million, which means that the proportion of oxygen molecules and water molecules in the glove box is less than one part per million.
　　 "The glove box is connected to a nitrogen cylinder through a gas pipeline, and nitrogen can be refilled at any time to prevent air backflow due to insufficient pressure inside the box."
　　 Chen Wanqing finished speaking and led Xu Qiu to the two cylinder cabinets placed in the corner of the laboratory.
　　The cabinet body is painted with eye-catching yellow paint, and the ground is also covered with yellow and black warning tape.
Sister 　　 opened the cylinder cabinet, Xu Qiu saw that each cabinet contained two cylinders, and there were four cylinders in total.
"We only have two types of cylinders, one is high-purity nitrogen, and the other is a mixture of nitrogen and hydrogen with a volume ratio of 95:5. The former is used to supply gas to the glove box and nitrogen gun, and the latter is used to clean the glove box. "Chen Wanqing said.
　　 Then, she looked at Xu Qiu earnestly and said, "The operation of a steel cylinder is dangerous, so before you are thoroughly familiar with it, you must be present before you can operate it."
　　 "Okay, Senior Sister." Although Xu Qiu has a system, he nodded obediently.
　　"This is high purity nitrogen with a capacity of 40 liters. The internal pressure is about 12.5 MPa. Because the pressure is too high, it cannot be used directly.
　　In order to solve this problem, steel cylinders are usually equipped with a pressure reducing valve, which can reduce the pressure to 0 to 2.5 MPa.
　　 In our daily use, the pressure range is 0.6 to 1 MPa, which is 3 to 5 divisions of the pressure reducing valve scale.
　　There is another very important point. The main valve of the cylinder is loosened and the pressure is higher; on the contrary, the tightening of the pressure reducing valve increases the pressure. "Chen Wanqing said.
　　 "Senior sister, the cylinder looks heavy, how did it come?" Xu Qiu asked, touching the body of the cylinder.
　　 "After placing an order in the school’s laboratory management system, the drug warehouse will send a master to deliver the cylinders in time, and then install them before shipping the used empty cylinders. UU Reading www.uukanshu.com"
　　 After studying the cylinder, the two returned to the glove box again.
　　" There are two foot pedals at the bottom of the glove box. One is for pressurization, which is to add nitrogen to the box, and the other is for decompression, which is to extract the nitrogen from the box and vent to the atmosphere.
　　The tank has an initial set pressure, usually 0.3bar, which is 0.3 atmospheres. When the pressure in the tank is lower than this value, it will automatically add air.
　　 When the pressure is too high, the safety valve on the top of the box will be opened, and the equipment will be forced to stop working.
　　The threshold is about 7bar, so pay attention to the pressure gauge when using it.
　　 But after you are familiar with it, you can judge the pressure based on your hand, without looking at the pressure gauge.
　　 When you want to enter the box through rubber gloves, you must be slow to prevent excessive pressure and open the safety valve.
When 　　 comes out, it should be slow to prevent the formation of negative pressure, which may cause air to enter. "
　　 "Xu Qiu, you can do it first," Chen Wanqing said.
　　……
　　 After putting on the lab coat and taking protective measures, Xu Qiu tried to put his hand into the glove box through rubber gloves.
　　 He first found the ten fingers on the rubber glove, put it on his hand, and then slowly stretched it in.
　　 was easy to enter at first, and as his hand moved forward, the resistance he encountered gradually increased.
　　 Seeing this, Xu Qiu stepped on the pressure relief pedal lightly and heard a hissing air current, and the resistance slowly decreased.
　　 continued to move forward, and finally reached the deepest point, with both arms fully extended into the box.
　　 Xu Qiu felt it, because the rubber was very thick and it was much cumbersome to operate.
　　 Finally, he slowly stretched out his hand and left the glove box.