Sizing Sodium etching

The so called porous silica is made by the acid etching of annealed sodium borosilicate glass. The bulk structure is glass mainly of silica and has a uniform pore size distribution in the mesopore region. These are used as a source of silica glass. 

The treatment generally begins with mechanical polishing with decreasing sizes of alumina (or equivalent). Then an etch with a mixture of ammonia and hydrogen peroxide or with a solution of sodium cyanide and hydrogen peroxide may be carried out. After a further wash with water, the electrode is immersed in the electrolyte solution, sometimes under cathodic potential control (-0.6 to -0.2 SCE). All the electric potentials in this review are referenced with respect to the standard calomel electrode (SCE), unless stated otherwise. 

A widely applied method for surface stmcturing is chemical etching. For example, Yeo et al. investigated whether the pretreatment of PCL 20% tricalcium phosphate (TCP) composites under alkaline conditions can be utilized to beneficially alter surface properties in order to enhance early bone formation. In doing so, PCL-TCP scaffolds were treated with 3M sodium hydroxide for 48 and 96 h, respectively. Both groups showed an increased surface roughness compared to unmodified controls however, the scaffold pore size and rod thickness remained unchanged. After implantation in the calvarias of... 

Samples of 0.030 in 2024 T3 bare aluminum were pre-cut, to suitable size for mounting in the spectrometer, with a tab to facilitate handling. The metal was subjected to 10 minute etch at 62-63 C in a sodium dichromate-sulfuric acid solution (per Section One, Handbook of Adhesives, Bloomingdale Aerospace Products, Havre de Grace, Maryland 21078), rinsed ten minutes in running, deionized water, and dried one hour at 63 C. One sample was then additionally subjected to the phosphoric acid anodization as outlined in BAG 5555. ... 

For applications involving filtration or dialysis, polyimide probes with integrated nanoporous filtration areas feature a membrane with submicron-sized pores [64]. The pores are created by irradiation with uranium or xenon ions to create ion tracks. These tracks are chemically etched in sodium hypochlorite and chlorine to produce a porous membrane. 

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