Biodegradable Poly(butylene adipate-co-terephthalate) composites reinforced with bio-based nanochitin: Preparation,enhanced mechanical and thermal properties

The accumulation of nonbiodegradable petrochemical-based polymers in the environment motivates the development and use of low-cost, eco-friendly, and biodegradable polymers. A series of biodegradable poly(butylene adipate-co-terephthalate) composites reinforced by sustainably sourced nanochitin were successfully prepared using melt blending and compression molding methods. Structural, thermal, and mechanical characterizations of poly(butylene adipate-co-terephthalate) (PBAT)/nanochitin composites were performed. SEM revealed that the nanochitin was uniformly dispersed throughout the PBAT matrix at low contents (<2 wt %), while DSC analyses revealed a corresponding increase in the crystallinity (32.6% enhancement) of the PBAT matrix. The tensile strength and elongation at break of the PBAT/nanochitin composite containing 0.5 wt % nanochitin were higher by 82.5 and 64.2%, respectively, compared with pristine PBAT. The Chitin-0.5 composite also showed improved thermal stability compared with PBAT (the char yield improved by 8%) due to the uniform dispersion of nanochitin in the PBAT matrix. The enhanced performance of the PBAT/nanochitin composites, prepared without an added compatibilizer, informs the development of improved biodegradable PBAT-based polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48485.     

Isomerization-induced introduction of metal cations into polyoxomolybdate-surfactant hybrid crystals

Monovalent metal cations (Ag⁺, K⁺, and Cs⁺) were successfully introduced into inorganic-organic hybrid crystals composed from β-type octamolybdate (β-Mo₈) and hexadecylpyridinium (C₁₆py). The introduction of metal cations was induced by the molecular isomerization from α-Mo₈ to β-Mo₈ anion. All hybrid crystals consisted of alternate stacking of β-Mo₈ inorganic and C₁₆py organic layers. In the inorganic layers, the metal cations and β-Mo₈ anions were connected to form one- or two-dimensional arrangement, which depended on the ionic radius of metal cations.     

Tests of continuous concrete slabs reinforced with carbon fibre reinforced polymer bars

Although several research studies have been conducted on simply supported concrete elements reinforced with fibre reinforced polymer (FRP) bars, there is little reported work on the behaviour of continuous elements. This paper reports the testing of four continuously supported concrete slabs reinforced with carbon fibre reinforced polymer (CFRP) bars. Different arrangements of CFRP reinforcement at mid-span and over the middle support were considered. Two simply supported concrete slabs reinforced with under and over CFRP reinforcement and a continuous concrete slab reinforced with steel bars were also tested for comparison purposes. All continuous CFRP reinforced concrete slabs exhibited a combined shear–flexure failure mode. It was also shown that increasing the bottom mid-span CFRP reinforcement of continuous slabs is more effective than the top over middle support CFRP reinforcement in improving the load capacity and reducing mid-span deflections. The ACI 440.1R–06 formulas overestimated the experimental moment at failure but better predicted the load capacity of continuous CFRP reinforced concrete slabs tested. The ACI 440.1R–06, ISIS–M03–07 and CSA S806-06 design code equations reasonably predicted the deflections of the CFRP continuously supported slabs having under reinforcement at the bottom layer but underestimated deflections of continuous slabs with over-reinforcement at the bottom layer.     

An eco-friendly process: Predictive modelling of copper adsorption from aqueous solution on Spirulina platensis

The adsorption of copper ions on Spirulina platensis was studied as a function of contact time, initial metal ion concentration, and initial pH regimes. Characterization of this adsorbent was confirmed by FTIR spectrum. Modified Gompertz and Logistic models have not been previously applied for the adsorption of copper. Logistic was the best model to describe experimental kinetic data. This adsorption could be explained by the intra-particle diffusion, which was composed of more than one sorption processes. Langmuir, Freundlich, and Redlich–Peterson were fitted to equilibrium data models. According to values of error functions and correlation coefficient, the Langmuir and Redlich–Peterson models were more appropriate to describe the adsorption of copper ions on S. platensis. The monolayer maximum adsorption capacity of copper ions was determined as 67.93 mg g^?1. Results indicated that this adsorbent had a great potential for removing of copper as an eco-friendly process.     

Syntheses and characterizations of two-dimensional polymers based on tetraimidazole tetraphenylethylene ligand with aggregation-induced emission property

Two new coordination polymers [Co(TIPE)(H₂O)₂]·Hbtc·CH₃CN·3H₂O (1) and [Cd(TIPE)_0.5(m-bdc)(H₂O)]·CH₃OH·H₂O (2) (TIPE = tetra(3-imidazoylphenyl)ethylene, H₃btc = 1,3,5-benzenetricarboxylate, m-H₂bdc = 1,3-benzenedicarboxylate) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and PXRD. Furthermore, the luminescent properties of complexes 1, 2 and TIPE ligand have also been investigated in the solid at room temperature.     

超快速加热退火下保温时间对5083铝合金组织及力学性能的影响

利用Gleeble-3500热模拟系统和电子背散射衍射(EBSD)技术对5083铝合金超快速退火组织的演变规律进行了研究,探讨了5083铝合金经过80%冷轧变形后以500 ℃/s加热至450 ℃时,不同保温时间(1~60 s,冷却速度40 ℃/s)对退火组织及力学性能的影响。结果表明,随退火保温时间从1 s延长到60 s,5083铝合金的平均晶粒尺寸由4.94 μm增大到6.44 μm,合金中主要产生了再结晶立方退火织构{001}<100>、旋转立方织构{001}<110>,以及少量的高斯织构{011}<100>和黄铜型织构{011}<211>。当退火保温时间从1 s增加到60 s,整体上合金中的再结晶退火织构先增强再减弱。退火保温时间对5083铝合金的强度影响较小,5083铝合金的屈服强度、抗拉强度没有明显的变化,分别约为170 MPa、326 MPa,而其伸长率由25.63%逐渐增大至30.06%,最后又降低至25.20%。     

Photoluminescent and electrical properties of novel Nd3+ doped ZnV2O6 and Zn2V2O7

Nd³⁺ doped ZnV₂O₆ and Zn₂V₂O₇ samples were synthetized by using melt-quenching method. X-ray diffraction patterns indicate that both samples are polycrystalline. The crystallinity was also verified by Raman scattering, from which the different vibrational modes of ZnV₂O₆ and Zn₂V₂O₇ were detected. Electron dispersive spectroscopy (EDS) analysis shows that the Nd³⁺ incorporation into the ZnV₂O₆ and Zn₂V₂O₇ hosts is around 0.9±0.1 and 0.2±0.1 at%, respectively. The micrographs obtained by Scanning Electron Microscopy, reveal that the Nd³⁺ doped ZnV₂O₆ sample is predominantly composed by micro-rods, whereas the Nd³⁺ doped Zn₂V₂O₇ one is only composed by irregular blocks. The band gap energies (E_g) were calculated from the diffuse reflectance spectra by the Kubelka–Munk equation; E_g values resulted to be 2.24 and 2.86 eV for the Nd³⁺ doped ZnV₂O₆ and Zn₂V₂O₇ samples, respectively. By means of two points dark conductivity measurements, conductivity values in the 10⁻⁴–10⁻⁶ and 10⁻⁶–10⁻⁸(Ω cm)⁻¹range for the Nd³⁺ doped ZnV₂O₆ and Zn₂V₂O₇ samples were measured, respectively. The conductivity as a function of the temperature indicated a semiconductor behavior. The photoluminescence spectra upon Ar⁺ laser excitation at 488 nm, exhibited the Nd³⁺ characteristics emissions. For instance, the Nd³⁺ doped ZnV₂O₆ sample displayed the Nd^{3+ 4}F_5/2→⁴I_9/2 and ⁴F_3/2→⁴I_9/2 emissions; while the Nd³⁺ doped Zn₂V₂O₇ one showed the Nd³⁺ characteristic emissions associated with the ⁴G_7/2, ⁴F_9/2, ⁴F_5/2 and ⁴F_3/2→⁴I_9/2 transitions. The lifetimes were 80 and 130 µs for the Nd³⁺ doped ZnV₂O₆ and Zn₂V₂O₇ samples, respectively. All these results suggest a successful synthesis of Nd³⁺ doped zinc vanadate compounds by the melt-quenching technique.     

Electrophoretic co-deposition of Bi2O3–multiwalled carbon nanotubes coating as supercapacitor electrode

Nafion is suggested as an efficient assistant in preparing supercapacitor by employing nanoparticles. In this work, using a bi-additive of 0.10-mM NaOH + 0.10 g L⁻¹ Nafion, Nafion-assisted electrophoretic co-deposition of Bi₂O₃–multiwalled carbon nanotubes (MWCNTs) coating is successfully realized in ethanol solvent. The capacitance performances of the electrophoretic coatings in 6.0-M KOH electrolyte are investigated by cyclic voltammetry and galvanostatic charge–discharge techniques. Comparing with Bi₂O₃ coating prepared with electrophoretic deposition (EPD) by employing other additive (such as polyethyleneimine), the Bi₂O₃ coating prepared by Nafion-assisted EPD shows a better capacitance performance. Benefiting from the improvement in coating conductivity caused by MWCNTs, with a small additional amount of 4.0 wt.%, the Bi₂O₃–MWCNTs coating exhibits an amazing 164% increase of mass-specific capacitance (473 F g⁻¹ at the current density of 1.0 A g⁻¹) in comparison with pure Bi₂O₃ coating (179 F g⁻¹ at the current density of 1.0 A g⁻¹). The cyclic stability test exhibits excellent capacitance retention of 88.7% over 3000 cycles at a constant current density of 10.0 A g⁻¹. This work combines the advantages of MWCNTs, Nafion, and EPD to provide a facile route for preparing Bi₂O₃-based coating as a high-performance supercapacitor electrode.