Plasma sterilization technologies have been the subject of several studies and remarkable developments over the last few years. Ozone (O 3 ) is an effective sterilizer, and its range of applications ...has extended to include water purification. Ozone is typically generated from oxygen (O 2 ) in nonthermal plasma (NTP). However, this process requires the use of an additional gas cylinder or supply device for O 2 , thereby entailing increased costs of operation and energy consumption. Air can be used as an alternative to O 2 as a source gas for O 3 production. However, this leads to the generation of nitrogen oxide (NO x ), an air pollutant, during plasma discharge. Hence, it is vital to develop a method for O 3 generation that addresses the challenges of energy costs and emission of air pollutants. This study, therefore, proposes an energy-efficient NTP sterilization system. The system is based on electrolysis of water to produce O 2 and hydrogen (H 2 ). The O 2 produced is used to generate O 3 for sterilization, and H 2 is used in fuel cells to generate electric power. The present study details the characteristics of energy consumption and efficiency in O 3 production and elucidates the proposed NTP sterilization system. Reduction in energy consumption for O 3 production is achieved with a power recovery rate of more than 11.1% in the present high-efficiency water sterilization system.
Superlubricity of tetrahedral amorphous carbon (ta-C) coatings under boundary lubrication with organic friction modifiers is important for industrial applications, but the underlying mechanisms ...remain elusive. Here, combined experiments and simulations unveil a universal tribochemical mechanism leading to superlubricity of ta-C/ta-C tribopairs. Pin-on-disc sliding experiments show that ultra- and superlow friction with negligible wear can be achieved by lubrication with unsaturated fatty acids or glycerol, but not with saturated fatty acids and hydrocarbons. Atomistic simulations reveal that, due to the simultaneous presence of two reactive centers (carboxylic group and C=C double bond), unsaturated fatty acids can concurrently chemisorb on both ta-C surfaces and bridge the tribogap. Sliding-induced mechanical strain triggers a cascade of molecular fragmentation reactions releasing passivating hydroxyl, keto, epoxy, hydrogen and olefinic groups. Similarly, glycerol's three hydroxyl groups react simultaneously with both ta-C surfaces, causing the molecule's complete mechano-chemical fragmentation and formation of aromatic passivation layers with superlow friction.
Large-scale quantum molecular dynamics of water-lubricated diamond (111) surfaces in sliding contact reveals multiple friction regimes. While water starvation causes amorphization of the tribological ...interface, small H_{2}O traces are sufficient to preserve crystallinity. This can result in high friction due to cold welding via ether groups or in ultralow friction due to aromatic surface passivation triggered by tribo-induced Pandey reconstruction. At higher water coverage, Grotthuss-type diffusion and H_{2}O dissociation yield dense H/OH surface passivation leading to another ultralow friction regime.
Air pollution caused by particulate matter (PM) is a worldwide concern. PM is particularly problematic from fossil-fuel-based energy conversion devices. For PM collection, a low-pressure loss method ...is ideal. Although PM collection via electrostatic force is an effective method with low pressure loss for PM with a wide range of diameters, it is difficult to apply to low-resistive PM, such as diesel particulates, owing to re-entrainment on the collection electrode. A magnetic fluid filter with an AC non-thermal plasma discharge solves the problem of re-entrainment. Based on our previous study, we hypothesized that an increase in the number of magnetic fluid spikes leads to an improvement in collection efficiencies with energy conservation. In this study, experiments are performed to verify this hypothesis. By improving our previous experimental methodology, the experiments include not only collection efficiency but also pressure loss, power consumption, and ozone generation efficiency. PM collection efficiencies using diesel fine particles and the ozone generation efficiencies required for air purification are investigated under different discharge conditions. The results revealed that the PM collection and ozone generation efficiencies increase proportionally with the number of spikes of the magnetic fluid with discharge, as hypothesized. The resulting PM collection and ozone generation efficiencies are sufficiently high for air purification.
Hydration states are a crucial factor that affect the self-assembly and properties of soft materials and biomolecules. Although previous experiments have revealed that the hydration state strongly ...depends on the chemical structure of lipid molecules, the mechanisms at the molecular level remain unknown. Classical and density-functional tight-binding (DFTB) molecular dynamics (MD) simulations are employed to determine the mechanisms underlying dissimilar water dynamics between lipid membranes with phosphatidylcholine (PC) and phosphatidylethanolamine (PE) head groups. The classical MD simulation shows that rotational relaxations of water are faster on the PE lipid than on the PC lipid, which is consistent with a previous experimental study using terahertz spectroscopy. Furthermore, DFTB-MD simulation of N(CH3)4 + and NH4 + ions, which correspond to the different head groups in PC and PE, respectively, shows qualitative agreement with the classical MD simulation. Remarkably, the PE lipids and the NH4 + ions break hydrogen bonds between water molecules in the secondary hydration shell. In contrast, the PC lipids and the N(CH3)4 + ions bind water molecules weakly in both the primary and secondary hydration shells and increase hydrogen bonds between water. Our atomistic simulations show that these changes in the hydrogen-bond network of water molecules cause the different rotational relaxation of water molecules between the two lipids.
Abstract
Friction and wear reduction by diamond-like carbon (DLC) in automotive applications can be affected by zinc-dialkyldithiophosphate (ZDDP), which is widely used in engine oils. Our ...experiments show that DLC’s tribological behaviour in ZDDP-additivated oils can be optimised by tailoring its stiffness, surface nano-topography and hydrogen content. An optimal combination of ultralow friction and negligible wear is achieved using hydrogen-free tetrahedral amorphous carbon (ta-C) with moderate hardness. Softer coatings exhibit similarly low wear and thin ZDDP-derived patchy tribofilms but higher friction. Conversely, harder ta-Cs undergo severe wear and sub-surface sulphur contamination. Contact-mechanics and quantum-chemical simulations reveal that shear combined with the high local contact pressure caused by the contact stiffness and average surface slope of hard ta-Cs favour ZDDP fragmentation and sulphur release. In absence of hydrogen, this is followed by local surface cold welding and sub-surface mechanical mixing of sulphur resulting in a decrease of yield stress and wear.
An effective NO x -reduction aftertreatment system for a marine diesel engine that employs combined nonthermal plasma (NTP) and adsorption is investigated. The system can also treat particulate ...matter (PM) that employs a diesel particulate filter (DPF) and its regeneration by NTP-induced ozone. The effect of the combined reduction of accumulated PM and NO x is studied. The marine diesel engine of interest provides an output power of 1 MW at 100% of the engine load. The NO x reduction is composed of repeated adsorption and desorption flow processes using NTP combined with NO x adsorbents. With a view toward practical use, experiments on a higher number of cycles are carried out. The amount of adsorbents is 105 kg, which is greater than that in the authors' previous study. As a result, NO x reduction efficiency by NTP is higher than in the previous study and is greater at higher amounts of adsorbents owing to higher NO x desorption. Furthermore, DPF regeneration with plasma-induced O 3 injection is achieved simultaneously. This aftertreatment system demonstrates an excellent energy efficiency of 114 g(NO 2 )/kWh. The present aftertreatment can generate a synergistic effect of PM and NO x reduction.
We applied our original chemical mechanical polishing (CMP) simulator based on the tight-binding quantum chemical molecular dynamics (TB-QCMD) method to clarify the atomistic mechanism of CMP ...processes on a Cu(111) surface polished with a SiO2 abrasive grain in aqueous H2O2. We reveal that the oxidation of the Cu(111) surface mechanically induced at the friction interface is a key process in CMP. In aqueous H2O2, in the first step, OH groups and O atoms adsorbed on a nascent Cu surface are generated by the chemical reactions of H2O2 molecules. In the second step, at the friction interface between the Cu surface and the abrasive grain, the surface-adsorbed O atom intrudes into the Cu bulk and dissociates the Cu–Cu bonds. The dissociation of the Cu–Cu back-bonds raises a Cu atom from the surface that is mechanically sheared by the abrasive grain. In the third step, the raised Cu atom bound to the surface-adsorbed OH groups is removed from the surface by the generation and desorption of a Cu(OH)2 molecule. In contrast, in pure water, there are no geometrical changes in the Cu surface because the H2O molecules do not react with the Cu surface, and the abrasive grain slides smoothly on the planar Cu surface. The comparison between the CMP simulations in aqueous H2O2 and pure water indicates that the intrusion of a surface-adsorbed O atom into the Cu bulk is the most important process for the efficient polishing of the Cu surface because it induces the dissociation of the Cu–Cu bonds and generates raised Cu atoms that are sheared off by the abrasive grain. Furthermore, density functional theory calculations show that the intrusion of the surface-adsorbed O atoms into the Cu bulk has a high activation energy of 28.2 kcal/mol, which is difficult to overcome at 300 K. Thus, we suggest that the intrusion of surface-adsorbed O atoms into the Cu bulk induced by abrasive grains at the friction interface is a rate-determining step in the Cu CMP process.
We investigate the removal of air pollutants containing nanoparticles with a wet-type plasma reactor that generates a gas-liquid interfacial nonthermal plasma. To evaluate the performance of this ...reactor, we prepare a simulated exhaust gas using polystyrene latex particles, as well as gas cylinders of synthesized air and mixed gas of nitric oxide (NO) and sulfur dioxide (SO2). We achieve a partial collection efficiency of more than 99% for nanoparticles. Moreover, we obtain removal efficiencies exceeding 99% and 81% for SO2 and NOx, respectively. We confirm that the proposed reactor is useful for the simultaneous removal of nanoparticles, NOx, and SOx.
•A wet-type plasma reactor is useful for air pollutants containing nanoparticles.•A collection efficiency of more than 99% is achieved for nanoparticles.•Removal efficiencies of 99% and 81% are obtained for SO2 and NOx, respectively.•A wet-type plasma reactor can achieve the removal of nanoparticles, NOx and SOx.
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