Papers by Keyword: Combustion

Abstract: The synthesis of Ni_0.8Co_0.15Al_0.05O₂ (NCA) cathode material is performed using the one-pot synthesis. This system is combined with the solution combustion method to produce ternary metal oxide (TMO). Nitric acid acts as an oxidizer and various amount of urea act as fuel for the combustion process. NCA material has a good hexagonal layer structure and the average particle size obtained was 1.17 µm. The electrochemical analysis showed that NCA cathode material obtained at a ratio NCA-OH: urea = 1: 2 has the highest specific discharge capacities of 118.617 mAh.g^-1, with a stability of up to 10 cycles.

Abstract: Lithium nickel cobalt manganese oxide, LiNi_1/3Co_1/3Mn_1/3O₂ (NMC 333) become a promising cathode material and attracted much attention to replace the LiCoO₂. The structure, particle size, and morphology are some of the factors that influence the performance of the NMC 333 materials were study in this work. The synthesis method of doped NMC 333 materials was done via combustion method and citric acid was used as a fuel. The final products of LiNi_0.3Mn_0.3Co_0.3Al_0.1O₂ and LiNi_0.3Mn_0.3Co_0.3Al_0.05Ti_0.05O₂ were denoted as 333A and 333AT, respectively. Based on the XRD results, all materials showed a pure, single phase and isostructural with hexagonal α-NaFeO₂. 333AT material show good cation ordering with RIR value of 1.25. It also shows the higher (003) peak intensity and smaller full widths at half maximum (FWHM) indicate this material has higher structural crystallinity and smaller crystallite size than 333A. Meanwhile, FESEM results revealed that all materials have morphology of polyhedral like shape and well-crystallized particles with smooth surfaces. Both materials clearly made up of micro-sized particles with the range particle size from 103 nm to 975 nm. 333A material display slightly larger crystallite size compared to the 333AT material. As a conclusion, doping technique will effect the structural and the morphology of materials.

Abstract: Based on the known data on the concentrations of intermediate substances and taking into account only those elementary reactions whose kinetic parameters are known, the mechanism of CF₃H destruction in a flame of methane-oxygen mixtures of various compositions is developed. It is shown that CF₃H destructs in the flame in reactions with O and OH without regeneration. In rich mixture further conversion of CF₃H mainly occurs due to the reactions of CF₃, CF₂, COF₂ with atomic hydrogen, which provide inhibition of methane combustion in oxygen by trifluoromethane. In stoichiometric and especially in lean mixture a role of oxidative processes involving O and OH increases and the inhibition effect weakens. The obtained scheme qualitatively describes the entire known experimental pattern observed during the combustion of CH₄/O₂/CF₃H mixtures.

Abstract: Diesel combustions produce greenhouse and harmful gases bringing health hazards and negative impact to environment. This study produced biochar from waste palm shell and the biochar was further applied as fuel additive in biodiesel to reduce the nitric oxides emission. The biochar showed high fixed carbon content (85.8 wt%) and low ash content (2.0 wt%). Subsequently, the biodiesel post-combustion emission of NO_X recorded a significant reduction up to 40.6% compared to without application of biochar. This study shows that the mixing of biochar in biodiesel is a potential approach to reduce the nitric oxide emission.

Abstract: This article is devoted to expanding the technological capabilities of the gas-forming stamping method by increasing the pressure of combustion products acting on the surface of a workpiece stamped. Therefore, a scheme of a two-chamber device and a method for compressing the fuel mixture is proposed. The essence of the method is that of carrying out the stamping products under the high gas pressure, which is created by compression and subsequent combustion of the gaseous fuel mixture. To ensure the compression of the fuel mixture, the device is equipped with two combustion chambers separated by a piston. Due to this method, the pressure rises sharply. Under the influence of the combustion products' pressure, the workpiece is intensely deformed and fills the cavity of the matrix. This method of sheet stamping, implemented on a two-chamber device, will increase the gas pressure on the surface of the forged workpiece to 70-80 MPa at a fuel mixture pressure of 1 MPa, which ensures stamping of a variety range of parts in almost all branches of small-scale production related to metalworking.

Abstract: Improvement of fuel efficiency and reduction of carbon dioxide emission are important issues in the automotive and aviation industries. To achieve these issues, materials that are lightweight and have excellent heat resistance are required. For this reason, various alloys have been proposed. Among them, TiAl intermetallic compounds have excellent low specific gravity and high strength at high temperature. However, TiAl is difficult for machining and easily oxidized, so casting is difficult. For this reason, a method using reaction sintering has been studied, though it is difficult to obtain low oxygen concentration TiAl alloy powder. Therefore, the process to produce TiAl parts from Ti powder and Al powder is studied. However, in this method, when a mixed powder of Ti and Al is sintered, a phenomenon called ignition with a rapid temperature increasing may occurs, and ignited parts are swelling and becomes high porosity.

Abstract: Rice husks (RH) are agricultural wastes available abundantly in rice producing country. A by-product obtained from combustion of rice husk is rice husk ash (RHA) which is rich in silica (SiO₂) contents. This paper focused on the effect of acid leaching treatment on rice husk to produce high-purity silica. There are 4 different states of conditions involved; raw rice husk (RRH), treated rice husk (TRH), rice husk ash (RHA), and treated rice husk ash (TRHA). Citric acid; C₆H₈O₇ was used as a leaching agent. TRH and TRHA was leached to see whether treated rice husk before combustion (TRH) or treated rice husk after combustion (TRHA) will produce more high-purity silica. Chemical composition analysis shows high amorphous silica content which is 98.47% with low metallic impurities at 1.0M C₆H₈O₇, 70 oC for treated rice husk (TRH). X-ray diffraction (XRD) pattern shows the presence of amorphous silica in treated rice husk (TRH) and crystalline silica in treated rice husk ash (TRHA). Fragmentation of TRH into small pieces after acid leaching is seen where there is significant increase in the exposed surface areas. High-purity amorphous silica with more than 98% was prepared via citric acid leaching treatment and combustion process.

Abstract: Characteristics and potential of microalgae Spirulina platensis as an energy source were studied in regard to the decomposition patterns, as well as kinetic and thermodynamic parameters. The thermogravimetric analysis was performed using the TGA instrument (Mettler Toledo TG DSC 1) at a heating rate of 30 °C/min, with an atmospheric air flow-rate of 100 ml/min at the temperature range of 25-1000 °C. The kinetic was evaluated using a differential method of Arrhenius. The results showed that Spirulina platensis microalgae decomposed into three stages. The first stage is related to the evaporation of moisture, the second stage is associated with the release of volatile matter, and the final stage is the combustion stage of char. The kinetic evaluation resulted in the respective activation energy (), pre-exponential factor (log A) and reaction order (n) are 53.57 kJ/mol, 4.4 min^-1, and 1.73. It also understands from the thermodynamic analysis that the respective values of enthalpy (), Gibbs free energy ( and the entropies ( were 48.50 kJ/mol, 146,73 kJ/mol, and-174,78 J/mol.

Abstract: The availability of synthetic waste (SW) continuously increases, but on the contrary fossil fuels resources always decrease. The potential of SW for alternative fuel is critical to investigate for overcoming the problem generated from its overabundance and to provide its value-added. In this study, the changes of the macromolecular and the mineralogical during the SW combustion processes were investigated by Fourier Transform Infrared (FTIR) spectroscopy and x-ray diffraction (XRD), respectively. The combustion has been performed by using thermogravimetric analyzer (TGA) at a heating rate of 10 °C/min, from 25 to 1000 °C, with 100 ml/min constant flowrate of air atmosphere. According to the TGA results, the decomposition stage of the sample can be identified as a function of temperature and time. From ambient temperatures to 293 °C the sample experienced the first decomposition process that was correlated with the moisture losses and light volatile release. Macromolecular changes occurred at the temperature 293 °C where functional group of C–H in methylene was decomposed due to the removal of volatile matter. From the temperature of 293 to 485 °C the sample underwent the second stage of decomposition. The XRD result showed that mineral changes occurred at the temperature of 485 °C where the KCl compound was formed. In line with the escalating temperature, SiO₂ was decomposed at a temperature of 590 °C. The final stage occurred at the temperature 625 to 1000 °C indicated by constant of TG line. At 625 °C, XRD result indicated the significant increasing of the CaCO₃ compound.

Abstract: The investigation of Titanium dioxide (TiO₂) nanoparticles on the thermal characteristic of Tetraselmis chuii (T.Chuii) microalgae during combustion process has been carried out through a thermogravimetric (TG) analyzer. T.Chuii microalgae samples were cultured within 8 days at BBPBAP Jepara, Central Java, Indonesia. The microalgae sediment was dried at 80°C for 24 hours then was powdered by means of a mortar. Thereafter, the dried powder of microalgae was filtered with a size of 60 mesh. Titanium dioxide (TiO₂) nanoparticles were used as catalysts with the particle size of < 25 nm; these were obtained from Singapore’s Sigma Aldrich. Amount of 0.03 mg of TiO₂ and 10 mg of T.Chuii microalgae were mixed mechanically using a mortar to guarantee the homogeneous blend, and then this sample was heated up in the oven for 14 hours at 80°C. The TG experiment was performed at a temperature range 25 to 900°C with atmospheric air at a flow rate of 50 mL/min and a heating rate of 15 °C/min. Differential method of Arrhenius is applied to evaluate kinetic parameters, including reaction order (n), activation energy (E_a), and pre-exponential factor (log A) that were 0.9; 74,191 kJ/mol and 6.38 min^-1 for the stage II and 0.87; 118.47 kJ/mol and 7.29 min^-1 for stage V.