Phonon transition across an isotopic interface

Abstract

Isotopic mixtures result in distinct properties of materials such as thermal conductivity and nuclear process. However, the knowledge of isotopic interface remains largely unexplored mainly due to the challenges in atomic-scale isotopic identification. Here, using electron energy-loss spectroscopy in a scanning transmission electron microscope, we reveal momentum-transfer-dependent phonon behavior at the h−10BN/h-11BN isotope heterostructure with sub-unit-cell resolution. We find the phonons’ energy changes gradually across the interface, featuring a wide transition regime. Phonons near the Brillouin zone center have a transition regime of ~3.34 nm, whereas phonons at the Brillouin zone boundary have a transition regime of ~1.66 nm. We propose that the isotope-induced charge effect at the interface accounts for the distinct delocalization behavior. Moreover, the variation of phonon energy between atom layers near the interface depends on both of momentum transfer and mass change. This study provides new insights into the isotopic effects in natural materials.

Injectable gelatin microspheres for osteomyelitis treatment: osteogenic and anti-inflammatory effect

“…The swelling property is essential for microspheres in tissue engineering, and most microspheres, especially those with a large amount of amino groups (such as Gel), will swell in an aqueous solution, resulting in Gel expansion. 65 Here, microspheres swelled rapidly in aqueous solution within 15 min (Fig. 6B).…”

Nanoscale Localized Phonons at Al2O3 Grain Boundaries

“…55,56 The tail of the zero-loss peak is fitted with a Pearson function with two fitting windows and then subtracted in order to obtain the vibrational signal. 41,57 The fitting windows are selected to make the background-subtracted spectra at the bulk The DFPT simulations were conducted using the Quantum Espresso 59,60 with the PBE Exchange-Correlation functional and Ultrasoft pseudopotential 61 for O and norm-conserving pseudopotential 62 for Al. The cutoff of the wave functions is 25 Ry (Ry) and 225 Ry of the charge density and potential.…”

“…The spectra were first aligned by zero-loss peaks to correct possible beam energy drift. A block-matching and 3D filtering (BM3D) algorithm was applied to remove Gaussian noise. , The tail of the zero-loss peak is fitted with a Pearson function with two fitting windows and then subtracted in order to obtain the vibrational signal. , The fitting windows are selected to make the background-subtracted spectra at the bulk area best fit the simulated EELS spectrum of bulk Al 2 O 3 . The statistical factors of the background-subtracted spectra, which were resulted from the different scattering probability of phonons with different frequency, were further corrected to make the spectra more comparable to the real phonon DOS …”

Adhesion Energy-Assisted Low Contact Thermal Resistance Epoxy Resin-Based Composite

“…In recent years, research on contact thermal resistance between inorganic solids and polymers has received more and more attention. , Different models and test methods of contact thermal resistance from a macroscopic and microscopic perspective have been proposed. − Both experimental and simulation results have demonstrated that bridging phonon spectral mismatch and enhancing adhesion strength between two contacting materials can reduce contact thermal resistance, such as in surface chemical treatment − and intermediate layer insertion. , As an effective strategy, introducing self-assembled monolayers can reduce contact thermal resistance. , However, these complex, cumbersome, and inconvenient requirements greatly limit their wide applicability in practical situations. The need for a practical method for the design and fabrication of epoxy resin composites with low contact thermal resistance with their contacting surface has remained a central challenge for the field.…”