Influence of gamma radiation and magnetic resonance imaging radiation on micro-structure,hardness and electrochemical corrosion behavior of Co‒Cr-based dental alloy

The effects of therapeutic gamma radiation at 10, 20 and 30 kGy and magnetic resonance imaging radiation from a 1.5 T MR scanner on the micro-structure, electrochemical corrosion behavior and micro-hardness of commercial dental Magnum H50 (Co=64%, Cr=29%, Mo=6.5%) alloy have been investigated. The corrosion rate, corrosion resistance, corrosion potential and corrosion current density values of the alloy treated with 0.5 M HCl vary due to gamma and magnetic resonance imaging radiation. At 30 kGy, the corrosion resistance of Magnum H50 reaches a minimum value and the corrosion rate obtains a maximum value. The Vickers hardness value of the Magnum H50 alloy decreases after both gamma and magnetic resonance imaging radiation.     

Electrochemical corrosion behavior,Vickers microhardness,and microstructure of Co–Cr and Ni–Cr dental alloys

Electrochemical corrosion behaviors, Vickers microhardness, microstructure, and electrical properties of Magnum H50 (Co=64.5%, Cr=29%, Mo=6.5% ) and Nikkeli–Kromi–Polttosekoitus (Ni=65.2%, Cr=22.5%, Mo=9.5%, X=2.8% Nb, Si, Fe, and Mn) dental alloys have been investigated. The corrosion potential for the Co_64.5Cr₂₉Mo_6.5 alloy in HCl was higher than that of the Ni_65.2Cr_22.5Mo_9.5X_2.8 alloy. The corrosion rate with 0.5 M HCl for the Ni_65.2Cr_22.5Mo_9.5X_2.8 alloy was measured as being high and the corrosion resistance as being small as compared with the values for the Co_64.5Cr₂₉Mo_6.5 alloy. Vickers hardness of the Co_64.5Cr₂₉Mo_6.5 alloy was higher than that of the Ni_65.2Cr_22.5Mo_9.5X_2.8 alloy. Also Vickers hardness values of the used alloys were decreased by increasing indentation load. The thermal conductivity and minimum shear stress values of the used alloys are calculated.     

Influence of Cr on microstructure and elastocaloric effect in Ni–Mn–In–Co–Cr polycrystalline alloys

Ni–Mn-based metamagnetic shape memory alloys have been proposed as potential elastocaloric refrigerants. The intrinsic brittleness of the alloys has limited their cooling application. Introducing a soft second phase is an effective way to reduce the brittleness. From the viewpoint of application, the effect of second phase on elastocaloric effect should be illustrated. In this paper, we have investigated the microstructure, martensitic transformation and elastocaloric effect of Ni₄₅Mn_37-xIn₁₃Co₅Cr_x ($x=0,1\text{ and }2$) polycrystalline alloys. Single-phase and precipitates-containing microstructures are obtained for the undoped and doped alloys, respectively. The precipitates in Cr-doped alloys enhances the fracture strength but significantly hinders the martensitic transformation. Balancing the fracture strength and martensitic transformation, the Ni₄₅Mn₃₆In₁₃Co₅Cr alloy with small amount of precipitates along grain boundaries exhibits large cooling effects of 4–6 K in the temperature range of 317–353 K.     

Effect of thermal cycling on structure and properties of Ni–Mn–In-based alloys

Technical Physics - The results of investigations of the structure and properties of ternary alloys Ni47–x Mn42 + x In11 (0 ≤ x ≤ 2) after thermal cycling are presented. It has...     

Influence of temperature and alloying elements on the threshold displacement energies in concentrated Ni–Fe–Cr alloys

Concentrated solid-solution alloys(CSAs) have demonstrated promising irradiation resistance depending on their compositions. Under irradiation, various defects can be produced. One of the most important parameters characterizing the defect production and the resulting defect number is the threshold displacement energies(E_d). In this work, we report the results of E_dvalues in a series of Ni–Fe–Cr concentrated solid solution alloys through molecular dynamics(MD)simulations. Based on several different empirical potentials, we show that the differences in the E_dvalues and its angular dependence are mainly due to the stiffness of the potential in the intermediate regime. The influences of different alloying elements and temperatures on E_dvalues in different CSAs are further evaluated by calculating the defect production probabilities. Our results suggest a limited influence of alloying elements and temperature on E_dvalues in concentrated alloys. Finally, we discuss the relationship between the primary damage and E_dvalues in different alloys. Overall, this work presents a thorough study on the E_dvalues in concentrated alloys, including the influence of empirical potentials,their angular dependence, temperature dependence, and effects on primary defect production.     

Effect of Fe on the glass-forming ability,structure and devitrification behavior of Zr–Cu–Al bulk glass-forming alloys

We report on the glass-forming ability and devitrification behavior of Zr₆₀Cu₃₀Al₁₀, Zr₆₀Cu₂₅Al₁₀Fe₅ and Zr_62.5Cu_22.5Al₁₀Fe₅ bulk glass-forming alloys on heating. The effect of Fe addition on the structure of Zr–Al–Cu alloys is also discussed. Crystallization kinetics and structural changes in the glassy alloys were studied using X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods. The results indicate that good glass-formers, such as Zr_62.5Cu_22.5Al₁₀Fe₅, are located somewhat beyond the equilibrium eutectic point. Possible phase separation in the supercooled liquid on heating and electron beam-induced in situ crystallization are observed and discussed.     

Phase transformations and structure of Ni–Mn–In alloys with varying ratio Ni/Mn

The fine structure of Ni–Mn–In alloys has been studied when manganese atoms are substituted for nickel atoms in an annealing state. The concentration dependence of the critical temperatures and the structures of the alloys have been discussed. It has been found that, as manganese atoms replace nickel atoms, the structure after annealing is changed from a two-phase (L2₁ + martensite) to single-phase L2₁ structure. The martensitic transformation in Ni₄₇Mn₄₂In₁₁ alloy is accompanied by the formation of modulated 14M martensite.     

Effects of annealing time on the structure,morphology, and stress of gold–chromium bilayer film

In this work, a 200-nm-thick gold film with a 10-nm-thick chromium layer used as an adhesive layer is fabricated on fused silica by the electron beam evaporation method. The effects of annealing time at 300℃ on the structure, morphology and stress of the film are studied. We find that chromium could diffuse to the surface of the film by formatting a solid solution with gold during annealing. Meanwhile, chromium is oxidized on the surface and diffused downward along the grain grooves in the gold film. The various operant mechanisms that change the residual stresses of gold films for different annealing times are discussed.     

Influence of environment on the corrosion of glass–metal connections

‘Glass sensors’ of the eighteenth century Backer glass and the sixteenth century enamel from Limoges have been chosen for a series of experiments. Combinations of these materials with different base materials such as copper and bronze has been investigated. To create surface changes on the ‘glass sensor’, a corrosion process was induced in a controlled environment. A variety of corrosive agents such as hydrochloric acid, sulfuric acid, water and formaldehyde were used. The sample immersed in the corrosive solution was exposed alternately to light and high temperature for a total of 38 weeks. During this period, macroscopic and microscopic observations were made and series of tests such as SEM/EDS and Raman spectroscopy were performed on the surface of the samples. ICP-MS methods were used to determine the change in the chemical composition of the solutions where the samples had corroded. The primary aim of this study was to identify the impact of a number of external corrosive variables such as temperature, humidity and local environment to identify the most damaging environments for glass–metal objects. The obtained results showed the chemical and physical phenomena acting on the surface of the glass, metal or in the place of their joints. Information obtained on this study was used to explain the influence of the environment on the surface of glass–metal materials. Results can be used in the design of conservation work as well as for sustainable conservation.     

Influence of the evolution of heat-resistant phases on elevated-temperature strengthening mechanism and deformation behavior in Al–Si multicomponent alloys

Evolution of the heat-resistant phases and deformation behavior of α-Al matrix of four alloys have been characterized by SEM and EBSD. The strengthening mechanisms influenced by morphology and distribution of the heat-resistant phases were described. And the strain contouring of the α-Al matrix after deformation was rendered. The heat-resistant phases with block-like as reticular or semi-reticular network distribution exist in grain boundary can effectively provide elevated-temperature strength for alloys, while the strain contouring of α-Al matrix is mainly concentrated in the area with fewer intermetallic phases. It is shown that intermetallic phase evolution corresponds to extrusion treatment and the formation of eutectic Si and primary Si, highly interconnected networks of intermetallic phases exist in the alloy in which the primary Si and the eutectic Si are simultaneously present or disappeared. And only the disappearance of the primary Si and the extrusion treatment will destroy the network structure of the intermetallic phases. A reticular or semi-reticular microstructure is more capable of matching strength and plasticity and facilitating uniform deformation of the α-Al matrix. And the destruction of this microstructure is allowed to accommodate more plastic strain before failure.     

Effect of gamma and beta radiation on I–V characterization of the solar cell panel

ABSTRACT

Optoelectronic devices, widely used in high energy and nuclear physics applications, suffer severe radiation damage that leads to degradations in its efficiency. In this paper, the influence of gamma radiation (¹³⁷Ce source) and beta radiation (⁹⁰Sr source) on the photoelectric parameters of the Si solar cell, based on the I–V characterization at different irradiation exposer, has been studied. The penetrating radiation produces defects in the base material, may be activated during its lifetime, becoming traps for electron–hole pairs produced optically and, this will, decrease the efficiency of the solar cell. The main objective of the paper is to study and measure changes in the I–V characteristics of solar cells, such as efficiency, maximum current, maximum power, and efficiency, due to the exposure of solar systems to different doses of γ and β irradiations.     

Abnormal resistivity behavior of Cu–Ni and Cu–Co alloys in undercooled liquid state

The resistivity behavior of undercooled liquid Cu–Ni and Cu–Co alloys had been studied in the contactless method, to probe the structure transition in undercooled melts during the cooling process. Over the entire concentration range, linear behavior of resistivity with temperature was obtained in liquid and undercooled liquid Cu–Ni system. It implied that the formation of icosahedral order might not influence the electron scattering in undercooled liquid Cu–Ni alloys. Similar results were obtained in Cu–Co system in the vicinity of liquidus temperature. A turning point was obvious in temperature coefficient of resistivity for undercooled liquid Cu–Co alloys around the bimodal line, which was interpreted to be responsible for metastable liquid–liquid phase separation. During liquid phase separation process, resistivity decreased and the temperature coefficient of resistivity was larger than that of homogeneous melts. In combination with transmission electron microscopy and scanning electron microscope studies on the as-solidified microstructure, this was interpreted as the formation of egg-type structure and concentration change in Cu-rich and Co-rich phases. The mechanism controlling the separation and droplets motion was also discussed in undercooled liquid Cu–Co system.     

Theoretical study on the phase stability,elasticity, hardness and electronic structures of Ni–P compounds

A systematic investigation concerned with phase stability, elastic properties, hardness and relevant electronic structure of Ni–P compounds (Ni₃P, Ni₁₂P₅, Ni₂P, Ni₅P₄, NiP, NiP₂ and NiP₃) was carried out using first principles calculations. The calculated results show that the Ni–P compounds have strong hardness, ranging from 7.80–14.54 GPa. Also, the hardness values gradually increase with the P content. Electronic structure analysis shows that the strong Ni–P and part of P–P hybrid orbitals play important roles in the hardness of these compounds. The calculated elastic constants indicated that the Ni₃P, Ni₁₂P₅ and NiP₂ phases are significantly anisotropic, the NiP and Ni₂P exhibit some anisotropy, while the Ni₅P₄ and NiP₃ show a relatively isotropic character. At last, the properties of these Ni–P compounds including lattice constants, thermodynamic stability, elastic constants C_ij, bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν have been calculated.     

Effect of gallium alloying on the structure,the phase composition,and the thermoelastic martensitic transformations in ternary Ni–Mn–Ga alloys

The effect of gallium alloying on the structure, the phase composition, and the properties of quasibinary Ni₅₀Mn_50–zGa_z (0 ? z ? 25 at %) alloys is studied over a wide temperature range. The influence of the alloy composition on the type of crystal structure in high-temperature austenite and martensite and the critical martensitic transformation temperatures is analyzed. A general phase diagram of the magnetic and structural transformations in the alloys is plotted. The temperature–concentration boundaries of the B2 and L2₁ superstructures in the austenite field, the tetragonal L1₀ (2M) martensite, and the 10M and 14M martensite phases with complex multilayer crystal lattices are found. The predominant morphology of martensite is shown to be determined by the hierarchy of the packets of thin coherent lamellae of nano- and submicrocrystalline crystals with planar habit plane boundaries close to {011}_B2. Martensite crystals are twinned along one of the 24 \(24\left\{ {011} \right\}{\left\langle {01\bar 1} \right\rangle _{B2}}\) “soft” twinning shear systems, which provides coherent accommodation of the martensitic transformation–induced elastic stresses.     

Development of the device prototype based on the semiconductor–carbon nanotubes structure for optical radiation detection and study of its parameters

A light-receiving device prototype based on the semiconductor–carbon nanotubes (CNTs) structure consisting of 16 cellular structured sensitive elements grown on the same substrate is developed. The topology of sensitive cells represents holes through metallization and insulator layers to the semiconductor from which the CNT array grows to the top metallization layer. The device prototype parameters are determined as follows: the effective wavelength range is within 400–1100 nm, the operational speed is no longer than 30 μs, the coefficients of peak sensitivity reached at wavelengths of 640 and 950 nm are 197 and 193 μA/W, respectively.     

Effect of additives on structure and corrosion resistance of ceramic coatings on Mg–Li alloy by micro-arc oxidation

In order to improve the corrosion resistance of ceramic coatings formed on Mg–5mass%Li substrate by micro-arc oxidation (MAO) method, two kinds of additives (Na₂B₄O₇ and EDTA) were doped in Na₂SiO₃–Na₃PO₄ solution system. The surface and cross-section morphology feature, phase composition and elemental composition were examined by SEM, XRD and EDX, respectively. Corrosion resistance of ceramic coating was tested by electrochemical methods. It was revealed that all coatings were composed of MgO and Mg₂SiO₄, and had porous surface structure. Doping of additives had little effect on the elemental composition, while it influenced the morphological feature of the coating. The results of electrochemical tests showed that the coatings prepared in the solutions with additive had good corrosion resistance. The addition of EDTA to the solution made coatings thinner and more uniform which resulted in better general corrosion resistance. The addition of Na₂B₄O₇ to the solution made coatings much thicker and compacter, which improved the pitting corrosion resistance.     

Influence of Chemical-Heat Treatment on Thermal Stability of Microstructure,Mechanical Properties and Fracture of V–Cr–Ta–Zr Alloy

Russian Physics Journal - A study of the features of structural-phase state, thermal stability, characteristics of mechanical properties and fracture behavior of V–Cr–Ta–Zr alloy...