1,721,011 research outputs found
Sol-Gel synthesis, thermal, spectroscopic and morphological characterization of bioactive titania
No full textTitanium dioxide (TiO2) is frequently used in the industrial and environmental applications for its photocatalytic activity, chemical stability and anticorrosive properties. It has been reported in the literature that titanium biomaterials’ response and properties can be affected by the synthesis technique. In this work, the sol-gel method was used to synthesize the TiO2 particles [1,2]. Regarding the chemical characterization, Fourier transform infrared (FTIR) spectroscopy and thermogravimetry (TG) were used to evaluate the chemical structure of the particles, while SEM and BET measurements were used to determine the morphology and nanoparticles size of the prepared TiO2 particles. In particular, the aim of this study was to evaluate the use of these materials in the prevention of the infection after the implantation. The antibacterial activity of TiO2 particles was assessed using Escherichia coli. Finally, in order to evaluate the biological properties, the TiO2 particles were soaked in simulated body fluid (SBF) for 21 days to observe their bioactivity.
[1] Catauro M, Tranquillo E, Dal Poggetto G, Pasquali M, Dell'Era A, Ciprioti Vecchio S. Influence of the heat treatment on the particles size and on the crystalline phase of TiO2 synthesized by the sol-gel method. Materials 11, (2018), 2364.
[2] Michelina Catauro, Giovanni Dal Poggetto, Roberta Risoluti, Stefano Vecchio Ciprioti, Thermal, antimicrobial characterization of bioactive titania by Sol-Gel synthesis. J. Therm. Anal. Calorim.
Vapor pressures and standard molar enthalpies, entropies and Gibbs energies of sublimation of two hexachloro herbicides using a TG unit
No full textThe vapor pressures above the solid hexachlorobenzene (HCB) and above both the solid and liquid 1,2,3,4,5,6-hexachlorocyclohexane (lindane) were determined in the ranges 332-450 K and 347-429 K, respectively, by measuring the mass loss rates recorded by thermogravimetry under both isothermal and nonisothermal conditions. The results obtained were compared with those taken from literature. From the temperature dependence of vapor pressure derived by the experimental thermogravimetry data the molar enthalpies of sublimation Delta(g)(cr)H(m)degrees() were selected for HCB and lindane as well as the molar enthalpy of vaporization Delta(g)(1)H(m)degrees() for lindane only, at the middle of the respective temperature intervals. The melting temperatures and the molar enthalpies of fusion Delta(1)(cr)H(m)degrees(T(fus)) of lindane were measured by differential scanning calorimetry. Finally, the standard molar enthalpies of sublimation Delta(g)(cr)H(m)degrees D(298.15 K) were obtained for both chlorinated compounds at the reference temperature of 298.15 K using the Delta(g)(cr)H(m)degrees(), Delta(g)(1)H(m)degrees() and Delta(1)(cr)H(m)degrees(T(fus)) values, as well as the heat capacity differences between gas and liquid and the heat capacity differences between gas and solid, Delta(g)(1)C(p,m)degrees and Delta(g)(cr)C(p,m)degrees, respectively, both estimated by applying a group additivity procedure. Therefore, the averages of the standard (p degrees = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation at 298.15 K, have been derived: [GRAPHICS] (C) 2009 Elsevier B.V. All rights reserved
Bioactive Titania-Based Organic–Inorganic Hybrids Synthesized via Sol–Gel
No full textIn the present work, the synthesis of organic–inorganic hybrid (OIH)
materials for biomedical applications is described. Two types of OIH systems
are prepared by means of a sol–gel process, both consisting of a titania
matrix. The use of two different biocompatible thermoplastic polymers as
organic component is evaluated: the poly(-caprolactone) and the
poly(ether-imide). The formation of the hybrid structure is ascertained by
scanning electron microscopy, whereas the identification of the interactions
between the organic and the inorganic phases is obtained by using Fourier
transform infrared spectroscopy. Moreover, a preliminary evaluation of the
osseointegration ability of the obtained material is investigated by soaking the
synthesized OIHs in a simulated body fluid to follow the ability of the
materials to induce the hydroxyapatite nucleation. The results show that all
OIHs are bioactive and, thus, potentially suitable for the implants’ design
Thermal characterization of micro encapsulated polyphenols extracted from olive leaves
Full text linkUnderstanding the relationship between thermal analysis and geopolymer composition containing waste glass
No full textThe use of waste glass in geopolymer matrices represents a very important resource for recycling of inorganic materials [1]. The aim of this study is the investigation of the thermal and mechanical modification of the metakaolin-based geopolymer network due to the presence of a different amount of waste glass.
The paste was prepared by mixing two homogenous powders, metakaolin and waste glass. No phase separation was observed since high viscosity was assured by a correct geopolymer formulation. The paste was poured into plastic molds and the setting phase carried out at 50 °C for 1 day, while the hardening phase was carried out at room temperature for 7, 14 and 28 days [2].
The chemical structure of the synthetized materials was investigated by Fourier Transform Infrared (FT-IR) spectroscopy, which showed the formation of bonds between the two components.
We adopted FT-IR spectroscopy to highlight the reticulation degree of the final amorphous solid product, as accurately reported in a previous study [3]. The bands at 3462 and 1640 cm−1 were attributed to the -OH stretching and bending vibrations of water's hydration, respectively [4]. The band at 1640 cm−1 was preserved in waste glass containing geopolymers. Furthermore, in all the spectra the typical signals of the silica matrix are found. The asymmetrical Si-O-Si stretching vibrations were detectable in the spectral region 1080–1050 cm−1. Aluminosilicate’s typical signals, assigned to internal vibrations of Si-O-Si and Si-O-Al bonds, are found in the spectra of waste glass based geopolymers, whereas the frequency of the absorption bands seems to be approximately related to the Si/Al ratio in the aluminosilicate framework. In the present case of waste glass powder addition to MK-based geopolymer the peak at 1080 cm−1 shift to lower wavenumber (1008 cm−1), accompanied by an increased contribution of the Si-O-Al bond (950–960 cm−1), indicating the formation of a more efficient 3D geopolymer network. The spectrum of metakaolin also revealed sharp peaks ascribed to the stretching of hydroxyl groups and to Al(VI)-OH bonds in the kaolinite residues [4], whereas the Al(IV) absorption band at around 800 cm−1, characteristic of metakaolin, seems to be not found in the spectra of the corresponding geopolymers. Indeed, a band at around 690 cm−1, whose intensity decreases with the increase of waste glass content, is evident in geopolymers' spectra.
The thermal behavior of the geopolymer samples was studied using a simultaneous Thermogravimetry/Differential Thermal Analysis (TG/DTA). The TG/DTA experiments were carried out from ambient temperature to 1500 K at a heating rate of 10 K/min under both argon and air atmosphere at 50 ml/min. The thermal characterization of the three mixtures (GPMK1, GPMK2 and GPMK3, respectively with 30, 40 and 50wt% of waste glass) revealed that the oxidizing atmosphere does not affect the thermal behavior of all the samples tested. The TG and DTA curves of GPMK and of the three waste glass-containing formulations under flowing Ar are reported in Fig. 1. Furthermore, they retained about 20 wt% of water, with lower amount for glass-rich geopolymers (GPMK2 and GPMK3 with 40 and 50 wt% of glass, respectively). Lower amounts of water were removed by dehydroxylation (in the range 573–973 K) in GPMK2 and GPMK3, since they have the lower content of geopolymer and, consequently, a lower number of hydroxyl groups to undergo condensation.
The mechanical stability of the 3D geopolymeric network has been measured in terms of the compressive strength. After 28 days at room temperature, the samples synthesized using different percentages of waste glass showed a good geopolymerization, reaching the highest mechanical performance at 40 wt% of glass incorporated into MK.
Preliminary biological data highlighted that cytotoxic and antimicrobial effects are significantly affected by the content of waste glass in the geopolymer matrix, due to the fact that the higher is the waste glass content the higher is the production of reactive oxygen species (ROS), responsible of both cytotoxic and antimicrobial effects.
Figure 1. TG (up) and DTA (down) curves of GMPK and of the three mixtures at 10 K/min under Ar flowing atmosphere.
Bibliography
[1] M.R. El-Naggar and M.I. El-Dessouky, Constr. Build. Mater,132 (2017) 543-555
[2] M.A. Pereira, D.C.L. Vasconcelos and W.L. Vasconcelos, Mater. Res., 22 (2019) 2
[3] S. Luhar, T.-W. Cheng, D. Nicolaides, I. Luhar, D. Panias, K. Sakkas, Constr. Build. Mater, 222 (2019) 673-687
[4] M. Catauro, A. Dell’Era, S. Vecchio Ciprioti, Thermochim. Acta, 625 (2016) 20–2
Biosensors for monitoring the isothermal breakdown kinetics of peanut oil heated at 180°C. Comparison with results obtained for extra virgin olive oil
No full textThe present research was devoted to studying the kinetics of the artificial rancidification of peanut oil (PO) when a sample of this oil was isothermally heated at 180 °C in an air stream. The formation of radical species due to heating was evaluated using a radical index whose value was determined using a biosensor method based on a superoxide dismutase (SOD), while the increasing toxicity was monitored using a suitable toxicity measuring probe based on the Clark electrode and immobilized yeast cells. An extra virgin olive oil was isothermally rancidified under the same experimental conditions and the corresponding data were used for the purpose of comparison. Both the so-called "model-fitting" and the classical kinetic methods were applied to the isothermal process biosensor data in order to obtain the kinetic constant rate value at 180 °C. © 2012 Elsevier Ltd. All rights reserved
Thermal analysis and health safety: Thermoanalytical characterization of hardwood softwood dust
No full textHardwood dust is a human carcinogen; upon inhalation, it can cause sinonasal adenocarcinoma. Softwood, on the other hand, is only suspected of carcinogenic properties. However, the toxicology-based recommended exposure limits for hardwood and softwood dust in working environments have been derived identically. While it is very simple to distinguish the wood by morphological evaluations, the wood dust produced in working activities does not allow differentiation. Thermal analysis, especially thermogravimetry, was applied to evaluate the different characteristic thermal profile of standard hardwood and softwood dusts. The different TG and DTG traces allow to propose thermogravimetry as a new tool to distinguish and quantify the different dust origin. © 2012 Akadémiai Kiadó, Budapest, Hungary
A multi-technique approach to characterize bioactive silicate composites
No full textIn the present work the ternary SiO2·CaO·P2O5composite, which differ in the Ca/P molar ratio, were synthesized by means of a sol-gel route. In order to investigate the influence of the relative amount of each phase the thermal properties of the synthesized gel-glass materials were studied as a function of the Ca/P molar ratio using thermogravimetric and differential thermal analysis (TG/DTA). After dehydration (in a single step), described from a kinetic point of view as a simple water evaporation without rupture of chemical bonds, all gels undergo a complex multi-step decomposition with endo and exothermic effects, followed by crystallization of calcium silicate phases at about 950°C. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy, coupled with energy dispersive spectroscopy (SEM/EDS), allowed us to detect the chemical modifications induced by modifying the Ca/P molar ratio and the sintering. This process is obtained by thermal treatment of the materials after analyzing their thermal behavior in the temperature range 600-1000°C, with the aim of making them suitable for their applications. The results revealed that when temperature is up to 900°C, crystallization occurs and pseudowollastonite and wollastonite were formed. Finally, the amount of pseudowollastonite decreased with increasing the sintering temperature, while that of wollastonite increased
Thermal and biological properties of several composite materials prepared by sol-gel method.
Full text linkSpectroscopic, Thermal Analysis and Bioactivity Study of New Ferrous Citrate Based Materials Prepared by Sol–Gel Method
No full textThe aim of this work is the development of a system able to release ferrous
ions in a controlled manner. An interesting alternative to a systemic therapy
can be the use of controlled drug release for medical applications. Starting
from iron powder and citric acid, ferrous citrate (Fe(II)C) is synthesized by a
redox reaction between these two. The confirmation that only Fe(II)C is
obtained by redox reaction is shown from Fourier transform infrared
spectroscopy (FTIR), 1,10-phenanthroline and sodium thiocyanate
colorimetric experiments. Fe(II)C is embedded within a SiO2 matrix in
different weight percentage by means of a sol–gel route. The presence of
Fe(II)C in the silica matrix is confirmed by FTIR spectroscopy and
thermogravimetry assays. Furthermore, these two techniques are used to
investigate the thermal behavior of the above-mentioned sol–gel materials.
The bioactivity test carried out by soaking the synthesized complex delivery
systems in a simulated body fluid shows that the biological properties of the
silica matrix are not modified by the presence of Fe(II)C
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