Convenient Mechanical Properties Research Articles

Bio-based chitosan and cellulose ionic liquid gels: polymeric soft materials for the desulfurization of fuel

Bio-based ionic liquid gels are new efficient soft materials, exhibiting convenient mechanical properties, that can be applied in the desulfurization of fuel to prevent air pollution.

Influence of process parameters on the interlayer bond strength of concrete elements additive manufactured by Shotcrete 3D Printing (SC3DP)

Shotcrete 3D Printing (SC3DP) is a novel robot-guided AM technology developed at Technische Universität Braunschweig in the environment of the Digital Building Fabrication Laboratory (DBFL). For successful automation, it is crucial to understand and redefine the entire concrete spraying process with all its interdependent parameters. This paper presents the basic principles of the SC3DP technology together with the results of a comparative study on the influence of the two concrete printing techniques extrusion and SC3DP on the interlayer bond strength. In particular, the effect of different time intervals between the deposition of two adjacent layers regarding mechanical properties (bond strength) is investigated. As will be shown, the SC3DP method allows convenient mechanical properties although the printed samples exhibit distinct anisotropies. The reasons are discussed based on investigations of the air void distribution by micro CT and mechanical test results.

Evaluation of physical, mechanical and biological properties of β-tri-calcium phosphate/Poly-3-hydroxybutyrate nano composite scaffold for bone tissue engineering application

ABSTRACT Design of a scaffold with convenient mechanical properties to emulate bone structure is a major challenge for bone tissue engineers. In this study, porous ceramic scaffolds containing various weight fractions of nano β-tricalcium phosphate (nβ-TCP) (with a particle size of about 50-70 nm) were prepared by the replication method. Synthesised scaffolds were then coated with poly(3‐hydroxybutyrate) (PHB) for 30 and 60 sec. According to the morphological and mechanical tests, it was determined that synthesised scaffold containing 50 wt.% of nβ-TCP with a coating time of 30 sec showed desirable properties in bone tissue engineering. The bioactivity of this scaffold indicated that the bone-like apatite layers were well formed on the nanocomposite scaffold. Cell culture study showed a significant increase in cell proliferation between the coated, uncoated and control sample after 5 days of cell culturing. The results confirm that this nanocomposite scaffold has good potential for bone tissue engineering applications.

Polypyrrole-Coated Polycaprolactone-Gelatin Conductive Nanofibers: Fabrication and Characterization

Electrically conductive nanofibrous meshes composed of polypyrrole, polycaprolactone and gelatin construct using a two-step approach including electrospinning and in situ polymerization. Nanometer-scale thick polypyrrole (PPy) is grown on the surface of electrospun polycaprolactone-gelatin (PCL-Gel) nanofiber by in situ chemical polymerization. Different PCL-to-gel ratios and fiber orientations are employed to construct template scaffolds for the coating reaction. SEM analysis indicates the fiber diameter of 162–207 nm and the coating thickness of 30–93 nm. Porosity estimation confirms conservation of total porosity in the coated mats. ATR-FTIR of the composite reveals that functional groups of all three polymers partially exist on the surface. Furthermore, XRD analysis verifies the crystalline nature of the hybrid scaffold. High electrical conductivity (4.6–5.8 S/cm) and convenient mechanical properties of the coated membranes are further achieved. The collective information of the current investigation introduces suitable potential candidates for diverse biomedical applications.

Environmental impacts and mechanical properties of lightweight concrete containing bauxite residue (red mud)

Bauxite residue (Red mud) is one of the industrial caustic waste materials obtained from alumina production. Because of high annual production, it requires high costs and vast landfills to dispose it. In addition, due to high alkalinity, disposal of red mud (RM) may cause serious environmental problems. Considering use of concrete beside economic and environmental issues of cement production, replacing cement by industrial waste seems inevitable. In this study, RM has been used as high as 25% replacement of cement mass in order to study the performance of this waste material on lightweight concrete (LWC) in terms of their mechanical properties, global warming potential (GWP), cumulative energy demand (CED) and major criteria air pollutants (CO, NOX, Pb, SO2). For the quantification of overall environmental impacts of LWC production, a life-cycle assessment (LCA) approach has been conducted. The results indicated that RM can be used to produce LWC with convenient mechanical properties and densities of 1685–1789 (kg/m3). Moreover, the environmental impacts of LWC incorporating 25% of RM reduced in terms of CED, GWP, CO, NOX, Pb and SO2. Consequently, reusing RM waste which is otherwise disposed in landfills is an environmental-friendly alternative.

Synthesis, Characterization and Properties of Nitropolybutadiene as Energetic Plasticizer for NHTPB Binder

The nitration of low molecular weight polybutadiene (PB) by a convenient and inexpensive procedure was investigated. To retain the unique physico-chemical properties of the plasticizer, it was nitrated to an extent of 10 % double bonds. The product nitropolybutadiene (NPB) was characterized by FT-IR and 1H NMR spectroscopy as well as GPC, DSC, and TGA methods. The kinetic parameters for the decomposition of NPB from room temperature to 400 °C were obtained from non-isothermal DSC. The changes in glass transition temperature (Tg) and inert uncured binder systems were used for determination of its efficiency as plasticizer. NPB was used in cured and unfilled nitro-hydroxyl terminated polybutadiene (NHTPB) binder. Isothermal thermogravimetric analysis (Iso-TGA) was employed to determine the migration rate in cured and unfilled HTPB binder systems compared to the dioctyladiphate (DOA) plasticizer. It was found that the exudation of the NPB plasticizer is slower than that of the DOA plasticizer. Thus, the NHTPB/NPB binder system (binder/plasticizer) presents more convenient mechanical properties than HTPB/DOA and is a promising new energetic binder system for polymer bonded explosives.

Twinning-detwinning assisted reversible plasticity in thin magnesium wires prepared by one-step direct extrusion

The present study examines the micromechanisms of plastic deformation in magnesium wires with diameters of 250μm, which were prepared by one-step direct extrusion with a high reduction ratio of 576:1 at a temperature of 577K. It is shown that small wire diameter combined with appropriate microstructure (grain size 14±2μm and strong texture) can yield convenient mechanical properties even in pure Mg. Reversible bending plasticity is achieved by abundant 101̅2 twinning-detwinning of selected variants in the compression zone and moderate dislocation activity in the tensile zone of bended wires. The 101̅2 twinning during bending is facilitated by the medium grain size and by the strong texture with the c-axis of grains roughly perpendicular to the extrusion direction. Intense or repeated plastic bending of wires results in twinning-induced grain refinement in the compression zone. Tensile tests conducted at room temperature and at strain rates of 10−3 and 10−1s−1 reveal maximum true stresses of 198±2 and 246±4MPa and ductility values of 10 and 8%, respectively. In contrast with bending, tensile deformation of wires almost exclusively includes dislocation mechanisms, and a minor contribution of any twinning mode is observed.

Influence of different reinforcing particles on the scratch resistance and microstructure of different WC–Ni composites

WC composites are largely used in many engineering and industrial fields such as mining, cutting tools, and underground works. This interest in WC materials is related to their high wear resistance due to their convenient mechanical properties and controllable microstructures. However, the abrasive behavior of WC materials is very complicated because they are formed from several phases and their damage mechanism involves numerous parameters and factors that may be related to the composites themselves and the external environment. Reinforcing particles play a critical role in the achievement of wear-resistant materials. In this study, the impact of the presence of different types of reinforcing particles in the chemical makeup of WC–Ni composites on their resistance to scratch formation is highlighted through experimental abrasion tests by a single diamond tip.

Improving Magnetooptical Faraday Effect of maghemite/silica nanocomposites

The present work is focused on the evaluation and characterization of the Magnetooptical Faraday Effect (MOFE) of sol–gel processed composites consisting of maghemite iron oxide nanoparticles embedded in a silica xerogel matrix. These materials are of great interest mainly for magnetic-field sensing applications because of their high MOFE response, even at low magnetic fields. We have implemented an in-situ approach for the composite processing in which nanoparticles precursor are formed while host matrix polymerization and subsequent annealing steps leads to γ-Fe2O3 nanocrystals growth inside the porous xerogel framework. The samples thus obtained are reddish monoliths showing convenient mechanical properties. This method allows obtaining, with carefully controlled preparation conditions, materials with reproducible mechanical, magnetic and optical properties. It is shown that an additional processing step in which the samples were subjected to thermal oxidation treatment in air, leads to an enhancement more than 10 times in the sample optical transmittance, in comparison with the values of the untreated samples. The study of the magnetooptical behavior of these materials reveals a rather high Faraday rotation, as well as a reproducible and practically reversible linear range at low magnetic fields.

From a clinical observation of chronic wound microbiology to the elaboration of an anti-biofilm dressing: The PANSaBIO project strategy

The PANSaBIO project aims to evaluate the prevalence of biofilms on a large panel of chronic wounds (more than 100 samples) and relate its presence to the type and history of the wound and its microbiology. A large file computing all the data is under construction. Moreover, several strategies to prepare an innovative anti-biofilm dressing have been developed. On one hand, antimicrobial peptides were grafted to gelatin; the modified protein can be used to prepare an active dressing. Second, various antiseptics were entrapped in a gelatin gel. An adaptation was necessary to obtain the convenient mechanical properties of the gel. Then this preparation was turned to a dressing. A first generation of dressings efficient against biofilms of Pseudomonas aeruginosa and Staphylococus aureus is available today.

Load Carrying Elements and Structural Modular Systems Made of Synthetic Fibres Reinforced Mineral Matrix Composite

The use of recyclable materials is a priority for the construction industry aiming to a sustainable development. Recent works have shown that calcium sulphate in the β anhydride III form which is a hydraulic binder manufactured from industrial wastes can partially replace ordinary Portland cement in construction elements. Alkali resistant glass fibres can be used as reinforcement for ecological mineral matrix in order to obtain a mineral composite material. In the framework of an extensive research program, load carrying elements and structural modular system entirely made of mineral composite material were designed, developed, tested, analyzed and implemented. The paper presents the selection of efficient mixes for a mineral matrix with convenient mechanical properties, good workability and encouraging prospects to be implemented in construction elements and full structural systems. The experimental work carried out confirms the suitability of this material for load bearing elements and modular building systems.

IR Reflectivity Change from Electroactive IPN

A promising alternative of multi-layered devices showing electrochromic properties results from the design of a self-supported semi-interpenetrating polymer network (semi-IPN) including an electronic conductive polymer (ECP). The formation of the ECP in the network has already been described by oxidative polymerization using iron trichloride as an oxidant and leading to conducting semi-IPN with mixed electronic and ionic conductivities as well as convenient mechanical properties. This work relates to the elaboration of such semi-IPN using a PEO/NBR (Nitrile Butadiene Rubber) IPN in which a linear poly (3, 4-ethylenedioxythiophene) (PEDOT) is formed symmetrically and selectively as thin layers on the two sides of the film matrix. PEO/NBR/PEDOT semi-IPNs lead to interesting optical reflective properties in the IR between 0.8 and 25 μm. Reflectance contrasts up to 35% are observed when, after swelling in an ionic liquid, a low voltage is applied between the two sides of the film. The PEO/NBR IPN as a thin film possesses both a good flexibility and a good resistance against thermal ageing compared with a single PEO network previously employed. Moreover, the combination of NBR and PEO in an IPN leads to materials possessing a good ionic conductivity at 25°C. Finally, NBR/PEO/PEDOT semi-IPNs allow observing comparable reflectance contrast in the IR range than those previously shown by PEO/PEDOT semi-IPNs.