Damping properties of epoxy-based composite embedded with sol–gel-derived Pb(Zr 0.53 Ti 0.47 )O 3 thin film with different thicknesses

Pb(Zr $_{\mathbf{0\boldsymbol{\cdot}53}}$ Ti $_{\mathbf{0\boldsymbol{\cdot}47}})$ O ₃ (PZT) thin films were prepared on Pt/Ti/SiO ₂ /Si substrate by sol?Cgel method. The effect of film thickness on microstructure, ferroelectric and dielectric properties was investigated. The single-phase PZT films were obtained with different thicknesses. PZT films with a thickness of 190?C440?nm had better dielectric and ferroelectric properties. The epoxy/PZT film/epoxy sandwiched composites were prepared. The thickness of PZT films influenced their damping properties of the composites, and the epoxy-based composites embedded with 310?nm-thick PZT films had the largest damping loss factor of 0 $\boldsymbol{\cdot} $ 915.     

Effect of Iron Particle Size and Concentration on Thermal Conductivity of Iron/Polystyrene Composites

The present study deals with the thermal conductivity of iron/polystyrene (PS) composites containing iron particles of different sizes: (5, 50, 150, and 250)  $\upmu \mathrm{m}$ , and with different iron concentrations: (0, 5, 10, 20 and 30) mass%. The effects of iron particle size and concentration on the thermal conductivity of iron/PS composites are investigated in the temperature range: (30 to 120)  $^{\circ }\mathrm{C}$ . It was found that the addition of ultrafine iron particles enhances the thermal conductivity of the composites more than that of larger (coarser) particles. The thermal conductivity also increases with increasing temperature and iron concentration. The glass transition temperature was found to increase with decreasing size of iron particles. A correlation between the observed electrical and thermal conductivities of the iron composites as a function of iron particle size is presented. Fitting of some theoretical models results in predictions of smaller values of the thermal conductivity than are the experimental values.     

Contact models based on experimental characterization of irregular shaped,micrometer-sized particles

The goal of this study is to investigate experimentally the mechanical contact properties of fine particles ( \(<\) 120  \(\upmu \) m) using of a novel experimental setup. On the basis of deformation curves from compression tests, particle behaviour under mechanical stress can be approximated with theoretical contact models. Models examined in this study include Walton and Braun, Tomas and Antonyuk, Zener and Thornton. Influence of climatic conditions on particle behaviour as well as hardening effects related to cyclic loading were also considered. Maltodextrin was used as a model substance for primary particles, while irregular shaped titanium dioxide granules were used to study the behaviour of agglomerates. In both cases, results are in good agreement with the established theories.     

Hydroxyapatite, a biomaterial: Its chemical synthesis, characterization and study of biocompatibility prepared from shell of garden snail, Helix aspersa

The shell of garden snail (Helix aspersa) is basically made of calcium carbonate. An attempt is made to convert calcium carbonate of garden snail shell to hydroxyapatite. The snail shell was found to decompose within 850 $^{\circ}$ C to all the carbonate phases. The calcined snail shells were then treated with acids followed by different chemicals in ammoniacal media maintaining proper stoichiometry to produce fine hydroxyapatite (HAP) as filter cake with a Ca $/$ P molar ratio of 1 ${\cdot }$ 67. The dried HAP powder was extremely pure with a specific surface area of 15 m $^{\bf 2}/$ g. The different characterization techniques were adopted both for calcined snail shell and HAP synthesized by X-ray diffraction (XRD), thermal analysis (DTA $/$ TGA), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The surface area and particle size of HAP powder prepared by chemical precipitation route, were also determined by BET and Malvern particle size analyser, respectively. The synthesized powder was soaked in stimulated body fluid (SBF) medium for various periods of time in order to evaluate its bioactivity. The changes of pH of SBF medium were measured. High bioactivity of prepared HAP powder due to the formation of apatite on its surface was observed.     

Elastic Properties Inversion of an Isotropic Plate by Hybrid Particle Swarm-Based-Simulated Annealing Optimization Technique from Leaky Lamb Wave Measurements Using Acoustic Microscopy

This paper presents a new method for the inversion of elastic properties of an isotropic thin plate by line-focus acoustic microscopy. Over 10 modes of the leaky Lamb waves of a 380  \(\upmu \) m thick aluminum plate were extracted by the \(V(f\) , \(z)\) measurement. The inversion method of hybrid particle swarm-based-simulated annealing (PS-B-SA) optimization induces an objective function dependent on the determinant of the coefficient matrix of the dispersive characteristic equation. PS-B-SA allows considerable flexibility in parametric inversion problem and seeks the global rather than the local minimum. An alternative image display method combined with the objective function will be used to show the dispersion curves and to demonstrate the principles of the PS-B-SA optimization algorithm. The elastic properties (Young’s modulus \(E\) , shear modulus \(G\) , Poisson’s ratio \(\nu \) ) and thickness (2 \(h)\) of the specimen are determined by the inversion of the dispersion curves. Inversed parameters by particle swarm optimization algorithm are compared with the PS-B-SA results to show the validity and stability of the hybrid method. Agreement between the inversed material parameters and the reported data is shown to be excellent.     

Investigation on effect of fibre hybridization and orientation on mechanical behaviour of natural fibre epoxy composite

Nowadays bio fibre composites play a vital role by replacing conventional materials used in automotive and aerospace industries owing to their high strength to weight ratio, biodegradability and ease of production. This paper aims to find the effect of fibre hybridization and orientation on mechanical behaviour of composite fabricated with neem, abaca fibres and epoxy resin. Here, three varieties of composites are fabricated namely, composite 1 which consists of abaca fibre and glass fibre, composite 2, which consists of neem fibre and glass fibre, whereas composite 3 consists of abaca, neem fibres and glass fibres. In all the above three varieties, fibres are arranged in three types of orientations namely, horizontal (type I), vertical (type II) and 45\(^{\circ }\) inclination (type III). The result shows that composites made up of abaca and neem fibres with inclined orientation (45\(^{\circ }\)) have better mechanical properties when compared with other types of composites. In addition, morphological analysis is carried out using scanning electron microscope to know the fibre distribution, fibre pull out, fibre breakage and crack propagation on tested composites.     

Structure-performance-fouling studies of polysulfone microfiltration hollow fibre membranes

Hollow fibre microfiltration membranes were prepared by solution spinning process using polymer dope containing different amounts of polysulfone (PS), polyvinylpyrollidone (PVP) and ${\bf \textit{N}}$ , ${\bf \textit{N}}$ -dimethylformamide (DMF). Spinning dope having PS: PVP: DMF (w/w) of 15: 5: 80, 15: 7: 78 and 17: 8: 75 were used for spinning to obtain hollow fibres having different dimensions (outer and inner diameters) and pore characteristics. Relatively high water permeability was observed for hollow fibre membrane spun from 15?wt.?% solution than 17?wt.?% PS solution having the same PVP/PS ratio of 0·47. Decrease of the PVP/PS ratio to 0·33 in the dope solution of 15?wt.?% PS solution produced hollow fibre membrane with lower flux. By changing the spinning parameters, fibre with different dimensions were obtained without a significant change in microstructural morphology. The flux decline due to fouling for the permeation of PEO/BSA solution was maximum for the hollow fibre membrane obtained from 15?wt.?% PS solution while a steady flux with slight fouling was observed for the hollow fibre membrane obtained from 17?wt.?% PS solution, when the PVP/PS ratio was 0·47.     

In situ ring-opening polymerization of hydroxyapatite/poly(ethylene adipate)-co-(ethylene terephthalate) biomimetic composites

Hydroxyapatite/poly(ethylene adipate)-co-poly(ethylene terephthalate) biomaterials (HAp/PEA-co-PET) have been prepared by ring opening polymerization (ROP) of cyclic oligo(ethylene adipate)-co-oligo(ethylene terephthalate) (C-OEA-co-C-OET) in the porous hydroxyapatite (HAp) scaffolds at 250 °C for 24 h under vacuum. The content of ROP-PEA-co-PET in the HAp/PEA-co-PET composite was about 20 wt% with the values of number average molecular weight $({\overline{M}_{{\rm n}}})$ and weight average molecular weight $({\overline{M}_{{\rm W}}})$ of 3380 and 7160 g/mol, respectively. Compressive strength and modulus of the HAp/PEA-co-PET composites were about 29 and 246 MPa, respectively. These mechanical properties were higher than those of the porous HAp templates and natural cancellous bone. In vitro bioactivity of the HAp/PEA-co-PET composites was studied by soaking in simulated body fluid (SBF) under the flowing system at the rate of 130 mL/day for 7, 14, 21 and 28 days. The formation of hydroxyapatite nanocrystals was observed on the composite surfaces through the consumption of calcium and phosphorus from the SBF solution, indicating the bioactivity of these HAp/PEA-co-PET composites. These results indicated the competency of HAp/PEA-co-PET composites for biomedical applications.     

Mechanical properties of inclined frictional granular layers

We investigate the mechanical properties of inclined frictional granular layers prepared with different protocols by means of DEM numerical simulations. We perform an orthotropic elastic analysis of the stress response to a localized overload at the layer surface for several substrate tilt angles. The distance to the unjamming transition is controlled by the tilt angle $\alpha $ with respect to the critical angle $\alpha _c$ . We find that the shear modulus of the system decreases with $\alpha $ , but tends to a finite value as $\alpha \rightarrow \alpha _c$ . We also study the behaviour of various microscopic quantities with $\alpha $ , and show in particular the evolution of the contact orientation with respect to the orthotropic axes and that of the distribution of the friction mobilisation at contact.     

Effect of rolling deformation and solution treatment on microstructure and mechanical properties of a cast duplex stainless steel

The present study deals with the effect of rolling deformation and solution treatment on the microstructure and mechanical properties of a cast duplex stainless steel. Cast steel reveals acicular/Widmanst?tten morphology as well as island of austenite within the $\boldsymbol\delta $ -ferrite matrix. Hot rolled samples exhibit the presence of lower volume percent of elongated band of $\boldsymbol\delta $ -ferrite ( $\boldsymbol\sim $ 40%) and austenite phase which convert into finer and fragmented microstructural constituents after 30% cold deformation. By the solution treatment, the elongated and broken crystalline grains recrystallize which leads to the formation of finer grains (<10? $\boldsymbol\mu $ m) of austenite. X-ray diffraction analysis has corroborated well with the above-mentioned microstructural investigation. Enhancement in hardness, yield strength and tensile strength values as well as drop in percent elongation with cold deformation increases its suitability for use in thinner sections. 30% cold rolled and solution treated sample reveals attractive combination of strength and ductility (25·22?GPa%). The examination of fracture surface also substantiates the tensile results. The sub-surface micrographs provide the potential sites for initiation of microvoids.     

Characterization and biocompatibility studies of new degradable poly(urea)urethanes prepared with arginine, glycine or aspartic acid as chain extenders

Polyurethanes are very often used in the cardiovascular field due to their tunable physicochemical properties and acceptable hemocompatibility although they suffer from poor endothelialization. With this in mind, we proposed the synthesis of a family of degradable segmented poly(urea)urethanes (SPUUs) using amino acids (l-arginine, glycine and l-aspartic acid) as chain extenders. These polymers degraded slowly in PBS (pH 7.4) after 24 weeks via a gradual decrease in molecular weight. In contrast, accelerated degradation showed higher mass loss under acidic, alkaline and oxidative media. MTT tests on polyurethanes with l-arginine as chain extenders showed no adverse effect on the metabolism of human umbilical vein endothelial cells (HUVECs) indicating the leachables did not provoke any toxic responses. In addition, SPUUs containing l-arginine promoted higher levels of HUVECs adhesion, spreading and viability after 7 days compared to the commonly used Tecoflex^® polyurethane. The biodegradability and HUVEC proliferation on l-arginine-based SPUUs suggests that they can be used in the design of vascular grafts for tissue engineering.     

Strain tensor determination of compressed individual silica sand particles using high-energy synchrotron diffraction

The three-dimensional X-ray diffraction (3DXRD) nondestructive technique was used to measure lattice strains within individual sand particles subjected to compressive loading. Three experiments were conducted on similar single columns of silica sand particles with particle sizes between 0.595 and 0.841 mm. In each experiment, three sand particles were placed inside an acrylic mold with an inner diameter of 1 mm. Multiple in situ 3DXRD scans were acquired for each sand column as compressive load was increased. The volume-averaged lattice strain tensor was calculated for each sand particle. In addition, particle orientation and volumetric strain were calculated for individual sand particles. The axial normal strain $\upvarepsilon _\mathrm{zz}$ ε zz exhibited a linear response in the range of 0 to $10^{-3}$ 10 ? 3 when the applied compressive axial load (F) increased from 0 to $\sim $ ～ 30 N when one particle in the sand column fractured. Stress tensor of individual particles was calculated from the acquired lattice strain measurements and elastic constants of silica sand that were reported in the literature. To the best of our knowledge, there have been no reported experimental measurements of the lattice strain tensor measurements within individual silica sand particles. The quantitative measurements reported in this paper at the particle level are very valuable for developing, validating or calibrating micromechanics-based finite element and discrete element models to predict the constitutive behavior of granular materials. 3DXRD represents an exciting new non-destructive technique to directly measure constitutive behavior at the scale of individual particles.     

On the automorphism group of a binary self-dual [120, 60, 24] code

We prove that an automorphism of order 3 of a putative binary self-dual $[120, 60, 24]$ [ 120 , 60 , 24 ] code $C$ C has no fixed points. Moreover, the order of the automorphism group of $C$ C divides $2^a\cdot 3 \cdot 5\cdot 7\cdot 19\cdot 23\cdot 29$ 2 a · 3 · 5 · 7 · 19 · 23 · 29 with $a\in \mathbb N _0$ a ∈ N 0 . Automorphisms of odd composite order $r$ r may occur only for $r=15, 57$ r = 15 , 57 or $r=115$ r = 115 with corresponding cycle structures $3 \cdot 5$ 3 · 5 - $(0,0,8;0), 3\cdot 19$ ( 0 , 0 , 8 ; 0 ) , 3 · 19 - $(2,0,2;0)$ ( 2 , 0 , 2 ; 0 ) or $5 \cdot 23$ 5 · 23 - $(1,0,1;0)$ ( 1 , 0 , 1 ; 0 ) respectively. In case that all involutions act fixed point freely we have $|\mathrm{Aut}(C)| \le 920$ | Aut ( C ) | ≤ 920 , and $\mathrm{Aut}(C)$ Aut ( C ) is solvable if it contains an element of prime order $p \ge 7$ p ≥ 7 . Moreover, the alternating group $\mathrm{A}_5$ A 5 is the only non-abelian composition factor which may occur in $\mathrm{Aut}(C)$ Aut ( C ) .     

Effect of substitution of sand stone dust for quartz and clay in triaxial porcelain composition

Quartz and kaolin were partially substituted by sand stone dust (a siliceous byproduct of Indian stone cutting and polishing industries) in a traditional triaxial porcelain composition consisting of kaolin, quartz and feldsper. The effect of substitution upon heating at different temperatures (1050–1150 $\boldsymbol{^\circ}$ C) were studied by measuring the linear shrinkage, bulk density, porosity and flexural strength. Qualititative phase and microstructural analysis on selected samples were carried out using XRD and SEM/EDX technique. The results show that the samples of all the batches achieved higher density (2 $\boldsymbol\cdot$ 50 g/cc) and almost full vitrification ( $\boldsymbol <$ 0 $\boldsymbol{\cdot}$ 1% apparent porosity) at around 1115 $\boldsymbol{^\circ}$ C compared to around 1300 $\boldsymbol{^\circ}$ C for traditional triaxial porcelain composition. As high as 70 MPa flexural strength was obtained in most of the vitrified samples. No significant variation in physico-mechanical properties was observed in between the composition. XRD studies on selected samples show presence of mainly quartz phase both at low and high temperatures. SEM photomicrographs of the 1115 $\boldsymbol{^\circ}$ C heated specimen show presence of quartz grain and glassy matrix. Few quartz grains (20–40 $\boldsymbol{\mu}$ m) are associated with circumferential cracks around them.     

A simple distinct element modeling of the mechanical behavior of methane hydrate-bearing sediments in deep seabed

The study on the mechanical behavior of methane hydrate-bearing sediments (HBS) in deep seabed is of great significance for the safe exploitation of methane hydrate in the future. Recent studies have shown that the mechanical behavior of HBS is significantly influenced by methane hydrate since it leads to cementation among soil grains. For better understanding its microscopic mechanical mechanism, this paper presents a simple numerical model of HBS using the distinct element method (DEM). First, a set of tests on two bonded aluminum rods were performed under different loading paths with a specially designed apparatus. Then, a simple bond contact model was proposed based on the experimental data and implemented into our two-dimensional DEM code, NS2D. Finally, a series of drained biaxial compression tests under different confining stresses on HBS samples with different bond strengths, which are used to represent different methane hydrate saturations $(S_{\mathrm{MH}})$ , were carried out with this code. By comparing the results of numerical simulations with the experimental data obtained from triaxial compression tests, the study shows that the DEM incorporating the new bond contact model is capable of capturing the main mechanical characteristics of HBS such as the strain softening and dilation. And it can also capture that (a) the peak shear strength increases as $S_{\mathrm{MH}}$ or the confining stress increases, while the dilation increases as $S_{\mathrm{MH}}$ increases or the confining stress decreases; (b) both the cohesion and friction angle increase with the increasing of $S_{\mathrm{MH}}$ , but the influence of $S_{\mathrm{MH}}$ on the cohesion is much more significant than on the friction angle.     

The Improved Superconducting Properties in the Ex-situ Sintered MgB_{2} Bulks with Mg Addition

The ex-situ method to prepare MgB \(_{2}\) superconductors is favorable in terms of bulk density compared to the in-situ method. Since the packing factor of ex-situ MgB \(_{2}\) is higher than that of in-situ MgB \(_{2}\) , a better \(J_{c}\) , even higher than that of in-situ, is naturally expected if strong grain connectivity is achieved. In the present work, ex-situ MgB \(_{2 }\) polycrystalline bulks with Mg addition were prepared by sintering. Combined with phase composition analysis, microstructure observation and superconducting properties measurement, it is found that Mg addition can obviously reduce MgO impurities, accelerate the self-sintering of MgB \(_{2}\) and even promote the formation of sintering necks between MgB \(_{2}\) grains. Consequently, the sintering density and grain connectivity is enhanced, and the \(J_{c}\) is improved across the whole magnetic field in the ex-situ MgB \(_{2}\) sample with Mg addition. Mg addition is a promising and effective way to further enhance \(J_{c}\) of ex-situ MgB \(_{2}\) superconductors.     

Photoacoustic Measurement of Thermal Properties of Co–Ni–Li Ferrite Nanoparticles

A simple home-made open photoacoustic cell is used for measuring some of the thermal properties of nanoparticles of $\mathrm{{Co}}_{0.5}\mathrm{{Ni}}_{0.5\text{-- }2{x}}\mathrm{{Li}}_x\text{ Fe }_{2+{x}}\mathrm{{O}}_{4}$ Co 0.5 Ni 0.5 -- 2 x Li x Fe 2 + x O 4 (with $x$ x ranging from 0.00 to 0.25 in steps of 0.05) prepared by the citrate precursor method. The influence of sintering temperatures on the thermal properties of a selected sample for $x=0.25$ x = 0.25 was also investigated. The thermal-diffusivity and thermal-effusivity measurements of the investigated samples are obtained by measuring the photoacoustic signal as a function of the modulated frequency depending on the existence of a reference sample. The thermal diffusivity of the as-prepared samples decreases as the $\mathrm{{Li}}^{1+}$ Li 1 + content increases except for the samples for $x=0.15$ x = 0.15 and $x=0.20$ x = 0.20 . These exceptions may be due to a better magnetic ordering in these samples leading to reduced phonon scattering and a higher thermal diffusivity. Finally, the thermal diffusivity of the sintered samples increases as the sintering temperature increases due to the increase in grain size.     

Behaviour of LaAlO3+LnTiTaO6 (Ln= Ce, Pr or Nd) dielectric ceramic mixtures

The 0·1LaAlO₃+0·9LnTiTaO₆ (Ln= Ce, Pr or Nd) ceramics are prepared through solid state ceramic route. The structure of the materials is studied using X-ray diffraction analysis. The microstructure is analysed using scanning electron microscopy. The dielectric properties in the radio as well as in the microwave frequencies are measured and discussed. The photoluminescence of a representative sample is also analysed. The dielectric constant ( $\varepsilon_{r})$ and temperature coefficient of resonant frequency ( $\tau_{f})$ are tailored without appreciable change in the quality factor. The measured values of $\varepsilon_{r}$ and $\tau _{f}$ are compared with the corresponding predicted values. These mixtures can be made useful in optical and microwave communication.     

Experimental Measurements of Thermophysical Properties of \mathrm{Al}_{2}\mathrm{O}_{3}– and \mathrm{TiO}_{2}–Ethylene Glycol Nanofluids

This paper presents measurements of the thermal conductivity and the dynamic viscosity of $\mathrm{Al}_{2}\mathrm{O}_{3}$ Al 2 O 3 –ethylene glycol and $\mathrm{TiO}_{2}$ TiO 2 –ethylene glycol (1 % to 3 % particle volume fraction) nanofluids carried out in the temperature range from $0\,^{\circ }$ 0 ° C to $50\,^{\circ }$ 50 ° C. The thermal-conductivity measurements were performed by using a transient hot-disk TPS 2500S apparatus instrumented with a 7577 probe (2.001 mm in radius) having a maximum uncertainty $(k=2)$ ( k = 2 ) lower than 5.0 % of the reading. The dynamic-viscosity measurements and the rheological analysis were carried out by a rotating disk type rheometer Haake Mars II instrumented with a single-cone probe (60 mm in diameter and $1^{\circ }$ 1 ° ) having a maximum uncertainty $(k=2)$ ( k = 2 ) lower than 5.0 % of the reading. The thermal-conductivity measurements of the tested nanofluids show a great sensitivity to particle volume fraction and a lower sensitivity to temperature: $\mathrm{TiO}_{2}$ TiO 2 –ethylene glycol and $\mathrm{Al}_{2}\mathrm{O}_{3}$ Al 2 O 3 –ethylene glycol nanofluids show a thermal-conductivity enhancement (with respect to pure ethylene glycol) from 1 % to 19.5 % and from 9 % to 29 %, respectively. $\mathrm{TiO}_{2}$ TiO 2 –ethylene glycol and $\mathrm{Al}_{2}\mathrm{O}_{3}$ Al 2 O 3 –ethylene glycol nanofluids exhibit Newtonian behavior in all the investigated temperature and particle volume fraction ranges. The relative viscosity shows a great sensitivity to the particle volume fraction and weak or no sensitivity to temperature: $\mathrm{TiO}_{2}$ TiO 2 –ethylene glycol and $\mathrm{Al}_{2}\mathrm{O}_{3}$ Al 2 O 3 –ethylene glycol nanofluids show a dynamic viscosity increase with respect to ethylene glycol from (4 to 5) % to 30 % and from 14 % to 50 %, respectively. Present experimental measurements were compared both with available measurements carried out by different researchers and computational models for thermophysical properties of nanofluids.     

Role of flying buttresses in the jamming of granular matter through multiple rectangular outlets

We present a simulation study on the formation of particle arches supported by flying buttresses that arrest the flow of monodisperse spherical particles through two adjacent slots (rectangular outlets) in a three-dimensional (3D) anisometric flat-bottomed silo discharging under gravity. Most previous experimental and simulation studies on the jamming of a silo have focused on a single outlet, and have shown that the mean number of particles exiting the silo before it jams depends on the ratio of outlet size to particle diameter ( $R$ ). In this paper, we look at the nature of jamming if there are two adjacent outlets and discover some new physical insights on how sand arches are mechanically supported and how they interact with each other. For a fixed slot width $D_{o}$ and particle diameter $d$ , the distance separating the two openings $D_{w}$ is varied. The distribution of $N$ particles exiting the silo before both slots are jammed is obtained for each $D_{w}$ . From these distributions, we show that as $D_{w}$ becomes less than approximately $3d$ , the particle arches on adjacent outlets start affecting each other, and mutually stable arches become harder to form. We show that in cases, where for a small orifice ratio $R={D_o}/d$ a single outlet would have easily jammed, two adjacent outlets do not jam. We propose that this is due to the importance of stable particles resting on the base of the silo adjacent to the arches, which redistribute the load much like a flying buttress does in Gothic arches.