Yttrium oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 200±425 C using Y(thd) 3 , Y(thd) 3 (bipyridyl), or Y(thd) 3 (1,10-phenanthroline) (thd = 2,2,6,6-tetramethyl-3,5-heptanedione) as an yttrium precursor, and ozone as an oxygen source. All yttrium precursors were analyzed by thermogravimetry/differential thermal analysis (TG-DTA) and mass spectrometry (MS). Soda lime glass and Si(100) were used as substrates. With all precursors, a constant deposition rate of 0.22±0.23 (cycle) ±1 was observed at 250±350 C on both substrates, indicating a surface-controlled growth and similar surface species at the deposition temperatures used. The effect of growth parameters, such as reactant pulsing times, was investigated in detail at 350 C using Y(thd) 3 . Deposited films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) in order to determine crystallinity and surface morphology, while ion-beam analysis and X-ray photoelectron spectroscopy (XPS) were used to analyze stoichiometry and impurity levels. Infrared (IR) measurements were performed to determine the type of carbon impurity. Crystalline films with a (400) dominant orientation were obtained when depositions were carried out within the ALE window (temperature range of 250±375 C), but films deposited below 250 C were nearly amorphous. Preferential orientation changed from (400) to (222) when deposition temperatures were raised slightly above the ALE window to 375 C, where a partial decomposition of Y(thd) 3 probably takes place. Judging from the impurity levels of the films and growth rates, the adducting of Y(thd) 3 does not bring about any advantages in the ALE growth of Y 2 O 3 .
Multiscale carbon
supraparticles (SPs) are synthesized by soft-templating
lignin nano- and microbeads bound with cellulose nanofibrils (CNFs).
The interparticle connectivity and nanoscale network in the SPs are
studied after oxidative thermostabilization of the lignin/CNF constructs.
The carbon SPs are formed by controlled sintering during carbonization
and develop high mechanical strength (58 N·mm–3) and surface area (1152 m2·g–1). Given their features, the carbon SPs offer hierarchical access
to adsorption sites that are well suited for CO2 capture
(77 mg CO2·g–1), while presenting
a relatively low pressure drop (∼33 kPa·m–1 calculated for a packed fixed-bed column). The introduced lignin-derived
SPs address the limitations associated with mass transport (diffusion
of adsorbates within channels) and kinetics of systems that are otherwise
based on nanoparticles. Moreover, the carbon SPs do not require doping
with heteroatoms (as tested for N) for effective CO2 uptake
(at 1 bar CO2 and 40 °C) and are suitable for regeneration,
following multiple adsorption/desorption cycles. Overall, we demonstrate
porous SP carbon systems of low cost (precursor, fabrication, and
processing) and superior activity (gas sorption and capture).
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