In the past few decades, nanoscience has developed rapidly, so researchers began to explore how to apply nanomaterial technology to enhance heat transfer. In 1995, Choi of Argonne National Laboratory in the United States first proposed the concept of "nanofluid", which has since innovatively combined nanotechnology with the traditional field of thermal engineering.

Nanofluid is a new uniform and stable heat transfer medium prepared by adding a certain amount of nanoparticles (size 1-100nm) to traditional liquids. Compared with traditional heat transfer fluids, it can effectively improve the heat transfer performance of thermal systems and meet the enhanced heat transfer requirements under some special conditions (microscale conditions), so it is considered a new type of heat transfer fluid.

However, the potential of nanofluids does not stop there. After being used in heat exchange systems as a bridge between heat sources and cooling equipment, it has gradually expanded to fields such as tribology, solar collectors, and biomedicine. In the past decade, research on nanofluids has aroused the interest of researchers at home and abroad and has become one of the hot spots of concern.

Aggregation state of nanoparticles in fluids

Hexagonal boron nitride (h-BN) is an isoelectric material similar to graphite. It has a lamellar structure similar to graphite and is called white graphite. It has a unique structure, excellent mechanical strength, and high thermal resistance. Stability, oxidation resistance and chemical inertness make it a material with great application prospects. If the h-BN sheet structure is peeled off to obtain h-BN sheets with a thickness of several nanometers, it can become boron nitride nanosheets (BNNS), which is another two-dimensional nanomaterial.

The most outstanding thing about boron nitride is its application advantages when used in nanofluids. details as follows:

①Improve tribological properties

Friction exists in almost all moving systems (drilling, cutting, cutting, machining and forming, etc.). Excessive friction will cause energy loss, mechanical failure and low work efficiency. In order to minimize the adverse effects of friction, solid or liquid lubricants are usually used, with the latter generally being the first choice for eliminating friction.

②Improve heat transfer performance

In the electronic and electrical industry, how to improve the thermal management capabilities of equipment is a very important topic. Many electronic products and mechanical equipment today use air cooling to remove waste heat. However, the thermal conductivity coefficient of air is extremely low, which limits the heat dissipation efficiency of heat dissipation equipment. Liquid cooling can effectively solve the heat dissipation problem under high heat flux densities in the electrical and electronics industry due to its high heat dissipation efficiency and quiet operation.

③Enhance photothermal conversion efficiency

Heating water using solar radiation is one of the many beneficial things that can be done with solar energy. Efficient use of solar energy can reduce or even replace the traditional way of providing the hot water needed for equipment through the combustion of fossil fuels. The collector is a key component of the solar water heating system, which can collect clean solar energy and convert it into thermal energy for water heating. Methods of increasing heat transfer through collectors can be divided into two categories: passive methods and active methods. Compared with active methods, passive methods do not require the action of external force. Utilizing nanofluids as heat transfer media in direct absorption solar collectors is a passive method to improve heat transfer.

④Improve drug loading capacity

Carbon nanomaterials have been extensively studied in medical fields such as biosensing, medical imaging, and cancer cell targeted therapy. However, carbon nanomaterials have certain cytotoxicity that limits their clinical application. Therefore, alternatives to carbon materials have been developed. Things are very meaningful. As a structural analog of carbon nanomaterials, BN's performance matches that of carbon materials. Its low cytotoxicity, excellent chemical stability and high thermal stability give it a strong competitive advantage in the medical field.

However, it should be noted that although lower concentrations of BN have been proven to be uniformly dispersed in water for a long time, whether high-concentration BN materials can be effectively dispersed and stably in different fluid media determines the performance of boron nitride composite nanofluids. The key to large-scale application is that more research on new processes is needed in this regard.