scholarly journals Understanding the Mechanism of Arsenic Mobilisation and Behaviour in Tailings Dams

2017 ◽  
Vol 17 (1) ◽  
pp. 85-89
Author(s):  
B. Koomson ◽  
E. K. Asiam ◽  
W. Skinner ◽  
J. Addai-Mensah
Keyword(s):  
Electron Microscopy ◽  
Heavy Metals ◽  
Scanning Electron Microscopy ◽  
Chemical Composition ◽  
Energy Dispersive Spectroscopy ◽  
X Ray ◽  
Tailings Dams ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Scanning Electron

This study was carried out on leaching of tailings at 30 ᵒC and 40 ᵒC. The mineralogical and chemical composition of the tailings material were determined by Quantitative X-Ray Diffractometry (QXRD) and Scanning Electron Microscopy combined with Energy Dispersive Spectroscopy (SEM-EDAX). The study revealed that the tailings contain sulphides (arsenopyrite and pyrite) which can leach to produce arsenic (As) and other ions in solution. The acid released during leaching depends on the temperature of leaching. More acid was produced at higher temperature (40 ᵒC) than lower temperature (30 ᵒC). It was established that arsenic precipitation from solution was higher at higher temperature (40 ᵒC) than lower temperature (30 ᵒC). Mimicking the study in a typical tailings environment, it could be proposed that As mobilisation will be enhanced at lower temperature (30 ᵒC) than at higher temperature (40 ᵒC). Keywords: Tailings, Leaching, Arsenopyrite, Heavy metals and Temperature

scholarly journals EFECTS OF CHEMICAL COMPOSITION ON THE MICROSTRUCTURE AND PROPERTIES OF THE CU-Ge-Sb ALLOYS

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Dejan Gurešić ◽  
Aleksandar Đorđević ◽  
Aleksandar Marković ◽  
Milica Tomović ◽  
Nadežda Talijan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Scanning Electron Microscopy ◽  
Chemical Composition ◽  
Diffraction Analysis ◽  
Eddy Current ◽  
Energy Dispersive Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

In the current study a ternary Cu-Ge-Sb system has been experimentally assessed. Chemical andphase compositions of the alloy samples from three vertical sections Cu-GeSb, Ge-CuSb and Sb-CuGe were studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy(EDS) and confirmed by X-ray diffraction analysis (XRD). Hardness of the alloys was measured byBrinell method while hardness of phases was measured using micro Vickers method. Electricalconductivity of the studied alloys was measured using eddy current instrument. Based onexperimentally determined values iso-lines of hardness and electrical conductivity for the wholeternary system were calculated using assumed mathematical models.

Preparation of Pd /α–Al2O3 and Pd-Ag/α–Al2O3 Membranes by Electroless Plating and Permeation Measurements

2012 ◽  
Vol 1372 ◽  
Author(s):  
L. Ortiz-Martínez ◽  
M. Torres-Rodríguez ◽  
M. Gutiérrez-Arzaluz
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electroless Plating ◽  
Energy Dispersive Spectroscopy ◽  
Ceramic Composite ◽  
Composite Membranes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Α Al2o3 ◽  
Scanning Electron

ABSTRACTIn this work, the synthesis of dense Pd/α–Al2O3 and Pd-Ag/α–Al2O3 ceramic composite membranes was done through the sequential electroless plating technique of Pd and Ag. The precursors are solutions of PdCl2 and AgNO3 and N2H4 salts, as reducing agent. The membranes were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The permeation tests of H2 and N2 was carried out at 20 psi of pressure and at 25°C, resulted πH2=5.2x10-9 mol H2/m2·s·Pa and πN2=8.2x10-10 mol N2/m2·s·Pa.

scholarly journals Analysis of working surface in new manual and rotary endodontic instruments (scanning electron microscopy)

2020 ◽  
Vol 148 (7-8) ◽  
pp. 398-403
Author(s):  
Milica Jovanovic-Medojevic ◽  
Martina Pelemis ◽  
Jelena Neskovic ◽  
Marijana Popovic-Bajic ◽  
Djordje Stratimirovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Statistical Analysis ◽  
Chemical Composition ◽  
Common Type ◽  
X Ray ◽  
Working Surface ◽  
Surface Metal ◽  
Scanning Electron ◽  
Common Defect

Introduction/Objective. The objective of this study is to use scanning electron microscopy (SEM) to analyze working surfaces of new manual and rotary endodontic instruments and to check possible existence of manufacture dirt particles or defects on the working surface. Methods. In this study, we used three sets of new manual instruments: K-File, KF (Dentsply Maillefer, Switzerland) and Hedstorm Files, HF (SybronEndo Co, USA) and three sets of mechanical Ni-Ti instruments ? type K3 (SybronEndo Co, USA) and BioRaCe (FKG DENTAIRE Swiss Dental Products, Switzerland). The instruments were analyzed using SEM method at 170 ? magnification while semi-quantitative energy dispersive x-ray analysis was used to determine chemical composition of dirt particles. Fisher test (p < 0.05) was applied in statistical analysis. Results. Results showed that none of the instruments were defect-free. The most common defect type was the presence of metal strips, which were noticed at the surface of all tested instruments. Debris was present on all manual and only one type of mechanical instruments, K3 (39% in the apical and 33% in the middle third). Fretting was noticed in all manual KF and all mechanical instruments of the K3 group. Pitting was common in all manual instruments, KF (33% in the apical and 39% in the middle third) and HF (11% in the apical and 6% in the middle third). Corrosion of the working surface, metal flash, and disruption of the cutting edge were marked only in the KF group. Conclusion. Manufacture defects were noticed in all instruments and the most common type of irregularity were metal strips. Electropolished surface of BioRaCe instruments showed no debris of organic origin.

scholarly journals Comparison of chemical composition of packable resin composites by scanning electron microscopy

2005 ◽  
Vol 13 (1) ◽  
pp. 67-71 ◽  
Author(s):  
Ana Amélia Bianchi e Silva ◽  
Elaine Bauer Veeck ◽  
José Pedro Peixoto de Oliveira ◽  
Paulo Henrique Couto Souza
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chemical Composition ◽  
Chemical Components ◽  
Resin Composites ◽  
X Ray ◽  
Scanning Electron

OBJECTIVES: the purpose of this study was to compare the chemical composition of four different shades (incisal/extra-light, A2, A3 and B3) of two packable resin composites (SOLITAIRE®, and PRODIGY CONDENSABLE TM). METHODS AND MATERIALS: the specimens measured 4mm in diameter and 4mm in thickness. Five specimens were made for each shade of the materials. They were light cured for 40 seconds at a power of 600mW/cm². Subsequently, the specimens were removed from the plates and ground to powder and then pressed into holes measuring 4mm in diameter in a Teflon matrix, using the plates of the same material as base and cover. Specimens were evaluated under SEM with an x-ray detector for the spectroscopic test by energy dispersing. RESULTS: the chemical components found in both materials were practically the same, but in different proportions. Carbon, Oxygen, Aluminum, Silica, Fluoride and Barium were found. CONCLUSIONS: the chemical composition of each same material varied according to each shade analyzed.

scholarly journals Joining of γ-TiAl Alloy to Ni-Based Superalloy Using Ag-Cu Sputtered Coated Ti Brazing Filler Foil

Metals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 723 ◽  
Author(s):  
Sónia Simões ◽  
Carlos Tavares ◽  
Aníbal Guedes
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Scanning Electron Microscopy ◽  
Chemical Composition ◽  
Tial Alloy ◽  
Energy Dispersive ◽  
X Ray ◽  
Base Materials ◽  
Intermetallic Particles ◽  
Scanning Electron

Joining γ-TiAl alloy to Ni-based superalloy Hastelloy using Ag-Cu sputtered coated Ti foil as brazing filler was investigated in this study. Brazing experiments were performed at 900, 950, and 980 °C with a dwelling stage of 10 min in vacuum. The microstructure and the chemical composition of the resulting interfaces were analyzed by scanning electron microscopy (SEM) and by energy dispersive X-ray spectroscopy (EDS), respectively. Sound joints were produced after brazing at 980 °C, presenting a multilayered interface, consisting mainly of Ti-Al and Ti-Ni-Al intermetallics close to the γ-TiAl alloy, and of Ti-rich, Ti-Ni, and Cr-Ni-Mo rich phases near Hastelloy. The hardness of the interface, ranging from around 300 to 1100 HV0.01, is higher than both base materials, but no segregation of either Ag solid solution or coarse intermetallic particles was observed. Therefore, the developed brazing filler also avoids the need to perform post-brazing heat treatments that aim to eliminate detrimental extensive segregation of either soft phases or of hard and brittle compounds.

scholarly journals Relationship Between the Surface Chemical Composition of Implants and Contact With the Substrate

2015 ◽  
Vol 41 (1) ◽  
pp. 17-21 ◽  
Author(s):  
Mariana Lima da Costa Valente ◽  
Antonio Carlos Shimano ◽  
Elcio Marcantonio Junior ◽  
Andréa Candido dos Reis
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chemical Composition ◽  
Surface Characterization ◽  
Structural Changes ◽  
Testing Machine ◽  
Energy Dispersive ◽  
Machined Surface ◽  
X Ray ◽  
Scanning Electron

The purpose of the study was to use scanning electron microscopy and energy dispersive x-ray spectrometry to assess possible morphologic and chemical changes after performing double-insertion and pullout tests of implants of different shapes and surface treatments. Four different types of implants were used—cylindrical machined-surface implants, cylindrical double-surface–treated porous implants, cylindrical surface-treated porous implants, and tapered surface-treated porous implants—representing a total of 32 screws. The implants were inserted into synthetic bone femurs, totaling 8 samples, before performing each insertion with standardized torque. After each pullout the implants were analyzed by scanning electron microscopy and energy dispersive x-ray spectrometry using a universal testing machine and magnified 35 times. No structural changes were detected on morphological surface characterization, only substrate accumulation. As for composition, there were concentration differences in the titanium, oxygen, and carbon elements. Implants with surface acid treatment undergo greater superficial changes in chemical composition than machined implants, that is, the greater the contact area of the implant with the substrate, the greater the oxide layer change. In addition, prior manipulation can alter the chemical composition of implants, typically to a greater degree in surface-treated implants.

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