Processing of lignocellulosic polymer wastes using microwave irradiation

Lignin and mixed lignocellulosic natural polymer wastes have been accumulated in landfills over the past hundred years. These wastes should be processed to produce added- value chemicals and materials. This mini-review presents a brief literature survey related to state-of-the-art methods developed recently by the world research community to solve the problem of rational conversion of lignocellulosic polymer wastes, including production of hydrogen, synthesis gas, phenols, and monomers. The focus is made on microwave and plasma technologies used for lignocellulosic wastes processing.     

Study of water uptake in poly(ether ether ketone) irradiated by MeV O+ and Au+ ions

Poly(ether ether ketone) (PEEK) was irradiated with 4?MeV O⁺ and 5 and 10?MeV Au⁺ ions to the fluences from 10¹² to 10^14?cm^?2 and then treated in 5 M/l water solution of LiCl for one month at room temperature. After drying and removal of LiCl surface contamination, the depth distribution of LiCl embeded in PEEK was measured by the neutron depth profilig method (NDP) sensitive to ⁶Li isotope. Embeded LiCl is believed to map distribution of water diffusing into PEEK interior. The results show that the PEEK irradiated to the fluences above 1.10¹³cm^?2 is prone to water penetration to the depths of few microns. On the pristine PEEK and that irradiated to lower ion fluences only a surface Li contamination is observed.     

GaInP/GaAs/Ge三结太阳电池不同能量质子辐照损伤模拟

以GaInP/GaAs/Ge三结太阳电池为研究对象,开展了能量为0.7, 1, 3, 5, 10 MeV的质子辐照损伤模拟研究,建立了三结太阳电池结构模型和不同能量质子辐照模型,获得了不同质子辐照条件下的I-V曲线,光谱响应曲线,结合已有实验结果验证了本文模拟结果,分析了三结太阳电池短路电流、开路电压、最大功率、光谱响应随质子能量的变化规律,利用不同辐照条件下三结太阳电池最大输出功率退化结果,拟合得到了三结太阳电池最大输出功率随位移损伤剂量的退化曲线.研究结果表明,质子辐照会在三结太阳电池中引入位移损伤缺陷,使得少数载流子扩散长度退化幅度随质子能量的减小而增大,从而导致三结太阳电池相关电学参数的退化随质子能量的减小而增大.相同辐照条件下,中电池光谱响应退化幅度远大于顶电池光谱响应退化幅度,中电池抗辐照性能较差,同时中电池长波范围内光谱响应的退化幅度比短波范围更大,表明中电池相关电学参数的退化主要来源于基区损伤.     

Influence of Polarity and Activation Energy in Microwave–Assisted Organic Synthesis (MAOS)

The aim of this work was to determine the parameters that have decisive roles in microwave-assisted reactions and to develop a model, using computational chemistry, to predict a priori the type of reactions that can be improved under microwaves. For this purpose, a computational study was carried out on a variety of reactions, which have been reported to be improved under microwave irradiation. This comprises six types of reactions. The outcomes obtained in this study indicate that the most influential parameters are activation energy, enthalpy, and the polarity of all the species that participate. In addition to this, in most cases, slower reacting systems observe a much greater improvement under microwave irradiation. Furthermore, for these reactions, the presence of a polar component in the reaction (solvent, reagent, susceptor, etc.) is necessary for strong coupling with the electromagnetic radiation. We also quantified that an activation energy of 20–30 kcal mol⁻¹ and a polarity (μ) between 7–20 D of the species involved in the process is required to obtain significant improvements under microwave irradiation.     

Conventional vs. Microwave- or Mechanically-Assisted Synthesis of Dihomooxacalix[4]arene Phthalimides: NMR,X-ray and Photophysical Analysis §

Direct O-alkylation of p-tert-butyldihomooxacalix[4]arene (1) with N-(bromopropyl)- or N-(bromoethyl)phthalimides and K₂CO₃ in acetonitrile was conducted under conventional heating (reflux) and using microwave irradiation and ball milling methodologies. The reactions afforded mono- and mainly distal di-substituted derivatives in the cone conformation, in a total of eight compounds. They were isolated by column chromatography, and their conformations and the substitution patterns were established by NMR spectroscopy (¹H, ¹³C, COSY and NOESY experiments). The X-ray structures of four dihomooxacalix[4]arene phthalimide derivatives (2a, 3a, 3b and 5a) are reported, as well as their photophysical properties. The microwave (MW)-assisted alkylations drastically reduced the reaction times (from days to less than 45 min) and produced higher yields of both 1,3-di-substituted phthalimides (3a and 6a) with higher selectivity. Ball milling did not reveal to be a good method for this kind of reaction.     

Hydrolytic polycondensation of trimethoxymethylsilane under ultrasonic irradiation

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Radical processes initiated by ionizing radiation in PEEK and their macroscopic consequences

Poly (ether ether ketone) was irradiated with gamma rays or electron beam to investigate the radical process. The generated paramagnetic species were observed by electron spin resonance spectroscopy at ambient temperature and in liquid nitrogen. The effect of microwave power on saturation of the particular spectra and thermal annealing effects were determined. The following radicals were identified: radical anion, phenoxyl radical, and phenylperoxy radical. Despite the fact that the intermediates were formed as a result of backbone cleavage causing degradation, the macroscopic features were almost unaffected by irradiation up to dose of 1500 kGy.     

Zinc‐containing ionic liquid as a dual solvent‐catalyst in base‐free condensations under ultrasonic irradiation

In this study, natural‐based ionic liquid (IL) using caffeine (Caff), trietahnolamine (TEA) and ZnBr₂, [Caff‐TEA]⁺[ZnBr₃]^?, which features high catalytic activity and environmentally‐friendly nature was synthesized with melting point of 76 °C by a facile method. The synthesized [Caff‐TEA]⁺[ZnBr₃]^? has high catalytic activity as both of catalyst and solvent in condensation reactions for the synthesis of benzylidenes, bis‐hydroxyenones and xanthenes. Synthesized IL was characterized by proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD) and Energy‐dispersive X‐ray spectroscopy (EDX) analysis. Also synthesized heterocycles were characterized by FT‐IR, proton nuclear magnetic resonance (¹HNMR) and carbon nuclear magnetic resonance (¹³CNMR).     

Ultrasonic-assisted synthesis of nano-sized metal-organic framework; a simple method to explore selective and fast Congo Red adsorption

A novel mixed linker Metal-organic Framework, [Co(NH₂IsoBDC)(bpfn)].DMF (TMU-69), with amide and amino functionalized spacers (bpfn = N,N'-(naphthalene-1,5-diyl)diisonicotinamide, NH₂IsoBDCH₂ = 5-Aminoisophthalic acid) was synthesized through both solvothermal and ultrasonic approaches. Applying sonochemical irradiation led to ultrafast formation of Flower-shaped nanoplates of TMU-69 within 15 min with high yield while, solvothermal method takes 3 days to form the framework. Control of size and morphology was also enhanced through applying ultrasonic irradiations. The implication of applied time and concentration of reagents on size and morphology of nano-structured TMU-69 have been optimized. Applying higher concentration of initial material with optimized 60-minute irradiation forms uniform smaller sized nanoplates of TMU-69. Also, the efficiency of TMU-69 bulk and nanoplates toward removal of pollutant dyes from water was investigated. The selective adsorption of Congo Red was observed among other dyes. Also, drastic enhancement in removal kinetic of Congo Red through using ultrasonic assisted nanoplates of TMU-69 was obtained.     

Facile preparation of superhydrophobic nanorod surfaces through ion-beam irradiation

Obtaining superhydrophobic surfaces for their application in electronics and flexible wearable devices remains a significant challenge. Most previously reported methods for obtaining superhydrophobic surfaces involve complex and expensive preparation techniques and thus cannot be used for practical applications. Ion-beam irradiation is a simple and promising method for fabricating superhydrophobic nanostructures on large areas at a low cost. Ion-beam irradiation using argon and oxygen gases was used to prepare silica nanorod structures on glass substrates. This study is not just a modification of the surface of nanoparticles, but a change in nanoparticle shape. The nanorods were subsequently treated with perfluorooctyltriethoxysilane to obtain superhydrophobicity. The surface of the silica nanorods exhibited a static water contact angle of 153°, indicating superhydrophobicity. The combination of rough structures of silica nanorods and low surface energy resulted in superhydrophobicity. The surface properties were evaluated in detail using Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. The proposed method is facile, inexpensive, and can be used for the large-scale production of nanorod structures for potential industrial applications.