Study on Thermal Decomposition Behavior, Gaseous Products, and Kinetic Analysis of Bis-(Dimethylglyoximato) Nickel(II) Complex Using TG-DSC-FTIR-MS Technique

The fiber-like bis-(dimethylglyoximato) nickel(II) complex, Ni(DMG)2 was successfully synthesized. The obtained samples were characterized by SEM-EDS, FT-IR, XRD, and XPS. The TG-DSC-FTIR-MS coupling technique was used to characterize the thermal decomposition behavior and evolved gas analysis of Ni(DMG)2. The non-isothermal decomposition reaction kinetic parameters were obtained by both combined kinetic analysis and isoconversional Vyazovkin methods. It was found that Ni(DMG)2 begins to decompose at around 280 °C, and a sharp exothermic peak is observed in the DSC curve at about 308.2 °C at a heating rate of 10 °C·min−1. The main gaseous products are H2O, NH3, N2O, CO, and HCN, and the content of H2O is significantly higher than that of the others. The activation energy obtained by the combined kinetic analysis method is 170.61 ± 0.65 kJ·mol−1. The decomposition process can be described by the random nucleation and growth of the nuclei model. However, it was challenging to attempt to evaluate the reaction mechanism precisely by one ideal kinetic model.

Utilization of Waste Bamboo Fibers in Thermoplastic Composites: Influence of the Chemical Composition and Thermal Decomposition Behavior

In this study, four types of waste bamboo fibers (BFs), Makino bamboo (Phyllostachys makinoi), Moso bamboo (Phyllostachys pubescens), Ma bamboo (Dendrocalamus latiflorus), and Thorny bamboo (Bambusa stenostachya), were used as reinforcements and incorporated into polypropylene (PP) to manufacture bamboo–PP composites (BPCs). To investigate the effects of the fibers from these bamboo species on the properties of the BPCs, their chemical compositions were evaluated, and their thermal decomposition kinetics were analyzed by the Flynn–Wall–Ozawa (FWO) method and the Criado method. Thermogravimetric results indicated that the Makino BF was the most thermally stable since it showed the highest activation energy at various conversion rates that were calculated by the FWO method. Furthermore, using the Criado method, the thermal decomposition mechanisms of the BFs were revealed by diffusion when the conversion rates (α) were below 0.5. When the α values were above 0.5, their decomposition mechanisms trended to the random nucleation mechanism. Additionally, the results showed that the BPC with Thorny BFs exhibited the highest moisture content and water absorption rate due to this BF having high hemicellulose content, while the BPC with Makino BFs had high crystallinity and high lignin content, which gave the resulting BPC better tensile properties.

Isothermal oxidation kinetics and oxidation behavior of nickel slag

To improve the reduction effect of nickel slag in preparing Fe–Co–Ni–Cu alloy, an oxidization pretreatment was carried out to changing the structure and phase of silicate and sulfide for the nickel slag before the reducing process. The oxidation behavior and kinetics of nickel slag under different temperature and time conditions were discussed. The results shown that in the oxidation process of nickel slag, the part of Fe2SiO4 was oxidized to Fe3O4 and further to Fe2O3, and the other part of Fe2SiO4 directly oxidized to Fe2O3. Meanwhile, the nickel, cobalt and copper in the form of silicate and sulfide were changed into oxides. The changes of the phases are beneficial to the subsequent reduction of nickel slag. The oxidation degree of nickel slag reached 98% under suitable oxidation conditions (900 °C, 15 min). The oxidation kinetic model of nickel slag obtained by Ln–Ln analysis and Model-fitting method was three-dimensional diffusion at lower temperature (300 °C, 400 °C and 500 °C) and random nucleation at higher temperature (700 °C, 900 °C and 1000 °C) respectively. The activation energies obtained by the model method and the model-free method were 28.58 kJ.mol−1 and 26.28 kJ.mol−1 at lower temperature (300 °C, 400 °C and 500 °C) respectively, and the corresponding value were 81.98 kJ.mol−1 and 78.36 kJ.mol−1 at higher temperature (700 °C, 900 °C and 1000 °C) respectively. The activation energy calculated by the two methods was relatively close, and both can be used to calculate the activation energy.

Mineralogical Characteristics and Isothermal Oxidation Kinetics of Ironsand Pellets

An in-depth understanding of mineralogical characteristics and the oxidation behaviors of ironsand is of great significance to make the best of ironsand and develop Ti-containing pellets. This paper quantitatively characterized the mineralogical characteristics of the ironsand from East Java in Indonesia through X-ray diffraction (XRD-Rietveld) and scanning electron microscope (SEM-EDS). The results indicated that the mineral composition of the ironsand was magnetite (22.7%), titanomagnetite (40.9%), enstatite (17.1%), hematite–ilmenite solid solution (14.5%), and magnesium iron aluminum silicon oxide (5.8%). The microstructure characterization of pellets after oxidation showed that the porosity of the pellets decreased from 20.7% to 11.7% with temperatures ranging from 1073 to 1473 K. Moreover, the activation energies of ironsand pellets were calculated by using model-function method. The calculated data of different mechanism functions indicated that the chemical reaction mechanism for the early stage of the oxidation fit A2 (random nucleation and nuclei growth) well, the chemical reaction mechanism for the post-oxidation at 1073–1273 K fit F1 (chemical reaction) well, and the chemical reaction mechanism for the post-oxidation at 1373 and 1473 K fit D4 (diffusion) well. The reaction mechanism and the limited link was finally discussed based on the kinetic analysis and the mineralogical characteristics.

EVALUASI KINETIKA DEKOMPOSISI TERMAL PROPELAN KOMPOSIT AP/HTPB DENGAN METODE KISSINGER, FLYNN WALL OZAWA DAN COATS - REDFREN

Decomposition of propellant Mechanism and kinetics have been investigated by using DTG/TA with three different methods: Kissinger, Flynn Wall Ozawa and Coats & Redfern. This research aims to determine decomposition kinetic parameters of LAPAN’s propellant. The propellants have different composition of Al and AP modal. RUM propellant consist of AP/HTPB. 450 propellant consists AP/HTPB/Al (bimodal). Meanwhile 1220 propellant consists of AP/HTPB/Al (trimoda). Thermal analysis takes place at 30 – 400oC and nitrogen atmosphere flow rate is 50 ml/min. The result according showed that propellant was decomposed by F1 mechanism (random nucleation with one nucleus on the individual particles). Activation energy of propellants are in range between 100.876 – 155.156 kJ/mol meanwhile pre-exponential factor are in range between 4.57 x 107 – 3.46 x 1012/min. Activation energy (E) as well as pre-exponential factor for 1220 propellant is the lowest among the others. AP trimodal application generates catalytic effect which decreases activation energy. 1220 propellant is easier to decompose (easier to react) than RUM and 450 propellant. AbstrakMekanisme dan kinetika dekomposisi propelan telah diinvestigasi menggunakan DTG/TA dengan tiga jenis metode yang berbeda yaitu Kissinger, Flynn Wall Ozawa dan Coats & Redfern. Penelitian ini bertujuan untuk mengetahui parameter kinetika dekomposisi propelan LAPAN. Propelan yang digunakan memiliki perbedaan komposisi Al dan jenis moda AP. Propelan RUM adalah propelan AP/HTPB. RX 450 adalah AP/HTPB/ Al (bimoda). Sementara itu, RX 1220 adalah AP/HTPB/ Al (trimoda). Pengujian termal berlangsung pada suhu 30 - 400oC dan atmosfer nitrogen berlaju alir 50 ml/menit. Hasil penelitian mengungkapkan bahwa semua jenis propelan terdekomposisi dengan mekanisme F1 (nukleasi acak dengan satu nukleus pada partikel individu). Energi aktivasi propelan berkisar antara 100,876 – 155,156 kJ/mol sementara faktor pre-eksponensial berkisar antara 4,57 x 107 – 3,46 x 1012/min. Energi aktivasi (E) dan faktor pre-eksponensial (A) RX 1220 adalah terendah dari ketiga sampel. Penggunaan jenis AP trimodul menciptakan efek katalitik yang menurunkan besarnya energi aktivasi. Propelan RX 1220 lebih mudah terdekomposisi (lebih mudah bereaksi) daripada propelan RUM dan RX 450.

Thermal stability and thermal decomposition kinetics of Ginkgo biloba leaves waste residue

Non-isothermal thermogravimetric (TG) analysis was used to investigate the thermal stability and kinetics of three types of Ginkgo biloba leaves. These three types of Ginkgo biloba leaves included: Ginkgo biloba leaves before enzymolysis and ultrasound extraction (G1), Ginkgo biloba leaves after enzymolysis and ultrasound extraction (G2), and Ginkgo biloba leaves after soxhlet extraction (G3). Thermogravimetric/dynamic thermogravimetric, (dynamic TG) experiments indicated that the thermal stability of G2 and G3 were weaker than G1. Kissinger, Flynn-Wall-Ozawa, Friedman, and Coats-Redfern methods were firstly utilized to calculate the kinetic parameters and predicted decomposition mechanism of G1, G2, and G3. The thermal decomposition of G1, G2, and G3 were all corresponded to random nucleation and growth, following the Avrami-Erofeev equation, and activation energy of which were 191.4, 149.9, and 201.6 kJ/moL, respectively. In addition, the thermal decomposition G1, G2, and G3 were endothermic, irreversible and non-spontaneous.

Preferential 〈220〉 crystalline growth in nanocrystalline silicon films from 27.12 MHz SiH4 plasma for applications in solar cells

Si-ncs are generally of 〈111〉 crystal orientation from random nucleation within poly-H network at grain-boundary, while Si ultra-ncs preferably harvest 〈220〉 alignment due to thermodynamically preferred grain growth by mono-H bonding at the boundary.