Thermodynamics of Solid-Phase Exchange Reactions Limiting the Subsolidus Structure of the System MgO-Al2O3-FeO-TiO2

2021 ◽  
Vol 1038 ◽  
pp. 177-184
Author(s):  
Oksana Borisenko ◽  
Sergey Logvinkov ◽  
Galina Shabanova ◽  
Oksana Myrgorod

The basis of modern materials science is multicomponent systems, on their basis it is possible to create various combinations of phases in structural materials with a set of specified properties. The investigated system MgO-Al2O3-FeO-TiO2 is promising for the production of periclase-spinel refractories used as lining of rotary kilns during cement clinker firing, which are highly resistant to chemical corrosion when exposed to a gas environment and cement clinker components; thermomechanical stresses. However, in the reference literature and scientific articles, no information was found on the structure of the four-component diagram of the state of the MgO-Al2O3-FeO-TiO2 system, partial elements of its structure are given only in the composition of multicomponent systems [1-3]. Thus, research to the study of the subsolidus structure of the MgO-Al2O3-FeO-TiO2 system, which is the physicochemical basis for the development of compositions of periclase-spinel refractories, is urgent.

Author(s):  
Oksana Borysenko ◽  
Sergii Logvinkov ◽  
Halyna Shabanova ◽  
Igor Ostapenko ◽  
Olena Gaponova

Over the past decades, the development and improvement of refractory materials for lining high-temperature zones of rotary kilns continues. The main requirements for refractory products for lining rotary kilns for cement clinker roasting are: high density and ultimate compressive strength, low porosity and gas permeability, increased abrasion resistance, low thermal conductivity, high corrosion resistance and the ability to form a protective layer.Today, the main goal of modern researchers is to create a heat-resistant refractory with a flexible structure that ensures its integrity at high temperatures and mechanical loads, which have the ability to form a protective coating layer. In this work, a technological approach has been tested for introducing a vibro-milled modifier (briquette based on a high-alumina component and a titanium-containing additive) into the composition of the raw charge for periclase-spinel refractory in the form of a pre-synthesized product containing crystalline phases of the Al2O3 – TiO2 – FeO system. The basis for the production of periclase-spinel refractories modified with TiO2 is the four-component system MgO – Al2O3 – FeO – TiO2, on the basis of thermodynamic calculations of which the content of individual components of the charge was selected and the operational characteristics were predicted. The interrelation of physical and mechanical properties with the content of individual components in the initial charge warehouses is shown, and the directions of solid-phase processes with their participation are noted. The features of the microstructure of the sample material are noted in relation to the formation of an optimal set of properties. It is shown that the nature of the organization of micropores is favorable for increasing the thermal stability of the material, which complements the phase adaptation mechanism also with the structural effect of damping mechanical stresses during thermal cycling.


Author(s):  
Vladimir V. Moskvichev ◽  
Natalya A. Chernyakova

The state, problems, directions of perspective research and tasks of the modern development of the machinery complex in the strategic planning documents are considered. Research tasks in the field of machine science, structural materials science, general engineering technologies (metalworking, casting, welding), digital industrial technologies, and the safety of technical systems are highlighted based on the concept of non-zero risk of accidents in the field of machinery and equipment used in Siberia, Northern and Arctic regions


2013 ◽  
Vol 80 (2) ◽  
Author(s):  
Ranena V. Ponce F. ◽  
Márcio A. Murad ◽  
Sidarta A. Lima

We propose a new two-scale model to compute the swelling pressure in colloidal systems with microstructure sensitive to pH changes from an outer bulk fluid in thermodynamic equilibrium with the electrolyte solution in the nanopores. The model is based on establishing the microscopic pore scale governing equations for a biphasic porous medium composed of surface charged macromolecules saturated by the aqueous electrolyte solution containing four monovalent ions (Na+,Cl-,H+,OH-). Ion exchange reactions occur at the surface of the particles leading to a pH-dependent surface charge density, giving rise to a nonlinear Neumann condition for the Poisson–Boltzmann problem for the electric double layer potential. The homogenization procedure, based on formal matched asymptotic expansions, is applied to up-scale the pore-scale model to the macroscale. Modified forms of Terzaghi's effective stress principle and mass balance of the solid phase, including a disjoining stress tensor and electrochemical compressibility, are rigorously derived from the upscaling procedure. New constitutive laws are constructed for these quantities incorporating the pH-dependency. The two-scale model is discretized by the finite element method and applied to numerically simulate a free swelling experiment induced by chemical stimulation of the external bulk solution.


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
НИНА МАЛАХОВА ◽  
Fatima Dzgoeva

Abstract Background and Aims Clinical studies in recent years have revealed a close relationship between hormonal disorders in women with CKD and the duration and quality of life, bone mineral and related disorders of the cardiovascular system. In individual studies, there is a tendency to improve the indicators of mineral and bone metabolism and the state of the cardiovascular system in hormonal or other drug-induced correction of hormonal dysfunctions in women. - Aims to study the effect of estrogen deficiency on bone and mineral metabolism in a population of women suffering from CKD stages III-V Method The study included 52 women who met the clinical criteria for the possible appointment of hormone therapy (both replacement and combined oral contraceptives) for the purpose of a detailed examination of the state of their cardiovascular system and bone-mineral metabolism in dynamics (with an interval of 10-12 months) in order to assess the degree of influence of estrogen-deficient conditions on the course of such common complications of CKD as cardiovascular diseases and pathology of the bone system. The age of the patients ranged from 26 to 61 years (mean age-50.65±9.17 years). The duration of CPN averaged 77.02 months.. The stages of CKD were determined according to the K/DOQI (2012) criteria, and the glomerular filtration rate was calculated using the CKD-EPI formula. The following parameters were evaluated: the concentration of sclerostin, osteoprotegerin, fibroblast growth factor 23 (FGF-23), parathyroid hormone, total calcium, phosphorus, alkaline phosphatase, creatinine, and urea. Follicle-stimulating hormone( FSH), luteinizing hormone(LH) and estradiol were determined by solid-phase chemiluminescent enzyme immunoassay (commercial sets of Alkor-Bio, St. Petersburg). Serum concentrations of sclerostin, sRANKL (soluble RANKL), and osteoprotegerin were determined by the enzyme-linked immunoassay using Biomedica gruppe test systems. Results The examined patients showed hormonal dysfunctions (82%), accompanied by changes in the content of sex hormones: the concentration of estradiol was below normal: 123.4±72.5 pmol/l and 150.0-450.0 pmol/l, respectively, in patients and in normal (p<0.01), which confirms the presence of estrogen deficiency in the examined patients . Concentrations of FSH and LH exceeded the norm in the group of patients as a whole: 91.6±46.1 IU/l and 3.0-8.0 IU/l FSH content in patients and normal; 51.8±32.1 IU/l and 3.0-10.0 IU/l LH in patients and normal. In the group of patients as a whole, an increase in the level of sclerostin to 28.5 ± 9.2 pmol/l was detected ( norm 12±33.45 pmol/l), an increase in the level of osteoprotegerin to 6.9±0.4 pmol/l (norm 2.7 pmol/l). Positive and negative correlations were found between the levels of morphogenetic proteins, sex hormones, and characteristic parameters of hormonal dysfunctions Conclusion Pre-and postmenopausal women with CKD have hormonal dysfunctions, including disorders of sexual and reproductive function, menstrual cycle, decreased fertility, increased risks of miscarriage at its onset, the basis of hormonal dysfunctions is the absence of LH peaks and changes in the concentration of estradiol depending on the phase of the cycle, hypoestrogenemia. It is assumed that there is a pathogenetic link between hormonal dysfunctions and disorders in the system of bone metabolism regulatory proteins in patients with CKD.


2020 ◽  
Author(s):  
Nathaniel E. Kallmyer ◽  
Nathan E. Rider ◽  
Nigel F. Reuel

AbstractSolid phase peptide synthesis (SPPS) has enabled widespread use of synthetic peptides in applications ranging from pharmaceuticals to materials science. The demand for synthetic peptides has driven recent efforts to produce automated SPPS synthesizers which utilize fluid-handling components common to chemistry laboratories to drive costs down to several thousand dollars. Herein, we describe the design and validation of a more ‘frugal’ SPPS synthesizer that uses inexpensive, consumer-grade fluid-handling components to achieve a prototype price point between US$300 and $600. We demonstrated functionality by preparing and characterizing peptides with a variety of distinct properties including binding functionality, nanoscale self-assembly, and oxidation-induced fluorescence. This system yielded micromoles of peptide at a cost of approximately $1/residue, a cost which may be further reduced by optimization and bulk purchasing.


Author(s):  
Daniel B. Miracle ◽  
Mu Li ◽  
Zhaohan Zhang ◽  
Rohan Mishra ◽  
Katharine M. Flores

Structural materials have lagged behind other classes in the use of combinatorial and high-throughput (CHT) methods for rapid screening and alloy development. The dual complexities of composition and microstructure are responsible for this, along with the need to produce bulk-like, defect-free materials libraries. This review evaluates recent progress in CHT evaluations for structural materials. High-throughput computations can augment or replace experiments and accelerate data analysis. New synthesis methods, including additive manufacturing, can rapidly produce composition gradients or arrays of discrete alloys-on-demand in bulk form, and new experimental methods have been validated for nearly all essential structural materials properties. The remaining gaps are CHT measurement of bulk tensile strength, ductility, and melting temperature and production of microstructural libraries. A search strategy designed for structural materials gains efficiency by performing two layers of evaluations before addressing microstructure, and this review closes with a future vision of the autonomous, closed-loop CHT exploration of structural materials. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.


2019 ◽  
Vol 974 ◽  
pp. 255-260
Author(s):  
Ludmila A. Suleymanova

Theoretical and experimental materials for analyzing the technical capabilities of concrete are generalized and the physicochemical basis for the strength and durability of concrete is developed on the basis of the recent advances in building materials science and other sciences. That may increase the traditional concrete potential use and most importantly – to create the most firm and durable concrete of the new generation.


1991 ◽  
Vol 237 ◽  
Author(s):  
Michael A. Grinfeld

ABSTRACTIn the absence of surface tension and external force fields, the equilibrium between a hydrostatically stressed crystal and its melt is neutral with respect to the perturbations associated with particle transfer from one region of the boundary into another. However, under the action of arbitrary small nonhydrostatic components of the stress field in the elastic crystal, the neutral equilibrium is transformed to an unstable equilibrium [1]. This instability is very general in nature; for example, for it to be seen the liquid media need only to be able to dissolve the solid phase or in some way to assist the transport of particles along the crystal's surface. In contrast, the surface tension, roughly speaking, stabilizes the shape of the interphase boundary but it cannot suppress the instability generated by the nonhydrostatic components of the stress field in the region of sufficiently long perturbations. Until now the basic instability mechanism discussed here seems to have escaped the attention of theorists. This mechanism allows one to look in a completely new way at a broad range of phenomena. We discuss tentative manifestations and role of this instability in low temperature physics, in materials science, in theory of crystal growth, and, in particular, in theory of epitaxy and of the Stranski-Krastanow pattern of growth of thin crystalline films.


1996 ◽  
Vol 438 ◽  
Author(s):  
R. G. Elliman ◽  
H. Jiang ◽  
W. C. Wong ◽  
P. Kringhøj

AbstractGexSi1-x, strained layers can be fabricated by Ge implantation and solid-phase epitaxy and can be used in electronic devices to improve their performance. Several important materials science issues are addressed, including the effect of the strain on solid-phase-epitaxy, the effect of oxidation on the implanted Ge distribution, and the effect of Ge on the oxidation rate of Si. The potential of this process is demonstrated by comparing the performance of metal-oxidesemiconductor field-effect-transistors (MOSFETs) employing ion-beam synthesised GeSi strained layer channel regions with that of Si-only devices.


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