Considerations on the Failure Mechanisms at Fatigue Loading of 1018 Steel Samples Coated with Wip-C1 by Cold Spray

There are some important advantages presented by metal specimens coated with WIP-C1 (Ni/CrC)-type materials. However, given the coating methods and the stress under dynamic loads, there are issues that need to be taken into account, particularly in terms of the behavior at the interface between the two materials. Using standardized cylindrical 1018 steel specimens uniformly coated with WIP-C1 (Ni/CrC) by cold spraying, this study investigated the fatigue behavior of the specimen as a whole, focusing on the interface areas of the two materials. The fatigue life diagram is given, to a large extent, by the behavior of the base material. As a result, in this work, we have focused not so much on the fatigue behavior of the assembly as on the integrity of the coating material and the defects, failures, etc., that may occur at the interface after a certain number of cycles. The applied load was cyclic fatigue through alternating-symmetric cycles. Scanning optical microscopy was used to observe plastic deformations and crack propagation during the breakage process. It was found that both the base material zone and the cover material zone presented good performance when the maximum stresses were at low values. A fatigue durability curve was also plotted, showing a conventional appearance for a metallic material, slightly influenced by the destruction of the base material interface. At higher maximum stress and, consequently, to large strains, a series of destructions at the interface of the two materials, of different types, were observed and will be highlighted in the paper.

Investigations on the Degradation Behavior of Processed FeMnSi-xCu Shape Memory Alloys

A new functional Fe-30Mn-5Si-xCu (x = 1.5 and 2 wt%) biomaterial was obtained from the levitation induction melting process and evaluated as a biodegradable material. The degradation characteristics were assessed in vitro using immersion tests in simulated body fluid (SBF) at 37 ± 1 °C, evaluating mass loss, pH variation that occurred in the solution, open circuit potential (OCP), linear and cyclic potentiometry (LP and CP), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and nano-FTIR. To obtain plates as samples, the cast materials were thermo-mechanically processed by hot rolling. Dynamic mechanical analysis (DMA) was employed to evaluate the thermal properties of the smart material. Atomic force microscopy (AFM) was used to show the nanometric and microstructural changes during the hot rolling process and DMA solicitations. The type of corrosion identified was generalized corrosion, and over the first 3-5 days, an increase in mass was observed, caused by the compounds formed at the metal-solution interface. The formed compounds were identified mainly as oxides that passed into the immersion liquid. The degradation rate (DR) was obtained as a function of mass loss, sample surface area and immersion duration. The dynamic mechanical behavior and dimensions of the sample were evaluated after 14 days of immersion. The nanocompounds found on the surface after atmospheric corrosion and immersion in SBF were investigated with the Neaspec system using the nano-FTIR technique.

The Influence of Beverages on Resin Composites: An In Vitro Study

Dental composites, through their structural diversity, represent the biomaterials frequently used in dental reconstructive therapy. The aim of our study was to observe the influence of different beverage environment conditions on seven types of obturation dental materials with different compositions. Our research focused on the surface modification analysis of the materials after the immersion in the different beverages; in this regard, we used the EDAX technique correlated with the energy-dispersive X-ray fluorescence (XRF). The pH of the drinks and that of the simulated saliva solution were determined by the titrimetric method, a sodium hydroxide solution 0.1 mol/dm3 was prepared and used for the titration. An amount of 5 mL of each analyzed solution was added to 15 mL of distilled water to obtain a dilution, to which 3 drops of phenolphthalein (as a color indicator-Phenolphthalein, 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone, C20H14O4 Mw: 318.32, purchased from Merck) were added for each analysis. For each solution, the experiment was repeated three times in order to obtain accurate results. The results of our study materialized into a real plea for modifying the patients' behavior in terms of diet and preferences for acidic drinks, so that their quality-of-life valence can be improved by keeping the composite materials in a long-term unalterable state on the one hand; on the other hand, systemic damage can be prevented as well.

Applications of Recycled and Crushed Glass (RCG) as a Substitute for Natural Materials in Various Fields-A Review

Glass is a substance that is present in most houses since glass-based items are made and consumed in relatively high quantities. This has led to the buildup of glass in concerning quantities all over the world, which is a problem for the environment. It is well known that glass has several advantageous physiochemical features that qualify it as an appropriate material for use in the construction industry as an aggregate. The features include being non-biodegradable, resistant to chemical assault, having low water absorption, having high hydraulic conductivity, having temperature-dependent ductility, having alterable particle gradation, and having a wide availability in a variety of forms and chemical compositions. Because of these qualities, glass has been used in various investigations and field tests conducted in civil engineering to evaluate its effectiveness as an engineering aggregate and to develop environmentally friendly management strategies for waste glass. These studies and research have utilized glass in various forms, such as fine recycled glass, medium recycled glass, coarse recycled glass, powdered glass, and glass-based geopolymers. This study focuses on research studies that present results on physicochemical, mechanical, and durability characteristics. These studies and research contain samples of pure glass or glass as replacement percentages in materials (0-100%), including but not limited to unbound granular materials (such as recycled concrete aggregates and crushed rock). In light of the information assembled in this review article, it is legitimate to claim that glass has strong promise as a material in various civil applications.

Interdisciplinary Research on Medieval Fresco Subjected to Degradation Processes in the Corbii de Piatră Cave Church

This paper presents research on the degradation processes of the fresco painting in the cave church of Corbii de Piatră Hermitage under the influence of meteoric infiltration water and environmental factors. The medieval fresco dates from the end of the 13th century and the beginning of the 14th century, being painted on a sandstone wall. The infiltration of meteoric water through this wall, the temperature variations, the environment and the repeated wetting/drying processes determined the degradation of the fresco, resulting in its detachment from large surfaces. This research established correlations between the processes that take place, the structural transformations, the changes in composition and the adhesion of the fresco to the sandstone wall. The results have been made available to conservation and restoration specialists, in order to choose appropriate materials and technologies. This paper presents findings regarding the pictorial material and introduces new analysis techniques in research on the degradation processes of the fresco painting in the cave church of Corbii de Piatră Hermitage under the influence of meteoric infiltration water and environmental factors.

Analysis of Degradation Products of Biodegradable ZnMgY Alloy

Biodegradable metallic materials are increasingly gaining ground in medical applications. Zn-based alloys show a degradation rate between those recorded for Mg-based materials with the fastest degradation rate and Fe-based materials with the slowest degradation rate. From the perspective of medical complications, it is essential to understand the size and nature of the degradation products developed from biodegradable materials, as well as the stage at which these residues are eliminated from the body. This paper presents investigations conducted on the corrosion/degradation products of an experimental material (ZnMgY alloy in cast and homogenized state) after immersion tests in three physiological solutions (Dulbecco's, Ringer's and simulated body fluid (SBF)). Scanning electron microscopy (SEM) was used to highlight the macroscopic and microscopic aspects of corrosion products and their effects on the surface. An X-ray energy dispersive detector (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) provided general information about the compounds based on their non-metallic character. The pH of the electrolyte solution was recorded for 72 h during immersion. The pH variation of the solution confirmed the main reactions proposed for the corrosion of ZnMg. The agglomerations of corrosion products were on the micrometer scale, mainly oxides, hydroxides and carbonates or phosphates. The corrosion effects on the surface were homogeneously spread, with a tendency to connect and form cracks or larger corrosion zones, transforming the pitting corrosion pattern into a generalized one. It was noticed that the alloy's microstructure strongly influences the corrosion characteristics.

Heat Treatment and Dynamic Mechanical Analysis Strain Sweep Effects on the Phase Structure and Morphology of an Fe-28Mn-6Si-5Cr Shape Memory Alloy

Fe-Mn-Si-based shape memory alloys (SMAs) have been extensively investigated since 1982 for various useful properties that enhance the development of different applications such as anti-seismic dampers for very tall buildings, pipe joints, or rail fasteners. In particular, the Fe-28Mn-6Si-5Cr (mass. %) alloy has been mainly used in vibration mitigation or self-adjustable axial displacement applications. Dynamic mechanical analysis (DMA), performed by strain sweeps (SS), enables the monitoring of the evolution of storage modulus and internal friction variations with increasing strain amplitudes at different constant frequencies and temperatures. Thus, applying dynamic bending with various frequencies and amplitudes that actually represents an isothermal mechanical treatment. In the present paper, an Fe-28Mn-6 Si-5Cr (mass. %) SMA was cast by ingot metallurgy, hot-rolled, and water quenched in order to obtain thermally induced martensite and avoid the occurrence of cooling cracks. The influence of the holding time, between 2 and 10 h, at 1050 °C and the effects of DMA-SS performed at three different frequencies were analyzed by a differential scanning calorimetry, an X-ray diffraction, and a scanning electron and atomic force microscopy. The effects of the holding time and mechanical treatment on the structure and morphology of martensite plates were corroborated with the results of the thermal analysis.

Microstructural and Electrochemical Influence of Zn in MgCaZn Biodegradable Alloys

In recent years, biodegradable materials have included magnesium alloys with homogenous disintegration and a controllable degradation rate. Utilized in medical applications, biodegradable materials based on magnesium have been widely explored throughout the years. It is well-known that alloying Mg with biocompatible and non-toxic elements increases the biodegradability of surgical alloys. The purpose of this study was to examine the microstructure and the electrochemical response (corrosion resistance) of a new experimental Mg-based biodegradable alloy-Mg-0.5%Ca with additions of Zn as follows: 0.5, 1.5, and 3.0 wt.% in order to control the corrosion rate. Immersion tests were performed for different periods in a simulated body fluid electrolyte solution at 37 °C, and the mass loss was appreciated in order to calculate the corrosion rate (CR). The investigation led to the discovery of a dendritic Mg solid solution, a lamellar Mg₂Ca compound, and a MgZn₂ intermetallic phase. Scanning electron microscopy, optical microscopy, and energy dispersive spectroscopy were used for surface analysis after the immersion and electro-corrosion resistance tests. The metallic and ceramic compounds that detached themselves from the sample and passed into the solution were evaluated using the SEM-EDS system. All samples presented a generalized electro-corrosion with anodic and cathodic reactions of similar intensity. The corrosion rate was similar regardless of the percentage of zinc, with a smaller value for a higher than 3 wt.% Zn percentage based on the more protective zinc oxide that appeared on the surface.

Microstructural, Corrosion Resistance, and Tribological Properties of Al2O3 Coatings Prepared by Atmospheric Plasma Spraying

An usual material, EN-GJL-250 cast iron, used for automotive braking systems, was covered with a ceramic material (105NS-1 aluminium oxide) using an industrial deposition system (Sulzer Metco). The main reason was to improve the corrosion and wear (friction) resistance properties of the cast-iron. Samples were prepared by mechanical grinding and sandblasting before the deposition. We applied two and four passes (around 12-15 µm by layer) each at 90° obtaining ceramic coatings of 30 respectively 60 µm. The surface of the samples (with ceramic coatings) was investigated using scanning electron microscopy (SEM), dispersive energy spectroscopy (EDS) and X-ray diffraction (XRD). Scratch and micro-hardness tests were performed using CETR-UMT-2 micro-tribometer equipment. The better corrosion resistance of the base material was obtained by applying the ceramic coating. The results present a better corrosion resistance and a higher coefficient of friction of the coated samples.

Evaluation of the Fatigue Behavior and Failure Mechanisms of 4340 Steel Coated with WIP-C1 (Ni/CrC) by Cold Spray

Fatigue behavior of standardized 4340 steel samples uniformly coated with WIP-C1 (Ni/CrC) by cold spray was investigated. In particular, when a crack appeared at the interface between the base material and the coating, the cause of it as well as its shape and size were investigated. Fatigue loading was applied by alternating symmetrical cycles. Scanning electron microscopy was used to study the onset of failure and the subsequent propagation of cracks. The interface between the two materials performed well-in all samples, the initial crack propagation occurred on the surface of the base material, continuing into the coating material and in the interior of the base material. The fatigue durability curve of stress vs. number of cycles (S-N) presented a conventional form for a metallic alloy and the coating material had an influence only on the damage on the surface of the base material.

Structural Testing by Torsion of Scalable Wind Turbine Blades

In life service, the wind turbine blades are subjected to compound loading: torsion, bending, and traction, all these resulting in the occurrence of normal and tangential stresses. At some points, the equivalent stresses, due to overlapping effects provided by normal and shear stresses, can have high values, close to those for which the structure can reach to the failure point. If the effects of erosion and clashes with foreign bodies are added, the structure of the blade may lose its integrity. Considering both the complex shape of the blade and internal structure used, the mechanical behavior of the blade, such as the rigidity and resistance along the length of the blade, are usually determined with some uncertainty. This paper presents the results obtained in the non-destructive tests at static torsion of a scalable wind turbine blade. The objective of the paper was to determine the variation of the equivalent stress in the most stressed points of the blade, in relation to the torques applied. To determine the points with the highest stress, a finite element analysis was performed on the scalable wind turbine blade. Electrotensiometric transducers were mounted at different points of the blade, determining the main stresses in the respective points, as well as their variation during the torsion test, by subsequent calculations. The determinations were performed by applying the torque in both senses, in relation to the blade axis, thus concluding the values of the equivalent stress in the two cases.

Long-Term Examination of Degradation and In Vivo Biocompatibility of Some Mg-0.5Ca-xY Alloys in Sprague Dawley Rats

The medical field has undergone constant development in recent years, and a segment of this development is occupied by biodegradable alloys. The most common alloys in this field are those based on Mg, their main advantage being the ability to degrade gradually, without affecting the patient, and also their ability to be fully absorbed by the human body. One of their most important conditions is the regeneration and replacement of human tissue. Tissue can be engineered in different ways, one being tissue regeneration in vivo, which can serve as a template. In vivo remodeling aims to restore tissue or organs. The key processes of tissue formation and maturation are: proliferation (sorting and differentiation of cells), proliferation and organization of the extracellular matrix, biodegradation of the scaffold-remodeling, and potential tissue growth. In the present paper, the design of the alloys in the Mg-Ca-Y system is formed from the beginning using high-purity components, Mg-98.5%, master-alloys: Mg-Y (70 wt.%-30 wt.%) and Mg-Ca (85 wt.%-15 wt.%). After 8 weeks of implantation, the degradation of the implanted material is observed, and only small remaining fragments are found. At the site of implantation, no inflammatory reaction is observed, but it is observed that the process of integration and reabsorption, over time, accentuates the prosaic surface of the material. The aim of the work is to test the biocompatibility of magnesium-based alloys on laboratory rats in order to use these alloys in medical applications. The innovative parts of these analyses are the chemical composition of the alloys used and the tests performed on laboratory animals.

Biosorption Potential of Microbial and Residual Biomass of Saccharomyces pastorianus Immobilized in Calcium Alginate Matrix for Pharmaceuticals Removal from Aqueous Solutions

Two types of biosorbents, based on Saccharomyces pastorianus immobilized in calcium alginate, were studied for the removal of pharmaceuticals from aqueous solutions. Synthetized biocomposite materials were characterized chemically and morphologically, both before and after simulated biosorption. Ethacridine lactate (EL) was chosen as a target molecule. The process performance was interpreted as a function of initial solution pH, biosorbent dose, and initial pharmaceutical concentration. The results exhibited that the removal efficiencies were superior to 90% for both biosorbents, at the initial pH value of 4.0 and biosorbent dose of 2 g/L for all EL initial concentrations tested. Freundlich, Temkin, Hill, Redlich-Peterson, Sips, and Toth isotherms were used to describe the experimental results. The kinetic data were analyzed using kinetic models, such as pseudo-first order, pseudo-second order, Elovich, and Avrami, to determine the kinetic parameters and describe the transport mechanisms of EL from aqueous solution onto biosorbents. Among the tested equations, the best fit is ensured by the pseudo-second-order kinetics model for both biosorbents, with the correlation coefficient having values higher than 0.996. The many potential advantages and good biosorptive capacity of Saccharomyces pastorianus biomass immobilized in calcium alginate recommend these types of biocomposite materials for the removal of pharmaceuticals from aqueous solutions.

Morphological Analysis of Laser Surface Texturing Effect on AISI 430 Stainless Steel

Laser surface texturing (LST) is a method to obtain micro-structures on the material’s surface for improving tribological performances, wetting tuning, surface treatment, and increasing adhesion. The material selected for LST is AISI 430 ferritic stainless steel, distinguished by the low cost in manufacturing, corrosion resistance, and high strength at elevated temperature. The present study addresses the morphology of new pattern designs (crater array, ellipse, and octagonal shapes). The patterns are applied on the stainless-steel surface by a non-contact method with high quality and precision nanosecond pulsed laser equipment. The investigation of laser parameter influence on thermal affected area and micro-structures is accomplished by morphological and elemental analysis (SEM + EDX). The parameters of the laser micro-patterning have a marked influence on the morphology, creating groove-type sections with different depths and recast material features. From the SEM characterization, the highest level of recast material is observed for concentric octagon LST design. Its application is more recommended for the preparation of the metal surface before hybrid welding. Additionally, the lack of the oxygen element in the case of this design suggests the possible use of the pattern in hybrid joining.

Evaluation of the Fatigue Behaviour and Failure Mechanisms of 52100 Steel Coated with WIP-C1 (Ni/CrC) by Cold Spray

Cold spray technique has been major improved in the last decades, for studying new properties for metals and alloys of aluminum, copper, nickel, and titanium, as well as steels, stainless steel and other types of alloys. Cold sprayed Ni/CrC coatings have the potential to provide a barrier as well as improved protection to steels. Fatigue characteristics of 52100 steel coated with Ni/Chrome-Carbide (Ni/CrC) powder mixture by using cold gas dynamic spray are investigated. Fatigue samples were subjected to symmetrically alternating, axially applied cyclic fatigue loading until failure. The test was stopped if a sample survived more than 5 × 106 cycles at the applied stress. Fracture surfaces for each sample were examined to investigate the behaviour of the coating both at high stress levels and at a high number of stress cycles. Scanning electron microscopy was used to assess the damage in the interface of the two materials. Good fatigue behaviour of the coating material was observed, especially at low stresses and a high number of cycles. Details of the crack initiation region, the stable crack propagation region and the sudden crack expansion region are identified for each sample. In most of the samples, the initiation of the crack occurred on the surface of the base material and propagated into the coating material. The possible effects of coatings on the initial deterioration of the base material and the reduction of the lifespan of the coated system were also investigated. The aim of the paper was to study the interface between the base material and the coating material at the fatigue analysis for different stresses, highlighting the appearance of cracks and the number of breaking cycles required for each sample.

Novel Mg-0.5Ca-xMn Biodegradable Alloys Intended for Orthopedic Application: An In Vitro and In Vivo Study

Mg-based biodegradable materials, used for medical applications, have been extensively studied in the past decades. The in vitro cytocompatibility study showed that the proliferation and viability (as assessed by quantitative MTT-assay-3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide) were not negatively affected with time by the addition of Mn as an alloying element. In this sense, it should be put forward that the studied alloys don't have a cytotoxic effect according to the standard ISO 10993-5, i.e., the level of the cells' viability (cultured with the studied experimental alloys) attained both after 1 day and 5 days was over 82% (i.e., 82, 43-89, 65%). Furthermore, the fibroblastic cells showed variable morphology (evidenced by fluorescence microscopy) related to the alloy sample's proximity (i.e., related to the variation on the Ca, Mg, and Mn ionic concentration as a result of alloy degradation). It should be mentioned that the cells presented a polygonal morphology with large cytoplasmic processes in the vicinity of the alloy's samples, and a bipolar morphology in the remote region of the wells. Moreover, the in vitro results seem to indicate that only 0.5% Mn is sufficient to improve the chemical stability, and thus the cytocompatibility; from this point of view, it could provide some flexibility in choosing the right alloy for a specific medical application, depending on the specific parameters of each alloy, such as its mechanical properties and corrosion resistance. In order to assess the in vivo compatibility of each concentration of alloy, the pieces were implanted in four rats, in two distinct body regions, i.e., the lumbar and thigh. The body's reaction was followed over time, 60 days, both by general clinical examinations considering macroscopic changes, and by laboratory examinations, which revealed macroscopic and microscopic changes using X-rays, CT(Computed Tomography), histology exams and SEM (Scanning Electron Microscopy). In both anatomical regions, for each of the tested alloys, deformations were observed, i.e., a local reaction of different intensities, starting the day after surgery. The release of hydrogen gas that forms during Mg alloy degradation occurred immediately after implantation in all five of the groups examined, which did not affect the normal functionality of the tissues surrounding the implants. Imaging examinations (radiological and CT) revealed the presence of the alloy and the volume of hydrogen gas in the lumbar and femoral region in varying amounts. The biodegradable alloys in the Mg-Ca-Mn system have great potential to be used in orthopedic applications.

Sustainable Functionalization of PAN to Improve Tinctorial Capacity

This study may open a new way to obtain the coloration of a polymer during functionalization. Two polyacrylonitrile (PAN) polymers in the form of textile fibers (Melana and Dralon L) were subjected to functionalization treatments in order to improve the dyeing capacity. The functionalizations determined by an organo-hypervalent iodine reagent developed in situ led to fiber coloration without using dyes. KIO3 was formed in situ from the interaction of aqueous solutions of 3-9% KOH with 3-9% I2, at 120 °C. The yellow-orange coloration appeared as a result of the transformations in the chemical structure of each functionalized polymer, with the formation of iodinehydrin groups. The degree of functionalization directly influenced the obtained color. The results of the Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Map and Temogravimetric Analysis (TG) plus Differential Thermal (DTA) analyses indicated the presence of new functional groups, such as iodine-oxime. The X-ray diffraction (XRD) analysis confirmed the change of the crystalline/amorphous ratio in favor of the former. The new groups introduced by functionalization make it possible to dye with classes of dyes specific to these groups, but not specific to PAN fibers, thus improving their dyeing capacity.

Experimental EDX analysis of different periodontal splinting systems

Physiological/normal tooth mobility may be defined as the slight displacement of the clinical crown of a tooth, which is allowed by the resilience of an intact and healthy periodontium, under the application of a moderate force. The factors influencing the success and longevity of dental splinting are the type of material used for the splint, the type of composite resin, the number and location of the dental units included for splinting (maxillary or mandibular arch). In periodontology, the term 'splint' is defined as the joining of two or more teeth into a rigid unit through restorations or fixed or removable devices. The purpose of using periodontal splints for tooth immobilization is to provide a period of rest in the areas where the healing process has begun and to allow normal functioning there where the tissues alone would not be able to withstand occlusal forces. The aim of the present study was to evaluate comparatively, by means of energy dispersive electron spectrometry (EDX), the chemical composition in the case of in vitro samples that structurally reproduce direct periodontal immobilization systems using fiberglass strips and fluid composite resins. The differences in the chemical composition of the investigated materials can influence their physiochemical properties, but also their biological and toxicological reliability. Elements such as C, O, Al, Si and Ba were identified as common elements among the resins tested in the present study. The only difference in terms of the component elements was found in the case of the fluid composite Clearfil Majesty ES Flow, which, apart from the elements mentioned, also presented Co in its structure.

Eco-Friendly Biosorbents Based on Microbial Biomass and Natural Polymers: Synthesis, Characterization and Application for the Removal of Drugs and Dyes from Aqueous Solutions

Pharmaceuticals and dyes are a very important part of the nonbiodegradable or hard biodegradable substances present in wastewater. Microorganisms are already known to be effective biosorbents, but the use of free microbial cells involves difficulties in their separation from effluents and limits their application in wastewater treatment. Thus, this study aimed to develop biosorbents by immobilizing Saccharomyces cerevisiae, Saccharomyces pastorianus and Saccharomyces pastorianus residual biomass on natural polymers (alginate and chitosan) and to evaluate the biosorptive potential for removal of pharmaceuticals and dyes from water. Six types of biosorbents were synthesized and characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy techniques and their biosorptive capacities for three drugs (cephalexin, rifampicin, ethacridine lactate) and two dyes (orange II and indigo carmine) were evaluated. The obtained results show that the removal efficiency depends on the polymer type used for the immobilization. In case of alginate the removal efficiency is between 40.05% and 96.41% for drugs and between 27.83% and 58.29% for dyes, while in the case of chitosan it is between 40.83% and 77.92% for drugs and between 17.17% and 44.77% for dyes. In general, the synthesized biosorbents proved to be promising for the removal of drugs and dyes from aqueous solutions.

Evaluation of the Corrosion Resistance of Some Coating Obtained by Thermal Spray in Plasma Jet, on the Surface of Some Crankshafts Made of C45 Steel

For modern engines the oil change interval can reach up to 30,000 km. If the oils lose their properties and are contaminated, they can adversely affect the corrosion resistance, the surface of the main bearing journals and the main journals of the crankshafts. In this study, the results obtained from the corrosion process were analyzed, in a solution of 3.5% NaCl of the layers obtained after spraying the surface of a C45 steel, used in the construction of crankshafts, with three powders: Cr3C2-(Ni20Cr), Al2O3-13TiO2, Cr2O3-SiO2-TiO2. The corrosion process was determined by the potentiodynamic polarization technique. The variations in time of the open-circuit potential and the Tafel curves were analyzed, for the samples with deposited layers and the basic material. Morphology and characterization of the structure of the layers after corrosion were performed by means of SEM microscopy and EDAX analysis. The results confirm that the powders sprayed by the atmospheric plasma spray method protect the surface of C45 steel from corrosion.

Electrochemical Analysis and In Vitro Assay of Mg-0.5Ca-xY Biodegradable Alloys

In recent years, biodegradable Mg-based materials have been increasingly studied to be used in the medical industry and beyond. A way to improve biodegradability rate in sync with the healing process of the natural human bone is to alloy Mg with other biocompatible elements. The aim of this research was to improve biodegradability rate and biocompatibility of Mg-0.5Ca alloy through addition of Y in 0.5/1.0/1.5/2.0/3.0wt.%. To characterize the chemical composition and microstructure of experimental Mg alloys, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM), and X-ray diffraction (XRD) were used. The linear polarization resistance (LPR) method was used to calculate corrosion rate as a measure of biodegradability rate. The cytocompatibility was evaluated by MTT assay (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide) and fluorescence microscopy. Depending on chemical composition, the dendritic α-Mg solid solution, as well as lamellar Mg₂Ca and Mg₂₄Y₅ intermetallic compounds were found. The lower biodegradability rates were found for Mg-0.5Ca-2.0Y and Mg-0.5Ca-3.0Y which have correlated with values of cell viability. The addition of 2-3 wt.%Y in the Mg-0.5Ca alloy improved both the biodegradability rate and cytocompatibility behavior.

Electrochemical Evaluation of Some Mg-Ca-Mn-Zr Biodegradable Alloys

Biodegradable magnesium alloys represent a class of materials with high properties that are used in a wide range of fields, such as medicine, aeronautics and automotive. Alloying the Mg-based alloys with small percentages of elements such as Ca, Mn and Zr can conduct to the obtaining of some materials that can be the basis for the development of orthopedic implants. Calcium contributes to the formation of the Mg2Ca lamellar compound, low concentrations of zirconium helps the microstructure refinement and corrosion resistance and the alloying with manganese leads to the increase of the mechanical characteristics.In this paper, the electrochemical behaviour of four biodegradable alloys from the Mg-Ca-Mn-Zr system was evaluated, with variable concentrations (0.5% -1%) of Mn, respectively Zr. Alloying the system with 1% of each element (Ca, Mn, Zr) led to the obtaining of the alloy with the highest corrosion resistance and the lowest degradation rate.

The Influence of Zr on Microstructure, Mechanical Properties and Corrosion Resistance in Mg-Y-Zr Biodegradable Alloys

The latest magnesium alloys are widely used in the medical field, especially for biodegradable implants. Magnesium alloys are very attractive for applications in different structures in the automotive, aerospace, printing and even medical fields [1]. It should be noted that some magnesium alloys have excellent damping properties as well as good mechanical properties, making them promising to respond to high damping needs for vibration control [1,2]. Although widely used, magnesium has a low corrosion resistance. To improve this resistance, different types of magnesium based on aluminum, such as Ca, Mn, Zn, Zr, Si and rare rare (Y, Gd ..), can be developed. The main purpose of this paper is to investigate the properties of a primary alloy based on the Mg-1Y-0,5Zr system with different concentrations of Zr (0.5,1,2) used in the development of alloys based on the biodegradability of Mg. Surface morphology was characterized by electronic scanning microscopy (SEM), X-ray diffraction (XRD) and optical microscopy. After XRD analysis, it was observed that certain specific compounds were made up of Mg2Ca, MgZr, Mg2Y, Mg24Y5 having the main Mg formed in the hexagonal structure, but Mg24Y5 are the cubic crystalline structure. Also, the microhardness of the alloy is higher than pure Mg and the scratch mark is smaller than that of pure Mg. The corrosion resistance was developed using linear voltammetry in specific medium and corrosion showed that it had significantly decreased for masteralloy. As a final conclusion, the structural properties of this model are recommended for use as medical implants.

Electro-chemical Corrosion of a Cast Iron Protected with a Al2O3 Ceramic Layer

Thin layers of Al2O3 were used to protect a standard FC250 cast iron at electro-corrosion in acid rain electrolyte solution. In comparison with a cast-iron material we present the results obtained on the metallic covered sample using linear and cyclic potentiometry. The material surface was investigated using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The results present a generalized corrosion with a higher resistance for covered samples (more than 30 times) in comparison with the simple cast iron. The main causes of the corrosion of the covered samples are based on the thin ceramic layer imperfections like pores or micro-cracks that facilitate the contact of the electrolyte solution with the metallic substrate.

Chemical Composition Influence on Microhardness, Microstructure and Phase Morphology of AlxCrFeCoNi High Entropy Alloys

The AlCrFeCoNi high entropy alloy exhibits unexpected properties that can be obtained after mixing five different elements, which could not be obtained from any one independent element. The difference to conventional alloys is that these alloys may have, at the same time, both hardness and plasticity, can be used in severe impact applications. In order to study the influence of aluminum content on the microhardness and microstructure of the high entropy alloys AlxCrFeCoNi (x: atomic ratio, x= 0.2 to 2.0) nine types of samples were obtained as mini-sized ingots (50x15x9.5 mm and 40 g weight). The mini-ingots were obtained using arc melt casting process in a vacuum arc remelting device (VAR MRF ABJ 900). The influence of the chemical elements on the microstructure, phases morphology and microhardness of AlxCrFeCoNi system was studied. The results have confirmed that mechanical properties could be greatly adjusted by the chemical composition change. The main element that influences the microhardness of the analyzed system is aluminum, due to the formation of Al-Fe compounds with high hardness. Increasing the aluminum content in the alloy to values greater than 1.8 ... 2 at.% contribute to the increase of hardness and also to the embrittlement thereof. Other elements like Cr, Fe, Co and Ni can contribute to mitigate increasing the hardness of the alloy. The type of phases formed in high entropy alloy are dependent to the aluminum concentration. So, depending on of aluminium content, different phases are obtained, like FCC for low Al content, mixture of FCC and BCC for about 2.5 %Al and BCC for high Al content. The crystallite size depends on the chemical composition and increase with the aluminium content.

Comparative Evaluation of Hardness and Elasticity Modulusof Tooth-Colored Materials for Dental Restoration

The aim of this study was to compare Rockwell hardness (HRC) and modulus of elasticity (Young modulus) to different restorative materials. Three commercial composite resins: Filtek Z250 (3M ESPE Co.), Zmack Comp (Zermack SpA, Italy), Kalore (GC Corporation, Japan) and one compomer: Dyract eXtra (Dentsply De Trey Gmbh, Germany) were used. Six samples of each material were obtained by placing them in plastic rings having 5 mm inner diameter and 6 mm high. All composite samples were cured for 40 s using a lamp LEDidition - Ivoclaire Vivadent clinical, Austria. The samples were finished and polished and then stored in distilled water, at room temperature for 48 hours. Rockwell Hardness (HRC) measurements were realized using the UMT-2 Tribometer (CETR). The hardness was automatically calculated from the slope of unloading curve and expressed in GPa and transformed in HRC values (kgf/mm2). Six indentations were performed on diametral direction and mean values were calculated for all tested samples. The device also measured the modulus of elasticity for each sample. Data were analyzed by ANOVA and Mann-Whitney test (significance level of p [ 0.05). The mean HRC values were the following: Filtek Z250 ] Zmack Comp ] Dyract eXtra ] Kalore (82.98 ] 70.10 ] 53.27 ] 37.72 kg/mm2). Regarding Young modulus, the rank from highest to lowest as follows: FiltekZ250 ] Zmack Comp ] Dyract eXtra ] Kalore (16.24 ] 14.05 ] 12.41 ] 7.86). The microhydrid composite resins have a significantly higher hardness than nano-hybrid composites or compomers.

Characterization of Some Master Mg-X System (Ca, Mn, Zr, Y) Alloys Used in Medical Applications

Ultralight magnesium alloys are wide used in the medical field, especially for biodegradable implants. Although they are wide used, magnesium has low corrosion resistance. To improve this resistance, different types of alloys based on magnesium and Ca, Mn, Zr and Y can be developed. The main goal of the present paper is to investigate the properties of some master alloy based on Mg-X system (Ca ,Mn, Zr, Y) used in the development of biodegradable based alloys of Mg. The surface morphology was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and optical microscopy. After the XRD analysis, there was observed that some specific compounds were formed of Mg2Ca, Mg0.97Mn0.025, MgZr, Mg2Y, Mg24Y5 having the main Mg phase formed in the hexagonal structure. There were also evaluated the master alloys micro-hardness values in the range of 58.41 HV (Pure Mg), 67.97 HV (Mg-3Mn), 85.12 HV (Mg-25Zr), 131.8 HV (Mg-15Ca) and 291.45 HV (Mg-30Y). The corrosion resistance was developed using electrochemical testing in specific medium and there is shown that the corrosion rate increased significantly for the master alloys investigated, rather than pure magnesium. As a final conclusion structural properties of these alloys recommend them for usage as medical implants.

Algorithmic approaches to protein-protein interaction site prediction

Interaction sites on protein surfaces mediate virtually all biological activities, and their identification holds promise for disease treatment and drug design. Novel algorithmic approaches for the prediction of these sites have been produced at a rapid rate, and the field has seen significant advancement over the past decade. However, the most current methods have not yet been reviewed in a systematic and comprehensive fashion. Herein, we describe the intricacies of the biological theory, datasets, and features required for modern protein-protein interaction site (PPIS) prediction, and present an integrative analysis of the state-of-the-art algorithms and their performance. First, the major sources of data used by predictors are reviewed, including training sets, evaluation sets, and methods for their procurement. Then, the features employed and their importance in the biological characterization of PPISs are explored. This is followed by a discussion of the methodologies adopted in contemporary prediction programs, as well as their relative performance on the datasets most recently used for evaluation. In addition, the potential utility that PPIS identification holds for rational drug design, hotspot prediction, and computational molecular docking is described. Finally, an analysis of the most promising areas for future development of the field is presented.

Transient protein-protein interface prediction: datasets, features, algorithms, and the RAD-T predictor

Background

Transient protein-protein interactions (PPIs), which underly most biological processes, are a prime target for therapeutic development. Immense progress has been made towards computational prediction of PPIs using methods such as protein docking and sequence analysis. However, docking generally requires high resolution structures of both of the binding partners and sequence analysis requires that a significant number of recurrent patterns exist for the identification of a potential binding site. Researchers have turned to machine learning to overcome some of the other methods’ restrictions by generalising interface sites with sets of descriptive features. Best practices for dataset generation, features, and learning algorithms have not yet been identified or agreed upon, and an analysis of the overall efficacy of machine learning based PPI predictors is due, in order to highlight potential areas for improvement.

Results

The presence of unknown interaction sites as a result of limited knowledge about protein interactions in the testing set dramatically reduces prediction accuracy. Greater accuracy in labelling the data by enforcing higher interface site rates per domain resulted in an average 44% improvement across multiple machine learning algorithms. A set of 10 biologically unrelated proteins that were consistently predicted on with high accuracy emerged through our analysis. We identify seven features with the most predictive power over multiple datasets and machine learning algorithms. Through our analysis, we created a new predictor, RAD-T, that outperforms existing non-structurally specializing machine learning protein interface predictors, with an average 59% increase in MCC score on a dataset with a high number of interactions.

Conclusion

Current methods of evaluating machine-learning based PPI predictors tend to undervalue their performance, which may be artificially decreased by the presence of un-identified interaction sites. Changes to predictors’ training sets will be integral to the future progress of interface prediction by machine learning methods. We reveal the need for a larger test set of well studied proteins or domain-specific scoring algorithms to compensate for poor interaction site identification on proteins in general.

[Aspects of molecular immunology and immunogenetics in autoimmune uveitis]

Generally speaking, the uveitis comprises a relative complex group of autoimmune diseases or other autoimmune associated illness. Until now, a little from molecular and cellular mechanisms are known in the autoimmunity of uveitis. The uveitis may cause a visual handicap as well, leading even to blindness. This paper tries to bring into focus some of the molecular mechanisms and immunogenetic features of the disease.

[Immunological aspects in glaucoma]

Glaucoma is one of the most frequent causes of vision loss and blindness. The increased intraocular pressure does not explain glaucoma in all patients but can be considered as a risk factor of the disease. It seems that systemic immunity of the eye through up-and-down immunological regulation of autoantibodies against ocular antigens make their impact felt on glaucoma patients too. The cells from retinal ganglion and aqueous humor itself can be the aperture selection of ocular immune response involved in glaucoma pathogenesis. Among its multiple functions, the immune system confers a protective action on retinal neurons. It is very important the immune maintenance in glaucoma, which involves on the other side the activity of immunoprotection and neuroprotection factors.