română DOREL RADU, OVIDIU DUMITRESCU
Abstract
The type, proportion and chemical-structural characteristics of compounds that are formed as a result of chemical reactions between oxides are determined by the chemical-structural characteristics of the starting oxides and the processing conditions (genesis route).
In present paper, we investigate the influence of basicity on the values of some thermodynamic functions. The considered thermodynamic functions correspond to the forming reactions of the oxide compounds in the alkali-silicate systems.
It was shown that there was no strong correlation between the considered thermodynamic functions (standard enthalpy of formation, deltaH0298, standard Gibbs free energy of formation, deltaG0298) and the percentage of basicity, pB (%).
However, a strong correlation was determined between the ‘”specific” thermodynamic properties and pB%. The specific thermodynamic properties were calculated by dividing the values of the standard (classic) functions to the number of moles of oxide in the compound which resulted from the reaction.
Keywords
Standard Gibbs free energy, Standard enthalpy, Basicity, Alkali-silicate systems
The influence of biomass use on CO2 emissions resulted from burning solid fuels in the energy sector
MONA BARBU, MIHAI BRATU, OVIDIU DUMITRESCU
Abstract
The issue of environmental protection focuses on preventing and reducing pollution phenomena caused by those human activities inducing negative effects such as global warming and the greenhouse effect. The energy sector has the greatest contribution to these phenomena in terms of greenhouse gases emissions.
The paper proposes an application in the energy sector for assessing CO2 emissions resulted from burning classic solid fuels and alternative and biomass fuels at a Combined Heat and Power (CHP) using two methods, either by calculations based upon data obtained from analytical laboratory investigations or by direct measurement at the source.
The investigations were carried out to highlight the influence of the addition of biomass (sawdust) to conventional solid fuel (lignite) for reducing CO2 emissions, recovering unburned carbon content present in the slag, improving the lignite energy properties, in order to use the biomass and slag waste and reduce the CO2 emissions.
Keywords
energy sector, coal, biomass, waste, carbon, CO2 emissions
MIRELA LAZĂR, DANIELA FIAT, GHEORGHE HUBCĂ
Abstract
In the recent years, the film-forming products obtained by adding a nanometric photocatalytic titanium dioxide pigment into their composition have drew the attention of both researchers and manufacturers.
The purpose of this paper is the development of new compositions based on organic binders in aqueous dispersion with different contents of nanometric photocatalytic titanium dioxide pigment and novelty lies in the study of their influence on the film-forming products properties. The study performed on these products revealed self-cleaning effect of the films after exposure to UV radiation and natural aging in urban-industrial environment and the improvement of certain properties, such as: coating power, adherence to support, water and watery-vapours permeability.
Keywords
titanium dioxide, self-cleaning, photocatalysis, film-forming product, aqueous dispersion.
MUSTAFA BASIM MOHAMMED AL TAMEEMI, DRAGOŞ GUDOVAN, RALUCA STAN, DAN MIHĂIESCU, CRISTINA OTT
Abstract
In this work it have been investigated the difference of the encapsulation efficiency and the release behavior of silica nanotubes and MCM-41 by using Ibuprofen as drug model. The highest encapsulation efficiency was in MCM-41, while the highest loaded Ibuprofen amount was in silica nanotubes. According to their larger size folded, silica nanotubes release percentage was around 80% which is higher than MCM-41 which was around 26%. It is worth mentioning that TEOS was used as silica precursor, and CTAB as a surfactant for the synthesis of both the nanostructured materials alike.
Keywords
MCM-41, silica nanotubes, Ibuprofen, Encapsulation efficiency, C-Silica, A-Sol-gel
-
Year
2015
-
Issue
45 (2)
-
Pages
188-193
RĂZVAN STATE, FLORICA PAPA, CORNEL MUNTEANU, IOAN BALINT, ALBERTO ION, ADRIAN VOLCEANOV
Abstract
Gold nanoparticles between 2 and 5 nanometers were synthesized using an easy obtaining method with good reproducibility using PVP as protective polymer and NaBH4 as reducing agent. The Au nanoparticles were characterized by TEM, XPS, XRD and UV-Vis. They are spherical with a very good dispersion making them suitable for a vast number of applications including catalytic and photocatalytic tests for nitrate and nitrite removal from water.
Keywords
gold nanoparticles, synthesis, characterization
UMUT YERLESEN, MÜNIR TASDEMIR
Abstract
The effect of zinc oxide (ZnO) and zinc borate (ZnHBO3) on the mechanical properties of high density polyethylene (HDPE) was investigated. Composites of HDPE with zinc oxide and zinc borate were prepared by melt mixing in a twin screw extruder and then the composites were molded by compression molding method. Filler contents in the HDPE were 5, 10 and 15 wt%.
The dispersion of zinc oxide and zinc borate particles in the matrix polymers was investigated using SEM. It was observed that the dispersion of ZnO and ZnHBO3 particles were relatively good with low ZnO and ZnHBO3 content but the aggregates of ZnO and ZnHBO3 particles in a polymer matrix increased with increasing content. The mechanical test showed that the elasticity modulus, hardness and density of HDPE composites increased with increasing ZnO and ZnHBO3 content. The addition of fillers to the HDPE changed the wear rate of the composites as well.
Keywords
High density polyethylene, zinc oxide, zinc borate, mechanical properties, wear