Abstract
Effects of physical and chemical states of iron-based catalysts on the formation of carbon-encapsulated iron nanoparticles (CEINs) synthesized thermally from kraft lignin were investigated. Experimental results indicated that if solution-based iron nitrate (FeN) was used as an iron source for the catalyst, CEINs observed were α-Fe and γ-Fe-based cores encapsulated by few layers graphitic-carbon (mostly 1–5 layers) and the majority of these CEINs were embedded in amorphous carbon matrix. The formation of graphitic-carbon shells is believed based on the dissolution and precipitation mechanism of amorphous carbon acting as the carbon source. If solid-based iron nanoparticles (FePs) were used as the catalyst, CEINs observed were α-Fe, γ-Fe, and Fe3C-based cores encapsulated with tangled graphitic-carbon nanoribbons and carbon tubules and the majority of these CEINs were found along the edge of amorphous carbon matrix. The growth of tangled graphitic-carbon nanoribbons and carbon tubules is based on a chemical vapor decomposition process, i.e., the carbonaceous gases from kraft lignin decomposition served as the carbon source.
Highlights
Lignin is the most abundant, highly cross-linked aromatic biopolymer on Earth, and mainly composes of carbon (~60%), oxygen (~30%), and hydrogen (~6%)
Experimental results showed that carbon-encapsulated iron nanoparticles (CEINs) synthesized from twotwo different catalyst systems had had different microstructures because of two different reaction processes illustrated in Figure different microstructures because of two different reaction processes illustrated in Figure precursor system, the initial degree of contact between iron and lignin was high because
Fe was converted to iron nanoparticles which were tightly trapped into amorphous carbon matrix
Summary
Lignin is the most abundant, highly cross-linked aromatic biopolymer on Earth, and mainly composes of carbon (~60%), oxygen (~30%), and hydrogen (~6%). More than 70 million tons of lignin is produced from wood pulping process every year as low-value by-products [1]. Lignin contains more than 60% of carbon and can be potentially used for the production of value-added graphitic-carbon nanostructures like carbon-encapsulated iron nanoparticles (CEINs). With appropriate functionalization [3], CEINs can be used in various applications required severe temperature and humidity conditions such as data storage, catalyst, environmental remediation, and biomedical area because the carbon shell structure prevents oxidation of iron nanoparticles [4]. CEINs can be produced through denotation [5], laser irradiation [6], flame synthesis [7], arc discharge [8,9] and chemical vapor decomposition (CVD) methods [10]. CVD process is normally used for the production of graphitic-carbon nanostructures, where carbonaceous
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