In this paper, magnesium hydroxide has been obtained from seawater by a well-known industrial process which involves the chemical reaction between magnesium ions of seawater with dolomite lime to ...produce the magnesium hydroxide precipitate. Furthermore, the precipitate was modified by ultrasound of high intensity. The purpose was to obtain magnesium hydroxide with high purity and reduced particle size without agglomeration. The precipitated magnesium hydroxide is characterized by the particle size distribution determined by the laser scattering method in the range of 20 nm–2 mm, and by the SEM analysis. Likewise, in order to investigate the effect of particle size on the thermal stability, thermokinetic study of magnesium hydroxide samples was performed by non-isothermal thermogravimetry in an inert atmosphere at different heating rates. The gained thermogravimetric data were utilized for the kinetic analysis, which was performed by using the isoconversional Friedman method in combination with the multivariate nonlinear regression method. For each degradation stage of investigated samples, kinetic parameters (activation energy, pre-exponential factor and kinetic model) were calculated and compared.
The main objective of this work is to investigate how the addition of the magnesium hydroxide particles affects thermal properties and consequently the mechanism of thermal degradation of ...polyethylene oxide. With this aim, polyethylene oxide composites, with different composition of magnesium hydroxide particles derived from the sea bittern residual, were prepared via hot melt extrusion. Non-isothermal thermogravimetry in nitrogen atmosphere was utilized, and on gained data, the kinetic analysis was performed. Activation energy, pre-exponential factor and kinetic model were calculated and compared. TG analysis revealed that thermal degradation of composites starts at lower temperatures, which could be an indication of magnesium hydroxide destabilizing effect on polyethylene oxide. Kinetic analysis showed that all composites degrade through three degradation stages. In the first stage, the sample with max load of inorganic particles resulted in the diffusion as the rate-controlling process, while in the second, denoted as the main stage, thermal degradation of all samples proceeded via the same accelerating reaction type. However, at higher mass fraction of inorganic particles, the addition of the magnesium hydroxide particles altered the mechanism of thermal degradation of polyethylene oxide.
High purity magnesium hydroxide has been synthesised from seawater with the addition of dolomite lime as reagent. High intensity ultrasound-assisted crystallization of magnesium hydroxide was carried ...out during precipitation with the intention to obtain fine particles of Mg(OH)2 as well as to prevent their agglomeration. Investigations were conducted on magnesium hydroxide samples in the form of sludge and voluminous powder. The composition, morphology, and properties of the product were determined by chemical, XRD, FTIR, and SEM/EDS analysis. The particle size distribution was detected by the laser light scattering method. The results showed that the mean particle size of magnesium hydroxide sludge was 5.75 µm, while voluminous powder was 7.58 µm. The morphology of magnesium hydroxide voluminous powder was in the form of aggregated filamentous (up to 300 nm in size) or flake structures.
Magnezijev hidroksid visoke čistoće sintetiziran je iz morske vode uz dodatak dolomitnog vapna. Ultrazvukom visokog intenziteta potpomognuta kristalizacija magnezijeva hidroksida tijekom precipitacije odvijala se u svrhu dobivanja što finijih čestica Mg(OH)2 i sprječavanja njihove aglomeracije. Ispitivanja su provedena na uzorcima magnezijeva hidroksida u obliku mulja i voluminoznog praha. Sastav, morfologija i svojstva dobivenog produkta analizirani su kemijskom, XRD, FTIR i SEM/EDS analizom. Raspodjela veličine čestica određena je metodom raspršenja laserskog svjetla. Rezultati ukazuju na to da je srednja veličina čestica magnezijeva hidroksida u obliku mulja 5,75 µm, dok je u voluminoznom prahu 7,58 µm. Morfologija voluminoznog praha magnezijeva hidroksida je u obliku aglomeriranih nitastih (duljine do 300 nm) i ljuspičastih struktura.
In this study, seawater bittern, a by-product of sea salt production containing a concentrated inorganic substance, was used to recover magnesium in the form of nanostructured magnesium ...hydroxide/oxide. Mg(OH)
2
/MgO nanostructures from seawater bittern were synthesized by a precipitation method with different addition of PVA surfactants. The aim of this study was to investigate the effects of PVA surfactant on the morpho-structural properties and thermal behavior of MgO nanostructures. Simple control of the morphology and particle size of MgO nanostructures obtained by the addition of PVA was performed during synthesis. XRD structural analysis showed that the synthesized MgO samples have good crystalline nature. The average crystallite size of the samples is 26 nm, 26 nm, 23 nm, 24 nm, 23 nm and 23 nm, respectively, which decreases with increasing PVA content. Based on the average particle size, the optimum addition of poly(vinyl alcohol) is at a mass ratio of 1:1.5, since the smallest particles are obtained and have a uniform distribution. The SEM and TEM observations show an improvement in the agglomeration behavior of MgO nanoparticles by increasing the PVA content. The constituents of the samples were confirmed by XRF and EDS analysis.
Modification of poly(lactic acid) (PLA) was performed with the surface modified magnesium hydroxide (mMH) obtained from seawater. Surface modification of MH with different amount of stearic acid (SA) ...results in chemically bonded SA, stearate as confirmed by Fourier transform infrared spectroscopy (FT-IR). Based on FT-IR and X-ray diffraction (XRD) analysis modified filler with a higher amount of SA was used for the composite preparation. PLA/m10MH composites were prepared using laboratory mixing extruder. Differential scanning calorimetry (DSC) was applied to study thermal properties and crystallinity of PLA/mMH composites, while the thermal stability was performed by thermogravimetric analysis (TG). According to DSC analysis, PLA crystallization is primary influenced by the filler. PLA/m10MH composites degrade in four degradation stages. With an increase of m10MH content in the composites, their thermal degradation becomes more complex and their thermal stability is getting worse. XRD and X-ray microcomputed tomography (XμCT), used to obtain structural and microstructural information about PLA/m10MH composites, revealed that addition of m10MH decreases the crystallinity of PLA, increases the porosity of the composite and produces agglomeration of mMH.
In order to improve the properties of sintered MgO (80 % precipitation) obtained from seawater, an investigation was carried out with (0, 1, 2) w/% of nano-TiO2 and micro-TiO2 additions during ...sintering at a temperature of 1500 °C (1 h and 2 h). The effects of the TiO2 addition on its microstructural properties, density, porosity and chemical composition after sintering were observed. The SEM/EDS analysis confirmed the formation of a homogeneous microstructure composed mainly of periclase grains and well-distributed secondary phases. CaTiO3 and MgTiO4 are predominantly located at the inter- and intra-periclase grain boundary surfaces during cooling. The microstructure of the MgO samples with the addition of nano-TiO2 become more compact, having a positive impact on the porosity and density of the samples. The addition of 1 w/% of nTiO2 represents the optimal amount for the improvement of the properties of the MgO samples (80 % precipitation) obtained from seawater.
The purpose of this study was to investigate the influence of a rinsing of
Mg(OH)2 precipitated from seawater by substoichiometric precipitation (80%
precipitation) and the addition of TiO2 on ...microstructural characteristics of
the MgO obtained by sintering at low temperature (1400?C). The results of
examination indicate that the method of rinsing of the magnesium hydroxide
precipitate in the technological process of obtaining MgO from seawater
significantly affects the chemical composition of samples, primarily with
regard to the CaO and B2O3 content. The samples were doped with TiO2 to
improve the evaporation of B2O3 and sintering of MgO samples that were
characterized by XRD and SEM/EDS. These techniques confirmed the high purity
of MgO samples obtained and the formation of secondary compounds in very
small quantities that have a positive effect on the densification.
nema
Understanding the degradation behavior of polymer composites is crucial for their practical application, especially in areas such as biomedicine and environmental engineering. In this study, we ...investigated the influence of titanium dioxide (TiO2) particle size and content, containing 0.5, 1, 2, 5, and 10 wt% m/nTiO2, on the degradation mechanism of biodegradable polycaprolactone (PCL) biocomposites. The degradation kinetics of the prepared biocomposites were evaluated using the Friedman method in conjunction with multivariate nonlinear regression facilitated by the Netzsch Thermokinetics software. The results indicate different degradation mechanisms for PCL biocomposites containing TiO2 microparticles compared to biocomposites containing TiO2 nanoparticles. However, the PCL biocomposites with TiO2 microparticles showed a three-step degradation process, and the PCL biocomposites with TiO2 nanoparticles exhibited a four-step degradation process. This difference can be attributed to the observed agglomeration of TiO2 nanoparticles within the PCL matrix, which leads to an additional diffusion step in the degradation process. Interestingly, the addition of TiO2 particles did not change the basic degradation mechanism of PCL but prolonged the degradation process to a higher conversion range. These findings shed light on the complicated interplay between the properties of the filler particles and the behavior of the polymer matrix and provide valuable clues for the design and optimization of biodegradable biocomposites.
Magnezijev hidroksid visoke čistoće sintetiziran je iz morske vode uz dodatak dolomitnog vapna. Ultrazvukom visokog intenziteta potpomognuta kristalizacija magnezijeva hidroksida tijekom ...precipitacije odvijala se u svrhu dobivanja što finijih čestica Mg(OH)2 i sprječavanja njihove aglomeracije. Ispitivanja su provedena na uzorcima magnezijeva hidroksida u obliku mulja i voluminoznog praha. Sastav, morfologija i svojstva dobivenog produkta analizirani su kemijskom, XRD, FTIR i SEM/EDS analizom. Raspodjela veličine čestica određena je metodom raspršenja laserskog svjetla. Rezultati ukazuju na to da je srednja veličina čestica magnezijeva hidroksida u obliku mulja 5,75 µm, dok je u voluminoznom prahu 7,58 µm. Morfologija voluminoznog praha magnezijeva hidroksida je u obliku aglomeriranih nitastih (duljine do 300 nm) i ljuspičastih struktura.
Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna .
Scientific and technical terminology represents a very topical issue in economically and technologically dependent countries with small languages such as Serbian. The current terminological problems ...in the Serbian language, especially in specialized areas that are experiencing dynamic development, are: Anglicization of the language for special purposes, underdeveloped and unstable terminology, and lack of adequate and modern terminological and lexical resources. On the one hand, the terminological problems listed above are of concern to subject-field specialists, since inadequate and non-existent terminology significantly affects the representation, transfer and management of specialized knowledge and information. On the other hand, terminology and language planners point to the growing need for immediate and systematic intervention aimed at terminology harmonization, consolidation and standardization. In spite of the awareness, there is no systematic approach to the solving of terminological problems in Serbian. In addition, practical activities regarding the collection and organization of terminology are few and reduced to individual initiatives. Under the paradigm of language planning (LP)-oriented terminology management (2), this paper is going to address a practical activity of terminology management: the creation of a Serbian management terminology database (TDB) with equivalent terms in English. The paper will discuss the methodology of terminology work, potential obstacles in termbase creation, as well as potential benefits that such a resource would have on all its potential users: management specialists and practitioners, professional translators, and language and terminology planners. A particular focus will be placed on the potential significance that this kind of a database would have for terminology policy and planning in the Serbian language, on the one hand, and knowledge transfer and management, on the other hand.
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