Applications of a granular model and percolation theory to the electrical resistivity of heat treated endocarp of babassu nut

Emmerich, Francisco G.; Sousa, Juliana; Torriani, Íris L.; Luengo, C.A.

doi:10.1016/0008-6223(87)90013-3

Cited by 58 publications

(22 citation statements)

References 24 publications

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“…The active surface area of carbon is the surface area determined by oxygen adsorption, which has a profound correlation with the chemical reactivity of carbons [26]. In the present study, we obtained similar information on the oxygen adsorption site by using a TPD technique.…”

Section: Physicochemical Properties Of Carbonsmentioning

confidence: 80%

Structures, physicochemical properties and oxygen reduction activities of carbons derived from ferrocene-poly(furfuryl alcohol) mixtures

Ozaki¹,

Nozawa²,

Yamada³

et al. 2005

J Appl Electrochem

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The structure, physicochemical properties and oxygen reduction abilities of carbons prepared by the carbonization of mixtures of ferrocene and poly(furfuryl alcohol) were studied. X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) studies revealed that the carbons thus prepared consisted of two components; amorphous and turbostratic shell-like components. The fraction, f sharp , obtained by the analysis of the (002) peak in XRD was found to be a parameter that represented the degree of formation of the shell-like components. The formation of the shell-like components induced an increase in the mesopore volumes. Electrical conductivity increased exponentially with f sharp , which indicated that the conduction process was governed by a percolation process of the conductive shell-like components. The amount of CO-desorption by O 2 -TPD technique showed a maximum desorption at f sharp =0.3, and the further development in the sharp component led to a decrease in the CO-desorption. Mo¨ssbauer spectroscopy technique revealed the presence of a-Fe, c-Fe, Fe 1-x O and Fe 3 C in the prepared carbons, which were soluble species to acids. The oxygen reduction activity was studied in a oxygen saturated sulfuric acid solution by rotating disk electrode voltammetry. The oxygen reduction potential varied with f sharp ; initially it increased by f sharp =0.3 and then it decreased at higher f sharp values. This behavior was similar to that of CO-desorption, which meant the presence of an adequate degree of the development of the shell-like structure for maximizing oxygen adsorption. Removal of the surface metal component from the carbons by acidwashing resulted in no decrease in the oxygen reduction activities of the carbons. The nature of the active sites on the carbon materials is discussed.

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Section: Physicochemical Properties Of Carbonsmentioning

confidence: 80%

Structures, physicochemical properties and oxygen reduction activities of carbons derived from ferrocene-poly(furfuryl alcohol) mixtures

Ozaki¹,

Nozawa²,

Yamada³

et al. 2005

J Appl Electrochem

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“…Biochar structure contains mostly amorphous and some crystalline parts (conjugated aromatic compounds) [9]; the latter increase with the highest treatment temperature (HTT) [10]. The biochar matrix also includes aromatic-aliphatic groups, residual volatiles, and inorganic ashes [11] with varying morphologies of voids, cracks, and pores (at micro-, meso-, and macro-scales) [12]. Pyrolysis temperature strongly affects the molecular architecture of biochar in terms of surface area, pore number, and pore size [13], as well as surface area functional groups [14].…”

Section: Introductionmentioning

confidence: 99%

Variation in Feedstock Wood Chemistry Strongly Influences Biochar Liming Potential

2019

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Chars intended for use as soil amendment (“biochars”) vary greatly in their chemical and physical properties. In the present study, 19 Canadian temperate wood feedstocks were charred across a range of pyrolysis temperatures from 300–700 °C. The resulting 95 biochars were tested for their physio-chemical properties and liming capacity. Data indicated increasing base cation concentrations including Ca, Mg, and K (elements that characteristically form liming compounds, i.e., carbonates) as pyrolysis temperature increased. Acidic surface functional groups were analyzed with modified Boehm titration: Carboxylic and lactonic functional group concentrations decreased and phenolic group concentration increased with pyrolysis temperature. Functional group composition also varied greatly with feedstock: In particular, conifer-derived biochars produced at pyrolysis temperatures <500 °C showed much higher carboxylic and lactonic functional group concentrations than did angiosperm-derived biochars. Liming capacity was assessed using soil incubation experiments and was positively related to biochar pH. Both acidic surface functional group concentration and nutrient element concentration influenced biochar pH: we developed a non-linear functional relationship that predicts biochar pH from the ratio of carboxylic to phenolic moieties, and concentrations of Ca and K. Biochar’s liming components that are inherited from feedstock and predictably modified by pyrolysis temperature provide a basis for optimizing the production of biochar with desired pH and liming characteristics.

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“…The nanocomposites prepared by aqueous solution polymerization show a typical percolation phenomenon in terms of electrical conductivity as a function of PPy content. It has been reported that the percolation phenomenon occurs in polymer matrix‐conducting composites,20–24 and percolation theory was also introduced as shown in eq. (1) where σ m , σ 1 , and σ h are the conductivities of the medium‐, low‐, and high‐conductivity components, respectively.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, characterization, and properties of polypyrrole/expanded vermiculite intercalated nanocomposite

Lin

Tang

et al. 2008

J of Applied Polymer Sci

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The conductive polypyrrole (PPy) is intercalated into the interlayers of expanded vermiculite (EVMT) to produce the nanocomposite with high conductivity by a synchronous polymerization of pyrrole and intercalation of PPy reaction in aqueous solution. The structures and properties are characterized by the nanocomposite using powder X-ray diffraction, Fourier transform infrared spectroscopy, conductivity measurements, and stability measurements. The nanocomposite exhibited a typical percolation phenomena and the percolation threshold is around mass ratio for pyrrole to EVMT 0.22. Under optimized conditions, a PPy/EVMT intercalated nanocomposite with conductivity of 67 S cm À1 is obtained. The intercalated nanocomposite has a good environmental stability.

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Applications of a granular model and percolation theory to the electrical resistivity of heat treated endocarp of babassu nut

Cited by 58 publications

References 24 publications

Structures, physicochemical properties and oxygen reduction activities of carbons derived from ferrocene-poly(furfuryl alcohol) mixtures

Structures, physicochemical properties and oxygen reduction activities of carbons derived from ferrocene-poly(furfuryl alcohol) mixtures

Variation in Feedstock Wood Chemistry Strongly Influences Biochar Liming Potential

Synthesis, characterization, and properties of polypyrrole/expanded vermiculite intercalated nanocomposite

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