Single crystals and dendritic formations of silver are grown on platinum electrodes by electrodeposition from a dense gaseous solution of silver nitrate in ammonia. Process is modification of hydrothermal process, and also differs from standard electrodeposition by permitting single crystals to be grown from hydrogen-bonded solvents

Naiditch, S.

Williams, R. A.

English

NASA Technical Reports Server

December 1970	 Brief 70-10676 
NASA TECH BRIEF H 
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nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Crystal Growing by Electrodeposition from Dense Gaseous Solutions 
Single crystals and dendritic formations of silver 
have been grown on platinum electrodes by electro-
deposition from a dense gaseous solution of silver 
nitrate in ammonia. The process is essentially a modi-
fication of the standard high temperature, high pres-
sure, hydrothermal process for growing crystals. How-
ever, unlike the standard hydrothermal process, which 
uses concentration gradients or chemical rates of solu-
tion as its driving force, the new method is driven by 
electric force in the form of electrodeposition. The 
method also differs from standard electrodeposition 
techniques in that it permits single crystals to be grown 
from a hydrogen-bonded solvent such as water or am-
monia. In normal, liquid-state electrolysis using such 
a solvent, hydrogen gas is evolved and trapped at the 
cathode surface as bubbles. Such bubbles often inter-
fere with the continuous growth of crystalline metallic 
deposits. In electrode position from a dense gaseous 
solution, however, because of the absence of surface 
tension, evolved hydrogen diffuses away from the 
cathode, and no bubbles are formed. 
In the experiments described, ammonia was selected 
as the solvent because of its convenient critical point 
(132.9°C; 112 atm.) and its chemical inertness toward 
metals. Silver nitrate was chosen as the salt because 
of its solubility in ammonia and the insolubility of the 
electrodeposited silver in ammonia. 
The electrodeposition was accomplished in a closed 
cell containing electrodes of platinum wire. The cell, 
made from 30 mm (OD) borosilicate glass tubing, was 
about 8 cm long with an internal volume of 35 to 40 cc. 
Reagent grade silver nitrate was placed in the cell 
and the cell was evacuated. Approximately 20 cc of 
high-purity liquid ammonia was then condensed into 
the cell, which was subsequently sealed and placed in 
a pressure vessel. During heating and electrodeposi-
tion, nitrogen gas pressure within the vessel was main-
tained at about 30 atm above the predicted internal 
cell pressure. 
Runs were made using current densities of I to 2 
mA/cm 2
 for time periods of from 600 to 800 sec, at 
temperatures of from —70°C to +140'C. The silver 
deposits became increasingly more crystalline as the 
critical temperature was approached. At temperatures 
above the critical point, needle-like single-crystal wires 
and dendrites up to 7 mm in length were produced. 
The observed triangular and square cross-sections of 
the central stems and branches of the dendrites sug-
gested screw dislocations in the (111) and (100) planes. 
The ease with which fairly large single crystals of 
silver were grown in the super-critical region suggests 
that the technique of electrodeposition from dense 
gaseous solution might be useful for growing whiskers 
or other desirable crystal forms of various metals. 
Note: 
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Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP70- 10676 
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application has been filed. Royalt y-free, nonexclusive 
licenses for its commercial use will be granted by 
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made to: 
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Pasadena, California 91103 (continued overleaf) 
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Government nor any person acting on behalf of the United States
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information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19700000655 2020-03-17T01:03:59+00:00Z
Source: S. Naiditch and R. A. Williams of
United Science Associates, Inc. 
under contract to
NASA Pasadena Office
(N PO- iO440) 
Brief 70-10676	 Category 03, 04


Crystal growing by electrodeposition from dense gaseous solutions

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