“…Relatively weak O 2 –C binding is thought to govern this behavior even though the localized partial pressure of the co-reactant oxygen gas is estimated to be on the order of 1.5× higher. The O 2 –C residence time is short (20 ns [ 62 ]) relative to the MeCpPt(IV)Me 3 precursor residence time (reported values ranging from 29 µs [ 63 ] to 30 ms [ 64 ]). The result is a negligible O 2 surface coverage which inhibits the purification reaction.…”
We investigate the growth, purity, grain structure/morphology, and electrical resistivity of 3D platinum nanowires synthesized via electron beam induced deposition with and without an in situ pulsed laser assist process which photothermally couples to the growing Pt–C deposits. Notably, we demonstrate: 1) higher platinum concentration and a coalescence of the otherwise Pt–C nanogranular material, 2) a slight enhancement in the deposit resolution and 3) a 100-fold improvement in the conductivity of suspended nanowires grown with the in situ photothermal assist process, while retaining a high degree of shape fidelity.
“…Relatively weak O 2 –C binding is thought to govern this behavior even though the localized partial pressure of the co-reactant oxygen gas is estimated to be on the order of 1.5× higher. The O 2 –C residence time is short (20 ns [ 62 ]) relative to the MeCpPt(IV)Me 3 precursor residence time (reported values ranging from 29 µs [ 63 ] to 30 ms [ 64 ]). The result is a negligible O 2 surface coverage which inhibits the purification reaction.…”
We investigate the growth, purity, grain structure/morphology, and electrical resistivity of 3D platinum nanowires synthesized via electron beam induced deposition with and without an in situ pulsed laser assist process which photothermally couples to the growing Pt–C deposits. Notably, we demonstrate: 1) higher platinum concentration and a coalescence of the otherwise Pt–C nanogranular material, 2) a slight enhancement in the deposit resolution and 3) a 100-fold improvement in the conductivity of suspended nanowires grown with the in situ photothermal assist process, while retaining a high degree of shape fidelity.
“…22 Graphite has a high density and a very low specific surface area. 2,23 The pore volume of the carbonized charcoals ranges between 0.044 and 0.170 mL/g, with the melt carbons typically having lower pore volumes compared to corncob carbon.…”
Section: Resultsmentioning
confidence: 99%
“…The reason for this decrease is not known; however, it is recognized that boron-doping of carbon materials can enhance graphitization , The pore volume of the carbonized charcoals ranges between 0.044 and 0.170 mL/g, with the melt carbons typically having lower pore volumes compared to corncob carbon. 1 (a) Adsorption/desorption isotherm of carbonized (950 °C) 20−40 Mesh corncob charcoal over the pressure region P / P 0 = 0.01−1.…”
Charcoals and carbonized charcoals (i.e., biocarbons) were prepared from a wide variety of biomass substrates,
including pure sugars containing five- and six-membered rings with furanose and pyranose configurations,
lignin, agricultural residues (corncob and nut shells), and a hard wood. These biocarbons were subject to
proximate and elemental analysis, gas sorption analysis, and analysis by inductively coupled plasma mass
spectroscopy (ICP-MS), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron spin resonance
(ESR), 13C cross-polarization magic-angle spinning (CPMAS) NMR, and matrix-assisted, laser desorption
ionization coupled with time-of-flight mass spectroscopy (MALDI-TOF MS). All the carbonized charcoals
contained oxygen heteroatoms, had high surface areas, and were excellent conductors of electricity. Doping
the biocarbon with boron or phosphorus resulted in a slight improvement in its electrical conductivity. The
XRD analysis indicated that the carbonized charcoals possess an aromaticity of about 71% that results from
graphite crystallites with an average size of about 20 Å. The NMR analysis confirmed the highly aromatic
content of the carbonized charcoals. The ESR signals indicated two major types of carbon-centered organic
radicals. MALDI-TOF spectra of the charcoals and carbonized charcoals greatly differed from those of synthetic
graphite. The biocarbons contained readily desorbed discrete ions with m/z values of 317, 429, 453, 465,
685, and 701. These findings were employed to develop a model for the structure of carbonized charcoal that
is consistent with the biocarbon's oxygen content, microporosity and surface area, electrical conductivity,
radical content, and its MALDI-TOF spectra.
“…Here, we demonstrate that the dilute sorbate limit does not correspond to the real sorption behavior at the same limit. (How adsorption at very low a 2 can be measured experimentally − is summarized in the Supporting Information). Extrapolation requires a fitting function.…”
Surface area estimation
using the Brunauer–Emmett–Teller
(BET) analysis has been beset by difficulties. The BET model has been
applied routinely to systems that break its basic assumptions. Even
though unphysical results arising from force-fitting can be eliminated
by the consistency criteria, such a practice, in turn, complicates
the simplicity of the linearized BET plot. We have derived a general
isotherm from the statistical thermodynamic fluctuation theory, leading
to facile isotherm fitting because our isotherm is free of the BET
assumptions. The reinterpretation of the monolayer capacity and the
BET constant has led to a statistical thermodynamic generalization
of the BET analysis. The key is Point M, which is defined as the activity
at which the sorbate–sorbate excess number at the interface
is at its minimum (i.e., the point of strongest sorbate–sorbate
exclusion). The straightforwardness of identifying Point M and the
ease of fitting by the statistical thermodynamic isotherm have been
demonstrated using zeolite 13X and a Portland cement paste. The adsorption
at Point M is an alternative for the BET monolayer capacity, making
the BET model and its consistency criteria unnecessary. The excess
number (i) replaces the BET constant as the measure of knee sharpness
and monolayer coverage, (ii) links macroscopic (isotherms) to microscopic
(simulation), and (iii) serves as a measure of sorbate–sorbate
interaction as a signature of sorption cooperativity in porous materials.
Thus, interpretive clarity and ease of analysis have been achieved
by a statistical thermodynamic generalization of the BET analysis.
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