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The dendritic growth of lead from gels
Journal of Crystal Growth 8 (1971) 8—12
i:
North-Holland Publishing C~o.
THE DENDRITIC GROWTH OF LEAD FROM GELS
H. M. LIAW and J. W. FAUST, JR.* Materials Research Laboratories, The Pennsylvania State University, University Park, Pennsylvania /6802, U.S.A.
Received 16 April 1970; revised manuscript received 16 July 1970 Lead dendrites were grown from gels, and their habit, morphology, and internal structure were studied. Growth was found to proceed in three stages. The first stage showed mainly single crystal dendrites growing in the <100> direction while the second and third stages gave dendrites growing in the >211> direction. All dendrites were faceted by {ll l} planes. The dendrites from the second and third stages were shown to grow by the twin plane re-entrant edge mechanism
Fig. I.
Lead dendrite spear grown in gels. 10
Taft and Stareck’), and Henisch, Vand and Hanoka2) reported that lead grew in gels in the form of dendrites. No information on the faceting planes nor growth direction were given. Enlarged pictures of individual spears of lead dendrites, fig. I, grown by Hanoka3) were examined and found to be strikingly similar to those of other fcc metals and semiconductors with the diamond cubic lattice grown from the meltZv), vapor5), and by electrodeposition6) (compare fig. I with fig. 34.5 in ref. 7 and fig. I in ref. 6). These dendrites were shown to grow by the twin plane re-entrant edge mechanism (TPREM). The striking similarity lead one of us to believe that the gel-grown dendrites grew by the TPREM. An investigation was undertaken to
study this. It is the purpose of this letter to report on the results of that investigation. The gel solution was prepared by titrating 0.85 M sodium metasilicate into an equal volume of 2.0 M acetic acid. To this gel solution, before it has started to gel, a desired volume of LOS M lead acetate was added. The mixed solution was then poured into growth cells especially designed for studying growth under a microscope. The time to set took from a couple of minutes to several days depending on the composition and pH of the solution. When the gel solution was set, the growth experiment was started by inserting a piece of zinc into the gel. The lead ions were then replaced from the gel medium, deposited on the zinc and grew as dendrites. Instead of conventional test tubes being used as the
Present address: College of Engineering, University of South Carolina, Columbia, South Carolina 29208, U.S.A. *
8
THE DENDRITIC GROWTH OF LEAD FROM GELS
Fig. 2.
Fig. 3.
9
<100 Dendrite grown in the first stage of the growth process. 100 x.
A fern-like dendrite grown in the second stage of the growth process. 100
growth cells, special thin glass cells were built with dimension 45 mm x 60 mm x 2.5 mm to fit under a microscope. These cells restrict the growth of the dendrites only to horizontal planes. The main purpose of
this investigation is to determine the growth habit and morphology of lead growth. After the dendrites had grown for 1 to 3 days, lengths of from 3 to 5 cm were obtained. The dendrites were
10
H. M. LIAW AND J. W. FAUST JR.
then removed from the gel and washed with distilled water. The structure of the dendrites were then studied both by X-rays and metallographic techniques. Laue photographs were taken perpendicular to the main faces of the dendrite. Since lead has a high mass absorption coefficient to X-rays, the twin spots of the dendrite could only be observed either by thining the dendrite by chemical polishing or by increasing the voltage ofX-ray beam. The dendrites for the metallographic examination were mounted in Selectron and crosssectioned perpendicular to the direction of growth. The lapping and polishing of the specimen followed the standard procedure. The polished surface of the dendrites were etched by (3 %) H 202 : HAc : H20 (3:2:2) to reveal the microstructure in the dendrite, As had been found by others, lead dendrites were obtained. The growth process was found to be in three stages. The first stage, when the zinc started to react with ions lead in thenuclei gel, hundreds or thousands of blacklead spongy were formed. The black spongy nuceli grown at this stage had secondary branches and extended three dimensionally perpendicular to each other (fig. 2). Few other morphologies were observed at this stage of growth. After a period of growth, however, it was found that the number of twodimensional fern-like dendrites increased at the expense ofthe three-dimensional dendrites. Furthermore, the two-dimensional fern-like dendrites continued to grow. The second stage of the growth process started when two-dimensional fern-like dendrites only were growing. A typical dendrite at this stage of growth is shown in fig. 3, in which the main stalk and branching limbs are distinctly observed. The growth of the twodimensional dendrites was primarily in the extension of the main stalk so that the structure of the dendrites was still thin and delicate. In the third stage of growth the space between the dendrite branches began to fill in. The primary and secondary limbs of the dendrites then became indistinct. It was not unusual that the fern-like dendrites finally grew to become lath-like or plate-like crystals as shown in fig. 4. This same sequence was found for several other reducing metals and for several variations in the gel composition. The three-dimensional dendrites which grew in the first stage branched at 90° to each other. The main stalk extended horizontally in <100> direction, from
which primary branches also grew in <100> directions both in the horizontal and vertical directions. The morphology of the dendrites at this stage of growth process is similar to that of dendrites grown from melt by Weinberg and Chalmers8). The tips of the dendrites were thicker than the primary stalk and well defined octahedral facets were observed. The two-dimensional fern-like and plate-like dendrites which grew at the second and third stages of the growth process are also faceted by { Ill } planes. The main stalk of the dendrites grew in <211> direction. Two types of branches were observed. For the most part, the dendrites branch in <211> directions so that the main stalk and the primary branches make an angle of 600. More rarely, the dendrites branch in <110> directions so that the branches make an angle of 900. Occasionally it was found that the propagation of the main stalk was not straight. “tile-roof” structure 9) for The his electrodeposited lead described by Wranglen dendrites was observed. The “tile-roof” was constructed in the fashion of unaligned stacking of octahedral platelets. The extension of the octahedral platelets was in the <211> direction and the overall direction of the main stalk deviated a few degrees from the <211> direction. The degree of the deviation ranged from 3 up to 15°.However, about 110 of deviation was most often observed, which means that the overall propagation direction of the main stalk was near to <321> which is an allowable direction for twined growth according to the rules of Faust and Johfli 0). The Laue photographs in addition to giving the above mentioned faceting planes and the growth direction, showed that a six-fold symmetry instead of threefold symmetry exists in the <111> direction of the main face of the dendrite. This indicates the presence of a 1800 rotation twin parallel to {l 1 l} main faces in the dendrites of fcc structure. Ogburn et al. ‘)reported that lead dendrites grown by electrodeposition grew in direction other than the <211> and contained twist boundaries rather than twin planes. In our studies over thirty dendrites were examined by the Laue technique. Measurements were made to better than directly from the Laue films. All films were similar, showing growth in the <211> direction and occasionally in the <321> direction (the “tile-roof” structure) and the six fold symmetry. No other spots were found that would suggest a twist ~-°
THI: DFNDRITI(
____
-
______
-
.
I
.,
_______
~‘1.,
11
GROWTH OF LIAD FROM GI.1.S
I.
4~V “7’S- -
~
~
f
.~
S
— .
..
~‘
. .
,.
.
-: Fig. 4.
A
plate-like “dendritc~ gro~~ n in the final stage of gros~thpro~css.100
~ ~
~
4
~
Fig. S.
~
.
rç~
~T~I
( ross—section of a fern—like dendrite showing i~in planes. .500
boundary. Instead ihe Laue lilms were strikingly 2) on copper densimilar to those given by Ogburn’ dritcs grown b~ electrodeposition and reported to have twin planes.
The metallographic technique also that are the closed-space twin planes parallel to the shows main faces sand~ichedin the center of the dendrites and extend across the entire dendrite. The spacing of the twin
12
H. M. LIAW AND J. W. FAUST JR.
planes was always less than one micron so that the exact number of twin planes could not be resolved with the optical microscope. In addition to this twin lamella, other {ll 1} twin planes closed to the main faces were also observed in some dendrites (fig. 5). The twin planes were found in all of the dendrites from the second and third stages. These investigations show that the lead dendrites grown in gels grow by the twin re-entrant edge mechanism reported by Faust and John1 0) References 1) R. Taft and J. Stareck, J. Chem. Educ. 7 (1930) 1520.
2) H. K. Henisch, V. Vand and J. Hanoka, private communica~
tion. 3) J. Hanoka, private communication.
4) J. W. Faust, Jr. and H. F. John, Trans. Met. Soc. AIME 233
(1965) 230.
5) J. W. Faust, Jr., unpublished results.
6) J. W. Faust, Jr. and H. F. John, J. Electrochem. Soc. 108 (1961) 109. 7) 0. Lindberg and J. W. Faust, Jr., in: Compound Seiniconductors, 1: Preparation of 111—V Compounda, Eds. R. K.
Willardson and H. L. Goering (Rheinhold, New York, 1962). 8) F. Weinberg and B. Chalmers, Can. J. Phys. 29 (9951) 382. 9) G. Wranglen, Acta Polytech. 182 (1955) I. 10) H. F. John and J. W. Faust, Jr., in: Metallurgy of Elemental and Compound Semiconductors, Ed. R. Grubell (lnterscience, New York, 1961). 11) F. Ogburn, C. Bechtoldt, J. B. Morris and A. de Koranyi, J. Electrochem. Soc. 112 (1965) 574. 12) F. Ogburn, J. Electrochem. Soc. 111 (1964) 870.
i:
North-Holland Publishing C~o.
THE DENDRITIC GROWTH OF LEAD FROM GELS
H. M. LIAW and J. W. FAUST, JR.* Materials Research Laboratories, The Pennsylvania State University, University Park, Pennsylvania /6802, U.S.A.
Received 16 April 1970; revised manuscript received 16 July 1970 Lead dendrites were grown from gels, and their habit, morphology, and internal structure were studied. Growth was found to proceed in three stages. The first stage showed mainly single crystal dendrites growing in the <100> direction while the second and third stages gave dendrites growing in the >211> direction. All dendrites were faceted by {ll l} planes. The dendrites from the second and third stages were shown to grow by the twin plane re-entrant edge mechanism
Fig. I.
Lead dendrite spear grown in gels. 10
Taft and Stareck’), and Henisch, Vand and Hanoka2) reported that lead grew in gels in the form of dendrites. No information on the faceting planes nor growth direction were given. Enlarged pictures of individual spears of lead dendrites, fig. I, grown by Hanoka3) were examined and found to be strikingly similar to those of other fcc metals and semiconductors with the diamond cubic lattice grown from the meltZv), vapor5), and by electrodeposition6) (compare fig. I with fig. 34.5 in ref. 7 and fig. I in ref. 6). These dendrites were shown to grow by the twin plane re-entrant edge mechanism (TPREM). The striking similarity lead one of us to believe that the gel-grown dendrites grew by the TPREM. An investigation was undertaken to
study this. It is the purpose of this letter to report on the results of that investigation. The gel solution was prepared by titrating 0.85 M sodium metasilicate into an equal volume of 2.0 M acetic acid. To this gel solution, before it has started to gel, a desired volume of LOS M lead acetate was added. The mixed solution was then poured into growth cells especially designed for studying growth under a microscope. The time to set took from a couple of minutes to several days depending on the composition and pH of the solution. When the gel solution was set, the growth experiment was started by inserting a piece of zinc into the gel. The lead ions were then replaced from the gel medium, deposited on the zinc and grew as dendrites. Instead of conventional test tubes being used as the
Present address: College of Engineering, University of South Carolina, Columbia, South Carolina 29208, U.S.A. *
8
THE DENDRITIC GROWTH OF LEAD FROM GELS
Fig. 2.
Fig. 3.
9
<100 Dendrite grown in the first stage of the growth process. 100 x.
A fern-like dendrite grown in the second stage of the growth process. 100
growth cells, special thin glass cells were built with dimension 45 mm x 60 mm x 2.5 mm to fit under a microscope. These cells restrict the growth of the dendrites only to horizontal planes. The main purpose of
this investigation is to determine the growth habit and morphology of lead growth. After the dendrites had grown for 1 to 3 days, lengths of from 3 to 5 cm were obtained. The dendrites were
10
H. M. LIAW AND J. W. FAUST JR.
then removed from the gel and washed with distilled water. The structure of the dendrites were then studied both by X-rays and metallographic techniques. Laue photographs were taken perpendicular to the main faces of the dendrite. Since lead has a high mass absorption coefficient to X-rays, the twin spots of the dendrite could only be observed either by thining the dendrite by chemical polishing or by increasing the voltage ofX-ray beam. The dendrites for the metallographic examination were mounted in Selectron and crosssectioned perpendicular to the direction of growth. The lapping and polishing of the specimen followed the standard procedure. The polished surface of the dendrites were etched by (3 %) H 202 : HAc : H20 (3:2:2) to reveal the microstructure in the dendrite, As had been found by others, lead dendrites were obtained. The growth process was found to be in three stages. The first stage, when the zinc started to react with ions lead in thenuclei gel, hundreds or thousands of blacklead spongy were formed. The black spongy nuceli grown at this stage had secondary branches and extended three dimensionally perpendicular to each other (fig. 2). Few other morphologies were observed at this stage of growth. After a period of growth, however, it was found that the number of twodimensional fern-like dendrites increased at the expense ofthe three-dimensional dendrites. Furthermore, the two-dimensional fern-like dendrites continued to grow. The second stage of the growth process started when two-dimensional fern-like dendrites only were growing. A typical dendrite at this stage of growth is shown in fig. 3, in which the main stalk and branching limbs are distinctly observed. The growth of the twodimensional dendrites was primarily in the extension of the main stalk so that the structure of the dendrites was still thin and delicate. In the third stage of growth the space between the dendrite branches began to fill in. The primary and secondary limbs of the dendrites then became indistinct. It was not unusual that the fern-like dendrites finally grew to become lath-like or plate-like crystals as shown in fig. 4. This same sequence was found for several other reducing metals and for several variations in the gel composition. The three-dimensional dendrites which grew in the first stage branched at 90° to each other. The main stalk extended horizontally in <100> direction, from
which primary branches also grew in <100> directions both in the horizontal and vertical directions. The morphology of the dendrites at this stage of growth process is similar to that of dendrites grown from melt by Weinberg and Chalmers8). The tips of the dendrites were thicker than the primary stalk and well defined octahedral facets were observed. The two-dimensional fern-like and plate-like dendrites which grew at the second and third stages of the growth process are also faceted by { Ill } planes. The main stalk of the dendrites grew in <211> direction. Two types of branches were observed. For the most part, the dendrites branch in <211> directions so that the main stalk and the primary branches make an angle of 600. More rarely, the dendrites branch in <110> directions so that the branches make an angle of 900. Occasionally it was found that the propagation of the main stalk was not straight. “tile-roof” structure 9) for The his electrodeposited lead described by Wranglen dendrites was observed. The “tile-roof” was constructed in the fashion of unaligned stacking of octahedral platelets. The extension of the octahedral platelets was in the <211> direction and the overall direction of the main stalk deviated a few degrees from the <211> direction. The degree of the deviation ranged from 3 up to 15°.However, about 110 of deviation was most often observed, which means that the overall propagation direction of the main stalk was near to <321> which is an allowable direction for twined growth according to the rules of Faust and Johfli 0). The Laue photographs in addition to giving the above mentioned faceting planes and the growth direction, showed that a six-fold symmetry instead of threefold symmetry exists in the <111> direction of the main face of the dendrite. This indicates the presence of a 1800 rotation twin parallel to {l 1 l} main faces in the dendrites of fcc structure. Ogburn et al. ‘)reported that lead dendrites grown by electrodeposition grew in direction other than the <211> and contained twist boundaries rather than twin planes. In our studies over thirty dendrites were examined by the Laue technique. Measurements were made to better than directly from the Laue films. All films were similar, showing growth in the <211> direction and occasionally in the <321> direction (the “tile-roof” structure) and the six fold symmetry. No other spots were found that would suggest a twist ~-°
THI: DFNDRITI(
____
-
______
-
.
I
.,
_______
~‘1.,
11
GROWTH OF LIAD FROM GI.1.S
I.
4~V “7’S- -
~
~
f
.~
S
— .
..
~‘
. .
,.
.
-: Fig. 4.
A
plate-like “dendritc~ gro~~ n in the final stage of gros~thpro~css.100
~ ~
~
4
~
Fig. S.
~
.
rç~
~T~I
( ross—section of a fern—like dendrite showing i~in planes. .500
boundary. Instead ihe Laue lilms were strikingly 2) on copper densimilar to those given by Ogburn’ dritcs grown b~ electrodeposition and reported to have twin planes.
The metallographic technique also that are the closed-space twin planes parallel to the shows main faces sand~ichedin the center of the dendrites and extend across the entire dendrite. The spacing of the twin
12
H. M. LIAW AND J. W. FAUST JR.
planes was always less than one micron so that the exact number of twin planes could not be resolved with the optical microscope. In addition to this twin lamella, other {ll 1} twin planes closed to the main faces were also observed in some dendrites (fig. 5). The twin planes were found in all of the dendrites from the second and third stages. These investigations show that the lead dendrites grown in gels grow by the twin re-entrant edge mechanism reported by Faust and John1 0) References 1) R. Taft and J. Stareck, J. Chem. Educ. 7 (1930) 1520.
2) H. K. Henisch, V. Vand and J. Hanoka, private communica~
tion. 3) J. Hanoka, private communication.
4) J. W. Faust, Jr. and H. F. John, Trans. Met. Soc. AIME 233
(1965) 230.
5) J. W. Faust, Jr., unpublished results.
6) J. W. Faust, Jr. and H. F. John, J. Electrochem. Soc. 108 (1961) 109. 7) 0. Lindberg and J. W. Faust, Jr., in: Compound Seiniconductors, 1: Preparation of 111—V Compounda, Eds. R. K.
Willardson and H. L. Goering (Rheinhold, New York, 1962). 8) F. Weinberg and B. Chalmers, Can. J. Phys. 29 (9951) 382. 9) G. Wranglen, Acta Polytech. 182 (1955) I. 10) H. F. John and J. W. Faust, Jr., in: Metallurgy of Elemental and Compound Semiconductors, Ed. R. Grubell (lnterscience, New York, 1961). 11) F. Ogburn, C. Bechtoldt, J. B. Morris and A. de Koranyi, J. Electrochem. Soc. 112 (1965) 574. 12) F. Ogburn, J. Electrochem. Soc. 111 (1964) 870.