In the Search of Fundamental Inner Bond Strength of Solid Elements

In order to understand the physics behind the surface properties and nano-scale phenomena, we are motivated first to investigate the inner bond strengths as well as the effect of number of neighboring atoms and their relative distance in addition to space positions (crystallography). Therefore, in order to study the effect of the nature of metallic bond on their physico-chemical properties, we first tried to investigate and introduce a mathematical model for transforming the bulk molar cohesion energy into microscopic bond strengths between atoms. Then an algorithm for estimating the nature of bond type including the materials properties and lattice scale “cutoff” has been proposed. This leads to a new fundamental energy scale free from the crystallography and number of atoms. The results of our model in case of fundamental energy scale of metals not only perfectly describe the inter relation between binding and melting phenomena but also adequately reproduce the bond strength for different bond types with respect to other estimations reported in literatures. The generalized algorithm and calculation methodology introduced here by us are suggested to be used for developing energy scale of bulk crystal materials to explain or predict any particular materials properties related to bond strengths of metallic elements

Egyensúlyi fázisdiagrammok számítása ESTPHAD módszerrel = Calculation of Equilibrium Phase Diagrams by ESTPHAD method

Az egyensúlyi fázisdiagramok igen jelentős része csak grafikusan ismert, vagy - egy csekély hányaduk -komplikált, igen hosszú CPU időt lekötő eljárással számítható ki. Ez a felismerés vezetett az ESTPHAD módszer és szoftver kidolgozásához. A módszer alapja az átalakulási hőmérsékletet leíró -termodinamikai összefüggésekből levezetett- egyenletek, melyekkel kiszámíthatók az átalakulások kezdő és befejező hőmérsékletei. A rendszer hierarhikus, azaz a többalkotós rendszerek egyenletei tartalmazzák az alacsonyabb rendű rendszerek állandóit. Az állandók mért, grafikusan ismert vagy valamely termodinamikai számításból kapott adatokból regresszióval határozhatók meg. A munka során 16 kétalkotós vas, 12 kétalkotós alumínium alapú, számos réz és nemesfém alapú kétalkotós rendszer vonalainak adatait dolgoztuk fel egészben vagy részben. A kétalkotós alumínium alapú ötvözetek adatait felhasználva 4 háromalkotós egyensúlyi fázisdiagram alumínium sarkának likvidusz és szolidusz felületeinek az egyenleteit is meghatároztuk. Feldolgoztuk 6 binér, 4 ternér és egy kvaternér oxid rendszert is. A rendszer egyszerű felhasználása érdekében egy szabadon felhasználható szoftvert dolgoztunk ki. A szoftver alkalmas az adatbázisban való keresésre, valamint lehetőség nyílik olyan szoftver részek letöltésére, amelyeket a szimulációs programba építve bárki ki tudja számítani az egyensúlyi fázisdiagramok adatait. A szoftver és az adatbázis a www.matsci.uni-miskolc.hu/estphad honlapról szabadon letölthető. | The majority of phase equilibria are known only in graphically presented phase diagrams. Alternatively, it can be computed using a so-called Calphad method. The latter, however, requires long CPU times for the numerical solution. This situation lead us to the idea to develop a new method and a computer code called Estphad. The method is based on thermodynamically derived equations. The Estphad system is hierarchically built. The coefficients of Estphad can be obtained by regression analysis, using measured data, graphical phase diagram, or data obtained by a Calphad computer code. Equilibrium lines of 16 binary iron-, 12 binary aluminum-based, and a number of binary copper-based and precocious metal-based systems have been evaluated. Using the data obtained for the binary aluminum-based alloys, equations, describing the solidus and liquidus surfaces in the Al-corners of four ternary aluminum based systems have been obtained, as well. Additionally six binary, four ternary and one quaternary oxide phase diagrams have been calculated. To ensure a simple and widespread use of our new Estphad system, an open computer code has been developed. The code let anyone to search in the existing database. Also, one can download specific fragments of the code, which can be useful as sub-routines in larger simulation programs to calculate phase equilibrium data. The code and the existing database can be downloaded free of charge from the website www.matsci.uni-miskolc.hu/estphad

Határfelületi energiák és jelenségek vizsgálata fémolvadék fázist tartalmazó rendszerekben = Study of interfacial energies and phenomena in systems containing liquid metals

A 4-éves projekt célja határfelületi energiák, erők és jelenségek vizsgálata volt fémolvadék fázist tartalmazó rendszerekben, melynek keretein belül részben kísérleti, részben elméleti munkát végeztünk. A munka eredményeiből 17 impakt faktoros folyóiratcikk jelent meg, melyekre a mai napig 42 független hivatkozást kaptunk. A kísérleti munka során a. sóolvadékban vizsgáltuk kerámiaszemcsék fém titánnal való felületi bevonásának lehetőségét, b. fémolvadékok felületi feszültségét és peremszögét mértük kerámiákon, c. felületi fémmátrixú kompozitot állítottunk elő lézeres felületkezeléssel. A projekt keretein belül kidolgozott elméleti modellek típusai: a. határfelületi (és innen származtatott) anyagtulajdonságok modellezése: fémolvadékok felületi feszültsége, kohéziós energiája, viszkozitása, egyéb határfelületi energiák, ezek koncentrációfüggése, különös tekintettel a felületi fázisátalakulásra, b. határfelületi erők modellezése: közös, általános képlet és algoritmus megalkotása - egyszerűsített geometriákra a hat, különböző határfelületi erő képletének levezetése, c. komplex határfelületi jelenségek modellezése, úgymint kristályfront - kerámiaszemcse kölcsönhatás, szemcse -fémolvadékfelület dinamikai kölcsönhatása, fémolvadék infiltráció különböző morfológiájú preformákba, szemcsékkel erősített fémmátrixú kompozitok, illetve szemcsékkel stabilizált fémhabok és fémemulziók stabilitása. | The goal of the 4-year project was to study interfacial energies, forces and phenomena in systems, containing a liquid metallic phase. 17 papers in journal with impact factors have been published, with total 42 independent references obtained so far. Experimentally the following subjects were covered: i. the possibility to coat ceramic particles by metallic titanium from molten salt was investigated, ii. surface tension of liquid metals and their contact angle on ceramic plates were measured, iii. a surface composite material was produced by a Laser Melt Injection technique. Theoretically the following types of models were developed: i. modeling interfacial (and related) properties, such as surface tension, other interfacial energies, cohesion energy and viscosity of liquid metals, their concentration dependence, with emphasis on surface phase transition, ii. modeling interfacial forces - the derivation of a most general equation and algorithm top derive interfacial forces, and the derivation of equation (for simplified geometries) for the 6 types of interfacial forces, iii. modeling complex interfacial phenomena, including the interaction of a solidification from with particles, dynamic interaction of particles with liquid surfaces, infiltration of liquid metals into preforms of different morphologies, stability of particle reinforced metal matrix composites, particles stabilized metallic foams and emulsions

In the Search of Fundamental Inner Bond Strength of Solid Elements

In order to understand the physics behind the surface properties and nano-scale phenomena, we are motivated first to investigate the inner bond strengths as well as the effect of number of neighboring atoms and their relative distance in addition to space positions (crystallography). Therefore, in order to study the effect of the nature of metallic bond on their physico-chemical properties, we first tried to investigate and introduce a mathematical model for transforming the bulk molar cohesion energy into microscopic bond strengths between atoms. Then an algorithm for estimating the nature of bond type including the materials properties and lattice scale “cutoff” has been proposed. This leads to a new fundamental energy scale free from the crystallography and number of atoms. The results of our model in case of fundamental energy scale of metals not only perfectly describe the inter relation between binding and melting phenomena but also adequately reproduce the bond strength for different bond types with respect to other estimations reported in literatures. The generalized algorithm and calculation methodology introduced here by us are suggested to be used for developing energy scale of bulk crystal materials to explain or predict any particular materials properties related to bond strengths of metallic elements

On the plasma chemistry of CH4-H2-Ar system relevant to diamond deposition process by plasma enhanced chemical vapor deposition

Diamond films are extensively deposited using plasma enhanced chemical vapor deposition (PECVD). In this work, the most important non-neutral plasma surface processes, which are needed to analyze the deposition mechanism of diamond films from plasma gas phase, are considered. Moreover, the role of ionic species, which is mostly neglected in deposition investigations, has been considered. To analyze the diamond deposition process, we use the reaction probability algorithm for different surface phenomena. Then, using different methods like Motz and Wise modified relation, the reaction probability is transformed to the mass action kinetic rate constant. Our results lead to the calculation of rate coefficients for non-neutral gas-surface reactions that take place during the diamond deposition from plasma in CH4-H-2-Ar system

Fe Doping in TiO₂ via Anodic Dissolution of Iron: Synthesis, Characterization, and Electrophoretic Deposition on a Metal Substrate

The tailored physical properties of TiO2 are of significant importance in various fields and, as such, numerous methods for modifying these properties have been introduced. In this study, we present a novel method for doping Fe into TiO2 via the anodic dissolution of iron. The optimal conditions were determined to be an application of 200 V to acetylacetone (acac)/EtOH medium for 10 min, followed by the addition of TiO2 to the solution, sonication for 30 min, stirring at 80 °C, and drying. The resulting powder was calcined at 400 °C for 3 h, and characterization was conducted using XRD, FTIR, TEM, and UV-vis. The synthesized powder revealed the successful doping of Fe into the TiO2 structure, resulting in a decrease in the optical band gap from 3.22 to 2.92 eV. The Fe-TiO2 was then deposited on a metal substrate via the electrophoretic (EPD) technique, and the weight of the deposited layer was measured as a function of the applied voltage and exposure time. FESEM images and EDX analysis confirmed that the deposited layer was nanostructured, with Fe evenly distributed throughout the structure