A Study of the Effect of Sintering Conditions of Mg0.95Ni0.05Ti3 on Its Physical and Dielectric Properties

Mg_0.95Ni_0.05TiO₃ ceramics were prepared by traditional solid-state route using sintering temperatures between 1300 and 1425 °C and holding time of 2–8 h. The sintered samples were characterized for their phase composition, micro-crystalline structure, unit–cell constant, and dielectric properties. A two-phase combination region was identified over the entire compositional range. The effect of sintering conditions was analyzed for various properties. Both permittivity (ε_r) and Q factor (Q_f) were sensitive to sintering temperatures and holding times, and the optimum performance was found at 1350 °C withholding time of 4 h. The temperature coefficient of resonant frequency (τ_f) in a range from −45.2 to −52 (ppm/°C) and unit–cell constant were not sensitive to both the sintering temperature and holding time. An optimized Q factor of 192,000 (GHz) related with a permittivity (ε_r) of 17.35 and a temperature coefficient (τ_f) of −47 (ppm/°C) was realized for the specimen sintered at 1350 °C withholding time of 4 h. For applications of 5G communication device (filter, antennas, etc.), Mg_0.95Ni_0.05TiO₃ is considered to be a suitable candidate for substrate materials.     

Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe₂)₄) and ammonia yield precipitates with composition TiC_0.5N_1.1H_2.3. Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 °C in NH₃ yields nearly stoichiometric TiN. However, heating in N₂ atmosphere leads to isostructural carbonitrides, approximately TiC_0.2N_0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 °C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC_0.22N_1.01H_0.07, or Ti₃(C_0.17N_0.78H_0.05)_3.96, close to Ti₃(C,N)₄. Previous workers have suggested that the intermediate compound was an amorphous form of Ti₃N₄. TEM investigation of the material indicates the presence of nanocrystalline regions <5 nm in dimension embedded in an amorphous matrix. Raman and IR reflectance data indicate some structural similarity with the rocksalt-structured TiN and Ti(C,N) phases, but with disorder and substantial vacancies or other defects. XAS indicates that the local structure of the amorphous solid is based on the rocksalt structure, but with a large proportion of vacancies on both the cation (Ti) and anion (C,N) sites. The first shell Ti coordination is approximately 4.5 and the second-shell coordination ∼5.5 compared with expected values of 6 and 12, respectively, for the ideal rocksalt structure. The material is thus approximately 50% less dense than known Ti_x(C,N)_y crystalline phases.     

Untersuchungen im System Sm-C-N

An isothermal section at 1,000°C of the system Sm–C–N was examined by X-ray diffraction techniques. Complete solid solubility between the phases SmC_1–x and SmN could be established. No indication for the existence of a ternary samarium carbonitride phase analogous to La₁C_0.88N_0.77, could be found.

     

Nitrogen-Doped Porous Carbon Materials Derived from Graphene Oxide/Melamine Resin Composites for CO2 Adsorption

CO₂ adsorption in porous carbon materials has attracted great interests for alleviating emission of post-combustion CO₂. In this work, a novel nitrogen-doped porous carbon material was fabricated by carbonizing the precursor of melamine-resorcinol-formaldehyde resin/graphene oxide (MR/GO) composites with KOH as the activation agent. Detailed characterization results revealed that the fabricated MR(0.25)/GO-500 porous carbon (0.25 represented the amount of GO added in wt.% and 500 denoted activation temperature in °C) had well-defined pore size distribution, high specific surface area (1264 m²·g⁻¹) and high nitrogen content (6.92 wt.%), which was mainly composed of the pyridinic-N and pyrrolic-N species. Batch adsorption experiments demonstrated that the fabricated MR(0.25)/GO-500 porous carbon delivered excellent CO₂ adsorption ability of 5.21 mmol·g⁻¹ at 298.15 K and 500 kPa, and such porous carbon also exhibited fast adsorption kinetics, high selectivity of CO₂/N₂ and good recyclability. With the inherent microstructure features of high surface area and abundant N adsorption sites species, the MR/GO-derived porous carbon materials offer a potentially promising adsorbent for practical CO₂ capture.     

二氧化钛含量对铈稳定立方氧化锆陶瓷的性能影响

本文用无压烧结法成功制备了高硬度的立方氧化锆陶瓷,研究了氧化锆陶瓷的物相,Vickers硬度,显微结构,相对密度等性能,主要分析了TiO2添加量对Zr0.8Ce0.2O2陶瓷硬度和相对密度的影响。结果表明:烧结助剂TiO2可以有效抑制陶瓷晶粒异常生长,加快气孔排除,促进氧化锆陶瓷烧结致密化,提高陶瓷硬度。最高维氏硬度为20.2 GPa,最高相对密度达到了99.8%。     

Replacement of the Common Chromium Source CrCl3(thf)3 with Well-Defined [CrCl2(μ-Cl)(thf)2]2

CrCl₃(thf)₃ is a common starting material in the synthesis of organometallic and coordination compounds of Cr. Deposited as an irregular solid with no possibility of recrystallization, it is not a purity guaranteed chemical, causing problems in some cases. In this work, we disclose a well-defined form of the THF adduct of CrCl₃ ([CrCl₂(μ-Cl)(thf)₂]₂), a crystalline solid, that enables structure determination by X-ray crystallography. The EA data and XRD pattern of the bulk agreed with the revealed structure. Moreover, its preparation procedure is facile: evacuation of CrCl₃·6H₂O at 100 °C, treatment with 6 equivalents of Me₃SiCl in a minimal amount of THF, and crystallization from CH₂Cl₂. The ethylene tetramerization catalyst [iPrN{P(C₆H₄-p-Si(nBu)₃)₂}₂CrCl₂]⁺[B(C₆F₅)₄]⁻ prepared using well-defined [CrCl₂(μ-Cl)(thf)₂]₂ as a starting material exhibited a reliably high activity (6600 kg/g-Cr/h; 1-octene selectivity at 40 °C, 75%), while that of the one prepared using the impure CrCl₃(thf)₃ was inconsistent and relatively low (~3000 kg/g-Cr/h). By using well-defined [CrCl₂(μ-Cl)(thf)₂]₂ as a Cr source, single crystals of [(CH₃CN)₄CrCl₂]⁺[B(C₆F₅)₄]⁻ and [{Et(Cl)Al(N(iPr)₂)₂}Cr(μ-Cl)]₂ were obtained, allowing structure determination by X-ray crystallography, which had been unsuccessful when the previously known CrCl₃(thf)₃ was used as the Cr source.     

In-Situ Synthesis and Characterization of Nanocomposites in the Si-Ti-N and Si-Ti-C Systems

The pyrolysis (1000 °C) of a liquid poly(vinylmethyl-co-methyl)silazane modified by tetrakis(dimethylamido)titanium in flowing ammonia, nitrogen and argon followed by the annealing (1000–1800 °C) of as-pyrolyzed ceramic powders have been investigated in detail. We first provide a comprehensive mechanistic study of the polymer-to-ceramic conversion based on TG experiments coupled with in-situ mass spectrometry and ex-situ solid-state NMR and FTIR spectroscopies of both the chemically modified polymer and the pyrolysis intermediates. The pyrolysis leads to X-ray amorphous materials with chemical bonding and ceramic yields controlled by the nature of the atmosphere. Then, the structural evolution of the amorphous network of ammonia-, nitrogen- and argon-treated ceramics has been studied above 1000 °C under nitrogen and argon by X-ray diffraction and electron microscopy. HRTEM images coupled with XRD confirm the formation of nanocomposites after annealing at 1400 °C. Their unique nanostructural feature appears to be the result of both the molecular origin of the materials and the nature of the atmosphere used during pyrolysis. Samples are composed of an amorphous Si-based ceramic matrix in which TiN_xC_y nanocrystals (x + y = 1) are homogeneously formed “in situ” in the matrix during the process and evolve toward fully crystallized compounds as TiN/Si₃N₄, TiN_xC_y (x + y = 1)/SiC and TiC/SiC nanocomposites after annealing to 1800 °C as a function of the atmosphere.     

Involvement of the γ Isoform of cPLA2 in the Biosynthesis of Bioactive N-Acylethanolamines

Arachidonylethanolamide (anandamide) acts as an endogenous ligand of cannabinoid receptors, while other N-acylethanolamines (NAEs), such as palmitylethanolamide and oleylethanolamide, show analgesic, anti-inflammatory, and appetite-suppressing effects through other receptors. In mammalian tissues, NAEs, including anandamide, are produced from glycerophospholipid via N-acyl-phosphatidylethanolamine (NAPE). The ɛ isoform of cytosolic phospholipase A₂ (cPLA₂) functions as an N-acyltransferase to form NAPE. Since the cPLA₂ family consists of six isoforms (α, β, γ, δ, ɛ, and ζ), the present study investigated a possible involvement of isoforms other than ɛ in the NAE biosynthesis. Firstly, when the cells overexpressing one of the cPLA₂ isoforms were labeled with [¹⁴C]ethanolamine, the increase in the production of [¹⁴C]NAPE was observed only with the ɛ-expressing cells. Secondly, when the cells co-expressing ɛ and one of the other isoforms were analyzed, the increase in [¹⁴C]N-acyl-lysophosphatidylethanolamine (lysoNAPE) and [¹⁴C]NAE was seen with the combination of ɛ and γ isoforms. Furthermore, the purified cPLA₂γ hydrolyzed not only NAPE to lysoNAPE, but also lysoNAPE to glycerophospho-N-acylethanolamine (GP-NAE). Thus, the produced GP-NAE was further hydrolyzed to NAE by glycerophosphodiesterase 1. These results suggested that cPLA₂γ is involved in the biosynthesis of NAE by its phospholipase A₁/A₂ and lysophospholipase activities.     

Preparation and Characterization of Thin-Film Solar Cells with Ag/C60/MAPbI3/CZTSe/Mo/FTO Multilayered Structures

New solar cells with Ag/C₆₀/MAPbI₃/Cu₂ZnSnSe₄ (CZTSe)/Mo/FTO multilayered structures on glass substrates have been prepared and investigated in this study. The electron-transport layer, active photovoltaic layer, and hole-transport layer were made of C₆₀, CH₃NH₃PbI₃ (MAPbI₃) perovskite, and CZTSe, respectively. The CZTSe hole-transport layers were deposited by magnetic sputtering, with the various thermal annealing temperatures at 300 °C, 400 °C, and 500 °C, and the film thickness was also varied at 50~300 nm The active photovoltaic MAPbI₃ films were prepared using a two-step spin-coating method on the CZTSe hole-transport layers. It has been revealed that the crystalline structure and domain size of the MAPbI₃ perovskite films could be substantially improved. Finally, n-type C₆₀ was vacuum-evaporated to be the electronic transport layer. The 50 nm C₆₀ thin film, in conjunction with 100 nm Ag electrode layer, provided adequate electron current transport in the multilayered structures. The solar cell current density–voltage characteristics were evaluated and compared with the thin-film microstructures. The photo-electronic power-conversion efficiency could be improved to 14.2% when the annealing temperature was 500 °C and the film thickness was 200 nm. The thin-film solar cell characteristics of open-circuit voltage, short-circuit current density, fill factor, series-resistance, and Pmax were found to be 1.07 V, 19.69 mA/cm², 67.39%, 18.5 Ω and 1.42 mW, respectively.     

正极材料Li(Ni0.5Mn0.5)1-xMxO2 (M=Ti，Al；x=0，0.02)电化学行为的比较研究

0IntroductionMany efforts have been made to develop newmaterials as an alternative to LiCoO2due to the rela-tively high cost and toxicity of Co.Much attention hasbeen paid to layered structure cathode materials suchas LiMnO2and LiNiO2due to their lower co…     

Solution/Ammonolysis Syntheses of Unsupported and Silica-Supported Copper(I) Nitride Nanostructures from Oxidic Precursors

Herein we describe an alternative strategy to achieve the preparation of nanoscale Cu₃N. Copper(II) oxide/hydroxide nanopowder precursors were successfully fabricated by solution methods. Ammonolysis of the oxidic precursors can be achieved essentially pseudomorphically to produce either unsupported or supported nanoparticles of the nitride. Hence, Cu₃N particles with diverse morphologies were synthesized from oxygen-containing precursors in two-step processes combining solvothermal and solid−gas ammonolysis stages. The single-phase hydroxochloride precursor, Cu₂(OH)₃Cl was prepared by solution-state synthesis from CuCl₂·2H₂O and urea, crystallising with the atacamite structure. Alternative precursors, CuO and Cu(OH)₂, were obtained after subsequent treatment of Cu₂(OH)₃Cl with NaOH solution. Cu₃N, in the form of micro- and nanorods, was the sole product formed from ammonolysis using either CuO or Cu(OH)₂. Conversely, the ammonolysis of dicopper trihydroxide chloride resulted in two-phase mixtures of Cu₃N and the monoamine, Cu(NH₃)Cl under similar experimental conditions. Importantly, this pathway is applicable to afford composite materials by incorporating substrates or matrices that are resistant to ammoniation at relatively low temperatures (ca. 300 °C). We present preliminary evidence that Cu₃N/SiO₂ nanocomposites (up to ca. 5 wt.% Cu₃N supported on SiO₂) could be prepared from CuCl₂·2H₂O and urea starting materials following similar reaction steps. Evidence suggests that in this case Cu₃N nanoparticles are confined within the porous SiO₂ matrix.     

PAN-based activated carbon nanofiber/metal oxide composites for CO2 and CH4 adsorption: influence of metal oxide

In the present study, we successfully prepared two different electrospun polyacrylonitrile (PAN) based-activated carbon nanofiber (ACNF) composites by incorporation of well-distributed Fe₂O₃ and Co₃O₄ nanoparticles (NPs). The influence of metal oxide on the structural, morphological, and textural properties of final composites was thoroughly investigated. The results showed that the morphological and textural properties could be easily tuned by changing the metal oxide NPs. Even though, the ACNF composites were not chemically activated by any activation agent, they presented relatively high surface areas (S_BET) calculated by Brunauer–Emmett–Teller (BET) equation as 212.21 and 185.12 m²/g for ACNF/Fe₂O₃ and ACNF/Co₃O₄ composites, respectively. Furthermore, the ACNF composites were utilized as candidate adsorbents for CO₂ and CH₄ adsorption. The ACNF/Fe₂O₃ and ACNF/Co₃O₄ composites resulted the highest CO₂ adsorption capacities of 1.502 and 2.166 mmol/g at 0 °C, respectively, whereas the highest CH₄ adsorption capacities were obtained to be 0.516 and 0.661 mmol/g at 0 °C by ACNF/Fe₂O₃ and ACNF/Co₃O₄ composites, respectively. The isosteric heats calculated lower than 80 kJ/mol showed that the adsorption processes of CO₂ and CH₄ were mainly dominated by physical adsorption for both ACNF composites. Our findings indicated that ACNF-metal oxide composites are useful materials for designing of CO₂ and CH₄ adsorption systems.     

Adsorption separation of carbon dioxide,methane, and nitrogen on Hβ and Na-exchanged β-zeolite

Adsorption isotherms of carbon dioxide （CO2）, methane （CH4）, and nitrogen （N2） on Hβand sodium exchanged β-zeolite （Naβ） were volumetrically measured at 273 and 303 K. The results show that all isotherms were of Brunauer type I and well correlated with Langmuir-Freundlich model. After sodium ions exchange, the adsorption amounts of three adsorbates increased, while the increase magnitude of CO2 adsorption capacity was much higher than that of CH4 and N2. The selectivities of CO2 over CH4 and CO2 over N2 enhanced after sodium exchange. Also, the initial heat of adsorption data implied a stronger interaction of CO2 molecules with Na＋ ions in Naβ . These results can be attributed to the larger electrostatic interaction of CO2 with extraframework cations in zeolites. However, Naβ showed a decrease in the selectivity of CH4 over N2, which can be ascribed to the moderate affinity of N2 with Naβ. The variation of isosteric heats of adsorption as a function of loading indicates that the adsorption of CO2 in Naβ presents an energetically heterogeneous profile. On the contrary, the adsorption of CH4 was found to be essentially homogeneous, which suggests the dispersion interaction between CH4 and lattice oxygen atoms, and such interaction does not depend on the exchangeable cations of zeolite.     

Insertion of Phosphenium Ions into a Bicyclo[1.1.0]Tetraphosphabutane Iron Complex

By reacting [{Cp‴Fe(CO)₂}₂(µ,η^1:1-P₄)] (1) with in situ generated phosphenium ions [Ph₂P][A] ([A]⁻ = [OTf]⁻ = [O₃SCF₃]⁻, [PF₆]⁻), a mixture of two main products of the composition [{Cp‴Fe(CO)₂}₂(µ,η^1:1-P₅(C₆H₅)₂)][PF₆] (2a and 3a) could be identified by extensive ³¹P NMR spectroscopic studies at 193 K. Compound 3a was also characterized by X-ray diffraction analysis, showing the rarely observed bicyclo[2.1.0]pentaphosphapentane unit. At room temperature, the novel compound [{Cp‴Fe}(µ,η^4:1-P₅Ph₂){Cp‴(CO)₂Fe}][PF₆] (4) is formed by decarbonylation. Reacting 1 with in situ generated diphenyl arsenium ions gives short-lived intermediates at 193 K which disproportionate at room temperature into tetraphenyldiarsine and [{Cp‴Fe(CO)₂}₄(µ₄,η^1:1:1:1-P₈)][OTf]₂ (5) containing a tetracyclo[3.3.0.0^2,7.0^3,6]octaphosphaoctane ligand.     

Adsorption separation of carbon dioxide, methane and nitrogen on monoethanol amine modified B-zeolite

A new type of composite adsorbents was synthesized by incorporating monoethanol amine (MEA) into β-zeolite. The parent and MEA-functionalized β-zeolites were characterized by X-ray diffraction (XRD), N₂ adsorption, and thermogravimetric analysis (TGA). The adsorption behavior of carbon dioxide (CO₂), methane (CH₄), and nitrogen (N₂) on these adsorbents was investigated at 303 K. The results show that the structure of zeolite was well preserved after MEA modification. In comparison with CH₄ and N₂, CO₂ was preferentially adsorbed on the adsorbents investigated. The introduction of MEA significantly improved the selectivity of both CO₂/CH₄ and CO₂/N₂, the optimal selectivity of CO₂/CH₄ can reach 7.70 on 40 wt% of MEA-functionalized β-zeolite (MEA(40)-β) at 1 atm. It is worth noticing that a very high selectivity of CO₂/N₂ of 25.67 was obtained on MEA(40)-β. Steric effect and chemical adsorbate-adsorbent interaction were responsible for such high adsorption selectivity of CO₂. The present MEA-functionalized β-zeolite adsorbents may be a good candidate for applications in flue gas separation, as well as natural gas and landfill gas purifications.     

The thermal dehydration and decomposition of Ba[Cu(C2O4)2(H2O)]·5H2O

The thermal behaviour of Ba[Cu(C₂O₄)₂(H₂O)]·5H₂O in N₂ and in O₂ has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The enthalpy for the dehydration was found to be 311±30 kJ mol^–1 (or 52±5 kJ (mol of H₂O)^–1). The overall enthalpy change for the decomposition of Ba[Cu(C₂O₄)₂] in N₂ was estimated from the combined area of the peaks of the DSC curve as –347 kJ mol^–1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly deceleratory and the -time curves could be described by the three dimensional diffusion (D3) model. The values of the activation energy and the pre-exponential factor for the dehydration were 125±4 kJ mol^–1 and (1.38±0.08)×10¹⁵ min^–1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.The values ofE _a andA were 206±23 kJ mol^–1 and (2.2±0.5)×10¹⁹ min^–1, respectively, for the fast process, and 259±37 kJ mol^–1 and (6.3±1.8)×10²³ min^–1, respectively, for the slow process.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthday     

Origins of Giant Dielectric Properties with Low Loss Tangent in Rutile (Mg1/3Ta2/3)0.01Ti0.99O2 Ceramic

The Mg²⁺/Ta⁵⁺ codoped rutile TiO₂ ceramic with a nominal composition (Mg_1/3Ta_2/3)_0.01Ti_0.99O₂ was synthesized using a conventional solid-state reaction method and sintered at 1400 °C for 2 h. The pure phase of the rutile TiO₂ structure with a highly dense microstructure was obtained. A high dielectric permittivity (2.9 × 10⁴ at 10³ Hz) with a low loss tangent (<0.025) was achieved in the as-sintered ceramic. After removing the outer surface, the dielectric permittivity of the polished ceramic increased from 2.9 × 10⁴ to 6.0 × 10⁴, while the loss tangent also increased (~0.11). The dielectric permittivity and loss tangent could be recovered to the initial value of the as-sintered ceramic by annealing the polished ceramic in air. Notably, in the temperature range of −60–200 °C, the dielectric permittivity (10³ Hz) of the annealed ceramic was slightly dependent (<±4.4%), while the loss tangent was very low (0.015–0.036). The giant dielectric properties were likely contributed by the insulating grain boundaries and insulative surface layer effects.     

Polymerisations of -caprolactone and β-butyrolactone with Zn-, Al- and Mg-based organometallic complexes

The reaction of EtAlCl₂ with 1,2-{LiN(PMes₂)}₂C₆H₄ (Mes = 2,4,6-Me₃C₆H₂) and of butyloctylmagnesium with 1,2-{NH(PPh₂)}₂C₆H₄ gave [AlEt(1,2-{N(PMes₂)}₂C₆H₄-κ²N,N′)(THF)] (1) and [Mg(1,2-{N(PPh₂)}₂C₆H₄-κ²N,N′)(THF)₂] (2), respectively. Complexes 1 and 2 were fully characterised by NMR (¹H, ¹³C, ³¹P) and IR spectroscopy and mass spectrometry. Complexes 1 and 2 were employed as catalysts in the polymerisation of -caprolactone, which produced polymers with a narrow molecular weight distribution. For comparison the polymerisations of -caprolactone and β-butyrolactone were carried out with the Zn complex [ZnPr{1-N(PMes₂)-2-N(PHMes₂)C₆H₄-κ²N,N′}] (3) as catalyst, which produced polymers with narrow molecular weight distributions and high molecular weights.     

Preparation of ethyl levulinate from wheat stalk over Zr(SO4)2/SiO2

A series of Zr(SO₄)₂/SiO₂ solid acid catalysts with different Zr(SO₄)₂ loadings were prepared by water-soluble-impregnation method at room temperature. Then, the prepared catalysts were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectrum, X-ray diffraction, adsorption/desorption of N₂, and temperature-programmed desorption of NH₃. The results showed that the active component Zr(SO₄)₂ was successfully adhered to the mesoporous SiO₂, and the acid amount of Zr(SO₄)₂/SiO₂ increased with the increasing of the Zr(SO₄)₂ loadings. Finally, the wheat stalk was used as raw material and depolymerized over Zr(SO₄)₂/SiO₂ to produce ethyl levulinate (EL). The reaction mixture was separated and purified by filtration and vacuum distillation. The kinetic characteristics and the reaction pathway were also studied. A comparative study showed that 20 wt.% Zr(SO₄)₂/SiO₂ exhibited higher catalytic activity. When reaction temperature, time, catalyst dosage and Zr(SO₄)₂ loadings were 190 °C, 50 min, 20 wt.% and 30 wt.%, the EL yield reached a maximum of 17.14%. The relative content of EL exceeded 90% after three steps of distillation.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.