Plasma Chemistry and Plasma Processing最新文献

The conversion of atmospheric nitrogen into nitrogen fertilizer has gained much attention owing to the increasing demand for food given the growth of the world’s population. The gliding arc plasma exhibited great potential in this area and constitutes a green alternative to the conventional Haber–Bosch process of nitrogen fixation by mitigating carbon footprints. The moist air gliding arc plasma treatment has been reported to be effective for the production of nitrogen species for agricultural applications. However, the amount of nitrogen species in the treated water rapidly reached a maximum value within a short time and then no longer increased. Thus, this work proposed an innovative approach to allow nitrate production to continually increase by incorporating a natural harmless dolomite mineral. Interestingly, the results demonstrated a significant effect of dolomite on increasing the nitrate concentration from 115.76 ± 3.15 to 263.19 ± 4.31 mg/L. The effects of operating parameters such as the nature of the feeding gas, the flow rate, the dolomite dosage, and the temperature were investigated. The optimal conditions were established as follows: flow rate, 800 L/h; dolomite dose, 2 g/L; temperature, 45 °C; and moist air gas. Under these conditions, the nitrite and nitrate concentrations reached 16.09 ± 0.50 mg/L and 294.73 ± 5.14 mg/L, respectively, within 60 min of aging. The mechanism of nitrate production was investigated, revealing that the plasma-generated acid species catalyzed dolomite dissolution, releasing Ca²⁺ and Mg²⁺ ions. In turn, these species react simultaneously with the produced nitrate ions to form double salts of Ca(NO₃)₂ and Mg(NO₃)₂, which serve as reservoirs to promote their accumulation. This study demonstrated substantial nitrate production improvement in distilled water via the use of moist air gliding arc plasma and offered a promising green alternative for nitrogen-based fertilizer production.

Numerical modeling of atmospheric pressure current-carrying argon plasma containing a single spherical metal particle was performed. The plasma is described in the hydrodynamic approach with account for its thermal and ionization non-equilibrium near the particle. Spatial distributions of electric current, electric potential, and electron flux around a single particle were calculated. The electric current flowing through the particle in the plasma was determined and compared with the model of the highly conducting particle in the uniform conducting media. The surface distribution and total heat flux density from plasma to the particle were studied. The range 10⁻⁵–10⁻⁴ m of particle radius and the range (0.5–2)×10⁷ A/m² of current density in unperturbed plasma, corresponding to the conditions of plasma transferred arc surfacing and plasma powder spheroidization, were considered. The electron temperature was assumed to be constant.

Dielectric barrier discharge plasma has been shown as an effective alternative in renewable NH₃ production, however a catalyst which enhances the process to commercial potential is still being sought. This work investigates three catalysts, CaH₂, Ca₃N₂, and LiH for NH₃ synthesis when subjected to plasma. This work found a maximum synthesis rate of 6440 µmol h^− 1 g_cat⁻¹ for CaH₂ and an efficiency of 4.0 g-NH₃ kWh^− 1 g_cat⁻¹. Varying flow ratios to determine effects on synthesis demonstrated CaH₂ and LiH preferred hydrogen rich environments while Ca₃N₂ performed best in nitrogen rich flows. These results suggest each of the tested catalysts could have different reaction pathways or dependencies. Gas chromatography was used to quantify production levels and optical emission spectroscopy was used to determine vibrational temperatures of molecular nitrogen. These findings introduce three catalysts for use in plasma-based NH₃ synthesis and characterize the potential for increased efficiency of ammonia production.

The Ag₂O/CuO nanoshuttles stacked with nanosheets were fabricated in CH₃COONa solution via direct current (DC) diaphragm discharge plasma technique, in which a silver-copper (Ag-Cu) alloy sheet was used as anode, and a graphite rod inserted into a quartz glass tube with a small hole on the sidewall was acted as cathode. The preparation mechanism of Ag₂O/CuO was discussed in detail. The performance of Ag₂O/CuO nanoshuttles as electrode material was assessed for sensing glucose. The results showed that Ag₂O/CuO electrode exhibits a low limit of detection of 0.35 µM, high sensitivity of 1001.2 µA mM^− 1 cm^− 2, wide linear range of 0.01–7.2 mM, and fast response time of only 0.4 s. In addition, Ag₂O/CuO has high selectivity, high stability and good repeatability. The glucose in human saliva is determined using Ag₂O/CuO modified electrode, the recovery is 101.1%~103.2%, and the relative standard deviations (RSDs) are below 5%. All results indicated that Ag₂O/CuO prepared by diaphragm discharge plasma can be regarded as an alternative electrode material for the glucose sensing. Compared with other synthesis methods, diaphragm discharge is a simple, effective, and green technique without expensive platinum, metal salts, alkali sources, and high temperature.

Graphical Abstract

Ag₂O/CuO nanoshuttles were fabricated via direct current diaphragm discharge plasma technique, and then regarded as an electrode material for sensing glucose

A novel method for generating high-temperature gas using a tandem-type inductively coupled thermal plasma (Tandem-ICTP), composed of two vertically arranged coils, was proposed to experimentally evaluate the dielectric properties of hot gases. The dielectric properties of high-temperature insulation gases are critical for determining the success or failure of current interruption in gas circuit breakers (GCBs). In this study, we focused on the detailed investigation of the high-temperature gas field generated by Tandem-ICTP. The temperature of (hbox {CO}_2) gas, heated by varying the lower-coil input power in the Tandem-ICTP system, was estimated using spectroscopic measurements at the electrode position, applying the Boltzmann plot method. Additionally, an electromagnetic thermofluid simulation was conducted to support the experimentally measured temperatures and to estimate the mole concentration of (hbox {CO}_2) gas between the electrodes. The results revealed that the temperature of the (hbox {CO}_2) gas could exceed 3800 K using the Tandem-ICTP and could be adjusted by approximately 2600 K by modifying the input power of lower-coil. Furthermore, the mole concentration of high-temperature (hbox {CO}_2) gas between the electrodes was found to be approximately 40(%), as determined by numerical simulation. This method demonstrates that a dielectric test can be conducted in the wide range of high-temperature gas fields above 3000 K by controlling parameters such as the input power of lower-coil in the Tandem-ICTP system.

Cold atmospheric direct plasma (CADP), an ionized gas at ambient temperature, represents a promising approach to enhancing tissue regeneration. A laboratory-based study was conducted to investigate the effects of medical CADP on the reparative potential of full-thickness acute skin wounds in murine models. For the in vivo investigations, two full-thickness dermal injuries were induced in each murine subject, each with a diameter of approximately 8 mm (n = 20). We employed a floating electrode within a CADP system that generates atmospheric pressure air plasma, characterized by a plasma temperature ranging from 36 to 38 °C. The dermal wounds received three plasma treatments, administered every two days, with irradiation durations of 5, 15, and 25 s. These wounds were subsequently evaluated at intervals of 2, 4, 6, 8, and 11 days post-wounding through histological examination and concentration analysis of growth factors. On the eleventh day, the wound healing rates were recorded at 34.80% for the control group, while the plasma-treated groups achieved rates of 56.62%, 84.97%, and 97.82%, respectively. Histological examination revealed that plasma-treatment promotes the development of epidermal keratin and granular strata, along with the formation of hair follicles and sebaceous glands. Concentration analysis of growth factors indicates increased levels of these factors alongside a reduction in white blood cell counts. The CADP therapeutic intervention has significantly enhanced the healing efficacy of acute dermatological lesions without any noticeable adverse effects or the simultaneous activation of pro-inflammatory signaling pathways. These findings highlight the advantages of employing plasma applications for wound management in clinical settings.

A co-axial packed-bed DBD reactor was used to conduct plasma-assisted non-oxidative coupling of methane (NOCM) utilizing glass beads as packing material at a fixed plasma power of 30 W. The influence on NOCM of five different bead size distributions (2000–5000 µm, 900–1100 µm, 425–600 µm, 212–300 µm, 150–212 µm) and operating pressure (1.2 bar, 1.7 bar) was investigated. The observed products consist of a mixture of saturated and unsaturated C₂–C₅ hydrocarbons. The conversion of methane decreased from 8.5 to 3.7% with decreasing bead size, while the selectivity towards unsaturated C₂ compounds increased from 16 to 50% with decreasing bead size. These reactor performance variations are associated with the transitional plasma dynamics and degree of partial discharging, as determined by characterization of non-ideal charge–voltage plots for the five tested glass bead sizes.

Oral cancer presents significant challenges with available treatment options; therefore, innovative treatment strategies are urgently needed. Nonthermal atmospheric pressure plasma (NAPP) is well known to be effective against various cancers. However, the effect and underlying mechanism of NAPP on YD-10B oral cancer cells are widely unknown. We have selected the oral cancer YD-10B cell line because the effect of NAPP on this particular cell line has not been investigated before. This study explored the therapeutic potential of NAPP via both direct and indirect NAPP treatments and their underlying mechanism on YD-10B cells for the first time. The viability of the oral normal HGF cells remained unchanged while significantly decreased in YD-10B cells using direct and indirect NAPP treatments. Direct treatment significantly increased intracellular reactive oxygen and nitrogen species (ROS/RNS), while indirect treatment mainly elevated RNS levels, with a modest but significant ROS increase in the NO-PAW15. The DNA damage and apoptosis markers are significantly upregulated in both direct and indirect treatments in YD-10B cells, though the expression levels are different. The western blot analysis confirms that both NAPP treatments (direct/indirect) are effectively inducing apoptosis in YD-10B cells. Furthermore, the utilization of N-Acetyl Cysteine and cPTIO as inhibitors confirms that the ROS/RNS are mainly responsible for inducing DNA damage and promoting apoptosis. Interestingly, both NAPP treatments are effective and follow the same molecular pathways to induce apoptosis. This study presents a promising avenue for the development of novel and targeted oral cancer treatments, with molecular insights providing valuable guidance for future investigations in the field.

Using the Langmuir probe method, the spatial distributions of plasma parameters (plasma potential, electron number density and mean electron energy) in a discharge supported by a rectangular hollow cathode in helium at reduced pressure were studied. Measurements were carried out both inside the geometric aperture between the cathode and the anode, and outside it, including the region behind the anode. In the experiments, different anode designs were used: a rectangular metal grid and a grid with an adjacent solid metal or dielectric plate. It is shown that there is a noticeable number density of electrons in the region behind the anode, and the highest is observed in the case of a grid anode. Using the electric field component E_x(х), measured along the central axis X of the discharge gap for the case of grid anode, electron number density profile N_e(x) was calculated within the 1D Monte Carlo model. In the cathode-anode gap, the calculation results agree satisfactorily with the experimental data, but behind the anode, they are significantly lower than those measured. This difference is explained by the fact that under experimental conditions some of the electrons enter this region not by flying through the grid anode, but by flying around it.