Imaging stress and magnetism at high pressures using a nanoscale quantum sensor.

Criticality of local three-dimensional stresses in a symmetric adhesively bonded joint

The nitrogen-vacancy (NV) color center in diamond is a promising solid-state quantum system at room temperature. However, its sensitivity is limited by its low fluorescence collection efficiency, and its coherence time is limited by spin interference of impurity electrons around the NV color center. Here, we innovatively fabricated a one-dimensional photonic crystal on the surface of diamond, which greatly improved the fluorescence intensity of the NV color centers and increased the sensitivity of NV ensembles by a factor of 2.92. In addition, the laser reflected by the photonic crystal excites impurity electrons around the NV color centers, improving the electric field environment around the NV color centers, which exponentially prolongs the dephasing time (from 209 to 841 ns), opening avenues for NV color-center ensemble sensors.

The axial‐torsional interaction of an epoxy resin was investigated by subjecting thin‐walled tubular specimens to combined normal and shear stress components. It is shown that a superimposed normal stress (tensile or compressive) or hydrostatic pressure will influence shear creep behavior. Similarly, a superposed shear stress affects the normal stress response of the resin. The axial‐torsional stress interaction is also observed in transient stress responses under different strain paths, and in the creep deformation with non‐proportional stress histories. Urear viscoelastic constitutive models are unable to predict the aforementioned behaviors. Two typical nonlinear viscoelastic constitutive models are examined with respect to their capabilities to predict the observed response. It Is shown that the predictions of these two models agree only qualitatively but not quantitatively with the experimental results.

Stress concentration and local behaviour of prestressed composite laminates/sandwich plates with overhangs in cylindrical bending

Pressure profoundly alters all states of matter. The symbiotic development of ultrahigh-pressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials’ properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields. These HP studies include: HP x-ray emission spectroscopy, which provides information on the filled electronic states of HP samples; HP x-ray Raman spectroscopy, which probes the HP chemical bonding changes of light elements; HP electronic inelastic x-ray scattering spectroscopy, which accesses high energy electronic phenomena, including electronic band structure, Fermi surface, excitons, plasmons, and their dispersions; HP resonant inelastic x-ray scattering spectroscopy, which probes shallow core excitations, multiplet structures, and spin-resolved electronic structure; HP nuclear resonant x-ray spectroscopy, which provides phonon densities of state and time-resolved Mössbauer information; HP x-ray imaging, which provides information on hierarchical structures, dynamic processes, and internal strains; HP x-ray diffraction, which determines the fundamental structures and densities of single-crystal, polycrystalline, nanocrystalline, and non-crystalline materials; and HP radial x-ray diffraction, which yields deviatoric, elastic and rheological information. Integrating these tools with hydrostatic or uniaxial pressure media, laser and resistive heating, and cryogenic cooling, has enabled investigations of the structural, vibrational, electronic, and magnetic properties of materials over a wide range of pressure-temperature conditions.

ABSTRACTThe evolution of a bubble confined inside a nonlinear micro vessel fully filled with a viscous liquid, subjected to a shock lithotripsy wave (SWL), is analyzed with a previously established asymmetrical model on bubble oscillation. Both the normal and shear stress components within the vessel wall are calculated. It is observed that although the shear stress induced by viscosity is far less than the normal stresses, hypertension patients are still at more risk than normal people in SWL because of the high blood pre-pressure and stiff vessel wall accompanying their high blood viscosity. Hence, safety of hypertensive patients with high blood viscosity must be taken into careful consideration in SWL. More detailed numerical results show that the increase of circumferential normal stress and strain in SWL is significantly larger than that of other stresses and strains. Large circumferential normal stress and strain are responsible for excessive dilation of vessel wall during asymmetrical oscillation of constrained bubbles, which implies that the vessel wall will rupture mainly in the form of a cleft along the vessel axial direction.

Three-dimensional stress analysis of textile composites: Part I. Numerical analysis

The nitrogen-vacancy (NV) color center in chemical vapor deposition (CVD) diamond has been widely investigated in quantum information and quantum biosensors due to its excellent photon emission stability and long spin coherence time. However, the temperature dependence of the energy level of NV color centers in diamond is different from other semiconductors with the same diamond cubic structure for the high Debye temperature and very small thermal expansion coefficient of diamond. In this work, a diamond sensor for temperature measurement with high precision was fabricated based on the investigation of the energy level shifts of NV centers by Raman and photoluminescence (PL) spectra. The results show that the intensity and linewidth of the zero-phonon line of NV centers highly depend on the environmental temperature, and the energy level shifts of NV centers in diamond follow the modified Varshni model very well, a model which is better than the traditional version. Accordingly, the NV color center shows the ability in temperature measurement with a high accuracy of up to 98%. The high dependence of NV centers on environmental temperature shows the possibility of temperature monitoring of NV center-based quantum sensors in biosystems.

The synthesis of the high-pressure ε phase of iron, which has not been observed under a conventional shock compression, was attained using a femtosecond laser. The lower pressure and temperature α phase (bcc) transforms to the γ phase (fcc) at higher temperatures and to the ε phase (hcp) at higher pressures. A shock induced α to ε phase transition in iron is one of the most famous transitions under high pressure. The induced high-pressure ε phase by a conventional shock loading returns to the α phase and it is not quenched after the shock release because this transition is considered to be diffusionless. Crystalline structures in a recovered iron sample after the femtosecond laser (800 nm, 120 fs, 1014 W/cm2) irradiation were determined using the electron diffraction and the synchrotron X-ray diffraction methods. These results show the existence of the ε phase and the fcc structure in the recovered iron. The femtosecond laser-driven shock wave may have the potential to synthesis high-pressure phases of other materials that has not been done using the conventional shock wave.

Pressure sensitivity of cemented granular materials

A robust hyper-elastic beam model under bi-axial normal-shear loadings

The interlaminar stress components can cause delamination (separation of laminae), resulting in the failure of material before its elastic limit. Thus, the accurate prediction of the stress components in the composite laminates is vital for the prediction of onset and progress of delamination. Our aim is to analytically arrive at a close approximation solution for interlaminar stress components using recovery relations through 1-D analyses. In this study, the development of an efficient analytical approach to obtain the 3-D elasticity solutions by using recovery relations is achieved. In order to get these stress components accurately, a procedure combining VAM-based framework with approximation method is developed. The approximate method is based upon the stress distribution from more appropriate, sophisticated, and simple polynomials on the equilibrium equation of elasticity. The resulting solution satisfies all the boundary conditions and the compatibility. A parametric study is carried out to understand the nature of 3-D stress components along the thickness of various symmetric, quasi-isotropic, and antisymmetric stacking sequences by this approach. The effectiveness of our approach is demonstrated by comparing the results for interlaminar normal and shear stress components along the interface and through the thickness near free edge under axial strain with those of the available in literature and 3-D FEM for the symmetric, antisymmetric, angle-ply, and cross-ply laminates. This newly described approach shows a good agreement and the computational efficiency. This approach effectively predicts the 3-D stress components with great time-saving.

The alpha-epsilon phase transition in shock loaded iron is well-known from numerous plate impact tests by the very accurately determined phase transition pressure value of 13 GPa. However, a more recent experimental study, using a sample loaded by a sweeping detonation wave, has found that a drop in the specific volume due to the transition during non-planar loading is not linked directly with the phase transition pressure value. The present analysis employing a two- phase model with the phase transition kinetic considers contribution from the shear stress at the loading resulting in the phase transition and kinetic character of the transition. The analysis demonstrates that taking these factors into account improves the accuracy of the description of the experimental data.

High-resolution two-photon fluorescence microscope imaging of nanodiamonds containing NV color centers

We describe an approach for acquiring high quality x-ray absorption fine structure (XAFS) spectroscopy spectra with wide energy range at high pressure using diamond anvil cell (DAC). Overcoming the serious interference of diamond Bragg peaks is essential for combining XAFS and DAC techniques in high pressure research, yet an effective method to obtain accurate XAFS spectrum free from DAC induced glitches has been lacking. It was found that these glitches, whose energy positions are very sensitive to the relative orientation between DAC and incident x-ray beam, can be effectively eliminated using an iterative algorithm based on repeated measurements over a small angular range of DAC orientation, e.g., within +/-3 degrees relative to the x-ray beam direction. Demonstration XAFS spectra are reported for rutile-type GeO2 recorded by traditional ambient pressure and high pressure DAC methods, showing similar quality at 440 eV above the absorption edge. Accurate XAFS spectra of GeO2 glass were obtained at high pressure up to 53 GPa, providing important insight into the structural polymorphism of GeO2 glass at high pressure. This method is expected be applicable for in situ XAFS measurements using a diamond anvil cell up to ultrahigh pressures.