Particle Removal Rate Research Articles

メガヘルツ周波数範囲のクォーツトランスデューサー超音波洗浄機を使用したポリスチレンラテックス粒子の除去の評価

This paper describes the newly developed quartz transducer ultrasonic cleaners (QTCs) operating at frequencies of 1 MHz to 3 MHz, designed to physically remove particles, including a few nano-sized particles, without causing damage to wiring patterns. The paper also discusses the potential of QTC by conducting experiments to remove submicron polystyrene latex (PSL) particles using QTC.In recent years, with the refinement and increased integration of semiconductors, there is a growing need to remove nanometer-sized particles. Conventional spray-type ultrasonic cleaners have the disadvantage of easily disrupting wiring patterns due to fluctuating sound pressure impacting the substrate surface. the QTCs were developed with the consistent sound pressure fluctuation. The QTC transmits ultrasonic waves from an ultrasonic oscillator through an elliptical quartz column and then impacts the particles on the wafer surface through the pure water between the QTC and the wafer surface. Therefore, the variation of sound pressure on the wafer surface is small. We measured the sound pressure emitted by the QTCs and confirmed that its fluctuation is significantly smaller than that of conventional spray-type ultrasonic cleaners, which exhibit large and random fluctuations in sound pressure.Subsequently, PLS particles ranging from 100 nm to 1 µm were coated onto the surface of silicon wafers with oxide film. These particles were then removed using QTCs operating at frequencies of 1, 2, and 3 MHz to elucidate the physical particle removal mechanism. The experimental results showed that the particle removal rates (PREs) tended to decrease as the particle size decreased. Regarding frequency dependence, the PREs increase with higher frequencies and also with higher amplitudes of the QTC. The removal of PSL particles in spray-type ultrasonic cleaning has been confirmed using drag force analysis. It has been observed that smaller PSL particles result in lower drag forces, leading to a decrease in the PRE. The same trend is observed in the present experiment. However, when the relationship between drag forces and PREs was confirmed using QTCs, the variations of PRE became significantly smaller as the frequency of QTCs increased. From this result, it was confirmed that the cleaning method developed this time with QTCs is easy to control with less turnover using a high frequency in the megahertz band.

Study of Chemical-Physical Cleaning Technologies for Better Particle Removal Trapped on the Crystal Defects of 4H-SiC

SiC, compared to conventional Si, has gained attention as a power semiconductor material due to its outstanding physical characteristics such as wide bandgap, high breakdown voltage, fast electron saturation velocity, excellent thermal conductivity, and superior mechanical strength. The fabrication process of SiC wafers follows a similar procedure to most processes except for Si single crystal growth and it requires management of various contaminants such as particles and metal impurities for high-quality SiC wafer production. The cleaning process of SiC wafers is crucial for achieving high-quality power semiconductor fabrication and high yield. The cleaning mechanism of contaminated particle for Si wafers is well known, typically utilizing RCA cleaning based on the principles of oxidation and etching with an increase in electrostatic repulsion. However, according to our previous studies, SiC shows characteristics where the chemical mixtures used in RCA cleaning do not induce oxidation and etching, it is necessary to find alternative cleaning methods for better contaminant removal distinct from Si cleaning mechanisms. Particularly, for removing particle contaminants trapped on crystal defects like triangular surface defects occurring during SiC fabrication, chemical-based cleaning methods are not effective. In this study, we evaluate various chemical-mechanical cleaning techniques for effectively removing particle contaminants on SiC wafers, specifically researching particle contamination removal within crystal defects.Given the superior mechanical strength of SiC compared to Si, this study assesses chemical-mechanical cleaning techniques, including PVA brush scrubbing technique and megasonic cleaning technique employing hydrogen dissolved functional DIW. Since most particle contamination occurs during the CMP process, 4H-SiC wafers were polished using CMP equipment to replicate particle contamination for cleaning evaluation. Furthermore, to compare and evaluate particle removal performance according to particle contamination methods, particles were contaminated using the dipping method. Particle removal efficiency was assessed by calculating the particle removal rate on SiC using optical microscopy, and the removal of particles trapped on the crystal defects was evaluated using FESEM. Both PVA brush scrubbing and megasonic cleaning methods showed excellent performance in surface particle removal. However, PVA brush scrubbing showed lower efficiency in removing particles trapped on the crystal defects, whereas megasonic cleaning method demonstrated higher efficiency, particularly when using hydrogen dissolved DIW, showed a better particle removal performance. This is attributed to the higher bubble cavitation effect observed in megasonic cleaning with hydrogen dissolved DIW, resulting in greater energy imparted upon collapse of cavitation bubbles, thus more effectively cleaning particles on the substrate surface and within crystal defects. For particle cleaning of SiC wafers, a chemical-mechanical cleaning process is excellent, and particularly, megasonic with hydrogen dissolved DIW was confirmed to be effective in removing particle contaminants trapped on crystal defects.

Advanced electro-assisted filtration of crude oil/water using a conductive mullite whiskers membrane

This study presents the development and characterization of a conductive composite membrane aimed at efficient oil-water separation via electrofiltration. The membrane comprises interconnected OH-functionalized multi-walled carbon nanotubes (OH-MWCNTs) and polyvinyl alcohol (PVA). Optimization parameters, including surface electrical resistance, water contact angle, and pure water permeance, were conducted, yielding an optimized membrane with a surface resistance of 256 Ω/sq, a contact angle of 39±2°, and a pure water permeance of 508.15 LMH/bar. The critical electric field intensity (Ecrit) was identified at 8–10 V, beyond which voltage increments had minimal flux impact. Electrofiltration experiments, incorporating filtration and backwashing, demonstrated enhanced permeate flux and oil particle removal rates under an applied electric field. Despite salt presence inducing flux reduction and fouling increase, membrane performance was still enhanced by the electric field. Energy consumption analysis revealed a 32 % reduction when combining electrical field with conventional filtration and backwashing, even at 1 mM concentration, compared to conventional filtration alone. This conductive composite membrane presents a promising, sustainable solution for effective crude oil/water separation across industries, offering improved performance, reduced fouling, and lower energy consumption.

Removal of micro-nano particles based on water-assisted enhanced plasma shock wave

Foreign micro/nanoparticles can compromise the production and performance of semiconductors, high-energy laser systems, and other technologies. Owing to the strong adhesion (in GPa) of these particles to the surfaces of these devices, removing them using traditional methods such as ultrasound is difficult. Laser plasmas at high temperatures and pressures can effectively clean the micro/nanoparticles. Compared with traditional air media, laser plasma generates stronger shock waves and water flow erosion underwater, which can effectively clean these particles. In this study, we analysed the particle removal process under the action of laser plasma in water dielectrics, primarily the distribution characteristics of particles under spatial phase transition, final removal efficiency, removal thresholds, and optimal removal regions of particles with different sizes, as well as the corresponding academic analysis based on thermodynamic effects. We used a silicon wafer that was subjected to a high-energy laser beam to generate plasma shock waves underwater, which were used to remove micro- and nano-sized impurities. We found that the shock wave pressure of the plasma and water flow gradually decreased from the centre to the outside, and the corresponding action region could be divided into three areas, namely, 0–30°, 30–45°, and 45–50°, with particle removal rates of 96.93 %, 75.52 %, and 36.60 %, respectively. For particles in the 0–30° and 30–45° regions, the maximum removal rate corresponded to particle sizes ranging from 50–200 nm and greater than 200 nm, respectively. However, in the 45–60° region, the pressure of the shock wave was lower than the fragmentation threshold and, hence, had the worst particle removal effect owing to the lowest pressure. We believe that these findings will provide guidance for the subsequent development of particle removal technologies using underwater laser plasma shock waves.

Particle characterization in commercial buildings: A cross-sectional study in 40 offices in Singapore

There is a knowledge gap in understanding how existing office buildings are protecting occupants from exposure to particles from both indoor and outdoor sources. We report a cross-sectional study involving weekly measurements of size-resolved indoor and outdoor particle concentrations in forty commercial building offices in Singapore. The outdoor and indoor particles size distributions were single mode with daytime peak number concentrations at 36.5 nm and 48.7 nm. Outdoor concentrations were significantly greater than indoors for all particle diameters. Indoor particle concentrations were generally low due to: 1) relatively high indoor particle removal (IPR) rates; 2) low indoor source strengths; and 3) low indoor particle of outdoor proportion (IPOP). We found that the ventilation system type had a substantial effect on indoor particle levels, IPR and IPOP. Through linear mixed model analyses, we identified dependencies of IPR rates with the use of MERV13 filters in supply air and filter maintenance frequency, IPOP with the use of MERV13 filters in the fresh air and supply air ducts and low particle source strength with regular daily cleaning presumably due to dust reservoir removal. Lastly, the contribution of outdoor sources was mainly seen for ultrafine and fine particles but less pronounced for coarse particles. This study provided detailed understanding of particle exposure in building offices and their influencing factors, facilitating future research on health impact of particle exposures.

Study of the water cleaning process by using CFD-DEM method: A case study of coarse filter material

In this paper, the CFD-DEM coupling method was utilized to study the water cleaning and regeneration process of fibrous filter material. The effects of cleaning flow rate, time and adhesion force on the particle removal process were simulated. The results showed that the particle removal rate had a diminishing marginal effect with the increasing of cleaning flow rate. More than 80% of the particles were removed in the initial period, and then tended to stabilize. The higher the flow rate, the shorter the time needed to achieve stability. For G4 filter material, the function between the particle removal rate and the cleaning flow rate and time was given, and the best cleaning flow rate was 1.2 m/s while the cleaning time was 30 seconds. The surface energy of the fibers plays a dominant role in the cleaning process, and the reduction 1/4 of the surface energy of the particles can effectively improve the cleaning and regeneration performance.

Numerical analysis and experimental research on the removal of CuO particles from monocrystalline silicon surfaces by picosecond laser

CuO particles on the surface of silicon wafers can seriously affect integrated circuits performance and service life. This paper carries out numerical calculations and experimental research on the removal of CuO particles from silicon substrates surfaces by picosecond laser. A thermal-stress coupled finite element model is established to simulate the changes in the temperature of silicon substrates and the thermal stress of CuO particles with laser action time and energy density, to predict the cleaning threshold of the particles and the damage threshold of the silicon substrates. The results show that the cleaning threshold for CuO particles with a particle size of 10 μm is 0.029 J/cm2 and the damage threshold for the silicon substrate is 0.512 J/cm2. As the laser energy density increases, the CuO particles removal rate on the silicon surface increases first and then decreases, and the silicon substrate roughness decreases first and then increases. When the laser energy density is 0.429J/cm2, the CuO particle removal rate reaches 93.42 %, the wafer surface is undamaged, and the roughness is as low as 1.33 nm. The ratio of Cu and Si elements on the cleaned silicon substrate surface is close to that on the silicon substrate surface before the sample was made.

Effect of combined water-jet inlets on the hydrodynamic performances in square arc-corner aquaculture tanks

To enhance the energy utilization and waste collection efficiency in a recirculating aquaculture system (RAS), this study investigates the hydrodynamic performance of a square arc-corner aquaculture tank using various combined water-jet inlets. An experimental verification system was developed for the recirculating aquaculture tank (RAT) to validate the accuracy of the computational fluid dynamics (CFD) model. This was achieved by comparing flow velocities at various monitoring points. A comprehensive analysis of the tank's hydrodynamic performance was conducted, encompassing velocity distribution, vorticity strength, flow uniformity index, resistance coefficient, Froude number, energy utilization efficiency, and particle removal rate. The results clearly showed that incorporating combined water-jet inlets greatly improved the hydrodynamic performance of the tank compared to traditional one-way inflow patterns. The combined injection method ensured a more uniform flow velocity both longitudinally and radially throughout the RAT, effectively reducing the concentration of water flow in a single direction. Additionally, the tangential injection of water flow along the tank wall promoted a more even flow rate, enhancing water mixing and maintaining a homogeneous distribution of dissolved oxygen. By arranging and spacing the injection holes appropriately, the fluidity and mixing of water were enhanced, leading to increased energy utilization and improved efficiency in pollutant collection.

Effect of bar magnet structure in magnetic separators on removal rate of magnetic particles in silica powder

In this study, the effects of the tilt angle of bar magnets on the removal performance of SUS304 wear particles by an iron removal equipment using magnets were investigated, particularly for particles smaller than 50 μm. The removal performance was verified by mixing SUS304 wear powder with silica powder of various particle size distributions. Results revealed that the-removal performance was improved by tilting the bar magnet at an appropriate angle, as the deposited powder slid off intermittently and the bar magnet surface was exposed more frequently. Moreover, the particle size distribution of the captured magnetic particles revealed that high magnetic flux density magnets effectively capture small particles. Furthermore, the effect of the anti-powder deposition plate on the removal performance was studied. The results indicated that a bar magnet with an anti-powder deposition plate reduced the powder deposition, however, the removal performance deteriorated.

Elevator Ventilation and SARS-CoV-2-Relevant Particulate Matter Removal in Three Older California Elevators

The objective of this study was to measure particulate matter (PM) total loss rates in three older (1940s, 1960s, and 1980s) elevators in California during two phases and three low-cost intervention modes. Tracer gas decay and <2 μm aerodynamic diameter nontoxic NaCl particles (PM2) were used to calculate PM2 loss rates. The NaCl particles were considered surrogates for smaller particles carrying SARS-CoV-2. Empirical PM2 loss rates were paired with modeled dynamic scenarios to estimate SARS-CoV-2-relevant PM2 removal. Mean loss rates (hr-1) ranged from 1.8 to 184. Compared to a closed-door, stationary elevator, the moving elevators had a fourfold increased mean loss rate (hr-1), while an air cleaner in a stationary elevator increased the mean loss rates sixfold. In a dynamic particle removal simulation of a ten-story elevator, PM was removed 1.38-fold faster with an air cleaner intervention during bottom and top floor stops only (express ride) and 1.12-fold faster with an air cleaner during every other floor stops. The increase in removal rates due to the air cleaner was modest due to the higher moving and open-door removal rates, except during stationary phase. The half-life of PM2 particles in a stationary elevator after all passengers have left can be 8-12 minutes following a single emission and 2-5 minutes with an air cleaner. The low particle removal rate in the stationary elevator requires an intervention so that the particle removal rate will be high to eliminate infectious aerosol. If codes permit, keeping the door open when the elevator is stationary is most effective; otherwise, an air cleaner in a stationary elevator should be used. While an air cleaner is commonly seen as a substantial improvement in reducing potential virus concentration in air, in the moving elevator scenarios, the effect is quite modest. This paper provides empirical particle loss rates inside elevators, the effectiveness of air cleaners in a dynamic elevator space, two approaches to control infectious agents while the elevator is stationary, and support for a precautionary approach towards elevator use amidst a pandemic.

Effect of forceful suction and air disinfection machines on aerosol removal

BackgroundsDental procedures involving drilling and grinding can produce a significant amount of suspended aerosol particles (PM) and bioaerosols. This study aims to analyze the size and concentration of aerosol particles generated during drilling and to investigate the effectiveness of two air exchange systems, namely forceful suction (FS) and air disinfection machines (DM), in removing PM.MethodsFor this study, 100 extracted permanent teeth were collected and divided into three groups: without suction (n = 50), suction with forceful suction (n = 25), and suction with air disinfection machines (n = 25). The removal rate of suspended aerosol particles was analyzed using particle counters and air data multimeter.ResultsWhen drilling and grinding were performed without vacuum, 0.75% of the aerosol particles generated were PM2.5-10, 78.25% of total suspended aerosol particles (TSP) were PM2.5, and 98.68% of TSP were PM1. The nanoanalyzer measurements revealed that the aerodynamic diameter of most aerosol particles was below 60 nm, with an average particle diameter of 52.61 nm and an average concentration of 2.6*1011 ultrafine aerosol particles. The air change per hour (ACH) was significantly lower in the air disinfection machines group compared to the forceful suction group. Additionally, the number of aerosol particles and mass concentration was significantly lower in the air disinfection machines group compared to the forceful suction group in terms of PM2.5 levels. However, the forceful suction group also reduced the mass concentration in PM10 level than the air disinfection machines group.ConclusionIn conclusion, the air exchange system can reduce the aerosol particles generated during drilling and grinding. Comparing the two air exchange systems, it was found that the air disinfection machines group reduces the number of aerosol particles and mass concentration in PM2.5 levels, while the forceful suction group reduces the mass concentration in PM10 level.

Soft Ionization: Improving Indoor Air Quality

In this paper we report two applications of a subcategory of air cleaning devices based on soft ionization that do not cause molecular fragmentation. A system that includes two unipolar ionizing modules has been used to simultaneously produce positive and negative ions in the air. In one set of experiments a large chamber (28 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) was used to study the effect of ions on reducing PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.0</sub> particles produced by a research grade calibrated cigarette. The data presented in this paper were obtained using a carbon-brush-based bipolar ionizer and a MERV 10 filter with electret media in a recirculating HVAC system. Significant improvement in removal rate of fine and ultrafine particles was achieved when using the bipolar ionizer in conjunction with the MERV 10 filter. The second set of experiments were conducted using a 36 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> chamber, following BSL-3 standards, to study the effect of ions on aerosolized SARS-CoV-2. Results of these investigations reveal the inactivation rate of SARS-CoV-2 are enhanced when ions are introduced in the air; inactivation rates were increased by more than 60% and 90% for ion densities of 10,000/cc and 18,000/cc.

Silver nanoparticles/graphene oxide arranged on polytetrafluoroethylene substrate hydrophilic modified with TiO2 to construct efficient air purification material

Recently, the harsh air environment caused by disasters and human activities poses a great challenge to the development of efficient and antibacterial air purification systems to protect human health. In this work, a new type of high-efficiency polytetrafluoroethylene (PTFE) air filter was successfully prepared by employing silver nanoparticles decorated with graphene oxide (Ag NPs/GO) functional materials that deposited in PTFE substrate membranes hydrophilic modified with TiO2 for the improvement of the enclosed space air quality. The results revealed that the introduction of TiO2 can improve the interfacial adhesion between PTFE membrane and functional materials, improving the feasibility of long-term application of composite membrane. The composite membrane possessed the crisscross network structure interconnected by fibrils, which gives the membrane high-efficiency particulate matters (PMs) removal rate (99.25% for PM2.5) without sacrificing the pressure drop (90.52 Pa). Moreover, the prepared composite membrane also has more excellent antibacterial performance (98.7% for Escherichia coli (E. coli)), which can reduce the secondary pollution caused by improper post-treatment of the polluted filter in practical applications. After simple cleaning and regeneration, the composite membrane can still maintain an ultra-high particle removal rate (over 95%) after 5 cycles. The prepared efficiency air filtration composite membranes have positive potential applications in air purification.

Design of an Automatic Ground Cleaning Machine for Dedusting Rooms of Chicken Houses

In this paper, we designed an automatic ground cleaning machine for the dedusting rooms of chicken houses to replace the manual daily cleaning of dust particles and fluff. The machine mainly comprised a power system, control system, frame and walking structure, ground cleaning system, and dedusting system. The automatic movement of the machine body in two vertical directions without turning, lifting, and lowering of the sweeper; the retraction and expansion of the sweeper support arm; the reciprocating movement of the sweeper relative to the machine body; and the timely separation of the dust particles and fluff from gas mixtures were achieved. Parameter optimization experiments on the machine were performed using a quadratic general rotary combination design considering the movement speed, rotation speed of the sweeper, and distance between the suction head nozzle and ground as experimental factors. The regression equations describing the relationship between the three experimental factors and the dust particle removal rate and fluff removal rate were obtained using Design-Expert 12 software, adequately reflecting the impact of the three experimental factors on the two experimental indexes. Further parameter optimization was conducted to obtain the optimized parameter combination at the same weight as the two experimental indexes: movement speed of 0.1 m/s, rotation speed of the sweeper of 198 r/min, and distance between the suction head nozzle and ground of 12 mm. The performance experiment on the machine was conducted using the optimized parameter combination, yielding a dust particle removal rate of 90.7% and fluff removal rate of 91.7%. The experimental results show that the machine exhibits good performance and stable operation, meeting the daily cleaning needs of large-, medium-, and small-scale rectangular dedusting rooms of chicken houses.

Effect of Oxyfluorination of PFA-Coated Metal Mesh with Superhydrophobic Properties on the Filtration Performance of SiO2 Microparticles

Recently, semiconductor wastewater treatment has received much attention due to the emergence of environmental issues. Acid-resistant coatings are essential for metal prefilters used in semiconductor wastewater treatment. Perfluoroalkoxy alkane is mainly used as an acid-resistant coating agent, since PFA has inherent superhydrophobicity, water permeability is lowered. To solve this problem, the surface of the PFA-coated metal mesh was treated via an oxyfluorination method in which an injected mixed gas of fluorine and oxygen reacted with the surface functional groups. Surface analysis, water contact angle measurement, and water permeability tests were performed on the surface-treated PFA-coated mesh. Consequently, the superhydrophobic surface was effectively converted to a hydrophobic surface as the PFA coating layer was surface-modified with C-O-OH functional groups via the oxyfluorination reaction. As a result of using simulation solutions that float silica particles of various sizes, the permeability and particle removal rate of the surface-modified PFA-coated stainless-steel mesh were improved compared to those before surface modification. Therefore, the oxyfluorination treatment used in this study was suitable for improving the filtration performance of SiO2 microparticles in the PFA-coated stainless-steel mesh.

Using Forward and Backward Particle Tracking Approaches to Analyze Impacts of a Water Intake on Ichthyoplankton Mortality in the Appomattox River

Municipal intakes of surface water have various uses, and their impacts on the aquatic environment and ecosystem, such as the impingement and entrainment of ichthyoplankton, are a major concern. A robust assessment of the intake impacts on ichthyoplankton in a system generally requires modeling efforts that can simulate the transport and dispersal pathways of the ichthyoplankton. However, it is challenging to simulate hydrodynamics with a high-resolution grid at the scale needed for intake screen sizes in a large system. In this study, a 3D unstructured grid model with a fine resolution grid (&lt;1 m) was developed to investigate potential impacts of an intake on aquatic resources in a tidal freshwater estuary. This approach enables us to directly estimate intake-induced mortality. With the use of the coupled particle-tracking model, we evaluated the total and maximum daily removal rates of particles by the intake that can be used to estimate percent mortality of ichthyoplankton. We further investigated how impacts from the intake vary with spawning locations, flow conditions, and vertical migration velocity of ichthyoplankton. A risk assessment was conducted based on designed flow of water withdrawals. This approach is widely applicable and can address impacts of water intakes in other systems.

Effect of low-cost recirculating portable air filtration on aerosol particle deposition and concentration in a conference room: Experiment, theory, and simulation comparison

Respiratory particles exhaled when an individual speaks and breathes can facilitate respiratory virus transmission. Portable air purification units can potentially reduce transmission risk by decreasing the overall infectious particle concentration in a room. This is particularly important for rooms with an inability to be ventilated with adequate amounts of filtered or outdoor air. While the efficacy of portable air filtration units on particle concentrations has been well-studied, the impact of portable air purification units on particle deposition and, hence, indirect aerosol transmission, has received lesser study but may be important for smaller spaces with greater surface area-to-volume ratios. We conducted a series of experiments in a simulated, small conference room (34.4 m3, mimicking a common office meeting room) assessing (1) particle removal rates and (2) changes in deposition rate owing to the presence of a low-cost box fan air purifier (BFAP). To mimic an infectious aerosol source, a breathing simulator manikin was utilized in these experiments, which ejected fluorescein tagged particles in the 1–3 μm size range throughout each experimental condition, with a prescribed, periodic, breathing waveform mimicking human exhalation. We measured deposition flux on upward- and downward-facing horizontal surfaces throughout the room and determined aerosol mass concentrations using impingers; combined, these data enabled estimates of surface-specific deposition velocities. Aerosol size distributions within the room were also quantified using an optical particle spectrometer. CFD simulations and theoretical calculations were simultaneously conducted for comparison to the experimental data. Results suggested the BFAP unit, which had an effective clean air delivery rate of 540 m3 h−1, increased the effective air exchange rate by 4.4x over baseline (20.1 vs. 4.5 h−1). Notably, BFAP unit operation introduced greater deposition to surfaces near the breathing simulator manikin vs. baseline, with deposition velocities within 2 m of the breathing simulator being 100 cm s−1 during BFAP operation, compared to 10−2 cm s−1 during baseline. Deposition velocities and air exchange rates generated from the CFD and theoretical calculations largely agreed with those derived from experiments. Taken together, data suggest that in smaller rooms, such as conference rooms, deposition is not negligible as a mechanism of aerosol clearance, even for particles near 1–3 μm in diameter.

Preparation of the Nanodiamond@SiO2 Abrasive and its Effect on the Polishing Performance of Zirconia Ceramics

For the purpose of achieving the industrial requirement of efficient and high precision polishing of zirconia ceramics, nanodiamond@SiO2 abrasives were synthesized by a simple method using tetraethyl orthosilicate (TEOS) as raw materials. As observed in the transmission electron microscopy results, the composite abrasives showed a homogeneous and dense silica coating layer. It was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction spectroscopy that the composite abrasives have a core–shell structure with a diamond core and a silica shell. According to the Zeta potential analysis, the dispersion stability of composite particles was improved compared to that of the pure nanodiamond particles. The chemical mechanical polishing (CMP) experimental results show that the polishing performances of composite abrasives on zirconia ceramics are better than that of the pure nanodiamond abrasives. The material removal rate of the composite particles is 2.184 μm h−1, and the surface roughness of the polished zirconia ceramics is 1.055 nm, which was 140% higher and 89% lower than that of pure nanodiamond abrasives, respectively. Furthermore, the polishing mechanism was explored by X-ray photoelectron spectroscopy (XPS), friction coefficient meter and dynamic contact angle test.

Investigating the Effectiveness of Vortex-Enhanced Particle Settling in a Hydraulic Separator Using Physical Modeling

Often it is implied that hydraulic particle separators that incorporate vortex technology provide enhanced particle settling. In this study, a generic vortex particle separator was closely examined using physical modeling to help understand typical flow hydraulic conditions. The study was conducted using particle capture analyses under different internal structure configurations, inflow rates, and inlet pipe configurations to examine how resulting changes to flow conditions influenced the settling of particles. The purpose of this study was not to evaluate performance or obtain absolute particle removal rates of a particular particle separator design; instead, the focus was on understanding how modifications to the flow conditions in the examined separator could affect the particle-settling efficiency. The comparison results show that the inflow-generated large internal vortex does not effectively improve particle settling; possible explanations are given based on hydraulics and physics principles. The study method and results can be extended to examine and improve other hydraulic particle separators.

Effect of different setups, protective screens and air supply systems on the exposure to aerosols in a mock-up restaurant

Social distancing measures to lower the risk of SARS-CoV-2 transmission limit seating capacity in and constrain restaurants’ ability to operate in an economically sustainable way. Experiments have been conducted in a real-size mock-up of a restaurant, using different table setting and configurations of the ventilation system. The study has analysed the effects on total exposure to aerosols in different settings compared with social distancing. Ventilation rate is the most decisive factor for the total exposure. The particle removal rate is directly proportional to the ventilation rate, while total exposure decreases with higher ventilation rates. At low ventilation rate, setups with protective screens perform comparably or somewhat superior to the social distancing configuration, but effect size is much smaller than for ventilation rate and results are not always significant. Air supply system type does not have significant effect on either total exposure or exposure duration.