Activation Energy Of Viscous Flow Research Articles

Melting, viscosity and structure of lithium-free CaO-SiO2 based melt: Substituting Li2O with Na2O and B2O3

Lithiation-free mold fluxes with excellent performances are urgently needed to be developed, due to the desire for Li2CO3 (Li2O) from the lithium battery industry. So, in this study, the melting, viscosity and structure of the CaO-SiO2 based flux melt, with the aim to replace Li2O by Na2O and B2O3, were investigated. Results show that the melting temperature decreased from 1258.1-1651.9 K to 1245.3–1632.5 K, and the viscosity at 1573 K decreased from 0.310 to 0.098 Pa s, when the ratio of Li2O/(Na2O + B2O3) decreased from 0.38 to 0.00. Meanwhile, the break temperature reduced from 1475.3 to 1451.4 K, and the activation energy of viscous flow also decreased from 181.44 to 55.39 kJ/mol, with the decease of Li2O/(Na2O + B2O3) ratio. Melt structure analyses indicate that the simpler structural units, such as Q0(Si), Q1(Si), [AlO4]5- tetrahedral and B-O- in [BO3] increased, while the more complex structural units, like Q2(Si), Q3(Si), bending vibration of Si-O-Al and boron ring in borate reduced, when Li2O was replaced by Na2O and B2O3. These changes suggest that the DOP of the flux melt was reduced and the melt structure was simplified during the lithiation-free process.

Investigation on Polyether Sulfone Toughening Epoxy Vitrimer: Curing and Dynamic Properties.

Diglycidyl ether of bisphenol A crosslinking with glutaric anhydride is used to form the conventional "covalent adaptive network", polyether sulfone (PES) by coiling and aggregating on the adaptive network is used to significantly increase the uncured resin viscosity for improving the processability of epoxy resin, but inevitably affecting the curing reaction and dynamic transesterification reaction. This study investigates the crucial roles of PES in curing dynamics and stress relaxation behavior. The results indicate that although PES does not directly participate in the crosslinking reaction of polyester-based epoxy vitrimers. Moreover, the isothermal curing studies reveal that the addition of PES can greatly bring forward the reaction rate peak from conversion α = 0.6 to α = 0.2, meaning that the curing mechanism transfers from chemical control to diffusion control. Dynamic property analysis shows that the addition of PES significantly accelerates stress relaxation, especially at lower temperatures, leading to low viscous flow activation energy Eτ and relatively insensitive stress relaxation behavior to temperature. Introducing PES into vitrimer resin greatly improves crosslinking density (2.31×10⁴molm- 3), enhancing glass transition temperature (82.68°C), tensile strength (68.66MPa), and fracture toughness (6.25%). Additionally, the modified vitrimer resin exhibits satisfying shape memory performance and reprocessing capability.

Investigation of P2O5 on the Break Temperature and Phase Composition of Slag from the Double Slag Converter Steelmaking Process

Herein, the influence of P2O5 on the break temperature and phase composition of slag from the double slag converter steelmaking process is investigated comprehensively. The composition and micromorphology of crystallized phase are analyzed by X‐Ray diffractometer and scanning electron microscope equipped with energy dispersive spectrometer. The results reveal that the break temperature of slag increases owing to an increase of P2O5 content. When the P2O5 content is 2%, the break temperature is 1198 °C, and it increases to 1209 °C for the slag with 4% P2O5. With the increase of P2O5 content from 2% to 8%, the activation energy for viscous flow shows an upward trend. The crystallized phase at the same temperature with different P2O5 contents remains nearly unchanged, but the diffraction peak intensity is different. When the P2O5 content remains constant, a decrease in temperature results in significant changes in the micromorphology of crystallized phases. The present results improve the knowledge about the P‐rich slag, and are also significant in optimizing the double slag converter steelmaking process.

High-temperature structural drivers immobilizing alkaline substances in red mud-derived mineral wool

Smelting and fiberization of red mud (RM) is an attractive approach for rapid recovery of metal resources, production of mineral wool, and immobilization of hazardous alkalis. However, an enormous challenge remains in understanding alkali immobilization behavior in mineral wool over a broad A/S (Al2O3 to SiO2 mass ratio) range. Here we addressed the challenge through molecular dynamics, thermodynamic and experimental analyses. Increasing A/S ratio caused an increasing degree of structural order and the remarkable micro-phase separation occurred at A/S > 0.9. The role of Na+ and Ca2+ changed from the network-modifying cations to the charge-compensating cations. Melt viscosity decreased and then increased significantly with an intensified temperature sensitivity, identified by the increasing viscous flow activation energy from 211.5 to 377.03 kJ/mol in the temperature region from 1500 to 1570 °C. The transformation of thermodynamic properties (real mixed/excess molar Gibbs free energies, and entropy increment) corresponded to the structural changes. Thermal, mechanical and leaching tests confirmed the negative effect of this structural transformation on alkali immobilization. The A/S ratios controlled below 0.9 were proposed for environmental benefits and product stability. The investigation of immobilization mechanism provides valuable information for tuning the vitrification chemistry and developing safe and green mineral wool from RM.

Effect of TiO2 on the structural properties and viscosity of CaO-SiO2-8.25 %MgO-15 %Al2O3-TiO2 slags

As a raw material for ironmaking, vanadium-bearing titanomagnetite will leads to an increase in the TiO2 content of blast-furnace slag and deteriorates the metallurgical properties of the slag. In this study, the effect of TiO2 content on the viscosity of CaO-SiO2–8.25 %MgO-15 %Al2O3-TiO2 slag system at fixed w(CaO)/w(SiO2) ratio of 1.2 was investigated, and Raman spectroscopy focusing on the relationship between the structure of high TiO2-bearing blast furnace slag and viscosity was performed. The findings showed that under the experimental condition, the viscosity of slag decreases with the increase of TiO2 content over a range of 20 to 35 %. The melting temperature of slag increases first and then decreases after w(TiO2) is higher than 30 %. The viscous-flow activation energy of slag decreases with the increase of TiO2 content, which has a concomitant variation corresponding with the results of the effect of TiO2 on viscosity. The analysis of Raman spectroscopy results reveals that the blast-furnace slag system is dominated by [SiO4]4- network structure. As the TiO2 content increases, more and more Ti4+ enters the silica-oxygen tetrahedral network structure, disrupting the Si-O-Si bond to form the [TiO4]4- structural unit and a small portion of the [TiO6]8- structural unit. The NBO/Si value of the Si4+ in the tetrahedron unit as an index for the degree of depolymerization of slags increased from 1.62 to 2.60 as the TiO2 content increased, the slag structure was gradually simplified and the slag viscosity was gradually decreased.

Eco-friendly material extrusion 3D printing for fabricating W-Ni-Fe lattices with improved compressive resistance

Tungsten (W) and its alloys are prevalently utilized in many special fields, such as the military and nuclear industry, owing to their exceptional attributes, including superior hardness, high density, and remarkable resistance to high temperatures. However, there are still challenges to achieve easy preparation of porous W alloys and uncover the secrets of their mechanical behavior. In this work, a porous lattice made from W93Ni4.9Fe2.1 with uniform microstructure was designed using enhanced material extrusion (MEX) 3D printing technology, offering exceptional formability while ensuring safety and environmental friendliness. The W93Ni4.9Fe2.1 lattice, fabricated at an extrusion temperature of 150 °C and infill percentage of 60 % exhibits the optimal geometry and homogeneous sintering shrinkage. The W93Ni4.9Fe2.1 lattice, fabricated at an extrusion temperature of 170 °C and infill percentage of 60 % shows the best compressive properties with the ultimate compressive strength of 1442 MPa and plastic strain of 19.8 %. The study of rheological properties of designed slurry determines the viscous flow activation energy of 1.64 kJ·mol−1 for the smooth extrusion of slurry, which is crucial for the formability of W93Ni4.9Fe2.1 lattice 3D printing. The ball milling treatment significantly improves the sinterability of W93Ni4.9Fe2.1 powder, confirming the effectiveness of mechanical alloying. This work presents a novel approach for fabricating complex structured porous W alloy with high-performance in a low-cost and environmentally friendly manner.

قياس ونمذجة الخواص الزائدة للمخاليط الثنائية والثلاثية من سيكلوهكسان و بيوتانول العادي 1-أوكتانول عند درجات حرارة مختلفة

This study aims to correlate the excess thermodynamic properties for new desirable mixtures. The density, refractive index, and viscosity of pure components and mixtures were measured over the entire composition range at atmospheric pressure and different temperatures. The results of measuring the density, viscosity, and refractive index were used to calculate the excess molar volumes, viscosity deviation, excess refractive index, and excess activation energies of viscous flow were reported for binary and ternary mixtures of cyclohexane, n-butanol, and 1-octanol at temperatures 20, 30, 40, and 50oC and over the whole mole fraction range. For all of the binary and ternary mixtures the computed excess molar volumes were correlated by applying the Redlich–Kister equation. and Prigogine–Flory–Patterson (PFP) theory. The correlations of excess molar volume, viscosity deviation, excess refractive index and excess activation energy to understand the effect of polar and nonpolar and temperature increase in the systems. Many works carried out to predict the excess thermodynamic properties, but the mixtures of this work have not been studied so far at such conditions. It is hoped that the present work will help in the availability of experimental data for some unknown mixtures to understand their behavior in the chemical processes, petrochemical industries and design processes. Keywords: Correlations, Excess properties, Density, Viscosity, cyclohexane and Alcohols, Binary and Ternary mixtures

Reprocessable and repairable carbon fiber reinforced vitrimer composites based on thermoreversible dynamic covalent bonding

The emergence of vitrimers breaks through the limitation of traditional carbon fiber reinforced thermoset composites (CFRP) caused by their permanent crosslinking molecular networks. Herein, the dynamic cross-linked network of vitrimer was synthesized from Bisphenol A diglycidyl ether (DGEBA) and glutaric anhydride (GA) under the catalysis of zinc acetylacetonate (Zn(acac)2), and the corresponding carbon fiber reinforced vitrimer composites (CF/Vx) were prepared via an impregnation and hot pressing process. The dynamic covalent adaptable networks (CANs) of vitrimer endow CF/Vx with stress relaxation and creep characteristics. By adjusting the catalyst content, the dynamic performance of CF/V0.05 can be optimized to achieve the highest viscous flow activation energy (60 kJ/mol) and the lowest characteristic relaxation time (1.0 × 10−3 s). The unique dynamic properties enable CF/Vx with reprocessability at high temperature. Typically, the flexural modulus of CF/V0.05 decreased from 87 ± 1.81 GPa at room temperature to 4.62 ± 0.28 GPa at 220 °C, which confirms the feasibility of thermoplastic forming of CF/V0.05 at high temperatures. Based on this, a CF/V0.05-based cap-shaped component was successfully manufactured through a thermoforming process. Additionally, the CF/V0.05 composites also exhibit repairability for interlaminar fractures. The optimal CF/V0.05 can achieve a repair efficiency of 128 % under the hot press conditions of 180 °C, 10 MPa and 1 h. Hence, the reprocessable and repairable CF/Vx composites hold enormous potential in the engineering field.

The Activation Energy Temperature Dependence for Viscous Flow of Chalcogenides

For some chalcogenide glasses, the temperature dependence of the activation energy E(T) of viscous flow in the glass transition region was calculated using the Williams–Landel–Ferry (WLF) equation. A method for determining the activation energy of viscous flow as a function of temperature is proposed using the Taylor expansion of the function E(T) using the example of chalcogenide glasses As-Se, Ge-Se, Sb-Ge-Se, P-Se, and AsSe-TlSe. The calculation results showed that the temperature dependence of the activation energy for the Ge-Se, As-Se, P-Se, AsSe-TlSe, and AsSe systems is satisfactorily described by a polynomial of the second degree, and for Sb-Ge-Se glass by a polynomial of the third degree. The purpose of this work is to compare the values of the coefficients obtained from the Taylor series expansion of E(T) with the characteristics of the E(T) versus (T − Tg) curves obtained directly from the experimental temperature dependence of viscosity. The nature of the dependence E(T) is briefly discussed.

Study of Activation Energy for Viscous Flow of Mixtures as a Measure of Dilution Efficiency for Heavy Oil-Diluent Systems

As the demand for crude oil continues to increase in response to the continued global needs for it, the development of unconventional crude oil reserves is the only way to sustain global supply. However, the excessively higher viscosity of heavy crude oil makes it less attractive for conventional pipeline transportation. Therefore, reducing the viscosity of heavy crude oil to meet crude oil transporting pipeline regulations is a necessity. This paper has assessed the dilution efficiency of well-known diluents in the petroleum industry, using different dilution ratios based on a thermodynamic approach involving activation energy and heat of vaporization determination. Based on selected dilution ratios, kinematic viscosities of binary and ternary systems of toluene and natural gas condensate as diluents, and Saudi Heavy crude oil as the base oil were measured, using anticipated field based temperatures reported in the literature, which facilitated the experimental approach. The study shows that although the ternary systems have the lowest activation energy for viscous flow and heat of vaporization in accordance with the thermal activation theory of viscous flow, natural gas condensate binary systems have the lowest cost of transportation per barrel of total fluid in the transporting pipeline. The study further shows that the binary systems for toluene and Saudi Heavy crude oil have higher activation energy for viscous flowed compared to the toluene systems.

Effect of fluorine on the viscosity and structure of non-reactive mold fluxes for high-Mn high-Al steel

The impact of varying F content from 4 wt% to 10 wt% on the structure and properties of non-reactive mold slag for high-Mn high-Al steel was investigated in this study. Employing a combination of techniques including a rotary viscometer, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy, the viscosity and structure of mold slag were analyzed. The findings revealed that increasing F content led to a gradual reduction in viscosity, activation energy for viscous flow, and the internal friction within the mold fluxes, consequently enhancing its fluidity. The Al–O–Al structure remained stable throughout the experimental range. The decrease in QAl2 content indicated a continuous depolymerization process, leading to the formation of free [Al2OF6] and [AlO6] structures as F content increased. At the same time, the replaced O2− ions were assimilated by [AlO4] tetrahedron, facilitating the formation [AlO6] octahedron. Consequently, the slag structure was simplified, resulting in a reduction in the degree of polymerization and viscosity.

Influence of Complex Plasticizer on Plasticizing Effects and Rheological Properties of Plasticized Poly(Vinyl Alcohol)

AbstractPoly(vinyl alcohol) (PVA) was modified using D‐mannitol (DM) and 1‐butyl‐3‐methylimidazole bromide (BMIMBr) as the complex plasticizer (DB), and PVA/DB composite was prepared. The plasticizing effect of DB on PVA was studied by Fourier transform infrared spectroscopy (FT‐IR), differntial scanning calorimetry (DSC), thermos gravimetric analysis (TGA) and melt flow indexer (MI). FT‐IR analysis indicated that Br− of BMIMBr and OH of DM could form H‐bonds with OH of PVA. With the increase of DB, the melt temperature (Tm2) and crystallization temperature (Tc1) of PVA/DB composite decreased, the initial thermal decomposition temperatures (Td), thermal processing window (ΔT) and MI values increased respectively. Based on above studies, the influence of DB content on rheological properties of PVA/DB composite was investigated by the capillary rheometer. The result displayed that apparent viscosity of PVA/DB composite decreased with increasing DB content, shear rate and measured temperature. The non‐Newtonian index (n) increased and structural viscosity index (Δη) decreased with the increase of measured temperature and DB. The viscous flow activation energy (Eη) decreased as the shear rate and DB content increased. When the measured temperature, DB content and shear rate were in the range of Tm2+30 −Tm2+35 °C, 40–50 wt% and 764.8–1504.9 s−1, respectively, the spinnability of PVA/DB composite was optimal, which will lay a theoretical foundation for the exploration of melt spinning process in the future.

Micelles and structural variation of the solution synergistically changing the viscosity of sodium aluminate solutions

Complicated organic behavior in the sodium aluminate solution limits the economical alumina production and improvement in alumina quality by Bayer process. Sodium gluconate (SG) or sodium stearate (SS) in sodium aluminate solution containing sodium oxalate (SO) changed the interfacial occurrence of anionic organics. The single anionic organic compounds or mixed organics initially decreased and then raised the viscosity of the sodium aluminate solution, and further increasing total organic carbon (TOC) remarkably increased the viscosity of the industrial sodium aluminate solution. Correspondingly, increasing concentration of anionic organic compound raised initially and then reduced diffusion coefficient. The minimum viscosity of the solution nearly occurred at the critical micelle concentration (CMC) of the anionic organic compound. Anionic organics also increased the viscous flow activation energy of sodium aluminate solutions. The disordered structure of sodium aluminate solution reduced the viscosity and increased the diffusion coefficient at low concentrations of organics less than CMC. Further increasing the concentration of organic compound more than CMC, micelles then contributed to the ordered structure of the sodium aluminate solution, increasing viscosity and reducing the diffusion coefficient of the sodium aluminate solution. Therefore, a large amount of micelles and the different solution structures synergistically changed the viscosity and diffusion coefficient of the sodium aluminate solution.

Features of extrusion of films from blends of LDPE and LLDPE of modern grades

The study of rheological and viscoelastic characteristics of modern grades of LLDPE and their mixtures with LDPE, intended for the production of fi lm products, as well as the evaluation of mechanical characteristics of films made of them have been carried out. As a result of studying the rheological properties of LLDPE and LDPE, it was found that polymer melts show behavior typical of pseudoplastic liquids. The flow index for all grades of LLDPE was 0.78–0.91, which indicates a narrow MWD of polymers; LDPE had a flow index of 0.56–0.57 and a higher activation energy for viscous flow than LLDPE.The viscoelastic properties of the polymers were assessed by the value of swelling coefficient (Ks) at two test temperatures. It is shown that the Ks of LDPE significantly exceeded that of all studied LLDPE grades at the same shear rates or shear stresses. The increase in temperature had an insignificant effect on the Ks value for both LDPE and LLDPE. It has been found that an increase in the content of LDPE in mixtures with LLDPE leads to an increase in Ks.The analysis of tensile properties of films obtained from the original polymers and their blends showed that the character of change in strength and elongation at break depends on the composition and type of LLDPE from different manufacturers. Films based on m-LLDPE of LUCENE brand had the maximum strength properties. The optimal content of LDPE in a mixture with LLDPE depends on the type of LLDPE and is no more than 10–20 wt.%.

Carboxymethyl hydroxypropyl guar gum physicochemical properties in dilute aqueous media

We investigate carboxymethyl hydroxypropyl guar gum (CMHPG) solution properties in water and NaCl, KCl, and CaCl2 aqueous solutions. The Huggins, Kraemer, and Rao models were applied by fitting specific and relative viscosity of CMHPG/water and CMHPG/salt/water to determine the intrinsic viscosity [η]. The Rao models yielded better results (R2 = 0.779–0.999) than Huggins and Kraemer equations. [η] decreased up to 84% in salt solution over the range 0.9–100 mM compared to water. Salt effects screened the CMHPG charged side groups chains leading to a compacted structure. In 0.9 mM NaCl(aq), the hydrodynamic coil radius (Rcoil) was 28% smaller and 45% smaller in 100 mM NaCl solution relative to water. Similar decreases were seen in KCl and CaCl2 solutions. KCl and CaCl2 were more effective than NaCl. CMHPG is salt-tolerant and shows comparatively less viscosity change than native guar gum, with modest reduced viscosity increases with CMHPG dilution at all salt concentrations. The electrostatic interactions were effective up to 100 mM salt. The activation energy of viscous flow for CMHPG solutions was computed and compared to measured xanthan gum and several literature values. These data show that the barrier to CMHPG flow is higher than for xanthan gum.

Viscous Flow Activation Energy and Short-Term Aging Resistance of SBS-Modified Asphalt Enhanced by PPA Oil-Grinding Activated MoS<sub>2</sub>

Viscous Flow Activation Energy and Short-Term Aging Resistance of SBS-Modified Asphalt Enhanced by PPA Oil-Grinding Activated MoS<sub>2</sub>

Физико-химические свойства растворов перхлората и тетрафторбората лития в смеси сульфолана и сернистого ангидрида

The temperature dependencies of physical and chemical properties (viscosity, density, electrical conductivity) and the melting temperature of 1M solutions of lithium salts (LiClO4 and LiBF4) in the mixture of sulfolane and sulfurous anhydride (∼1M) were studied. It was shown that the introduction of 1M (5% wt.) of sulfurous anhydride into 1M solutions of LiClO4 and LiBF4 in sulfolane increased the specific and corrected electrical conductivity, densities, activation energy of electrical conductivity and viscous flow of electrolyte solutions; and reduced viscosity and melting temperatures.

Physical properties of deep eutectic solvents with efficient nitrogen removal capability

The efficient separation of N-compounds from fuel oil is of great significance for environmental protection and the development of sustainable chemical processes. In this work, eight quaternary acidic deep eutectic solvents (DESs) were prepared for the removal of basic N-compounds (pyridine) from simulated oils. Initially, the density, viscosity, conductivity, surface tension and refractive index values of the DESs were determined at 293.15–333.15 K. Based on these data, physical quantities such as molecular volume, standard entropy, lattice energy, activation energy of viscous flow, activation energy of conductivity, surface entropy, surface energy, speed of sound, molar Gibbs free energy, molar polarizability, molar polarizability, and free molar volume have been calculated. The effects of temperature, alkyl chain length of hydrogen bond acceptors (HBAs)/hydrogen bond donors (HBDs), structure of HBDs, and HBAs anion on the physical properties of DESs were systematically investigated. The internal interaction and property change of DESs are further studied. Finally, pyridine was extracted from the simulated oil using the prepared DESs. DESs consisting of tetrabutylammonium bromide and lactic acid had the highest extraction capacity under the same conditions. The extraction efficiency was found to be strongly correlated with the alkyl chain length and the acidity of the HBDs. This work is expected to provide information on the removal of N-compounds from both theoretical and industrial perspectives.

The Activation Energy of Viscous Flow and Liquid–Liquid Structure Transition in Co-B Alloys

The temperature dependences of the kinematic viscosity during heating and cooling have been investigated in Co-B melts with a boron content of up to 30.8 at. A liquid–liquid structural transition was found, which is accompanied by an increase in the activation energy and cluster size, as well as a significant decrease in the density of the melt. The liquid–liquid structural transition was associated with the formation of clusters with a short-range order of Co23B6 in the intermediate temperature region. At low and high temperatures, clusters of the order of an atomic size are active participants in the viscous flow. It was shown that with an increase in the cluster size, the activation energy increases and the viscosity of melts decreases. The formation of large Co23B6 clusters during the cooling of melt with low boron content leads to undercooling and the appearance of the transition temperature region with high activation energy, although this region does not exist during the heating stage.

Effect of BaO/Al2O3 ratio and Li2O content on viscosity and crystallization of BaO–Al2O3–TiO2-based mold slags

In the current study, the influence of different BaO/Al2O3 ratios and Li2O contents on the viscosity, melting temperature, crystallization behavior and structure of BaO–Al2O3–TiO2-based mold slags was investigated through the measurement of the viscosity-temperature relationship, hemisphere point method, crystallization process and crystallization temperature, and the calculation of NBO/T and optical basicity. With the increase of the BaO/Al2O3 ratio from 0.60 to 1.67, the viscosity at 1573 K and the melting temperature of mold slags decreased from 0.3 to 0.05 Pa s, and 1261 K–1217 K, respectively, while those also slightly decreased from 0.15 Pa s to 0.11 Pa s, and 1244 K–1213 K with the Li2O content from 4 % to 6 %, respectively, which was related to the increase of fluxing reagent or oxygen ions released by basic oxide in slags. In current slags, precipitated phases mainly existed as LiTiO2 and BaTiO3, and the difference of the BaO/Al2O3 ratio and Li2O content resulted in the competitive precipitation of these phases. With the increase of BaO/Al2O3 ratio from 0.60 to 1.67, precipitated phases gradually changed from LiTiO2 to BaTiO3, and the initial crystallization temperature had the tendency to decrease and increase. On the contrary, the precipitated phase gradually changed from BaTiO3 to LiTiO2, and the initial crystallization temperature as well as the break temperature decreased with the Li2O from 4 % to 8 %. The parameter NBO/T and optical basicity of molten slags increased with the increase of BaO/Al2O3 and Li2O content, and the polymerization degree of the melt decreased, resulting in the decrease of the activation energy of viscous flow and the viscosity. Hence, the increase of the BaO/Al2O3 ratio and Li2O content within limits could lower the viscosity, melting temperature, break temperature and crystallization ability of mold slags, and then improve the lubrication of the slag on solidified shell.