Defined Temperature Range Research Articles

Correlation Effect on Different Temperature-Humidity Range of Highly Thermal GNP/AG/ SA Conductive Ink

The study evaluates how the resistivity and properties of the material change in response to environmental factors such as temperature and humidity, and how these changes impact its performance in various applications. In order to develop a highly thermal graphene hybridization conductive ink, a new formulation of conductive ink was formulated using graphene nanoplatelet (GNP), silver flake (Ag), and silver acetate (SA) as conductive fillers mixed with organic solvents. The batch of chemicals was converted into a powder by undergoing sonication and stirring to create a powdery state. The powder was then treated with organic solvents, specifically 1-butanol and terpineol, and mixed using a thinky mixer to form a paste. The GNP/Ag/SA hybrid conductive ink paste was then printed on copper substrates using a mesh stencil and was cured at 250°C for 1 hour. Cyclic testing had been conducted using a cyclic bending test machine and a cyclic torsion test machine in a heat chamber with different temperature-humidity. The new formulation then was characterized base on the electrical and mechanical behaviour. After the torsion and bending tests, the GNP/Ag/SA hybrid conductive ink formulation reliability was evaluated. GNP/Ag/SA hybrid conductive ink room temperature baseline and GNP/Ag/SA hybrid conductive ink after given different temperature-humidity were compared in terms of electrical and mechanical properties. Both cyclic bending and torsion testing results showed an increasing value of resistance and resistivity with every progress of bending and torsion cycle, which displays a clear trend. The results indicate that the average resistance values at all sample points either stay constant or decrease with the increasing temperature. This observation suggests that the ink's electrical conductivity remains rather stable as the temperature increases. Thus, even with rising temperatures, the ink's electrical conductivity remains stable, indicating the ink's capacity to preserve its integrity and structural qualities within a defined temperature range. Future research should focus on improving the adhesion, stability and reliability of stretchable conductive inks under various temperature and humidity conditions.

Automatization of theoretical kinetic data generation for tabulated TS models building - Part 1: Application to 1,3-H-shift reactions

Estimation of kinetic parameters is a key aspect of chemical combustion modeling and several approaches were developed to approximate unknown data. In this work, a code in Python was developed to build tables of transition state (TS) models automatically for intramolecular H-shift reactions in alkyl radicals. The code generates the kinetic rules for all the possible combinations of methyl-substituted reactions based on the structures of the minimal, non-substituted, reactant, TS, and product. The code is able to create and differentiate multiple transition state configurations, considering the axial and equatorial positions for the cyclic substituents and including all the possible pathways for the reactions, which is shown to be an important feature in performing accurate automatic kinetic calculations. Each structure is automatically submitted to geometry optimization and electronic energy calculations, as well as the relaxed scans of the torsional modes identified by the code. From the results of electronic calculations, the rate constants for each pathway are obtained automatically by the application of the transition state theory with tunneling corrections, in a defined temperature range. The kinetic coefficients, as well as the modified Arrhenius parameters, are then assembled and organized to create a final table that connects the kinetic data with TS structure characteristics. These tables can be directly applied as a kinetic data source for reaction mechanism development. The ability of the code to generate reliable rate constants was tested for 1,3-H-shift reactions and the results were compared with theoretical data manually produced, and showed a good agreement. In particular, the code was able to create all the transition state configurations, with an exhaustive description of all possible reaction pathways, using a rigorous and systematic counting based on symmetry, stereocenters, and diastereomers. The proposed method leads to more accurate results on these aspects, compared to repetitive hand calculations of dozens of rate constants.

Effect of fluxes in submerged arc welding for steel: A review

In submerged arc welding, fluxes have a multifaceted function throughout the process of welding. Apart from influencing bead geometry and shielding the weld pool, these fluxes also experience deliberate melting within a defined temperature range. These fluxes serve to refine the weld metal and engage in reactions between slag and metal before ultimately being eliminated as slag. The cost of welding flux constitutes a significant portion of the expenses in the submerged arc welding (SAW) process. As time has passed, the pursuit of improved compositions for welding flux, ones that offer enhanced mechanical properties and productivity while remaining economically efficient, has garnered substantial attention from researchers. This review paper focuses on the collective research efforts of various scholars within the realm of welding flux advancement. The effect of various fluxes on the structural properties of the steel has been briefly revised in this paper.

The influence of the temperature on the hydration behavior and hardening process of PCC

AbstractPCC exhibit improved durability, chemical resistance and adhesion strength compared to unmodified variants. Commonly, the modifiers consist of thermoplastics. Despite the distinct temperature‐dependent behavior of these polymers, the properties of PCC were barely investigated within different temperatures. To make statements about the effect of different temperatures on the hardening process and therewith on the load bearing and deformation behavior of PCC, the properties of the materials have to be experimentally assessed at a defined temperature range. Accordingly, the degree of hydration, the structure development, the compressive and flexural strength as well as dynamic and static modulus of elasticity of different PCC were characterized while the samples were exposed to service temperatures of ‐20 °C, 20 °C, and 60 °C. After the specimens were thermally conditioned, the samples were tested in the proposed temperature scope. The results reveal influential changes in all tested attributes for the PCC within the applied service temperature range compared to a reference. This knowledge is essential to further investigate the temperature impact on the material and develop appropriate prediction models for the application of PCC and the integration in guidelines.

Thermodynamics Study for Selective Leaching of Copper and Zinc from Complex Secondary Raw Materials Using Oxidative Sulfuric Acid Leaching

This study focuses on evaluating the optimal process conditions for selectively leaching copper and zinc from complex secondary raw materials using the oxidative sulfuric acid leaching process. The research includes both physical and chemical characterization of the materials and a comprehensive thermodynamic analysis to assess the thermodynamic properties and behaviors of the system under investigation. The physical characterization involves determining parameters such as bulk density, moisture content, and granulometric composition of the samples. Elemental composition analysis is performed using X-ray fluorescence spectrometry (XRF) and energy dispersion spectroscopy (EDX), while the phase composition is determined through X-ray diffraction (XRD) analysis. Additionally, the materials' morphology is examined using scanning electron microscopy (SEM). Fraction diagrams are created using Hydra/Medusa software to assess the phase distributions of zinc and copper during the leaching process. The stability of the metals and potential chemical reactions within a defined temperature range is analyzed using Eh-pH diagrams with the HSC 9 Chemistry Software. Based on the thermodynamic analysis conducted, it is determined that effective leaching of copper and zinc from the complex secondary raw materials is achievable. Furthermore, the results indicate that the leaching process is relatively insensitive to temperature variations. The optimization of the leaching process should primarily focus on achieving optimized consumption of the oxidizing agent.

Experimental studies of a granulator with a cooling system using a standard matrix for the development of waste-free industries

The use of renewable resources and the development of waste-free industries are becoming more and more urgent as the environmental crisis is growing and energy resources are decreasing. Wood processing is one of these areas. Dumps of forest waste can cause fires. The use of wood processing waste as a fuel is impractical due to their low calorific heat value. Therefore, such waste is first subjected to special treatment to obtain fuel briquettes or pellets using special lines, the basis of which is a granulator. However, the granulation process takes place within a strictly defined temperature range. Therefore, one of the main problems to be solved is the stabilization of the heating of the granulator matrix. To solve this problem, we have developed a scheme of a cooled matrix granulator. We carried out a series of experiments in order to determine the efficiency of the proposed granulator. The aim of the first stage of our research was to study the working process of a granulator with a cooling system using a standard matrix. We have come to the conclusion that granules of the required quality in a granulator with a standard matrix are not obtained in all operating modes.

Purity determination and uncertainty estimation of natural products sourcing chemical reference substances by high-performance liquid chromatography and differential scanning calorimetry

Natural products sourcing chemical reference substances (NPSCRSs) are widely used in the analysis industry to determine the content and quality of food and drug products. Chromatographic techniques have been traditionally used to determine the purity of chemical reference substances (CRSs). However, the uncertainty values of NPSCRSs purity are rarely measured due to the chemical complexity of natural products and the diversity of instrument influencing factors. Recently, differential scanning calorimetry (DSC) technique has been proved to be able to detect the purity of CRSs, but its adaptability for NPSCRSs is rarely researched. Herein, a HPLC-DSC combined method was developed for the purity calibration and uncertainty measurement of 20 NPSCRS samples. As a result, the value of “purity ± uncertainty” was suggested to represent the quantitative result for purity measurement of NPSCRSs. Among four influence factors of HPLC analysis, the influence of peak area was first proposed as the source of uncertainty, and the uncertainty caused by the wavelength was simplified to a five wavelength-based method. As for DSC method using for purity determination of NPSCRSs, it could be used as an alternative and complementary method to verify the purity of a NPSCRS that is more than 98% because of its advantage of practicality, speed, reproducibility, no corresponding reference standard requirement, and no sample preparation is required. Note that, DSC method is not appropriate if the compound lacks standard melting peak, decomposes in the defined temperature range, or exhibits other thermal event (s) which interfere with the melting point of the compound.

Experimental determination of thermodynamic properties of terpene and aromatic ketones by gas chromatography

The terpene and aromatic ketones are among oxygenated compounds present in essential oils (Eos). They are substances of great importance to the chemical, pharmaceutical, and the food industries. Because of their applications in these industries, it is extremely necessary to know their thermodynamic properties and to obtain reliable data of these properties. This work aims to determinate experimentally the enthalpy of vaporization (∆Hvap) and normal boiling temperature (Tnb) of some terpene and aromatic ketones and other oxygenated compounds present in essential oils by the gas chromatography technique (GC). The additional goal is to evaluate three group contribution models developed to estimate enthalpies of vaporization. The experimental determination of thermodynamic data using GC involves the use of the chromatographic retention index in combination with Kirchhoff-Rankin type equations. Gas chromatography experiments were carried out within a defined temperature range consistent with the nature of the compounds studied. In all, 11 compounds were evaluated. The ∆Hvap data were determined at 298.15 K. The results obtained agreed with those found in the literature, showing small relative deviations (RD), demonstrating that the CG technique can be a good tool for obtaining the thermodynamic properties studied. In addition, unpublished data of ∆Hvap at 298.15 K and Tnb for the compounds bicyclo[2,2,2]octan-2,5-dione, methyl-jasmonate and 4-(4-hydroxyphenyl)-2-butanone are reported.

Structure, electrochemical impedance and Raman spectroscopy of lithium-niobium-titanium-oxide ceramics for LTCC technology

Resultsof Electrochemical Impedance Spectroscopy (EIS) are reported for lithium-niobium-titanium-oxide (LNTO) ceramics synthesized by a solid-state reaction method with two functional additives (MoO3 or ZnO) in the temperature range 323 K - 573 K and frequencies between 10−1 Hz and 107 Hz. Scanning electron microscopy (SEM) reveals a textured morphology of rod and plate-like particles that are typical for M-phase LNTO materials, while X-ray diffraction (XRD) analysis confirms the formation of an M-phase member compound with an approximate structure of Li7Nb3Ti5O21. Complex impedance analysis indicates that its overall electrical resistivity behavior depends mostly on the grain boundary processes. EIS analysis shows a negative temperature coefficient of resistance behavior (NTCR) in a defined temperature range in two LNTOs and thermal activation of the conduction mechanisms. The low dielectric constants of 5.5 and 12.1 at 1 MHz were found for the first and second LNTOs, respectively. Complimentary Raman spectroscopic measurements, despite very large crystallographic unit cell of LNTO, reveal only a small number of lines, which is the consequence of a “molecular” nature of materials.

Chemical Looping Steam Methane Reforming via Ni‐ferrite Supported on Cerium and Zirconium Oxides

AbstractPure hydrogen was produced by means of chemical looping steam methane reforming with novel oxygen carriers. Ni‐ferrite, Ni‐ferrite‐ZrO2, and Ni‐ferrite‐CeO2 were synthesized as oxygen carriers and characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller (BET) method, scanning electron microscopy (SEM), dynamic light scattering (DLS), and hydrogen temperature‐programmed reduction (H2‐TPR). The performances of the as‐synthesized oxygen carriers in the cyclic oxidation‐reduction were investigated in the packed‐bed microreactor at a defined temperature range and under atmospheric pressure. Ni0.39Fe2.61O4‐ZrO2 exhibited the best performance and maximum methane conversion among the other oxygen carriers. In addition, high selectivities for H2 and CO were reached.

Polyacrylonitrile/α‐Fe2O3 Hybrid Photocatalytic Composite Adsorbents for Enhanced Dye Removal

AbstractThe potential of a novel α‐Fe2O3/polyacrylonitrile (PAN) hybrid composite adsorbent to eliminate methylene blue (MB) from aqueous solution was evaluated. PAN was selected as the base composite. The presence of α‐Fe2O3 as nanophotocatalyst on the surface of PAN introduced an efficient photocatalytic hybrid composite adsorbent for degrading MB. Effects of α‐Fe2O3 nanopowder loading, pH, temperature, MB initial concentration, solar light, and contact time were investigated. Langmuir, Freundlich, and Temkin isotherms were applied to analyze the adsorption behavior. The Freundlich equation provided the best correlation with experimental data. Pseudo‐first‐order, pseudo‐second‐order, and intraparticle models were employed. Thermodynamic studies indicated an endotherm and spontaneous adsorption process in a defined temperature range.

Effect of phase change material using in building thermal comfort applications through several climate conditions.

Nowadays, buildings sector contributes to climate change by consuming a considerable amount of energy to afford thermal comfort for occupants. Passive cooling techniques are a promising solution to increase the thermal inertia of building envelopes, and reduce temperature fluctuations. The phase change materials, known as PCM, can be efficiently employed to this purpose, because of their high energy storage density. Among the various existing solutions, the present study is dedicated to solid-liquid phase change materials. Temperature evolution (according to their defined temperature range) induces the chemical change of the material and its state. For building applications, the chemical transition can be accomplished from liquid to solid (solidification) and from solid to liquid (melting). In fact, this paper presents a comparative thermal analysis of several test rooms with and without phase change materials embedded in a composite wallboard in different climates. The used PCM consist in a flexible sheet of 5 mm thickness (Energain, manufactured by the company DuPont de Nemours). The main properties of such a commercial solution have been delivered by the manufacturer and from analyses. The room model was validated using laboratory instrumentations and measurements of a test room in four cities: Lyon; Reading and Casablanca. Results indicate that this phase change material board can absorb heat gains and also reduce the indoor air temperature fluctuations during daytime. The aim of the study is to show the benefits of this layer with phase change material and compare it in different climatic zones.

Fabrication and characterization of phase change material-SiO2 nanocomposite for thermal energy storage in buildings

Abstract Phase change materials (PCMs), which can absorb or release large latent heat over a defined temperature range while the phase transition occurs, have achieved huge attention due to the environmental concerns and energy crisis. In recent years, phase change material nanocomposites are extensively used in thermal energy storage and energy management. Here, a shape-stabilised PCM nanocomposite, consisting n-hetadecane as a PCM and SiO2 nanoparticles as a supportive material was successfully prepared using an impregnation method with different mass fraction of PCM. The formation of n-heptadecane-SiO2 nanocomposite was approved using X-ray diffraction, FTIR spectroscopy, and SEM studies. The melting and freezing latent heats of the nanocomposite reached 123.8 and 120.9 J/g, respectively, and the mass loading percentage of n-hetadecane in the nanocomposite which was estimated using DSC was about 54.6 wt.%. The resulting nanocomposite possessed excellent thermal cycling reliability and its thermal conductivity was also improved compared to pure n-heptadecane. Additionally, Gypsum composite board containing n-hetadecane-SiO2 nanocomposite showed acceptable temperature control performance compared to ordinary gypsum board and hence, the obtained nanocomposite can be suitable for storing thermal energy and indoor temperature regulation in the buildings.

Thermomechanical behavior of shape memory alloy metal matrix composite actuator manufactured by composite extrusion

Continuous composite extrusion represents a new possibility for the manufacturing of shape memory alloy metal matrix composites (SMA-MMC). During the process SMA wires are embedded into aluminum or magnesium profiles by means of modified porthole dies. Due to the high flexibility regarding the profile geometry, the materials as well as number, thickness and position of the SMA elements, the process can be used for the generation of a profile integrated bending function. The bending function of the actuator profile depends on the temperature and is thermally activated. The parameters influencing the behavior of the manufactured composited actuators are experimentally investigated. It is found that the radius of curvature mainly depends on the recovery stress and the eccentric position of the SMA wire as well as on the bending stiffness of the actuator profile. The bending mechanism and the experimental results are described by the use of an analytical model as well as a finite element analysis. Based on the results the analytical model is used for the targeted design of a profile with multiple embedded NiTi wires, which is able to perform a repeatable, pure elastic deflection within a defined temperature range between room temperature and 75 °C.

Enthalpy-temperature plots to compare calorimetric measurements of phase change materials at different sample scales

Phase change materials (PCM) can provide high thermal energy storage capacities in narrow temperature ranges around their phase change temperature. The expectable maximum storage capacity of a PCM in a defined temperature range is equal to the enthalpy change in that range and can be determined via calorimetric measurements such as differential scanning calorimetry (DSC) or T-History calorimetry. T-History samples (∼15 ml) are about 1000 times larger than DSC samples (∼15 μl). Experiments in a pilot plant are performed to study the charging and discharging behaviour of even larger amounts of the PCM (∼150 l). The common practise is to investigate PCM at one scale, rarely at two scales. In this work, the characterisation was carried out at three scales (DSC, T-History, and pilot plant) for four PCM (RT58, bischofite, d-mannitol, and hydroquinone). Thereby, the question arises how the enthalpy changes measured at different scales and under different conditions can be compared. In literature, the melting enthalpy is usually assigned to a single temperature without indicating the temperature range considered for evaluation. In very few instances, the enthalpy change within a defined temperature range is stated. In both cases, results measured under different conditions are difficult to compare. In this work, it is demonstrated that enthalpy-temperature plots facilitate the comparison and interpretation of measurements obtained under different experimental methods at different sample scales.

Automated in Situ Measurement of Gas Solubility in Liquids with a Simple Tube-in-Tube Reactor.

Data on the solubilities of gases in liquids are foundational for assessing a variety of multiphase separations and gas-liquid reactions. Taking advantage of the tube-in-tube reactor design built with semipermeable Teflon AF-2400 tubes, liquids can be rapidly saturated without direct contacting of gas and liquid. The gas solubility can be determined by performing steady-state flux balances of both the gas and liquid flowing into the reactor system. Using this type of reactor, a fully automated strategy has been developed for the rapid in situ measurement of gas solubilities in liquids. The developed strategy enables precise gas solubility measurements within 2-5 min compared with 4-5 h using conventional methods. This technique can be extended to the discrete multipoint steady-state and continuous ramped-multipoint data acquisition methods. The accuracy of this method has been validated against several gas-liquid systems, showing less than 2% deviation from known values. Finally, this strategy has been extended to measure the temperature dependence of gas solubilities in situ and to estimate the local enthalpy of dissolution across a defined temperature range.

Solubility Studies of Sodium Azide in Liquid Ammonia by In Situ Ultrasonic Velocity Measurement

AbstractUltrasonic velocity measurement data has been established as a simple and convenient tool to determine different thermodynamic properties of liquids and solutions. Such measurements were carried out in situ to determine the solubility of NaN3 in liquid ammonia within a defined temperature range. Different mixtures of NaN3 in ammonia were prepared and the ultrasonic velocities of these mixtures were measured within this temperature range in order to compile calibration curves. Further, these calibration curves were used to calculate the solubility in a saturated solution.

Adsorption of C1–C4 Alcohols, C4–C5 Isoolefins, and their Corresponding Ethers over Amberlyst™35

AbstractAn experimental liquid‐ and gas‐phase adsorption study of C1–C4 alcohols, C4–C5 isoolefins, and the tert‐alkyl ethers obtained thereof over Amberlyst™35 is presented. Liquid‐phase adsorption experiments were performed in a batch adsorber and gas‐phase adsorption experiments were carried out in a packed‐bed adsorber in a defined temperature range. Adsorption entropy and enthalpy were determined from adsorption equilibrium constants of each tracer in both liquid and gas phase. Adsorption equilibrium constants of alcohols were found to be larger than those of isoolefins and ethers. The moment technique was used to estimate micro‐ and macropore effective diffusion coefficients of the involved species.

Innovative Carbon Dioxide‐Capturing Organic Solvent: Reaction Mechanism and Kinetics

AbstractThe reaction rates of CO2 with an innovative CO2‐capturing organic solvent (CO2COS), consisting of blends of 2‐tert‐butyl‐1,1,3,3‐tetramethylguanidine (BTMG) and 1‐propanol, were obtained as function of BTMG concentration and temperature. A stopped‐flow apparatus with conductivity detection was used. The reaction was modeled by means of a modified termolecular reaction mechanism which resulted in a second‐order rate constant, and activation energies were calculated for a defined temperature range. Quantum chemical calculations at the B3LYP/6‐31G(d) level also produced the activation energy of this reaction system which strongly supports the experimental findings.

Inorganic fullerene-like IF-WS2/PVB nanocomposites of improved thermo-mechanical and tribological properties

The subject of this research is to explore the possibility of preparation of nanocomposite material of improved thermo-mechanical and tribological properties, using inorganic fullerene-like tungsten disulfide nanostructures (IF-WS2) as reinforcement in poly(vinyl butyral) (PVB). This paper also reports investigation of the effects of using different solvents in preparation of PVB/IF-WS2 nanocomposite on the thermo-mechanical behavior of the resulting material. PVB was dissolved in ethanol, isopropanol, n-butanol and ethyl acetate. IF-WS2 nanoparticles were added to these PVB solutions and dispersed by different deagglomeration techniques. Samples were dried and thin films were obtained. Their microstructure and the quality of IF-WS2 dispersion and deagglomeration in PVB matrix was analyzed by scanning electron microscope (SEM). The reinforcing effect of IF-WS2 is examined by determining hardness, reduced modulus of elasticity and coefficient of friction, by nanoindentation and nanoscratch test, in terms of the different solvents applied in preparation of the samples, mode of stirring and different contents of IF-WS2. The glass transition temperature (Tg) was determined for the prepared samples using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA). Storage modulus and mechanical loss factor were observed in a defined temperature range using DMA.