An energy dispersive X-Ray study of pure and brominated carbon black was carried out. The analysis of the

diffraction patterns reveals that the low bromine load (ca.1% mol) is trapped into the structure, without significantly

modifying it. This allows the application of the difference methods, widely tested for electrolyte solutions, inorganic

matrices containing metals and isomorphic substitutions

Carbone, M

Gontrani, L

Marilena Carbone

Lorenzo Gontrani

Crossref

Brominated carbon black: An EDXD study

Cineca Institutional Research Information System

An energy dispersive X-Ray study of pure and brominated carbon black was carried out. The analysis of the
diffraction patterns reveals that the low bromine load (ca.1% mol) is trapped into the structure, without significantly
modifying it. This allows the application of the difference methods, widely tested for electrolyte solutions, inorganic
matrices containing metals and isomorphic substitutions

CARBONE, MARILENA

Gontrani, L.

English

An energy dispersive X-Ray study of pure and brominated carbon black was carried out. The analysis of the diffraction patterns reveals that the low bromine load (ca.1% mol) is trapped into the structure, without significantly modifying it. This allows the application of the difference methods, widely tested for electrolyte solutions, inorganic matrices containing metals and isomorphic substitutions

Carbone, Marilena

GONTRANI, Lorenzo

Archivio della ricerca- Università di Roma La Sapienza

Archivio della Ricerca - Università di Roma Tor vergata

Brominated carbon black: An EDXD study
Marilena Carbone and Lorenzo Gontrani 
 
Citation: AIP Conference Proceedings 1603, 47 (2014); doi: 10.1063/1.4883041 
View online: http://dx.doi.org/10.1063/1.4883041 
View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1603?ver=pdfcov 
Published by the AIP Publishing 
 
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Brominated Carbon Black: an EDXD Study  
Marilena Carbone1, Lorenzo Gontrani2,3,a)  
Università di Roma Tor Vergata, Via della Ricerca Scientifica 1 I-00133 Roma, 
Italy 
1 Università di Roma Tor Vergata, Via della Ricerca Scientifica 1 I-00133 Roma, Italy 
2 CNR-Istituto di Struttura della Materia, Via del Fosso del Cavaliere, I-00133 Roma, Italy 
3Dipartimento di Chimica- Università Sapienza, P.le Aldo Moro 5, I-00184 Roma, Italy 
 
a)Corresponding author: lorenzo.gontrani@uniroma1.it 
Abstract. An energy dispersive X-Ray study of pure and brominated carbon black was carried out. The analysis of the 
diffraction patterns reveals that the low bromine load (ca.1% mol) is trapped into the structure, without significantly 
modifying it. This allows the application of the difference methods, widely tested for electrolyte solutions, inorganic 
matrices containing metals and isomorphic substitutions.  
Keywords: Carbon Black, EDXD, Bromine, Diffraction 
PACS: 61, 82 
 
INTRODUCTION 
 
Carbon black is a widely used material in many applications. It can be used as filler in elastomers, plastics and 
paints, to modify the mechanical, electrical and optical properties of the materials it is dispersed in. When embedded 
in plastics it imparts UV protection, electrical conductance and range of darkness and reinforcement. When used as 
filler in rubbers it changes the fracture behavior, improves abrasion and failure properties.  Carbon black is 
electrically conductive and imparts good conductivity to thermoplastic polymers [1-5]. Furthermore, it is used as 
pigment in xerographic toner since it plays a role in maintaining a suitable level in electric charge on the toner.  
Carbon black primary characteristics responsible for its properties are the particle size, the aggregate size, the 
morphology and microstructure of the aggregates, porous structure, nature of the surface, surface area [6]. Carbon 
black technical performances may be improved by halogenation and bromination, in particular [7].  
Furthermore, brominated carbon systems are synthons for further derivatization, since they are chemically reactive 
and the Br atoms can be substituted by alcohols (Williamson ether synthesis or Grignard Reactions) or glycols, etc., 
but more importantly by amines or diamines, too. Using this approach a covalent bonding of organic molecules or 
polymers onto the carbon material surfaces is possible and a wide range of new applications is on the horizon. 
Besides, Br addition on graphene lattice sp2 carbon atoms sp3 hybridized carbon atoms at domain edge or defects are 
also available for substitution or other reactions. 
Several chemico-physical methods were used for bromination of carbon system including the use of bromine, 
bromoform and mixtures of both. Plasma reactions yield highly effective, highly selective bromination, expressed as 
absence of side-reactions. Microwave methods may also be used, in the spark-assisted variant [8]. The resulting 
graphite halide can easily be exfoliated into monolayer graphene in organic solvents. The bromination may occur as 
a radical substitution of hydrogen by bromine atoms [9] or as an addition to a carbon-carbon double bond. A 
recently reported method for bromination of carbon systems is an ultrasound assisted one [10].   
The structural properties of carbon-based materials upon bromination are method- and mechanism-dependent. As 
for carbon black, both covalent bromine-carbon bonds and molecular bromine entrapment are possible interactions.  
In the current paper, microwave-assisted bromination was used as carbon black halogenation method. The product 
were, then, studied by Energy Dispersive X-ray Diffraction. In particular, in order to isolate the contribution of the 
C-Br interaction from the overall curve, the difference method was applied, i.e. scattered intensities of the NANOFORUM 2013AIP Conf. Proc. 1603, 47-52 (2014); doi: 10.1063/1.4883041©   2014 AIP Publishing LLC 978-0-7354-1237-8/$30.0047
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brominated and non-brominated couples of carbon systems were collected and normalized. Subsequently, the 
scattered intensity of the non-brominated compound was subtracted from the corresponding brominated one.  
This method, originally developed for isomorphic electrolyte solutions and later on applied to SiO2 matrices 
containing small traces of different metals and to bromine salts [11-17], is based on the assumption that the 
solute/matrix concentration (carbon black in this case) is almost identical in the samples, so that its scattering 
contribution can be regarded as a constant and can be subtracted from the total curve to obtain a difference spectrum 
to which only the remaining structural correlations contribute. 
 
Experimental Methods 
A weighed amount of carbon black N220 was placed in a 50 ml round bottomed flask, then liquid bromine was 
added and the flask was tightly closed with a glass stopper and with a rubber band to avoid any bromine leakage. 
The mixture was sonicated by submerging large part of the round-bottomed reaction flask inside the tank of the 
ultrasonic cleaner which was filled with water at the suggested filling level. After 2h sonication, the bromine in 
excess was distilled off under reduced pressure. 
Energy Dispersive X-ray Dispersion (EDXD) measurements of the two samples were performed using a 
noncommercial energy scanning diffractometer [18-20]. The white Bremsstrahlung emitted by a tungsten tube (50 
kV, 40 mA) was used as radiation source. The samples were loaded in a quartz capillary (2 mm diameter, 80 mm 
length). Scattering intensities of the sample were obtained by merging several measurements performed in 
correspondence of eight scattering angles θ = 24°, 15.5°, 5°, 10.5°, 8°, 3°, 1°, .5°. The larger number of angles than 
normally used in this technique, where five angles are enough to yield I(q) spectra (see below) ranging from 0.12 to 
19.56 Å-1 [21], was necessary because bromine fluorescence lines fall amid the bremsstrahlung, so that the usable 
portion of the radiation is beyond bromine Kβ line. The presence of the very sharp bromine fluorescence lines is 
clearly visible in the diffracted intensity vs energy pattern registered, for instance, at 15.5 degrees, see Fig. 1. The 
expression for q is q= cost *E* sin θ, where cost is equal to 1.014 when E is expressed in keV and q in Å-1. The 
primary beam intensity I0(E) was measured  
 
 
FIGURE 1 – Diffracted intensity measured at θ = 15.5°. Brominated Carbon Black: red; Carbon Black: green 
 48
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directly, by reducing the tube current to 10 mA without the sample with the two slits after the source and before 
the detector “closed” (i. e. very narrow). Transmission of the samples and of the empty capillary was measured 
under the same conditions. Both quantities are needed to carry out the necessary absorption corrections to 
experimental data [22]. The various angular data were normalized to a stoichiometric unit of volume containing one 
carbon atom and merged to yield the scattered intensity, IE.U. (q), expressed in electron units. Finally, the 
independent scattering was subtracted from IE.U. (q) to obtain the total static structure function i(q), also termed 
“reduced intensity”, according to the relation 
 
          
   
€ 
i(q) = IE .U .(q) − xi∑ f i2                           
(1)    
In this equation, xi and fi are the number concentration and the scattering factor of carbon atoms, respectively. This 
function was multiplied by q and by a q-dependent sharpening factor, M(q), to improve the curve resolution at high 
q. The expression for M(q), using carbon as the “sharpening atom”, is 
 
€ 
M(q) =
fC
2(0)
fC
2(q)
exp(-0.01q2 )                                  (2) 
 
The structure function pattern were then Fourier-Transformed to obtain the Radial Distribution Function in 
distance space, according to the relation 
 
               (3)             
 
 
All data treatment was performed with in-house written codes.  
 
 
FIGURE 2 - Structure Function qI(q)M(q); Brominated Carbon Black (green); Carbon Black (red) 
  
€ 
D(r) − 4πr 2ρ0 = 4πr
2ρ0(G(r ) −1) =
2r
π
qi(q)M (q)sin(rq)dq
0
∞
∫ 49
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 Results and Discussion 
The measured structure functions are plotted in Fig. 2 (CB, green; Br-CB, red) and show patterns of large peaks 
typical of amorphous systems. Overall, the two functions show several differences, despite the very small 
concentration of bromine (1.0% molar ratio). In particular, a general increase of peak height is observed in the low q 
and central region of the spectrum. The pre-peak (or FSDP, First Diffraction Peak) position moves from 0.34 Å-1 in 
pure CB to 0.28 Å-1 in Br-CB, while the two tallest peaks (1.70 and 5.30 Å-1) gain intensity without changing 
position. All these features can be associated with the formation of new carbon-bromine and bromine-bromine 
contacts that are longer than carbon-carbon ones, causing an overall increase of longer structural correlations. The 
dependence of the peak position on the distance of two individual point scatterers is originated by the cardinal sine 
function (sinc) of the Debye formula [23]: 
 
  
€ 
I (q) = xi
i≠ j
∑ x j fi f j
sin(qrij )
qrij
* exp(−0.5q2σ 2ij )                                                                      (4) 
 
In this expression, fij and xij are the q-dependent scattering factors and the numerical concentration of the 
scatterers respectively, rij is the relative distance and σij a Gaussian-type strain function associated to it, necessary to 
model the spatial uncertainty when a single model configuration is used. As regards the two pre-peaks, they are 
generally attributed to medium-range order in liquids and amorphous solids [24, 25], and are related to effective 
Bragg distances (2π/q) occurring in the partially ordered system, that correspond to 18.48 Å and 22.44 Å in distance 
space, respectively. Qualitatively speaking, all features seem to indicate that the insertion of even smaller quantities 
of bromine (1%) into CB structure causes the system to enlarge, if not to swell. 
  
A further structural analysis was carried out according to the method based on difference curves. In Br-CB 
spectrum, once CB curve has been taken out, only Br-Br and Br-C contributions are left. The difference curve Br-
CB - CB is reported in Fig. 3. The already marked increase of peak heights already discussed for Fig. 2 is very 
evident in the difference curve. 
 
  
FIGURE 3 - Difference Structure Function qI(q)M(q): brominated Carbon Black minus Carbon Black 50
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The presence of new Br-C contacts in the Br-CB sample is more evident in the difference between Radial 
Distribution Functions D(r)(Br-CB) – D(r) (CB), reported in Fig. 4. Among these contacts, though, the presence of 
covalent bonds between carbon and bromine is negligible, since there is no peak around 1.9-2.0 Å. The first visible 
peak is at 2.30 Å, and corresponds to the typical Br-Br distance of diatomic molecular bromine; all the peaks that 
follow can be ascribed to larger bromine-carbon contacts. 
 
 
FIGURE 4 – Difference Radial Distribution Function D(r): brominated Carbon Black minus Carbon Black 
 
CONCLUSIONS 
Carbon black N220 and its brominated analogue, obtained by an ultrasound assisted procedure, were investigated 
by Energy Dispersive X-ray Diffraction. In spite of the low bromine load (1%) structural information could be 
achieved, by application of the difference method. It was found that the first structural peak in the difference radial 
curve corresponds to the typical distance of molecular bromine, which appears to be the dominant species embedded 
in the carbon black matrix. 
ACKNOWLEDGMENTS 
The authors wish to thank Prof. Ruggero Caminiti for providing EDXD spectra and for general guide and 
assistance and Dr. Franco Cataldo for providing the samples.  Computational support from CASPUR (grant std11-
465, std12-011) is acknowledged; L. G. acknowledges support from FIRB (RBFR086BOQ) 
 
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Brominated carbon black: An EDXD study

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