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Chemical lnstmentation Edited by GALEN W. EWING, Seton Hall University, So. Orange, N. J. 07079
These articles are inlended to s m e the readers o f ~ m JOURNAL s by calliny attention to new development8 in the theory, design,or availability of chemical laboratory instrumentation, or by presenting useful insights and ezplanations of topics that are of practical importance to those who use, or leach the use of, modern instrumentation and instncmental techniques. The editor invites correspondence from prospective contribulms.
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LXVI. Scanning Electron Microscopy-Part
Figwe 35. Unuwol orrongement of cryrtolr on fractured rurface of alumina.
Annemarie C. Reimschuessel ANied Chemkol Corporofion, Box 102 l R , Morrisfown, N. 1. 07960
A stndy conducted to investigate fracture phenomena of alumina, quenched over various temperature intervals revealed that both intergranular m d transgranular fracture had occurred. This is illustrated in Figures 33 and 34. An unusual moroholxv with resnect to the arrangements of alumina crystals observed on one of the fractured surfaces is shown in Figure 35. Scanning electron microscopy together with X-my diffraction studies of Zn crystals prepared potentiostatieally revealed that depending on the growth conditions either single crystal or polycrystalline dendrites had formed (11). Whereas twinned single crystal dendrites had formed a t a low growth rate of 24 p/min (Fig. 36), fern-like polycrystalline dendrites were the typical form grown at a rate of 67 plrnin. The strikingly different morphology of these "fast growing" Zn
dendrites from that of the "lo$growing" dendrites is illustrated in Figure 37. The effect of growth conditions on the morphology of Zn-oxide cl.ystals is illustrated in Figures 38 and 39. Whereas ZnO crystals prepared in an aqueous solution of ammonium tartrate were characterized by s. rosette-like arrangement of large lath shaped lamellae (Fig. 38), those formed in a solution of ammonium pentaborate in ethylene glycol resembled small conical protrusions orspike (Fig. 39). The results of an investigation on the effect of thermal treatment on the morphology of gold and nickel wire mesh are demonstrated in Figures 40-43. Annealing of the wires had resulted in a pronounced change of the morphology with respect to topography, grain size, and void formation. The sharp edged plxtelets characteristic of t.he gold control sample (Fig. 40a and 40b) had heen trans-
Figure 33. of olvmina.
Figure 34. of alumina.
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Example of intergranulor fracture
Exomple of tranrgronvlor frocture
Figure 36. zinc.
Twinned single rryrtol dendrite of
Figure 37. zinc.
Fernlike poly
