In the present work, a combination of experimental and numerical procedure is proposed to study the effects of different hygrothermal conditions on the creep strain, viscoelastic properties of ...nanocomposites, and mechanical properties of such nanocomposite-based carbon fiber–reinforced polymer (CFRP) hybrid composite materials. Ultrasonic probe sonicator is used to randomly disperse the multiwalled carbon nanotubes into an epoxy to minimize agglomerations. Dynamic mechanical analysis is employed to conduct the creep tests under different hygrothermal conditions of such nanocomposite samples. The Findley power law is used to obtain the long-term creep behavior of nanocomposite materials. Prony series is used to determine the viscoelastic properties of nanocomposite material in the frequency domain. Coefficient of moisture expansion (CME) is independent of moisture concentration; thus, CME of the nanocomposite is also determined. Strength of materials and Saravanos–Chamis micromechanics (SCM) have also been utilized to obtain the mechanical properties of such hybrid composite materials under different hygrothermal conditions. It has been found that the inclusion of multiwalled carbon nanotubes in the nanocomposite and hybrid composites improves storage modulus and loss factor (i.e., tanδ) compared to the conventional CFRP-based composite materials under hygrothermal conditions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Fe4NbTaO9 material was synthesized by solid state reaction and arc melting method.•Due to the high cooling rates during the arc melting process, precipitation of additional phases is ...suppressed.•Most prominent magnetoelectric response was observed in Fe4NbTaO9 without spin-flop phase.
In this paper, we have investigated magnetic, dielectric, and pyroelectric properties of polycrystalline Fe4NbTaO9 which is closely related to the recently discovered Fe4Nb2O9 and Fe4Ta2O9 that show magnetoelectric/multiferroic effect. Fe4NbTaO9 samples were synthesized using two synthesis routes i.e. solid-state reaction and arc melting methods. Rietveld analysis of XRD patterns confirmed the proper phase formation with P3-c1 space-group symmetry of these two samples. No impure phase was observed in the arc melted sample. Magnetic measurements have indicated an antiferromagnetic phase transition at TN ≈ 88 K for both synthesized samples. Temperature dependent dielectric curves reveal two broad transitions at TN1 ≅ 88 K and TN2 ≅ 50 K. Further, magnetic field induced electric polarization is evidenced by pyro-electric curves in both samples of Fe4NbTaO9. Herein, all findings demonstrate that partial replacement of Nb5+ by Ta5+ is sufficient to modify the ground state in the Fe4B2O9 (B = Nb, Ta) members. Our results provide new insights into magnetoelectric phase control of the novel oxide multiferroics.
•Low temperature neutron diffraction data reveal non-collinear magnetic structure in Co4Ta2O9.•Neutron diffraction data fit best to a non-centro-symmetric crystal structure below Neel ...temperature.•Correlation between magnetic structure and improper ferroelectricity is analyzed for Co4Ta2O9.•Co-existing large magnetoelectric coupling is determined in the spin-flop phase of Co4Ta2O9.
We study magnetocapacitance (MC) effect and magnetoelectric (ME) coupling in spin-flop driven antiferromagnet Co4Ta2O9. Powder neutron diffraction data reveal that the magnetic structure corresponds to a non-collinear arrangement along with a non-centrosymmetric crystal structure below Néel Temperature. Electric polarization is achieved below Néel temperature only when the sample is cooled in the presence of external magnetic field. The magnetocapacitance data at high magnetic fields are analyzed by phenomenological Ginzburg-landau theory of ferro-electromagnets and it is found that change in dielectric constant is proportional to the square of magnetization. The saturation polarization and magnetoelectric coupling are estimated to be 52 µC/m2 and γ = 1.4 × 10−3 (emu/g)−2 respectively at 6 Tesla. Strong magnetoelectric coupling and ferroelectric phase in the anti-ferromagnetic Co4Ta2O9 are correlated to magnetic structure as derived from neutron diffraction data.
Topological materials with extremely large magnetoresistance exhibit a prognostic feature of resistivity turn-on behaviour. This occurs when the temperature dependence of resistivity ρ(T) changes ...from metallic to semiconducting characteristics on application of external magnetic field above a threshold value. Here, we study the magneto-transport properties of type-II Weyl Semimetal WP2. The zero field electrical resistivity in the low temperature region indicates the dominant electron-phonon scattering. The saturation in ρ(T) curves under all applied magnetic fields are observed at low temperatures. A minimum in resistivity at ~40K is revealed in the temperature derivative of resistivity curves, which implies onset of field induced turn-on effect. Furthermore, a non-saturating linear magnetoresistance (MR) is observed above ~ 5 T which is generally assigned to linear energy dispersion near the Weyl nodes. However, Kohler's scaling fits the data well with resistivity ρ~(B/ρ0)m that implicitly explains the turn-on behaviour and the resistivity minimum. Thus, semi-classical theories of magnetoresistance are consistent with our data without the need to invoke topological surface states. Our findings in this work provides an alternative basis to understand the temperature dependence of magnetoresistance in topological materials.
•Observation of resistivity saturation and magnetic field induced resistivity turnon effect in WP2 .•Determination of resistivity crossover temperature from the temperature derivative of resistivity and energy band gap from the Arrhenius plot.•Detection of linear transverse magnetoresistance (MR) at all temperatures from magnetic field dependent transverse MR data.•Observation of parabolic and linear magnetic field dependence of transverse MR at low temperatures.•Estimation of resistivity minimum and turn-on effect from the classical description of Kohler scaling rule.
A New Model for Grinding Force Prediction and Analysis Patnaik Durgumahanti, U.S.; Singh, Vijayender; Venkateswara Rao, P.
International journal of machine tools & manufacture,
03/2010, Letnik:
50, Številka:
3
Journal Article
Recenzirano
In the present paper a new grinding force model is developed by incorporating the effects of variable coefficient of friction and ploughing force. This is based on the fact that chip formation during ...grinding consists of three stages: ploughing, cutting and rubbing. Equations for the total normal and tangential force components per unit width of the grinding, during these three stages, were established. These components were expressed in terms of the experimental coefficients and process parameters like wheel speed, table feed and depth of cut. All the coefficients were determined experimentally by performing grinding tests at specified conditions. The variation of the friction coefficient with process parameters such as wheel speed and work feed has been taken into consideration while calculating the frictional force components. The ploughing force components were modelled by performing single-grit tests. During these tests the grinding forces were measured by duplicating the cutting mechanism of grinding wheel using a dummy aluminium wheel and a diamond indenter. The predicted normal and tangential grinding forces were compared with those experimentally obtained and the results show reasonable agreement quantitatively. From the total force values the contributions of each component of force were obtained.
Abstract
Geometric Spin Frustration, when sufficiently strong, provides a platform for novel spin textures with emergent phenomena, such as ferroelectricity. This article investigates NiCr
2
O
4
, a ...spinel chromite co-hosting the frustration of Cr
3+
spins with orbital frustration of Ni
2+
ions, with the latter expected to eradicate the spin frustration by lowering lattice symmetry. Detailed experiments unveil an intriguing reentrant-spin-glass-like behavior alongside the previously known canted ferrimagnetism. Our analysis focuses on the ordering of Cr
3+
spins at two distinct sublattices, with one contributing to canted ferrimagnetism, while the other exhibits a local
↑↑↓↓
(spin-frustrated) texture, potentially inducing spin-glass behavior. Density functional theory calculations corroborate the experimental findings, establishing
↑↑↓↓
as the ground state of NiCr
2
O
4
. This study presents new prospects for ferroelectricity driven by exchange striction in orbitally ordered spinel chromites.
•The liquid octane accommodation coefficient αc was studied via molecular dynamics simulations.•The average lifetime of molecular pair-association in bulk liquid octane was estimated.•Octane ...condensation probabilities were estimated in the room temperature range.•The model of octane molecule was found to have a stronger effect than temperature on the computed αc.•The assumption that αc=1 was confirmed valid in the room temperature range.
The condensation coefficient, αc, also called mass accommodation coefficient, of liquid octane, is assumed to be 1.0 in fluid models of thin film evaporation even though it decreases with increasing liquid temperature. The temperature range where αc=1 is valid, is yet to be fully described. In this work, the condensation coefficient of liquid octane was estimated by employing large scale equilibrium classical molecular dynamics simulations and computing the condensation probability as the ratio of the number of octane molecules that condense in the liquid phase to the number of octane molecules incident at the interface from the gas phase. The effect of the model details on the computed value of the condensation coefficient was explored by using two different parameterizations of the octane molecule, the all-atom OPLS and the united-atom TraPPE force fields. The condensation probabilities were computed in the temperature range from 290K to 350K. Bulk properties of liquid octane were also studied via molecular dynamics simulations and the persistent residence times of nearest coordination of octane molecules were determined. At 300K, the temperature of interest in electronics cooling applications, the united-atom molecular model predicted αc=0.96 and the all-atom model predicted αc=0.93. No significant temperature dependence of the condensation coefficient was observed within the studied temperature range, therefore, supporting the assumption of αc=1.0 at room temperature. The two octane models predicted similar liquid structure and condensation probabilities. Compared to the all-atom molecular model, the united-atom model was found to predict shorter residence times in the first coordination shell of bulk octane molecules. This work extends the computational prediction of octane condensation coefficient into room temperature range.
We report on the structural, electrical and magnetic measurements in as-grown polycrystalline samples of Pb
10−x
Cu
x
(PO
4
)
6
O. This compound has been recently reported to be a room temperature ...superconductor. Our as-grown specimen has excellent XRD matching with the original submission of Lee et al. This sample has 1.5% of Cu
2
S as an impurity phase. A resistive transition around 380 K, possibly corresponding to structural transitions of Cu
2
S, is observed. No evidence of superconducting to normal state transitions in I–V characteristics at room temperature is obtained. Magnetization measurements show linear diamagnetic behavior that cannot be associated with the superconducting state. Hall measurements provide evidence of hole doping through Cu substitution. In summary, we find no evidence for room temperature ambient pressure superconductivity in Cu doped lead apatite Pb
10−x
Cu
x
(PO
4
)
6
O.
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