Biodegradable starch-based composites: effect of micro and nanoreinforcements on composite properties

Thermoplastic starch (TPS) matrix was reinforced with various kenaf bast cellulose nanofiber loadings (0–10 wt%). Thin films were prepared by casting and evaporating the mixture of aqueous suspension of nanofibers (NFs), starch, and glycerol which underwent gelatinization process at the same time. Moreover, raw fibers (RFs) reinforced TPS films were prepared with the same contents and conditions. The effects of filler type and loading on different characteristics of prepared materials were studied using transmission and scanning electron microscopies, X-ray diffractometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and moisture absorption analysis. Obtained results showed a homogeneous dispersion of NFs within the TPS matrix and strong association between the filler and matrix. Moreover, addition of nanoreinforcements decreased the moisture sensitivity of the TPS film significantly. About 20 % decrease in moisture content at equilibrium was observed with addition of 10 wt% NFs while this value was only 5.7 % for the respective RFs reinforced film

Properties of rice straw reinforced alkali activated cementitious composites

© 2020 The paper investigates the characteristics of rice straw reinforced alkali activated cementitious composites (AACC). The untreated and NaOH treated rice straw at the proportion of 1%, 2%, 3% by weight of binder was added to the mixes. Characteristics of rice straw have been studied by using SEM and XRD. Mechanical properties, water absorption, drying shrinkage and durability under wet/dry cycling have been investigated to evaluate the performance of the AACCs. SEM was also used to investigate the mechanism of deterioration of the AACC. The results show that rice straw has very significant positive effects on the performance of AACCs including increase in flexural and compressive strength, durability under wet/dry cycling, large reduction in drying shrinkage, and water absorption. In addition, alkali treatment is an effective method for enhancing bond between the rice straw and the matrix leading to improved performance of AACCs

A comprehensive review of techniques for natural fibers as reinforcement in composites::preparation, processing and characterization

Designing environmentally friendly materials from natural resources represents a great challenge in the last decade. However, the lack of fundamental knowledge in the processing of the raw materials to fabricate the composites structure is still a major challenge for potential applications.Natural fibers extracted from plants are receiving more attention from researchers, scientists and academics due to their use in polymer composites and also their environmentally friendly nature and sustainability. The natural fiber features depend on the preparation and processing of the fibers. Natural plant fibers are extracted either by mechanical retting, dew retting and/or water retting processes. The natural fibers characteristics could be improved by suitable chemicals and surface treatments. This survey proposes a detailed review of the different types of retting processes, chemical and surface treatments and characterization techniques for natural fibers. We summarize major findings from the literature and the treatment effects on the properties of the natural fibers are being highlighted

Caractérisation des interactions physico-chimiques dans un matériau composite à base de phyllosilicates, de chaux et de fibres végétales

Afin de comprendre les mécanismes physico-chimiques régissant les interactions entre des fibres de chanvre et une matrice à base de chaux et d'argiles, les effets de différents traitements chimiques des fibres sur l'état de surface des fibres d'une part et sur les propriétés mécaniques des composites d'autre part ont été évalués. Un traitement basique à l'hydroxyde de sodium (NaOH) permet ainsi d'augmenter les forces d'adhésion entre la fibre et un colloïde de silice et d'accroître les propriétés mécaniques d'un matériau composite dont la matrice est constituée de chaux uniquement ou de chaux et de kaolin. Cette amélioration peut être le résultat d'une augmentation de la rigidité de la fibre et d'une homogénéité en surface qui la rendent plus réactive. Les autres traitements réalisés, avec de l'acide éthylène diamine tétra-acétique (EDTA), du polyéthylène imine (PEI), une solution saturée d'eau de chaux et une solution de chlorure de calcium n'ont pas d'effets sur les propriétés mécaniques.In order to understand the physico-chemical mechanisms governing the interactions between hemp fibres and mineral matrices based on lime and on mixtures of lime and clay minerals, the influence of various chemical treatments of fibres on their surface properties and on macroscopic mechanical properties of mortars were evaluated. treatment with sodium hydroxide (NaOH) removes various organic components from the surface of the fibres, increases the adhesion forces between the fibre and a colloid made of silica and improves the mechanical properties of the resulting composites for lime and lime/kaolin matrices. An explanation for this behaviour could be linked to an increase of the fibre surface roughness and homogeneity. Other chemical treatments, with Ethylene Diamine Tetra-acetic Acid (EDTA), Polythylene imine (PEI), a saturated lime solution and a calcium chloride solution have no impact on the mechanical properties of the composite material.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

“Cold ceramics”: low temperature processing of ceramics for applications in composites

International audienc

InP/ZnS nanocrystals: Coupling NMR and XPS for fine surface and interface description

International audienceAdvanced 1H, 13C, and 31P solution- and solid-state NMR studies combined with XPS were used to probe, at the molecular scale, the composition (of the core, the shell, and the interface) and the surface chemistry of InP/ZnS core/shell quantum dots prepared via a non-coordinating solvent strategy. The interface between the mismatched InP and ZnS phases is composed of an amorphous mixed oxide phase incorporating InPO x (with x = 3 and predominantly 4), In2O3, and InOy(OH)3-2y (y = 0, 1). Thanks to the analysis of the underlying reaction mechanisms, we demonstrate that the oxidation of the upper part of the InP core is the consequence of oxidative conditions brought by decarboxylative coupling reactions (ketonization). These reactions occur during both the core preparation and the coating process, but according to different mechanisms

Experimental Investigation on Shear and Hardness of Abaca based Hybrid Composites

Present technology development in the area of materials replaces the conventional materials used in automobile and aerospace sector by composite materials due their less weight and bio degradability. This paper aims to fabricate and investigate the mechanical properties of abaca-raffia hybrid composite fabricated by hand layup process. Since, abaca fiber has more strength than other fibers like kenaf, banana and sisal, the composite with this fiber can be suitable replacement material for automotive applications.The properties like double shear and hardnessare evaluated andthe result shows that the double shear properties and hardness of the hybrid composites [GFRP+Abaca+Raffia] is higher than other two combinations. The internal microstructure of the hybrid composites were analysed using Scanning electron microscope (SEM)

From rational design of organometallic precursors to optimized synthesis of core/shell Ge/GeO2 nanoparticles

International audienceThe synthesis of germanium nanoparticles has been carried out, thanks to the design of novel aminoiminate germanium(II) precursors: (ATI)GeZ (with Z = OMe, NPh2, and ATI = N,N′-diisopropyl-aminotroponiminate) and (Am)2Ge (Am = N,N′-bis(trimethylsilyl)phenyl amidinate). These complexes were fully characterized by spectroscopic techniques as well as single crystal X-ray diffraction. The thermolysis of both complexes yielded NPs which display similar features that are a Ge/GeO2 core/shell structure with a mean diameter close to 5 nm with a narrow size distribution (300 °C) classically reported in the literature for the preparation of germanium-based NPs were necessary for thermolysis of the complexes (ATI)GeZ, the use of amidinate-based precursors allows the preparation at an unprecedented low temperature (160 °C) for the thermolytic route. As suggested by a mechanistic study, the lower reactivity of (ATI)GeZ (for which the concomitant use of high temperature and acidic reagent is required) was explained in terms of lower ring strain compared to the case of (Am)2Ge