Narrow Results

The ITO film was deposited onto the glass substrate at room temperature by the inclination opposite target type DC magnetron sputtering equipment. An indium tin alloy (In₂O₃(90wt%)+SnO₂(10wt%)) target was used. The Total sputtering pressure was varied from 2.6×10^-1 to 8.3×10^-1Pa. The experimental result showed that the ITO film produced at room temperature had microstructure in which a X-ray diffraction peak is not clear, regardless of the total sputtering pressure. All the films showed a high optical transmittance. The ITO films prepared at low pressures gave low electrical resistivity. The elastic modulus and hardness of ITO films on various total sputtering pressures were increased with decreasing the total sputtering pressure and this tendency was similar to the change in electrical resistivity with decreasing the total sputtering pressure.

In this paper, some available analytical models for the complete stress-strain curve for high-strength concrete (HSC) under uniaxial compression are examined and compared with experimental curves published in the literature. Based on these findings, a new analytical constitutive relation is proposed to generate the complete stress-strain curves for normal weight concrete subjected to uniaxial compression with a strength range of 60-120MPa. To demonstrate the validity of the model, comparisons are made with published experimental data for uniaxial compressive tests on high-strength concrete specimens. The present model is shown to give a quite good representation of mean behavior of the actual stress-strain response.

An optical method has been applied to measure the elastic modulus of a beetle wing membrane. A specimen was prepared by cutting the beetle wing carefully to take a sample size of 5.0 mm in width and 7.5 mm in length. We used a scanning electron microscope for the exact measurement of the membrane thickness of a beetle wing. It was attached to a fixture in order to induce a uniform displacement using a micromanipulator. We measured the applied load by the use of a load cell with a maximum capacity of 5 N and the corresponding displacement was measured by means of an ARAMIS system based on the digital image correlation method. The measured thickness of the beetle wing varied from point to point of the wing part and the elastic modulus was different according to the loading direction. In conclusion, we successfully measured the elastic modulus of a beetle wing with an ARAMIS system based on an optics based measurement method.

We performed the tensile test of an individual carbon nanofiber (CNF) inside a scanning electron microscope. The mechanical testing system was installed in a scanning electron microscope (SEM). The nano-manipulator was set up in the SEM, and the force sensor, which is formed as a cantilever, was mounted on the nano-manipulator. Then, the force sensor can be controlled by using the nano-manipulator. The CNFs were dispersed on the transmission electron microscope (TEM) grid, and the both end of the CNFs were welded on the TEM grid and the tip of force sensor by exposing electron-beam of the SEM. The tensile test of the CNFs was performed by controlling the nano-manipulator. The load response during the tensile test was obtained by force sensor. Stess-strain curve was obtained from force-displacement curve of CNF after tensile test. The elastic modulus of CNFs was calculated at ~12.5 GPa.

Vacancy plays a crucial role in mechanical properties of transition metal borides (TMBs). However, the influence of vacancy on hardness of TMBs is unknown. In this paper, the relationship between boron vacancy and mechanical properties of CrB₄ is investigated by first-principle calculations. Two different vacancies including boron monovacancy (MV) and boron bivacancy (BV) are considered. We find that CrB₄ with boron MV is more stable than that of boron BV. The removed atom weakens the deformation resistances, and reduces the elastic stiffness and hardness. The calculated shear modulus, Young’s modulus and theoretical hardness of boron MV are larger than that of boron BV. The reason is that the removed atom weakens the localized hybridization between B and B atoms, and damages the 3D-network B–B covalent bond. However, the bulk modulus of B${}_{\mathrm{\text{-BV4}}}$ is slightly larger than that of perfect CrB₄. This reason is attributed to the formation of triangular pyramid bonding in B${}_{\mathrm{\text{-BV4}}}$ vacancy.

The structural stability, mechanical properties and Debye temperatures of La-rich La–Ni (LaNi, La₂Ni₃ and LaNi₂) phases were studied by a first-principles method. The formation enthalpy indicates that the La-rich phase is stable. As the La content increases, the enthalpy of formation decreases. The bonding of La–Ni is covalent and metallic. The La-d and Ni-d orbitals contribute mainly at the Fermi level. The mechanical properties indicate that the La-rich La–Ni phases are brittle. La₂Ni₃ has the most prominent anisotropy. The hardness of LaNi, La₂Ni₃ and LaNi₂ are 37.62 GPa, 41.61 GPa and 65.06 GPa, respectively. Those phases have the potential to form a superhard material. LaNi₂ has the highest Debye temperature (232.88 K). LaNi₂ is the most stable among these phases.

MAX phases captured attention ever since they were synthesized. They are suited for different applications, especially in high-temperature and extreme environments. So knowledge of mechanical properties is essential for our applications of MAX phases in different situations. Cr₂AC (A = Al, Ge) compounds belong to M₂AX phases. But, few of their physical properties have been studied. This work demonstrated the compression behavior of Cr₂AC (A = Al, Ge) by first-principles method. The elastic constants were calculated in the range of 0–50 GPa, it is shown that they satisfy the requirement of mechanical stability. The values of bulk moduli, shear moduli, Young’s moduli, Possion’s ratio and Lame’s constant were calculated. We also studied brittleness/ductility of Cr₂AC(A = Al, Ge). For the more, we studied the dependence of a/a₀, c/c₀ and bulk moduli on the pressure below 50 GPa. In the end, we calculated the Mulliken bond overlap and theoretical hardness. We also discussed the bonding and antibonding.

Bulk metallic glasses are often used well below their glass transition temperatures, T_g, because of their change in the physical properties of the material through its glass transition, which is not considered a phase transition; rather it is a phenomenon extending over a range of temperature and is defined by a viscosity threshold of 10¹² Pa ⋅ s. In this work, a Zr-based metallic glass upon annealing below glass transition temperature (T_g–30 K) was quasi-in-situ investigated. The structural and elastic properties were observed carefully by utilizing an in-house designed density testing device and an ultrasonic testing device. We found out that the density, the shear velocity, the longitudinal wave velocity, and the elastic modulus increased through annealing at 719 K for 300, 900 and 1500 s. A possible explanation was presented based on the free volume theory and it was found that the relaxation kinetics in this study obeyed the Kohlraush–Williams–Watts (KWW) relaxation function with $\beta$ = 0.420 $<$ 1 implying that the relaxation mechanisms were multiple ones.

Nanostructured WC-17Co, 2C-12Co coatings and conventional WC-17Co coating were prepared by High Velocity Oxygen Flame (HVOF) spray technique. The elastic modulus, fracture toughness and crack spread path were studied. The residual stress, different phases, microstructure from surface to the depth of coatings were also analyzed. While the nanostructured WC-12Co coating showed the highest elastic modulus, the nanostructured WC-17Co coating has the highest fracture toughness. The compressive residual stress of the nanostructured coatings was higher than the conventional coating. Both WC and W₂C phases showed compressive residual stress, but Co₆W₆C phase showed tensile stress. The distribution of residual stress showed that the stress is the lowest at the surface and the highest close to the interface.

High modulus SiC fibers can be used in complex working environment with alternating heat and cold. In this paper, SiC fibers with various oxygen contents and crystal size were fabricated by polymer-derived ceramics routes. The effects of oxygen content and crystal size on the elastic modulus of SiC fibers were studied in detail. It was found that the elastic modulus of SiC fibers can be improved by reducing the oxygen content and increasing the crystal size of SiC fibers when the crystal size was less than 2 nm. When the oxygen content decreased from 21.5 wt.% to 11.7 wt.%, the elastic modulus of SiC fibers was increased from 131 GPa to 167 GPa. Particularly, the highest elastic modulus of CVC treated hypoxic SiC fibers is close to 200 GPa when the crystallite size is about 2 nm.

Chromium-carbon films have been deposited on silicon substrates by magnetron sputtering of chromium and carbon targets in pure argon atmosphere. The composition of the films was examined by Auger electron spectroscopy. Oxygen, nitrogen, and iron were the major impurities incorporated in the films. The mechanical and electrical properties of the films were investigated as a function of negative bias voltage applied to substrates. The hardness and elastic modulus were measured by a nano-indenter and the values are around 17.0±0.9 GPa and 245±11 GPa, respectively. The hardness and elastic modulus of the films increased while the electrical resistivity decreased when the substrate bias voltage was applied. The lowest resistivity (~ 267 μohm-cm) was obtained at the substrate bias voltage of 50 V. The temperature dependence of resistivity of the films was measured in air from room temperature to 673 K. The time dependence of resistivity of the films was also measured in air at 673 K. It was found that the resistivity changed little with temperature or time.

The thermodynamic and mechanical properties of the zinc-blende indium pnictides InP, InAs and InSb compounds have been investigated thanks to the statistical moment method in statistical mechanics. We have derived the analytical expressions of thermal induced atomic displacement, lattice constant, elastic moduli (Young’s modulus, bulk modulus and shear modulus) and elastic constants of the zinc-blende compounds. The difference of temperature effects on mechanical properties of InSb comparing to InP and InAs compounds has been pointed out. We show that InSb is less affected by temperature while InP changes its mechanical properties from hardness to softness quickly when the temperature increases. The advancement of this method is that it has included the anharmonic effects of thermal lattice vibrations by taking into account the higher-order atomic displacement terms.

Acoustic black hole (ABH), as a new wave manipulation technique, shows excellent applications in vibration and noise reduction of structures. Nowadays, most ABHs use materials with a fixed elastic modulus, limiting their low-frequency performance. Herein ABH plates with variable elastic modulus (VM-ABH) is designed, and its vibration and acoustic radiation characteristics are investigated by using numerical analysis. The results show that the vibration response of VM-ABH has a decrease of 5–13.2dB relative to that of the uniform texture ABH (UT-ABH) in the frequency range of 10–5000Hz, and the degree of energy aggregation is significantly improved. Moreover, the sound pressure level was reduced by 3.6 dB. Meanwhile, by linearly varying the elastic modulus in the center region of the VM-ABH, the effects of gradient index and terminal elastic modulus on the damping characteristics and dynamic response are revealed. The research results provide new objects for the study of vibration and noise reduction of ABH.

In this paper, through finite difference and finite element coupling algorithms with structured grid, the fluid–structure coupling problems of the pressure of the fluid as well as stress and strain of the heterogeneous porous medium under the initial pressure of MPa magnitude are calculated, respectively. The porous medium is a cavity cylinder with fractal characteristics. The parameters of porosity, elastic modulus and Poisson’s ratio of porous media with different fractal dimensions ($D=2.3$, 2.4 and 2.5) are obtained by theoretical calculation. Through theoretical derivation, the amplitude of WM function is expressed by the fractal parameter porosity, which can predict the uneven characteristics caused by the nonuniformity of pore size distribution after explosion. The results show that with the increase of fractal dimensions, the porosity increases, and both the elastic modulus and the Poisson’s ratio decrease. The Poisson’s ratio has a linear relationship with porosity, which is well consistent with the modified formula in the literature. Under the same initial pressure, the stress and strain values of the material without fractal characteristics are much larger than those of the material with fractal feature which has an obvious fluctuation by extracting the average values. It indicates that the fractal porous media with rough surface can effectively reduce the pressure wave peak at the wall surface, and reduce the size of the stress and strain concentrations to prevent the vibration of the cylinder. As expected, if the initial pressure increases with an equal fractal dimension, the stress and strain values of the fluid–structure coupling will increase too. When the initial pressure is equal, the peak value of pressure in wall decreases gradually with the increase of fractal dimension, and the stress and strain values also decrease.

The effective elastic modulus and fracture toughness of the nanofilm were derived with the surface relaxation and the surface energy taken into consideration by means of the interatomic potential of an ideal crystal. The size effects of the effective elastic modulus and fracture toughness were discussed when the thickness of the nanofilm was reduced. And the dependence of the size effects on the surface relaxation and surface energy was also analyzed.

In the present work, hardness and elastic modulus of a titanium nitride coatings prepared on Ti6Al4V by powder immersion reaction-assisted coating (PIRAC) are tested and comparatively studied with a physical vapor deposition (PVD) TiN coating. Surface hardness of the PIRAC coatings is about 11GPa, much lower than that of PVD coating of 22GPa. The hardness distribution profile from surface to substrate of the PVD coatings is steeply decreased from $\sim$22GPa to $\sim$4.5GPa of the Ti6Al4V substrate. The PIRAC coatings show a gradually decreasing hardness distribution profile. Elastic modulus of the PVD coating is about 426GPa. The PIRAC coatings show adjustable elastic modulus. Elastic modulus of the PIRAC coatings prepared at 750${}^{\circ }$C for 24h and that at 800${}^{\circ }$C for 8h is about 234 and 293GPa, respectively.

The Q235 steel was covered by Fe–Al–Nb alloyed coating to improve the mechanical properties of the Q235 steel. This double glow plasma surface metallurgy (DGPSM) surface modification technique was carried out at 1023K and pressure of 38Pa for 4.5h. The surface morphology represented the typical Volmer–Weber mode, an island structure which was accumulated by numerous small particles, and most of the angles formed between three islands were about 120${}^{\circ }$ where there was no appreciable defect. Meanwhile, in the cross-sectional morphology of the Fe–Al–Nb coating, there was a deposition layer, a diffusion layer and two transition regions between the different adjacent interfaces, and the coating approximate 17$\mu$m was found to be metallurgically adhered to the Q235 steel. The basic mechanical properties of the Fe–Al–Nb coating and Q235 steel including the hardness, elastic modulus and friction performance were measured and compared. The results showed that the formation of Fe₃Al, FeAl, and Fe₂Nb intermetallic compounds and Nb carbides in the coating can enhance the mechanical properties of the treated sample. The nanoindentation tests indicated that the hardness and elastic modulus of Fe–Al–Nb coating were 8.08GPa and 260.03GPa which were much higher than Q235 steel. The sliding friction tests showed that Fe–Al–Nb coating significantly improved the friction performance of Q235 steel at the speed of 300, 600 and 900rpm with load 320g for 15min.

In order to improve the mechanical compatibility and cytocompatibility of titanium implants, tantalum coatings were prepared using plasma spraying technology. Tantalum coatings have been deposited via atmospheric plasama spraying (APS) and vacuum plasma spraying (VPS) methods, and then their morphologies, porosities, bonding strengths and elastic modulous were investigated. In vitro cytocompatibility of the two coatings was evaluated via human bone marrow stromal cells (hBMSCs). The results show that oxidation phenomenon was observed for the APS tantalum coatings, while less oxidation was found in the VPS tantalum coatings. Compared with APS tantalum coatings, the VPS tantalum coatings have a more compact microstructure and less impurity content, resulting in a better bonding with the titanium substrate. VPS tantalum coatings were measured to have a lower elastic modulus and a higher hardness than APS Tantalum coatings. Electrochemical corrosion of the coatings were examined and the VPS tantalum coating showed improved chemical stability. Besides, bone marrow stem cells (BMSCs) adhere to and spread well on the surface of both VPS and APS tantalum coatings without significant difference. The proliferation rate of BMSCs is higher on VPS tantalum coating surface than on APS tantalum coatings. Our results suggest that VPS tantalum coatings are more suitable for the application of surface modification of titanium implant due to their lower elastic modulus and better chemical stability for higher mechanical compatibility and cytocompatibility.

This paper represents the nanomechanical properties of various loading levels of montmorillonite clay filled polyester composites and randomly distributed jute fiber reinforced hybrid composites through Vickers micro-hardness test. The study of indentation fracture mechanics in polymer materials is a simple and cost-effective technique for the determination of fracture toughness. Ultrasonication technique was used to disperse the clay in the polyester matrix. The hand layup method was adapted to prepare the test specimens. Incorporation of 5wt.% montmorillonite clay into the polymer matrix results in an enhancement in hardness of 26.52% and the modulus of elasticity increased from 4205.21MPa for neat polyester to 5051.46MPa with the addition of clay. Fracture toughness was observed to depend on the montmorillonite clay content, and the maximum value was observed at 5wt.% nanoclay and 25wt.% jute fibers. The results show that the increase in the fiber content reduces the crack propagation in hybrid composites and increases the fracture toughness. To predict the crack size, the scanning electron microscope images are used.

Background: Cortical bone analysis has been investigated at the macroscopic level with mechanical tests and imaging techniques, but few studies have been done at the microscopic level (osteons). The purpose of this study is to measure the elastic modulus of thick lamellae of osteons exhibiting different degrees of mineralization. This study aims to provide clinicians with a better understanding of bone remodeling and help in assessing the different stages of bone healing. Methods: Six femoral human samples (5 mm × 5 mm × 5 mm) were cut transversally along the length of a human femur. Scanning electron micrographs were produced to reflect the composition of the microstructure. Three types of osteons were selected: white (high mineralization), gray (intermediate mineralization), and dark (low mineralization) osteons. Nanoindentation tests were performed on three locations of the thick lamella located in the middle of each osteon. The mechanical test induced three holdings and unloadings with a constant holding of 10 s. The maximal force was 2500 μN, which induced a maximal depth of about 400 nm. Results: Elastic modulus (E) and hardness (H) for the white (N = 61), gray (N = 17), and dark (N = 39) osteons were E_white = 21.30 GPa ± 3.00 GPa and H_white = 0.55 GPa ± 0.15 GPa, E_gray = 19.27 GPa ± 1.78 GPa and H_gray = 0.41 GPa ± 0.09 GPa, and E_dark = 12.95 GPa × 2.66 GPa and H_dark = 0.30 GPa ± 0.10 GPa, respectively. The variation of elastic properties within a lamella was approximately 2.6 GPa, depending on the level of mineralization. Conclusions: These results demonstrate the inhomogeneity of the lamella, suggesting that both the orientation of collagen fibers and the degree of mineralization may vary within the lamella. Our study shows a large range of elastic properties and hardness, reflecting different degrees of osteon mineralization.