Chapter 113: 1mapingchuan

　　 The three of them first came to Room 530 of Xiancai Building.
　　 Inside the house, the gel chromatograph has stopped working.
　　 Chen Wanqing turned on the computer next to the instrument, found their test data, and started data processing.
　　 There is a special software for data processing. You only need to import the results and apply the processing algorithm written in advance to automatically fit and calculate.
　　 However, if the curve shape of the test result is abnormal, it may not be able to fit automatically. In this case, manual operation is required.
　　 Fortunately, Xu Qiu and the others did not encounter such a situation, and all the data automatically got results after importing.
　　 If every data has to be processed manually, it may be here all morning.
　　The results show that the number average molecular weight of the eight polymer materials is between 20,000 and 50,000, and the polydispersity coefficient is between 1.6 and 1.9.
　　This is normal data in polymer donor materials in the field of organic photovoltaics.
　　If the molecular weight is too small, it indicates that the polymer main chain is too short, and the charge transport performance of the material will deteriorate;
　　 The molecular weight is too large, unless there are particularly long branches, otherwise solubility problems will occur.
　　 And the polydispersity coefficient is too large, for example, more than 2.0, then using this batch of materials for batteries, the repeatability of the device performance data will be very poor.
　　 Maybe the same batch of materials, under the same conditions, some can achieve 8%, some only 7%, 6% or even lower.
　　 As for the polydispersity coefficient is less than 1.5, that is really good, and the repeatability of the experiment will be very good.
　　 Xu Qiu also wanted to achieve such a result, but based on the current synthesis conditions, it could not be achieved.
　　 After processing the data, copy it with a USB flash drive, and the three people disposed of the waste liquid and other experimental garbage, locked the door and left.
　　 only took more than half an hour in total.
　　……
　　 Then, I went to room 528 next to me.
There are three instruments in 　　, including the DSC and TGA that will be used today, and a TMA thermomechanical analyzer.
　　TMA is a technology that measures the functional relationship between the deformation of a substance and the temperature and time under the action of the program temperature and non-vibration load. It mainly measures the expansion coefficient and phase transition temperature of the substance.
　　 is generally to test structural materials such as rubber and fibers. The polymer materials used by Xu Qiu and others for organic photovoltaics are functional materials, and this characterization method is not available.
　　 Xu Qiu didn't return all the experimental skills of DSC and TGA to the teacher. After all, it was an experiment just learned last year.
　　 He and his senior sister conducted experiments together, and the senior sister watched and studied nearby.
　　 TGA is relatively simple in principle, that is, under the atmosphere of nitrogen protection, the material is gradually heated to increase its temperature, and the weight of the material changes over time.
　　Because it is programmed temperature control, the temperature and time are one-to-one correspondence, so the change curve of the weight of the material with the temperature can be obtained.
　　 When the material loses a large amount of weight, it may mean that the solvent in the material evaporates, loses crystal water, decomposes, and secondly decomposes.
The temperature corresponding to 　　 is the critical temperature at which the above reaction occurs.
　　The operation is also simple, just put the weighed sample into the crucible, then hang it in the instrument, set the heating program according to the demand and execute it.
　　DSC also uses program temperature control, but it can achieve precise temperature control from minus 80 degrees Celsius to more than 1,000 degrees Celsius.
　　Because it involves low-temperature experiments, the low-temperature cooling device needs to be turned on in advance.
　　The DSC in the material department is a power compensation type.
　　The internal heating type is adopted. The holders for the sample and the reference are independent components. At the bottom of the sample and the reference, there is a platinum thermal resistance for heating and a platinum sensor for temperature measurement.
　　 In the thermal test, many parts are made of precious metal platinum.
　　 It uses the principle of dynamic zero balance, which requires the temperature of the sample and the reference material to maintain a dynamic zero balance state regardless of whether the sample absorbs heat or exotherms, that is, to maintain the temperature difference between the sample and the reference material to zero.
"By measuring the difference in energy required to maintain the sample and the reference at the same temperature, the change in sample enthalpy can be reflected, and the glass transition temperature and crystallization temperature of the material can be obtained.
　　 However, the polymer materials generally used for organic photovoltaics are weakly crystalline, and most of the measured DSC images are of a map, and the curve shape is similar to a parallelogram.
　　 There is no distinction between patterns like this, and no other useful information can be obtained except to prove its weak crystallinity.
　　 But after all, it is a routine characterization test, and the process should be followed.
　　 Eight samples, start with the test from the sister.
　　 Weigh the sample, put it into the crucible, and place it on the platform of the DSC instrument.
　　 Set the program temperature control, from normal temperature to a high temperature first, such as 250 degrees Celsius, and then back to minus 20 degrees Celsius, and then rise to a high temperature, cycle again.
　　 Generally, the high temperature setting temperature is lower than the decomposition temperature of the material, which is the temperature measured from the TGA.
　　 It is worth noting that if the material will release a large amount of gas or explode at high temperature, DSC and TGA cannot be tested.
　　 Otherwise, after half of the measurement, the material exploded inside the instrument.
　　 Test failures are trivial matters, and it is likely to damage the instrument.
The 　　 department may not directly trouble you, but you will definitely seek compensation from your tutor, and then you will be prepared to face the angry tutor.
　　 When the temperature of the DSC cooling device reaches minus 80 degrees Celsius, start the test.
　　 The test time is very long~EbookFREE.me~A sample usually takes about an hour. People can leave during the test and just lock the door.
　　 However, neither of these two instruments can automatically change samples, so changing samples still requires manual operation.
　　 There is a key problem. The first and second materials floors were built at the same time. The two buildings were next to each other. The advanced materials building was rebuilt later, which was far away from the first and second materials.
　　 Counting the time to go up and down the stairs, it takes about fifteen minutes to walk from the first to the first, and it takes half an hour to go back and forth.
　　Riding a shared bicycle is faster, but for a shared bicycle on campus, it may stop for ten minutes, then come back and look for it, and the bicycle will be gone.
　　 Xu Qiu thought for a while and said:
　　 "When I stay and watch, you can go back. Anyway, I want to write an article. It's the same here.
　　 My computer is still on the first floor of the material..."
　　 "Leave it to me, and I'll send it to the brother later." Han Jiaying said.
　　 "That line, you should go back first."
　　 This school girl is still on the road.
　　……
　　 Saying goodbye to the two, Xu Qiu looked at the layout of the laboratory.
　　 The area of ​​this laboratory is similar to that of Caiyi 216, but there are only three equipment, and it looks relatively empty.
　　 There is an air conditioner on the wall, as well as a few tables and stools.
　　 The air conditioner is not turned on, and he has no plans to turn it on.
　　 Just three days ago, the magic capital came to Autumn Tiger.
　　 It is no longer so hot during the day, and it starts to get cold at night.
　　 It seems that that day is separated by summer and autumn.
　　 After half an hour, the DSC curve of the first sample of Sister-in-law has run halfway, and looking at its shape, it is really flat.
　　 Xu Qiu shook his head, calculating the time in his mind, the school girl should be coming over.