Effect of chemical conditioning on the triboelectrification of coal and mineral particles

Chemical conditioning was used to modify the triboelectrification of coal and mineral particles.The chemicals tested included starch,lignin,kerosene,ethanol,acetic acid,salicylic acid,sodium oleate,Sodium Hexametaphosphate(SH),sodium silicate, Sodium Dodecylbenzenesulfonate(SDBS),Sodium Bicarbonate(SB) and ammonia.A high-speed,dry mixing method was employed.The charge-to-mass ratio of the coal and mineral samples,both untreated and treated,was tested using a Faraday cup. Dielectric constants were determined by measuring capacitance.It is found that the selectivity of the additives toward coal or minerals is not consistent.Salicylic acid is the optimal additive to enhance the triboelectrification performance of coal samples.Starch, lignin and sodium oleate are suitable for removal of pyrite.SH,sodium silicate,SDBS,SB and ammonia are suitable additives for the removal of ash-forming minerals.

Triboelectrification induced UV emission from plasmon discharge

UV is a high-energy electromagnetic radiation that has been widely used in industrial production and the scientific research domain. In this work, a deep UV light emission was obtained using triboelectrification induced plasma discharge without any extra power supply. By a mechanical friction between polymer and quartz glass, the triboelectric charges cause a changing electric field, which may bring plasma discharge of low pressure gas （Ar-Hg） and give out 253.7 nm irradiation. The UV light caused by continuous friction can excite a trichromatic phosphor and afford a bright white light emission. A UV sterilization experiment shows that -98% of Escherichia coil can be killed in 30 min by UV irradiation, which reveals that a self-powered sterilization apparatus with good sterilization effect was fabricated. This work provides a novel design to fabricate a self- powered UV light emitting device using low-frequency mechanical friction and realizes the coupling of triboelectrificafion and plasma luminescence, which may further expand the application of UV light in special circumstances.

Fundamental theories and basic principles of triboelectric effect: A review

Long-term observation of the triboelectric effect has not only proved the feasibility of many novel and useful tribo-devices(e.g., triboelectric nanogenerators), but also constantly motivated the exploration of its mysterious nature. In the pursuit of a comprehensive understanding of how the triboelectric process works, a more accurate description of the triboelectric effect and its related parameters and factors is urgently required. This review critically goes through the fundamental theories and basic principles governing the triboelectric process. By investigating the difference between each charging media, the electron, ion, and material transfer is discussed and the theoretical deduction in the past decades is provided. With the information from the triboelectric series, interesting phenomena including cyclic triboelectric sequence and asymmetric triboelectrification are precisely analyzed. Then, the interaction between the tribo-system and its operational environment is analyzed, and a fundamental description of its effects on the triboelectric process and results is summarized. In brief, this review is expected to provide a strong understanding of the triboelectric effect in a more rigorous mathematical and physical sense.

Effect of contact- and sliding-mode electrification on nanoscale charge transfer for energy harvesting

The process of charge transfer based on triboelectrification （TE） and contact electrification （CE） has been recently utilized as the basis for a new and promising energy harvesting technology, i.e., triboelectric nanogenerators, as well as self- powered sensors and systems. The electrostatic charge transfer between two surfaces can occur in both the TE and the CE modes depending on the involvement of relative sliding friction. Does the sliding behavior in TE induce any fundamental difference in the charge transfer from the CE？ Few studies are available on this comparison because of the challenges in ruling out the effect of the contact area using traditional macro-scale characterization methods. This paper provides the first study on the fundamental differences in CE and TE at the nanoscale based on scanning probe microscopic methods. A quantitative comparison of the two processes at equivalent contact time and force is provided, and the results suggest that the charge transfer from TE is much faster than that from CE, but the saturation value of the transferred charge density is the same. The measured frictional energy dissipation of -11 eV when the tip scans over distance of I A sheds light on a potential mechanism： The friction may facilitate the charge transfer process via electronic excitation. These results provide fundamental guidance for the selection of materials and device structures to enable the TE or the CE in different applications; the CE mode is favorable for frequent moderate contact such as vibration energy harvesting and the TE mode is favorable for instant movement such as harvesting of energy from human walking.

A self-powered gas sensor based on PDMS/Ppy triboelectric-gas-sensing arrays for the real-time monitoring of automotive exhaust gas at room temperature

A new self-powered active gas sensor for realtime monitoring of automotive exhaust gas was devised.The pipe-shaped device was fabricated from polydimethylsiloxane/polypyrrole(PDMS/Ppy)triboelectric gas-sensing unit arrays.The gas-sensing units can actively convert the mechanical energy of gas flow into a triboelectric current.The output current signal depends on the species and concentrations of the target chemical gases(CO,NH3,NO)in the gas flow,and thus can be used as a sensing signal.The device consists of seven gas-sensing units with different Ppy derivatives.As the different sensing units respond to the gases in different ways,the device can differentiate between gas species.The working mechanism is attributed to the coupling effect between the triboelectric effect of PDMS/Ppy and the gas-sensing properties of Ppy.The device can be installed in the tailpipe of an automobile,and can thus analyze the exhaust gas in real time without the need for any external electrical power.The results of the present study spur a new research direction for the development of automotive exhaust gas monitoring systems,thus playing an important role in the detection of air pollution.

A supportive electrostatic model of the COVID-19 airborne transmission

A mechanism-oriented model is proposed here as a speculative but robust attempt to understand whether there might be any increased risk of electrostatically induced contamination,with relevant consequences from the epidemiological viewpoint.This could also be the case for the COVID-19 spreading because an amount of micro-sized droplet nuclei,often carrying net electric charge,are expected to be electro-dynamically involved in a physical process originated by the natural and unperceivable static electrification of human beings.The effects of the triboelectric charging have long been successfully tested because the phenomenon under examination is also implied in the genesis of the electrostatic discharge(ESD),a demanding key objective in the special context of electromagnetic compatibility(EMC).Therefore,the ultimate purpose of this technical paper is to provide valuable insights into infection control,building on what is already being done for maintaining static-safe environments.The stature of the applied model can be further appreciated because some currently observed climate-dependent and sexlinked different vulnerabilities to COVID-19 are critically examined by unique sound arguments.These ultimately focus attention on ambient relative humidity and worn shoes,the latter differing for typology,size and material,for their integrated control of the inadvertent human aptitude to buildup tribocharges.These would appear as a dreadful prerequisite for charge bearing droplets in the airborne state to be efficiently attracted/repelled according to the described electrostatic mechanism.