scholarly journals Diffusion of Sulfuric Acid in Concentrated Solutions

1993 ◽  
Vol 140 (8) ◽  
pp. 2217-2221 ◽  
Author(s):  
Shigeru Umino ◽  
John Newman
Keyword(s):  
Sulfuric Acid ◽  
Concentrated Solutions

scholarly journals Study of Cellulose Interaction with Concentrated Solutions of Sulfuric Acid

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Michael Ioelovich
Keyword(s):  
Sulfuric Acid ◽  
High Power ◽  
Room Temperature ◽  
Regenerated Cellulose ◽  
Structure And Properties ◽  
Optimal Conditions ◽  
Initial Sample ◽  
Concentrated Solutions ◽  
Crystallinity Degree ◽  
20 Nm

The effect of the concentration of sulfuric acid (SA) and temperature on structure and properties of cellulose (MCC) had been studied. Investigations showed that solubility of the initial sample at the room temperature increased gradually in the range of the acid concentration from 50 to 60 wt.% SA. When SA concentration reached 65 wt.%, then MCC sample dissolved completely. Cellulose regenerated from 65 wt.% SA had an amorphized structure and was characterized by high enzymatic digestibility. At increased temperature, 45°C, solubility of MCC in SA was raised, while yield and DP decreased. After treatment of MCC with hot 50–60 wt.% SA, the crystallinity degree of the obtained cellulose samples changed slightly, and these samples retained mainly the CI crystalline polymorph. However, when SA concentration reached 65 wt.%, then regenerated cellulose had CII crystalline polymorph, reduced crystallinity degree, and low DP. Using optimal conditions of the acidic treatment (57–60 wt.% SA, T = 45°C; t=1 h) in combination with the high-power disintegration permitted obtaining the CI nanocrystalline cellulose particles (NCP) having sizes 150–200 × 10–20 nm with the heightened yield (65–70%). These NCP can be used, for example, as reinforcing nanofillers for various composites.

Resolution of Raman spectra of aqueous sulfuric acid mixtures using principal factor analysis

1981 ◽  
Vol 59 (17) ◽  
pp. 2591-2598 ◽  
Author(s):  
Robin A. Cox ◽  
Ülo L. Haldna ◽  
K. Loralee Idler ◽  
Keith Yates
Keyword(s):  
Factor Analysis ◽  
Sulfuric Acid ◽  
Raman Spectra ◽  
Ion Pair ◽  
Medium Composition ◽  
Principal Factor ◽  
Water Molecules ◽  
Concentrated Solutions ◽  
Principal Factor Analysis ◽  
Hydrated Ion

Principal factor analysis has been applied to Raman spectra of 26 sulfuric acid/water mixtures covering the 0–100% H2SO4 concentration range. The analysis greatly facilitates the identification of peaks due to different species. The results show that SO42− ions and "free" HSO4− ions do not co-exist with undissociated H2SO4 molecules in solution and that two water molecules rather than one are required for the first ionization of H2SO4. A species with the composition H2SO4•2H2O, assigned a hydrated ion pair structure, reaches maximum concentration at the same medium composition at which SO42−, free HSO4−, and H2SO4 are at concentration minima, about 75% w/w. The only species apparent in the more concentrated solutions are the ion pair and undissociated H2SO4, which could be taken to mean that H2SO4 is a weaker acid than H3O+, but a stronger one than H3O+•H2O (or H5O2+, if this entity has a real existence). Separate peaks due to the postulated H3O+•H2SO4 (or H5SO5+) were not observed.

Preparation of Thin Cadmium Telluride Samples for Electron Microscope Studies

1974 ◽  
Vol 32 ◽  
pp. 548-549
Author(s):  
T. J. Magee ◽  
J. Peng ◽  
J. Bean
Keyword(s):  
Electron Microscope ◽  
Sulfuric Acid ◽  
Solid State ◽  
Sample Preparation ◽  
Cadmium Telluride ◽  
Potassium Dichromate ◽  
Optical Components ◽  
The Past ◽  
Solid State Devices

Cadmium telluride has become increasingly important in a number of technological applications, particularly in the area of laser-optical components and solid state devices, Microstructural characterizations of the material have in the past been somewhat limited because of the lack of suitable sample preparation and thinning techniques. Utilizing a modified jet thinning apparatus and a potassium dichromate-sulfuric acid thinning solution, a procedure has now been developed for obtaining thin contamination-free samples for TEM examination.

Physical, Chemical, and Crystallographic Characterization of Anodic Coatings on High Strength Aluminum Base Alloys

1976 ◽  
Vol 34 ◽  
pp. 636-637
Author(s):  
R. E. Herfert ◽  
N. T. McDevitt
Keyword(s):  
Sulfuric Acid ◽  
Salt Spray ◽  
High Strength ◽  
Environmental Stability ◽  
Anodic Films ◽  
Sodium Dichromate ◽  
Corrosion Resistant ◽  
Aerospace Applications ◽  
Bond Strengths ◽  
Adhesive Bonded Joints

Durability of adhesive bonded joints in moisture and salt spray environments is essential to USAF aircraft. Structural bonding technology for aerospace applications has depended for many years on the preparation of aluminum surfaces by a sulfuric acid/sodium dichromate (FPL etch) treatment. Recently, specific thin film anodizing techniques, phosphoric acid, and chromic acid anodizing have been developed which not only provide good initial bond strengths but vastly improved environmental durability. These thin anodic films are in contrast to the commonly used thick anodic films such as the sulfuric acid or "hard" sulfuric acid anodic films which are highly corrosion resistant in themselves, but which do not provide good initial bond strengths, particularly in low temperature peel.The objective of this study was to determine the characteristics of anodic films on aluminum alloys that make them corrosion resistant. The chemical composition, physical morphology and structure, and mechanical properties of the thin oxide films were to be defined and correlated with the environmental stability of these surfaces in humidity and salt spray. It is anticipated that anodic film characteristics and corrosion resistance will vary with the anodizing processing conditions.

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