The Effect of the Multi-doping Strategy on Stabilization of the Cubic δ-phase in the Bi2O3-based Solid Electrolyte Systems in Terms of the SOFC Applications

In this study, the effects of multi-doping strategy on phase stabilization and electrical conductivity for the doped Bi 2 O 3 system were investigated. All solid mixtures were created by solid state reactions according to a certain stoichiometric ratio in atmospheric conditions. The structural, electrical, thermal and surface characterizations of the created samples were performed by x-ray diffraction method (XRD), four point-probe technique (4-PPT), differential thermal analysis/thermo gravimetric analysis (DTA/TGA) and scanning electron microscope (SEM), respectively. From XRD results, it was seen that the fcc δ-phase could be stabilized by using only 1:1:1:2 or 2:2:2:1 dopant content ratio (in here, “1:” is corresponds to” 5%” mole). The other compounds prepared out of this ratios were mixed phase because of the containing both α-phase peaks and δ-phase peaks on their XRD pattern. When the all samples were compared in terms of electrical conductivity at 750 °C, it was observed that the fcc δ-phase stabilized samples exhibited higher conductivity than that of other compounds as expected. The highest electrical conductivity was for the sample, dopant content ratios of which are 1: 1: 1: 2, with 0.014 S.cm -1 at 750 °C and also it had the lowest activation energy (0.51 eV) among all samples. On the other hand, according to the thermal analysis results, it was concluded that phase transition occurred only on the DTA curve of the sample given with dopant content ratios 1:1:1:1 due to presence of endothermic peak on its DTA curve at 729°C during the heating process. Also, for this sample, it was clearly predicted from the electrical conductivity graphs depending on temperature that the phase transition occurred at just that temperature (729 °C) due to the sudden increase in conductivity by indicating phase transition from the α-phase to the cubic δ-phase. The SEM analysis pointed out that grain size decreased as total dopant ratio increased and also the grain boundary changed sharply with the increase in the total dopant ratio.

Environmental Protection with HDPE Geomembranes in Mining Facility Constructions

The present work evaluated two high-density polyethylene (HDPE) geomembranes exhumed from mining facility constructions in Brazil. The MIN sample was exhumed from a pond for water use for the iron ore process after 7.92 years of exposure. The MIN2 sample was exhumed from a spillway channel of a ferronickel tailing dam after 10.08 years of service. The physical evaluations showed high depletion for antioxidants that work in the temperature range of 200 °C. The samples presented brittle tensile behavior and had similar behaviors between stress cracking and tensile. Low tensile elongation values and low-stress crack resistance were noted. The MIN2 sample presented a higher melt flow index (MFI) value and lower stress crack resistance. Thermogravimetric curves (TG) under synthetic air purge gas evaluation showed that both samples presented a similar behavior during the evaluation but had several mass losses. The results showed that exothermic and endothermic events occurred with loss of mass and showed no combustion events in the differential thermal analysis (DTA) curve evaluation. Differential scanning calorimetry (DSC) analysis showed no changes in the samples’ behavior. Thus, the results of tensile, stress cracking, and viscosity properties can demonstrate that changes in polymer structure occurred after field exposures.

In Situ High-Temperature X-ray Powder Diffraction and Infrared Spectroscopic Study of Melanterite, FeSO4·7H2O

The thermal behavior of melanterite from the Fornovolasco mine (Tuscany, Italy) has been investigated via differential thermal analysis (DTA), thermogravimetry (TG), in situ high-temperature X-ray powder diffraction (XRPD) and Fourier-transform infrared spectroscopy (FTIR). The DTA curve showed endothermic peaks at 70, 100, 260, 500–560 and 660 °C whereas the TG curve evidenced a total mass decrease of ~68%, in keeping with the loss of all H2O and SO4 groups. Rietveld refinements were performed for all the collected patterns in the 25–775 °C range and converged at 1.57 ≤ R (%) ≤ 2.75 and 1.98 ≤ Rwp (%) ≤ 3.74. The decomposition steps FeSO4·7H2O → FeSO4·4H2O (25 ≤ T ≤ 50 °C) → FeSO4·H2O (50 < T ≤ 100 °C) → FeOHSO4 (75 < T ≤ 200 °C) → Fe2(SO4)3 (400 < T ≤ 500 °C) → Fe2O3 (500 < T ≤ 775 °C) were obtained. The high-temperature infrared analysis confirmed that melanterite undergoes a three-step dehydration in the 25–300 °C temperature range. The FeOHSO4 phase is stable over a wide range of temperature and transforms partially to Fe2(SO4)3 without the formation of Fe2O(SO4)2. The findings highlight a different behavior of the studied sample with respect to the synthetic salt.

Determination of the Order of Kinetics of a DTA Curve by Using the Concept of Skewness

In the present paper, a novel way of finding out the order of kinetics of differential thermal analysis (DTA) curves by using the concept of skewness (Sk) has been investigated. It is found that for a particular DTA peak, skewness is a function of both the order of kinetics and the quantity, First order DTA peaks are characterized by negative skewness whereas those for the second order are characterized by positive skewness. Therefore, skewness can be used as an indicator of the order of kinetics of a DTA peak. We have evaluated and compared the orders of kinetics of some reported DTA peaks using the concept of skewness and found that the resulting values of the orders of kinetics are in fair agreement with those reported in literature.

Simultaneous Differential Thermal Analysis and Thermogravimetric Analysis of Si-30B Alloy

This article focuses on the experimental determination of the transformation temperature of Si-30B alloy in the temperature range of 25-1820 °C in a flowing gas atmosphere (He, 99.9992%) carried out by simultaneous differential thermal analysis and thermogravimetric analysis (DTA–TG) using a graphite container. The DTA curve during heating showed the presence of two critical temperatures, i.e., T = 1380.7 °C and T = 1532.0 °C. The first one corresponds to the melting point of a eutectic system (Si + SiB6). The high-temperature interaction and reactivity between the alloy and the container during DTA–TG test were evaluated by scanning electron microscopy coupled with energy-dispersive x-ray analysis. The results have demonstrated that the graphite container reacts with both liquid silicon and boron dissolved in liquid constituent of the alloy to form SiC and B4C, respectively.

Study on Physicochemical and Thermal Properties of Tetrabutylammonium-Based Cation Ionic Salts Induced by Al2O3 Additive for Thermal Energy Storage Application

The physicochemical and thermal properties of tetrabutylammonium bromide (TBA-Br) and tetrabutylammonium hexafluorophosphate (TBA-PF6), and their change with the addition of Al2O3, were investigated using infrared (IR) spectroscopy and by simultaneously conducting thermal thermogravimetric (TG) analysis and differential thermal analysis (DTA) to obtain the differential scanning calorimetry (DSC) thermogram. The change in the IR data is characterized by the growth of a large peak in the range of 3500 cm−1 and the reduction of peaks below 1000 cm−1 with the additive concentration. The decomposition temperature determined from the peak in the DTG curve is nearly constant for TBA-Br, and it decreases with the addition of Al2O3 for TBA-PF6, although it does not depend on the concentration of the additives. The DTA curve of ionic salts with the addition of Al2O3 shows additional peaks, which indicates a change in the sample’s temperature at disorder or phase transitions. The variation in the melting temperature with additive concentration is similar to that of decomposition temperature. The maximum heat of fusion value was approximately 67 kJ kg−1 for the doped TBA-Br and TBA-PF6 but was achieved at a different additive concentration. This is due to the additional disorder in the system induced by the dissolution of Al2O3.

Properties of Linear Low Density Polyethylene

As result of the modification of polyolefin, composite materials based on them were obtained for the use in special equipment in order to entrain their heat resistance. Data analysis DTA (differential thermal analysis) of the DTA curve of this polyethylene sample suggests a bimodal nature of their MWD (molecular weight distribution) which differs from polyethylene with unimodal MWD and a series of endo oxidation effects with a maximum temperature of 245, 335, 358 and 435 °С. X-ray structural studies showed that the crystal system and the size of the unit cells of the crystal lattice of LLDPE practically does not differ from those of LDPE. LLDPE as well as LDPE and HDPE has a layered structure with dense packing of macromolecules. In terms of crystallinity and crystallite sizes, LLDPE are on par with HDPE and significantly differ from LDPE. These data are in agreement with published data. The parameters of the unit cells of the crystal structure of UHMWPE are close to those of LLDPE, and by crystallinity it occupies middle ground between HDPE and LLDPE.

A Fast and Robust Approach for the Green Synthesis of Spherical Magnetite (Fe3O4) Nanoparticles by Tilia tomentosa (Ihlamur) Leaves and its Antibacterial Studies

Background: In the past few years, Magnetite (Fe3O4) nanoparticles have gained a significant research interest in the field of biology, chemistry, metallurgy due to their wide range of applications. Some of their important applications include drug delivery, chemotherapy, low-friction seals, magnetic fluid, adsorbent, recovery of hazardous wastes, etc. Methods: In the present paper, we reported an eco-friendly route of preparing magnetite nanoparticles by using leaves of Tilia Tomentosa (Ihlamur) followed by calcination at 400 ˚C for 15 minutes. Results: The bandgap energy of the prepared Fe3O4 nanoparticles was studied by UV–Visible spectroscopy and the value was found to be 3.31 eV. The scanning electron microscopy (SEM) image showed the spherical magnetite nanoparticles with an average size of 25 nm. The phases and thermal properties of Fe3O4 nanoparticles were studied by using X-ray diffraction, thermogravimetric (TG) and differential thermal analysis (DTA). The enthalpy change of Fe3O4 nanoparticles was calculated by using the DTA curve and the value was found to be 4.97 kJ/mol at 8˚C/min heating rate. The antimicrobial activity of Fe3O4 nanoparticles was carried out by the minimum inhibition concentration (MIC) assay method. Except for B. subtilis, Fe3O4 nanoparticles demonstrated significant antibacterial property. Conclusion: The prepared magnetite nanoparticles showed excellent thermal stability and less weight loss over a 30–1000 ˚C temperature range. The size of the prepared magnetite nanoparticles is very less therefore they interacted effectively with the organelle, enzymes, and cells of bacteria and inhibited bacterial growth by killing them.

Thermal Decomposition and Kinetic Studies of Pyrolysis of Spirulina Platensis Residue

Analysis of thermal decomposition and pyrolisis reaction kinetics of Spirulina platensis residue (SPR) was performed using Thermogravimetric Analyzer. Thermal decomposition was conducted with the heating rate of 10, 20, 30, 40 and 50oC/min from 30 to 1000oC. Thermogravimetric (TG), Differential Thermal Gravimetric (DTG), and Differential Thermal Analysis (DTA) curves were then obtained. Each of the curves was divided into 3 stages. In Stage I, water vapor was released in endothermic condition. Pyrolysis occurred in exothermic condition in Stage II, which was divided into two zones according to the weight loss rate, namely zone 1 and zone 2. It was found that gasification occurred in Stage III in endothermic condition. The heat requirement and heat release on thermal decomposition of SPR are described by DTA curve, where 3 peaks were obtained for heating rate 10, 20 and 30°C/min and 2 peaks for 40 and 50°C/min, all peaks present in Zone 2. As for the DTG curve, 2 peaks were obtained in Zone 1 for similar heating rates variation. On the other hand, thermal decomposition of proteins and carbohydrates is indicated by the presence of peaks on the DTG curve, where lignin decomposition do not occur due to the low lipid content of SPR (0.01wt%). The experiment results and calculations using one-step global model successfully showed that the activation energy (Ea) for the heating rate of 10, 20, 30, 40 and 50oC/min for zone 1 were 35.455, 41.102, 45.702, 47.892 and 47.562 KJ/mol, respectively, and for zone 2 were 0.0001428, 0.0001240, 0.0000179, 0.0000100 and 0.0000096 KJ/mol, respectively.Keywords: Spirulina platensis residue (SPR), Pyrolysis, Thermal decomposition, Peak, Activation energy.Article History: Received June 15th 2017; Received in revised form August 12th 2017; Accepted August 20th 2017; Available onlineHow to Cite This Article: Jamilatun, S., Budhijanto, Rochmadi, and Budiman, A. (2017) Thermal Decomposition and Kinetic Studies of Pyrolysis of Spirulina platensis Residue, International Journal of Renewable Energy Development 6(3), 193-201.https://doi.org/10.14710/ijred.6.3.193-201

DEKOMPOSISI TERMAL PROPELAN KOMPOSIT BERBASIS AMONIUM PERKLORAT/HYDROXY TERMINATED POLYBUTADIENE (AP/HTPB)

Thermal decomposition process of AP/HTPB solid propellant type RUM, 450 and 1220 were investigated by DTG60 (Differential Thermogravimetric) with operational parameters: temperature 30 – 400oC, nitrogen flow rate 50 ml/min, and heating rate 2.5 C/min. Thermal decomposition analysis will be the first step of decomposition kinetics research in determining life time of the propellant. TGA curve of propellant RUM was found to be two staged meanwhile the thermal decomposition of propellant 450 and 1220 has become one staged. The DTA curve/thermogram of propellant RUM show the formation of intermediate product before full-length decomposition. Unlike propellant RUM, DTA curves of propellant 450 and 1220 do not show the formation of intermediate product. Decomposition process of propellant 450 and 1220 accelerate by Al presence. The difference between AP modal on propellant 450 and 1220 show insignificance effect to the amount of decomposition energy consumption. Abstrak Proses dekomposisi termal propelan padat AP/HTPB jenis RUM, 450 dan 1220 telah dianalisis menggunakan Differential Thermogravimetric 60 (DTG) dengan parameter operasi: suhu 30 - 400⁰C, atmosfer nitrogen berlaju alir 50 ml/menit, dan laju pemanasan 2,5⁰C/menit. Analisis dekomposisi termal adalah langkah awal penelitian kinetika dekomposisi propelan dalam menentukan life time propelan. Kurva TGA menunjukkan bahwa propelan RUM mengalami proses dekomposisi dua tahap sedangkan propelan 450 dan 1220 mengalami proses dekomposisi satu tahap. Kurva DTA/ termogram proses dekomposisi propelan RUM menunjukkan adanya pembentukan produk intermediate sebelum akhirnya terdekomposisi sempurna. Berbeda dengan propelan RUM, termogram propelan 450 dan 1220 tidak menunjukkan terbentuknya produk intermediate. Proses dekomposisi propelan 450 dan 1220 terakselerasi oleh keberadaan Al. Perbedaan modal AP pada propelan 450 dan 1220 ternyata tidak begitu berpengaruh pada nilai konsumsi energi proses dekomposisi.