Phani Kumari Paritala; Tejasri Yarlagadda; Jessica Benitez Mendieta; Jiaqiu Wang; YuanTong Gu; Zhiyong Li; Prasad K.D.V. Yarlagadda
Abstract
Cardiovascular diseases (CVD) are the leading causes of morbidity and mortality globally. Atherosclerosis is a chronic inflammatory CVD associated with the accumulation of plaque activated by the complex interactions between systemic, hemodynamic and biological factors. Thus, identification of plaque ...
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Cardiovascular diseases (CVD) are the leading causes of morbidity and mortality globally. Atherosclerosis is a chronic inflammatory CVD associated with the accumulation of plaque activated by the complex interactions between systemic, hemodynamic and biological factors. Thus, identification of plaque vulnerability is essential for the prevention of acute events and treatment of the disease. Despite, advanced imaging technologies, patient-specific computational simulations and availability of experimental data, there are still challenges in developing accurate risk stratification techniques. Therefore, this study aims to characterize the carotid plaque components structurally (histological analysis and immunostaining), mechanically (Nanoindentation tests) and chemically (Fourier Transform Infrared (FT-IR) micro-spectroscopy). The preliminary results showed that arterial remodelling is a dynamic interaction between mechanical forces and plaque progression. The biological content and composition of human atherosclerotic plaque tissue have been shown to significantly influence the mechanical response of samples. This data represents a step towards an enhanced understanding of the behaviour of human atherosclerotic plaque. Future large-scale experimental studies with more cross-sections along the length of the plaque could be used to develop a risk stratification technique.
Jazmín I. González; Diana M. Escobar; Claudia P. Ossa
Abstract
Hydroxyapatite is one of the appropriate materials for hard tissue engineering because it is the inorganic structural constituent of bones and teeth, and hydroxyapatite has been evaluated to compare the mechanical properties, processing as scaffolds to evaluate the influence of porosity, since the elastic ...
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Hydroxyapatite is one of the appropriate materials for hard tissue engineering because it is the inorganic structural constituent of bones and teeth, and hydroxyapatite has been evaluated to compare the mechanical properties, processing as scaffolds to evaluate the influence of porosity, since the elastic modulus of material is influenced by the porosity, it is essential to establish a relationship between the two characteristics to obtain a material with optimum conditions for its implantation. The main objective of this research was to study the mechanical properties of hydroxyapatite scaffolds using compression and nanoindentation tests. The scaffolds were manufactured by gel-casting and gel-casting combined with foam polymer infiltration, in both cases 40 and 50% solids and three different monomers were used. The samples obtained by gel-casting exhibited a compressive strength between 0.93 and 6.15 MPa, an elastic modulus between 11.46 and 27.27 GPa; some of these scaffolds showed very similar values to human trabecular bone reported. In addition, samples produced by gel-casting combined with foam polymer infiltration, it was found that compressive strength was between 0.05 and 0.12 MPa, the elastic modulus between 1.61 and 6.24 GPa, concluding that the gel-casting produces scaffolds with closest to trabecular bone.
Kaleem Ahmad Najar; Nazir Ahmad Sheikh; M. A. Shah
Abstract
In the present work, smooth boron-doped (BD) and undoped multilayered diamond coating systems (MDCS) with top layer nanocrystallinity were deposited on chemically etched cemented tungsten carbide (WC-6%Co) substrates, using hot filament chemical vapour deposition (HFCVD) technique. Both coatings were ...
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In the present work, smooth boron-doped (BD) and undoped multilayered diamond coating systems (MDCS) with top layer nanocrystallinity were deposited on chemically etched cemented tungsten carbide (WC-6%Co) substrates, using hot filament chemical vapour deposition (HFCVD) technique. Both coatings were accomplished by combining the alternate thin films of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) with a transition layer (TL) of ~1μm thick, using predetermined process parameters during the deposition process. The effects of boron doping on the residual stresses (σ), hardness (H) and coefficient of friction (COF) of MDCS were analyzed using Raman spectroscopy, Berkovich Nanoindenter and Micro-tribometer, respectively. The comparison has been documented between BD-MDCS with undoped one, under same input operating conditions and within same atmospheric conditions. The frictional characteristics were studied under the application of increasing normal load when sliding against smooth alumina (Al2O3) ceramic counter ball for the total duration of 20 min, within dry sliding conditions. The average values of COF of undoped-MDCS and BD-MDCS decrease from ~0.30 – 0.27 and ~0.28 – 0.25, respectively under the application of 1 – 10 N loads. Also, the average values of indentation depths for undoped-MDCS and BD-MDCS were ~65 nm and ~70 nm, with average hardness values in the range of ~65 – 80 GPa and ~55 – 75 GPa, respectively. Therefore, depositing smooth, adhesive and thick BD-multilayered diamond coatings on cemented tungsten carbide components would certainly enable its many useful future applications in mechanical industry.
Ravi Prakash; R. Jayaganthan;Davinder Kaur
Abstract
Chromium tungsten nitride (Cr1-xWxN) thin films were successfully deposited on the silicon (100) substrate using dc magnetron reactive co-sputtering. The structural, surface morphological, electrochemical and mechanical properties were studied using X-ray diffraction, field emission-scanning electron ...
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Chromium tungsten nitride (Cr1-xWxN) thin films were successfully deposited on the silicon (100) substrate using dc magnetron reactive co-sputtering. The structural, surface morphological, electrochemical and mechanical properties were studied using X-ray diffraction, field emission-scanning electron microscopy, atomic force microscopy, electrochemical potentiostat and nanoindentation respectively. X-ray diffraction pattern with different atomic concentrations of tungsten (0<x<0.61) shows the presence of (111) and (200) orientation. The content of tungsten (W) in these thin films was controlled by varying the power on the W target. A small amount of tungsten addition led to the significant change in the structural, electrochemical and mechanical properties of the Cr1-xWxN films. The crystallite size varies from 31.1 nm to 15.2 nm with the W content due to variation in nucleation rate and reduction of the self-shadowing effect of the deposition process. Electrochemical properties of these thin films were studied by Tafel polarization curves, which explored the enhancement in corrosion rate due to the higher ratio of real surface area and projected area after a certain amount of W addition. Hardness follows the Hall-Petch relation and tends to increase with the decrease in grain size. Highest hardness 43.18 Gpa and elastic modulus 341.02 Gpa were achieved at the grain size of 15.2 nm in Cr0.48W0.43N thin film.
Nicola M. Everitt; Nesma T. Aboulkhair; Ian Maskery; Chris J. Tuck; Ian Ashcroft
Abstract
Single track and single layer AlSi 10Mg has been produced by selective laser melting (SLM) of alloy powder on an AlSi12 cast substrate. The SLM technique produced a cellular-dendritic ultra-fined grained microstructure. Chemical composition mapping and nanoindentation showed higher hardness in the SLM ...
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Single track and single layer AlSi 10Mg has been produced by selective laser melting (SLM) of alloy powder on an AlSi12 cast substrate. The SLM technique produced a cellular-dendritic ultra-fined grained microstructure. Chemical composition mapping and nanoindentation showed higher hardness in the SLM material compared to its cast counterpart. Importantly, although there was some increase of grain size at the edge of melt pools, nanoindentation showed that the hardness (i.e. yield strength) of the material was uniform across overlapping tracks. This is attributed to the very fine grain size and homogeneous distribution of Si throughout the SLM material.
Zdenka Prochazkova; Vlastimil Kralik; Jiri Nemecek; Michal Sejnoha
Abstract
Introduction of recycled plastic materials in structural applications such as bridges, retaining walls or railway sleepers requires a proper identification of necessary material properties. Given similarities in the microstructure of various structural elements we limit our attention to beams having ...
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Introduction of recycled plastic materials in structural applications such as bridges, retaining walls or railway sleepers requires a proper identification of necessary material properties. Given similarities in the microstructure of various structural elements we limit our attention to beams having a rectangular cross-section. Owing to the manufacturing process the cross-section is represented by a porous-core (inner section) surrounded by a homogeneous material (outer section). The influence of microstructural details on material parameters is examined here with a reference to the elastic Young’s modulus derived from nanoindentation measurements. To identify a gradual evolution of the stiffness of plastic material from the outer section into the core the grid indentation method based on the statistical evaluation of a large number of indentations was adopted. These tests were accompanied by standard static indentation measurements to address also the effect of temperature in the range of 20–40°C. When dealing with these types of recycled plastics, even a 5°C temperature variation leads to a significant change in the material stiffness. In addition, standard macroscopic material properties were measured by tensile tests of samples with and without the porous core and compared with microscopic parameters. The elastic modulus obtained from nanoindentation was found to be ~20 % higher than that provided by the tensile tests.
Minh-Tai Le;Shyh-Chour Huang
Abstract
The main objective of this work is to conduct a manufacturing experiment on a single-walled carbon nanotube (SWCNT)/polyester nanocomposite for characterization of its mechanical properties using a tensile test and nanoindentation techniques. Experimental specimens were made under identical conditions ...
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The main objective of this work is to conduct a manufacturing experiment on a single-walled carbon nanotube (SWCNT)/polyester nanocomposite for characterization of its mechanical properties using a tensile test and nanoindentation techniques. Experimental specimens were made under identical conditions using the hot press process. Dispersion of SWCNTs in an unsaturated polyester matrix was conducted by a sonication method, and a high-speed shear mixer was used for mixing the curing agent and resin. Following the manufacturing of the SWCNT/polyester nanocomposites, characterization of the mechanical properties of the material was performed by tensile testing and nanoindentation techniques. In addition, the morphologies of the fractured surface of SWCNT/polyester nanocomposites were observed with a scanning electron microscope (SEM). The results of mechanical tests exhibit improvements of Young’s modulus and hardness by 35% and 29%, respectively, at 1.0 wt% SWCNTs. In addition, the elastic modulus determined by the nanoindentation technique differs from the one obtained from tensile tests by 16%. The experimental samples are expected to yield the novel promising materials that offer a low-cost, high-strength material for use in the manufacture of lightweight components for automobiles, transportation systems and consumer products.
Sanjay Thorat; Alberto Diaspro; Marco Salerino
Abstract
A photo-polymerizable resin based on bisphenol-A-glycidyldimethacrylate monomer was loaded at both 10 and 50% by weight with particles of alumina of size scales in the 10 micrometers and submicrometer order, termed micro-alumina and nano-alumina, respectively. After curing, the viscoelastic properties ...
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A photo-polymerizable resin based on bisphenol-A-glycidyldimethacrylate monomer was loaded at both 10 and 50% by weight with particles of alumina of size scales in the 10 micrometers and submicrometer order, termed micro-alumina and nano-alumina, respectively. After curing, the viscoelastic properties of these materials were characterized by multifrequency dynamic mechanical analysis at 0.1, 1 and 10 Hz, carried out in bending mode under strain control across the range of temperatures of 2 to 62°C, normally occurring in the mouth. The storage moduli close to body temperature (37°C) and mastication frequency (1 Hz) was evaluated as the main result of the analysis, along with its change on frequency. The stiffest composite was the 50%wt loaded nano-alumina, which reached a modulus of ~6.8 GPa, comparable to those of commercial restorative composites, even in the absence of bonding agent coating of the fillers. The storage moduli at the same frequency but room temperature (25°C) were compared with the elastic modulus resulting from atomic force microscopy nanoindentation. These measurements confirmed the same ranking of materials as the dynamic flexural analysis, while providing elastic modulus values ~50% higher on average. From the dynamic analysis no thermal transition was observed in the considered temperature range, and a stiffening effect appeared at higher frequencies for all the composites.
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