Search results for "Diffusion"

Effect of pseudo-gravitational acceleration on the dissolution rate of miscible drops

2017

The effect of pseudo-gravitational acceleration on the dissolution process of two phase miscible systems has been investigated at high acceleration values using a spinning drop tensiometer with three systems: 1-butanol/water, isobutyric acid/water, and triethylamine/water. We concluded that the dissolution process involves at least three different transport phenomena: diffusion, barodiffusion, and gravitational (buoyancy-driven) convection. The last two phenomena are significantly affected by the centrifugal acceleration acting at the interface between the two fluids, and the coupling with the geometry of the dissolving drop leads to a change of the mass flux during the course of the dissol…

Coagulation bath composition and desiccation environment as tuning parameters to prepare skinless membranes via diffusion induced phase separation

2015

Diffusion Induced Phase Separation (DIPS) is a currently used technique to produce porous membranes for a large variety of applications. A strong limitation is represented by the occurrence of a dense skin, which is formed during the process, highly reducing the membrane permeability. To overcome this issue, two modifications of the standard DIPS protocol were investigated: the use of coagulation baths composed by a solvent/nonsolvent mixture and the desiccation in a controlled environment, by modulating the partial pressure of nonsolvent vapor. An appropriate choice of coagulation bath composition, together with an appropriate desiccation protocol (i.e., the use of a nonsolvent vapor), wil…

Inside Cover: Exploiting Reaction‐Diffusion Conditions to Trigger Pathway Complexity in the Growth of a MOF (Angew. Chem. Int. Ed. 29/2021)

2021

Giant Spin Seebeck Effect through an Interface Organic Semiconductor

2019

Interfacing an organic semiconductor C60 with a non-magnetic metallic thin film (Cu or Pt) has created a novel heterostructure that is ferromagnetic at ambient temperature, while its interface with a magnetic metal (Fe or Co) can tune the anisotropic magnetic surface property of the material. Here, we demonstrate that sandwiching C60 in between a magnetic insulator (Y3Fe5O12: YIG) and a non-magnetic, strong spin-orbit metal (Pt) promotes highly efficient spin current transport via the thermally driven spin Seebeck effect (SSE). Experiments and first principles calculations consistently show that the presence of C60 reduces significantly the conductivity mismatch between YIG and Pt and the s…

Theoretical Study on the Diffusion Mechanism of Cd in the Cu-Poor Phase of CuInSe2 Solar Cell Material

2013

We have employed first-principles static and molecular dynamics (MD) calculations with semilocal and screened-exchange hybrid density functionals to study the diffusion of Cd in bulk CuIn5Se8, a copper-poor ordered vacancy compound of CuInSe2. The diffusion mechanism and the underlying kinetics/energetics were investigated by combining ab initio metadynamics simulations and nudged elastic band (NEB) calculations. We found that the migration of Cd occurs via a kick-out of Cu atoms, assisted by the pristine vacancies that are constitutive of this compound, and follows a double-hump energy profile. The rate-limiting step has a barrier of about 1 eV at 0 K but reduces to 0.3 eV at 850 K, pointi…

Mg impurity in helium droplets.

2011

Within the diffusion Monte Carlo approach, we have determined the structure of isotopically pure and mixed helium droplets doped with one magnesium atom. For pure 4He clusters, our results confirm those of M. Mella et al. [J. Chem. Phys. 123, 054328 (2005)] that the impurity experiences a transition from a surface to a bulk location as the number of helium atoms in the droplet increases. Contrarily, for pure 3He clusters Mg resides in the bulk of the droplet due to the smaller surface tension of this isotope. Results for mixed droplets are presented. We have also obtained the absorption spectrum of Mg around the 3s3p 1P_1 <-- 3s2 1S_0 transition.

Interface Solid-State Reactions in La0.8Sr0.2MnO3/Ce0.8Sm0.2O2 and La0.8Sr0.2MnO3/BaCe0.9Y0.1O3 Disclosed by X-ray Microspectroscopy

2019

The stability of the electrode/electrolyte interface is a critical issue in solid-oxide cells working at high temperatures, affecting their durability. In this paper, we investigate the solid-state chemical mechanisms that occur at the interface between two electrolytes (Ce0.8Sm0.2O2, SDC, and BaCe0.9Y0.1O3, BCY) and a cathode material (La0.8Sr0.2MnO3, LSM) after prolonged thermal treatments. Following our previous work on the subject, we used X-ray microspectroscopy, a technique that probes the interface with submicrometric resolution combining microanalytical information with the chemical and structural information coming from space-resolved X-ray absorption spectroscopy. In LSM/BCY, the …

Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE

2016

A family of new branched phosphine derivatives {Ph2N-(C6H4)n-}3P → E (E = O 1-3, n = 1-3; E = S 4-6, n = 1-3; E = Se 7-9, n = 1-3; E = AuC6F5 4-6, n = 1-3), which are the donor-acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λem = 403-483 nm in CH2Cl2 solution, λem = 400-469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge -(C6H4)n-. The pyramidal geometry of central R3P → E fragment on the one hand disrupts π-conjugation between the branches to preserve blue luminescence and high triplet energy, while on the other hand provides amorphous materials to prevent excimer form…

Magnetic Properties of Quinoidal Oligothiophenes: More Than Good Candidates for Ambipolar Organic Semiconductors?

2006

A series of quinoidal oligothiophenes have been investigated by means of solid-state Fourier-transform (FT)-Raman and electron spin resonance (ESR) spectroscopies complemented with density functional theory calculations. FT-Raman spectra recorded as a function of temperature show that, upon laser irradiation, the molecules undergo a reversible structural evolution from a quinoid-type pattern at low temperature to an aromatic-type pattern at high temperature. Moreover, ESR spectra show that a portion of these compounds exists in a biradical state at room temperature. These seemingly disconnected findings and others, such as conformational isomerism, are consistently explained by the consider…

Donor and acceptor substituted triphenylamines exhibiting bipolar charge-transporting and NLO properties

2017

Donor-acceptor type triphenylamine-based malonodinitriles were synthesized and their thermal, optical, photophysical, electrochemical and nonlinear optical properties were studied. The synthesized compounds formed glasses with the glass transition temperatures ranging from 38 to 107 °C. The ionization potentials of the samples of the compounds established by cyclic voltammetry were found to be in the range of 5.50–5.57 eV, while those estimated by photoelectron emission spectrometry ranged from 5.36 to 5.74 eV. The electron affinity values of the compounds were found to be in the range of −3.41–−3.05 eV. The ambipolar charge-transporting properties were observed for the layers of triphenyla…