Papers by Keyword: Viscosity

Abstract: This study investigates Halloysite Nanotube (HNT) dispersibility in ethanol-water mixtures – 0% and 10% ethanol at 100, 300, and 500 ppm HNT concentrations. Overall, the study finds that changes in HNT concentration linearly affect the response variables and showed that the 10% ethanol solvent has a higher zeta potential, smaller particle size, higher viscosity, and settling velocity. The enlargement of HNT particles at 10% ethanol while keeping better stability than water solvent is unexpected and can open novel studies about the dispersion of HNT in this solvent system.

Abstract: Polymer flooding, an improved oil recovery technique, is a well-established method for improving oil production. Although numerous polymers have been suggested in the literature, identifying suitable ones for applications in high-temperature and high-salinity carbonate reservoirs remains a challenging task. The viscosity of polymer solutions depends on various parameters, including polymer concentration, temperature, and shear rate. Therefore, screening polymers for these demanding conditions necessitates meticulous experimental work. In this experimental study, polymer solutions' physical property—viscosity—was measured as a function of polymer concentration, temperature, and shear rate. Subsequently, the generated rheological data were used to develop empirical models capable of predicting the viscosity of polymer solutions under various conditions. An acceptable match was achieved between the experimental and model-predicted data. Furthermore, a validation was conducted for the empirical models, yielding a root mean square error of 1.75. These models will significantly reduce the number of experiments required for the screening process and prove valuable for optimization procedures.

Abstract: For a long time, rayon has been produced using dissolving pulp (DP). DP is typically made from wood or cotton, but it takes a long time to collect wood, and high-quality cotton must be imported from afar. Sansevieria trifasciata (ST) fiber, which contains more than 50% cellulose, offers potential as a raw material and a substitute for cotton and wood. It is simple to develop and grow. It can endure a wide range of light and temperature conditions. By using the water-pre-hydrolysis, soda-Anthraquinone cooking (soda-AQ), and elementary-chlorine-free (ECF) bleaching sequences, this work aims to convert ST into DP. Results, The DP was produced with a yield of 43.69%, a kappa value of 4.73, a viscosity of 9.3 cP, an alpha-cellulose content of 97.7% and a brightness of 90.7%, which was higher than the ISO brightness of 88%. The DP quality corresponds to the minimum DP level for rayon according to the Indonesian National Standard (SNI). It is very promising for further development, such as being used for viscose fiber production.

Abstract: In various fields such as engineering, nanotechnology, and biomedical sciences, the study of non-Newtonian nanofluid flow with heat generation is becoming increasingly important. However, it is challenging to accurately model such flows due to their complex behavior and slip effects at the fluid-solid interface. This research investigates the impact of first and second-order slip conditions on the flow and heat transfer properties of a non-Newtonian nanofluid using a power law model to describe the fluid's non-Newtonian behavior and numerical methods to solve the resulting equations. To determine the influence of various parameters such as slip parameters, Brinkman number, power law index, and Eckert number on the velocity, temperature, and concentration profiles, which this study examines. The study shows that slip parameters significantly determine the flow and heat transfer properties of non-Newtonian nanofluids, the study also reveals that slip parameters are a crucial factor in understanding the flow and heat transfer characteristics of nanofluids, with the second-order slip condition having a greater impact on velocity and temperature profiles than the first-order slip condition. These findings are valuable for developing and optimizing heat transfer devices that involve non-Newtonian nanofluids with heat generation, which is essential for technological advancements in today's industry.

Abstract: The temperature dependence of the diffusion coefficient in metallic glass-forming systems do not follow the Arrhenius behavior over a wide temperature range. Instead, it exhibits a kink behavior at around the glass transition temperature. Some researchers associate this behavior to the difference in the diffusion mechanism operating in the glassy and the supercooled liquid state, whereas others do not support this view. In addition, usually, the temperature dependence of the diffusion coefficient is analyzed by splitting the temperature range into two regions, above and below the glass transition temperature. In the present study, we developed an analytical theory that describes the continuous variation of the diffusion coefficient across a temperature where the kink behavior is observed. According to the theory, the kink behavior arises from the freezing of free volume available for diffusion by lowering the temperature. A connection to the vacancy mechanism of diffusion has been also pointed out.

Abstract: Direct ink writing (DIW) is an extrusion additive manufacturing (AM) technique in which inks are extruded through a nozzle and then deposited layer-by-layer. This technology allows 3D printing many different materials such as ceramics, metals, food, etc. In this work, the performance of zirconia pastes is addressed. The pastes are composed of yttria stabilized zirconia (YSZ) powder and a polymeric binder. Ceramic content is a mix of two components: A and B. Both the total content of ceramic and the content of component A in the paste are varied, according to a 3² design of experiments. The paste was characterized regarding Densification (%) and Elastic modulus G’ (Pa). A new parameter w³/G’ is defined to evaluate the viscosity of the inks. In the tests, the ceramic percentage is limited by the pressing force of the plunger that will be used to extrude the pastes. On the other hand, the binder concentration is also limited, because it requires to be in a gel form in order to be properly extruded. The results showed that Densification depends mainly on ceramic content, while the w³/G’ parameter is related to percentage of component A. In this work, the properties of the pastes prior to 3D printing are assessed. However, in the future, the pastes will be used to extrude complex parts with medical applications. AM extrusion processes constitute a possible way to overcome the difficulties to obtain complex geometries with conventional methods such as machining, in which zirconia parts can break due to their brittleness. Thus, the results of this work will help to manufacture complex shapes with porous areas in zirconia, when the DIW technology is employed.

Abstract: Shear thickening fluids (STF) viscosity significantly increases when subjected to an external dynamic load. Recent advances show their potential for engineering applications, such as developing shock absorbers and impact energy-absorbing structures. There is a search for sustainable materials for several applications due to the critical need to replace nonrenewable raw materials. Cork is a sustainable material reported to be an excellent alternative to synthetic energy absorbers thanks to its cellular microstructure and cell wall composition. This work explores the development of cork-STF composites designed for impact energy mitigation. The cork-STF composites were manufactured by compression moulding, exploring different compositions of both materials. Additionally, the manufactured compounds were characterized by submitting samples to impacts. The results made it possible to conclude that deagglomeration occurs for STF concentrations higher than 20%. On the other hand, good results were achieved with compounds that have less than 20% of STF in their composition and can withstand impact loading. Therefore, the energy absorption of white cork agglomerates decreases with STF. Nevertheless, the agglomeration was successful, and this design can be adapted for other specific purposes, applications, or even strain rates than the ones explored in this work.

Abstract: The effect of chemical and physical effects on the viscosity of heavy oil has been experimentally investigated in the work. The effect of the addition of a reagent on the viscosity of heavy oil, as well as the effect of microwave exposure under different modes on the effectiveness of reducing the viscosity has been established. The effectiveness of the joint physical and chemical action for reducing the viscosity of heavy oil is shown.

Abstract: – The research on CPO as an insulator to replace mineral oil. The CPO was heated using vacuum distillation technology. The parameters used are the temperature of 110°C to 170°C with the difference of 10°C and the vacuum pressure of 0 mmHg to-600 mmHg with the difference of 200 mmHg. The highest breakdown voltage measurement of 49 kV (170°C-600 mmHg), the lowest viscosity is 20 mPas (170°C-600 mmHg), the lowest water content was obtained at 30 (160°C-400 mmHg). The vacuum pressure and temperature rise causes the high breakdown voltage and viscosity are high and the water content is low. The relationship between vacuum pressure and breakdown voltage is y = 5.8 x + 7 with R² of 0.9397, the viscosity is y = -2x + 35.67 with R² of 0.9231 and the water content is y=-7.25x2 + 22.95x + 106.75 with R² of 0.9945.

Abstract: The analysis of high temperature physical and chemical properties of molten salt system of aluminum electrolysis has guiding significance for practical production In this paper, the molecular dynamics calculation method was used to simulate the physical and chemical properties of 78%Na₃AlF₆-9.5%AlF₃-5.0%CaF₂-7.5%Al₂O₃ molten salt electrolyte system with Zr and B as additives at 1200K and standard atmospheric pressure. The effects of Zr and B elements on the radial distribution function, coordination number, diffusion coefficient, viscosity, and conductivity of electrolyte system were discussed in detail. The simulation results showed that Zr⁴⁺ weakened the connection between Al³⁺, while the addition of B³⁺ enhanced the interaction between Al³⁺, Na⁺, and F^-. In the electrolyte system without impurities, the order of self-diffusion coefficient is Na⁺ > O^2- > F^- > Ca²⁺ > Al³⁺. And the addition of Zr⁴⁺ is conducive to the diffusion of ions in the system, while the addition of B³⁺ is not conducive to the diffusion of ions in the system. What’s more, the addition of Zr improves the conductivity of the system, while the addition of B reduces the conductivity of the system.