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•High REE contents in the bauxite deposits from Songqi area of Henan Province, north China.•The rare earth elements appear in various modes of occurrences.•Most REE are adsorbed in ...the form of ions on the surface of clays and diaspore.•Some REE occur as xenotime, bastnaesite, and other P-REE minerals.
High concentrations of rare earth elements (REE) are found in the bauxite deposits in the Songqi area of Henan Province, North China. However, no studies have been carried out on the occurrences of REE in these bauxite ores. In this study we explored the REE occurrence and their possible enrichment mechanism in the Songqi bauxite deposits using petrographic observation, X-ray diffraction (XRD), scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), and LA-ICP-MS techniques. The major aluminum-rich ore mineral in the Songqi bauxite deposits is diaspore, and other coexisting minerals include clay mineral aggregates, with minor amounts of hematite, pyrite, anatase, and zircon. The bauxite ores are rich in REE and also some other critical metals (Li, Zr, Nb, and Ga). Most of the REE are adsorbed in the form of ions on the surface of clay minerals and diaspore, and some heavy rare earth elements (HREE) exist in the form of xenotime. The SEM-EDS and LA-ICP-MS analyses show that REE is closely related to the content of P and therefore it is possible that other dispersed and minor P-bearing rare earth minerals may occur in the bauxite deposits except for the possible co-adsorption of P and REE in the clays and diaspore.
//ABSTRACT IN SPANISH: Mediante una combinación de la técnica MEB-EDS se pudo estudiar un fragmento de la piel tatuada y no tatuada de la Señora de Cao, una mujer de la alta clase social mochica ...(mochica temprano). La sonda EDS aplicada a la zona con tatuaje indica la utilización de óxido ferroso (FeO). Según la información arqueobotánica y el hallazgo de momias tatuadas que están sosteniendo frutos de "jagua" Genipa americana L., es posible que este fruto de origen selvático haya servido como materia prima para ser utilizada en tatuar a la Señora de Cao. //ABSTRACT IN ENGLISH: Through a combination of SEM-EDS technique could study a fragment of tattooed and non tattooed skin of the Lady of Cao, a woman of high social class Moche (Mochica early). EDS probe applied to the area with tattoo indicates the use of ferrous oxide (FeO). According to the information and finding archaeobotany tattooed mummies are holding fruits of "Jagua" Genipa americana L., is possible that this fruit of wild origin have served as raw material for use in tattooing the Lady of Cao.
Abstract Objectives To characterize the microstructure and composition of two different composites, and to determine their influence on the physical properties and fracture behavior. Methods The ...microstructure and composition of a microhybrid (Filtek Z250™-Z2) and a nanofill (Filtek Supreme™-SU) composite were analyzed using scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS). Filler wt% was determined by thermogravimetric analysis. Hardness ( H ) and degree of conversion (DC) were evaluated at top and bottom surfaces of 2-mm thick specimens, and the dynamic elastic modulus ( E ) was determined with ultrasonic waves. Bar specimens ( n = 30) were subjected to flexure loading and flexural strength ( σf ) was calculated (MPa). Fractographic analysis (FA) was performed to determine the fracture origin ( c ) for calculation of fracture toughness ( KIc ), and these results were compared to those from the single edge notch beam (SENB) method. Results were statistically analyzed using two-way ANOVA, Student's t -test and Weibull analysis ( α = 0.05). Results Z2 had higher filler wt%, H , E and DC at 2-mm depth as compared with SU. The fracture behavior ( σf and KIc ) and the structural reliability ( m ) of the composites were similar. Results of KIc tested by SENB or calculated from fracture surfaces from flexure testing were similar. Significance The microstructural organization of the composites determines their physical properties, in spite of the similar filler content. In contrast, the microstructure did not influence the fracture behavior and the structural reliability of these highly filled composites. FA was shown to be a reliable method for determining the KIc of composites.
In this research the oxidation of ASTM A335 P92 steel and the effect of 40% K2SO4 - 60% NaCl salt mixture at temperatures of 500ºC to 700ºC in intervals of 50°C with exposure times of 1,3,10, 30,100 ...and 150 hours were evaluated using the standard standardized by the European Federation of Corrosion. Metallographic analysis and hardness analysis were performed before and after the test to identify the possible structural change; evidence of x-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS) were performed to determine the corrosion products present in the steel. By SEM-EDS analysis it is shown that corrosive species such as Cl--, SO4-- do not react with the alloying elements of steel. It was also noted that the oxide layers formed showed stability, and good adhesion which confirms the oxides protection on the metal. The "gained weight by salts deposition" curves showed a parabolic behavior, typical of high temperature materials.
In the paper, the SEM and EDS study results of the surface coatings formed on the niobium and titanium alloys (TNZ, NiTi, Ti6Al4V) after the Plasma Electrolytic Oxidation (PEO), also known as Micro ...Arc Oxidation (MAO), are described. For the experiment of the PEO treatment, a non-conventional electrolyte, based on the concentrated orthophosphoric acid, was used. Copper -enriched surface coatings on the biomaterials after the PEO were obtained and studied. General surface characteristics, regarding the metallic biomaterials after the PEO treatment, with the significant differences of the results, have been displayed and statistically developed. Keywords: Plasma Electrolytic Oxidation (PEO); Micro Arc Oxidation (MAO); SEIM; EDS Analysis; Niobium; TNZ (Ti-Nb-Zr); NiTi; Ti6Al4V U radu su opisani rezultati SEM i EDS analize povrsinskih slojeva nastalih na legurama niobija i titanija (TNZ, NiTi, Ti6Al4V) nakon plazma elektroliticke oksidacije (PEO), poznate i kao mikro lucna oksidacija (Micro Arc Oxidation--MAO). Za eksperiment PEO postupka upotrebljen je nekonvencionalni elektrolit, temeljen na koncentriranoj ortofosfornoj kiselini. Nakon PEO dobiveni su i proucavani bakrom obogaceni povrsinski slojevi na biomaterijalu. Prikazane su i statisticki obradene opce znacajke povrsine u odnosu na kovinske biomaterijale nakon PEO postupka, uz znacajne razlike u rezultatima. Kljucne rijeci: plazma elektroliticka oksidacija (PEO), mikro lucna oksidacija (MAO), SEM, EDS analiza, niobij, TNZ (Ti-Nb-Zr); NiTi; Ti6Al4V
Synthesis of NiMo Anderson-type polyoxomolybdates supported on ZnO-modified V2O5/Al2O3 was evaluated in the oxidative desulfurization of DBT. The catalyst was characterized by XRF, B.E.T specific ...area, FTIR, surface acidity by potentiometric titration with n-Butylamine and SEM-EDS. XRF analysis revealed no significant changes between the experimental (Ni:Mo 1:7) and theoretical (Ni:Mo 1:6) molar ratios. The BET specific area followed the order ɣ-Al2O3 (207 m2/g) > ɣ-Al2O3-ZnO (185 m2/g) > VNiMo/ɣ-Al2O3-ZnO (74 m2/g) > VNiMo/ɣ-Al2O3 (56 m2/g). FTIR showed bands of Mo-O2 and N-H bonds assignable to polyoxomolybdates. The VNiMo/ɣ-Al2O3 catalyst (57.7 μeq/m2) has a higher density of acid sites than the VNiMo/ɣ-Al2O3-ZnO catalyst (38.2 μeq/m2). SEM revealed laminar texture and irregular morphology, while its EDS analysis indicates the presence of elements that constitute solids: V, Ni, Mo, Al, Zn. The DBT ODS activity of VNiMo/ɣ-Al2O3 is higher than VNiMo/ɣ-Al2O3-ZnO by 25%.
La síntesis de polioxomolibdatos tipo Anderson de NiMo soportados sobre V2O5/Al2O3 modificada con ZnO se evaluó en la desulfuración oxidativa de DBT. El catalizador se caracterizó por FRX, área específica BET, IRTF, acidez superficial por titulación potenciométrica con n-butilamina y MEB-EDS. El análisis FRX reveló que no hay cambios significativos entre las relaciones molares experimentales (Ni:Mo 1:7) y teóricas (Ni:Mo= 1:6). El área específica BET siguió el orden ɣ-Al2O3 (207 m2/g) > ɣ-Al2O3-ZnO (185 m2/g) > VNiMo/ɣ-Al2O3-ZnO (74 m2/g) > VNiMo/ɣ-Al2O3 (56 m2/g). FTIR mostró bandas correspondientes a los enlaces Mo-O2 y N-H asignables a polioxomolibdatos. El catalizador VNiMo/ɣ-Al2O3(57.7 μeq/m2) posee mayor densidad de sitios ácidos que el catalizador VNiMo/ɣ-Al2O3-ZnO (38.2 μeq/m2). MEB reveló textura laminar y morfología irregular, mientras que su análisis EDS indica la presencia de elementos que constituyen a los sólidos: V, Ni, Mo, Al, Zn. La actividad ODS de DBT de VNiMo/ɣ-Al2O3 es mayor que VNiMo/ɣ-Al2O3-ZnO en un 25 %.
Five variations of the monetite (M) synthesis were evaluated modifying the stirring, the phosphoric acid addition rate, the homogeneity and the drying temperature. Products were assessed by means of ...XRD, FTIR, SEM-EDS analysis and chemical assay of Ca/P (calcium by titration with potassium permanganate and phosphorus by colorimetric assessment of the molybdenum blue complex). X-ray diffraction, infrared spectroscopy and Ca/P ratio indicate that the synthesized phosphate corresponds to pure monetite. It was found that the most influential factors affecting composition, crystal size and Ca/P were stoichiometry and ball milling mechanoactivation.
Offshore structures serve in harsh environment here the combined effects of freeze-thaw cycles and Cl− erosion severely degrade the bond performance between steel bars and concrete, significantly ...reducing the structures' service life. This paper investigates the bond performance of marine concrete with nano-particles to steel bars under the simultaneous influence of Cl− erosion and freeze-thaw cycles. The bond-slip (τ-s) curves are derived from pull-out tests, in order to reveal the mechanism of nano-particles to improve the bond performance of reinforced concrete under the action of both Cl− erosion and freeze-thaw cycles, the microstructure of the bond interface between steel bar and concrete is examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and mercury impression test (MIP). The test results show that adding nano-SiO2 and nano-TiO2 enhance the cracking bond strength (τs), ultimate bond strength (τu), ultimate slip value (Su), and residual bond strength (τr) of reinforced concrete. The optimal content for both nano-SiO2 and nano-TiO2 are 2 %, with nano-SiO2 showing superior effect. When Cl− erosion and the number of freeze-thaw cycles are certain (N = 100), the τu values of NSC20 and NTC20 are increased by 26.25 % and 16.68 %, and the Su values are increased by 25.30 % and 22.89 %, respectively, compared with PC. The results of the SEM and EDS analyses indicate that nano-particles promote C–S–H gel formation, reduce porosity and optimize concrete's pore structure, enhance shear strength at the bonding surface, reduce Cl− content at the interface, slow down the corrosion of the steel bars. Thus, the addition of nano-particles significantly improves the bond performance of reinforced concrete under the action of both Cl− erosion and freeze-thaw cycles, which is vital for enhancing the load-bearing capacity and seismic performance of engineering structures.
•Bonding properties of nanoparticle-containing concrete to steel reinforcement under salt freezing cycles.•Effect of nanoparticles and number of freeze-thaw cycles on bond slip curves and bond eigenvalues.•The macroscopic damage law of drawing specimens under different salt-freezing cycles caused by nanoparticles was analyzed.•Microstructural changes of reinforcement-concrete bonding surfaces by SEM, EDS and MIP microtests.
In this work synthesized magnetite and hematite were included in the Electroless Ni-P coatings deposited on steel AISI 304 to improve their resistance to degradation at high temperatures. The ...deposition was done on cylindrical pieces of 12.7 mm diameter and 3 mm thickness. The coatings are oxidized in the presence of a constant fow of air to 700°C at a time of 2 hours with a heating rate of 10°C/min. Then they were analyzed with SEM, EDS and DRX. For the analysis of impedance spectroscopy (IS) in solid state was used a temperature range between 300°C and 700°C. The SEM and EDS analysis showed that the oxide layer formed on all coatings consisted mainly of NiO and Ni3P. By evaluating the electrical resistance was found that hematite coatings offered better resistance to electrical fow those other coatings.
En este trabajo se incluyeron magnetitas y hematitas sintetizadas, en la deposición electroless de recubrimientos Ni-P sobre acero AISI 304 para mejorar su resistencia a la degradación a temperaturas elevadas. La deposición se llevó a cabo sobre probetas cilíndricas de 12,7 mm de diámetro por 3 mm de espesor. Los recubrimientos se oxidaron en presencia de un fujo de aire constante a 700° C por un tiempo de 2 horas con una velocidad de calentamiento de 10°C/min. Posteriormente fueron analizados con SEM, EDS y DRX. Para el análisis de espectroscopía de impedancias (IS) en estado sólido se trabajó en un intervalo de temperatura entre 300° y 700° C. Los análisis de SEM y EDS mostraron que la capa de óxido formada sobre todos los recubrimientos estaba compuesta principalmente por NiO y Ni3P. Mediante la evaluación de la resistencia eléctrica se encontró que los recubrimientos con hematita ofrecían una mejor resistencia al paso de la corriente que los demás recubrimientos.
Valutare le caratteristiche microscopiche dei cementi endodontici MTA disponibili in commercio e di un cemento di Portland.
Analisi su quattro varietà di MTA: Ogna Aureoseal
®, Proroot white MTA
®, ...Angelus white e gray MTA
® e un cemento di Portland. I campioni, previo esame in diffrazione X, sono stati consolidati; i provini a cemento solidificato sono stati inglobati in una resina epossidica e lucidati in superficie: questo ha permesso un’osservazione SEM-EDS per evidenziarne la struttura e la natura chimica e mineralogica.
Le analisi mostrano significative differenze tra i vari tipi di MTA presi in esame e tra questi e il cemento di Portland usato come riferimento.
I cementi utilizzati a scopo odontoiatrico hanno granuli di minori dimensioni, una maggiore idratazione e un minor contenuto di ferro e zolfo. Tra i costituenti mineralogici caratteristici del MTA si riscontrano agenti radio-opacizzanti (Bi
2O
3 e CaWO
4). Una sostanziale differenza tra i cementi MTA è la quantità variabile nel contenuto di magnesio e alluminio che, dopo il consolidamento, presentano una granulometria inferiore nei campioni Ogna Aureoseal
® e Proroot white MTA
®; la presenza di apatite e tungstato di calcio (CaWO
4) è invece caratteristica del cemento MTA Ogna Aureoseal
®.
Le differenze tra i campioni MTA e tra questi e il cemento di Portland sono significative sia a livello di tessitura microscopica sia di composizione chimica.
To determine the mineralogical, chemical, and microtextural differences between commercially available MTA products, clarifying common differences with Portland and between each other.
The study was done on four commercially available MTA cements, that is Ogna Aureoseal
®, Proroot white MTA
®, Angelus white and gray MTA
® and on a commercial Portland cement. After preliminary X-ray diffraction characterization of the powder, the samples were consolidated following the same procedure used in clinical practice. The consolidated material was embedded in epoxy and polished, and subsequently investigated, by means of SEM-EDS analysis of back-scattered electron images on all samples and of quantitative compositional mapping on MTA.
The MTA and Portland cements differ for the grain size, the hydration rate, and homogeneity of the set products, and for lower Fe and S content in MTA. Previously reported presence of opacizing agents (Bi
2O
3 and CaWO
4) was confirmed in all samples, whereas low Al content was not observed in all MTA. Although the MTA products are all mainly composed by di-calcium and tri-calcium silicates, the post-setting texture and the chemical and mineralogical constitution differ. Finer texture was observed in Ogna Aureoseal
® and Proroot white MTA
®; in Ogna Aureoseal
® the presence of apatite and Ca-tungstate was reported; Mg and Al content changed in samples, following the clinker composition.
Significant differences exist between Portland cement and MTA, but also among different MTA formulations. MTA products can be classified as a form of Portland cement, specifically modified for dentistry purposes.
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