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The effect of CO2 addition on the ethane conversion reaction under the combined action of plasma and 10% CeO2/Y-Al2O3

The effect of CO2 addition on the ethane conversion reaction under the combined action of plasma and 10% CeO2/Y-Al2O3

The effect of CO2 addition on the ethane conversion reaction under the combined action of plasma and 10% CeO2/Y-Al2O3: It can be seen that the conversion rate of CO2 decreases with the increase of CO2 addition, but it is higher than the conversion rate of pure CO2 under the same plasma conditions, which indicates that C2H6 contributes to the conversion of CO2. According to the reaction equations (3-40) and (3-41), the decomposition rate of CO2 is related to the concentrations of CO2, CO, O- and O in the plasma catalytic system. O and O- are consumed by the reaction with H, and H is determined by C2H6 decomposition reaction generated. Therefore, the conversion rate of CO2 increases with the increase of C2H6 concentration. It can be seen that the selectivity of C2H4 and C2H2 decreases monotonically with the increase of CO2 and the addition amount, so although the conversion rate of ethane increases with the increase of CO2 addition, the total yield of C2H4 and C2H2 changes in a peak shape, and the addition amount of CO2 is The extreme value occurs at 50%. On the other hand, reactive oxygen species will further react with ethylene or acetylene, resulting in the cleavage of its C-H bond to form CO or carbon deposition. This phenomenon is especially obvious when the amount of CO2 added is large. Therefore, when the amount of CO2 added is greater than 50%, the total yield of C2H4 and C2H2 decreases. The change in the amount of CO2 added leads to changes in the ratio of C2H4/C2H2 and H/CO in the gaseous products of the reaction. With the increase in the amount of CO2 added, the ratio of C2H4/C2H2 increases and the ratio of H2/CO decreases. This is due to the CO yield in the reaction system. due to rapid increase.

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Plasma-formed high-pressure shock wave technology is used in titanium and aluminum alloys in the aerospace industry

Plasma-formed high-pressure shock wave technology is used in titanium and aluminum alloys in the aerospace industry

Plasma-formed high-pressure shock wave technology is used in titanium and aluminum alloys in the aerospace industry: Shock strengthening (LSP), also known as shot peening, is a new type of surface strengthening technology that uses high power density and short pulses to irradiate the surface of materials. A surface absorbing layer (coating layer) on the surface of a material. Explosive vaporization occurs by absorbing energy, and the vaporization produces high-pressure plasma. When the plasma is bound by the confinement layer and explodes, a high-pressure shock wave acts on the metal surface and propagates inside. When the dense and stable dislocation structure is formed on the surface of the material, the surface layer of the material is strain hardened, and a large compressive stress remains, which significantly improves the fatigue resistance and stress corrosion resistance of the material. The impact pressure model induced on the surface of the material, the nanometerization of the surface layer of the impact-induced material, and the impact-induced plasma strengthening technology are applied to the application of titanium alloys and aluminum alloys in the aviation industry. The surface of the polished target is usually coated with a layer of coating (also called sacrificial layer, usually organic black paint, tape or thin metal foils such as lead, zinc, and aluminum). A high peak power density, short pulsed beam is used to focus the beam through a focusing lens into a millimeter-scale spot and then irradiate it through a transparent confinement layer (usually water or glass) onto the coating surface. The coating fully absorbs high-energy energy, and explosive vaporization occurs in a very short time. The vapor continues to absorb energy to generate a high-pressure plasma layer. The latter's outward ejection is bound by the confinement layer to generate a high-pressure shock wave, which generates a strong stress wave that propagates from the surface of the target to the interior. When the pressure peak of the stress wave exceeds the elastic limit of the material for a certain period of time, a dense and stable dislocation structure will be formed on the surface of the material, and microscopic defects such as twins may also be generated, and the surface of the material will be strain hardened. The existence of residual compressive stress will change the stress field distribution on the surface of the structure and improve the fatigue strength of the material. Under the combined action of these two factors, the properties of the material such as fatigue resistance and stress corrosion resistance are significantly improved after plasma strengthening. The microstructure of the material directly affects the surface properties of the material. Grain size is one of the important factors affecting the structural properties of materials. As the grain size of the material surface decreases, the strength, plasticity and wear resistance of the material also increase. Studies have shown that grain refinement and even nanometerization on the surface of materials can improve the ability of materials to resist fatigue, wear and corrosion. Plasma produces strong dislocations and grain refinement in the material, so that under certain conditions, it is possible to realize nanometerization of the surface of the material. Achieving grain refinement is beneficial to improve the surface properties of titanium alloys and thus improve the overall performance of the entire component. The high-pressure shock wave formed by the plasma is introduced into the workpiece to cause plastic deformation of the workpiece under the force effect of the shock wave. The beam is used as a loading tool, and the parameters such as pulse energy, spot size and pulse interval width are controllable. The relative motion trajectory of the impact head and the workpiece is controlled by the numerical control system, which can realize the local forming of the workpiece with a single impact and optimize the plasma parameters. The workpiece is impacted at multiple points and multiple times, so as to realize the flexible stamping and forming of the workpiece.

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Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction

Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction

Under the action of plasma plasma, CH4 and CO2 are the raw material gas to synthesize C2 hydrocarbon reforming reaction: Synthesis of C2 hydrocarbons with CH4 and CO2 as feed gas is a very interesting reaction. The first complete reduction product of CO2 hydrogenation is CH4, and the partial reduction product is C2 hydrocarbon; secondly, the complete oxidation product of CH4 is CO2, the partial oxidation product is C2 hydrocarbon, and the intermediate product is CHx. Obviously, these two reactions are mutually reversible. , such as co-activation of CH4 and CO2, that is, the presence of CO2 will be beneficial to the partial oxidation of CH4, and the presence of CH4 will inhibit the deep reduction of CO2, the result of the joint action will be conducive to the formation of C2 hydrocarbons. The significance of studying the CH4 coupling reaction with CO2 as the oxidant is that: first, a method to solve the difficult activation of CH4 is proposed, which provides an effective way to make full use of natural gas: Secondly, the conversion and utilization of CO2 can reduce greenhouse gases to a certain extent. emission. Therefore, this research has important academic value and broad application prospects. The synthesis route of CO2 oxidation of CH4 to C2 hydrocarbons has been reported. Under the action of plasma plasma, CO2 oxidation of CH4 to C2 hydrocarbons can be divided into indirect method and direct method. Synthetic system of C2 hydrocarbons. Zhou et al. used the dielectric barrier discharge method to realize the CO2 reforming CH4 reaction. When the injection energy was 87kW.h/(N∙m3), the conversion rate of methane was 64%, and the conversion rate of carbon dioxide was 54%. Gallon et al. and Pinhao et al. respectively investigated the reforming reaction of CH4 and CO2 under the action of DBD discharge plasma, and the results showed that the main product of the reforming reaction was syngas, and only a small amount of hydrocarbons (mainly C2H6) were generated. However, under the action of DBD discharge plasma, the reactant conversion of CH4 and CO2 reforming reaction is relatively low and the reaction energy consumption is high. Li et al. investigated the reforming reaction of CH4 and CO2 under the action of DC and AC corona discharge respectively. The experimental results show that the reformation reaction of CH4 and CO2 under the action of corona discharge plasma can obtain higher conversion rate of reactants, H2 selectivity and CO selectivity, compared with that obtained by DC positive corona discharge. , followed by AC corona, low DC negative corona. Malik et al. and Gesser et al. realized CO2 reforming CH4 reaction under pulsed corona plasma and silent discharge plasma conditions, respectively. The direct method is to prepare C2 hydrocarbons from CH4 and CO2 in one step, and the reaction can be realized under the action of microwave, flow column discharge and radio frequency plasma. Liu uses the flow column discharge method, with He as the balance gas (accounting for 60%~80% of the total gas flow), under a certain discharge power, according to the different molar ratios of CO2 and CH4, the methane conversion rate is between 20%~80% , the conversion rate of carbon dioxide is between 8% and 49%, and the yield of C2 hydrocarbons is between 20% and 45%. Chen Dongliang et al. directly converted CH4 and CO2 under the action of microwave plasma, and produced C2 hydrocarbons in one step. The main C hydrocarbon products in the reaction were C2H2 and C2H6. The increase of plasma power is conducive to the generation of C2H2. Yao et al. used radio frequency plasma to realize the reaction of CO2 oxidation of CH to C2 hydrocarbons, the methane conversion rate was 31%, the carbon dioxide conversion rate was 24%, and the C2 hydrocarbon selectivity was 64%.

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Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research

Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research

Plasmon-enhanced InAs Single Quantum Dot Fluorescence Radiation Changes Nanoscale Size Tuning Wavelength Research: Semiconductor quantum dots are quantum structures with limited three-dimensional dimensions, which restrict the spatial distribution and motion of carriers, and thus have some unique physical properties, such as discrete energy levels, density of states similar to functions, etc. Quantum dots have good application prospects in single-photon emitting devices. After the surface plasmon treatment of metal nanostructures, it has rich and unique physical properties, which makes the optical field localized in the sub-wavelength size range, and has a strong localized electromagnetic field enhancement effect. Changing the nanometer size of metals can tune the resonant wavelength of surface plasmons. At the same time, metal nanostructures will also reduce the lifetime of fluorescence, reduce the intensity of fluorescence, or cause fluorescence quenching. When the nanostructures only resonate with the excitation light field, the fluorescence lifetime of the quantum dots remains unchanged; when the nanostructures resonate with the fluorescence of the quantum dots, the quantum yield can be improved, while the fluorescence lifetime of the quantum dots is reduced. The luminescence lifetime, luminescence intensity and saturation excitation power of the obtained quantum dots are all modulated by the gold island film. This is mainly manifested in the following three aspects: One is the enhancement of the localized laser field. The nanostructure of the gold island film allows the optical field to be localized in the sub-wavelength size, especially at some sharp corners or slits, which increases the localized strength of the electric field, which will lead to saturated excitation power. reduce; 2. The coupling between the quantum dot dipole transition and the gold island film leads to a decrease in the fluorescence lifetime, which belongs to the non-radiative recombination process of excitons. At the same time, the luminous energy is absorbed by the gold island film and lost, resulting in a decrease in the luminous intensity and an increase in the saturation excitation power; 3. The gold island film structure is used as a directional coupling-out antenna for quantum dot light emission, which increases the PL collection efficiency, resulting in a higher spectral collection efficiency, but has little effect on the saturated excitation power and fluorescence lifetime. The coupling between the gold island film and the quantum dot emission is related to the emission wavelength of the quantum dot and the specific nanostructure of the gold island film in the quantum dot sample. The metal nanostructure can change the radiation direction of the light field to form the directional emission of the light field. Therefore, metal nanostructures are widely used to study excitation light field enhancement, fluorescence emission coupling and their interaction with dipole luminescence, such as using Tam plasmon modes, nanoparticles, nanoantennas, metal films, nanostructures And plasmon resonance, etc., improve the fluorescence radiation intensity of quantum dots, form fluorescence directional emission, improve fluorescence collection efficiency, etc. Plasma enhances the fluorescence radiation of single quantum dots and improves the quality of the luminous effect of the product. The main physical mechanism of the fluorescence enhancement effect is that the gold island film structure acts as an effective directional coupling output of quantum dots, and the antenna increases the PL collection efficiency of the quantum dots, thereby obtaining a higher spectral collection efficiency. The gold island film structure mainly enhances the collection efficiency of quantum dot spectra, providing an efficient method for preparing bright single-photon sources. At the same time, it is also observed that a small number of quantum dots like QD2 have the phenomenon that the luminescence lifetime is shortened (about 270ps), the saturation excitation power is increased (about 1nW), and the total fluorescence intensity is weakened. This is because the luminescence energy is reduced by gold. The island film is absorbed and lost, and no radiation recombination plays a major role. The gold island film has a certain modulation effect on the luminescence lifetime, luminescence intensity and saturation excitation power of quantum dots. The gold island film nanostructure is beneficial to improve the collection efficiency of PL spectra of quantum dots, which provides an efficient method for fabricating bright single-photon sources.

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The vacuum plasma surface treatment equipment will not produce a damaged layer on the surface of the material after treatment

The vacuum plasma surface treatment equipment will not produce a damaged layer on the surface of the material after treatment

The vacuum plasma surface treatment equipment will not produce a damaged layer on the surface of the material after treatment: Vacuum plasma surface treatment equipment uses plasma treatment to improve the adhesion and adhesion of the material surface. By removing organic pollutants, polar organic functional groups are introduced on the surface to improve the surface hydrophilicity and surface wetting performance, which is a thorough peeling. Dry cleaning, vacuum plasma surface treatment equipment will not produce a damaged layer on the surface of the material, and the surface quality of the material is guaranteed. Plasma surface treatment uses oxygen and argon gas to generate energy. When there is enough energy to open the carbon-fluorine bond of PTFE and fluorine atoms are replaced by active groups, PTFE will become Polar polymer with enhanced surface energy and improved hydrophilicity. According to the different shapes, processing purposes and requirements of the PTFE Teflon products to be processed, there will be differences. For example, film materials are suitable for use in roll-to-roll plasma equipment; plate materials are suitable for plasma cleaning machines with horizontal or vertical electrode structures. The control of the process parameters of the vacuum plasma surface treatment equipment has an important influence on the treatment of PTFE polytetrafluoroethylene materials. Plasma surface treatment equipment includes low-pressure vacuum plasma surface treatment equipment and atmospheric plasma surface treatment equipment. The former can be fed with different process gases and a number of process parameters can be deployed, which is relatively suitable for the treatment of PTFE polytetraoxide. Plasma surface treatment equipment, also known as plasma cleaning machine, or plasma surface treatment instrument, is a brand-new high-tech technology that uses plasma to achieve results that cannot be achieved by conventional cleaning methods. Plasma is a state of matter, also known as the fourth state of matter, and does not belong to the common solid-liquid-gas three-state. When enough energy is applied to a gas to ionize it, it becomes a plasma state. The "active" components of the plasma include: ions, electrons, atoms, reactive groups, excited nuclides (metastable states), photons, etc. If a reactive gas is introduced into the discharge gas of the vacuum plasma surface treatment equipment, a complex chemical reaction will occur on the surface of the activated material, and new functional groups, such as hydrocarbon groups, amino groups, carboxyl groups, etc., will be introduced. Significantly improve the surface activity of the material. Generally, materials such as NH3, O2, CO, Ar, N2, H2 and other gas plasma treatment will be exposed to air, and groups such as -COOH will be introduced on the surface to increase their hydrophilicity.

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CH4 and CO2 reforming reaction under the combined action of DBD plasma and catalyst

CH4 and CO2 reforming reaction under the combined action of DBD plasma and catalyst

CH4 and CO2 reforming reaction under the combined action of DBD plasma and catalyst: The conversion reaction of CO2 oxidation to CH4 under the action of plasma is mainly initiated by free radicals, and the target product C2 hydrocarbon has poor selectivity. The CO2 oxidation CH4 conversion reaction under chemical catalysis has higher selectivity of the target product. For example, the target product given by the supported nickel catalyst is syngas (CO+H2); the target product using lanthanide oxides as the catalyst is a C2 hydrocarbon. In the catalytic reaction, due to the high energy required to break the C-H bond of methane and the C-O bond of CO2, the synthetic route using C2 hydrocarbons as the target product has disadvantages such as high reaction temperature and low conversion rate of CH4. Wang et al. investigated the CH4 and CO2 reforming reaction under the combined action of DBD plasma and catalyst. The results show that the synergistic effect of the two can effectively improve the conversion rate of reactants and the selectivity of target products. Some research groups have also investigated the reforming reaction of CH4 and CO2 under the conditions of sliding arc discharge combined with catalyst, and the experimental results all show that the synergistic effect of the two is obvious.  The plasma-catalytic co-activation method is used to promote the conversion of methane into the target product C2 hydrocarbons. Although the heterogeneous catalysis of plasma may occur in the plasma area, plasma afterglow area and product collection area, because the pulsed corona plasma works under normal pressure, the particle density in the system is high and the collision probability is high, so The active particles such as free radicals have extremely short lifetimes, and the heterogeneous catalysis that occurs in the plasma region is mainly studied.

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