PowerPoint PresentationWhat are the naked facts?
PADUA UNIVERSITY
Science Faculty
Enzo Palmieri XIV _ SRF
Enzo Palmieri XIV _ SRF
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Enzo Palmieri XIV _ SRF
(ratio 18 : 21 : 61)
Enzo Palmieri XIV _ SRF
refineries using Hydrofluoric acid
• Contact with HF does not cause immediate pain, so systemic
poisoning begins before the person is aware
• Because its action can be delayed for many hours, it can distribute
throughout the body, causing the erosion of bone.
• F- ions bind to Ca++ and Mg++ ions to form insoluble salts
• (CaF2 and MgF2 salts form some natural gemstones).
• In the body, Ca and Mg ions are used to mediate a variety of
physiological processes, such as muscle movement.
• Cardiac arrests have been reported from concentrated acid burns
to as little as 2.5% of exposed body surface area
Enzo Palmieri XIV _ SRF
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Japanese Patent office Publication number 60092500 A - Date of filing 26.10.83
Applicant Mitsubishi heavy Ind LTD., Nomura Tokin: KK
Inventor : Yoshisuke Keisuke; Nomura Hirotoshi
See also: K. Saito, Proceedings of the 4th workshop on RFSC, Tsukuba 1989
1. Alternatives to HF:
fluosulfuric acid
2. Alternatives to HF:
Note: Some authors claim that ethyl-perchlorate is as dangerous as Nitroglycerin
An EP mixture
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Mg(ClO4)2 0.05 mole/lt in CH3OH EP Voltage = 50-70 V, Temperature = -5°C
Is it less dangerous?
3. Alternatives to HF: by Schober and Sorajic, extrapolating what
proposed by Epelboin [Rev. Met. 49 (1952) 863.]
Perchlorate salts:
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4. Alternatives to HF: by O. Piotrowski, C. Madore. Landolt, Electrochinica acta 44,2289 (1999)
Zhao Xin, Virginia Polytechnic Instytute, PhD Thesis (2009)
Sulphuric acid
in Methanol
HARMFUL IF INHALED OR ABSORBED THROUGH SKIN
AFFECTS CENTRAL NERVOUS SYSTEM AND LIVER
Enzo Palmieri XIV _ SRF
liver damage to reproductive harm, blindess or death
Methanol is very flammable. The pure liquid catches fire easily
and aqueous solutions containing a significant amount of
methanol can also catch fire
The flame above burning methanol is virtually invisible, so it is
not always easy to tell whether a methanol flame is still alight
The explosion limits for methanol are unusually wide.
Enzo Palmieri XIV _ SRF
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5. Alternatives to HF: V. Palmieri, V. Brichese, V. Rampazzo, S. Stivanello,
Nb Electrodissolution in Solution1: KOH 1 M
T ~ 70° Stirring E = 1,38 V Etching rate: 132 g/m2min
Enzo Palmieri XIV _ SRF
possible in molten salts
Anhydrous AlCl3 can give rise to unpleasent exothermic reactions!
Enzo Palmieri XIV _ SRF
• having a melting point less than 100 °C
• which solely consist of cations and anions
Enzo Palmieri XIV _ SRF
during times of rapid development. It is especially effective at
doing so in poultry, and so it is a common poultry feed additive.
Choline is particularly important for fetal development and for
babies / children. Human milk contains high amounts of choline
Choline is important for cell membrane structure, for
synthesizing folic acid and vitamin B12, and for protecting the
liver from accumulating fat. Take choline chloride supplements
to protect the liver from damage, to lower cholesterol, to improve
memory, to preserve prostate and to enhance mood! ….
…. and to electropolish Niobium
Enzo Palmieri XIV _ SRF
Molar Mass 139.62 g mol−1
Appearance White or deliquescent crystals
Molecular Formula 302 °C (decomposes)
Solubility in water very soluble
Choline chloride is a quaternary ammonium salt. It
has a Choline cation with Chloride anion.
With Urea it forms a deep eutectic solvent
Enzo Palmieri XIV _ SRF
Choline (2-hydroxyethyl-trimethylammonium) Chloride
is a quaternary ammonium salt also known as Vitamin B4
Enzo Palmieri XIV _ SRF
One simple hydrogen bond 'donor' that can been used is
urea ((NH2)2C=O), which is a common fertiliser
Urea mixed with choline chloride in a 2:1 ratio produces a
colourless liquid that freezes at ca 12°C, which is
remarkable, given the melting points of the constituents
The lowest melting point of these mixtures occurs when
the ratio of salt to hydrogen bond donor is 1:2.
The depression of freezing point and the eutectic
composition changes with the nature of the molecule
providing the hydrogen bonds, eg oxalic acid
(HOOCCOOH): choline chloride has a eutectic
composition of 1:1 and a freezing point depression of
212°C
1/1; 2/1; 3/1; 4/1
- Added NH4Cl Concentration
Enzo Palmieri XIV _ SRF
Sample 52 05A/cm2
As a conseauence increase both
voltage and Temperature
bubbles forming on the surface
If it is too strong, will damage the
viscous layer
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Aging of the solution A quantity of dissolved Niobium is mandatory for good EP
Fresh
Aged
EP HF-H2SO4 132,7 189,7
1
Enzo Palmieri XIV _ SRF
Magic Component
The NH2 group it has good solubility in Urea’s melts
Enzo Palmieri XIV _ SRF
solution gets big heat.
The best recipe found
Magic Component, g/l 30
characteristic of electropolishing
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Surface quality as a function of quantity Nb-ions in the melt
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Surface quality as a function of quantity Nb-ions in the melt
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Dissolving speed 6,2 um/min
(in our laboratory on cavities in classical EP we have 0,5 um/min)
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Horizontal EP didn’t give good results,
because of the very fast temperature
rising: after 1 minute temperature inside
the cavity was more than 190C, which
brought to degradation of electrolyte.
Only Cutoff tubes appeared satisfactory
has enough good view.
Enzo Palmieri XIV _ SRF
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With vertical EP there are also difficulties, but avoidable. High activity formation of cathode gas brings to saturation of electrolyte with H2 (like the most probable cathode reaction in electrolyte which includes –OH and –NH2 groups)
The Molecules of H2 can oxidize on anode on the viscous film surface. Time between babbles adsorption and reduction there is no electrical field on anode surface which is passiving during this time.
Enzo Palmieri XIV _ SRF