195 research outputs found
Conductive ceramic-carbon nanotube composites
No full textPowder metallurgy offers great and obvious potential for nano-enhancement, since nanomaterials can be readily incorporated. Fawad Inam of Nanoforce, one of the UK Technology Strategy Board's nanotechnology facilities based at Queen Mary College, is working on the manufacture of electrically conducting ceramics. As Inam explained at the event, spark plasma sintering is a new process that can produce materials from powder, such as alumina reinforced with containing carbon nanotubes. This opens the door to making high-performance ceramic material that is electrically and thermally conducting. Potential applications include spacecraft heat shields, armour, bio-inert ceramics and functionally graded materials
The effect of methanol exposure on the flexural and tensile properties of halloysite nanoclay/polyester
No full textIn this study, halloysitenanoclay reinforced polyester composites were prepared by adding different weight percentage in unsaturated polyester resin and subsequently cross linked using mixture of methyl ethyl ketone peroxide. The effect of methanol immersion on the flexural strength and tensile strength of polyester halloysite nanoclay was experimentally investigated. After 30 minutes of immersion in methanol, samples were tested and analysed. From the experimental results, flexural and tensile properties of halloy sitenanoclay/polyester decreased as a result of methanol reactionon the polymer composites. Keywords—Polyester composites, Halloysitenanoclay, Effect of Methanol, Mechanical Properties
Oxidation of alcohols using CoFe204@APTES@Ni(OH)2
No full textOxidation of alcohols using CoFe204@APTES@Ni(OH)2 was characterised by AAS, FT-IR, UV/Vis, XRD, TEM, FESEM, N2 adsorption, and VSM analyses. The catalyst was recovered by magnetic separation and reused four times without significant loss of catalytic activity
Structural health monitoring capabilities in ceramic – carbon nanocomposites
No full textA novel method for analysing structural health of alumina nanocomposites filled with graphene nanoplatelets (GNP), carbon nanotubes (CNTs) and carbon black nano-particles (CB) is presented. All nanocomposites were prepared using novel colloidal processing and then by Spark Plasma Sintering. Good homogeneous dispersion was observed for all carbon filled materials. Nanocomposite bars were indented to produce sub-surface damage. Change in electrical conductivities were analysed after indentation to understand structural damage. For correlating change in electrical conductivity and indentation damage and understanding damage tolerance, mechanical properties were compared. Because of the systematically induced indentation damage, a sharp decrease of 86% was observed in the electrical conductivity of CNT nanocomposite as compared to 69% and 27% in the electrical conductivities of GNP nanocomposites and CB nanocomposites respectively. CNTs impart superior damage sensing capability in alumina nanocomposites, in comparison to GNP and CB, due to their fibrous nature, high aspect ratio and high electrical conductivity
Novel synthesis of CNTs-Si3N4/Cu nanocomposites: electroless deposition, powder metallurgy, spark plasma sintering, microstructure, and physical properties
No full textIntroduction Metal matrix composites reinforced with ceramic and carbon nanotubes (CNTs) are considered recently as new materials for thermal managements and heat sink applications of electronic components.Method Cu nanocomposites reinforced with CNTs and different content of Si3N4 up to 5 wt.% (CNTs-xSi3N4/Cu) are synthesized by electroless Cu deposition process. The produced (CNTs-xSi3N4/Cu) nanocomposites powder were divided into two groups of samples. The first group were consolidated by two steps of cold pressing at 600 MPa compaction pressure followed by sintered under Ar atmosphere at 850 degrees C for 90 min. However, the second group of powders are spark plasma sintered (SPS) under vacuum by simultaneously applying compaction pressure of 50 MPa at sintering temperature of 850 degrees C for one min. The microstructure and the chemical composition of the investigated CNTs and the produced CNTs-xSi3N4/Cu powders as well as the CNTs-xSi3N4/Cu sintered nanocomposites were investigated by FTIR, SEM, TEM, EDX, X-ray mapping and XRD. The sinterability of the produced CNTs-xSi3N4/Cu nanocomposites is evaluated by measuring the Archimedes' density and the coefficient of thermal expansion (CTE).Results and discussion The electroless coating process enhancing the homogeneous distribution of CNTs and Si3N4 reinforced particles in the Cu matrix by preventing the formation of the agglomerations and segregations in the Cu matrix and retaining the nanostructure. The density and the CTE of the obtained CNTs-xSi3N4/Cu nanocomposites were improved by consolidation with SPS. The CNTs-xSi3N4/Cu nanocomposites sintered by SPS process have higher relative density approaches 100 % and lower CTE of 1.8 x 10-5 degrees C-1-1.6 x 10-5 degrees C-1 than, the density of the CNTs-xSi3N4/Cu nanocomposites sintered by conventional powder metallurgy technique with relative sintered density approaches 85 % and CTE of 2.6 x 10-5 degrees C-1-1.9 x 10-5 degrees C-1. Our findings owing that; the produced CNTs-Si3N4/Cu nanocomposites are expected as suitable candidate materials for thermal managements and heat sink packaging materials of electronic components.
Modeling and simulation of graphene based polymer nanocomposites: advances in the last decade
No full textModeling and simulation allow methodical variation of material properties beyond the capacity of experimental methods. The polymers are one of the most commonly used matrices of choice for composites and have found applications in numerous fields. The stiff and fragile structure of monolithic polymers leads to the innate cracks to cause fracture and therefore the engineering applications of monolithic polymers, requiring robust damage tolerance and high fracture toughness, are not ubiquitous. In addition, when “many-parts” cling together to form polymers, a labyrinth of molecules results, which does not offer to electrons and phonons a smooth and continuous passageway. Therefore, the monolithic polymers are bad conductors of heat and electricity. However, it is well established that when polymers are embedded with suitable entities especially nano-fillers, such as metallic oxides, clays, carbon nanotubes, and other carbonaceous materials, their performance is propitiously improved. Among various additives, graphene has recently been employed as nano-filler to enhance mechanical, thermal, electrical, and functional properties of polymers. In this review, advances in the modeling and simulation of grapheme based polymer nanocomposites will be discussed in terms of graphene structure, topographical features, interfacial interactions, dispersion state, aspect ratio, weight fraction, and trade-off between variables and overall performance
Novel synthesis of Al2O3 short fibers/Ti-12Mo-6Zr composites for cranial reconstruction applications: spark plasma sintering, microstructure and nanomechanical properties
No full textCeramic-Titanium matrix composites have recently attracted significant interest as a new type of biomaterials protecting the brain from external force and infections of cranial defects due to its biocompatibility and good mechanical and corrosion properties matched with the bone tissue. Spark plasma sintering (SPS) is one of powder technology techniques that can be utilised in the fabrication of final net complex and irregular shape parts used for cranial reconstruction and maxillofacial trauma by reconstruction and cranioplasty. The present work studies the effect of alumina (Al2O3) short fibers reinforcement addition on the nanomechanical properties estimated by the nanoindentation measurements of the Ti-12Mo-6Zr and its correlation with the microstructure. Al2O3 short fibers/Ti-12Mo-6Zr of different Al2O3 reinforcement short fibers content up to 5 wt.% were fabricated by Spark Plasma Sintering technique. Powders of Ti, Mo, and Zr powders were mechanically wet milled with different wt.% of Al2O3 reinforced short fibers. The mechanically mixed Al2O3 short fibers/Ti-12Mo-6Zr samples of different compositions were consolidated by SPS at 1000 oC for 5 min under vacuum and 50 Mpa compaction pressure. Optical microscopy (OM), high-resolution scanning electronic microscopy (HRSEM) conducted with Electron dispersive spectroscopy (EDAX) unite and X-Ray Diffraction (XRD) are used to evaluate the particle size and shape, surface morphology, microstructure, the chemical compositions and the phase identifications for the investigated samples. The samples were determined by the rule of mixture (ROM) as well as the Archimedes' principle. The nanomechanical properties were estimated by measuring the nanoindentation of the produced Al2O3 short fibers/Ti-12Mo-6Zr sintered samples using a Berkovich indenter with continuous stiffness measurement (CSM) method. The hardness and the Young modulus were estimated from the obtained data of the applied load-displacement in the depth curves. The obtained Al2O3 short fibers/Ti-12Mo-6Zr composites have good mechanical properties which revealed the efficiency of the sintering process by spark plasma sintering. Also, the estimated hardness and Young's modulus are increased by increasing the content of the Al2O3 reinforcement nanoparticles from 1 to 5 wt.% in the Ti-12Mo-6Zr metal matrix. Based on our findings of the nanoindentation studies; it was expected that the produced Al2O3 short fibers/Ti-12Mo-6Zr new composites have appropriate physical and mechanical properties for cranial reconstruction applications.
A quasi-3D theory for vibration and buckling of functionally graded sandwich beams
No full textThis paper presents a finite element model for free vibration and buckling analyses of functionally graded (FG) sandwich beams by using a quasi-3D theory in which both shear deformation and thickness stretching effects are included. Sandwich beams with FG skins-homogeneous core and homogeneous skins-FG core are considered. By using the Hamilton’s principle, governing equations of motion for coupled axial-shear-flexural-stretching response are derived. The resulting coupling is referred to as fourfold coupled vibration and buckling. Numerical examples are carried out to investigate the thickness stretching effect on natural frequencies and critical buckling loads as well as mode shapes of sandwich beams for various power-law indexes, skin-core-skin thickness ratios and boundary conditions
Re-agglomeration of carbon nanotubes in two-part epoxy system; influence of the concentration
No full textCarbon nanotubes, because of their exceptional mechanical properties, are one of the potential reinforcements for polymers in near future. Before substituting these nanocomposites in commercial applications, there are many problems, like dispersion, agglomeration, cost effectiveness etc., which need to be sorted. Processing such nanocomposites for longer durations is quite frequently observed these days. Apart from the other major obstacles, re-agglomeration, because of strong van der walls forces between carbon nanotubes, is one of the latest problems that has been always underestimated and ignored. In this study, different carbon nanotubes (Single-wall nanotubes (SWNT), Double wall nanotubes (DWNT), Amino-modified double wall nanotubes (DWNT-NH2), Thin Multi wall nanotubes (MWNT) and COOH-modified thin multi wall nanotubes (MWNT-COOH)) at different concentrations (0.025, 0.05 and 0.1 %wt) in two-part epoxy system (Liquid Epoxy, Liquid hardener and Liquid epoxy-hardener mixture) were studied involving nano-particle size analyzer. After a study of 3 hours, it was observed that there is a strong dependence of re-aggregation profile on the employed homogenizing technique, i.e. high-power bath ultrasonication in this study. Apart from nanotubes/epoxy mixture, higher concentrations yielded higher aggregates profile and vice versa. Re-agglomeration, with the passage of time, in liquid epoxy was found to be least as compared to liquid hardener and liquid epoxy-hardener mixture. Hardener in liquid-epoxy mixture was the main culprit responsible for re-aggregation. Results were further verified by scanning electron microscopy, which revealed significant differences in the microstructures of the cured and fractured samples. Suggestions for altering processing parameters in order to avoid this major obstacle are discussed
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