More valuable chemical nanomaterials are created by flashing

Scientists at Rice University used “flash” materials to synthesize graphene and other substances, turning their attention to boron nitride, which is highly valued for its thermal and chemical stability.

During the research of chemist James tour in rice laboratory, a precursor was placed in rapid heating and cooling to produce two-dimensional materials, in this case, pure boron nitride and boron nitride carbon. So far, these two substances are difficult to mass produce, and it is almost impossible to produce in a soluble form.

The report published by the laboratory in the journal advanced materials introduces in detail a technology introduced by tour laboratory in 2020 – Flash Joule heating, how to prepare purified microscopic boron nitride sheets containing different degrees of carbon through adjustment.

The experiment of this material shows that boron nitride sheet can be used as part of a powerful anti-corrosion coating.

“Boron nitride is a very popular 2D material,” tours said. “It can be mass produced and now it is mixed with a lot of carbon, which makes it more versatile.”

At the nanoscale, boron nitride has several forms, including a hexagonal structure that looks like graphene, but boron and nitrogen atoms alternate instead of carbon atoms. Boron nitride is soft, so it is often used as an additive in lubricants and cosmetics. It is also found in ceramics and metal compounds to improve their ability to deal with high temperatures.

Michael Wang, a Rice chemical engineer, recently reported that boron nitride is an effective catalyst that helps destroy PFAS, a dangerous “permanent chemical” found in the environment and human beings.

Flash Joule heating involves filling the source material between the two electrodes of the tube and sending a fast current through them. For graphene, the material can be anything containing carbon. Food waste and waste plastic auto parts are just two examples. The process also successfully separates rare earth elements from fly ash and other raw materials.

In the experiment led by Weiyin Chen, a graduate student of rice, the laboratory sent ammonia boron (bh3nh3) together with different amounts of carbon black into the flash chamber, depending on the product required. Then, the sample is flickered twice. For the first time, 200 volts is used to remove the excess elements in the sample, and 150 volts is used to complete the process again. The total flicker time is less than one second.

Microscopic images show that these sheets are turbocharged – that is, they are not aligned, like poorly stacked plates – and their interaction has weakened. This makes the flakes easy to separate.

They are also easy to dissolve, which leads to anti-corrosion experiments. The laboratory mixed flash boron nitride with polyvinyl alcohol (PVA), coated the compound on the copper film, and exposed its surface to sulfuric acid bath for electrochemical oxidation.

Flash compounds proved to protect copper more than 92% than PVA alone or similar compounds with commercial hexagonal boron nitride. Microscopic images show that this compound creates a “tortuous diffusion path for corrosive electrolytes to reach copper” and also prevents the migration of metal ions.

Chen said that the conductivity of the precursor can be adjusted not only by adding carbon, but also by adding iron or tungsten.

He said the laboratory saw the potential for flashing additional materials. “Precursors that have been used in other methods, such as hydrothermal method and chemical vapor deposition method, can be tried in our flash method to see if we can prepare more products with metastable characteristics,” Chen said “We have proved that metallic carbides and transition metal dihalogenated compounds in the scintillation metastable phase are worthy of further study.”