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March 2023
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197 Reads
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5 Citations
Crystal Growth & Design
Nanostructure control is an important issue when using electroactive materials in energy conversion and storage devices. In this study, we report various methods of synthesis of nanostructured copper (II) hydroxide nitrate (Cu2(OH)3NO3) with a layered hydroxide salt (LHS) structure using various synthesis methods and investigate the correlation between nanostructure, morphology, and their pseudocapacitive electrochemical behavior.
July 2021
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52 Reads
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8 Citations
Journal of Alloys and Compounds
Layered Double Hydroxides (LDH) and related nanocomposites have attracted much attention for biomedical applications and the development of LDH drug carriers composed by endogenous metals, such as iron, is of obvious interest. However, most of the studies reported so far on iron-containing LDH, mainly focusing on the applications, suffer from insufficient data about the synthesis and the characterization of these materials. In this study, it is addressed compositional and structural properties of two series of LDH materials, Mg2FeyAl(1-y)-Cl and Zn2FeyAl(1-y)-Cl with a M²⁺/M³⁺ molar ratio equal to 2 and 0 ≤ y ≤ 1. By combining crystal-chemical reasoning, Rietveld refinements and pair distribution function analysis (PDF), it was possible to differentiate between contributions from crystalline and amorphous components. Concerning Mg-series, for y > 0.5, the compositions were found to slightly deviate from those expected with an increase in the value of R tending to 3. For Zn-series, more heterogeneous samples were obtained with the presence of amorphous 2-line ferrihydrite clearly demonstrated by PDF analysis. As well as providing a reliable approach to the characterization of Fe-LDH, this study gives useful elements for better understanding and interpreting the results reported in the literature regarding these phases.
June 2020
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145 Reads
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12 Citations
The thermal behavior of a model MK based K‐geopolymer (Si/Al = 1.38 and K/Al = 0.68; obtained by alkaline activation of a very pure metakaolin) was investigated between room temperature and 1400°C in order to evaluate its potentiality for high‐temperature applications. The purpose of our study was to monitor the behavior of a geopolymer during a temperature rise in order to better understand its variations with respect to temperature. The works from the present paper focus only variations in the internal structure of the mineral matrix. The results presented here show that the amorphous mineral matrix is preserved up to 900°C. The results also show that there is a densification of the internal structure of tetrahedral network during heating, due to changes in the Q³ environments in fully‐connected Q⁴ for both silicates and aluminates. Thus, our work provides a new more precise vision of the 3D geopolymeric mineral matrix for which the silicoaluminous network is not exclusively composed of Q⁴ entities, contrary to what is frequently encountered in the literature before.
... Cu catalyst synthesis on SiO2 was studied by Toupance et al. [51][52][53], evaluating the Cu species present. Their method, termed "cation exchange" or "selective adsorption", involved the synthesis of the octhaedral [Cu(NH3)4(H2O)2] 2+ complex and suspending SiO2 in a complex solution maintaining pH above 9 to avoid During synthesis, urea hydrolysis provides the necessary hydroxide ions, derived from the acid-base equilibrium of released ammonia, for Cu(OH) 2 formation [47]. In the presence of nitrate ions, this leads to Cu(II) hydroxide nitrate formation (Cu 2 (OH) 3 NO 3 ), as nitrate ions have a strong tendency to incorporate into the Cu(OH) 2 crystal structure [48]. ...
March 2023
Crystal Growth & Design
... The PDF curves were extracted from total X-ray scattering data and, to facilitate interpretation, and the same analysis was performed on Zn2Al-Cl55 sample and NAC salt. As reported elsewhere [72], the first peak observed on the PDF for LDH materials refers to the hydroxide layers. Thus, in the present case, the first peak around 2.0 Å is due to the closest OH shell around Zn, Al atoms while the peaks observed at about 3.07 Å (a), 5.3 Å (√3a), and 6.2 Å (2a) are attributed to the M−M bond distances The other peaks are due to multiple pairs of atoms. ...
July 2021
Journal of Alloys and Compounds
... Using 2% NK results in an enhancement for the matrix morphology and filling most of the formed pores where it acts as nucleation sites for accumulation [48,49] of the geopolymer constituents leading to the formation of three dimensional network (Fig. 8b). Increasing NK to 3% leads to formation of 6 Bulk density of alkali activated specimens enhanced with mixed ratio of nano materials, a nano-glass and nano-kaolin, b nano-silica fume and nano-kaolin agglomerates from NK and N-glass forming wide voids between the matrix binder and so hinder the formation of the geopolymer network as indicated from the micrograph (Fig. 8C) [51,52]. ...
June 2020
![TGA/DTA analysis of the geopolymer sample with indication (arrows) of the thirteen thermal treatments applied for ex situ characterizations [Color figure can be viewed at wileyonlinelibrary.com]](https://www.researchgate.net/publication/341884889/figure/fig1/AS:11431281255413273@1719419032810/TGA-DTA-analysis-of-the-geopolymer-sample-with-indication-arrows-of-the-thirteen_Q320.jpg)
![Chemical shift variation with temperature for A, ²⁷Al MAS NMR experiments (maximum position for the three T95, T³⁰, and Tbak series) and B, ²⁹Si MAS NMR (δiso for the T³⁰ series) [Color figure can be viewed at wileyonlinelibrary.com]](https://www.researchgate.net/publication/341884889/figure/fig5/AS:11431281255387220@1719419034123/Chemical-shift-variation-with-temperature-for-A-Al-MAS-NMR-experiments-maximum_Q320.jpg)
