Atmospheric Pressure Plasma Jet in Ar and O_2/Ar Mixtures:Properties and High Performance for Surface Cleaning

An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20~32 kHz, and their effects on the cleaning of surfaces have been studied. Properties of the jet discharge are studied by electrical diagnostics, including the waveform of discharge voltage, discharge current and the Q-V Lissajous figures. The optical emission spectroscopy is used to measure the plasma parameters, such as the excitation temperature and the gas temperature. It is found that the consumed power and the excitation temperature increase with increase of the discharge frequency. On the other hand, at the same discharge frequency, these parameters in O2/Ar mixture plasma are found to be much larger. The effect on surface cleaning is studied from the changes in the contact angle. For Ar plasma jet, the contact angle decreases with increase of the discharge frequency. For O2/Ar mixture plasma jet, the contact angle decreases with increase of discharge frequency up to 26 kHz, however, further increase of discharge frequency does not show further decrease in the contact angle. At the same discharge frequency, the contact angle after O2/Ar mixture plasma cleaning is found to be much lower compared to the case of pure Ar. From the results of quadrupole mass-spectrum analysis, we can identify more fragment molecules of CO and H2O in the emitted gases after O2/Ar plasma jet treatment compared with Ar plasma jet treatment, which are produced by the decomposition of surface organic contaminants during the cleaning process.

Multi-objective genetic algorithm for the optimization of road surface cleaning process

The parameters affecting road surface cleaning using waterjets were researched and a fuzzy neural network method of calculating cleaning rate was provided. A genetic algorithm was used to configure the cleaning parameters of pressure, standoff distance, traverse rate and angle of nozzles for the optimization of the cleaning effectiveness, efficiency, energy and water con-sumption, and a multi-objective optimization model was established. After calculation, the optimized results and the trend of variation of cleaning effectiveness, efficiency, energy and water consumption in different weighting factors were analyzed.

A Diamond Electrochemical Cleaning Technique for Organic Contaminants on Silicon Wafer Surfaces

Peroxodiphosphate anion （a powerful oxidant） can be formed in a special water-based cleaning agent through an electrochemical reaction on boron-doped diamond electrodes. This electrochemical reaction was applied during the oxidation,decomposition, and removal of organic contaminations on a silicon wafer surface, and it was used as the first step in the diamond electrochemical cleaning technique （DECT）. The cleaning effects of DECT were compared with the RCA cleaning technique, including the silicon surface chemical composition that was observed with X-ray photoelectron spectroscopy and the morphology observed with atomic force microscopy. The measurement results show that the silicon surface cleaned by DECT has slightly less organic residue and lower micro-roughness,so the new technique is more effective than the RCA cleaning technique.

Environment-friendly surface cleaning using micro-nano bubbles

Cleaning a surface using a solution containing a large number of micro to nano scale bubbles has significant advantage regarding environmental protection.This review first briefly introduces the cleaning mechanism of micro-nano bubbles(MNBs),including physical and chemical effects.Then the applications of MNBs in cleaning of metal parts,precision parts,cultural relics or food are introduced.After that,coupled cleaning method of ultrasound and bubbles is introduced.Finally,the characterization methods for the cleaning effect are introduced,which mainly focuses on the changes of physico-chemical properties(mass or cleaning area,infiltration,colony number and light scattering intensity)of the cleaned parts or that(like conductivity)of the solvent.It is believed that MNBs technology will be applied in a broader range of surface cleaning applications.

Effects of Multiple Cleaning and Disinfection Interventions on Infectious Diseases in Children: A Group Randomized Trial in China

Objective To assess the effectiveness of multiple cleaning and disinfection interventions in the homes and kindergartens, in reducing gastrointestinal and respiratory illnesses of children. Methods From October 2010 to September 2011, we performed a prospective, controlled study in China. 408 children under 5 years old were recruited and group randomized into intervention and control groups. Families and kindergartens in the intervention group were provided with antibacterial products for hand hygiene and surface cleaning or disinfection for one year. Each child＇s illness symptoms and sick leave were recorded every day. Results A total of 393 children completed the study, with similar baseline demographics in each of the 2 groups. Except for abdominal pain, the odds of symptoms （fever, cough and expectoration, runny nose and nasal congestion, diarrhea）, illness （acute respiratory illness and gastrointestinal illness）, and sick leave per person each month were significantly reduced by interventions. The rates of fever, diarrhea, acute respiratory illness, gastrointestinal illness and sick leave per person per year were significantly decreased as well. Conclusion Not only the acute respiratory children were significantly reduced by multiple and gastrointestinal illness but the sick leave rate in interventions.

Conditions for laser-induced plasma to effectively remove nano-particles on silicon surfaces

Particles can be removed from a silicon surface by means of irradiation and a laser plasma shock wave.The particles and silicon are heated by the irradiation and they will expand differently due to their different expansion coefficients,making the particles easier to be removed.Laser plasma can ionize and even vaporize particles more significantly than an incident laser and,therefore,it can remove the particles more efficiently.The laser plasma shock wave plays a dominant role in removing particles,which is attributed to its strong burst force.The pressure of the laser plasma shock wave is determined by the laser pulse energy and the gap between the focus of laser and substrate surface.In order to obtain the working conditions for particle removal,the removal mechanism,as well as the temporal and spatial characteristics of velocity,propagation distance and pressure of shock wave have been researched.On the basis of our results,the conditions for nano-particle removal are achieved.

Investigation on the influence of vortex generator on particle resuspension

The vortex generator(VG)and its well-known effect in flow optimization are widely studied and employed across different engineering sectors.However,while the same working principles of VG may be well suited for the applications on surface-cleaning technologies,such promising potential is hardly,if any,explored in the published literature.Therefore,in the present study,the influence on flow-induced particle resuspension brought by a rectangular vG in a channel flow is investigated with the help of highfidelity computational fluid dynamics simulations.Substantial increases of particle removal forces and resuspension rates are discovered in long,strip-like regions with reduced boundary-layer thickness resulted from the vG-induced vortices,and the enhancement effect is especially significant for configurations with the VG installed at a greater angle of attack.It is also shown that while the resuspension enhancements on the lower and the upper surfaces of the channel exhibit distinct statistical characteristics,having a VG in the channel improves the overall particle-removing capability of the channel flow by introducing higher surface-averaged removal forces and particle resuspension rates.Last but not least,the increase of resuspension rate is especially significant for the smaller,micron-scale particles which are otherwise hardly disturbed by a VG-less channel flow,and such resuspension-enhancement effectgenerally subsides with increasing particle size.

Adhesive properties study on the interfaces of AlN and metal of Pd,Ag and Cu

A1N is used as high power LED package material because of its excellent thermal conductivity. But its poor adhesive with metal is not compatible with the later processing sequence. The properties of the bonding between the deposited palladium, silver, copper and the clean Al-terminated （0001） surface of wurtzite AIN are investigated by using the density-functional the- ory. The results show that the sites of deposited metal atoms on N site are more stable than that on A1 site. Relaxations are found at all the studied interfaces. The bonding energies of Pd/A1N, Ag/A1N and Cu/A1N are respectively 2.75, 1.98, 2.26 eV. Hybridizations of s orbit and p orbit of the deposited metal atoms are observed, which contributes to the bonding energy of interface. The moving to lower energy state of the d orbit and the easier transfer of electrons to semi-empty d orbit in the case of deposited Pd results in the higher bonding energy of Pd/A1N interface.

Reversible hydrogenation restores defected graphene to graphene

Graphene as a two-dimensional material is prone to hydrocarbon contaminations,which can significantly alter its intrinsic electrical properties.Herein,we implement a facile hydrogenation-dehydrogenation strategy to remove hydrocarbon contaminations and preserve the excellent transport properties of monolayer graphene.Using electron microscopy we quantitatively characterized the improved cleanness of hydrogenated graphene compared to untreated samples.In situ spectroscopic investigations revealed that the hydrogenation treatment promoted the adsorption of water at the graphene surface,resulting in a protective layer against the re-deposition of hydrocarbon molecules.Additionally,the further dehydrogenation of hydrogenated graphene rendered a more pristine-like basal plane with improved carrier mobility compared to untreated pristine graphene.Our findings provide a practical post-growth cleaning protocol for graphene with maintained surface cleanness and lattice integrity to systematically carry a range of surface chemistry in the form of a well-performing and reproducible transistor.

Design and experiment of an upper-side-discharge straw-returning and bundle self-unloading integrated corn residual film recycling machine

Due to the arid climate,flat terrain,certain irrigation sources and high popularization of mechanical harvest in Hexi Irrigation Area of Gansu Province,the widely adopted half film-flat-mulching for corn cultivation faces serious adverse situations,such as high soil compactness,strong film-soil adhesion,significant straw stubble and thick covering accumulation on film.Therefore,a new kind of segmented combination upper-side-discharge straw-returning and bundle self-unloading integrated corn residual film recycling machine was proposed.The scheme was characterized by small volume,low resistance,low complexity and film-impurities twice separation.It is constructed based on the concept of module subsection combination.It was composed of film surface straw cleaning device and the followed residual film recycling machine,in terms of function,any usage requirements of separate and joint operations can be satisfied.The film surface straw cleaning device is responsible for the removal of vertical corn straw and ground covering beyond the film.Although its stubble cutter roller obtuse-angle Lshaped blades paired single-helix arrangement is simple,it runs smoothly and the straw crushing effect is good enough.The layout that upper-side-discharge straw-returning cross-range screw conveyor auger is back and beyond the stubble cutter roller,eliminates the common connecting transportation mechanism between crushing and straw-returning section,so that,the system structure can be optimized and the efficiency has been significantly improved.The integrated residual film recycling machine is composed of triangular pyramid arc two-stage wing(TPATSW)type film lifting shovel,rod-tooth-belt type film-impurities separation device and semi-enclosed shaftless bundle film collector.Among them,TPATSW type film lifting shovel has good corn root whisker cutting effect,low soil contact resistance and small soil congestion area,but its ability to lift film is strong,more importantly,the special segmented configuration of shovel handle and the body,shortens the overall machine length significantly.For semi-enclosed shaftless bundle film collector,however,a new scheme of eight sub-rolls rotate in the same direction,to roll the residual film into a bundle is innovatively adopted.Under its own parameters,the system has the lowest sub-roll rotation speed that can bundle the residual film without shaft inside the film collecting chamber,rather than on any subroll itself.The gap between the sub-rolls can separate impurities for the second time.After the film collection reaches the standard,the film collector can dump the residual film directly,which is simple and efficient.The field orthogonal test data of the prototype show that,the optimal parameter combination is:film lifting shovel earth angle is 30°,its operation depth is 50 mm and the machine forward speed is 5.0 km/h.The average residual film recycling rate and the crushed straw qualified rate under the optimal parameters are 84.9%and 90.3%respectively,which meet the requirements of the national and industrial standards.The research solved the passive situation that there was no matching equipment for the recycle of residual film in corn field in Hexi Irrigation Area effectively.