scholarly journals Effect of Stabilizer on Gold Leaching with Thiourea in Alkaline Solutions

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Wenjuan Li ◽  
He Shang ◽  
He Zhou ◽  
Yongsheng Song ◽  
Shuilin Zheng ◽  
...  
Keyword(s):  
Activation Energy ◽  
Sodium Silicate ◽  
Cyclic Voltammetry Curve ◽  
Sodium Sulfite ◽  
Alkaline Solutions ◽  
Gold Leaching ◽  
Force Microscopy ◽  
Atomic Force ◽  
Alkaline Thiourea ◽  
The Stability

The present work investigated the comparison of the effects of Na2SO3 and Na2SiO3 on thiourea stabilization, and a systematic study was undertaken to establish the effects of these stabilizers on the stability of alkaline thiourea, both qualitatively and quantitatively. The effects of these stabilizers on the activation energy of alkaline thiourea gold leaching was also studied. The results showed that sodium silicate was more suitable as a stabilizer in this system than sodium sulfite because the peak current of gold dissolution with sodium sulfite was higher than that with sodium silicate, but the inhibition of thiourea decomposition by the former was less obvious than that of sodium silicate in the cyclic voltammetry curve. The quartz crystal microbalance results showed that the quality decreased to about 100 ng cm2 in the presence of a stabilizer, while it increased to 300 ng cm2 in the absence of the stabilizer. It is inferred that gold can be dissolved by alkaline thiourea in the presence of a stabilizer, while it cannot without a stabilizer because of the decomposition of thiourea. This assumption was confirmed by atomic force microscopy measurements. The surface activation energy of Au dissolution decreased from 183.76 to 98.07 kJ/moL with the addition of sodium silicate, indicating that Au dissolution was promoted with the chemical.

scholarly journals Thermal Activation of Crystalline Silicon Ions in Alkaline Solution

1970 ◽  
Vol 7 (7) ◽  
pp. 15-18
Author(s):  
Shobha Kanta Lamichhane
Keyword(s):  
Activation Energy ◽  
Etch Rate ◽  
Thermal Activation ◽  
Crystalline Silicon ◽  
Micro Electro Mechanical System ◽  
Alkaline Solutions ◽  
Force Microscopy ◽  
Microstructure Fabrication ◽  
Atomic Force ◽  
Key Techniques

Anisotropic wet chemical etching of silicon in alkaline solutions (KOH) is one of the key techniques for the manufacture of microstructure. Fabrication of Micro-electro mechanical system (MEMS) part demand smooth surface finish and angular dependent etch rate. The absolute values of orientation dependent etch rate is found to vary with thermal agitation. In this work, experimental results of etch rate is found with their unusual values of activation energy along different planes. The various sites that an atom can occupy are not equivalent of their energy; some are more favorable to removal than others. In this paper attention is being given to demonstrate thermal activation is the prime factor that influences the behavior of etching mechanism as well as surface morphology. Atomic force microscopy (AFM) has been employed to analyze the morphology of the etched silicon surface at relevant elevated temperature. A systematic variation in morphological growth leads to stabilized surface structure under the influence of associated activation energy. Keywords: Activation energy; Etching; Anisotropy; Etch rate; MEMS; LPCVD; SOI. DOI: 10.3126/sw.v7i7.3817 Scientific World Vol.7(7) 2009 pp.15-18

Growth of 4H-SiC Single Crystals on 6H-SiC Seeds with an Open Backside by PVT Method

2009 ◽  
Vol 615-617 ◽  
pp. 15-18 ◽  
Author(s):  
Emil Tymicki ◽  
Krzysztof Grasza ◽  
Katarzyna Racka ◽  
Marcin Raczkiewicz ◽  
Tadeusz Łukasiewicz ◽  
...  
Keyword(s):  
Single Crystals ◽  
Electron Backscatter Diffraction ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Optical Scanning ◽  
Atomic Force ◽  
The Stability ◽  
Backscatter Diffraction ◽  
Source Materials

4H-SiC single crystals grown by the seeded physical vapour transport method have been investigated. These crystals were grown on 6H-SiC seeds. The influence of the seed temperature, form and granulation of SiC source materials on the stability and efficiency of the 4H polytype growth have been investigated. A new way of the seed mounting - with an open backside - has been used. Crystals obtained were free of structural defects in the form of hexagonal voids. The crystalline structure of SiC crystals was investigated by EBSD (Electron Backscatter Diffraction) and X-Ray diffraction methods. Moreover, defects in crystals and wafers cut from these crystals were examined by optical, scanning electron and atomic force microscopy combined with KOH etching.

In Situ and Real-Time Atomic Force Microscopy Studies of the Stability of Oligothiophene Langmuir–Blodgett Monolayers in Liquid

2014 ◽  
Vol 118 (11) ◽  
pp. 5789-5795 ◽  
Author(s):  
Nai-Ning Yin ◽  
Alexander Buyanin ◽  
Shawn L. Riechers ◽  
Olivia P. Lee ◽  
Jean M. J. Fréchet ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Real Time ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Atomic Force ◽  
The Stability

Ta2O5-Incorporated WO3 Nanocomposite Film for Improved Electrochromic Performance in an Acidic Condition

2006 ◽  
Vol 6 (11) ◽  
pp. 3572-3576 ◽  
Author(s):  
Hee-Sang Shim ◽  
Hyo-Jin Ahn ◽  
Youn-Su Kim ◽  
Yung-Eun Sung ◽  
Won Bae Kim
Keyword(s):  
Surface Roughness ◽  
Photoelectron Spectroscopy ◽  
Potential Cycling ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Continuous Potential ◽  
Chemical States ◽  
The Stability

We report electrochromic and electrochemical properties of a WO3-Ta2O5 nanocomposite electrode that was fabricated from co-sputtering. Transmission electron microscopy (TEM)images of the WO3-Ta2O5 nanocomposite electrode revealed that morphology of the WO3 film was changed by incorporation of Ta2O5 nanoparticles, and their chemical states were confirmed to be W6+ and Ta5+ oxides from X-ray photoelectron spectroscopy (XPS). The introduction of Ta2O5 to the WO3 film played a role in alleviating surface roughness increase during continuous potential cycling; whereas the surface roughness of the WO3 film was increased from ca. 3.0 nm to ca. 13.4 nm after 400 cycles, the roughness increase on the WO3-Ta2O5 was significantly reduced to 4.2 nm after 400 cycles, as investigated by atomic force microscopy (AFM). This improvement of the stability by adding Ta2O5 may be responsible for the enhanced electrochemical and optical properties over long-term cycling with the WO3-Ta2O5 nanocomposite electrode.

Uniform Ultimate Boundedness of Probe-to-Probe Dynamics in Dual Probe Atomic Force Microscopy

2014 ◽  
Author(s):  
Ayad Al-Ogaidi ◽  
Douglas Bristow
Keyword(s):  
Switched Systems ◽  
Ultimate Boundedness ◽  
Contact Mode ◽  
Force Microscopy ◽  
Simultaneous Imaging ◽  
Atomic Force ◽  
State Dependent ◽  
Uniform Ultimate Boundedness ◽  
The Stability ◽  
Dual Probe

Atomic force microscopes use a probe to interface with matter at the nanoscale through a variety of imaging or manipulation methods. A dual-probe atomic force microscope (DP-AFM) has been proposed for simultaneous imaging and manipulation. One challenge of DP-AFM is probe-to-probe contact, which may occur intentionally such as when locating one probe with the other. This work studies the stability for such interactions where the 1st probe is in the tapping mode (typically used for imaging) and 2nd probe is in the contact mode (typically used for manipulation). A state dependent switched model is proposed for DP-AFM. A theorem is proposed for uniformly ultimately bounded (UUB) stability of switched systems under a sequence nonincreasing condition and applied to the DP-AFM problem.

scholarly journals Thermal Induced Microstructures of KOH Etched Silicon Surface

1970 ◽  
Vol 5 (1) ◽  
pp. 62-70 ◽  
Author(s):  
Shobha Kanta Lamichhane
Keyword(s):  
Activation Energy ◽  
Silicon Surface ◽  
Etch Rate ◽  
Low Voltage ◽  
Micro Electro Mechanical System ◽  
Contact Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Engineering And Technology ◽  
Etched Silicon

Anisotropic KOH etching of silicon for the fabrication of Micro-electro mechanical system (MEMS) part is based on surface finish and angular dependence of etch rate, creating thin diaphragm. The absolute values of orientation dependent etch rate is found to vary with thermal agitation. In this work, experimental results of etch rate is found quite consistent with simulated and are justify with their unusual values of activation energy along different planes. The various sites that an atom can occupy are not equivalent of their energy; some are more favorable to removal than others. In this paper attention is given to demonstrate thermal activation energy is the prime parameter that influences the behavior of etching mechanism as well as AFM surface morphology. Low-voltage contact mode atomic force microscopy (AFM) has been employed to analyze the morphology of the etched silicon surface at relevant different temperature. A systematic variation in morphological growth leads to stabilized surface structure under the influence of associated activation energy is concluded. Key words: Etching; Anisotropy; Etch rate; diaphragm; MEMS; LPCVD; SOI; AFM DOI: 10.3126/kuset.v5i1.2847 Kathmandu University Journal of Science, Engineering and Technology Vol.5, No.1, January 2009, pp 62-70

scholarly journals The Influence of the Preparation and Stability of Nanofluids for Heat Transfer

2019 ◽  
Vol 25 (4) ◽  
pp. 45-54 ◽  
Author(s):  
Noor Sabih Majeed ◽  
Basma A. Abdulmajeed ◽  
Anwar Khudhur Yaseen
Keyword(s):  
Heat Transfer ◽  
Electron Microscopy ◽  
Base Fluid ◽  
X Ray Diffraction ◽  
Step Method ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Stability ◽  
Scanning Electron

Recently the use of nanofluids represents very important materials. They are used in different branches like medicine, engineering, power, heat transfer, etc. The stability of nanofluids is an important factor to improve the performance of nanofluids with good results. In this research two types of nanoparticles, TiO2 (titanium oxide) and γ-Al2O3 (gamma aluminum oxide) were used with base fluid water. Two-step method were used to prepare the nanofluids. One concentration 0.003 vol. %, the nanoparticles were examined. Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray diffraction (XRD) were used to accomplish these tests. The stability of the two types of nanofluids is measured by zeta potential and UV-vis spectrophotometer. The results showed that γ-Al2O3/water has more stable than TiO2/ water for the same period of time.  

Synergistic effect of polyvinylpyrrolidone noncovalently modified graphene and epoxy resin in anticorrosion application

2020 ◽  
pp. 095400832094229
Author(s):  
Shifeng Wen ◽  
Jiacheng Ma
Keyword(s):  
Epoxy Resin ◽  
Photoelectron Spectroscopy ◽  
Electrochemical Impedance ◽  
Covalent Modification ◽  
Original Structure ◽  
Graphene Layers ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Stability ◽  
Modified Graphene

In this article, polyvinylpyrrolidone (PVP) was used for the noncovalent modification on the surface of graphene. Compared with covalent modification, this method maintained the original structure of graphene layers, thereby maximizing the original properties of graphene. The π–π noncovalent bond was formed between PVP and graphene by X-ray photoelectron spectroscopy analysis, indicating that PVP successfully modified graphene. The thickness of graphene layer was measured by atomic force microscopy, which showed that the distance between graphene layers was increased by 5–6 nm, and the stability of the modified graphene in N, N-dimethylformamide was remarkably improved. The obtained composite coating by combination of the modified graphene and the epoxy resin was subjected to electrochemical impedance test to obtain the best anticorrosive effect of the coating with the graphene content of 0.3 wt%. The results showed that the addition of graphene to the epoxy resin could effectively improve the anticorrosive effect. Meanwhile, the good electrical conductivity allowed the electrons which lost from the substrate to led to air or saline rapidly, thereby reducing the combination of iron ions with oxygen and the generation of corrosion products (iron oxides).

Electroplated CuO Thin Films from High Alkaline Solutions

2011 ◽  
Vol 15 (1) ◽  
pp. 49-55
Author(s):  
V. Dhanasekaran ◽  
T. Mahalingam ◽  
S. Rajendran ◽  
Jin Koo Rhee ◽  
D. Eapen
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Film Thickness ◽  
Structural Characteristics ◽  
Band Gap Energy ◽  
Alkaline Solutions ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Microstructural Parameters ◽  
Atomic Force

CuO thin films were coated on ITO substrates by an electrodeposition route through potentiostatic mode. The electrodeposited CuO thin films were characterized and the role of copper sulphate concentration on the structural, morphological and optical properties of the CuO films was studied. Film thickness was measured by a stylus profilometer and found to be in the range between 800 and 1400 nm. The structural characteristics studies were carried out using X-ray diffraction and found that the films are polycrystalline in nature with a cubic structure. The preferential orientation of CuO thin films is found to be along (111) plane. The estimated microstructural parameters revealed that the crystallite size increases whereas the number of crystallites per unit area decreases with increasing film thickness. SEM studies show that the grain sizes of CuO thin films vary between 100 and 150 nm and also morphologies revealed that the electrodeposited CuO exhibits uniformity in size and shape. The surface roughness is estimated 15 nm of the CuO film were studied by atomic force microscopy. Optical properties of the films were analyzed from absorption and transmittance studies. The optical band gap energy was determined to be 1.5 eV from absorption coefficient. The variation of refractive index (n), extinction coefficient (k), with wavelength was studied and the results are discussed.

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