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In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO2 adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO2 uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO2 uptake at 25 &deg, C, but had no effect on it at 0 &deg, C.

ZnO nanoparticles doped with transition metal ions are intensively studied nanomaterials, due to their charges and the spins of electrons that provides new magnetic, optical and transport properties. They find a vast range of applications, ranging from optoelectronics to spintronics. In this context especially important is the room temperature ferromagnetism observed for ZnO doped nanomaterials, although this phenomenon is still a controversial and open topic in material science, mostly due to low reproducibility of results from samples prepared by different techniques. In the first part of this article a short review of papers using magnetometric methods to determine the magnetic characteristics of Co-doped ZnO nanomaterials is presented. Different models introduced to explain room temperature ferromagnetism (carrier mediated ferromagnetism, Co2+-oxygen vacancy pairs, blocked superparamagnetic clusters, Co2+-Zn interstitial pairs, heterogeneous distribution of magnetic ions) are examined and discussed. In the second part, magnetisation study of a new series of nCoO/(1-n)ZnO nanocomposites synthesized by hydrothermal method under higher than previously applied pressure will be described. The obtained experimental results will be analysed and information on magnetic systems responsible for the observed characteristics and the involved magnetic interactions will be deduced.

We have studied the magnetic properties of nanocrystals of ZnO :MnO prepared by traditional wet chemistry method. The detailed structural and morphological characterization was performed. The results of systematic measurements of AC magnetic susceptibility as a function of temperature and frequency as well as DC magnetization are reported. We observed two different types of magnetic behavior depending on the concentration doping. For samples with low nominal content (up to 30 wt% of MnO), superparamagnetic behavior was observed. We attribute the observed superparamagnetism to the presence of nanosized ZnMnO 3 phase. For nanocrystals doped above nominal 60 wt% of MnO ferrimagnetism was detected with TC at around 42 K. This magnetic behavior we assign to the presence of nanosized Mn3O4 phase.

Carbon spheres were prepared by carbonisation of phenolic resin spheres obtained using a modified Stober method in a microwave assisted solvothermal reactor. Preparation process involved water–ethanol, ammonia water, resorcinol, potassium oxalate and formaldehyde. The mixture was stirred for 24 h at room temperature and then subjected to a pressure treatment, in which the solution was treated in a microwave assisted solvothermal reactor for 15 min at a pressure of 1–3 MPa. The proposed synthesis resulted in a material containing microporous carbon spheres having high surface area (from 1178 to 1648 m2/g), with diameters from 200 to 350 nm, total pore volume from 0.49 to 0.78 cm3/g, and high CO2 adsorption capacity from 3.86 to 5.03 mmol/g measured at 0.1 MPa and 25 °C. Taking into account the properties of the obtained material, it can be applied as a sorbent for CO2 capture.

The ZnO/ZnMn2O4 nanocomposite (ZnMn) was used as adsorbent for the removal of cationic dye Basic Yellow 28 (BY28) from aqueous solutions. The adsorbent was characterized by X-ray diffraction, scann...

The effect of an alkali treatment (potassium hydroxide) on the properties of a commercial activated carbon has been studied. The aim of the treatment was to improve the adsorption properties of the material toward carbon dioxide. In the result of the treatment, silica contained in the raw carbon was removed and the density of the material increased. The changes in the surface chemistry were observed as well. The treatment of the activated carbon with KOH resulted in a complete removal of carboxy and lactone groups and a decrease of the general content of the acidic groups (more significant than that of basic groups). Simultaneously, the surface concentration of hydroxyl groups increased. The alkali treatment of activated carbon resulted in an increase of carbon dioxide uptake of 14% (measured using a volumetric method at 0℃). The adsorption of carbon dioxide on activated carbon has a mixed (physicochemical) character and that two types of adsorption sites are present at the surface. The adsorption energy varies roughly from 25 to 60 kJ/mol.

In this work, production and characterization of carbon spheres from resorcinol and formaldehyde, using a microwave assisted solvothermal reactor, is presented. The influence of different experimental conditions, e.g., reaction time, pressure, and power, on the structure of the obtained materials, and carbon dioxide adsorption properties, was studied. Using the method described in this work, it is possible to significantly reduce the reaction time, to as low as 10 min, compared with widely described processes carried out in autoclaves, requiring several hours. Simultaneously, it was discovered that the application of higher reactor pressures, over 3 MPa, resulted in the destruction of spherical shape and the formation of graphitic layers. The importance of micropores below 0.4 nm, for adsorption of carbon dioxide, was also shown in this work. Microporous carbon spheres with efficient CO2 adsorption properties (nearly 7 mmol/g at 1 bar and 0 °C) were synthesized using this process.

Nanocrystalline samples of ZnO(Mn) were synthesized by hydrothermal method. The morphology of the samples was studied by HRTEM and SEM. X-ray diffraction was used to determine composition of the samples (ZnO and ZnMn2O4) and the mean crystalline size (from 16 to 99 nm). In this paper we report the experimental spectra of Raman scattering (from 100 to 1600 cm−1) with surface optical phonons (SOP) in range of 497–538 cm−1 as well as formation of new phases MnO, Mn3O4 and ZnMnO3. The phonon of registered phase's exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

The nanopowders of (ZnO)1–x(Al2O3)x, where x ranges from 0 to 0.7, were obtained by two chemical methods: the co-precipitation/calcination and hydrothermal synthesis. The first assessment of structural and optical properties of the obtained nanopowders was undertaken by the SEM, XRD, Raman and far-infrared spectroscopy, which was followed by the photoluminescence spectroscopy at room temperature. The obtained far-infrared reflectivity spectra were analyzed using the fitting procedure. The dielectric function of ZnO–Al2O3 nanopowders was modeled by the Maxwell-Garnet formula under the assumption that the nanopowders are a mixture of homogenous spherical inclusions in air. The combined plasmon-LO phonon modes (CPPM) were observed in the far-infrared reflection spectra. The photoluminescence spectra contain emissions related to the presence of ZnO, ZnAl2O4, and AlOOH phases in the nanomaterial, which is in agreement with the results obtained by other experiments.

Nanocrystaline samples of ZnO(Fe) were synthesized by traditional wet chemical method followed by calcinations. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, ZnFe 2 O 4 and Fe 2 O 3 ) and the mean crystalline size (from 8 to 51 nm). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm −1 ) with surface optical phonons (SOP) in range of 500–550 cm −1 . The phonon of registered phase’s exhibit effects connected to phase concentration, while the SOP phonon mode exhibit significant confinement effect.

Surface optical phonons (SOP) were observed in the range of 496–572 cm−1 on Raman scattering spectra of nanocrystalline samples of ZnO(Co) prepared by use of the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcinations. The phase composition of the samples (ZnO, Co3O4, ZnCo2O4) and the mean crystalline size (14–300 nm) were determined using X-ray diffraction measurements. The SOP phonon mode exhibit significant size confinement effect, while the phonons of registered phases exhibit effects connected to phase concentration.

Nanocrystaline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe 2 O 3 , ZnFe 2 O 4 ) and the mean crystalline size (8–52 nm). In this paper we report the experimental spectra of Raman scattering. Main characteristics of experimental Raman spectrum in 200–1600 cm −1 spectral region are: sharp peak at 436 cm −1 and broad two-phonon structure at ∼1150 cm −1 , typical for ZnO; broad structure below 700 cm −1 that has different position and shape in case of ZnFe 2 O 4 or Fe 2 O 3 nanoparticles. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles. Frequencies of these vibrational modes were analyzed in elastic continuum approximation, which considers nanoparticle as homogeneous elastic sphere.