Materials technology

In this study, the effect of copper coated particles on the properties of CoCrFeNi and AlCoCrFeNi high entropy alloys (HEAs) was studied. Mechanical milling is applied to achieve a good homogeneous distribution of an equiatomic CoCrFeNi and AlCoCrFeNi HEAs for 25 h milling time, followed by an electroless copper plating with 5e20 wt.% Cu by 5 wt.%, have been established. The prepared powder alloys were compacted at 800 MPa, then sintered at 1150 C, 1200 C, 1250 C for Cu x /(CoCrFeNi) 1-x HEA and 900 C, 950 C, and 1000 C for Cu x /(AlCoCrFeNi) 1-x HEA in a vacuum furnace for 90 min. The correlation between the microstructure, density, hardness, wear behavior and corrosion resistance of the fabricated CoCrFeNi, Cu x /(CoCrFeNi) 1-x and Cu x /(AlCoCrFeNi) 1-x HEAs were investigated. The results revealed that, alloys which sintered at 1200 C for (CoCrFeNi e Cu x /(CoCrFeNi) 1- x HEAs) and at 950 C for (Cu x /(AlCoCrFeNi) 1-x HEA) exhibit the highest relative density. Densification was enhanced as a result of increasing the nano Cu wt.% content. A dramatic decrease in the produced samples' hardness was observed where it decreased from 189.1 HV to 134.5 HV for Cu x /(CoCrFeNi) 1-x and from 403 HV to 191 HV for Cu x /(AlCoCrFeNi) 1-x HEAs by the addition of the nano Cu wt.% content. In addition, Wear rate is increased gradually by the addition of the nano Cu wt.% content. The electrochemical results indicate that an increased nano Cu wt.% content corresponds to an increased corrosion rate from 0.297 mm/year to 1.84 mm/year for Cu x /(CoCrFeNi) 1-x and from 0.03 mm/year to 0.093 mm/ year for Cu x /(AlCoCrFeNi) 1-x HEAs.

The iron catalyst nanoparticles were prepared on silicon wafers by solution process, which first spins coat the solution of iron (III) nitrate nonahydrate and colloidal solution, and then are heated to obtain the formation of iron nanoparticles. The effects of different spin speed and heat treatment parameters during the solution process were investigated. As a result, the smallest thickness of the Fe catalyst thin films is 78 nm, and the smallest Fe catalyst nanoparticles, i.e. 9?67 nm, were obtained at the highest spin speed of 8000 rev min 21 and 500uC. The uniformity of the thin films was also found to increase with increasing spin speed. The particle and thickness analysis was performed by means of field emission scanning electron microscopy.

The iron catalyst nanoparticles were prepared on silicon wafers by solution process, which first spins coat the solution of iron (III) nitrate nonahydrate and colloidal solution, and then are heated to obtain the formation of iron nanoparticles. The effects of different spin speed and heat treatment parameters during the solution process were investigated. As a result, the smallest thickness of the Fe catalyst thin films is 78 nm, and the smallest Fe catalyst nanoparticles, i.e. 9?67 nm, were obtained at the highest spin speed of 8000 rev min 21 and 500uC. The uniformity of the thin films was also found to increase with increasing spin speed. The particle and thickness analysis was performed by means of field emission scanning electron microscopy.

Tellurite glasses are considered a potential alternative for applications not achieved by SiO 2 -based glasses, presenting interesting optical properties, such as high linear and nonlinear refractive indexes, extended optical window, being also suitable for metallic nanoparticle growth, like Te 0 . When doped with sulfide species, it can benefit the reduction of Te 4þ to Te 0 , which can be advantageous to synthesize in-situ chalcogenide nanoparticles and quantum dots. This work presents investigations on the reduction of Te 4þ to Te 0 in tellurite glasses doped with PbS and PbO/ZnS, and aims to control this redox process through the processing with pulsed fs-laser. Tellurite glass samples were synthesized by melt-quenching technique and the thermal and structural properties were explored by different techniques, such as DSC, Raman scattering spectroscopy and mapping experiment, TEM and SAED. Reduction of tellurium to Te 0 nanocrystals into tellurite glass after laser irradiation was studied in detail and confirmed by the presence of bands at ~120 and 140 cm À1 in Raman spectroscopy and mapping, assigned to the TeeTe vibrational modes, which suggest that S 2À induces in-situ Te 4þ reduction. Moreover, quasi spherical tellurium nanoparticles were observed through TEM and confirmed their chemical nature and crystallization by SAED. The study of tellurium reduction in the vitreous matrix becomes particularly important and promising for some applications, since its reduction generates changes in the refractive index by precipitation of Te 0 nanoparticles, allowing the fabrication of waveguides and as photosensitive material for tridimensional data storage.

The benefits of the electrical-based biosensor include cheap production and fast response time of detecting diseases. An interdigitated electrode (IDE) is fabricated using silver (Ag) as a metal contact that is deposited on aliminium (Al) nanoparticles doped with both zinc oxide (ZnO) and Silicon (Si) forming AZO/Si nanostructures by vacuum coater in a thermal evaporator. The electrical properties are studied as a function of frequency and voltage using I-V characteristics. Sol-gel method under annealing temperature, 500 • C is utilized to generate Al nanoparticles doped ZnO nanostructures. UV-vis spectrophotometer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray diffractometer (XRD) are used for analyzing optical, topographical, morphological and structural studies of AZO nanostructure, respectively. Specific empirical models of optical dielectric constant, bulk modulus and refractive index are also verified.

Abstract Currently, growing interest exists in the development of packaging materials of natural origin for food applications. This study, conducted the extraction of pigments from natural sources (anthocyanin and betanin) from the exocarp of the black eggplant (Solanum melongena) and the mesocarp of beet (Beta vulgaris), which were incorporated in a film-forming solution based on sodium alginate and starch, as an indicator of films with natural pigment extract (FNE). In consequence, the objective of this work was to assess the effect caused by incorporating extracts of natural origin on the mechanical, optical, and structural properties of sodium alginate/yucca starch films. The films were elaborated with different concentrations of each pigment extracted (2% and 5%) and compared with a control film (CF). The films were exposed to a series of synthetic amines and the changes were observed in the UV-vis absorption spectra. In addition, the effect was evaluated when adding extracts from natural pigments into a polymer matrix, evaluating the mechanical, structural, and optical properties. The results showed that incorporation of natural extracts (NE) influenced on the mechanical properties, but did not influence on film thickness and water vapor permeability (WVP). X-ray diffraction (XRD) indicated increased film crystallinity when incorporating the natural extracts. The microstructure Fourier transform infrared analyses of the films showed that the extracts were compatible with the polymer matrix. Films with eggplant extract (FEE) had higher antioxidant activity against the 1,1-Diphenyl-2-picryl-hydrazyl (DPPH) radical and were more sensitive to the exposure of gaseous amines in comparison with films with beet extract (FBE). Hence, the results obtained show that the films developed with natural compounds are a visual method that could report and monitor the state of the foods.

Ce travail n'aurait pas été réalisé sans l'aide de nombreuses personnes envers lesquels je suis reconnaissant. J'exprime toute ma gratitude aux professeurs Sandrine THUILLIER et Didier CHICOT, d'avoir acceptés de rapporter mes travaux de thèse. J'exprime, de même, mes remerciements au professeur David GLOAGUEN d'avoir accepté d'être président de mon jury de thèse. Je tiens à exprimer mes plus vifs remerciements à Gérard MAUVOISIN qui fut pour moi un directeur de thèse attentif et disponible malgré ses nombreuses charges. Sa compétence, sa rigueur scientifique et sa clairvoyance m'ont beaucoup appris. Je tiens à le remercier pour tous les efforts et le temps qu'il a consacré pour faire avancer ce projet. Je tiens à remercier énormément Olivier BARTIER, pour son encadrement, sa disponibilité et bien sûr ses compétences scientifiques remarquables. Je retiens en particulier ses qualités humaines, sa vision de la science et son enthousiasme. Son soutien, sa clairvoyance et ses compétences m'ont été d'une aide inestimable. Je dois de même le remercier pour tout le temps qu'il a consacré pour lire et corriger mes rapports semestriels et mes présentations et surtout pour tout l'effort qu'il a consacré pour les corrections de ce mémoire de thèse. Je vais m'arrêter là car je sais bien que quelques lignes de remerciements ne suffiront pas pour le remercier. J'exprime mes remerciements de même à Xavier HERNOT pour son encadrement et pour ses conseils scientifiques importants. Je n'oublierai jamais son enthousiasme pour la science, son esprit critique, ses compétences intellectuelles et mathématiques. Je le laisse avec plein de choses qu'on a commencé ensemble sans pouvoir les finaliser. J'espère pouvoir publier avec lui tout ce qui a été commencé. Toute ma gratitude va aussi à ESI-Group d'avoir financé ce projet pendant ces trois années. Je tiens à remercier tout particulièrement mon encadrant industriel Pascal LONGRAIS pour son esprit rigoureux, scientifique et clairvoyant. Je n'oublie pas de remercier de même Eddie GAZO HANNA pour son aide et ses conseils. Je tiens de même à remercier tous les collègues que j'ai eu l'occasion de rencontrer pendant ces années de thèse : je note tout particulièrement, Michel YETNA N'JOCK, Charbel MOUSSA ainsi que Walid NASRI. Je remercie tout particulièrement Liva RABEMANANJARA ; un collègue mais encore un ami avec des qualités humaines exceptionnelles. Je tiens à remercier tous les membres du LGCGM pour leur accueil chaleureux et pour leur esprit amical. Enfin mes derniers remerciements, qui n'en sont pas pour autant les moins importants, vont à mon frère Afif, à ma soeur Dana, à mes meilleurs amis (Mahmoud HASSAN, Ahmad MHEICH, Mahmoud ISRAEL, Anas HASSAWI, Mohamad SHAMAS, Imad ALAWE…). iii Titre : Apport de l'indentation instrumentée dans la caractérisation mécanique des tôles métalliques destinées à l'emboutissage : influence de l'écrouissage Avec les nouvelles nuances de matériaux utilisées dans le but de l'allègement des structures automobiles, la prédiction du retour élastique de ces matériaux après leur mise en forme par emboutissage devient de plus en plus difficile. La solution est de prévoir le comportement mécanique de ces matériaux. Les travaux de cette thèse consistent à examiner ce que peut apporter l'essai d'indentation instrumentée dans la caractérisation mécanique de tôles destinées à l'emboutissage ; notamment la capacité de l'essai d'indentation instrumentée à déterminer l'état d'écrouissage d'un matériau pré-déformé. Tout d'abord, le caractère local de l'essai d'indentation a permis de mettre en évidence la variation des propriétés mécaniques dans l'épaisseur des tôles. Différentes lois d'écrouissage ont ainsi pu être identifiées à différents endroits de la section de la tôle.

The uniform and localized corrosion behaviour of sintered Ti-Ni containing niobium and copper additions were studied using potentiodynamic and cyclic polarization measurements in 0.9% sodium chloride. Results indicated that copper and niobium addition did not have significant effects on the uniform corrosion characteristics, but significantly improved the pitting corrosion resistance. Both copper and niobium additions significantly increased the re-passivation potentials, while copper was observed to reduce the pitting hysteresis loop area. Alloys containing 15% copper and 2% niobium additions depicted the most improved pitting corrosion resistance, and increased the re-passivation value from -315.60 mV to a high re-passivation potential of 840.68 mV.

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The objective of this paper is to present a comprehensive study of the effects of ball burnishing on the low cycle fatigue endurance of cylindrical specimens subjected to alternative bending stress, by constructing fatigue S-N curves to evaluate the impact of the process on the general fatigue behavior of AISI 1038. The specimens were burnished through five different force-number of passes couples, displacing the as-machined-material S-N curve towards higher lifespans as the degree of cold work is increased, either by effect of a higher force and more burnishing passes. The derived surface hardening effect also proved to be correlated analytically with the fatigue lifespan increase at all tested maximum-stress levels, as prove the correlation of the parameters that represent the potential equation associated to the Wöhler model with the hardening effect. It is concluded that the process performed with 120 N and 7 passes results in the most favorable results, represented by a 41% increase of hardness and a 77% increase in the lifespan in the best of cases.

Numerous simplified numerical models have been established to optimize the ball burnishing of steel surfaces. Nevertheless, their conceptualization has not considered the toolepart interaction, leading to an unsatisfactory process parameterization. As a solution, a structured numerical simulation has been defined that reproduces this interaction by several friction coefficient approximations. This study provides the tribological process inputs (friction and initial surface conditions) to this model, adapting it to a pre-textured martensitic precipitation hardening stainless-steel. Results show the versatility of the model to reproduce the surface integrity alterations. Hence, this consistent model configuration can be postulated as an economical and efficient approach to tackle ball burnishing parameterization according to the applicability of the manufactured steel parts.

Congenital abnormalities are worldwide major health problem. One of these abnormalities is; cleft lip and palate. Such a condition when occur, it can affect the child and provoke physiological and psychological consequences. One of the desired and sparkling line of treatment is stem cells engineering. There are many different types of stem cells. The most popular stem cells used in craniofacial treatment are; bone marrow derived mesenchymal stem cells (BM-MSCs) and adipose tissue derived mesenchymal stem cells (AT-MSCs). Although both showed positive results, still there are few comparative studies that evaluate the effectiveness of AT-MSCs over BM-MSCs. The purpose of this review was to provide an overview of stem cells and their clinical uses, and to compare the effectiveness of BM-MSCs and AT-MSCs in cleft lip and alveolus patients. Electronic search of English scientific papers from 2000 to 2017 was accomplished using PubMed, Cochrane Database and Google Scholar search engines. The following search terms used were, Cleft Lip and Palate, Bone Marrow Derived Mesenchymal Stem Cells, Adipose Tissue Derived Mesenchymal Stem Cells, Clinical Applications in Dentistry, Animal Studies. Stem cells offer a new era for craniofacial reconstruction. Both of adipose and bone marrow derived stem cells show effective results in the level of restoring function and esthetic. However, the AT-MSCs were easier to obtain without any harm to the patients.

This article examines the digital media revolution as a revolution reliant upon a sustained legacy of colonial violence in regions such as the Congo, the locale of this study. Contemporary production is foreshadowed by the industrial genocide of the late nineteenth and early twentieth centuries visited upon the Congo by Belgium. In an era defined by globally distributed trade networks, colonialism is equally distributed and mercurial -its complex supply chains obfuscating responsibility toward either the environment or its human inhabitants. The paper looks at the minerals required for latter day digital devices which have become the latest iteration of conflict in the region. Minerals are traced through a number of modern technologies including matches, atomic clocks and mobile devices, all of which evoke alchemical transformation and spectacle. We trace the legacy of colonial violence through smartphones, as the contemporary epitome of technical supremacy -highlighting their qualities of immediacy, mobility and making the remote proximate, especially by bringing remotely sourced geological elements into everyday use. Moving away from our own technoromantic affiliation with such commodities, the article highlights the fact that focus on effect often further obfuscates the causal factors and consequences of resource extraction in commodity production. Even as we summon stories of global trade with our fingertips on mobile, networked devices, we are implicated in these cycles of violence.

In this work, the zinc oxide (ZnO) and dioxide titanium (TiO₂) thin film were prepared by using the method of spry pyrolsis chemical with different thickness on glass substrate at temperature of 60º C. Thees different thickness of the deposited films were measured by using mass approximations weighting different method. The thickness for Tio₂ films
are (3.1, 0.24, 0.12)μm and for ZnO films (3.5, 4)μm. The samples coated have been irradiated by gamma ray to 21.5 kGy dose from Co-60 source. The optical properties such as the absorbance spectrum, transmittance, reflectance, and optical constant (absorption coefficient, extinction coefficient, refraction index and coefficient finesse with different thickness as function wave length of films but energy gap and urbach
energy as function photon energy) were studied before and after irradiation dose. From experimental work show that the color of these films were changed after irradiated, at the result all optical properties spectra thin films changed with different thicknesses. The absorption, reflectance absorption coefficient, extinction coefficient, refractive index,
coefficient finesse are increases after irradiation but the transmission, urbach energy and energy gap decreases after dose for all thicness of TiO2 films. Whereas absorption and absorption coefficient, extinction coefficient increases after irradiation for thiknsss of ZnO thin films but reflectance, transmission, refractive index, coefficient finesse urbach
energy and energy gap decreases after dose for Zno. These effect of optical properties may be due to change of structure properties for Tio2, Zno thin films after irradiated.

Lignocellulosic biomass has been acknowledged for potential use to produce chemicals and biomaterials. Lignin is the second most abundant natural polymer with cellulose being number one, making up to 10-25% of lignocellulosic biomass. Lignin is a three-dimensional, highly cross-linked macromolecule composed of three types of substituted phenols, which include: coniferyl, sinapyl, and p-coumaryl alcohols by enzymatic polymerization, yielding a vast number of functional groups and linkages. There is a wide range of lignin sources available, including: jute, hemp, cotton, and wood pulp. Hence, the lignin's physical and chemical behavior will be different with respect to the original source and extraction method used. The objective of this research is to extract lignin from nonwood cellulosic biomass (Wheat straw, Pine straw, Alfalfa, Kenaf, and Flax fiber) by formic acid treatment followed by peroxyformic acid treatment for the potential use as a partial replacement for the phenol precursor in resole phenolic systems. Isolated lignins were purified to remove impurities and characterized by Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC) analysis to compare thermal properties and chemical composition. It was found that lignin obtained from alfalfa provided the greatest yield of the various sources. Enthalpy measurements were higher for lignin from flax fiber and alfalfa at 190.57 and 160.90 J/g, respectively. The source of lignin samples was seen to affect the thermal properties. Overall, lignin extracted from wheat straw had the greatest thermal stability followed very closely by that obtained from flax fiber.

Les processus de détérioration des machines tournantes, qu'ils soient accidentels (rupture fragile d'un composant) ou résultant de l'usure normale des éléments mécaniques, sont en général très complexes. Toutefois, l'apparition d'une détérioration se traduit par une modification du comportement de la machine et en particulier une évolution des niveaux vibratoires. De ce fait, il existe plusieurs procédures de diagnostic de défauts. Le choix d'une approche est lié à la connaissance que l'on souhaite acquérir sur le système, mais aussi à la complexité de ce système. Les techniques de surveillance par reconnaissance de formes sont plus élaborées que les simples tests statistiques et sont capables de détecter et de diagnostiquer les défaillances d'une manière automatisée. Pour cela, il suffit d'extraire un vecteur de paramètres, appelé vecteur forme (VF), sur chacune des mesures effectuées sur la machine. La règle de décision utilisée permet de classer les observations décrites par le vecteur forme par rapport aux différents modes de fonctionnement connus avec ou sans défaut. Les travaux présentés dans cet article portent sur la sélection d'un nombre réduit de paramètres pertinents pour représenter les signatures vibratoires des défauts d'une boîte de vitesse CH-46 d'un hélicoptère de la marine américaine. Nous avons pu montrer que les performances des méthodes de reconnaissance de formes (RdF) sont étroitement liées à la pertinence des indicateurs de défauts.

The interactions of polymers (corn starch, dextrin from maize starch, humic acid sodium salt and sodium carboxymethyl cellulose) with iron oxides (hematite and magnetite) have been investigated by measuring adsorption isotherms and by electrophoresis. According to the electrophoresis measurements at pH 7 both iron oxides present negative surface charge and positive at pH 5. The equilibrium adsorption isotherms were then determined at pH 7 for all the adsorbates except for humic acid which was studied at pH 5, due to its anionic characteristics. The equilibrium data of both iron oxides were studied using Freundlich and Langmuir models and it was found to best fit to the Freundlich one. The values for Freundlich constants indicate that the mechanism that contributes most to the adsorption process in all experiments was the hydrogen bonding. However, the coexistence of more than one adsorption mechanism is what best explains the process itself, in addition to explaining the differences found amongst theories over the years.

espanolEn este estudio, se analiza la sinterabilidad de composites de matriz de aluminio reforzados con WC 1, 3, 5, 9 y 15% (en peso) y obtenidos por induccion rapida y metodos tradiconales. El procedimiento seguido fue, en primer lugar, presionar mediante un metodo de prensado en frio no axial con una presion de 200 MPa. Algunas de estas muestras patrones se sinterizaron mediante un metodo de sinterizacion por induccion rapida a ultra alta frecuencia, durante 300 s a temperatura de 600 °C. Otras muestras se sinterizaron a 600 °C durante 1800 s. Se midieron los valores de densidad y dureza de los composites sinterizados y se ensayaron las propiedades microestructurales, y el comportamiento de abrasion y de friccion. Se observo que si se aumentaba la relacion de refuerzo de WC la resistencia a la abrasion y el coeficiente de friccion tambien aumentaban. Finalmente, el estudio mostro que la sinterizacion a ultra alta frecuencia es una alternativa tan valida como el metodo tradicional ...

This work introduces an extremely easy method for preparing luminescent carbon dots (CDs) at ambient temperature using 1,2-naphthoquinone sulphonate and ethylenediamine as precursors via self-exothermic reaction without energy input. The as-obtained CDs have a high quantum yield (34.1 %), a production yield of 21.2 %, and a small size diameter (3.44 nm). Various techniques (NMR, TEM, EDX-mapping, XPS, XRD, FT-IR, fluorescence, and UV-visible spectroscopy) were used to characterize the prepared CDs. The CDs exhibited an excitation-independent emission with λ ex of 275 nm, demonstrating their homogeneity and high purity. The anticancer drug vincristine (VCR) quantitively quenched the fluorescent signal of the synthesized CDs, allowing their application as the first fluorescent nano-sensor to determine VCR. The quenching effect was linear within the range of 0.2-5.0 μg mL-1 , enabling the determination of VCR in vials, plasma, and for content uniformity testing with a detection limit of 0.06 μg mL-1. Moreover, the synthesized CDs were employed as a bio-sensing platform to detect VCR in cancer cells owing to their good selectivity, excellent biocompatibility, minimal cytotoxicity, and high stability. The fabrication of CDs with excellent properties at room temperature under mild conditions paves the way for new advancements in the room temperature synthesis of CDs and offers a highly efficient alternative to traditional synthesis approaches.

The paper describes structural changes in the welded joints, leading to the emergence of intergranular corrosion (IGC) during exploitation. The occurrence of intergranular corrosion in welded joints of austenitic, ferritic and duplex stainless steels and in welded joints of aluminium alloys and nickel alloys is analysed. Special attention was paid to austenitic stainless steels, due to their wide application in practice. In addition to sensitization in the weld heataffected zone (HAZ), which results in degradation of the welded joint (“weld decay”), also considered is the sensitization that occurs close to the weld metal in the stabilized steel, which leads to a “knife line attack”. Considerable attention is devoted to describing the various procedures in order to prevent the sensitization of the welded joints. Kljucne reci • metali i legure • zavareni spoj • interkristalna korozija • senzibilizacija Izvod

Present paper reports an overview on the processing, corrosion behavior and applications of various metal matrix composites with a special focus on iron based metal matrix nanocomposites. As iron has a much higher melting temperature compared to aluminum, copper and magnesium therefore it is synthesized using powder metallurgy technique. P/M technique is widely used because it provides microstructural control of the phases with or without less excessive interactions between matrix and the reinforcement. Gupta et al. have reported that Fe-Al2O3 metal matrix nanocomposites show improved properties which include density, hardness, wear, deformation and corrosion respectively. This research work shows that due to reactive sintering an iron aluminate (FeAl2O4) phase is formed and hence various properties have been found to improve. It is anticipated that the results of these investigations will be useful in developing better technology for producing higher grade metal matrix nanocomposites.

Additive Manufacturing (AM) transforms aerospace by enabling complex, resource-efficient designs. This paper explores how AM enhances durability and reduces failure modes like fatigue, stress corrosion cracking, and structural failure. Techniques such as Selective Laser Sintering (SLS), Electron Beam Melting (EBM), and Fused Deposition Modeling (FDM) are examined for their advantages over traditional methods. Challenges like material limitations and cost are discussed, highlighting AM's potential for sustainable aerospace innovation.

Cement is among the important contributors to carbon dioxide emissions in modern society. Researchers are studying solutions to reduce the cement content in concrete to minimize the negative impact on the environment. Among these solutions is replacing cement with other materials, such as waste, which also poses environmental damage and requires landfill areas for disposal. Among these wastes are eggshell powder ash (ESPA) and wheat straw ash (WSA), which were utilized as cement substitutes in green mortar production. Thirteen mixtures were cast, one as a reference without replacement and twelve others that included replacing ESPA and WSA (single and combined) with cement in 2%, 4%, 6%, and 8% proportions of cement's weight. The mechanical (compressive and flexural strength), microstructural (SEM), and thermogravimetric analysis (TG/DTA) properties of all mixtures were examined. The results showed a remarkable improvement in mechanical properties, and the best improvement was recorded for the (4%ESPA+4%WSA) mixture, which reached 73.3% in compressive strength and 56% in flexural strength, superior to the reference mixture. Furthermore, SEM analyses showed a dense and compact microstructure for the ESPA and WSA-based mortars. Therefore, the WSA and ESPA wastes can be recycled and utilized as a substitute for cement to produce an eco-friendly binder that significantly improves the microstructural and mechanical characteristics of mortar. In addition, combining the two materials also presents a viable option for creating a sustainable ternary blended binder (with cement) that boasts superior properties compared to using the WSA or ESPA individually.

Higher performance is steadily required in the field of material surface engineering, especially in terms of surface degradation of mechanical parts and repair and renewal of surfaces. By preparing a more reasonable surface design and improving the surface composition and structure of the material, the surface modification layer can provide an important potential solution to the surface degradation problem. The coatings obtained by double glow plasma surface alloying (DGPSA) technology are a compelling method in current and future applications because of a unique combination of characteristics including pollution-free, the gradient distribution of the alloying elements and the strong metallurgical bonding between the alloying layer and the matrix. In recent years, with the increasing requirements for the surface properties of materials in various environments, the layer prepared by DGPSA technology is developing toward alloying, functionalization and nanometer. This review begins with a brief introduction of double glow plasma surface alloying. The recent developments of the double glow plasma surface alloying technology for improving various surface performance are systematically reviewed in the sight of applied material, background, duplex treatment and duplex coating preparation.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Ferritic stainless steels (FSSs) are viable alternatives to nickel containing austenitic stainless steels. The AISI 436 FSS grade is fully ferritic at all temperature ranges, and therefore, grain refinement can only be achieved through controlling inclusions during solidification and/or recrystallization. In this work, the effects of strain and inter-pass time on the restoration behavior of 436 were systematically investigated using the Gleeble 1500 thermomechanical processing simulator. The aim of the study was to promote the accumulation of strain by delaying recrystallization during roughing rolling simulation to improve the driving force for recrystallization during finishing rolling simulation at lower temperature. Three roughing rolling schedules were designed, i.e., the first simulated the existing industry practice (Control), the second with increased inter-pass time (INT) and the last with both increased inter-pass time and strain per pass (INT + S). Roughing and finishing were each simulated in three-passes, amounting to a total of six-passes. The SEM-EBSD results revealed that the Control and INT schedules resulted in higher strain localization, particularly around particles. On the contrary, the increased inter-pass times and strains (INT + S) led to less strain accumulation. Annealing after roughing rolling simulation led to the nucleation of fine grains in the Control, which suggests that delaying finishing rolling would promote recrystallization and the breakdown of the cast structure.

Artificial Neural Networks (ANNs) are excellent tools for prediction of complex processes that have many variables and complex interactions. In the present study, the properties of copper based composite prepared from sintering of mechanically alloyed powders, were predicted using Artificial Neural Network (ANN) approach. In order to prepare copper based composites, copper powder with four different amounts of Al 2 O 3 reinforcement (1, 1.5, 2, 2.5 wt%) were mechanically alloyed and the consolidated compacts of prepared powders were sintered in five different temperatures of 725-925 • C at seven several sintering times of 15-180 min. Hardness and electrical conductivity measurements were performed to evaluate the properties of these composites. Then, for modeling and prediction of hardness and electrical conductivity, a multi layer perceptron back propagation feed forward neural network was constructed to evaluate and compare the experimental calculated data to predicted values. It was found that, in a given sintering temperature of 875 • C, the electrical conductivity increases as the sintering time increases and the amount of Al 2 O 3 reinforcement decreases. Also, increasing of reinforcement amount and sintering time in a given sintering temperature of 875 • C leads to a decrease in hardness. Furthermore, electrical conductivity and hardness of specimens have shown a consistency with predicted results of ANN. These trained values had an average error of 3% and 5% for electrical conductivity and hardness values, respectively.

Premium and super premium Rails Microstructure Mechanical properties a b s t r a c t Heavy haul railways are increasingly being subjected to operating conditions that demand better performance of the materials, with speeds of operation and loads increasing to comply with the large demand for transportation. For joining of rails, the Flash Butt Welding (FBW) process stands out due to the higher quality of the joint with respect to thermite welding. However, the properties of the rails may be compromised because of improper parameterization of the welding process and the appearance of defects in the welded joint, as well as heterogeneities in the Heat Affected Zone (HAZ). In this work, a statistically planned experimental array was used to study four parameters of the FBW process (pulse current, number of pulses, upsetting force, and equivalent carbon) on Premium and Super Premium rail steels. The array generated eight different welding conditions. The results made it possible to understand the relationship between the microstructure and the microhardness maps on the longitudinal section of the welded joint. Fracture analysis showed the fracture mechanisms for each welding condition. The Premium rails showed double-necking in the partial austenitization region while Super Premium rails showed brittle fracture, except for the more extreme welding condition. Additionally, two welding conditions showed doublenecking in the partial austenitization region, but with brittle fracture outside the necking region. Tensile tests showed that the welding condition that corresponds the highest heat input presented the worst mechanical behavior for applications on railroads and the welding conditions with lowest heat input presented the best behavior.

This study investigated the impact of absorption layer thickness and back reflection layer incorporation on (CIGS/TiO2/ZTO/ZnO:Al) solar cell efficiency. Results demonstrated that cell efficiency increases with absorption layer thickness until stabilizing at an optimal balance with other layers. The addition of a back reflection layer enhanced the efficiency while allowing for reduced absorption layer thickness, potentially lowering production costs. MoSe 2 was identified as the optimal back reflection layer material, enabling a reduction in absorption layer thickness to 0.5 µm. Initial results yielded Voc = 0.6865 V, Jsc=40.32 mA/cm 2 , FF = 83.30 %, and η = 23.06 %. Further investigation revealed that back reflection layer thickness also influences cell performance, with efficiency increasing until stabilization. Optimizing this parameter resulted in improved final outcomes: Voc=0.6955 V, Jsc=42.98 mA/cm 2 , FF = 83.10 % and η = 24.84 %. These findings contribute to the ongoing efforts to enhance solar cell efficiency and reduce manufacturing costs. ☆ This article is part of a special issue entitled: 'Graphene Photonics' published in Results in Optics.

This study investigated the impact of absorption layer thickness and back reflection layer incorporation on (CIGS/TiO2/ZTO/ZnO:Al) solar cell efficiency. Results demonstrated that cell efficiency increases with absorption layer thickness until stabilizing at an optimal balance with other layers. The addition of a back reflection layer enhanced the efficiency while allowing for reduced absorption layer thickness, potentially lowering production costs. MoSe 2 was identified as the optimal back reflection layer material, enabling a reduction in absorption layer thickness to 0.5 µm. Initial results yielded Voc = 0.6865 V, Jsc=40.32 mA/cm 2 , FF = 83.30 %, and η = 23.06 %. Further investigation revealed that back reflection layer thickness also influences cell performance, with efficiency increasing until stabilization. Optimizing this parameter resulted in improved final outcomes: Voc=0.6955 V, Jsc=42.98 mA/cm 2 , FF = 83.10 % and η = 24.84 %. These findings contribute to the ongoing efforts to enhance solar cell efficiency and reduce manufacturing costs. ☆ This article is part of a special issue entitled: 'Graphene Photonics' published in Results in Optics.

In this paper, laboratory and semi-industrial processes for the preparation of aluminium foam samples and core-foamed panels with closed porosity were investigated. The samples were prepared starting from the accumulative hot-roll bonded precursors, with titanium hydride (TiH 2 ) or dolomite (Ca 0.5 Mg 0.5 CO 3 ) powder added as the foaming agent. The formation of the precursors was performed in three steps. In the initial stage, titanium dihydride or dolomite particles were deposited on a single side of a selected number of aluminium strip samples made from the alloy AA 1050. In the second step, by putting together in pairs, single-sided coated strips, precursors with a two-layered structure were prepared. The samples were hot-rolled to a final thickness of 1.9-3.8 mm, introducing a total deformation of about 45-49% by a process well-known as accumulative hot-roll bonding. In the third stage of the precursor's formation, the desired multilayered precursor's structure was achieved by hot-roll multi-passing, i.e., by repeating (with 2-16 passes) the accumulative hot-roll bonding procedure. The obtained precursors were foamed in an electrical furnace, under different foaming conditions, based on the initial temperature of the thermal decomposition of the foaming agent. The microstructure of the obtained foam samples was investigated with optical and scanning electron microscopy. According to the accumulated experimental results, one can conclude that the usage of dolomite powder as a foaming agent with a higher temperature of thermal decomposition (>750 °C) compared to TiH 2 , which thermally decomposed even at the temperature of hot-rolling (>350 °C), enabling the formation of multilayered precursors at higher temperatures of hot-rolling without any intermediate annealing. This consequently increases the productivity of the foamed core panel production without influencing their final quality.

Natural fiber-reinforced composites have great potential as they have good mechanical properties and are environmentally friendly and sustainable. This study improves the adhesivity properties of Sansevieria natural fiber composite reinforcement through alkali treatment. Alkaline soaking of sansevieria fibers for 2 hours using a 5% NaOH solution. Furthermore, the fiber is used as a composite reinforcement with a polyester resin matrix. Characterization of the chemical properties of the composite was carried out by TGA and XRD tests, mechanical properties tests by tensile tests, morphological observation using SEM, and pull-out tests. The results showed that alkali treatment of the fibers could increase the tensile strength of the composite by 142.7 MPa, up 70% from the fiber-reinforced composite without alkali. XRD and EDX analysis indicated changes in the crystal structure and surface composition of the fibers after alkali treatment. This fact indicates the contribution of alkali to the increase in adhesivity. This improvement is also supported by the higher pull-out test results in the composites with alkali-treated fibers. The results show that alkali treatment is an effective method to improve the adhesivity properties of sansevieria fibers in composites, thus potentially improving the overall mechanical performance of the composites.

Among the natural fibers, the hemp fiber extracted from the stem of Cannabis sativa is, after sisal, the second most applied as reinforcement of polymer composites and increasingly used from automotive to civil construction industries. Polypropylene (PP) is the most common hemp fiber-reinforced matrix. Despite numerous papers on the application of natural fibers reinforcing polymer composites for ballistic protection, only one was so far dedicated to hemp fibers/PP with this purpose. In the present work, the main objective is for the first time to investigate the ballistic performance of the epoxy matrix reinforced with up to 30 vol% of hemp fabric. Epoxy is recently emerging as another strong alternative for the hemp fiber/fabric matrix. Due to the great variability in properties, a preliminary investigation was conducted on the basic mechanical and thermal behavior of the composites. The 30 vol% reinforcement with hemp fabric increased by 7.5 times the Izod impact energy as well as by more than 60% the tensile strength and 80% of the elastic modulus as compared to the neat epoxy. For all composites, a decrease of 20% in thermal temperatures (T onset and T max ) occurred in comparison to neat epoxy. The absorbed ballistic energy from the impact of 0.22 ammunition was significantly higher (95e108.5 J) than that previously reported of 36 J for hemp fabric/PP composite and others natural fiber/ epoxy composites.

A morfologia, dimensões e composição química de tribocamadas são fortemente dependentes das pressões e temperaturas existentes no contato e oriundas das reações das superfícies entre si, com a atmosfera, com os lubrificantes e contaminantes presentes no contato. No presente artigo foi analisada a formação de tribocamadas em pares DLCaço inoxidável testados por 180, 500, 1000 e 2500 horas em atmosfera de gás refrigerante R134a sem a presença de óleo lubrificante. A caracterização foi realizada por microscopia eletrônica de varredura espectroscopia de energia dispersiva (MEV-EDS) (morfologia e composição química) e interferometria ótica de luz branca (dimensões). Nas análises por MEV-EDS foram identificadas tribocamadas que se apresentaram mais pronunciadas nas superfícies do aço inoxidável sendo as mesmas oriundas de transferências mútuas entre os pares tribológicos bem como oxidação. A espessura das tribocamadas, por sua vez variou de 100 a 500 nm. Os resultados revelam que as tribocamadas são quimicamente estáveis e que suas espessuras não variam significativamente após mil horas de ensaio. Palavras-chave: Tribologia, tribocamada, Carbono tipo-diamante (DLC).

Purpose-The purpose of this paper is to study the thermal behavior of radial porous fin surrounded by water-base copper nanoparticles under the influence of radiation. Design/methodology/approach-In order to optimize the response variable, the authors perform sensitivity analysis with the aid of response surface methodology (RSM). Moreover, this study enlightens the applications of artificial neural networks (ANN) for predicting the temperature gradient. The governing modeled equations are firstly non-dimensionalized and then solved with the aid of Runge-Kutta fourth order together with the shooting method in order to guess the initial conditions. Findings-Numerical results are analyzed and presented in the form of tables and graphs. This study reveals that the temperature of the fin is decreasing as the wet porous parameter increases (m 2) and the temperature for 10% concentration of nanoparticles are higher than 5 and 1%. Physical parameters involved in the study are analyzed and processed through RSM. It is come to know that sensitivity of temperature gradient to radiative parameter (Nr) and convective parameter (Nc) is positive and negative to dimensionless ambient temperature (θ a). Furthermore, after ANN training it can be argued that the established model can efficiently be used to predict the temperature gradient over a radial porous fin for the copper-water nanofluid flow. Originality/value-To the best of our knowledge, only a few attempts have been made to analyze the thermal behavior of radial porous fin surrounded by copper-based nanofluid under the influence of radiation and convection.

Friction surfacing (FS) is a coating technique applied mainly in corrosion protection and repair of components. The study addresses the effects of deposition and rotational speeds on the rods characteristics and process efficiency for the deposition of Ti-6Al-4V on self-mating substrates by FS. The consumption rate was 1.8 mm/s, deposition speeds of 8, 16 and 24 mm/s and rotational speeds of 2000, 3000 and 4000 rpm. It was shown that the flash forms primarily at the rod, ascending around the tip and leaving the coating without flash. The higher deposition speeds led to a decrease in rod thickness and diameter. For higher rotational speeds, an increase in diameter and decrease in thickness is observed for the flash on the rod. Experiments have shown that the rotational and deposition speeds have a decisive influence on the flash formation. Its microstructure changes due to the welding process and a change in hardness can be observed.

Titanium Grade 1 was deposited on Ti-6Al-4V, 2 mm thickness, by Friction Surfacing. The process parameters were rotational speed, deposition speed and consumption rate. Only the rotational speed was varied in order to evaluate the influence of this parameter on the coatings generated. The applicability of the process has been described for a large number of materials, although the depositions of titanium alloys are still not widely studied. The objective is to investigate the effects of the rotational speed on the coatings' geometry and microstructural evolution. This investigation has shown that Titanium Grade 1 coatings can be deposited onto a Ti-6Al-4V by Friction Surfacing depending on the rotational speed. The coatings' surface homogeneity was influenced by the rotational speed, being inhomogeneous for the lowest speed. The coatings' thickness and width increased with enhancing this speed. The heat affected zone in the substrate corresponded to the complete thickness under the depositions.

Introduction There is increasing interest in the lost foam casting technique because of its ability to produce near-net-shaped components of high complexity. The idea is to first make a prototype of the part to be cast in foam. This is then used as a pattern that can be placed in a box and surrounded by sand. Finally, metal is poured such that it smoothly replaces the foam by melting and/or evaporating it.

Stay-in-place (SIP) formwork is a more-practical alternative to traditional steel or wood formworks due to its improved constructability and durability. The aim of this paper was to study the fire resistance performances of structural and non-structural concrete panels with polyvinyl chloride (PVC) SIP formwork. Three 124.01 in × 110.24 in × 3.15 in panels of PVC SIP formwork were tested and compared to one another. All panels were aged for 28 days, then exposed to the standard fire curve based on the ISO 834:2014 standard, and the temperatures in each panel surface recorded. The results indicate that concrete strength significantly influenced the structural stability and the fire resistance time of the panels (under load), even in this type of panels when exposed to high temperatures. It was found that the PVC encasement enhanced the thermal insulation property, one of the fire resistance performance criteria. Overall, the importance of this alternative formwork is the reduction in the use of forest resources, the raise of awareness of their conservation, and the promotion of their rational use as this a material is friendly to the environment.

High Calcium Fly Ashes are reactive materials that often do not meet the limits of the standards. Therefore, most of the quantity produced annually in the world, due to lignite burning, remains unexploited and charges the environment. Efforts of standardizing these materials as supplementary cementitious materials in Europe failed because there are some bad experiences with the material in the past and many doubts about the performance in concrete mixtures. The only way of utilization of these fly ashes is to be used in the blended cement industry. Actually, a low percentage of the materials is absorbed at a permanent basis from the cement industry and huge amounts are rejected or used for reclamation of mining areas. However, investigation on these materials has shown which are the weak points and how they could be overcome by using advances in materials technology. Moreover, they could be classified in categories relative to application fields where the addition in concrete mixtures is advantageous. Following this concept, National Specifications for the use of calcareous fly ash in concrete were established and are in force in Greece, where only such fly ashes are produced at the power stations of the Public Power Corporation. Therefore, categorization of calcareous fly ashes was made according to their free lime content, sulphate content and fineness, which are considered the most influential characteristics on the performance of fly ashes. Then, criteria for their pozzolanicity and volume stability were suggested, following the pattern of the EN 450 Standard for low-calcium fly ashes, but modified in order to be more realistic for calcareous fly ashes. A complete methodology of testing these fly ashes is accompanying the National Specification document, since it was found that some modifications on the relevant methodologies were necessary. The authors, who played a leading role in the more than five year old national effort, believe that this regulative frame provides flexibility in the utilization of calcareous fly ashes and promotes their marketing.

Nowadays, the extrusion process has an important role in the production of parts with high mechanical properties and quality in high-tech industries. In this study, the deformation behavior of aluminum alloy 7075, which is a very applicable alloy in the aerospace industry, has been studied under the backward extrusion process to produce conical parts. In this regard, the finite element simulation was performed by ABAQUS software. In this research, the variations of imposed plastic strain along the part's thickness have been investigated under different frictional conditions. The mesh sensitivity test also was performed to obtain more accurate results. The error of simulation results was about 10%, which indicates the high accuracy of the simulation. The maximum amount of deformation load was about 73 KN at the friction coefficient of 0.15, which was observed after 80% of the punch displacement. Eventually, this is concluded that by increasing the friction coefficient, the amount of imposed plastic strain has been increased. The average plastic strain in this process was about 1 which will result in better mechanical properties of the product. The results showed that by using backward extrusion in producing conical parts in the aircraft industry, this is possible to use more lightweight products with better mechanical properties.

Implants are usually manufactured in titanium alloys due to their biocompatibility and high corrosion resistance. The additional elements present in titanium alloys increase the mechanical properties but also increase the possibility of infectious-inflammatory processes in the implanted region. Commercially pure titanium (CP Ti) has lower mechanical properties, but it can be processed by severe plastic deformation for grain refining and enhancement of mechanical behavior. This paper compares the machinability of di erent workpieces, manufactured in CP-Ti and CP-Ti powder processed by Equal Channel Angular Pressing (ECAP), using cutting forces as the reference parameter. Although mechanical properties are improved, cutting force experiments show that extruded specimens presented same level of machinability of CP-Ti bar.

The study is fundamentally geared toward the investigation of the influence of Manual Metal Arc (MMA) welding on the mechanical and microstructural properties of low carbon steel immersed in a 0.5 M nitric acid environment having a pH of 0.3. The corrosion and mechanical behavior of the substrates are investigated prior to and after 336 h of immersion in the test environment. The outcome of the experiment shows that the structural integrity of the immersed substrates is affected due to corrosion in the test environment. Prior to immersion, the bending resistance is seen to decrease at the welded joints relative to the blank sample and then decrease further after immersion in the test solution respectively as 3.95, 3.53, and 4.21KN. Similarly, the tensile strength of the immersed substrate decreases as compared to the unexposed and blank samples; exposed to test environment (30.60%), welded unexposed to test environment (33.25%) and for the control sample (36.33%). Furthermore, the hardness value is observed to be higher at the heat-affected zone (HAZ) of the test substrate than at the weldment and parent metal, respectively, as 11.3, 17.7, and 15.7HV. Optical micrographs prior to and after immersion have evidently revealed that heat input during welding has caused recrystallization leading to coarser grains at the HAZ.

This book presents the basic provisions and principles of production of iron ore pel-lets from magnetite concentrates. The main stages of the technological process are con-sidered, starting from the preparation of raw materials and ending with the production of commercial pellets. The basics of rating raw materials are reflected. The factors of pelletizing processing that affect the production of high-quality pellets are analyzed, in-cluding the requirements for the mineralogy of the ore component, physical, chemical and metallurgical properties and methods for their determination. The features of the operation of the roasting machine and the use of alternative types of biofuel are de-scribed. The tools for managing the technological process are given. Modern aspects of building a quality management system for the produced pellets are shown with the in-troduction of the concepts of a quality guide and a knowledge base.
Designed for employees of mining and processing and metallurgical enterprises that have divisions for the production of iron ore pellets.

The use of plant fibres in industrial applications has traditionally been dominated by fibres from staple crops such as cotton, hemp, and jute. However, the potential of ornamental crops as sources of fibrous materials has garnered increasing interest due to their unique structural properties,
sustainability, and ecological benefits. This review comprehensively explores the fibres derived from various ornamental species, including orchids, palms, grasses and woody shrubs, and evaluates their extraction methods, physical and chemical properties, and potential applications. Ornamental plants, often cultivated for their aesthetic appeal, possess fibres that can be utilized in a range of industries, from textiles and handcrafts to eco-friendly packaging and bio-composites. The fibres
extracted from these crops are often strong, elastic and biodegradable, offering an alternative to synthetic fibres and conventional natural fibres. Despite the promising characteristics of ornamental fibres, challenges related to large-scale cultivation, fibre extraction, and processing remain a barrier to their widespread use. This review highlights the growing body of research on ornamental crop fibres, discussing key species, such as orchids and palms, and providing insight into their sustainability, commercial potential, and contribution to a circular economy. The review also examines the environmental and economic benefits of utilizing ornamental plants for fibre production, proposing strategies to overcome existing limitations and encouraging further exploration of these underutilized resources. By emphasizing the potential of ornamental crops as viable fibre sources, this paper aims to contribute to the development of sustainable materials and to inspire future research in the field of natural fibres.

An aqueous hybrid inorganic/organic sol-gel solution composed of tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS) was applied on ZnFe (14 wt.% Fe) electrodeposited on steel as a sacrificial layer. Two precursor contents were studied: 10 (SG10) and 30 % (SG30). First, the morphology and thickness of the films were assessed by Scanning Electron Microscopy (SEM) observations. They revealed the presence of micro-cracks in the films without alkaline surface preparation due to the pyramidal shape of the ZnFe deposit. Then, the corrosion resistance of the systems was determined by Electrochemical Impedance Spectroscopy (EIS) and Neutral Salt Spray (NSS) test. All results indicated an improvement in the corrosion resistance thanks to the presence of the SG films. However, the protection provided by the SG10 film did not permit to durably protect the ZnFe deposit. The combination of surface preparation and a SG30 film provided promising protection to the ZnFe deposit with an increase of the low-frequency modulus and a delay in corrosion product appearance during the NSS test.

Pristine samples of a polymer blend of polyvinylpyrrolidone (PVP)/ polyvinyl alcohol (PVA)/ chitosan filled with different concentrations of silver nanoparticles (AgNPs) were prepared using the casting method. The samples were then examined using various physical and antibacterial characterization techniques. Characterization studies showed that the blend provides a uniform and controlled distribution of AgNPs inside the polymeric matrix without the addition of any more stabilizers. The mean particle size for green and laser-ablated AgNPs was found to be 50 nm according to transmission electron microscopy (TEM) studies. Fourier transforms infrared (FTIR) studies showed the presence of characteristic main peaks corresponding to the vibrational groups which characterize the prepared samples. The interactions between the AgNPs and the blend were marked by changes in the intensity of vibrational peaks and spectral positions. X-ray diffraction (XRD) confirmed the structural modification ...