Positron Lifetime as a Nanoprobe for Free Volume Distribution in High Density Polyethylene–Carbon Black Conducting Composites

Patnaik,; AZhu,; ZYang,; GSun,

doi:10.1002/(sici)1521-396x(199809)169:1<115::aid-pssa115>3.3.co;2-t

Cited by 5 publications

(8 citation statements)

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“…A certain effect of morphology on the electrical behavior of composites was shown for the composites of polymer blends and CB 7–9. Patnaik et al have studied electrical conductivity of HDPE–CB composites using Positron Annihilation Lifetime Spectroscopy and suggested existence of three different morphological domains with different free volumes 14. In our experiments, LDPE as a crystalline branched polymer has a morphology with the possibility of formation of structural parts in percolation range.…”

Section: Resultssupporting

confidence: 61%

“…If we compare the results in Figures 2 and 3, we notice in Figure 2 the absence of a clear percolation threshold, whereas Figure 3 shows clear increases of conductivity at the low (15% CB) and higher (23% CB) percolation points. If we take into consideration the results of Patnaik et al14 about structural inhomogeneity in HDPE–CB composites and our previous results of the effects of charge trapping in crystalline LDPE,12, 13 the presence of two peaks on the graphs in Figure 3 can be attributed to different dispersions of CB particles in structural inhomogeneities and micro defects of LDPE. A more significant frequency dependence at the higher percolation peak than at the low one can be related to different surroundings of CB fillers.…”

Section: Resultsmentioning

confidence: 58%

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Clinical images: Infarct‐associated bone sarcoma in the clinical context of systemic lupus erythematosus

Oliveira¹,

Martins²

2012

Arthritis & Rheumatism

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A biopsy was performed, and the histopathologic diagnosis was malignant fibrohistiocytoma. The lesion was resected with reconstruction of the tibia using a fibular graft, without recurrence at 5-year followup. SLE and corticosteroids are well-established risk factors for osteonecrosis. Irrespective of their cause, areas of osteonecrosis involving metaphysis and diaphysis of long bones (infarcts) can be associated with sarcomas over time, unlike those affecting subarticular regions and epiphysis (avascular necrosis) (1-3). Histologic types include malignant fibrohistiocytoma (the most common), osteosarcoma, fibrosarcoma, angiosarcoma, and epithelioid hemangioendothelioma (1-3). Nearly 75% of patients have multiple foci of infarcts, men are affected twice as frequently as women, and the distal femur and proximal tibia are the typical sites of this rare complication (2). Reactive tissue at the periphery of the infarcts has been suggested as the source of these sarcomas (1,2). The appearance of pain with an aggressive lesion seen by radiography at a site of an evident infarct should raise suspicion of infarct-associated bone sarcoma (1,2), which usually has a poor prognosis (3).

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 58%

Clinical images: Infarct‐associated bone sarcoma in the clinical context of systemic lupus erythematosus

Oliveira¹,

Martins²

2012

Arthritis & Rheumatism

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“…They found that the variation of the positron annihilation parameters is sensitive to protonation level and consistent with the metal–granule island model. The electrical conductivity (at room temperature) of high‐density polyethylene–carbon black (HDPE–CB) switching composites as a function of the conductivity filler (CB) content was studied by Patnaik et al16 using PALS. The CB imparted high conductivity to its composites, starting at a low level of loading.…”

Section: Introductionmentioning

confidence: 99%

Effect of doping polyacrylic acid with some dopants as studied by different techniques

Mostafa

Mohamed

2002

J of Applied Polymer Sci

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ABSTRACT:The molecular weight of polyacrylic acid (PAA) was determined by a viscometric method using NaNO 3 as solvent at 30°C. The specific electric conductivities () of PAA as well as PAA doped with carbon black (CB), chromium oxide (Cr 2 O 3 ), and cupferron with different concentrations (from 0.25 to 1 wt %) were measured at a temperature range 360 -400 K. IR spectra of some polymers were determined and it was shown that when PAA was doped with 0.5 wt % CB, a COOOC band appeared at 775-875 cm Ϫ1 . The positron annihilation lifetime (PAL) spectra in PAA doped with the above-mentioned dopants were measured as a function of their concentrations. It was observed that the short lifetime intensity I 1 decreased, whereas the intermediate lifetime intensity I 2 , which is related to the conductivity of the material, increased with increasing the wt % of Cr 2 O 3 and cupferron as well as at low concentrations of CB. These results are discussed in terms of the conducting island model. It was found that there were distinct positive relationships between and I 2 .

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“…Two common observations can be deduced from these figures; (i) both τ 3 and I 3 decrease as the filler content increases (ii) τ 3 and I 3 for the G filled composites (G‐samples) have higher values than those of the CB filled composites (CB‐samples). To interpret the first observation, it should be mentioned that adding fillers, CB or G, to silicone rubber matrix inhibits the formation of o‐Ps due to filling up some of the free‐volume holes in this matrix and as a result the size and concentration of these holes decrease . In such case the positron has a higher probability to annihilate in the filler than to form o‐Ps.…”

Section: Resultsmentioning

confidence: 99%

Correlation of electrical and swelling properties with nano free-volume structure of conductive silicone rubber composites

et al. 2013

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The present study focuses on finding a correlation between the positron annihilation parameters of silicone rubber polydimethylsiloxane (PDMS) composites loaded with different conductive fillers and their swelling and electrical properties. Four types of conductive fillers have been used in this study, i.e., carbon black (CB), graphite (G), copper, and nickel powders. The investigated swelling parameters for PDMS composites such as the maximum degree of swelling Qm%, the penetration rate, P, and consequently the diffusion coefficient, D, decreased with increasing the filler content due to the reduction of the size of free‐volume, which could be observed through a decrease of the probability of ortho‐positronium (o‐Ps) formation I3, that has been measured by the positron annihilation spectroscopy (PALS). Accordingly, a positive correlation has been found of 76.78% and 61.1% between Qm% and the o‐Ps lifetime τ3, representing the size of free‐volume for the CB and G filled composites, respectively. It is worthwhile, mentioning that the CB filled composites exhibit relatively low values of P, D, and Qm% as compared to the G filled composites due to the difference in the physical properties of the filler, particle size, surface area as well as the tendency of the filler particles to make aggregates. On the other hand, the variation of the diffusion coefficient with the relative fractional free‐volume Fr is found in good agreement with the Fujita's free‐volume theory. On the other hand, the electrical conductivity increases with increasing the conductive filler content. Positive temperature coefficient of conductivity (PTCC) behavior is detected, except for the composite containing 20 or 25 phr CB, which showed a metallic behavior. Besides, CB filled PDMS composites exhibit higher electrical conductivity as compared to the composites filled with the other three fillers. The electrical conductivity ln (σ) is positively correlated with the probability of free annihilation of positrons at interfaces I2, thus suggesting an increase in the electron density with the filler content. The activation energy of conduction, Ea, decreases with the increase in the loading of conductive filler. Moreover, it was noticed that Ea varies with the filler type, the values of Ea increase as the particle size of the filler increases. Finally, a correlation between the free‐volume Vf, determined by PALS with the DC electrical conductivity ln(σ) is found to be in accordance with Miyamoto and Shibayma model. POLYM. COMPOS., 34:2105–2115, 2013. © 2013 Society of Plastics Engineers

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Positron Lifetime as a Nanoprobe for Free Volume Distribution in High Density Polyethylene–Carbon Black Conducting Composites

Cited by 5 publications

References 0 publications

Clinical images: Infarct‐associated bone sarcoma in the clinical context of systemic lupus erythematosus

Clinical images: Infarct‐associated bone sarcoma in the clinical context of systemic lupus erythematosus

Effect of doping polyacrylic acid with some dopants as studied by different techniques

Correlation of electrical and swelling properties with nano free-volume structure of conductive silicone rubber composites

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