The Cobalt Oxide and Calcium-Aluminum Oxide nano-catalysts were analyzed using Scanning Electronic Microscopy (SEM), X-ray diffraction (XRD), and dispersive X-ray spectroscopy (EDX) techniques. Preliminary results showed that the particles of Cobalt Oxide exhibit sponge like morphology and homogenous distribution as per confirmation via SEM. Its average particle size ranges to 30.6 nm demonstrating enormous number of pores and aggregative in nature. Its various peaks were ranging from 19.2 to 65.4 after XRD analysis. The highest intensity was observed at 36.9 position. The energy dispersive spectroscopy techniques were used to calculate the elements present in sample according to their weight and atomic percentage. The cobalt oxide contain cobalt as the most abundant element with 46.85 wt% and 18.01 atomic percent. It contain oxygen with 30.51 wt% and 43.19 atomic percent. Whereas, SEM of calcium aluminum oxide showed random morphology. According to the calculation of Scherrer equation regarding XRD analysis, it was distributed homogenously with particle size ranges from 30 to 40 nm. Its porous morphology was due to the interconnecting gaps between different particles. It result the eight peaks ranging from 18.1 to 62.7 in XRD spectrum. The highest intensity observed at 35.1 with average crystallite particle size of 25.6 nm. The calcium aluminum oxide contain aluminum 7.45 wt% and 6.93 atomic percent. The calcium was the most abundant element with54.7 wt% and 34.24 atomic percent followed by oxygen with 37.26 wt% and 58.42 atomic percent. It was concluded that the SEM, XRD, and EDX are the most significant techniques to characterize nano-catalysts in particular and other compounds generally.

1. R E S E A R C H A R T I C L E
Characterization of Cobalt Oxide and Calcium-Aluminum
Oxide nano-catalyst through Scanning Electron Microscopy,
X-ray diffraction, and Energy Dispersive X-ray Spectroscopy
Iram Gul1
| Shujaul Mulk Khan1
| Tariq Mehmood2
| Zeeshan Ahmad1
|
Hussain Badshah1
| Hussain Shah3
1
Department of Plant Sciences, Quaid-i-Azam
University, Islamabad, Pakistan
2
Department of Nano-science and
Technology, NCP, Quaid-i-Azam University
Campus, Islamabad, Pakistan
3
Department of Plants and Environmental
Protection, PARC, Islamabad, Pakistan
Correspondence
Shujaul Mulk Khan, Department of Plant
Sciences, Quaid-i-Azam University, Islamabad,
Pakistan.
Email: shujaqau@gmail.com
Review Editor
Paul Verkade
Abstract
The Cobalt Oxide and Calcium-Aluminum Oxide nano-catalysts were analyzed using
Scanning Electronic Microscopy (SEM), X-ray diffraction (XRD), and dispersive X-ray
spectroscopy (EDX) techniques. Preliminary results showed that the particles of
Cobalt Oxide exhibit sponge like morphology and homogenous distribution as per
confirmation via SEM. Its average particle size ranges to 30.6 nm demonstrating
enormous number of pores and aggregative in nature. Its various peaks were ranging
from 19.2 to 65.4 after XRD analysis. The highest intensity was observed at 36.9
position. The energy dispersive spectroscopy techniques were used to calculate the
elements present in sample according to their weight and atomic percentage. The
cobalt oxide contain cobalt as the most abundant element with 46.85 wt% and 18.01
atomic percent. It contain oxygen with 30.51 wt% and 43.19 atomic percent.
Whereas, SEM of calcium aluminum oxide showed random morphology. According
to the calculation of Scherrer equation regarding XRD analysis, it was distributed
homogenously with particle size ranges from 30 to 40 nm. Its porous morphology
was due to the interconnecting gaps between different particles. It result the eight
peaks ranging from 18.1 to 62.7 in XRD spectrum. The highest intensity observed at
35.1 with average crystallite particle size of 25.6 nm. The calcium aluminum oxide
contain aluminum 7.45 wt% and 6.93 atomic percent. The calcium was the most
abundant element with54.7 wt% and 34.24 atomic percent followed by oxygen with
37.26 wt% and 58.42 atomic percent. It was concluded that the SEM, XRD, and EDX
are the most significant techniques to characterize nano-catalysts in particular and
other compounds generally.
K E Y W O R D S
Calcium-Aluminum Oxide, Cobalt Oxide, nanotechnology, Scanning Electron Microscopy, X-
ray diffraction
1 | INTRODUCTION
After the invention of Atomic Force Microscope (AFM) and Scan-
ning Tunneling Microscope (STM) in 1980s, the atoms and
Review Editor
Paul Verkade
Received: 12 November 2019 Revised: 28 January 2020 Accepted: 16 April 2020
DOI: 10.1002/jemt.23504
1124 © 2020 Wiley Periodicals, Inc. Microsc Res Tech. 2020;83:1124–1131.wileyonlinelibrary.com/journal/jemt

2. molecules were used and controlled at nanoscale. Nanoscience and
technology work at very small scale known as nanoscale. The prop-
erties of materials that is electronic, magnetic, physical, or chemical
at nanoscale are much diverse from larger scale properties of the
same. In addition, the products formed in the industry through
nanoscale technologies have smallest size and hence best perfor-
mance in various applications. The field of nanotechnology has
been progressing very quickly due to the inventions of AFMs and
STMs. This caused industrial revolution that profit 1–2 trillion dollar
marketing during 2015. Its application in industry will be more
advanced up to 40–50 years (Lux Research, 2010). The growth of
nanotechnology causes development in engineering technology and
science as well. The techniques equiped with nanotechnology cover
different fields of science for example organic chemistry, molecular
biology, microfabrication, surface science, biology, semiconductor
physics and Plants anatomy etc (Khan et al., 2019).
Nanotechnology has been growing rapidly and created many
research offshoots in last few years (Hullmann, 2006). It plays an
important role in many application domains and technological com-
petence of a country. Whereas, nanoparticles are small particles that
behave as a whole unit with respect to its properties and transport
ranges from 1 to 100 nm in size (Mohanraj & Chen, 2006). Currently,
the nanoparticle research gain rigorous scientific interest due to its
potential important applications in fields of electronic, optical, and
biomedical sciences (Hewakuruppu et al., 2013; Taylor et al., 2013;
Taylor, Otanicar, & Rosengarten, 2012). Like, cobalt oxide nanoparti-
cle have significant role in electronic gas sensor and lithium ion bat-
teries. It also has applications in gene therapy, hyperthermic, and
drug delivery. Aluminum oxide nanoparticle has diverse biomedical
applications due to their unique physicochemical and structural char-
acteristics. These nanoparticles are generally characterized by their
disparity, surface area, shape, and size (Jiang, Oberdörster, &
Biswas, 2009) though scanning electron microscopy (SEM), energy
dispersive spectroscopy (EDS), and powder X-ray diffraction (XRD)
(Fedlheim & Foss, 2001; Sepeur, 2008; Shahverdi, Shakibaie, &
Nazari, 2011). Furthermore, the wavelengths of light ranges from
300 to 800 nm are commonly used for characterization of changed
metal nanoparticles (Fedlheim & Foss, 2001). Whereas, the wave-
length ranges from 400 to 450 nm and 50 to 550 nm is measured
through spectrophotometric absorption for characterizing the gold
and silver nanoparticles (Huang & Yang, 2004). The transmission and
scanning electron microscopy are typically used for size and mor-
phological characterization of nanoparticles (Schaffer, Hohenester,
Trügler, & Hofer, 2009). While, XRD was mainly used for characteri-
zation of crystalize size and crystal orientation of the nanoparticles
(Sun, Murray, Weller, Folks, & Moser, 2000). The EDS technique is
commonly used to determine the elemental composition of metal
nanoparticles (Strasser et al., 2010).
Therefore, the current study was carried out to synthesize
cobalt oxide and calcium-aluminum oxide nano-catalysts via
coprecipitation and Top down Ball Mill method and its characteriza-
tion through SEM, XRD, and energy dispersive X-ray spectroscopy
techniques.
2 | MATERIALS AND METHODOLOGY
2.1 | Preparation of Cobalt Oxide nanoparticles by
coprecipitation
Sodium hydroxide (NaOH crystals) and Cobalt Nitrate were the essen-
tial chemicals used during this experiment. 100 ml of distilled water
was taken in 500 ml beaker, added with 15 g Cobalt Nitrate, stirred
the solution through magnetic stirrer, and kept on Hot Plate. At the
same time, 0.1 M Sodium Hydroxide (NaOH) solution was pre-
pared, put in burette (100 ml) and titrated against cobalt nitrate.
During titration procedure, the pH increased slowly and gradually
precipitate was formed. The titration process was stopped when
its pH was reached to 10 and blackish green in color (Mahmood &
Hussain, 2010). Subsequently, when precipitate settled down, it
was washed with distilled water to remove all the impurities. The
precipitate was kept in oven for an hour at 100
C to remove all the
moisture and water completely. Furthermore, it was calcined at
500
C for 3–5 hours in furnace. The calcined nanoparticles were
kept for cooling, grinded and put into plastic sample vials with the
help of steel spatula for SEM, XRD, and EDX analyses (Mahmood
Hussain, 2010).
2.2 | Preparation of Calcium-Aluminum Oxide
nano-catalyst by using top down Ball Mill method
The Calcium-Aluminum Oxide nano-catalyst was synthesized in labo-
ratory through Ball Milling process. The calcium hydroxide (2 g) and
aluminum oxide (2 g) was weighted and transformed into fine
nanoparticles by Ball Mill method at 200 rpm at room temperature for
2 hr. In this process, Calcium Oxide and Aluminum was placed in Ball
Mill separately and subjected these powder to high-energy collision
from the Balls. After that 2 hr were given to obtain nano size desired
particles. After that these nano size particles were mixed in equal
amounts and calcined at 500
C for 3 hr in oven, to investigate the
proficiency as mixture of Calcium-Aluminum oxide nanoparticles. The
fine nano catalyst was obtained after calcination procedure and char-
acterized through XRD, EDX, and SEM.
3 | RESULTS
3.1 | Characterization of cobalt oxide nanoparticle
The cobalt oxide nanoparticles were analyzed through SEM, XRD, and
EDS techniques. The detail description is as follows.
3.1.1 | SEM of Cobalt Oxide nanoparticles
The SEM was used for the determination of morphology and size
of the nanoparticles. The particles of cobalt oxide showed sponge
GUL ET AL. 1125

3. like morphology that distribute homogenously. Its particles size
ranges to 30.6 nm, which was according to the calculation of
Scherrer equation for XRD analysis. These particles demonstrate
enormous number of pores and aggregative in nature. In addition
to, some of the particles were smaller in size and was connected
to the larger ones (Figure 1).
3.1.2 | XRD spectrum of Cobalt Oxide (CoO)
nanoparticles
The XRD technique shows crystalline size and chemistry of the par-
ticles. The size of Cobalt Oxide nanoparticles were characterized by
XRD (Model No. D8 Advance Bruker Company). It was carried out at
10–60 2θ values. The Scherrer equation was used from full width
half maximum (FWHM) of peak positions for size calculation of
Cobalt Oxide nanoparticles. The various peaks were found in XRD
spectrum ranging from 19.2 to 65.4 (Table 1). The highest intensity
was observed at 36.9 position. The spectrum show cubical structure
of Cobalt Oxide particles with average 30.6 nm crystallite sizes
(Figure 2).
3.1.3 | EDS peaks spectra of Cobalt Oxide (CoO)
nanoparticles
The EDS techniques were used to calculate the elements present in
sample according to their weight and atomic percent. The Cobalt
Oxide contain cobalt as the most abundant element with 46.85 wt%
FIGURE 1 The SEM of cobalt
oxide nanoparticles micrograph
showing different resolutions.
SEM, Scanning Electron
Microscopy
TABLE 1 The peak positions of XRD spectrum of Cobalt Oxide
(CoO) nanoparticles
Peak position 2θ (degree)
FWHM β
(degree)
Crystallite
size (nm)
19.2 0.228 42
30.3 0.312 27
36.9 0.388 23
43.7 0.254 33
59.2 0.218 21
65.4 0.272 38
Average crystallite size
(nm)
30.6 nm
Abbreviations: FWMH, full width half maximum; XRD, X-ray diffraction.
1126 GUL ET AL.

4. and 18.01 atomic percent. It contain oxygen with 30.51 wt% and
43.19 atomic percent. The Carbon impurities were due to Carbon taq
used for conducting SEM analysis. While, the iron impurities were due
to iron tool used for placing the sample in machine (Table 2 and
Figure 3).
3.2 | Characterization of Calcium Aluminum Oxide
nanoparticle
The Calcium Aluminum Oxide nano-particles were analyzed by
SEM, XRD, and EDS techniques. Its detail description is as
follows.
3.2.1 | SEM of Calcium Aluminum Oxide
nanoparticles
The SEM was mainly used for the determination of size and mor-
phology of the nanoparticles. It was resulted that the SEM of Cal-
cium Aluminum Oxide showed random morphology. According to
the calculation of Scherrer equation regarding XRD analysis, it was
distributed homogenously with particle size ranges from 30 to
40 nm. In addition to, the porous morphology was due to the inter-
connecting gaps between different particles. Calcium Aluminum
Oxides showed that few smaller particles were attached to the larger
particles and quite clear with low agglomeration or aggregates
(Figure 4).
FIGURE 2 The XRD spectrum of Cobalt Oxide (CoO)
nanoparticles showing various peaks of elemental compositions. XRD,
X-ray diffraction
TABLE 2 Elemental composition of the EDS spectra of (CoO)
nanoparticles
Elements Weight percent Atomic percent
Carbon 20.01 37.34
Oxygen 30.51 43.19
Iron 2.62 1.06
Cobalt 46.85 18.01
Abbreviation: EDS, energy dispersive spectroscopy.
FIGURE 3 The EDS of Cobalt Oxide nanoparticles micrograph showing elemental composition. EDS, energy dispersive spectroscopy [Color
figure can be viewed at wileyonlinelibrary.com]
GUL ET AL. 1127

5. FIGURE 4 The SEM of
Calcium Aluminum Oxide
nanoparticles' micrograph
showing different resolutions.
SEM, Scanning Electron
Microscopy
TABLE 3 The peak positions of Calcium Aluminum Oxide
nanoparticles in XRD spectrum
Peak position 2θ (degree)
FWHM β
(degree)
Crystalline
size (nm)
18.1 0.454 19
28.8 0.230 39
29.5 0.202 45
34.2 0.451 20
47.2 0.635 15
50.9 0.388 25
54.4 0.456 21
62.7 0.485 21
Average crystallite size
(nm)
25.6 nm
Abbreviations: FWMH, full width half maximum; XRD, X-ray diffraction.
FIGURE 5 Eight different peaks in XRD spectrum of Calcium
Aluminum Oxide. XRD, X-ray diffraction
1128 GUL ET AL.

6. 3.2.2 | XRD spectrum of Calcium Aluminum Oxide
nanoparticles
The Calcium-Aluminum Oxide nanoparticles were characterized by
XRD (Model No. D8 Advance Bruker). The XRD sample of nanoparti-
cle was carried out at 10–70 2θ values. The Scherrer equation was
used at FWHM for peak position of Calcium-Aluminum Oxide
nanoparticles. It result the eight peaks ranging from 18.1 to 62.7 in
XRD spectrum. The highest intensity observed at 35.1 with average
crystallite particle size of 25.6 nm (Table 3 and Figure 5).
3.2.3 | EDX peaks spectra of Calcium Aluminum
Oxide nanoparticles
The EDX peaks spectra are used to calculate elements present in the
sample according to their weight and atomic percent. In present
project the calcium aluminum oxide contain aluminum 7.45 wt% and
6.93 atomic percent. In addition to, the calcium was the most abun-
dant element with 54.7 wt% and 34.24 atomic percent followed by
oxygen with weight percent 37.26 and atomic percent 58.42, respec-
tively. Whereas, the Chlorine was present as impurities (Table 4 and
Figure 6).
4 | DISCUSSION
The XRD pattern of Cobalt Oxide nano-catalyst showed various dif-
fraction peaks at 2θ angles, that is, 19.2, 30.3, 36.9, 43.7, 59.2, and
65.4. The nanoparticle average crystalline size has been 30.6 nm cal-
culated by the Scherrer equation having cubical structure from
FWHM. The XRD pattern of Cobalt Oxides derivatives showed differ-
ent structure such as CoOX and R-170 have hexagonal structure, R-
230 with spinel structure (CO3O4) and R-300 have Face-centered
cubic structure, CoO(Lin, Wang, Chiu, Chien, 2003). The American
Society for Testing Minerals (ASTM) analyzed the XRD patterns of the
CoO nanoparticles that showed the cubic structure with 7.2 nm size
range (Hussain, Ali, Bano, Mahmood, 2011). According to peak
width and Scherrer equation, similarly the XRD patterns of cobalt
oxide demonstrated hexagonal structure having average particle size
10 nm (Tang, Wang, Chien, 2008). In the same way, Mahmood,
Hussain, and Malik (2010) also reported the XRD pattern of cobalt
oxide nanoparticles that showed size ranges from 2 to 90 nm having
similar cubic structure by using ASTM XRD files.
TABLE 4 Elemental composition of the EDX spectra of Calcium
Aluminum Oxide nanoparticles
Element Weight percent Atomic percent
O 37 58.42
Al 7.45 6.93
Cl 0.59 0.41
Ca 54.7 34.24
Abbreviation: EDX, dispersive X-ray spectroscopy.
FIGURE 6 EDS peaks spectra of Calcium Aluminum Oxide nanoparticles micrograph with various elemental compositions. EDS, energy
dispersive spectroscopy [Color figure can be viewed at wileyonlinelibrary.com]
GUL ET AL. 1129

7. The present study revealed the morphology of Cobalt Oxide. Its
appearance was aggregative in nature, distributed homogeneously
having sponge like morphology. According to Scherrer equation calcu-
lation for XRD analysis, its particle size ranged from 30.6 nm. In the
same way, the Cobalt Oxide (Co3O4) nanoparticles were prepared that
revealed 25, 76, and 93 nm size with calcination temperature of
300
C, 500
C, and 700
C having microspheres morphology (Sharifi,
Shakur, Mirzaei, Hosseini, 2013). Similar to present project the
porous morphology of cobalt oxide were also reported by (Kandalkar,
Gunjakar, Lokhande, 2008). Whereas, (Mahmood Hussain, 2010)
reported the Cobalt Oxide particles showed the uniform regular
spherical sponge like morphology with the size ranges from 2 to
90 nm. In addition to, the cubic and spherical sponge like shape, uni-
form regular with the size ranges from 2 to 10 nm of the cobalt oxide
particles were also reported by Hussain et al. (2011). Regarding the
EDS spectra of Cobalt Oxide nano-catalyst, present work resulted the
concentration of cobalt was 46.85 wt% and 18.01 atomic percent.
The Oxygen concentration was reported 30.51 wt% and 43.19 atomic
percent, respectively. While the iron and carbon concentration was an
impurity, the same method was used for the synthesis of Cobalt Oxide
nanoparticles by (Farhadi, Safabakhsh, Zaringhadam, 2013). Their
EDX spectra showed Oxygen and Cobalt with atomic percent 33.97
and other element, that is, carbon and iron as an impurities.
In current project, SEM result of Calcium-Aluminum Oxide showed
random morphology with porous and aggregative nature. The XRD
analysis bared particles size ranges from 30 to 40 nm via Scherrer equa-
tion. In present research work, mixture of calcium-aluminum oxide were
used in order to use Calcium Oxide or Aluminum Oxide separately. Sim-
ilarly Safaei-Ghomi, Ghasemzadeh, and Mehrabi (2013) used calcium
oxide nanoparticles and resulted spherical morphology with 30–40 nm
particles size. Whereas, Ho, Ng, and Gan (2012) used Calcium Oxide
nanoparticles having uniform distribution, aggregative and irregularly in
shapes with spongy and porous structures. In addition to, similar to pre-
sent work the Calcium Oxide has been used as a based catalyst with
1 μm to 100 μm size ranges and nonuniform diverse shape by Bazargan,
Kostic, Stamenkovic, Veljkovic, and McKay (2015). Lee, Wong, Tan, and
Yew (2015) reported the Calcium Oxide nano-catalyst that showed
stone-like particles with irregular size.
In present study, the EDX spectra of Calcium-Aluminum Oxide
showed Calcium as the most abundant element with 54.7 wt% and
34.24 atomic percent. Aluminum was reported 7.45 wt% and 6.93
atomic percent, oxygen with 37.26 wt% and 58.42 atomic percent,
respectively. Whereas Ho et al. (2012) reported the calcium oxide
with the abundance of calcium and Oxygen. Similarly Calcium Oxide
based catalyst was used and its elemental composition show the
abundance of Carbon and Oxygen after calcination by Bazargan
et al. (2015).
5 | CONCLUSION
It was concluded that the coprecipitation and Top down Ball Mill
methods were the most significant techniques for synthesis of Cobalt
Oxide and Calcium Aluminum Oxide nano-catalysts whereas, SEM,
XRD, and EDX are the most efficient techniques for the characteriza-
tion of nano-catalysts in particular and other compounds in general.
ORCID
Shujaul Mulk Khan https://orcid.org/0000-0003-1217-6612
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How to cite this article: Gul I, Khan SM, Mehmood T,
Ahmad Z, Badshah H, Shah H. Characterization of Cobalt
Oxide and Calcium-Aluminum Oxide nano-catalyst through
Scanning Electron Microscopy, X-ray diffraction, and Energy
Dispersive X-ray Spectroscopy. Microsc Res Tech. 2020;83:
1124–1131. https://doi.org/10.1002/jemt.23504
GUL ET AL. 1131