Preparation of pressure-sensitive adhesives from tung oil via Diels-Alder reaction

In this study, tung oil was polymerized with a dimaleimide (4,4’-methylene-bis(N-phenylmaleimide) (MPMI) and two diacrylates (poly(propylene glycol) diacrylate (PPGDA) and bisphenol A glycerolate diacrylate (BPAGDA) via Diels-Alder reaction (DA reaction) to prepare pressure-sensitive adhesives (PSAs). On the one hand, the polymer of tung oil and MPMI was readily prepared however it was too rigid to serve as a PSA. On the other hand, the polymerization of tung oil with PPGDA or BPAGDA resulted in PSAs with peel strengths ranging from 0.1 to 0.2 N cm⁻¹ and loop tacks ranging from 0.4 to 0.5 N. Nevertheless, tung oil reacted readily with acrylic acid to form adducts (TOAA) with lower content of conjugated diene groups than those of tung oil. The use of TOAAs instead of tung oil to polymerize PPGDA failed to increase the peel strength of the resulting PSAs. However, polymerizations of TOAAs with BPAGDA resulted in PSAs with much higher peel strengths and much higher loop tacks than the polymerization of tung oil with BPAGDA. In addition, the introduction of a small amount of MPMI in the polymerization of TOAA and PPGDA significantly shortened the curing time.     

Conversion of pyrazoline to pyrazole in hydrazine treated N-substituted reduced graphene oxide films obtained by ion bombardment and their electrical properties

An efficient method for the conversion of pyrazoline to pyrazole in hydrazine treated N-substituted reduced graphene oxide (N-rGO) films at room temperature has been reported. This method comprises the Ar⁺ ion bombardment of the N-rGO films that are prepared by drop casting method. The X-ray photoelectron spectroscopy (XPS) data in association with the X-ray diffraction, Ultra-violet spectroscopy and Raman spectroscopy data reveal that the addition of hydrazine removes the epoxy and hydroxyl groups of graphite oxide largely, and the reaction of hydrazine with carbonyl groups at 1,3-position of GO yields the pyrazoline moiety at the edge of the exfoliated carbon network. Further, the XPS data of the bombarded N-rGO films at the threshold applied potential of ∼3 keV for 10 min show that the position of the N1s XPS peak shifts from 400.05 to 398.6 eV due to the bombardment, indicating a conversion occurs from non-aromatic pyrazoline to aromatic pyrazole moiety. The electrical results reveal that the conductivity of the N-rGO/pyrazole film (47,600 S/m) is higher than the N-rGO/pyrazoline film (25,000 S/m) by virtue of the enhancement in the length of the conjugation π bond. The conversion of pyrazoline to pyrazole is discussed based on the activation energy.     

Nanointerfacial strength between non-collagenous protein and collagen fibrils in antler bone

Antler bone displays considerable toughness through the use of a complex nanofibrous structure of mineralized collagen fibrils (MCFs) bound together by non-collagenous proteins (NCPs). While the NCP regions represent a small volume fraction relative to the MCFs, significant surface area is evolved upon failure of the nanointerfaces formed at NCP–collagen fibril boundaries. The mechanical properties of nanointerfaces between the MCFs are investigated directly in this work using an in situ atomic force microscopy technique to pull out individual fibrils from the NCP. Results show that the NCP–fibril interfaces in antler bone are weak, which highlights the propensity for interface failure at the nanoscale in antler bone and extensive fibril pullout observed at antler fracture surfaces. The adhesion between fibrils and NCP is additionally suggested as being rate dependent, with increasing interfacial strength and fracture energy observed when pullout velocity decreases.     

Synthesis and characterization of castor oil and ricinoleic acid capped CdS nanoparticles using single source precursors

We report the synthesis of castor oil and ricinoleic acid capped CdS nanoparticles by the thermolysis of piperidine (1) and tetrahydroquinoline (2) dithiocarbamate complexes of cadmium(II) at temperatures varying from 190 °C to 300 °C. Reaction parameters such as time and temperature were varied to study their effect on the properties and morphology. The optical properties of CdS were typical of particles that displayed quantum confinement effects. X-ray diffraction studies revealed the existence of both cubic and hexagonal phases depending on the reaction conditions. Ricinoleic acid capped CdS gave cubic phase particles whereas castor oil capped CdS gave both cubic and hexagonal phases dependent on the reaction temperature and the type of complex used. The morphology of the particles varied from oval-short rods to spherical shaped particles with sizes ranging from 10 to 22 nm. Rhodamine B (RhB) dye photodegradation studies of a representative CdS nanoparticles’ sample have been carried out in the presence of halogen light and studied using UV–visible spectroscopy.     

Non-fullerene organic solar cells with 7% efficiency and excellent air stability through morphological and interfacial engineering

We report on the fabrication of the poly{[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]} (PTB7) and poly{[N,N-9-bis(2-octyldodecyl)- naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)}(P(NDI2OD-T2)) active layer combination employing air brush spray coating technique in 2-methyl anisole. Optical absorption characteristics of the blend layer were examined utilizing UV–visible spectra in the wavelength sweep varying from 300 to 900 nm. Atomic force microscopy was utilized to analyze the surface characteristics of the fabricated active layer. Under the radiance of simulated solar light with 100 mW cm⁻² (AM 1.5G), the current density voltage (J-V) characteristics were determined by employing a solar simulator. Fullerene-free organic solar cells were build using a combination of P(NDI2OD-T2) acceptor and a polymer donor PTB7 with SnO₂ acting as an interlayer, which showed power conversion efficiency (PCEs) of more than 7.0%, which is considered as the best PCEs been reported for the chosen donor and the acceptor. The device is extremely stable, holding 75% of its unique effectiveness subsequent to being put away in air for 72 days even without encapsulation. These outcomes demonstrate that the spray-coated film is a feasible contrasting option to the vacuum-deposited ITO film in terms of cost for mass production and for roll-to-roll based organic solar cells.     

Alumina powder assisted carbon nanotubes reinforced Mg matrix composites

Mg matrix composites reinforced by carbon nanotubes (CNTs)-Al₂O₃ mixture, which was synthesized by in situ growing CNTs over Al₂O₃ particles through chemical vapor deposition (CVD) using Ni catalyst, were fabricated by means of powder metallurgy process, followed by hot-extrusion. By controlling synthesis conditions, the as-grown CNTs over Al₂O₃ particles possessed high degree of graphitization, ideal morphology, higher purity and homogeneous dispersion. Due to the ‘vehicle’ carrying effect of micrometer-level A₂O₃, CNTs were easy to be homogeneously dispersed in Mg matrix under moderate ball milling. Meanwhile, Al₂O₃ particles as catalyst carriers, together with CNTs, play the roles of synergistic reinforcements in Mg matrix. Consequently, the Mg matrix composites reinforced by CNTs-Al₂O₃ mixture exhibited remarkable mechanical properties.     

Mechanical,thermal and friction properties of rice bran carbon/nitrile rubber composites: Influence of particle size and loading

Four types of rice bran carbon (RBC) with different particle sizes were compounded with nitrile rubber (NBR) in a laboratory size two-roll miller. The obtained RBC/NBR composites were characterized using Field Emission Scanning Electron Microscopy (FE-SEM) and tensile tests. Experimental results showed the RBC with lowest particle size exhibited best dispersion state and superior reinforcement ability. Then, we investigated the influence of RBC loading on the morphology, vulcanization characteristics, mechanical, thermal and friction properties of NBR composites. Experimental results indicated that the incorporation of RBC resulted in higher torque values, longer curing time, but shorter scorch time. The addition of RBC remarkably improved the mechanical properties of NBR composites. However, when the RBC loading exceeded 60 phr, the improvement in the tensile strength was not significant due to the poor dispersion state and weak interfacial bonding between RBC and NBR matrix, which were confirmed by Mooney–Rivlin stress–strain curves and FE-SEM observations. The thermal stabilities of RBC/NBR composites were largely improved as the loading of RBC increased. Friction tests revealed that under a certain concentration, the presence of RBC increased the static friction coefficient of NBR composites, suggesting the anti-skid role of RBC in the NBR composites. The overall results demonstrated that RBC could act as ideal filler for NBR composites providing both economic and environmental advantages.     

Fe和Cu对6061再生铝合金凝固行为和热裂倾向的影响

利用双电偶热分析和约束杆模具热裂评价法,研究了Fe和Cu杂质元素对6061再生铝合金凝固特性和热裂倾向(HTS)的影响。结果表明,随着Fe和Cu元素含量的增加,再生铝合金的热裂倾向逐渐增大。Fe元素主要影响再生铝合金初期凝固行为,提高Al13Fe4富铁相的形核温度和含量,促使凝固过程中枝晶搭接完成,阻碍液相流动补缩。Cu元素主要影响再生铝合金末期凝固行为,低熔点Al5Cu2Mg8Si6相显著降低脆性温度区间的下限,并降低固相线附近糊状区强度,导致热裂性能恶化。     

Nitrogen-doped carbon nanofibers derived from polyacrylonitrile for use as anode material in sodium-ion batteries

Nitrogen-doped carbon nanofibers (N-CNFs) derived from polyacrylonitrile were successfully synthesized by a combination of electrospinning and thermal treatment processes. The as-prepared N-CNFs were used as anode material for sodium-ion batteries due to their unique fabric and weakly-ordered turbostratic structure as well as large spacing between graphene layers. Results show that N-CNFs carbonized at 800 °C delivered a high reversible capacity of 293 mAh g⁻¹ at a current density of 50 mA g⁻¹ in the first cycle. Even though the first-cycle Coulombic efficiency was 64%, it increased to nearly 100% only after a few initial cycles. Additionally, these N-CNFs showed excellent cycling and high-rate performance, and maintained a capacity of up to 150 mAh g⁻¹ even at an extremely high current density of 1000 mA g⁻¹ for over 200 cycles. It is, therefore, demonstrated that N-CNFs prepared under appropriate conditions are promising anode material candidate for sodium-ion batteries.     

Effect of Sm on hydrogen storage performance of La–Sm–Mg–Ni alloys

In this study, Sm was adopted in order to completely replace the expensive Pr/Nd elements in the A2B7 type alloy. The results indicate that Sm is a favourable element for forming Ce2Ni7 type and Ce5Co19 type phases. With the increasing amount of Sm, the discharge capacity of the alloy retains a value of 283·3 mAh g^?1 at the current density of 1200 mA g^?1. The maximum discharge capacity of the alloys increases with the increasing Sm content when Mg content is relatively low. By optimising the composition and processing technology, the cycle life the alloy enhances from 74 cycles to more than 540 cycles, and the maximum discharge capacity also increases from 300 to 355 mAh g^?1.