scholarly journals Positron Study of Carbon Black Parameters: Structure and Surface Area

2008 ◽  
Vol 607 ◽  
pp. 186-188
Author(s):  
J. Wang ◽  
V.O. Jobando ◽  
C.A. Quarles
Keyword(s):  
Carbon Black ◽  
Surface Area ◽  
Fine Particle ◽  
Dibutyl Phthalate ◽  
Positron Lifetime ◽  
Doppler Broadening ◽  
S Parameter ◽  
Particle Aggregates ◽  
Two Parameters ◽  
Composite Samples

Carbon black (CB) is essentially carbon in the form of extremely fine particle aggregates (100-200nm) having an amorphous molecular structure. Oil absorption or compressed dibutyl phthalate (CDBP) and iodine adsorption or nitrogen surface area (N2SA) are parameters commonly used to describe CB morphology or structure and the surface area of CB available for reaction with rubber. We have used both positron lifetime and Doppler broadening spectroscopy to study these two parameters for a variety of rubber CB composite samples. The o-Ps pickoff lifetime depends only on the type of rubber and is independent of CDBP and N2SA. However, the o-Ps lifetime intensity, I3, and the S parameter decrease with both CDBP and N2SA.

scholarly journals Charge-Induced Defect Formation in LixCoO2 Battery Cathodes: XRD and PA Spectroscopy Study

2014 ◽  
Vol 70 (a1) ◽  
pp. C1800-C1800
Author(s):  
Brigitte Bitschnau ◽  
Franz Mautner ◽  
Peter Parz ◽  
Werner Puff ◽  
Robert Würschum ◽  
...  
Keyword(s):  
Positron Lifetime ◽  
Defect Formation ◽  
Lithium Ion ◽  
Life Time ◽  
Doppler Broadening ◽  
Positron Source ◽  
S Parameter ◽  
Characteristic Variation ◽  
Electrochemical Control ◽  
Vacancy Chains

Lithium-ion batteries have developed into most advanced battery systems, e.g. laptops and mobile phones. LiCoO2 is a typical intercalation battery cathode material. However, reversible charge-discharge cycling of LiCoO2 is only possible down to 50% of the available Li-ions since further removal of Li-ions drastically reduces the capacity and cycle stability. The formation of vacancy-type defects during the charging process in LixCoO2 battery cathodes was investigated by XRD and position life-time spectroscopy and Doppler broadening of positron-electron annihilation (PA) radiation as defect specific techniques [1]. Li+-extraction, which in a battery mode corresponds to charging, was performed at 293 K under electrochemical control in a 3-electrode test-cell with a Maccor Series 4000 battery tester. The composition of the lithium-ion electrode material used was: 88wt.% LiCoO2 particles, 7 wt.% carbon black as conducting agent, 5 wt.% binder material (polyvinylidene difluoride hexafluoropropylene copolymer). Structural analysis of the electrode samples was performed by means of X-Ray diffraction using a Bruker D8 Advance diffractometer in Bragg-Brentano geometry with Cu-Kα radiation. Diffractograms were measured in the 2-Theta angle range from 150to 1300and were analysed by Rietveld refinement with the programs FULLPROF [2] and X'PertHighScorePlus (Panalytical). For positron annihilation measurements a positron source (22NaCl) was sandwiched between two identical LiCoO2 electrode samples. Positron lifetime measurements were performed with a fast-fast spectrometer with a time resolution of 221 ps. The spectra were analysed by using the program pfposfit [3]. Doppler broadening (DB) measurements were performed in a coincidence setup with two high purity Ge detectors.with energy resolution for the 511 keV annihilation γ-line in the detector system corresponds to ca. 0.88keV (FWHM). Both the Doppler broadening S parameter as well as the positron lifetime component τ1 exhibit a characteristic variation with increasing amount of Li+-extraction; the S-parameter and τ1 first increases upon decreasing x from 1 to 0.6. Further Li+-extraction causes a decrease of S and τ1 (x = 0.55), followed by a re-increase for x<0.55. Conclusions: The regime of reversible charging is dominated by vacancy-type defects on the Li+-sublattice the size of which increases with increasing Li+-extraction. Indication is found that Li+-reordering which occurs at the limit of reversible Li+-extraction (x = 0.55) causes a transition from the two-dimensional agglomerates into one-dimensional vacancy chains. Degradation upon further Li+-extraction is accompanied by the formation of vacancy complexes on the Co- and anion sublattice.

Elastic Modulus of Vulcanizates as Related to Carbon Black Structure

1973 ◽  
Vol 46 (4) ◽  
pp. 877-896 ◽  
Author(s):  
A. I. Medalia
Keyword(s):  
Elastic Modulus ◽  
Carbon Black ◽  
Surface Area ◽  
Network Structure ◽  
Dibutyl Phthalate ◽  
New Technology ◽  
Residual Effect ◽  
High Amplitude ◽  
Effective Network ◽  
Low Amplitude

Abstract The elastic modulus Gf′ of filled SBR vulcanizates has been measured as a function of strain amplitude A. At low loadings of carbon black (20 phr), where Gf′ is practically independent of A, the value of Gf′ (at 25° C, 0.25 Hz) can be predicted within 5 per eent from the gum modulus Gg′ by the Guth—Gold equation with due allowance for occluded volume, as calculated from the dibutyl phthalate absorption. At normal loadings (50 phr) the value of Gf′ can be predicted fairly well from this treatment if the measurements are made at high amplitude. At 25° C, 0.25 Hz, Gf′ is about 10 per cent higher than predicted due to the residual effect of the carbon black network. The dependence of the high-amplitude Gf′ on frequency and temperature is essentially the same for various reinforcing and semi-reinforcing blacks. Consequently, the value of Gf′ for one black can be calculated from the values found for other blacks. The dependence of Gf′ on A is primarily a function of surface area, but in two cases the dependence is unusually steep for different reasons. With graphitized blacks the low-amplitude Gf′ is higher than that of the ungraphitized blacks, but the high-amplitude Gf′ is low, probably due to molecular slippage. “New technology” blacks, including N339 and N351, give a high-amplitude Gf′ comparable to that of conventional blacks of the same dibutyl phthalate absorption, but give a higher Gf′ at low amplitude, indicating a more effective network structure.

Point Defect Characterization in CoAl Using Positron Annihilation

1998 ◽  
Vol 552 ◽  
Author(s):  
Werner Puff ◽  
Bernd Logar ◽  
Adam G. Balogh
Keyword(s):  
Point Defect ◽  
Positron Lifetime ◽  
Composition Range ◽  
Defect Characterization ◽  
Doppler Broadening ◽  
Dramatic Decrease ◽  
S Parameter ◽  
Co Concentration ◽  
Long Time ◽  
Positron Lifetime Spectroscopy

ABSTRACTVacancy-like defects in CoAl in the composition range 48.5 at.-% <Cco, < 53 at.-% are investigated by means of positron lifetime spectroscopy and Doppler-broadening measurements. The observed lifetimes in the annealed samples confirm that defects are quenched-in during the production of the samples. The values of the positron lifetime and the S-parameter decrease with increasing Co concentration. After quenching from 1400°C or 1600°C an increase in the positron parameters isobserved. Long-time annealing of the Co-rich sample shows a dramatic decrease of the positron lifetime to the expected bulk lifetime.

Low Temperature Positron Lifetime and Doppler Broadening Measurements in B2-type FeAl Alloys

2000 ◽  
Vol 646 ◽  
Author(s):  
Tomohide Haraguchi ◽  
Fuminobu Hori ◽  
Ryuichiro Oshima ◽  
Mineo Kogachi
Keyword(s):  
Low Temperature ◽  
Positron Lifetime ◽  
Vacancy Concentration ◽  
Doppler Broadening ◽  
Quenching Temperature ◽  
Al Content ◽  
Increase With Increase ◽  
S Parameter ◽  
Temperature Dependences ◽  
Positron Lifetimes

ABSTRUCTPositron lifetime and Doppler broadening measurements were carried out at a low temperature, 100K, for B2-type intermetallic compounds FeAl with composition ranges from 41.2 to 50.7 at%Al systematically in order to clarify the feature of lattice defects of the alloys. Quenching temperature dependences of positron lifetimes ranging from 573 to 1173 K was examined for alloys with 41.2, 49.0 and 50.7 at%Al. Two lifetime component analyses could not be made except for a few spectra, indicating a saturation trapping of positrons at atomic vacancies. The mean positron lifetimes are in a range of 175–195 psec, which are not corresponding to vacancy clusters but to mono and/or di-vacancies. The tendency for S-parameter to increase with increase in Al content was found. This suggests that such an increase of S-parameters is attributed to change in the fraction of atoms around the vacancies, not to increase in vacancy concentration.

Slow Positron Studies of Defects in Si-Doped GaAs

2006 ◽  
Vol 251-252 ◽  
pp. 51-58
Author(s):  
B. Godbole ◽  
N. Badera ◽  
S.B. Shrivastava ◽  
K.P. Joshi
Keyword(s):  
Point Defects ◽  
Shape Parameter ◽  
Positron Lifetime ◽  
Doppler Broadening ◽  
Slow Positron ◽  
Si Doping ◽  
S Parameter ◽  
Trapping Model ◽  
Si Doped ◽  
Line Shape Parameter

The mechanism of slow positron annihilation in Si-doped GaAs has been discussed in terms of the diffusion trapping model (DTM). The trapping of positrons has been considered in SiAs acceptors i.e. shallow defects and in VGa-SiGa vacancy complexes. The model has been used to obtain the Doppler broadening line shape parameter (S-parameter) and average positron lifetime in Si-doped GaAs, for a temperature range 20K to 290K and for different doping concentrations. Observations are made regarding the effect of doping on the nature and concentration of point defects. The change in point defect concentration due to Si- doping has been found to be proportional to the doping concentration. The effect of detrapping from the shallow defects has been found to be important at higher temperatures.

PERMEABILITY STUDIES: III. SURFACE AREA MEASUREMENTS OF CARBON BLACKS

1948 ◽  
Vol 26a (2) ◽  
pp. 29-38 ◽  
Author(s):  
J. C. Arnell ◽  
G. O. Henneberry
Keyword(s):  
Electron Microscope ◽  
Low Temperature ◽  
Carbon Black ◽  
Surface Area ◽  
Satisfactory Agreement ◽  
Nitrogen Adsorption ◽  
Average Particle ◽  
Carbon Blacks ◽  
Permeability Studies ◽  
Nitrogen Adsorption Isotherms

The modified Kozeny equation has been found to be satisfactory for the measurement of the specific surfaces of carbon blacks having average particle diameters ranging from 0.01 to 0.1 μ to within ±10%. Comparative data were obtained from electron microscope counting and from low temperature nitrogen adsorption isotherms. The three methods examined gave results that were in satisfactory agreement, except when the carbon black was porous, and then the adsorption value was extremely large.

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