This study investigates the synthesis of a Ca–Al hydrocalumite-type layered double hydroxide (LDH) from calcite and MK through acid leaching, alkaline precipitation, and hydrothermal crystallization. The objective was not only to assess the feasibility of this route from minimally processed mineral precursors, but also to identify the conditions governing selective hydrocalumite (HC) formation in a Ca–Al system. The effects of HCl concentration, aging time, aging temperature, pH during aging, crystallization time, and crystallization temperature were systematically examined. X-ray diffraction results showed that phase formation strongly depends on the balance between precursor dissolution, release of calcium and aluminum species, and suppression of silica-related secondary reactions. The most favorable conditions were obtained with 1 M HCl, 30 min aging at 45 °C, pH 11.5, and hydrothermal crystallization at 50 °C for 18 h. Under these conditions, the synthesized product exhibited the most pronounced HC reflections, with limited formation of katoite, anorthite, and residual calcite. FTIR and TG/DTA analyses supported the formation of a hydrated Ca–Al hydrocalumite-type phase containing carbonate species. Compared with a commercial reference, the synthesized material displayed a finer and more homogeneous particle size distribution, a more open @lamellar morphology, and lower specific surface area and porosity, while maintaining strong basicity and buffering capacity in aqueous media. These results demonstrate that HC can be successfully obtained from simple mineral resources, provided that synthesis parameters are carefully controlled, and open the way for more economical and accessible preparation routes for Ca–Al layered materials.
The crystal growth behavior of gamma alumina (γ-Al2O3) nanoparticles (NPs) prepared by the high pressure-induced spark plasma sintering (SPS) method and crystallographic characteristics of the resultant NPs were examined by X-ray diffraction (XRD) and the transmission electron microscopy (TEM) technique. The XRD revealed that γ-Al2O3 in the tetragonal form as a highly crystalline phase was formed and no secondary phases were detected. The crystallinity of the material was 94.26 % and the micro-strain and lattice strain were 0.02 % and 0.029 % respectively. The unit-cell volume of 1484.94 Å3 was obtained and the lattice parameters of a = b = 7.961 Å and c = 23.430 Å were calculated using the WPPF analysis. The crystallite-size analysis showed model dependent variations corresponding to diffraction peak broadening, strain and stress effects. Near spherical to irregular NPs were found according to TEM with a moderate inter-particle agglomeration and a particle-size distribution between 50 and 85 nm where average particle size of 67.22 nm. The well-resolved lattice fringes obtained from HR-TEM with an interplanar spacing of 0.330 nm for the (2 1 3) plane was in agreement with the XRD result, revealing the crystalline structure. The presence of crystalline and less ordered regions and several crystal orientations revealed NPs evidence of crystal nucleation and growth. The SAED pattern also corroborated its polycrystalline nature of the synthesized γ-Al2O3 NPs. The overall XRD and TEM analyses give a detailed insight into the crystallographic structure, the morphology of the particles, the crystal growth behavior and the nanoscale structural ordering of the γ-Al2O3 NPs treated by SPS.
This work investigates the integration of homogeneous and heterogeneous catalysis using copper peroxide nanoparticles (CPNPs) to enhance the efficiency of benzyl alcohol oxidation in an aqueous medium at elevated pH. The aqueous basic catalytic system CuSO4.5H2O / S2O8-2 / KOH (pH = 9) is examined for the catalytic oxidation of benzyl alcohol, and para substituted benzyl alcohol to their respective acids aldehyde at ambient temperature. An in-depth investigation of the system elucidates the dual catalytic functions of copper peroxide nanoparticles, wherein both homogeneous and heterogeneous mechanisms influence reaction kinetics and selectivity. Copper peroxide nanoparticles (CPNPs) are separated and characterised using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometry (EDS), FTIR spectra, and BFT analysis. The results confirmed the formation of copper peroxide nano semi-flake-like particles with an average size of 17 nm. BET analysis revealed a high surface area (49.61 m2/g), while BJH analysis confirmed the mesoporous nature, with a pore radius of 1.92 nm and a total pore volume of 0.1475 cc/g. This significantly enhanced the catalytic surface properties, increasing the number of active sites available on CPNP heterogeneous catalysts for benzaldehyde preparation.
Nanocopper powder, exhibits excellent electrical/thermal conductivity, high catalytic activity and only 1% of the cost of silver, making it highly promising for electronic information, catalysis, biomedicine and new energy. However, its application faces critical challenges: easy oxidation and agglomeration, and immature large-scale preparation for high-end products. This review adopts a “performance requirements – preparation technologies – performance regulation – modification methods – application challenges – future prospects” framework. It outlines key performance indicators (particle size uniformity Coefficient of Variation≤20%, purity ≥99.9%, oxidation resistance ≥200 °C). Preparation methods include solid-phase (e.g., ball milling), liquid-phase (e.g., reduction, hydrothermal), and gas-phase (e.g., PVD, CVD) routes, each with distinct advantages and limitations. Electrochemical characterization (Cyclic Voltammetry, Electrochemical Impedance Spectroscopy, Linear Sweep Voltammetry etc.) reveals the influence of size, morphology, and surface state. Modification strategies such as surface coating, elemental doping and structural optimization (spheroidization, porosification) are examined. Finally, current applications and remaining challenges—oxidation stability, batch consistency, and green synthesis—are analyzed, providing a comprehensive reference for advancing high-end nanocopper powder development.
In this report, composites of porphyrins and TiO2 are developed for the detection of nitrite. The porphyrins employed are free base (TCPP) and Ni(II) (NiTCPP) 5, 10,15,20-tetrakis(4-carboxyphenyl) porphyrin. TCPP and NiTCPP were characterized using ultraviolet-visible light spectrophotometry (UV-Vis) which showed the expected bands and the time-of-flight-secondary ionization mass spectrometry which showed acceptable m/z values. Following this, they were conjugated onto TiO2 nanospheres (TiO2NS). The characterization of the nanoconjugates was done using solid state UV-Vis spectroscopy which showed hybrid bands, X-ray diffractometer, Brunauer-Emmett-Teller analyzer, atomic force microscopy, and transmission electron microscopy. An irreversible diffusion-controlled oxidation was observed upon electrochemical sensing of nitrite. TiO2NS-NiTCPP showed high sensitivity in terms of limit of detection (LoD) compared to previous reports. The obtained limit of detection was 4.60 μM is lower than the known permitted amount of 1 mg/L for nitrite in drinking water.
