Stability of silver and Pyrex in perchloric acid-silver perchlorate solutions and in conductivity water

Craig, D. Norman; Law, Catherine A.; Hamer, Walter J.

doi:10.6028/jres.064a.011

Cited by 6 publications

(10 citation statements)

References 2 publications

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“…Another possible cause of too little delivery of silver into solution might be less than perfect efficiency of the electrode in generating silver at the anode. Electrode efficiency to the required precision cannot be directly measured (the most precise measuremen ts have established the reversibility of the silver coulometer to only 60 ppm [4]). Indirec tly we can seek co rrelations of EA g with the current or the maximum overvoltage of the anode during dissolution.…”

Section: Discussionmentioning

confidence: 99%

“…The silver perchlorate is present in the solution to reduce to insignificant proportions the already meager spontaneous dissolution of silver into perchloric acid. The work establishing these desirable conditions was done at the National Bureau of Standards (NBS), by Craig et al [4] in preparation for his determination [5] of the Faraday.…”

Section: Chemical Principlesmentioning

confidence: 99%

“…In the experiments of Craig [4] this finely divided material was recovered, filtered and weighed. It was counted as part of the final weight of the anode.…”

Section: Apparatusmentioning

confidence: 99%

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The electrochemical equivalent of pure silver - a value of the Faraday

Bower

Davis

1980

J. RES. NATL. BUR. STAN.

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Oxygen-free high-pu rity samples were used in a precise deter mina tion of the electrochemi cal equival ent of silver . A comprehensive mass spec trometric analysis for impurities was performed . Our value agrees well wi th prior meas urements of the same qua ntity at th e Na ti onal Bureau of Sta ndards (NBS) by Craig and coworke rs_ We find the elec troc hemi cal equivalent of pure silver to be 1.1179648 mg C-')8S' Attached to this figur e is an unce rtainty whose random co mponent (standa rd deviation of th e mean of 8 deter minati ons) is 9.5 X 10-7 mg Co, (0.85 ppm). Th e roo t-sum-squ are of systema tic uncertainties of known origin is 1.07 X 10-6 mg Co, (0.96 ppm). The above value for the elec trochemical equival ent of silver'leads us to cal culate th e Faraday to be: F = 96486.33 (24) AN B s . s . mol-' (2.5 ppm).

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Section: Discussionmentioning

confidence: 99%

Section: Chemical Principlesmentioning

confidence: 99%

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The electrochemical equivalent of pure silver - a value of the Faraday

Bower

Davis

1980

J. RES. NATL. BUR. STAN.

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“…The second set of samples was prepared by deposition of the paste into wire shaped gaps with approximate dimensions of 1 mm by 1 mm cross-section and 3 mm length for the first sample and approximately 150 µm by 150 µm cross section and 4 mm length for the remaining samples of this set. The first sample was stored at 300 °C in air and the The fourth set of samples were prepared by sintering of the NanoTach® X paste inside glass sample holders, which were designed for surface cleaning of the samples by perchloric acid (effective for removing organic contamination on silver without causing damage from the utilised concentration [22,23]) before high temperature storage. After manual deposition of paste into the holder and sintering, the samples were stored for 30 minutes inside an aqueous solution containing 20% concentration of perchloric acid and then stored in deionised water before placement into the furnace for high temperature storage at 300 °C inside ~40 mPa vacuum for 5 h.…”

Section: Methodsmentioning

confidence: 99%

Microstructural evolution of sintered silver at elevated temperatures

Paknejad

Mansourian

Greenberg

et al. 2016

Microelectronics Reliability

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Reduction in the sintering temperature of metal powders by lowering particle size into the nanoparticle range has resulted in a new class of porous sintered joining materials.Especially promising are sintered silver based materials which can be used to form bonds between wide-bandgap semiconductor die and circuit boards for use in high temperature applications. This work shows that for these materials the exterior sintered silver surface oxidizes preventing surface morphology changes, while the interior pore surfaces of the porous silver remain largely oxide-free. These pore surfaces facilitate fast atomic movement resulting in grain growth and changes in the internal microstructure.Morphology changes in the temperature range 200-400 °C are presented both as statistical averages of grain size and, uniquely in this type of study, by tracking individual pores and grains. It is shown that the internal structure will undergo changes during high temperature storage in contrast to the stable outer surface. A new technique, utilizing the electromigration effect to check the relative surface mobility of atoms in the interior pores and exterior surfaces was used to support the conclusions deduced from thermal ageing 2 experiments. Finally, we speculate that the stability of the exterior surface could be reproduced in the interior if the chemistry of the paste was altered to allow formation of a passivating layer on the interior pores during the final stages of the sintering process, resulting in formation of a stable die attach material for applications of up to 400 °C, for which there is an urgent need.

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“…Of all the electrolytes considered or studied it was found that perchloric acid was the most suitable and was used in some preliminary studies by Craig and Hoffman [ 22 ]. The stability (or solubility) of silver in perchloric acid, in the absence of current flow, has recently been studied in detail [ 23 ]. It was found that silver is highly stable in perchloric acid (20 wt %), more stable in perchloric acid (20 wt %) containing a small amount (0.5 wt %) of silver Perchlorate, and practically inert in conductivity water.…”

Section: Introductionmentioning

confidence: 99%

Determination of the value of the faraday with a silver-perchloric acid coulometer

Craig¹,

Hoffman²,

Law³

et al. 1960

J. RES. NATL. BUR. STAN. SECT. A.

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An accurate value of t he faraday has bee n deter min ed by the e lectrolytic dissolution of metall ic silver in aq ueous solu tions of perchloric acid. Standards of electric curren t mass, a nd time a s maintained by t he National Bureau of Standards were utili zed in th~ determinatio ns. Th e electri c c l1l'rent was m easured in terms of th e standards of cle ctromotive force and electrical resistan ce. Silver of hi gh purity, freed fr om oxygen, was used.The value of t he faraday was found to be faraday = 96516.5 ± 2.4 coulombs gram -equival e nt-1 (physical scale). faraday = 96490.0 ± 2.4 coulombs gram -eq ui valent-1 (chemical scale) .These values were obtained usin g 107.9028 ± 0.001 3 and 107.8731 ± 0 .0013 for t h e atomic weigh t of silver on t h e phys ica l and ch e mical scales, resp ectively . ' The electrochemical eq uiva lent of sil ver was found to be electrochemical equivalent of s ilver = 1.117972 ± 0.000019 milligram coulomb-I.This value may be used in a n alternate meth od of defining t h e ampere in absolute value, llamely, t hat steady current which will d issolve 1.117972 milligrams of silver per seco nd a nd de pends only on t he standards of mass and t ime. The indicated un cer tainties are overa ll limi ts of error based on 95 percent co nfidence limi ts for t he mean an d a ll owan ces for t he effects of kn own sources of possible systematic errol'. I . IntroductionThe classic m ethod for the determination of the faraday involves the electrolytic deposition of silver on platinum from an aqueous solu tion of silve)' nitrate. This method h as been extensively studied and tmder closely sp ecified condi tions [1] 1 was used for many years in defining the international amper e. In the original work at th e National Bureau of Standards the national standards of electric current mass, and time were used, and great emphasis wa~ placed on the r eproducibility of the method as a ch eck on the stability of th e existing standards of electromotive for ce (Weston cell) and electrical r esistan ce (mercury ohm). In 1916 Rosa and Vinal [2] sum.-m arized th e work that h ad been done with the silver coulometer not only in yielding a value of the faraday but also in ftttaining conditions wherein reproducible r esults could be obtained. At th at time the consensus was th at tIl e silver coulome ter gave highly accurate as well ftS reproducible r esults and yielded a value of the faraday acc ura te to within 0.001 percent (10 ppm).However , 4 years earlier (in 1912) vVashburn and B ates [3 ] h ad proposed ftn improved 2 iodine coulom-1 F igures in brackets indicate the literature references at th e end of this paper. 2 T he iodine eoulometC!· bad bren studied earlier by H elTOtul [4]. D ann eel 15J, Kreider [6J , and Gallo l7J b ut tbese experimenters did not cla im higb aecm aey for t heir \vork .eter for which high reproducibility and accuracy wer e elaimed. In 1914 Vinal and B ates [8,9] made a direct comparison of the silver and iodine coulometer s in the labor atories of NBS and found that the two...

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Stability of silver and Pyrex in perchloric acid-silver perchlorate solutions and in conductivity water

Cited by 6 publications

References 2 publications

The electrochemical equivalent of pure silver - a value of the Faraday

The electrochemical equivalent of pure silver - a value of the Faraday

Microstructural evolution of sintered silver at elevated temperatures

Determination of the value of the faraday with a silver-perchloric acid coulometer

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