Papers by Keyword: Thermodynamic

Abstract: The current study was carried out to measure the heat resulting from the spontaneous dissociation of some inorganic salts by using sodium chlorate and ammonium perchlorate salts (3gm), iron filings (22gm) with grain size (350 µ), sawdust (7gm) with a size of (200 µ), activated carbon (7gm), and distilled water (8ml), The speed of the reaction was measured and found it was second degree (n=2). Measurement of the heat of the reaction emitted was also studied in several ways, including the direct method from the Vant-Hoff equation and the calorimetric method, in addition to comparing it with the theoretical value of standard heat of formation which showed the dependence of the reaction temperature on the two salts. Moreover, classical methods were used to determine the amount of chlorate and perchlorate radicals by depositional gravimetric analysis and volatilization methods.

Abstract: In order to optimize the composition and microstructure of quasicrystalline strengthened Mg-based alloy, the equilibrium phases of Mg-Zn-Y-Zr alloys with three components were studied by using thermodynamic calculation. The calculated results showed that the equilibrium phases of the three alloys were mainly Liquid phase, α-Mg matrix phase, α-Zr dispersed phase, quasicrystalline strengthening I phase, W phase and Z phase. It was observed that the specific content and temperature range of these phases were different. Among them, alloy 3 had the highest quasicrystalline content. And alloys 1 and 2 contained dispersed phase α-Zr which can lead to grain refinement.

Abstract: The mangosteen rind has O‒H, C=C aromatics, and ethers functional groups, its performance for Au adsorption become an interesting research to both environment and economic purpose. In this study, waste mangosteen rind as eco-friendly adsorbent had been used for Au(III) adsorption. Initiate by maceration for pre-treatment of biosorbent, the mangosteen rind’s perfomance was revealed. Crystalline structure of mangosteen rind was analyzed by X-ray diffraction, while after interaction with Au(III) ions gave three characteristic peaks indicated Au(III) reduction into Au(0). The adsorption followed isotherm Langmuir model and afforded spontaneous reaction that evidenced by enhancement of ∆G° by increasing of temperature (–1.7 at 30 °C to –8.4 at 60 °C). The value of ∆H° and ∆S° were 71.1 kJ mol^–1 and 238.5 J mol^–1 K^–1, respectively.

Abstract: A thermodynamic evaluation of the binary LaCl₃-CaCl₂ system was carried out by using CALPHAD method. The Modified Quasihelical Model was defined in order to describe the Gibbs energies of the liquid phases, and the model parameters were optimized from the experimental thermodynamic and phase diagram data. The phase diagram and the enthalpy of mixing of LaCl₃-CaCl₂ liquid were calculated. For LaCl₃-CaCl₂, a calculated eutectic point was observed at 924.82 K, 34.8 mol. % LaCl₃. The calculated enthalpy of mixing is exothermic, the minimum was found at approximately 30 mol. % LaCl₃. The thermodynamic properties and the phase diagram calculated from the optimized parameters agree well with the experimental data.

Abstract: This In this study, the Ca-Al layered double hydroxide was used as a potential adsorbent for the removal of Congo red from aqueous solutions. The effects of Initial concentration and contact time on the adsorption properties of Congo red by Ca-Al LDHs were studied. The removal rate of Conge red reached to 59.416 mg/g under room temperature with 0.2g of adsorbent, initial concentration of 50 ppm, adsorption time of 210 min, shaking speed of 90r/min. The experimental equilibrium data for the removal of Congo red were evaluated by various isotherm models. The pseudo-second-order kinetic models were found to fit the adsorption kinetics, and the equilibrium data were appropriately fitted to Langmuir and Freundlich model adsorption isotherm.

Abstract: Ni-Al-WC ternary system during self-propagating high-temperature synthesis (SHS) was analyzed and calculated based on thermodynamic principle, and the curves of adiabatic temperature (T_ad) and preheating temperature (T₀) and WC content (wt.%) were drawn. The results showed that adiabatic temperature of the system decreased with the increase of WC content and the maximum of WC content was about 34 wt.% for preheating temperature of 933K. Adiabatic temperature increased with increasing preheating temperature and properly increasing preheating temperature could promote the reaction self-sustaining when WC content was excessive and adiabatic temperature was less than 1912K.

Abstract: To theoretically evaluate three widely used second generation single crystal superalloys-PWA1484, ReneN5 and DD6, the alloy densities, phase graphs, TCP contents, d-electron energy, and creep rupture lives were calculated, and the calculation results were analyzed combined with actual data. Results showed that among the three alloys, PWA1484 had the greatest density, secondly was DD6, and ReneN5’s density was the lowest. The PWA1484 alloy was most likely to precipitate TCP due to its highest d-orbital energy level; the ReneN5 alloy had a medium d-orbital energy level, but its high Cr content induced it to precipitate the most TCP types; the DD6 alloy had the least chance to precipitate TCP phases because of its lowest d-orbital energy level as well as lowest Cr content. It is concluded that thermodynamic calculation had the ability to simulate TCP types and TCP content at steady states, while d-orbital energy concept was capable of exhibiting the alloys in sequence of TCP precipitation potential. Mere thermodynamic calculation will lead to comparatively conservative results, including more TCP types, higher TCP contents and lower rupture lives. Analyzing the thermodynamic and d-orbital energy calculations comprehensively, it can be considered that the DD6 alloy has the most stable microstructure among the three single crystal superalloys.

Abstract: The performance of nanosilver loaded bamboo-based activated carbon as an adsorbent used for the adsorptive removal of formaldehyde in the air. The size porous of the active carbon is predominantly on the size of mesoporous and microporous. Adsorption tests have been evaluated in laboratory scale fixed-bed column, at different temperatures and initial formaldehyde concentration. In order to investigate is both equilibrium and thermodynamic aspects. The experimental data was fitted with Langmuir model and fit well with the adsorption capacity of 91-110 mg/g. The increase in temperature reduces the adsorption capacity. The thermodynamic parameters show that the values of ∆G^o obtained to confirm the feasibility of activated carbon effective sorbents of formaldehyde. The formaldehyde adsorption process is exothermic and adsorbent has a good affinity to formaldehyde.

Abstract: Controlled diffusion solidification (CDS) is a novel and simple process that enables the formation of non-dendritic microstructure of primary Al phase through mixing two liquid alloys of different composition and temperature together. A quaternary alloy (Al-5.0Cu-0.35Mn-0.25Ti, wt.%), having a similar chemical component with ZL205A, was fabricated using controlled diffusion solidification (CDS) method with different mixing temperature. The mixing temperature of two liquids mostly affects the cast structure especially the primary Al phase. Results show that CDS can reduce the element segregation degree inside the grains. Microstructure evolution during solidification initiates from a primary nucleus firstly and then changed to a non-dendritic grain structure. The thermal analysis confirms the thermodynamic conditions for the formation of non-dendritic grain structure evolution.

Abstract: Two important objectives of the automotive industry are the decrease of the body-in-white weight and the improvement of the passenger safety. High strength steels (HSS) are widely used to achieve these objectives. Quenching and partitioning (Q&P) has recently been proposed to achieve high strength steel grades for the third generation of advanced high strength steels (AHSS), which contain a considerable amount of retained austenite. Due to their microstructure these new steel grades combine a high tensile strength with good elongation values, as long as cementite precipitation is avoided. A model describing the involved phase transformations is presented. Special focus is put on the cementite precipitation and how it is influenced by silicon and aluminum additions.