Exothermic Research Articles

Analytical assessment of hetero-/homogeneous combustion of magnesium particle: Fully explicit formulas for flame characteristics

In this study, by proposing a comprehensive multi-step model, the combustion of magnesium particles in O2-He, O2-Ar, and O2-N2 is scrutinized. In the current model, both the heterogeneous and homogeneous combustions are considered and the process is divided into four stages solid, liquid, and gas combustion and melting. Moreover, the diffusions of oxygen and unreacted magnesium to droplet and infinity together with surface exothermic reaction are considered. The governing equations are analytically solved and then, the formulas are extracted for combustion time and temperature, flame standoff distance, and evaporation rate as the functions of particle diameter, ambient temperature and pressure, oxygen mass fraction, type of inert gas, and Lewis numbers. For 120 µm particle and oxygen content of 0.05, time contributions of homogeneous and heterogeneous combustions are 85.8% and 14.2%, respectively. The burning time has drastic changes at ambient pressures below l atm, so that the burning time variations relative to the pressure in the environments less than 1 atm and greater than it are equal to 1200–1550 and 70–90 ms/atm, respectively. When the oxygen mass fraction is less than 0.29, combustion in helium-oxygen ends earlier than that in O2-Ar and O2-N2, but for the mass fraction greater than 0.35, it has the longest burning time.

Investigating the impact of common migration substances found in milk packaging on proteases: A multispectral and molecular docking approach

The effects of common migration substances in milk packaging on digestive protease were studied. We choose the common migrants found in eight types of multi-layer composite milk packaging. Enzyme activity experiments revealed that pepsin activity decreased by approximately 18 % at 500 μg/mL of stearic acid and stearamide treatment, while trypsin activity decreased by approximately 18 % only by stearic acid treatment (500 μg/mL). Subsequently, fluorescence spectroscopy, circular dichroism spectroscopy, and molecular docking technology were employed to investigate the inhibition mechanism of protease activity by migrating substances in three systems: stearic acid-trypsin, stearic acid-pepsin, and stearamide-pepsin. Results showed that the inhibitory effect of stearic acid on trypsin is a reversible mixed inhibition, whereas the inhibitory effects of stearic acid and stearamide on pepsin are non-competitive. In all three systems, ΔH < 0, ΔS < 0, and ΔG < 0, indicating the binding process between the migrant and the protease is a spontaneous exothermic process primarily driven by hydrogen bonding and van der Waals forces. In addition, their binding constants are all around 104 L/moL, indicating that there are moderate binding affinities exist between migrants and proteases. The binding process results in the quenching of the protease's endogenous fluorescence and induces alterations in the enzyme's secondary structure. Synchronized fluorescence spectroscopy showed that stearic acid enhanced the hydrophobicity near the Tyr residue of trypsin. The molecular docking results indicated that the binding affinity of stearic acid-trypsin, stearic acid-pepsin, and stearamide-pepsin was –22.51 kJ/mol, −12.35 kJ/mol, −19.28 kJ/mol respectively, which consistent with the trend in the enzyme activity results. This study can provide references for the selection of milk packaging materials and the use of processing additives, ensuring food health and safety.

Synthesis of WL.nZVI/ GAC adsorbent green for chromium removal from aqueous solutions (Characterization, kinetics, isotherms, and thermodynamics)

This paper aims to synthesize zero-valent iron green nanoparticles to remove chromium from aqueous solutions. A granular activated carbon base was used to solve the problem of nanoparticle agglomeration. This study produced zero-valent iron nanoparticles using walnut leaf extract and immobilization on granular activated carbon (WL.nZVI/ GAC). Then, the specifications of the nanocomposite were studied using FE-SEM, EDX, BET, FTIR, and XRD analysis. This study investigated the parameters affecting adsorption, such as pH, adsorbent dose, contact time, pollutant concentration, and temperature. The WL.nZVI/ GAC nanocomposite specifications showed that the nanoparticles are spherical, and the diameter of the iron nanoparticles immobilized on activated carbon was determined in the range of 16.77 to 27.72 nm. XRD results also indicated that the Wl.nZVI/ GAC adsorbent was amorphous. According to EDX analysis, the loaded iron content in WL.nZVI/ GAC was about 1.86 %. pHPZC for WL.nZVI/ GAC nanocomposites was determined in the range of 6.1; In other words, at pH less than 6.1, the adsorbent’s surface charge is positive and can absorb the chromium existing in solution, which is in the form of chromate, well. The results of adsorption process optimization showed that the adsorption of Cr(VI) is optimal at pH = 4, contact time of 780 min, concentration of 80 ppm, and temperature of 298 K. Experimental studies showed that the chromium removal by adsorbent is strongly dependent on pH. The adsorption kinetics of chromium by WL.nZVI/ GAC adsorbent follow the Pseudo-second-order, and the adsorption isotherm follows the Langmuir model. The adsorption of Cr(VI) ions on the Wl.nZVI/ GAC adsorbent is a spontaneous and exothermic process.

"Impact of hydride composite materials on thermochemical hydrogen compression"

The formation of a hydride from a metal or intermetallic alloy is an exothermic reversible chemical reaction. The thermodynamic properties governing hydride formation facilitate their thermochemical applications, such as hydrogen compression. Thermal transport inside the materials is of highest importance for system dynamics and its productivity. In this contribution, we demonstrate a two-stage thermochemical hydrogen compressor using the AB5 alloy LaNi5 in the first stage and an AB2 alloy TiMn2 (Hydralloy®) in the second stage. To evaluate the impact of the thermal conductivity of the materials, the productivity of the compressor was compared for pure metal hydride compacts (MH) and metal hydride composite materials (MHC). Compared to pure MH pellets, the MHC used in this study contain expanded natural graphite (ENG), a secondary phase with highest thermal conductivity. As the radial thermal conductivity of the MHC increased, the time required for the loading, temperature change and unloading steps was successfully reduced by 400%. Productivity was increased by over 320 % from 14 NlH2/(kgMaterial*h) to 44 NlH2/(kgMaterial*h). Overall, MHC have the potential to simplify handling, reactor design and reduce investment costs for thermochemical compression systems. Thus, MHC have highest impact and potential for thermochemical applications.

Optimization of hydrochar production from cigarette filters for enhanced CO2 adsorption

In this study, CO2 capture using Hydrochar adsorbents synthesized from Cigarette Filter, specifically H-208 and HA-204, was rigorously investigated. Optimization using RSM was applied to fit a quadratic model to the data with F-value of 184.95 and R2 of 0.9847. H-208 and HA-204 display maximum CO2 adsorption capacities of 1028.35 mg/g and 1003.35 mg/g, respectively, at 9 bar and 25 °C. Isotherm studies ranked Freundlich and Sips models as effective descriptors, highlighting differences in adsorption behavior between HCs synthesized at different conditions. Kinetic modeling identified the Elovich model as suitable for predicting time-dependent CO2 adsorption. Thermodynamic analysis revealed differences in adsorbent affinity and spontaneity between HCs, with higher enthalpy values for H-208 indicating stronger adsorbent-adsorbate interactions. ΔH° values of −61.863 kJ/mol for H-208 and -47.442 kJ/mol for HA-204, signifying an exothermic adsorption process. The CO2 adsorption mechanism involves physical and chemical processes influenced by the polar structure, surface area, and functional groups of HCs. The effect of HCl on CO2 adsorption is insignificant, and the use of HCl only reduces the synthesis time. Adsorbent reusability tests showed minor capacity declines over multiple cycles, indicating their potential in environmental remediation and industrial gas separation processes.

Thermal Runaway Mechanism in Ni-Rich Cathode Full Cells of Lithium-Ion Batteries: The Role of Multidirectional Crosstalk.

Crosstalk, the exchange of chemical species between battery electrodes, significantly accelerates thermal runaway (TR) of lithium-ion batteries. To date, the understanding of their main mechanisms has centered on single-directional crosstalk of oxygen (O2) gas from the cathode to the anode, underestimating the exothermic reactions during TR. However, the role of multidirectional crosstalk in steering additional exothermic reactions is yet to be elucidated due to the difficulties of correlative in situ analyses of full cells. Herein, the way in which such crosstalk triggers self-amplifying feedback is elucidated that dramatically exacerbates TR within enclosed full cells, by employing synchrotron-based high-temperature X-ray diffraction, mass spectrometry, and calorimetry. These findings reveal that ethylene (C2H4) gas generated at the anode promotes O2 evolution at the cathode. This O2 then returns to the anode, further promoting additional C2H4 formation and creating a self-amplifying loop, thereby intensifying TR. Furthermore, CO2, traditionally viewed as an extinguishing gas, engages in the crosstalk by interacting with lithium at the anode to form Li2CO3, thereby accelerating TR beyond prior expectations. These insights have led to develop an anode coating that impedes the formation of C2H4 and O2, to effectively mitigate TR.

Cellulosic materials for the removal of ciprofloxacin from aqueous environments

Abstract The feasibility of using cellulose from Pinus spp. sawdust from Zomba, Malawi, treated with commercial and lemon-derived citric acid (CA) for ciprofloxacin (CFX) adsorption from water has been tested. Different CA concentrations were used on NaOH-pretreated sawdust for cellulose esterification. The material was analysed using a variety of techniques. Adsorption tests for CFX were performed using the batch method, and the data were analysed using Langmuir, Freundlich, and Temkin’s isotherms. The Fourier transform infrared spectroscopy (FTIR) and point of zero charge results showed surface charges increasing (hydroxyl, −OH, and carboxyl, −COOH groups) due to the CA reaction. The Temkin model was the best fit for the experimental data with R 2 test values of 0.9515, while pseudo-second-order was the best fit (R 2 = 0.9999) in an exothermic adsorption process. The adsorption efficiency was 83% on 0.8 g of the material at pH 4 in 20 mL (20 mg·L−1) CFX. The different CA concentrations during sawdust treatment had a negligible impact on morphology. A regression analysis (R 2 and p-values) of structural data showed that the particle size, distance, and crystallinity index had negligible impact, while surface charges and functional groups had a significant impact on adsorption. Overall, the adsorption of CA-treated sawdust material on CFX is satisfactory.

Coconstruction of Supramolecular Lithium-Conducting Cross-Linked Networks Based on PVDF and Triblock Polymer Nanomicrosphere Solid-State Polymer Electrolytes for Lithium-Metal Batteries.

Uneven lithium plating and low ionic conductivity currently impede the realization of high-capacity rechargeable lithium metal batteries. And the conventional poly(ethylene oxide) (PEO) solid-state electrolytes are unsuitable for high-energy-density Li anode applications due to their low lithium-ion transference number and high reactivity with Li metal, leading to detrimental dendrite formation and potentially hazardous exothermic reactions with the electrolyte. In this study, we employ a supramolecular approach to develop a novel polymer solid-state electrolyte based on poly(vinylidene fluoride) (PVDF) and a novel triblock polymer nanomicrosphere, (poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone), (PCL-PEG-PCL). The abundance of carbonyl and ether-oxygen functional groups in PCL-PEG-PCL enhances the lithium coordination environment within the polymer solid-state electrolyte. Additionally, the original C-F moieties of PVDF form hydrogen bonds with C-H and terminal hydroxyl groups in PCL-PEG-PCL, collectively creating a multichannel fast Li+-conducting supramolecular cross-linked network. The resulting electrolyte demonstrates a high ionic conductivity of 1.4 × 10-3 S cm-1 and an extended electrochemical window of 5.2 V. Moreover, the electrolyte exhibits a high lithium-ion transference number (tLi+ = 0.63) at room temperature and exhibits excellent interfacial compatibility with the lithium metal anode. For the resulting electrolyte utilized in LiFePO4 batteries, the capacity retention of the cells assembled with this electrolyte exceeds 91.3% after 1000 cycles at 25 °C and 2 C (0.281 mA cm-2).

Stone-Wales defective C60 fullerene for hydrogen storage

Hydrogen energy is one of promising non-polluting and renewable energy sources. In this paper, we present a first principal study of hydrogen storage in pure C60 fullerene cage and Stone-Wales (SW) defective C60 cages using density functional theory (DFT) with applying both the exchange functional B3LYP and the dispersion correction wb97xd at 6–31+g(d,2p) basis set. In addition, the counterpoise correction is applied, and the basis set superposition error is calculated. The calculations underscore that the hydrogenation binding energy of C60 cages occurs through an endothermal process for C60Hin with a hydrogen binding energy of 0.09 eV and through an exothermal process for C60Hout, C60SW66Hout, and C60SW65Hout, cages with hydrogen binding energies of −2.17 eV, −2.96 eV, and −2.20 eV, respectively. Remarkably, for the first time, the intermediate hydrogen binding energy is found inside C60SW66Hin fullerene, and C60SW65Hin fullerene cages with energies of −0.26 eV and −0.81 eV, respectively. The hydrogen adsorption inside the cavity of C60SW66 fullerene cage is thermodynamically possible below 289.8 K and entire pressure range considered. Our results highlight, for the first time, that the endohedral cavity of C60SW66 is a promising new medium for hydrogen storage due to its binding energies (−0.26 eV) and its hydrogen storage weight percentage (5.3%) that are close to the optimal conditions specified by DOE for commercial use. In addition, this study opens up a new discovery of Stone-Wales defective C60 fullerene for further endohedral cavity applications.

Production of iron triad-based colored spinels by the self-propagating high-temperature synthesis

Blue, green, and khaki spinels were produced by self-propagating high-temperature synthesis (SHS) using Co3O4–ZnO–Mg(NO3)2·6H2O–Al(OH)3–Al, Ni2O3–ZnO–Cr2O3–Al(OH)3–Al, and Co2O3–Fe2O3–Al(OH)3–Al mixtures. The composition of the synthesis products was characterized by X-ray diffraction and IR spectroscopy. The oxides Co3O4, Co2O3, ZnO, Ni2O3, Cr2O3, Fe2O3, and aluminum hydroxide Al(OH)3 were used for the synthesis. Fuel was provided by aluminum powder (ASD-4). The spinel-type ceramic pigments were synthesized using layer-by-layer combustion, which involves two parallel exothermic reactions: aluminum oxidation and aluminothermic reactions. The fast self-propagating reactions and high synthesis temperatures rapidly destroy the structure of Al(OH)3 hydroxide in the starting mixture, producing gaseous reaction products that prevent the sintering of the spinels. The surface morphology of pigment powders and their composition was studied using a Quanta 3D 200i, FEI Co. scanning electron microscope and a Philips SEM 515 scanning electron microscope equipped with a local energy dispersive X-ray analysis (EDAX). The particle size of the synthesized spinels was approximately 1–5 μm. Colored spinels powders obtained by the SHS process can be used as ceramic pigments.

Numerical analysis of unsteady free convection under the combined influence of inclined magnetohydrodynamic and exothermic chemical reaction in an enclosure filled with nanofluid

Unsteady study of the natural convection of aluminum oxide-water nanofluid within a trapezoidal geometry containing a circular cylinder located at its center. Finite Element method has been considered for the numerical analysis. The proposed investigation handled the impact of Rayleigh number (103–105), chemical reaction parameter (0–4), aluminum oxide nanoparticles volume fraction (0–0.06), magnetic field (0–63) and its inclination angle (0°–90°), and circular obstacle diameter (0.3–0.7) effects on time-dependent natural convection of Al2O3–H2O nanofluid. On the other hand, the value of Prandtl number has kept constant at (Pr = 6.2). Since the nanofluid mobility at φ = 0.02, Ha = 3, and Fk = 1 significantly improved, the heat transfer rate achieved its maximum intensity at Ra = 105. Research also reveals a little effect on heat transfer by increasing the fraction of nanoparticles. Additionally, as Ha intensifies from 0 to 63, a final change in the mean Nusselt number of 28.65 % is displayed. Finally, as the magnetic field angle of rotation is diminished, more enhancement in heat transmission is achieved. This research provides insights into the intricate relationship between natural convection and exothermic reaction under the influences of various conditions. This can illustrate the flow and thermal behaviors of nanofluid in such non-uniform shapes in many engineering applications.

Intermolecular interactions between malvidin-3-O-glucoside and caffeic acid: Structural and thermodynamic characterization and its effect on real wine color quality

The copigmentation effect between malvidin-3-O-glucoside and caffeic acid was comprehensive inquiry on the model wine solution, theoretical simulation and real wine. Thermodynamic parameters were determined by UV/Visible spectroscopy and Isothermal titration calorimetry (ITC). Theoretical data were obtained employing a dispersion-corrected density functional approach. The effects in real wines were investigated by adding the caffeic acid during different fermentation periods. Results shown that the copigmentation reaction between caffeic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersions forces. Computations show that the polyhydroxyl sugar moiety and phenolic hydroxyl groups are the key active sites. The addition of caffeic acid in post-alcohol fermentation samples evidences an improving color characteristics in the wine.

Efficient capture of lead ions from aqueous solution by the functional covalent organic framework materials

Lead is one of the most common harmful metals in aqueous solutions. It has become an urgent need to devise a method that can effectively remove Pb(II) from aqueous solutions. In this paper, a novel covalent organic framework adsorbent was synthesized by post-modification method to remove Pb(II) from aqueous solution. This adsorbent analyzed by adsorption isotherms, kinetic and thermodynamic studies shows that the adsorption is chemically monolayer and controlled by intraparticle diffusion. The whole adsorption process is an exothermic and spontaneous reaction process. The maximum adsorption capacity of the adsorbent for Pb(II) can reach 359.94 mg/g at 298 K and the optimum pH 4. The zeta and density functional theory suggest that the electrostatic and coordination interactions between N, O and S functional groups and Pb(II) play a key role in the adsorption process. The selectivity and reproducibility results showed that this adsorbent was capable of targeted removal of Pb(II) from a polyionic environment and maintained a high adsorption efficiency after 5 cycles. In conclusion, this adsorbent has a very good application in the removal of metal ions from aqueous solutions.

Experimental study for the effect of spark ignition on methanol/PODE dual fuel combustion under medium and low loads

Methanol/high reactivity fuel (HRF) dual fuel combustion cannot further extend methanol energy ratio (MER) at medium and low loads. Polyoxymethylene dimethyl ether (PODE) as a biofuel with high cetane number is well suited for HRF. This paper explored the effect of spark ignition (SI) on energy conversion and MER extension for methanol/PODE under medium and low loads. The results show that SI triggers the exothermic processes of SI and dual fuel spark-assisted compression ignition (D-SACI). SI raised MER from 30 %, 40 %, 46 % to 40 %, 60 %, 90 % for brake mean effective pressure (BMEP) of 0.2, 0.4, 0.6 MPa, respectively. SI and D-SACI combustion can partially or completely replace premixed compression ignition (CI). Diffusion combustion and one or more exothermic processes of SI, D-SACI and premixed CI make up two-stage or three-stage exotherm. D-SACI is easily triggered when spark timing approaches PODE injection timing, otherwise, SI exotherm is easily triggered; at BMEP of 0.6 MPa, the exothermic energy of premixed CI is gradually converted into the exothermic energy of D-SACI and SI as MER increases. By optimizing, maximum brake thermal efficiency for BMEP of 0.4 and 0.6 MPa are 37.75 % and 42.82 %, respectively, corresponding to the MER of 50 % and 80 %, respectively.

DFT investigation for the mechanisms of γ-butyrolactones from styrene and acrylic acid, catalyzed by NMA*BF4 and PhSSPh

The reaction mechanisms of γ-butyrolactones through electrophilic addition reactions between styrene and acrylic acid, catalyzed by the 9-mesityl-10-methylacridinium ion (NMA*BF4) and diphenyl disulfide (PhSSPh) under 450 nm visible-light, were investigated by employing M06-2X-D3/ma-def2SVP method and basis set. In this study, the SMD model was taken to simulate the solvent effect of dichloromethane. The photocatalyst NMA absorbs the energy of photons and becomes an excited state, capturing an electron from styrene; this leads to an electrophilic addition reaction happened between the obtained styrene cationic radical and acrylic acid anion (or acrylic acid molecule); finally, an intramolecular ring-closure process and H-shift process result in the formation of the final product. The computational results point out that the electrophilic reaction is an exothermic process; and the optimal path for ring-closure reaction and H-shift reaction has Gibbs free energy barriers of 11.10 and 9.94 kcal/mol, respectively. In particular, the recycling of the photo-catalyst NMA and cocatalyst PhSSPh has also been discussed. The ρhole and ρele can reveal the charge transfer process during the photo-catalytic reaction. Results would provide valuable insights into these types of interaction and related processes.

Revealing the quasi-solid-state electrolyte role on the thermal runaway behavior of lithium metal battery

Replacing flammable non-aqueous organic liquid electrolyte (LE) with high thermal stability solid-state electrolyte (SSE) is considered to overcome the safety issues in lithium metal batteries (LMBs). However, both inorganic solid-state batteries (SSBs) with high mechanical strength and thermal stability, as well as flexible polymer-based SSBs, are not proven to be inherently safe yet. Currently, the reliability of SSBs still require continuous scientific verification. In this work, quasi-solid-state electrolyte (QSE) with practical application prospects was prepared through in-situ polymerization method. The effects of QSE and LE on the thermal runaway behavior of LMBs were systematically compared from four levels: electrolyte, electrolyte/electrode interface, coin cells, and pouch cells. The results showed that higher thermal stability of QSE was conducive for improving the reliability of quasi-solid-state batteries (QSBs) under different abused conditions. The stable and dense solid electrolyte interface (SEI) in QSB could not only inhibit the severe side-reactions of LMBs during cycling at elevated temperature, but also enhance the decomposition temperature with dead lithium. QSE's lower reaction activity towards Li reduced the exothermic reaction inside the battery had been proven to increase the self-exothermic onset temperature and thermal runaway trigger temperature of LMBs, which promoted the safety performance of LMBs. Thus, this study revealed the thermal runaway mechanism of QSE in LMBs, and provided a theoretical guideline for safe QSBs design.

Preparation and Hydration Properties of Sodium Silicate-Activated Municipal Solid Waste Incineration Bottom Ash Composite Ground-Granulated Blast Furnace Slag Cementitious Materials.

The production of municipal solid waste incineration bottom ash (MSWIBA) is substantial and has the potential to replace cement, despite challenges such as complex composition, uneven particle size distribution, and low reactivity. This paper employs sodium silicate activation of MSWIBA composite Ground-granulated Blast Furnace slag (GGBS) to improve the reactivity in preparing composite cementitious materials. It explores the hydration performance of the composite cementitious materials using isothermal calorimetric analysis, Fourier-transform infrared (FTIR) spectroscopy, XRD physical diffraction analysis, and SEM tests. SEM tests were used to explore the hydration properties of the composite gelling. The results show that with an increase in MSWIBA doping, the porosity between the materials increased, the degree of hydration decreased, and the compressive strength decreased. When the sodium silicate concentration increased from 25% to 35%, excessive alkaline material occurred, impacting the alkaline effect. This inhibited particle hydration, leading to a decrease in the degree of hydration and, consequently, the compressive strength. The exothermic process of hydration can be divided into five main stages; quartz and calcite did not fully participate in the hydration reaction, while aluminum did. The vibrational peaks of Si-O-Ti (T = Si and Al) were present in the material. The vibrational peaks of XRD, FTIR, and SEM all indicate the presence of alumosilicate network structures in the hydration products, mainly N-A-S-H and C-A-S-H gels.

Adsorption of the rare earth elements cerium, lanthanum, and neodymium onto ZSM-5 zeolite: A statistical physics approach

The recovery of rare earth elements (REE) is essential to meet the growing demand for these resources and promote the reuse of available resources. This study investigated the potential of ZSM-5 zeolite in the recovery of trivalent ions of cerium, lanthanum and neodymium under conditions of pH 6 and temperatures between 298 and 328 K. REE equilibrium isotherms were analyzed using five statistical physics models. The results indicate that removing all REE occurs predominantly in monolayers, as these models showed better prediction performance (coefficient of determination > 0.97 and mean squared error < 18.0). The best model determined that lanthanum and neodymium have one adsorption energy, while cerium has two adsorption energies involved in the process. The predominant functional groups are those containing silicon. Increasing temperature causes an increase in the number of REE ions captured per functional group, which reduces the adsorption space available on the surface. The model parameters indicate that the adsorption of these ions implies a multi-ionic mechanism (number of ions adsorbed per site greater than 1) and is an exothermic process. Based on the calculated adsorption capacities at saturation, the order of preference in adsorption can be established: neodymium > cerium > lanthanum. The adsorption energies indicate that the process occurred mainly due to physical forces since all energy values are below 40 kJ mol−1. The study’s results led to the proposal of a mechanism for the adsorption of REE on ZSM-5 zeolite, which highlights the predominance of electrostatic interactions and complex formation, which result in the formation of a monolayer on the adsorbent’s surface.

Low‐Temperature Epitaxy of Perovskite WO3 Thin Films under Atmospheric Conditions

As Si electronics hits fundamental performance limits, oxide integration emerges as a solution to augment the next generation of electronic and optical devices. Specifically, oxide perovskites provide diverse functionalities with a potential to create, tune, and combine emergent phenomena at interfaces. High‐level crystalline order is needed to realize these functionalities, often achieved through epitaxy. However, large‐scale implementation in consumer devices faces challenges due to the need for high‐temperature deposition in complex vacuum systems. Herein, this challenge is addressed using atmospheric pressure spatial chemical vapor deposition, a thin‐film fabrication technique that can rapidly produce uniform films at sub‐400 °C temperatures under atmospheric conditions over ≈cm2 areas. Thus, the deposition of epitaxial perovskite tungsten trioxide, WO3, thin films is demonstrated at a rate of 5 nm min−2 on single‐crystal substrates at 350 °C in open‐air conditions enabling a high‐throughput process. The resulting films exhibit crystallographic and electronic properties comparable to vacuum‐based growth above 500 °C. The high‐quality epitaxy is attributed to the energetics of the exothermic decomposition reaction of the W[CO]6 precursors combined with the stabilization of a hot zone near the substrate surface. From this work, the way can be paved for low‐temperature atmospheric‐pressure epitaxy of a wide range of other perovskite thin films.

Numerical investigation of reaction driven magneto-convective flow of Sisko fluid

In many geothermal engineering applications involving exothermic chemical reactions, gravity, and buoyancy forces significantly enhance yields, especially during the thermal and catalytic cracking involving high temperature and concentration differences of some heavy hydrocarbons. This investigation deals with the numerical examination of nonlinear double convective flow, heat, and mass transfer of reactive Sisko fluid based on chemical kinetics theory for fluid flowing through a nondeformable porous medium. The governing equations are formulated and made dimensionless, and numerical results are obtained by applying the Spectral Chebyshev Collocation Method and validated with the Shooting-RK4 method. The effects of several parameters on the flow, heat, mass transfer, and thermal stability of the combustible fluid are documented in graphical and tabular forms, with detailed explanations. The computation reveals that buoyancy forces and Frank–Kamenetskii parameters encourage a velocity and temperature distribution rise. This analysis gives an insight into friction reduction in many heat and mass transfer thermophysical systems such as automobiles, power generations, and lots more.