MULTI-PHASE FENICOCUMO AND FENICOCUNB HIGH-ENTROPY ALLOYS WERE SUCCESSFULLY SYNTHESIZED VIA MECHANICAL ALLOYING AND HOT PRESSING. FENICOCUNB AND FENICOCUMO FORMED A FACE-CENTERED CUBIC SOLID SOLUTION FOR 15 AND 30 HOURS OF MILLING, RESPECTIVELY. AT LONGER MILLING TIMES, BOTH ALLOYS WERE CONSTITUTED BY AMORPHOUS PHASES. THE SAMPLES HOT-PRESSED AT 1000 °C EXHIBITED A MAJOR FACE-CENTERED CUBIC PHASE AND INTERMETALLIC PHASES: C14 LAVES PHASE IN FENICOCUNB ALLOY, AND ? AND ? PHASES IN FENICOCUMO ALLOY. SEMI-HARD MAGNETISM WAS FOUND IN SINTERED FENICOCUMO AND FENICOCUNB ALLOYS, ASSOCIATED WITH AN EXTENSIVE AMOUNT OF PHASE BOUNDARIES. THE FENICOCUMO ALLOY PRESENTED A SATURATION MAGNETIZATION (MS) OF 62.63 EMU G?1 AND COERCIVITY (HC) OF 40.69 OE. BY SUBSTITUTING MO FOR NB, THE MS VALUE WAS REDUCED TO 53.27 EMU G?1, WHILE THE COERCIVITY WAS INCREASED UP TO 53.49 OE. THE PRESENCE OF HARD INTERMETALLIC PHASES AND SOLID-SOLUTION STRENGTHENING LED TO HIGH-HARDNESS FENICOCU-BASED HIGH-ENTROPY ALLOYS. ALTHOUGH NB INCREASED THE MICROHARDNESS AND ELECTRICAL RESISTIVITY OF THE ALLOY, IT ALSO REDUCED THE SOFT MAGNETIC PROPERTIES OF THE ALLOYS. BETTER MAGNETIC PROPERTIES WERE FOUND BY THE ADDITION OF MO, SUGGESTING THAT TAILORING ITS CONTENT COULD CONDUCT TO OBTAIN AN EXCELLENT BALANCE BETWEEN MECHANICAL AND SOFT MAGNETIC PROPERTIES IN THE FENICO-BASED HIGH-ENTROPY ALLOYS.

THIS WORK AIMS TO DO A COMPUTATIONAL ANALYSIS OF THE INFLUENCE THAT GRADED POROSITY HAS ON THE ELASTIC MODULUS OF COMMERCIALLY PURE TI FOAMS. THIS ANALYSIS IS FOCUSED ON TI FOAMS FOR BIOMEDICAL USES. TWO KINDS OF GRADED POROSITY WERE CONSIDERED, LONGITUDINAL GRADED AND LATITUDINAL GRADED POROSITIES. EACH MODEL WAS MADE CONSIDERING THREE ZONES WITH DIFFERENT POROSITY LEVELS. THE ELASTIC MODULUS SIMULATIONS WERE MADE BY THE FINITE ELEMENT ANALYSIS (FEA) USING ANSYS SOFTWARE V19.3. THE RESULTS WERE COMPARED WITH EXPERIMENTAL DATA REPORTED IN THE LITERATURE. THE LONGITUDINAL AND LATITUDINAL GRADED POROSITY DISTRIBUTION MODELS WERE ANALYZED WITH EQUIVALENT POROSITY BETWEEN 30% AND 40% AND 20?50%, RESPECTIVELY. THE ELASTIC MODULUS VALUES DECREASED FROM 110 TO 38 GPA FOR THE LONGITUDINAL GRADED POROSITY, AND FROM 110 TO 36 GPA FOR THE LATITUDINAL GRADED POROSITY (0% AND 40% POROSITY, RESPECTIVELY). THOSE RESULTS SHOWED THAT LONGITUDINAL GRADED POROSITY WAS STIFFER THAN LATITUDINAL GRADED POROSITY MODELS FOR ALL POROSITY LEVELS.

THIS WORK AIMS TO PERFORM A COMPUTATIONAL ANALYSIS ON THE INFLUENCE THAT MICROSTRUCTURE AND POROSITY HAVE ON THE ELASTIC MODULUS OF TI-6AL-4V FOAMS USED IN BIOMEDICAL APPLICATIONS WITH DIFFERENT ?/?-PHASE RATIOS. THE WORK IS DIVIDED INTO TWO ANALYSES, FIRST THE INFLUENCE THAT THE ?/?-PHASE RATIO HAS AND SECOND THE EFFECTS THAT POROSITY AND ?/?-PHASE RATIO HAVE ON THE ELASTIC MODULUS. TWO MICROSTRUCTURES WERE ANALYZED: EQUIAXIAL ?-PHASE GRAINS + INTERGRANULAR ?-PHASE (MICROSTRUCTURE A) AND EQUIAXIAL ?-PHASE GRAINS + INTERGRANULAR ?-PHASE (MICROSTRUCTURE B). THE ?/?-PHASE RATIO WAS VARIATED FROM 10 TO 90% AND THE POROSITY FROM 29 TO 56%. THE SIMULATIONS OF THE ELASTIC MODULUS WERE CARRIED OUT USING FINITE ELEMENT ANALYSIS (FEA) USING ANSYS SOFTWARE V19.3. THE RESULTS WERE COMPARED WITH EXPERIMENTAL DATA REPORTED BY OUR GROUP AND THOSE FOUND IN THE LITERATURE. THE ?-PHASE AMOUNT AND POROSITY HAVE A SYNERGIC EFFECT ON THE ELASTIC MODULUS, FOR EXAMPLE, WHEN THE FOAM HAS A POROSITY OF 29 WITH 0% ?-PHASE, AND IT HAS AN ELASTIC MODULUS OF ?55 GPA, BUT WHEN THE ?-PHASE AMOUNT INCREASES TO 91%, THE ELASTIC MODULUS DECREASES AS LOW AS 38 GPA. THE FOAMS WITH 54% POROSITY HAVE VALUES SMALLER THAN 30 GPA FOR ALL THE ?-PHASE AMOUNTS.

EN ESTE TRABAJO, SE X0.85?XPREPARARON COMO ELECTROLITOS PARA APLICACIONES DE PILAS DE COMBUSTIBLE DE ÓXIDO SÓLIDO, LA 0,85 X 1,85 MG 0,15 MG 0,15 O 3O (LSBGM), CON 0 X X . . . . . . . . . . . . . . . . . . . . . . SE ESTUDIÓ EL EFECTO DE LA TEMPERATURA DE BARIO Y SINTERIZACIÓN EN LA ESTRUCTURA Y LAS PROPIEDADES ELÉCTRICAS. SE UTILIZÓ UN MÉTODO DE COMBUSTIÓN RÁPIDA, COMENZANDO CON SALES DE NITRATO Y ÁCIDO CÍTRICO COMO COMBUSTIBLE. LOS ESPECTROS XRD MOSTRARON DOS FASES PRINCIPALES CORRESPONDIENTES A LSGM ORTOHOMBIC (GRUPO ESPACIAL IMMA) Y LSGM-CUBIC (GRUPO ESPACIAL PM-3 M). A PARTIR DE LA LITERATURA, AMBAS ESTRUCTURAS SE REPORTAN COMO ESPECIES CONDUCTORAS DE ION DE ALTO OXÍGENO, PERO NORMALMENTE, NO SE INFORMA DE QUE APAREZCAN JUNTAS. LAS PRINCIPALES FASES SECUNDARIAS FUERON LASRGAO 44, BALAGAO 44, Y BALAGAO 77. SEM REVELÓ UN MATERIAL CON BAJA POROSIDAD, LO QUE INDICA UNA DENSIFICACIÓN INCOMPLETA. LA MUESTRA LA 0.85 SR 0.075 BA 0.075 GA 0.85 MG 0.15 O 3O OO. . MOSTRÓ UNA CONDUCTIVIDAD DE 0.016 Y 0.058 S CM 1 A 600 OC Y 800 OC, RESPECTIVAMENTE. ESTO SIGNIFICA UNA MEJORA DEL 34% EN COMPARACIÓN CON LA MUESTRA NO DE BARIO LA SR GA MG O A 600 OC. ASÍ, ESTA COMPOSICIÓN PODRÍA SER UTILIZADA EN SOFC. RESUMEN GRÁFICO

THIS WORK INVESTIGATES THE EFFECT OF MG AND CA PRECIPITATES ON THE ELECTROCHEMICAL PERFORMANCE OF FE-MN-NI-BASED ANODES PRODUCED THROUGH POWDER METALLURGY IN SIMULATED AND REAL ALKALINE SEAWATER. THE ELECTRODES THAT EXHIBITED THE BEST PERFORMANCE IN SIMULATED SEAWATER WERE THOSE CONTAINING 60 %FE-40 %NI AND 15 %FE-15 %MN-70 %FE, BOTH WITH AN OVERPOTENTIAL FOR THE OXYGEN EVOLUTION REACTION OF 370 MV AT 10 MA/CM2 AND TAFEL SLOPES OF 45 AND 53 MV/DEC, RESPECTIVELY. HOWEVER, WHEN REAL ALKALINE SEAWATER WAS USED AS ELECTROLYTE, THE ELECTROCATALYTIC ABILITY OF THESE ELECTRODES DECREASED; THE PRESENCE OF CA2+ WAS IDENTIFIED AS A SIGNIFICANT FACTOR PROMOTING PITTING CORROSION. THE STUDY CONCLUDES THAT A COMPREHENSIVE INVESTIGATION INTO THE INDIVIDUAL EFFECT OF SEAWATER IONS ON ELECTRODE PERFORMANCE IS NECESSARY.

IN THIS WORK, A BLEND OF TI, NB, AND MN POWDERS, WITH A NOMINAL COMPOSITION OF 15 WT.% OF MN, AND BALANCED TI AND NB WT.%, WAS SELECTED TO BE MECHANICALLY ALLOYED BY THE FOLLOWING TWO ALTERNATIVE HIGH-ENERGY MILLING DEVICES: A VIBRATORY 8000D MIXER/MILL® AND A PM400 RETSCH® PLANETARY BALL MILL. TWO BALL-TO-POWDER RATIO (BPR) CONDITIONS (10:1 AND 20:1) WERE APPLIED, TO STUDY THE EVOLUTION OF THE SYNTHESIZED PHASES UNDER EACH OF THE TWO MECHANICAL ALLOYING CONDITIONS. THE MAIN FINDINGS OBSERVED INCLUDE THE FOLLOWING: (1) THE SEQUENCE CONVERSION EVOLVED FROM RAW ELEMENTS TO A TRANSITORY BCC-TINBMN ALLOY, AND SUBSEQUENTLY TO AN FCC-TINB15MN ALLOY, INDEPENDENT OF THE MILLING CONDITIONS; (2) THE TOTAL FULL CONVERSION TO THE FCC-TINB15MN ALLOY WAS ONLY REACHED BY THE PLANETARY MILL AT A MINIMUM OF 12 H OF MILLING TIME, FOR EITHER OF THE BPR EMPLOYED; (3) THE PLANETARY MILL PRODUCED A NON-NEGLIGIBLE FE CONTAMINATION FROM THE MILLING MEDIA, WHEN THE HIGHEST BPR AND MILLING TIME WERE APPLIED; AND (4) THE FINAL FCC-TINB15MN ALLOY SYNTHESIZED PRESENTS A NANOCRYSTALLINE NATURE AND A PARTIAL DEGREE OF AMORPHIZATION.

COMMERCIALLY PURE (C.P.) TITANIUM GRADE IV WITH A BIMODAL MICROSTRUCTURE IS A PROMISING MATERIAL FOR BIOMEDICAL IMPLANTS. THE INFLUENCE OF THE PROCESSING PARAMETERS ON THE PHYSICAL, MICROSTRUCTURAL, AND MECHANICAL PROPERTIES WAS INVESTIGATED. THE BIMODAL MICROSTRUCTURE WAS ACHIEVED FROM THE BLENDS OF POWDER PARTICLES WITH DIFFERENT SIZES, WHILE THE POROUS STRUCTURE WAS OBTAINED USING THE SPACE-HOLDER TECHNIQUE (50 VOL.% OF AMMONIUM BICARBONATE). MECHANICALLY MILLED POWDERS (10 AND 20 H) WERE MIXED IN 50 WT.% OR 75 WT.% WITH C.P. TITANIUM. FOUR DIFFERENT MIXTURES OF POWDERS WERE PRECOMPACTED VIA UNIAXIAL COLD PRESSING AT 400 MPA. THEN, THE SPECIMENS WERE SINTERED AT 750 °C VIA HOT PRESSING IN AN ARGON GAS ATMOSPHERE. THE PRESENCE OF A BIMODAL MICROSTRUCTURE, COMPRISED OF SMALL-GRAIN REGIONS SEPARATED BY COARSE-GRAIN ONES, WAS CONFIRMED BY OPTICAL AND SCANNING ELECTRON MICROSCOPIES. THE SAMPLES WITH A BIMODAL MICROSTRUCTURE EXHIBITED AN INCREASE IN THE POROSITY COMPARED WITH THE COMMERCIALLY AVAILABLE PURE TI. IN ADDITION, THE HARDNESS WAS INCREASED WHILE THE YOUNG S MODULUS WAS DECREASED IN THE SPECIMENS WITH 75 WT.% OF THE MILLED POWDERS (20 H).

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°C.

LA0?8SR0?2MNO3 (LSM) PEROVSKITE AS OXYGEN ELECTRODE MATERIAL FOR THE REVERSIBLE SOLID OXIDE FUEL CELLS (RESOFC) WAS SYNTHESIZED BY THE FAST SOLUTION COMBUSTION METHOD AND ASSESSED FOR SUBSEQUENT CALCINATION INFLUENCE. THE MICROSTRUCTURAL, MORPHOLOGICAL, COMPOSITIONAL AND OPTICAL PROPERTIES OF THE OBTAINED MATERIAL WERE ANALYZED WITH X-RAY DIFFRACTION (XRD), HIGH-RESOLUTION TRANSMISSION ELECTRON MICROSCOPY (HR-TEM), SCANNING ELECTRON MICROSCOPY (SEM) COUPLED WITH AN ENERGY-DISPERSIVE X-RAY SPECTROSCOPY DETECTOR (EDS) AND UV?VISIBLE SPEC- TROSCOPY TECHNIQUES. THE XRD RESULTS SHOWED THE COEXISTENCE OF RHOMBOHEDRAL R-3C AND PM-3M POLYMORPHS FOR THE PEROVSKITE PHASE, WITH A DECREASED FRACTION OF THE CUBIC PHASE AS THE TEMPERATURE AND/OR TIME USED FOR THE CALCINATION WERE INCREASED. THE HR-TEM IMAGES CONFIRMED THE EXISTENCE OF THE R-3C AND PM-3M POLYMORPHS FOR THE SAMPLE SUBJECTED TO CALCINATION AT 1300 ?C, SHOWING THAT THE RAPID COMBUSTION METHOD DID NOT ALLOW THE PURE FORMATION OF THE LA0?8SR0?2MNO3 PHASE FOR THE CALCINATION TEMPERATURES BELOW 1400 ?C, DUE TO THE SWIFTNESS OF THE COMBUSTION SYNTHESIS 500 ?C FOR 5 MIN. THE AVERAGE GRAIN SIZE WAS FOUND TO BE INCREASED WITH THE CALCINATION TIME. THE EDS ANALYSIS DEPICTED A BETTER AGREEMENT IN STOICHIOMETRY WITH THE THEORETICAL COMPOSITION. THE APPARENT POROSITY WAS DECREASED WITH THE INCREASE IN THE TEMPERATURE AND CALCINATION TIME DUE TO THE COALES- CENCE OF THE SINTERING PORES. THE SAMPLE OBTAINED AFTER THE CALCINATION AT 1400 ?C FOR 8 H EXHIBITED 1.6% OF POROSITY. THE HARDNESS WAS IMPROVED WITH THE HIGHER CALCINATION TIME AND TEMPERATURE AND REACHED A MAXIMUM VALUE OF 5.7 GPA THAT MERELY MATCHED THE BULK DENSITY. A SIMILAR TREND WAS OBSERVED IN THE TEMPERATURE DEPENDENCE RESISTIVITY STUDIES AND ALL THE SAMPLES PRESENTED A LOW RESISTIVITY OF ~1.2 ? CM IN THE TEMPERATURE RANGE OF 600?700 ?C. THE OPTICAL CHARACTERIZATION EXHIBITED A BROAD ABSORPTION IN 560?660 NM.

A SERIES OF LA0.6SR0.4MNO3 (LSM) PEROVSKITE WAS MADE USING THE RAPID SOLUTION COMBUSTION METHOD, WHICH WAS CALCINED BY VARYING THE TEMPERATURES. IN ORDER TO DETERMINE HOW THE CALCINATION TEMPERATURE AFFECTED THE NANOPOWDERS PRODUCED AND CALCINED AT VARIOUS TEMPERATURES, THEIR MICROSTRUCTURAL, MORPHOLOGICAL, COMPOSITIONAL, OPTICAL, AND ELECTRICAL PROPERTIES WERE ANALYZED USING CORRESPONDING CHARACTERIZATION TOOLS. THE XRD RESULTS SHOWED THE COEXISTENCE OF THE RHOMBOHEDRAL POLYMORPHS R-3C AND PM-3M FOR THE PEROVSKITE PHASE UNDER A CALCINATION TEMPERATURE OF 1400 °C, WHICH WERE ELIMINATED WITH INCREASED CALCINATION TEMPERATURE. THE AVERAGE GRAIN SIZE WAS FOUND TO INCREASE WITH INCREASING CALCINATION TEMPERATURE. THE EDS ANALYSIS SHOWED BETTER AGREEMENT OF THE STOICHIOMETRY WITH THE THEORETICAL COMPOSITION. THE APPARENT POROSITY DECREASED WITH INCREASING TEMPERATURE DUE TO THE COALESCENCE OF SINTERING PORES. THE SAMPLE OBTAINED AFTER CALCINATION AT 1500 °C SHOWED 10.3% POROSITY. THE HARDNESS ALSO IMPROVED WITH INCREASING CALCINATION TEMPERATURE AND REACHED A MAXIMUM VALUE OF 0.4 GPA, WHICH MATCHED THE BULK DENSITY. A SIMILAR TREND WAS OBSERVED IN THE RESISTIVITY STUDIES AS A FUNCTION OF TEMPERATURE, AND ALL THE SAMPLES EXHIBITED A LOW RESISTIVITY OF ~1.4 ?·CM IN THE TEMPERATURE RANGE OF 500?600 °C. THE OPTICAL CHARACTERIZATION SHOWED BROAD ABSORPTION AT 560?660 NM AND BANDWIDTH VALUES BETWEEN 3.70 AND 3.95 EV, ACCORDING TO THE APPLIED HEAT TREATMENT.

BECAUSE OF THE MASSIVE INCREMENT IN SOLAR PLANTS LOCATED IN EXTREME ENVIRONMENTS, STUDYING THE ASSOCIATION OF CLIMATE PARAMETERS AND SOILING IN NATURAL CONDITIONS HAS BEEN NECESSARY. IN THIS WORK, SOLAR GLASS COUPONS WERE EXPOSED TO ENVIRONMENTAL CONDITIONS IN SALVADOR SOLAR PLANT, IN THE ATACAMA DESERT, DURING SUMMER AND WINTER CAMPAIGNS. THE SOILING WAS QUANTIFIED AND CHARACTERIZED, AND THE DEGRADATION OF OPTICAL PROPERTIES OF SOILED COUPONS WAS ALSO MEASURED. REGARDING THE REDUCTION OF THE OPTICAL PROPERTIES OF THE GLASS COUPONS, IT WAS OBSERVED THAT THE DETRIMENTAL EFFECT WAS HIGHER IN SUMMER THAN IN WINTER. A STATICAL ANALYSIS FOUND THAT THIS DIFFERENCE IN SOILING PERFORMANCE IS RELATED TO THE RELATIVE HUMIDITY AND WIND SPEED PRESENT IN EACH CAMPAIGN, MAINLY DUE TO THE DAILY VARIATIONS OF THESE PARAMETERS. PROLONGED PERIODS OF RELATIVE HUMIDITY CLOSE TO 30% PROMOTE THE ADHESION OF PARTICLES TO THE PV GLASS SURFACE AND INHIBIT THEIR RESUSPENSION BY THE ACTION OF THE WIND, I.E., MORE DUST MASS ACCUMULATES. SINCE THE EFFECT OF SOILING IS MORE CRITICAL DURING THE SUMMER PERIOD, THE USE OF A PREVENTING SOILING MITIGATION SYSTEM IS HIGHLY ENCOURAGED, AND THE ADJUSTMENT OF THE CLEANING SCHEDULE ACCORDING TO THE SEASONALITY OF SOILING.

THE SYNTHESIS OF THE NICKEL OXIDE-GADOLINIUM DOPED CERIA (NIO-GDC WITH 65:35 WT. %) NANOCOMPOSITE POWDERS WITH A STOICHIOMETRY OF GD0.1CE0.9O1.95 WAS PERFORMED VIA FAST SOLUTION COMBUSTION TECHNIQUE; USING THREE DIFFERENT MIXING METHODS: (I) CM (METAL CATIONS IN AN AQUEOUS SOLUTION), (II) HM (HAND MORTAR), AND (III) BM (BALL MILLING). THE NANOCOMPOSITE POWDERS WERE CALCINED AT 700 °C FOR 2 H AND CHARACTERIZED BY TRANSMISSION ELECTRON MICROSCOPY (TEM), X-RAY FLUORESCENCE (XRF), AND X-RAY DIFFRACTION XRD. THE TEM AND XRD ANALYSES EVIDENCED THE WELL-DISPERSED NIO AND GDC CRYSTALLITES WITH THE ABSENCE OF SECONDARY PHASES, RESPECTIVELY. LATER, THE CALCINED POWDERS (NIO-GDC NANOCOMPOSITES) WERE COMPACTED AND SINTERED AT 1500 °C FOR 2 H. THE MICROHARDNESS OF THE SINTERED NANOCOMPOSITES VARIES IN ACCORDANCE WITH THE SYNTHESIS APPROACH: A HIGHER MICROHARDNESS OF 6.04 GPA WAS OBTAINED FOR NANOCOMPOSITES SYNTHESIZED THROUGH CM, WHILE 5.94 AND 5.41 GPA WERE OBTAINED FOR BALL-MILLING AND HAND-MORTAR APPROACH, RESPECTIVELY. FURTHERMORE, IT WAS OBSERVED THAT REGARDLESS OF THE LONG TIME-CONSUMING BALL-MILLING PROCESS WITH RESPECT TO THE HAND MORTAR, THERE WAS NO SIGNIFICANT IMPROVEMENT IN THE ELECTRICAL PROPERTIES.

WE REPORT THE SYNTHESIS OF A NEW RANGE OF FERRIHYDRITE-GRAPHENE OXIDE (FH-GO) FOAMS USING CHITOSAN AS CROSS LINKER, WITH VARYING IRON CONTENT (5 WT%, 10 WT%, AND 20 WT% OF FH) AS HIGHLY EFFICIENT ADSORBENTS FOR THE REMOVAL OF ARSENIC (III) (AS(III)) IN AN AQUEOUS SOLUTION. THE SONOCHEMICAL METHODS WERE ADOPTED TO SYNTHESIZE VARIOUS FH-GO FOAMS AND WERE FURTHER CHARACTERIZED BY XRD, SEM, TEM, FTIR, RAMAN, AND XPS TECHNIQUES. THE SYNTHESIZED MATERIALS WERE USED FOR THE REMOVAL OF AS(III) IN BOTH BATCH AND FIXED BED ABSORBENT COLUMN METHODS. THE ADSORPTION ISOTHERM RESULTS SHOWED THAT THE 10 WT% OF FH-GO FOAMS DEMONSTRATED A SUPERIOR ADSORBENT FOR THE AS(III) WITH HIGH ADSORPTION CAPACITIES THAN THAT OF THE OTHER TWO FH-GO FOAMS (5 WT% AND 20 WT% OF FH). MOREOVER, 10 WT% OF FH-GO FOAMS WAS ALSO DEMONSTRATED TO BE NEARLY A COMPLETE (>98.4%) REMOVAL OF AS(III) IONS AT NEUTRAL PH 7. THE ADSORPTION ISOTHERM FITTED VERY WELL WITH THE LANGMUIR MODEL WITH THE HIGHEST ACCURACY DATA FOR ALL THE SYNTHESIZED ADSORBENT MATERIALS. IN ADDITION, THE FIXED BED ABSORBENT COLUMN METHOD WAS ALSO ADOPTED FOR THE REMOVAL OF AS(III) IONS IN THE WATER SAMPLE, WHICH SHOWED > 99.2% OF REMOVAL EFFICIENCY. THE OUTSTANDING ADSORPTION CAPABILITIES, ALONG WITH THEIR EASY AND LOW-COST SYNTHESIS, MAKE THESE KINDS OF ADSORBENTS EXTREMELY CAPABLE FOR COMMERCIAL APPLICATIONS IN WASTEWATER TREATMENT AND DRINKING WATER PURIFICATION.

THE GOETHITE (ALPHA-FEOOH) NANOPARTICLES WERE WRAPPED ON THE REDUCED GRAPHENE OXIDE (RGO) TO SYNTHESIZE THE ALPHA-FEOOH/RGO NANOCOMPOSITES. THE NANOCOMPOSITES (NCS) WERE INITIALLY EXAMINED FOR THEIR OPTICAL, STRUCTURAL, AND MORPHOLOGICAL PROPERTIES. THE XRD DATA OBTAINED THE CRYSTALLITE SIZE OF THE ALPHA-FEOOH, SHOWED THAT THE AVERAGE CRYSTAL SIZE FOR PRISTINE ALPHA-FEOOH AND ALPHA-FEOOH/RGO NANOCOMPOSITES WERE ABOUT 85 AND 90 NM, RESPECTIVELY. THE TRANSMISSION ELECTRON MICROSCOPE CONFIRMED THE NANOPARTICLES (NPS) WERE EVENLY DISTRIBUTED THROUGHOUT THE REDUCED GRAPHENE OXIDE SHEETS. THE NANOCOMPOSITES IMPROVED GLASSY CARBON ELECTRODES (GCE), MAKING THEM EFFICIENT SENSORS FOR DETECTING THE ARSENIC(III) (AS+3) IN A PH 5 PHOSPHATE BUFFER SOLUTION WITH AN AG/AGCL REFERENCE ELECTRODE. THE DETECTION LIMIT FOR AS+3 WAS 0.07 MU GL-1 AND THE RESULTING SENSITIVITY WAS 0.39 MU A-1 MU GL-1 IN THE LINEAR DYNAMIC RANGE OF 0.1-10 MU GL-1. THE ALPHA-FEOOH/RGO/GCE WAS MORE SENSITIVE THAN ITS ORIGINAL AND SHOWED A SYNERGISTIC EFFECT DUE TO THE INFLUENCE OF ALPHA-FEOOH ON THE PROPERTIES OF RGO. THE ALPHA-FEOOH/ RGO NCS-MODIFIED GCE ELECTRODE PERFORMED AS A PROMISING SENSOR, BY SEPARATING THE COMMON INTERFERING IONS. MOREOVER, THE MODIFIED ELECTRODE EXHIBITED REMARKABLE STABILITY, REPEATABILITY, AND POTENTIAL REAL-TIME APPLI-CATION TOWARDS THE DETECTION OF ARSENIC(III). ADDITIONALLY, THE PROPOSED APPROACH HAS BEEN SUCCESSFULLY APPLIED TO THE DETECTION OF AS+3 IN THE REAL WATER SAMPLE.

EXPERIMENTAL THERMODYNAMIC MEASUREMENTS IN MULTICOMPONENT SYSTEMS EXHIBIT HIGH COMPLEXITY. THEORETICAL CALCULATIONS BY EXTRAPOLATION OF CONSTITUTIVE BINARY SYSTEMS ARE AN EXCELLENT TOOL TO ESTIMATE THE THERMODYNAMIC PROPERTIES IN TERNARY OR QUATERNARY SYSTEMS. IN THIS CONTEXT, THE MIEDEMA AND BAKKER SEMI-EMPIRICAL MODELS ARE GOOD TO ESTIMATE THE ENTHALPY OF MIXING OR FORMATION. THIS WORK PRESENTS A NEW SOFTWARE, MAAT (MATERIALS ANALYSIS APPLYING THERMODYNAMICS), DESIGNED TO CALCULATE SELECTED THERMODYNAMIC PROPERTIES OF BINARY AND TERNARY SYSTEMS. THE MAAT IS A FREE SOFTWARE THAT CAN BE DOWNLOAD FROM WWW.RPM.USM.CL. THE MAAT SOFTWARE IS A PLATFORM, WRITTEN IN MATLAB, WHICH RUNS IN 32/64 BITS WINDOWS SYSTEMS. THE MAIN CHARACTERISTICS OF THE SOFTWARE ARE: I) CALCULATION AND PLOTTING GIBBS FREE ENERGY OF MIXING CURVES OF RANDOM SOLID SOLUTIONS, AMORPHOUS AND INTERMETALLIC COMPOUNDS, II) CALCULATION AND PLOTTING THE ACTIVITY OF COMPONENTS IN SOLID SOLUTIONS, AND III) ANALYSIS OF THE EFFECT OF ADDITIONAL TERMS OVER THE GIBBS FREE ENERGY OF MIXING OF RANDOM SOLID SOLUTIONS, SUCH AS CENTRIFUGAL FIELD, GRAIN SIZE AND DISLOCATIONS. IN THIS WORK, THE THERMODYNAMIC CALCULATIONS PERFORMED WITH MAAT ARE COMPARED WITH EXPERIMENTAL DATA IN FOUR CASES: FORMATION OF SOLID SOLUTION (CU-MO-CR SYSTEM), FORMATION OF AMORPHOUS PHASE (TI-TA-SN SYSTEM), FORMATION OF INTERMETALLIC COMPOUND (CU-NB-CO SYSTEM) AND EFFECT OF CENTRIFUGAL FIELD ON FORMATION OF SOLID SOLUTION (CU-CR SYSTEM). FOR ALL SYSTEMS ANALYZED, THE CALCULATIONS MADE USING MAAT GAVE RESULTS THAT ARE COMPARABLE WITH EXPERIMENTAL DATA.

THE COPPER (CU) MATRIX COMPOSITES HAVE BEEN CONSTANTLY INVESTIGATED TO ADDRESS THE REQUIREMENTS FOR THEIR UTILITY IN FUNCTIONAL APPLICATIONS. AMONG THE VAST AVAILABLE REINFORCEMENTS, THE MAX PHASES ARE PROMISSORY TO BE EFFICIENT TO STRENGTHENING THE CU, WITHOUT A DRASTIC REDUCTION OF ITS ELECTRICAL CONDUCTIVITY. IN THE PRESENT REPORT, THE SYNTHESIS OF NOVEL TI2ALN MAX PHASE REINFORCED COPPER MATRIX COMPOSITES (CU-MAX COMPOSITES) BY USING HOT PRESSING ARE REPORTED. THE MICROSTRUCTURE OF THE COMPOSITES AND THE EVIDENCED REACTION BETWEEN THE MATRIX AND REINFORCEMENT ARE DISCUSSED WITH THE ASSESSMENT OF SCANNING ELECTRON MICROSCOPY (SEM), TRANSMISSION ELECTRON MICROSCOPY (TEM) AND X-RAY DIFFRACTION (XRD). IT WAS NOTICED THAT THE DIFFUSION OF THE AL AND TI ATOMS OF THE TI2ALN PARTICLES INTO THE CU MATRIX GENERATED A MICROSTRUCTURE COMPOSED OF CU, CU (AL, TI) SOLID SOLUTION AND TI-CU-N PARTICLES WITH A NANO-LAMELLAR STRUCTURE. THE RESULTS OF THE MECHANICAL, PHYSICAL AND ELECTRICAL PROPERTIES INDICATED THAT THE DENSITY, HARDNESS AND FLEXURAL STRENGTH OF THE COPPER WERE INFLUENCED SIGNIFICANTLY WITH LOW AMOUNTS OF REINFORCEMENT. THE MECHANICAL STRENGTH SHOWED A SUBSTANTIAL INCREMENT FROM 355 TO 855 MPA WHILE THE DUCTILITY WAS MAINTAINED, BY ADDING 5 WT% OF TI2ALN INTO THE CU, WHEREAS THE ELECTRICAL CONDUCTIVITY WAS REDUCED.

THE TRANSITION METAL CHALCOGENIDE (TMC) NANOSHEETS ARE A NEW CLASS OF 2D MATERIALS THAT PLAY AN INCREASINGLY IMPORTANT ROLE IN THE VARIETY OF ELECTRONIC DEVICES. IN THE PRESENT WORK, TUNGSTEN SULFIDE (WS2) NANOSHEETS WERE SUCCESSFULLY SYNTHESIZED BY THE ONE-STEP MICROWAVE IRRADIATION METHOD (850 W, ANTON PAAR MONOWAVE 200) WITHOUT USING ANY TEMPLATES. THE STRUCTURAL FORMATION OF THE WS2 WAS PRIMARILY CONFIRMED BY THE X-RAY POWDER DIFFRACTION ANALYSIS AND THE MORPHOLOGY WAS OBSERVED BY THE FIELD EMISSION SCANNING ELECTRON MICROSCOPY. THE RAMAN, X-RAY PHOTOELECTRON, AND ENERGY-DISPERSIVE X-RAY SPECTROSCOPIES WERE USED TO INVESTIGATE THE ORDERED NATURE AND ELEMENTAL COMPOSITION OF THE WS2 NANOSHEETS. THE SYNTHESIZED WS2 SHOWED AMENDABLE ELECTROCATALYTIC ACTIVITY FOR THE OXYGEN REDUCTION REACTION IN AN ALKALINE MEDIUM WITH THE ONSET POTENTIAL OF 0.82 V AND THE NUMBER OF ELECTRONS TRANSFERRED FOR THE REACTION AS 3.29. ALL OF THESE FACTS POINT TO THE WS2 NANOSHEETS BEING A PROMISING NOBLE-METAL -FREE ORR CATHODE CATALYST FOR THE FUEL CELLS.

IN THIS WORK, WE PREPARED LA1?XSRXGA1?YMGYO3 (LSGM) BY THE FAST COMBUSTION METHOD AND ASSESSED THE ELECTRICAL PROPERTIES WITH RESPECT TO THE COMPOSITION AND SINTERING TEMPERATURE (1200, 1300, AND 1400 °C BY 6 H) AS AN ELECTROLYTE MATERIAL FOR THE REVERSIBLE SOLID OXIDE CELLS (RESOCS). FOR THE PREPARATION OF SAMPLES, TWO DIFERENT FUELS, SUCH AS TARTARIC ACID (TA) AND CITRIC ACID (CA), WITH CORRESPONDING NITRATE SALTS AS PRECURSORS, WERE ADOPTED FOR THE FAST COMBUSTION METHOD (AT 500 °C FOR 10 MIN). FROM THE X-RAY DIFRACTOGRAMS, TWO MAIN PHASES CORRESPONDING TO LSGM ORTHORHOMBIC (SPACE GROUP IMMA) AND LSGM-CUBIC (SPACE GROUP PM-3 M) WERE IDENTIFED. FROM THE LITERATURE, BOTH STRUCTURES ARE REPORTED AS HIGH OXYGEN ION CONDUCTIVE SPECIES, BUT NORMALLY THEY ARE NOT REPORTED TO APPEAR TOGETHER. ADDITIONALLY, IN SOME CASES, AN ISOLATING (SECONDARY) PHASE OF LASRGAO4 IN A LOW CONCENTRATION

THE DEVELOPMENT OF HIGH-ENTROPY ALLOYS HAS BEEN HAMPERED BY THE CHALLENGE OF EFFECTIVELY AND VERIFIABLY PREDICTING PHASES USING PREDICTIVE METHODS FOR FUNCTIONAL DESIGN. THIS STUDY VALIDATES REMARKABLE PHASE PREDICTION CAPABILITY IN COMPLEX MULTICOMPONENT ALLOYS BY MICROSTRUCTURALLY PREDICTING TWO NOVEL HIGH-ENTROPY ALLOYS IN THE FCC + BCC AND FCC + BCC + IM SYSTEMS USING A NOVEL ANALYTICAL METHOD BASED ON VALENCE ELECTRON CONCENTRATION (VEC). THE RESULTS ARE COMPARED WITH MACHINE LEARNING, CALPHAD, AND EXPERIMENTAL DATA. THE KEY FINDINGS HIGHLIGHT THE HIGH PREDICTIVE ACCURACY OF THE ANALYTICAL METHOD AND ITS STRONG CORRELATION WITH MORE INTRICATE PREDICTION METHODS SUCH AS RANDOM FOREST MACHINE LEARNING AND CALPHAD. FURTHERMORE, THE EXPERIMENTAL RESULTS VALIDATE THE PREDICTIONS WITH A RANGE OF TECHNIQUES, INCLUDING SEM-BSE, EDS, ELEMENTAL MAPPING, XRD, MICROHARDNESS, AND NANOHARDNESS MEASUREMENTS. THIS STUDY REVEALS THAT THE ADDITION OF NB ENHANCES THE FORMATION OF THE SIGMA (?) INTERMETALLIC PHASE, RESULTING IN INCREASED ALLOY STRENGTH, AS DEMONSTRATED BY MICROHARDNESS AND NANOHARDNESS MEASUREMENTS. LASTLY, THE OVERLAPPING VEC RANGES IN HIGH-ENTROPY ALLOYS ARE IDENTIFIED AS POTENTIAL INDICATORS OF PHASE TRANSITIONS AT ELEVATED TEMPERATURES.

TITANIUM (TI) AND ITS ALLOYS ARE USED FOR BIOMEDICAL APPLICATIONS BECAUSE OF THEIR HIGH RESISTANCE TO CORROSION, GOOD STRENGTH-TO-WEIGHT RATIO, AND HIGH FATIGUE RESISTANCE. HOWEVER, A PROBLEM THAT COMPROMISES THE PERFORMANCE OF THE MATERIAL IS THE MISMATCH BETWEEN YOUNG?S MODULUS OF TI AND THE BONE, WHICH BRINGS ABOUT STRESS SHIELDING. ONE STRATEGY THAT HAS BEEN INVESTIGATED TO REDUCE THIS DIFFERENCE IS THE MANUFACTURE OF TI-BASED FOAMS, USING POWDER METALLURGY (PM) METHODS, SUCH AS THE SPACE-HOLDER TECHNIQUE. HOWEVER, IN THE UNIAXIAL COMPACTION, BOTH NON-UNIFORM DENSITY DISTRIBUTION AND MECHANICAL PROPERTIES REMAIN BECAUSE OF THE COMPACTION METHOD. THIS WORK STUDIES THE INFLUENCE OF COMPACTION BY ADOPTING A FLOATING-ACTION DIE RELATED TO A SINGLE-ACTION DIE (SAD), ON THE DENSITY OF GREEN AND SINTERED TI FOAMS WITH POROSITIES AROUND 50 VOL.% CHARACTERIZED BY OPTICAL MICROSCOPY, ULTRASOUND ANALYSIS, COMPRESSION TESTS, AND MICROHARDNESS. THE COMPACTION PROCESS EMPLOYING A FLOATING-ACTION DIE GENERATES TI FOAMS WITH A HIGHER DENSITY UP TO 10% WITH MORE CONTROL OF THE SPACER PARTICLE ADDED COMPARED TO THE SINGLE-ACTION DIE. FURTHERMORE, COMPACTION METHOD HAS NO RELEVANT EFFECT ON MICROHARDNESS AND YOUNG?S MODULUS, WHICH ALLOWS GETTING BETTER CONSOLIDATED SAMPLES WITH ELASTIC MODULES SIMILAR TO THOSE OF HUMAN BONE.