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Creep Models of Nanocomposites Deterministic Approach
Published in Leo Razdolsky, Phenomenological Creep Models of Composites and Nanomaterials, 2019
Chemical thermodynamics is a branch of physical chemistry, in which thermodynamic methods (general thermodynamics) are used for analysis of chemical and physicochemical phenomena: chemical reactions, phase transitions and processes in solutions. Chemical thermodynamics uses for calculations parameters that are known from experience—data about the initial and final state of the system and the conditions under which chemical process is evolving (temperature, pressure, etc.). Consequently, chemical energy is an integral part of the general Gibbs theory (and hence the integral creep equation), for example, in the case of the creation of nanocomposites materials (the ‘nucleation and growth of clusters’) by the synthesis of chemical elements or by an autocatalytic chemical reaction. Many of nanochemical processes can be described (at least in engineering applications) as a first order chemical reaction, except for autocatalytic reactions. Autocatalysis is the process of catalytic acceleration of a chemical reaction by one of its products. The kinetic curve of the product of the autocatalytic reaction has a characteristic S-shape. The rate of these equations for autocatalytic reactions are fundamentally nonlinear. There are many methods for Measurement of Reaction Rates: one might monitor the concentrations; the total volume or pressure if these are related in a simple way to the concentrations. Whatever the method, the result is usually something like that illustrated in Fig. 4.3.
Chemical Reaction Thermodynamics, Kinetics, and Reactor Analysis
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
Next we will consider the example of an autocataytic reaction. In an autocatalytic reaction, the product of the reaction acts as the catalyst. () A+R→R+R
Basic Chemical Thermodynamics and Kinetics
Published in Kalliat T. Valsaraj, Elizabeth M. Melvin, Principles of Environmental Thermodynamics and Kinetics, 2018
Kalliat T. Valsaraj, Elizabeth M. Melvin
In some environmental chemical reactions, some of the products of the reaction act as catalysts. A bimolecular autocatalysis reaction is represented as A + B → 2B. The rate expression is r = −d[A]/dt = k[A][B]. Let us define the progress of the reaction by ξî. If at any time [A]0 − [A] = [B] − [B]0 such that [B] = [A]0 + [B]0 − [A] = [A]0 + [B]0 − ξ, −dξdt=kξA0+B0−ξ This equation can be integrated to obtain B=A0+B01+A0B0⋅e−kA0+B0t Note from this that at t = 0, [B] = [B]0. For [B]0, the only condition is that [B] = 0 for all t. However, if [B]0 ≠ 0 at t = 0, [B] will slowly increase; this is termed the “induction period.” The value of [B] increases continuously and reaches its maximum value of [A]0 + [B]0 as t → ∞. The characteristic S-shaped curve shown in Figure 2.40 is characteristic of autocatalytic reactions in the environment. Oscillatory reactions such as the oxidation of malonic acid by bromate and catalyzed by cerium ions (otherwise called the “Belousov-Zhabotinsky reaction”) are classic examples of autocatalysis.
Characterization of MHD convective flow of Jeffrey nanofluid driven by a curved stretching surface by employing Darcy–Forchheimer law of porosity
Published in Waves in Random and Complex Media, 2022
B. Nagaraja, B. J. Gireesha, D. O. Soumya, Felicita Almeida
Srinivas et al. [22] explored non-Darcian time-reliant micropolar fluid flowing over a porous stretched surface. Their work is authenticated by former works. Makinde and Animasaun [23] recorded the slip mechanism involved in Buongiorno model for bioconvective flow with thermal radiation that is non-linear moving on top horizontal paraboloid of revolution surface. Krishnamurthy et al. [24] analyzed the influence of thermal radiation, chemical reaction on slip flow stimulated by a non-linear stretched sheet. Koriko et al. [25] scrutinized thermal stratification, an autocatalytic chemical reaction on 3D Eyring-Powell alumina-water nanofluid flow. Their study concluded that homogeneous fluid concentration rises, while heterogeneous fluid concentration at the wall drops with a magnetic parameter.
Aspects of active-passive controls of nanoparticles of chemically reactive and radiative nanofluid flow past a frequently moving thin needle with thermal and velocity slip: A numerical framework
Published in Numerical Heat Transfer, Part A: Applications, 2023
Thermal radiation is quite an interesting part of the engineering and technology sector due to its vast physical applications. It is also employed in biomedicines, cancer treatment, paper production, space equipment, chemical hub, nuclear power plant, energy propagation from the sun, and even our daily cooking at home. Nadeem et al. [24] expressed this radiation layer stream a nanoliquid flow passing over a stretching surface. Ahmed et al. [25] extended the study with viscous and joule heating. Afridi et al. [26] considered a nanofluidic flow model with CNT passing over a thin needle and analyzed the heat radiation effect. Along with the same radiation, another research on hybrid nanocomposition flow on a stretching disk has been done by Farooq et al. [27]. Energy generation and viscous have also enriched the problem. Very recently et al. [28] explained the consequences of the radiation on the flow of nanosuspension through a curved surface in the existence of autocatalytic chemical reaction. Sedki [29] highlighted the previous impacts on MHD mixed convective nanofluidic drift upon a nonlinearly stretched plate in a porous medium. Also, Arshad et al. [30] provided the outcomes for the existence of this radiation accompanied by chemical reactions in their investigation. The parallel researches are also existed [31–37].
Curing kinetics and mechanical properties of an underwater SiO2/epoxy adhesive
Published in The Journal of Adhesion, 2023
Xiaodong Wang, Xin Zhang, Xiaotian Bian, Chenchen Lu, Qi Li, Chengying Bai, Lili Zhang, Ting Zheng
The first stage is the initial stage of the curing reaction (α < 20%), where the reaction is just started and the growth of α is slow. Then, with increasing temperature, α gradually increases. The second stage is the middle stage of the curing reaction (20% < α < 80%). In this stage, α increases rapidly with increasing temperature owing to the higher temperature of the curing system and exothermic curing reaction, which further accelerate the curing reaction rate. The third stage is the last stage of the curing reaction (α > 80%). In this stage, the viscosity of the curing system is higher, the system is in a gel state, the movement of the molecular chain is blocked, and the unreacted active functional groups require more energy to continue the reaction, resulting in the slow growth of α. Furthermore, as the heating rate β increases, the α–T curve gradually moves toward the higher temperature, implying that α is a function of temperature T. To further understand the relation between dα/dt and α, the dα/dt–α curve was obtained via differential treatment of the α–T curve at different heating rates (β), as shown in Figure 2(c). The results show that dα/dt first increases and then decreases with increasing α and increasing the heating rate can increase the curing-reaction rate. However, the αmax value corresponding to the maximum curing rate remains constant in the range of 0.35–0.45, indicating that an autocatalytic curing-reaction mechanism may be followed in the SiO2/epoxy adhesive curing system.