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In a large number of synthesis methods that have been used to obtain cobalt ferrite nanoparticles, co-precipitation is an economical and straightforward way to get superparamagnetic nanoparticles.
The average particle size can be computed from the TEM image as follows [13] (2) Where d is average diameter, di is the diameter of the ith particle, and N is the number of particles taken into account.
At all the samples, the XRD patterns (Figure 1) of the synthesized nanoparticles show the characteristic peaks (220), (311), (400), (511) and (440), which are matched to the cubic spinel structure (JCPDS card no. 22-1086).
As the temperature is increased, the strength of the absorption band at 590 cm-1 becomes stronger, correlating with a more divalent cation number in B octahedral sublattice.
Acknowledgments This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 104.06-2017.42 References [1] Z.

The quality of conformity between the observed and calculated data can be measured by a number of conventional factors, generally called as ‘R-factors’ (Rexp, Rwp etc.) which have been defined by the following equations [3], (2) (3) and (4) where Iio and Iic stand for the observed and calculated intensities in the ith step, wi represents the weighted factor, (n-p) be the number of degrees of freedom.
The unit cell distortion parameter (ξu) and the degree of cell distortion (R) for a hexagonal wurtzite nanostructures have also been evaluated using the following relations [18]: (6) and (7) Values of a0 and c0 have been taken from JCPDS database (card no. 05-0664) for this calculations.
The mean speed of sound can be written in the form [24,26], (17) Using the um value from Table 4, Debye temperature (θD) can be estimated by using the following relation [24,26], (18) Here, n is the number of atoms in the hexagonal unit cell, NA is the Avogadro number, kB is the Boltzmann constant, and M is the molecular weight of ZnO.

Finally the product was filtered and washed with water numbers of times.
Fig. 1: EPR spectra of Ceria NPs at different temperatures XRD Analysis The XRD pattern of the Ceria NPs calcined at the temperatures of 700˚C and 850˚C was carried out by diffraction within the range of 2θ between 10° to 90°by indexing though the JCPDS card no.81-0792 as shown in Fig.2 .The sample exhibits 9 peaks corresponding to the Ceria crystalline planes with Miller indices of (111), (200), (220), (311), (222), (400), (331), (420),(422) for a series of characteristic peaks at 28.4°, 33.2°, 47.4°, 56.4°, 59.0°, 69.3°, 76.6°, 79.0°, 88.3°, respectively.
The value of lattice constant is sample Ceria NPs is 5.392 Å at a temperature of 700˚C and 5.357 Å at a temperature of 850˚C, it's decreased with increasing the calcinations temperatures., The mean reaction time increases due to increase of temperature, the number of O2-anions decreases from eight to seven and introduces Ce3+ions into the crystal lattice by creating oxygen vacancies.
Peak I is displaced to high wave number peak II when particle size increased.

Phase identification of the samples done with standard JCPDS cards.
The PCM is said to be reliable, if it remains chemically, physically and thermally stable after a certain number of repeated thermal cycles of operation.
To assess the impact of a large number of working thermal cycles on the phase change temperature and the latent heat of fusion of the prepared bio-composite material, the two PCM samples of 2 g each were taken.
From the capsules that were heated and cooled, around 1 g of material was taken for DSC analysis following the number of melt/freeze test cycles stated in order to measure the melting temperatures and estimate the latent heat of fusion of the PCMs.

It can be seen from the XRD graph that the F-Ta2O5 sample has only two absorption peaks that located at 2θ=23.8° and 2θ=47.1°, respectively corresponding to (001) of the quadrature phase Ta2O5 (JCPDS card No. 25-0922) crystal plane and (002) crystal plane.
Batching Table of ZIF-67@graded F-Ta2O5 Nanostructures number Z-0 Z-10 Z-20 Z-50 Z-100 Z-200 Z-500 Amount of F-Ta2O5(mg) 0 10 20 50 100 200 500 Amount of ZIF-67 (mg) 6 6 6 6 6 6 6 Fig. 4.
Phase of ZIF-67@graded F-Ta2O5 Treated with Nitrogen number N-10 N-20 N-50 N-200 N-500 Phase composition Mixture of CoTa2O6 and Co4Ta2O9 CoTa2O6 Mixture of CoTa2O6 and Ta2O5 Mixture of Ta2O5 and CoTa2O6 Ta2O5 It can be seen from Table 3 that when the content of graded F-Ta2O5 is 20mg, the composition of the sample is relatively pure CoTa2O6; With the increase in the amount of Ta2O5 added, the relative content of CoTa2O6 in the sample treated at 900°C in a nitrogen environment gradually decreases.
After 3 cycles, although the hydrogen production efficiency decreased, the hydrogen production efficiency was still higher than the original 90%, indicating that the N-50 sample showed good stability and its service life (number of cycles) was relatively high.

The FT-IR spectrum of these materials was done by “Interspec 2020 FTIR spectrometer” spectro lab UK, over the wave number of 4000–400 cm-1.
The XRD patterns elucidate that pure Ag2SO4 has an orthorhombic crystal structure in consistent with the standard data (JCPDS card no. 07-0203).
FT-IR spectra of the various samples in the wave number range 4000-400 cm-1 are shown in Fig. 2.
This type of interaction between these components provides a large number of surfaces and interfaces which strongly modify the macroscopic properties of the composite solid electrolyte.
The temperature dependence of conductivity of the composite samples is given by the Arrhenius expression, (1) (2) where n is the number of ions per unit volume, e the ionic charge, the distance between two jump positions, n the jump frequency, c the intersite geometric constant, K the Boltzmann constant, and , and are the activation free energy, entropy, and enthalpy terms.

The pattern in Fig. 2(b) of the film deposited from the urea containing solution was identified with the turbostratic a-Ni(OH)2 phase (JCPDS 22-0444 card).
That is, during the first cycle the voltammograms showed small current values which continuously evolve with the increasing number of cycles up to about 80 cycles.
Furthermore, the shift of the redox potential of the Ni(OH)2/NiOOH couple to higher values with increasing cycles number, implies the a®b transformation of Ni(OH)2 in the bleached state and correspondingly the b-NiOOH®g-NiOOH transformation in the colored film.
The number of cycles is indicated for the bleached state.

The patterns match well with the characteristic reflections of Ni-Zn ferrites reported in the JCPDS file card No. 08-0234.
Ionic radius [Å] No. of 3d Electrons Spin-only Magnetic Moment In µB Cu 2+ 6(octahedral) 0.87 9 1 Ni 2+ 6(octahedral) 0.83 8 2 Zn 2+ 4(tetrahedral) 0.74 10 0 Fe 3+ 4(tetrahedral) 6(octahedral) 0.63 0.69 5 5 Table 2: Co-ordination number, Ionic radius, Number of 3d electrons and resulting spin moment of Cu 2+, Ni2+, Zn 2+, Fe 3+ [Collected from various sources].
But in the series of 42x2.0)x8.0( OFeCuZnNi − , Zn 2+ ions having a strong preference for A-sites replace a proportionate number of the magnetic Fe 3+ ions, which are forced to occupy B-sites.

Nanoceria could be prepared through a number of techniques including precipitation, sol-gel and solvothermal methods.
Zeta potentials depend on a number of factors such as velocity of the moving particle under the influence of electric field as well as the viscosity of the dispersion media.
The pattern produced is of good quality and free from any foreign atom or molecule and was compared with the indexed pattern reported from the standard crystallographic database (JCPDS cards no. 89-8436).
This study could possibly be applied in nanoparticles surface modifications and functionalisations in a number of applications particularly catalysis, biomedical and pharmaceuticals.

Introduction On account of the close correlation between the physical and chemical properties and the shape, size, and structure of materials, designing and preparing novel nano-microstructure materials has been intensely pursued not only for fundamental scientific interest but also for their various applications in fields such as biological labeling and imaging, catalysis, drug delivery, sensing, and surface-enhanced Raman scattering.[1] Bi2WO6 is a typical Aurivillius oxide, which is composed of accumulated layers of corner- sharing WO6 octahedral sheets and bismuth oxide sheets. [2] Bi2WO6 is one of the simplest members(when n=1) of the Aurivillius oxide family of layered perovskites with the general formula Bi2An-1BnO3n+3 (A =Ca, Sr, Ba, Pb, Na, K; B = Ti, Nb, Ta, Mo, W, Fe; and n = number of perovskite-like layers), which are structurally composed of alternating perovskite-like and fluorite-like blocks[1].
As shown in Fig. 1, the product can be indexed to orthorhombic Bi2WO6 phase with lattice parameters of a=0.5437nm, b=1.643nm and c=0.5458nm and a space group of Pca21 (JCPDS Card No. 79-2381).
However, bismuth citrate is a wirelike structure that it is easier to shape into nanoplates, resulting in the increased number of nanoplates in Fig.3d compared to Fig.3b and Fig.3c.
Orthorhombic Bi2WO6, which formed nanoparticles later in the hydrothermal process, is a number of alternating (Bi2O2)n2+ layers and perovskite-like (WO4)n2- layers, stacking along the c axis (step 2 in Scheme 1).