Influence of water addition on the modification of polyethylene surface by nitrogen atmospheric pressure plasma jet

Polyethylene (PE) has many excellent material properties (low density, high flexibility, good chemical resistance, etc.), and is widely used in industrial and medical fields. However, the practical applications of PE are sometimes limited due to its poor wettability. In this article, we employ pure nitrogen atmospheric pressure plasma jet (APPJ) and N₂-H₂O APPJ to hydrophilize PE surfaces. Wettability, time stability, chemical composition, micromorphology, and mechanical properties of the treated surfaces are investigated by contact angle measurement, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and electric digital display push–pull machine. The pure nitrogen APPJ can hydrophilize PE surfaces without inducing obvious microstructure changes, and relatively better wettability (water contact angle = 13°) could thereby be achieved. On the other hand, the N₂-H₂O APPJ creates micro/nanoscale pores on the treated hydrophilic surfaces, contributing to the better time stability and lower tensile strength. The results reported here clearly demonstrate the great potential of nitrogen APPJs with different water mixing ratios in controlling surface wettability and microstructures of polymer surfaces. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47136.     

Rolltruded Poly(Aryl Ether Ether Ketone) (PEEK) for Membrane Applications

Abstract

An investigation of the transport and separation of several permanent gases (CO₂, N₂, CH₄, and H₂) and vapors (H₂O and ethanol) in unprocessed and rolltruded poly(aryl ether ether ketone) (PEEK) thin films has been conducted to evaluate PEEK for membrane applications requiring thermally and chemically stable materials. Transport coefficients and separation factors have been determined at permeation temperatures ranging from 40 to ca. 180°C. The gas transport coefficients were found to increase by up to 30% depending on the processing conditions. Actual separation factors, determined for a CO₂/N₂ gas mixture (24.6 vol% CO₂), were depressed slightly in comparison to the ideal values obtained from pure component data. In contrast, water and ethanol vapor permeabilities declined between 10 and 15% as a result of processing. For a 39.1 wt% vapor mixture of H₂O in EtOH, ideal and actual separation factors, determined at 130°C, were in good agreement. In contrast, order of magnitude improvements in the actual versus ideal separation factors were found for 11.7 and 7.6 wt% mixtures of H₂O in EtOH in both unprocessed and rolltruded PEEK. A comparison with other membranes considered for high temperature vapor dehydrations suggests that PEEK may be an excellent polymer for these applications.     

LiMn2O4 Li-ion hybrid supercapacitors processed by nitrogen atmospheric-pressure plasma jet

LiCl–Mn(NO₃)₂·4H₂O pastes were screen-printed on a carbon cloth substrate and furnace-calcined to convert them into LiMn₂O₄. The LiMn₂O₄ electrode was then post-processed using a nitrogen atmospheric-pressure plasma jet (APPJ). APPJ processing created oxygen vacancy defects on the electrode surface. Electrochemical tests of the Li-ion hybrid supercapacitors (Li–HSCs) were performed by cyclic voltammetry (CV) and galvanostatic charging/discharging (GCD) in 1-M Li₂SO₄ aqueous solution. The results indicate that proper APPJ treatment optimizes the Li–HSCs performance, whereas excessive APPJ treatment may cause material damage. After 3-min APPJ treatment at 620 °C, the Li–HSCs exhibited a maximum areal capacitance of 87.96 mF/cm² with capacitance retention of 124.8% after a 1000-cycle CV test.     

Recycling photovoltaic silicon waste for fabricating porous mullite ceramics by low-temperature reaction sintering

In this study, porous mullite ceramics with coral-like structures were fabricated at a low temperature of 900 °C by using photovoltaic silicon waste (PSW) as the silicon source directly. The effects of additive content and sintering temperature on the mullitization reaction of green bodies were studied. The results showed that ammonium molybdate tetrahydrate molybdenum (H₂₄Mo₇N₆O₂₄·4H₂O) as an additive could reduce the reaction temperature for mullitization from 1100 °C to 900 °C. The research on the influence of catalyst on material properties showed that porous mullite ceramics with a flexural strength of 52.83 MPa, a 41.78 % porosity, a sintering expansion rate of 0.49 % and an average pore size of 0.23 μm could be fabricated by introducing 7.5 % H₂₄Mo₇N₆O₂₄·4H₂O at the sintering temperature of 1000 °C. This study develops an environment-friendly recycling method of PSW and provides a new idea for the low-cost preparation of porous mullite ceramics with high purity.     

Eigenschaften und thermische Reaktionen von Komplexen der Arendiazoniumsalze mit Kronenethern

Properties and Thermal Reactions from Complexes of Arene Diazonium Salts with Crown Ethers In contrast to 18-crown-6, the substituted crown ethers Benzo-18-crown-6, Dibenzo-18-crown-6, and Naphtho-18-crown-6 form in solution complexes with p-CH₃ C₆H₄ N₂⁺BF₄-characterized by a broad charge transfer absorption up to 550 nm. The formation constants lg K_c are 2,32 2,16 and 1,44 for Benzo-, Dibenzo-, and Naphtho-18-crown-6, respectively. Formation enthalpy ΔH = −7,5 kJ/mol and entropy ΔS = +18 J/K mol are measured in the case of p-Cl C₆H₄ N₂⁺BF₄⁻ and Dibenzo-18-crown-6 (20°). K_c depends on substituents in the arene ring of the diazonium salt; ϱ = +0,8. Thermal dediazoniation in the presence of Crown ethers results in high yields of the corresponding arene. This is explained by a fast radical chain reaction between the diazonium salt and the polyether (Meerwein-Reduction).     

Facile one‐step high‐temperature spray pyrolysis route toward metal carbide nanopowders

Fine ultrahigh‐temperature ceramic (UHTC) powders have found very important applications in many fields. In this work, a facile high‐temperature spray pyrolysis (HTSP) approach is implemented for the synthesis of HfC and TaC UHTC nanopowders starting from organic solvent (e.g., ethanol or 1‐pentanol) solutions of metal precursors (HfCl₄ or TaCl₅). It is proposed that, during HTSP, the precursor solution droplets would continuously undergo rapid drying, thermolysis (i.e., removal of low molecular weight species such as H₂, H₂O, and CO), and finally in situ carbothermal reduction (CTR) process to give rise to metal carbide nanopowders. The as‐obtained materials are shown by SEM as uniform and separated nanoparticles (~90 nm), whereas TEM reveals the carbide (e.g., HfC) nanoparticles are actually even smaller (~10‐20 nm) and embedded in amorphous carbon from excess solvent decomposition. It is found that among different processing parameters, the organic solvent used and the metal precursor concentration could largely influence the formation of metal carbide. In addition, lower HTSP temperatures (≤~1500°C for HfC) only lead to oxide‐carbon mixtures while higher temperatures (≥~1650°C) promote carbide formation. The HTSP method developed in this work is simple, low‐cost and efficient, and could potentially be optimized further for future large‐scale manufacturing of ultrafine UHTC nanopowders.     

Characterization of ADN and ADN‐Based Propellants

Ammonium dinitramide (ADN), NH₄N(NO₂)₂ is being considered as one of the potential new energetic oxidizers for composite propellants. In this study, ADN crystals, prills and two ADN‐based propellants having different relative amounts of ingredients were characterized. The concentration of the crystals and the prills samples was determined using ion chromatography. The thermal behavior of the crystals, prills and propellants was studied using DSC, simultaneous TG‐DTA‐FTIR‐MS, ARC (accelerating rate calorimeter), HFC (heat flux calorimeter) and INC (isothermal nanocalorimeter). Decomposition of ADN was observed from all of the samples at temperatures above the melting point of ADN (~ 92 °C). Formation of N₂O, NO₂, H₂O, CO₂, CO, N₂ and NO was detected during the ADN decomposition. The thermal stability of the ADN samples at temperatures below the melting point of ADN was studied. Early solid decomposition of ADN, which generates N₂O and H₂O, was observed at 60 °C. Electrostatic discharge (ESD) and impact sensitivity of the ADN samples were determined. The crystals and prills are sensitive to impact, while the two propellants are relatively less ESD and impact sensitive.     

The morphology of poly(aryl-ether-ether-ketone)

The morphology and related properties are described for the aromatic thermoplastic poly(aryl-ether-ether-ketone) (PEEK) [C₆H₄OC₆H₄OC₆H₄CO]_n. Topics covered include crystallinity, crystallization and melting behaviour, Iamellar thickness and spherulitic structure. The data are used to derive the following material parameters $\text{T1}{}_{\mathrm{<mtext>m</mtext>}}\text{= 395°}\text{C}$, σ_e = 49 erg cm^?2, σ_s = 38 erg cm^? and ΔH_F = 130 kJ kg^?1. PEEK is closely analogous to poly(ethylene terephthalate) in its crystallization behaviour except that the main transitions occur about 75°C higher.     

Solubilite de l'eau dans le melange gazeux (N2 + 3 H2) comprime—teneurs a la saturation—methode de calcul

The solubility of water in the synthesis gas (N₂ + 3H₂) has been measured between ?20°C and +15°C, at pressures varying from 100 to 400 atm. These results are coherent with those formerly published concerning higher temperatures.An easy method for calculating solubility is explained. It gives an accurate account of measures relating to the systems containing water or ammonia and a nonpolar component. For instance, the author presents the results obtained for the mixtures (H₂O + N₂ + 3H₂) and the mixtures (NH₃ + N₂ + 3H₂).     

Preferential CO Oxidation in the Presence of H2, H2O and CO2 at Short Contact-times

High selectivities and conversions in the preferential oxidation of CO in the presence of large quantities of H₂, H₂O and CO₂ are demonstrated on noble metal catalysts at millisecond contact times (~10–15 ms) for temperatures between 150 and 500 °C. With a simulated water-gas shift product stream containing 0.5% CO and varying amounts of H₂, H₂O and CO₂, we are able to achieve ~90% CO conversions on a Ru catalyst at temperatures of ~300 °C using a stoichiometric amount of O₂ (0.25%). Experiments with and without O₂ and with varying H₂O reveal that significant water-gas shift occurs on Pt and Pt-ceria catalysts at temperatures between 250 and 400 °C, while significant CH₄ is formed on Ru and Rh catalysts at temperatures greater than 250 and 350 °C, respectively. The presence of H₂O blocks H₂ adsorption and allows preferential CO oxidation at higher temperatures where rates are high. We propose that a multistage preferential oxidation reactor using these catalysts can be used to bring down CO content from 5000 ppm at the reactor entrance to less than 100 ppm at very short contact-times.     

One‐step fabrication of fluoropolymer transparent films with superhydrophobicity by dry method

Fluoropolymer transparent thin films were deposited on different substrates by one‐step vacuum evaporation method, which exhibit superhydrophobic property with water contact angle (CA) greater than 150°. Polytetrafluoroethylene (PTFE) film with network structure shows high oleophobicity with oil CA of 138°, whereas polytetrafluoroethylene‐perfluoropropylvinylethers (PFA) film with particle structure is superoleophilicity with oil CA near 0°. It is believed that different conformation of  CF₂ groups at the surface lead to this different surface activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structural characterization and conformational analysis of (aqua)(ethylenediamine-N,N,N′-triacetato)chromium(III) monohydrate complex. Crystal structure of the cis-equatorial isomer of [Cr(ed3a)(H2O)] · H2O

The structure of the cis-equatorial isomer of [Cr(ed3a)(H₂O)] · H₂O (ed3a=ethylenediamine-N,N,N^′-triacetate ion) was determined by X-ray diffraction method. The complex crystallizes in the monoclinic space group P2₁/n, a=7.004(1) Å, b=15.958(2) Å, c=11.046(1) Å, β=97.16(1)°, and Z=4. Conformational analysis of the three possible geometrical isomers, trans(H₂O,N^′), trans(H₂O,N_H), and trans(H₂O,O) of [Cr(ed3a)(H₂O)] moiety, performed using the consistent force field (CFF) program with the recently developed parameters for EDTA-type complexes, yielded structural details and energies of the minimized form for each of the isomers. Calculated energies showed that the cis-eq isomer is the most stable one, with the geometry in a very good agreement with the crystallographic structure. Comparison of the molecular mechanics calculations with those for the analogous [Cr(ed3p)(H₂O)] · H₂O (ed3p=ethylenediamine-N,N,N^′-tripropionate ion) revealed some general patterns for the conformational preference of EDTA-type complexes.     

Fabrication of mechanically robust superhydrophobic aluminum surface by acid etching and stearic acid modification

The aluminium surface with multi-scale structure has been fabricated via a facile and rapid solution-phase etching method by HCl/H₂O₂ etchants. After modification with stearic acid solution, the wettability of the etched aluminum surface turns into superhydrophobicity with an optimal water contact angle of 160° ± 2° and a sliding angle of 4° ± 1°. The processing conditions, such as the etching time, modifier types and the concentration of H₂O₂ are investigated to determine their effects on the surface morphology and wettability. As a result, the obtained sample shows excellent anti-adhesion property and bouncing phenomenon of water droplet. It can withstand mechanical abrasion for at least 100 cm under 12.3 kPa, or hydrostatic pressure under 24 ± 1 kPa without losing its superhydrophobicity, suggesting superior mechanical durability. Moreover, the surface also remains superhydrophobicity even after contacting corrosive liquids or long-term exposure in air over 100 days. Such a mechanically durable superhydrophobic aluminum surface can provide a promising practical application in various fields.     

Silicon Oxynitride Ceramics Prepared by Plasma Activated Sintering of Nanosized Amorphous Silicon Nitride Powder without Additives

Si₂N₂O ceramics were prepared by plasma activated sintering using nanosized amorphous Si₃N₄ powder without sintering additives within a temperature range of 1400°C–1600°C in vacuum. A mixed Si–N_4?n–O_n (n = 0, 1…4) amorphous structure was formed in the process of sintering, and Si₂N₂O crystals were nucleated where the local structure was similar with Si₂N₂O. After sintering at 1600°C, the Si₂N₂O ceramic was composed of elongated plate‐like Si₂N₂O grains and amorphous phase. The Si₂N₂O grains showed a width of less than 100 nm and a very high aspect ratio.     

Hydrothermal stability of fluorine-induced microporous silica membranes: Effect of steam treatment conditions

A fluorine-SiO₂ membrane was prepared using triethoxyfluorosilane (TEFS) as a Si precursor, and its hydrothermal stability was evaluated. The TEFS membrane calcined at 750°C had fewer Si-OH and Si-F groups in its network structure and showed H₂ permeance that was greater than 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ with H₂/N₂ and N₂/SF₆ permeance ratios of 10 and 210, respectively. This membrane performance was relatively stable under the temperature (< 500°C) used for steam treatment, regardless of the steam partial pressure (30, 90 kPa). On the other hand, when the steam treatment temperature was increased beyond 500°C, gas permeance decreased significantly and the membrane became highly selective for He and H₂ over smaller molecules (He/N₂: > 600, H₂/N₂: > 100). The relationship between the activation energy of H₂ and the permeance ratios (He/H₂, He/H₂O, H₂/H₂O) of a TEFS-derived membrane under steam treatment higher than 600°C resulted in a network pore size that approximated in conventional microporous SiO₂ membranes.     

Stabilizer Reaction is Cast Double Base Rocket Propellants. Part VIII: Characterization of propellant gassing properties during simulated aging

The decomposition process of two cast double base (CDB) propellant compositions was measured in vacuum. The process of gas evolution during heating of propellant compositions in vacuum has been studied using Vacuum Stability Test (VST) and Gas chromatography/ Mass Spectrometry (GC-MS) techniques. The results for the two different compositions aged at different storage temperatures for different periods of time were compared. VST has been used to quantify the amount of gases evolved during heating of propellant (aged and unaged) compositions at 100°C in vacuum, while quantitative GC-MS has been used to identify and quantify the evolved gases when the same propellant compositions were heated at 60 °C and 70 °C at low free volume. The results have shown that the amount and type of gases evolved depend on the composition of propellant, percentage of stabilizer etc. Composition 1 evolved CO₂, CO, N₂, NO and N₂O and produced the greater total gas volume, while Composition 2 evolved C0₂, CO and N₂ only. In each case C0₂ was the predominant gas and Composition 1 produced more COz but less CO than Composition 2. It is suggested that these differences in gas evolution profiles are due to the presence of different ballistic modifiers in the two propellant compositions. Gas evolution assessment using VST technique cannot be the strict measure of double base propellants stability.     

Separation of a gas mixture through a polymer membrane metallized with palladium

Investigations were carried out on the permeation of He, H₂, Ar, O₂ and N₂, in the range 26–60°C, and the separation at 20°C of a H₂ + N₂ gas mixture through a polytetrafluoroethylene (PTFE) membrane metallized in vacuum with a 1000 Å thick layer of palladium. In both experiments it was found that the thin layer of Pd acts as a gas-selective barrier which determines an increase of the H₂ permeation selectivity, respectively H₂-N₂ separation factor with up to 360%. The causes which determine the small decrease, up to 16%, of the H₂ flux which permeates through the metallized membrane are also discussed.     

Wettability of poly(ethylene terephthalate) film treated with low‐temperature plasma and their surface analysis by ESCA

The surface of poly(ethylene terephthalate) (PET) film was modified by low‐temperature plasma with O₂, N₂, He, Ar, H₂, and CH₄ gases, respectively. After being treated by low‐temperature plasma, their surface wettability and chemical composition were investigated by means of electron spectroscopy for chemical analysis (ESCA) and contact angle measurement. The result shows that the surface wettability of PET can be improved by low‐temperature plasma, and the effect of the modification is due mainly to the kind of the gases. Mainly because of the contribution of hydrogen bonding force γ[STACK]^c_S[ENDSTACK], the surface wettability of PET treated with O₂, N₂, He, and Ar plasma for a short time (3 min) increase sharply, and the surface wettability is also improved by H₂ plasma treatment; but the CH₄ plasma treatment does not improve the wettability of PET. ESCA shows that the effect of wettability of PET is tightly related to the presence of polar functional groups that reside in the outermost surface layer of PET. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1327–1333, 1999     

Dynamics and Selectivity of N<Subscript>2</Subscript>O Formation/Reduction During Regeneration Phase of Pt-Based Catalysts

The formation of N₂O has been studied by means of isothermal lean-rich experiments at 150, 180 and 250 °C over Pt–Ba/Al₂O₃ and Pt/Al₂O₃ catalysts with H₂ and/or C₃H₆ as reductants. This allows to provide further insights on the mechanistic aspects of N₂O formation and on the influence of the storage component. Both gas phase analysis and surface species studies by operando FT-IR spectroscopy were performed. N₂O evolution is observed at both lean-to-rich (primary N₂O) and rich-to-lean (secondary N₂O) transitions. The production of both primary and secondary N₂O decreases by increasing the temperature. The presence of Ba markedly decreases secondary N₂O formation. FT-IR analysis shows the presence of adsorbed ammonia at the end of the rich phase only for Pt/Al₂O₃ catalyst. These results suggest that: (i) primary N₂O is formed when undissociated NO in the gas phase and partially reduced metal sites are present; (ii) secondary N₂O originates from reaction between adsorbed NH₃ and residual NO_x at the beginning of the lean phase. Moreover, N₂O reduction was studied performing temperature programming temperature experiments with H₂, NH₃ and C₃H₆ as reducing agents. The reduction is completely selective to nitrogen and occurs at temperature higher than 250 °C in the case of Pt–Ba/Al₂O₃ catalyst, while lower temperatures are detected for Pt/Al₂O₃ catalyst. The reactivity order of the reductants is the same for the two catalysts, being hydrogen the more efficient and propylene the less one. Having H₂ a high reactivity in the reduction of N₂O, it could react with N₂O when the regeneration front is developing. Moreover, also ammonia present downstream to the H₂ front could react with N₂O, even if the reaction with stored NO_x seems more efficient.     

Single stage process for desizing,scouring, and bleaching of cotton fabric

The efficiency of a treating bath formulation consisting of H₂O₂, sodium hydroxide, chelating agents, wetting agent, metal ions, and MgSO₄ · 7H₂O in effecting combined desizing, scouring, and bleaching of cotton fabric using a winch beck system was investigated under different conditions. Presence of MgSO₄ · 7H₂O at a concentration of up to 3 g/l was essential for stabilization of the strongly alkaline H₂O₂ solutions (containing 10 g/l NaOH) at 95°C for 90 min to achieve complete starch removal and to bring about fabric with satisfactory whiteness and absorbency without seriously degrading the fibre substance. Chelating agents, namely EDTA and gluconic acid (2 g/l, each) assisted in stabilization of H₂O₂ even in presence of Fe³⁺, Cu²⁺ or both ions and resulted in improved whiteness and lower fibre degradation but had no effect on residual starch or on wettability of the fabric. The wetting agent used had no significant effect on stabilization of H₂O₂ and fibre degradation, but it helped starch removal and improved the wettability of the fabric. The decomposition of H₂O₂ increased by increasing its own concentration from 2 to 12 ml/l as well as the concentration of sodium hydroxide from 5 to 17.5 g/l. The same hold true for temperature (60 to 98°C) and duration (30 to 150 minutes). Combined desizing, scouring, and bleaching of loomstate cotton fabric could successfully be effected by using a treating bath consisting of sodium hydroxide (10 g/l), H₂O₂ (4 ml/l), MgSO₄ · 7H₂O (3 g/l), EDTA (2 g/l), gluconic acid (2 g/l), anionic/nonionic wetting agent (1.5 g/l) at 95°C for 90 min, and a material : liquor ratio of 1 : 25.