Layers of cerium dioxide nanoparticles were prepared on titanium by electrodeposition with organic solution. Three concentrations of cerium ions were used at 31.6 V. The organic solution was isobutanol and titanium foils were used as anodes and cathodes. Currents were monitored during the electrodeposition. Deposition times ranged from 0.5 to 8 h. Deposited Deposited layers were calcined at 700 K for 30 min. The morphology and composition of the deposited layers were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). As-prepared and calcined deposition layers were assayed to be cerium dioxide. The average crystallite size increased from 4 to 7 nm through calcination at 700 K. Sizes of calcined cerium oxide agglomerates were ranging from 73 to 146 nm for 30 min deposition and 209 to 262 nm for 8 h deposition. The electrodeposition efficiencies of 0.5 h deposition at three concentrations were measured to be highest.
Targets of cerium dioxide with thicknesses in range of several mg/cm2 were used in proton-induced nuclear reactions [
Thin layers of cerium dioxide (CeO2) have been prepared by various methods such as electrodeposition [
In this work nanocrystalline CeO2 layers of various thicknesses were prepared on titanium by electrodeposition in isobutanol of three concentrations of Ce3+ ions at 31.6 V, similarly to nanocrystalline lanthanum oxide and lanthanum oxycarbonate layers prepared at much higher voltages ranging from 200 to 1000 V [
Cerium nitrate hexahydrate (Ce(NO3)3·6H2O, ≥99.0%, Fluka) powder was dissolved in a minimal amount of distilled water and further in isobutanol. The aqueous-organic mixture was evaporated by heating above 94°C to its nearly dried state, whose composition was examined by X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha+ spectrometer) with an Al K
The electrodeposition was carried out at room temperature in a cell which was made of Teflon and used in the previous study [
Chart for syntheses of as-prepared and calcined CeO2 layers.
Morphology and surface compositions of electrodeposition layers were examined by scanning electron microscopy (SEM, Hitachi S-4300) and X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha). Their corresponding compositions and structural data with average crystalline sizes were determined from measurements by X-ray diffraction (XRD, PANalytical X’pert PRO MPD) with wavelength of Cu K
XPS spectrum of the cerium nitrate precursor with isobutanol dried on a Ti foil is shown in Figure
Elemental composition (atomic %) obtained from XPS spectra for cerium nitrate precursor and electrodeposition layers.
Major |
Cerium nitrate precursor | Layers | |
---|---|---|---|
As-prepared | Calcined at 700 K for 30 min | ||
Ce | 4.6 | 13.0 | 16.9 |
O | 61.9 | 52.6 | 58.8 |
C | 20.3 | 32.3 | 24.3 |
N | 13.2 | 2.1 |
XPS spectra of (a) cerium nitrate precursor dried on Ti and layers on Ti electrodeposited at 31.6 V (b) as prepared and (c) calcined at 700 K for 30 min.
The Ce 3d5/2 and 3d3/2 peaks with their corresponding satellite peaks in Figure
XPS spectra of Ce 3d peaks with their satellite lines denoted as S for (a) cerium nitrate precursor and the layers (b) as prepared and (c) calcined at 700 K for 30 min in Figure
A wide-angle X-ray diffraction (XRD) pattern of the cerium nitrate precursor with isobutanol dried on a Ti foil is shown in Figure
Estimated crystallite size (Scherrer size), lattice parameter
CeO2 sample |
|
Scherrer size (nm) |
|
|
Strain | SF | TC |
---|---|---|---|---|---|---|---|
As-prepared | 111 | 3.630 | 5.441 | 0.07587 | 0.00955 | 0.01983 | 1.1899 |
200 | 4.146 | 5.439 | 0.05817 | 0.00836 | 0.01628 | 0.8344 | |
220 | 4.049 | 5.451 | 0.06098 | 0.00856 | 0.01432 | 1.1136 | |
311 | 3.175 | 5.424 | 0.09918 | 0.01092 | 0.01714 | 0.8622 | |
Calcined at 700 K for 30 min | 111 | 6.991 | 5.428 | 0.02046 | 0.00496 | 0.01029 | 1.1364 |
200 | 8.494 | 5.426 | 0.01386 | 0.00408 | 0.00792 | 0.9499 | |
220 | 6.572 | 5.420 | 0.02315 | 0.00527 | 0.00880 | 1.0453 | |
311 | 6.612 | 5.420 | 0.02287 | 0.00524 | 0.00823 | 0.8685 |
X-ray diffraction patterns of (a) cerium nitrate precursor dried on Ti and electrodeposition layers on Ti (b) as prepared and (c) calcined at 700 K for 30 min.
The average crystallite sizes of the as-prepared CeO2 layer in Table
SEM micrographs of CeO2 layers obtained by 0.5 or 8 h electrodeposition with 0.046, 0.092, and 2.0 mg/mL of Ce3+ ions and subsequent 30 min calcination at 700 K are shown in Figure
SEM micrographs of CeO2 layers calcined at 700 K for 30 min after (a) 30 min electrodeposition of 0.046 mg/mL of Ce3+ on Ti, (b) 8 h electrodeposition of 0.046 mg/mL of Ce3+, (c) 30 min electrodeposition of 0.092 mg/mL of Ce3+, (d) 8 h electrodeposition of 0.092 mg/mL of Ce3+, (e) 30 min electrodeposition of 2.0 mg/mL of Ce3+, and (f) 8 h electrodeposition of 2.0 mg/mL of Ce3+.
Currents of 0.5, 2, 4, 6, and 8 h electrodepositions at 31.6 V with 0.046, 0.092, and 2.0 mg/mL of Ce3+ ions are shown in Figures
Currents of 0.5 h electrodepositions with three concentrations of Ce3+ ions at 31.6 V.
Currents of 2 h electrodepositions with three concentrations of Ce3+ ions at 31.6 V.
Currents of 4 h electrodepositions with three concentrations of Ce3+ ions at 31.6 V.
Currents of 6 h electrodepositions with three concentrations of Ce3+ ions at 31.6 V.
Currents of 8 h electrodepositions with three concentrations of Ce3+ ions at 31.6 V.
Thicknesses and yields of 0.5, 2, 4, 6, and 8 h electrodepositions at 31.6 V with 0.046, 0.092, and 2.0 mg/mL of Ce3+ ions are shown in Figures
Thicknesses and yields of electrodepositions for three concentrations of Ce3+ ions.
Deposition time (h) | Concentration of Ce3+ ions (mg/mL) | |||||
---|---|---|---|---|---|---|
0.046 | 0.092 | 2.0 | ||||
Thickness (mg/cm2) | Yield (%) | Thickness (mg/cm2) | Yield (%) | Thickness (mg/cm2) | Yield (%) | |
0.5 | 0.015 ± 0.014 | 24 ± 22 | 0.021 ± 0.015 | 17 ± 12 | 0.16 ± 0.02 | 5.7 ± 0.9 |
2 | 0.057 ± 0.010 | 91 ± 16 | 0.050 ± 0.014 | 40 ± 11 | 0.40 ± 0.04 | 15 ± 1 |
4 | 0.067 ± 0.015 | 106 ± 25 | 0.090 ± 0.019 | 72 ± 15 | 0.43 ± 0.03 | 16 ± 1 |
6 | 0.054 ± 0.022 | 86 ± 35 | 0.099 ± 0.018 | 78 ± 15 | 0.42 ± 0.03 | 15 ± 1 |
8 | 0.067 ± 0.062 | 106 ± 40 | 0.150 ± 0.036 | 120 ± 29 | 0.35 ± 0.03 | 13 ± 1 |
Yields of electrodepositions with 0.046 mg/mL of Ce3+ ions at 31.6 V.
Yields of electrodepositions with 0.092 mg/mL of Ce3+ ions at 31.6 V.
Yields of electrodepositions with 2.0 mg/mL of Ce3+ ions at 31.6 V.
Similar results for XPS and XRD of as-prepared samples were observed irrespective of currents and deposition times. Typical particle sizes of as-prepared and calcined cerium dioxide samples shown in the corresponding SEM data were 4 and 7 nm, respectively, regardless of their concentrations, indicating that nucleation was driven mainly by the applied potential. However, the deposition time affected the size of calcined agglomerates, showing that longer deposition times increase the corresponding sizes.
Layers of CeO2 nanoparticles with thicknesses ranging from 0.021 to 0.43 mg/cm2 were prepared on titanium by electrodeposition with isobutanol solution and subsequent calcination. As-prepared and calcined deposited layers turned out to be cubic CeO2. The average crystallite size increased from 4 to 7 nm through calcination at 700 K for 30 min irrespective of the concentration and the current. Structural parameters such as lattice parameter, dislocation density, strain, and stacking factors were reduced by the calcination. The deposition time affected the size of calcined agglomerates as longer deposition times increased the corresponding sizes.
The electrodeposition efficiency was highest at 0.5 h deposition at all three concentrations. The 0.5 h electrodeposition at the highest concentration is suitable for preparation of thicker layers of cerium dioxide, which are to be used in the investigation of cross sections of 142Pr produced in the proton-induced reaction with cerium.
The authors declare that they have no conflicts of interest.
This work was financially supported by AMIE Fund.