Interstitial Doping of SnO_(2) Film with Li for Indium-Free Transparent Conductor

SnO_(2)films exhibit significant potential as cost-effective and high electron mobility substitutes for In_(2)O_(3)films.In this study,Li is incorporated into the interstitial site of the SnO_(2)lattice resulting in an exceptionally low resistivity of 2.028×10^(-3)Ω·cm along with a high carrier concentration of 1.398×10^(20)cm^(-3)and carrier mobility of 22.02 cm^(2)/V·s.

Ethene and butene oligomerization over isostructural H-SAPO-5 and H-SSZ-24: Kinetics and mechanism

BrФnsted-acidic zeolite and zeotype materials are potential catalysts for the conversion of ethene to higher alkenes. In this study, two materials with AFI structure but different acid strength, H-SAPO-5 and H-SSZ-24, were subject to studies of ethene, cis-2-butene and ethene-butene mixture conversion under conditions where C3-C5 alkene formation is thermodynamically favoured over higher hydrocarbons(673-823 K, 1 atm). Ethene and cis-2-butene partial pressures were varied in the range 9-60 and 0.9-8.1 kPa, respectively, and contact times were varied in the range 3.78-756 and 0.573-76.4 s.μmol H+/cm^3 over H-SAPO-5 and H-SSZ-24, respectively. Less than 1% conversion of ethene and less than 10% conversion of butene was obtained in the range of conditions used for elucidation of rate parameters. The ethene conversion rates were more than an order of magnitude higher over the more acidic H-SSZ-24 than over H-SAPO-5(6.5 vs. 0.3 mmol/mol H+.s at 748 K, Pethene = 33 kP a), with corresponding lower reaction order in ethene(1.5 vs. 2.0 at 673 K) and lower apparent activation energy(52 vs. 80 kJ/mol at 698-823 K). Propene selectivity was substantially higher over H-SSZ-24 than over H-SAPO-5(68% vs. 36% at 0.5% ethene conversion). A similar difference in apparent reaction rates was observed for cis-2-butene conversion over the two catalysts, and for co-feeds of ethene and cis-2-butene. However, the cis-2-butene conversion to C3-C5 alkenes was found to be severely influenced by thermodynamic limitations, impeding a detailed kinetic analysis, and leading predominantly to isobutene formation at the highest temperatures.

GaZn-VZn acceptor complex defect in Ga-doped ZnO

Gallium （Ga）-doped ZnO is regarded as a promising plasmonic material with a wide range of applications in plasmonics. In this study, zinc self-diffusion experiments are adopted to disclose the nature of the dominant compensating defect in Ga-doped ZnO isotopic heterostructures. The （GaZn-VZ.）- complex defect, instead of the isolated VZn^2-, is identified as the predominant compensating acceptor center responsible for the low donor doping efficiency. The comparative diffusion experiments operated by the secondary ion mass spectrometry reveal a -0.78 eV binding energy of this complex defect, which well matches the electrical activation energy derived from the temperature-dependent Hall effect measurements （-（0.82±0.02） eV）. These findings contribute to an essential understanding of the （GaZn-VZn）- complex defect and the potential engineering routes of heavily Ga-doped ZnO.

Noble gas as a functional dopant in ZnO

Owing to fully occupied orbitals,noble gases are considered to be chemically inert and to have limited effect on materials properties under standard conditions.However,using first-principles calculations,we demonstrate herein that the insertion of noble gas(i.e.He,Ne,or Ar)in ZnO results in local destabilization of electron density of the material driven by minimization of an unfavorable overlap of atomic orbitals of the noble gas and its surrounding atoms.Specifically,the noble gas defect(interstitial or substitutional)in ZnO pushes the electron density of its surrounding atoms away from the defect.Simultaneously,the host material confines the electron density of the noble gas.As a consequence,the interaction of He,Ne,or Ar with O vacancies of ZnO in different charge states q(ZnO:VO^(q))affects the vacancy stability and their electronic structures.Remarkably,we find that the noble gas is a functional dopant that can delocalize the deep in-gap VO^(q) states and lift electrons associated with the vacancy to the conduction band.

In vitro corrosion behaviour of phenolic coated nickel–titanium surfaces

The biocompatibility of implantable nickel-titanium biomaterials relies on the quality of their surfaces.In this study,nickel-titanium surfaces are coated with phenolic thin films of tannic acid and pyrogallol with the purpose of studying their corrosion resistance in physiological environments.Three tests are performed:the open-circuit potential test,potentiodynamic polarisation and potentiostatic electrochemical impedance spectroscopy.Polarisation measurements are scrutinised in order to gain knowledge concerning the kinetics of the cathodic and anodic reactions,while the open-circuit potentials and impedance spectroscopy help to study the electrolyte-surficial interactions.It is found that coating nitinol with polyphenols results in the depletion of the native oxide layer and thus a decrease of corrosion resistance.Pyrogallic treated nitinol surfaces(with a corrosion rate of 0.119 mm/year)are half as electrochemically corrosion resistive as tannic acid-coated substrate.Therefore,it is proposed that tannic treated nitinol would be a better option if implanted on biomaterial surfaces.