Formation of ultrafine nanoporous gold related to surface diffusion of gold adatoms during dealloying of Al2Au in an alkaline solution

2010 ◽  
Vol 62 (3) ◽  
pp. 137-140 ◽  
Author(s):  
Zhonghua Zhang ◽  
Yan Wang ◽  
Yingzi Wang ◽  
Xiaoguang Wang ◽  
Zhen Qi ◽  
...  
Keyword(s):  
Surface Diffusion ◽  
Alkaline Solution ◽  
Nanoporous Gold ◽  
Gold Adatoms

Formation of Nanoporous Gold by Chemical Dealloying of an AlAu Intermetallic Compound

2011 ◽  
Vol 236-238 ◽  
pp. 2092-2096
Author(s):  
Ji Kui Lin ◽  
Zhong Hua Zhang
Keyword(s):  
Intermetallic Compound ◽  
Surface Diffusion ◽  
Nanoporous Gold ◽  
Uniform Structure ◽  
Length Scales

Here, we report the synthesis of nanoporous gold (NPG) with a uniform structure by chemical dealloying of an AlAu intermetallic compound under free corrosion conditions. The length scales of ligaments/channels in NPG can be tuned by changing the dealloying solution. We verify that Cl-can accelerate the surface diffusion of Au atoms and induce the coarsening of ligaments/channels in NPG. In addition, a metastable intermediate Al2Au5phase appears during the dealloying of AlAu.

A theory of contamination in electron microscopes by surface diffusion

1978 ◽  
Vol 36 (1) ◽  
pp. 116-117
Author(s):  
J.T. Fourie
Keyword(s):  
Electron Beam ◽  
Surface Diffusion ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Physical Parameters ◽  
Carbon Compounds ◽  
Hydrocarbon Molecules ◽  
Electron Microscopes ◽  
Primary Electrons ◽  
Long Chain

Contamination in electron microscopes can be a serious problem in STEM or in situations where a number of high resolution micrographs are required of the same area in TEM. In modern instruments the environment around the specimen can be made free of the hydrocarbon molecules, which are responsible for contamination, by means of either ultra-high vacuum or cryo-pumping techniques. However, these techniques are not effective against hydrocarbon molecules adsorbed on the specimen surface before or during its introduction into the microscope. The present paper is concerned with a theory of how certain physical parameters can influence the surface diffusion of these adsorbed molecules into the electron beam where they are deposited in the form of long chain carbon compounds by interaction with the primary electrons.

Blue Sapphire with Partial Red Surface Diffusion

2020 ◽  
Vol 37 (1) ◽  
pp. 23-24
Author(s):  
Bear Williams ◽  
Cara Williams ◽  
Charles I. Carmona
Keyword(s):  
Surface Diffusion

The Effect of Dry Mix Sodium Hydroxide onto Workability and Compressive Strength of Geopolymer Paste

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
A. Z. Mohd Ali ◽  
◽  
N. A. Jalaluddin ◽  
N. Zulkiflee ◽  
◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Alkaline Solution ◽  
High Emission ◽  
New Material ◽  
Curing Regime ◽  
Solid Form ◽  
Geopolymer Paste

The production of ordinary Portland cement (OPC) consumes considerable amount of natural resources, energy and at the same time contribute in high emission of CO2 to the atmosphere. A new material replacing cement as binder called geopolymer is alkali-activated concrete which are made from fly ash, sodium silicate and sodium hydroxide (NaOH). The alkaline solution mixed with fly ash producing alternative binder to OPC binder in concrete named geopolymer paste. In the process, NaOH was fully dissolved in water and cooled to room temperature. This study aims to eliminate this process by using NaOH in solid form together with fly ash before sodium silicate liquid and water poured into the mixture. The amount of NaOH solids were based on 10M concentration. The workability test is in accordance to ASTM C230. Fifty cubic mm of the geopolymer paste were prepared which consists of fly ash to alkaline solution ratio of 1: 0.5 and the curing regime of 80℃ for 24 hours with 100% humidity were implemented. From laboratory test, the workability of dry method geopolymer paste were decreased. The compressive strength of the dry mix of NaOH showed 55% and the workability has dropped to 58.4%, it showed strength reduction compared to the wet mix method.

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