Rate of Sublimation of Ammonium Halides

Chaiken, Robert F.; Sibbett, Donald J.; Sutherland, Jessica E.; Mark, D. K. Van de; Wheeler, Ahlborn

doi:10.1063/1.1733003

Cited by 59 publications

(16 citation statements)

References 6 publications

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“…It is well known that NH 4 Cl undergoes sublimation at 338 1C according to NH 4 Cl (s) -NH 3 þHCl. We observed the complete elimination of the NH 4 Cl at 425 1C, which is consistent with Chaiken et al [25] who found that the typical sublimation weight loss of NH 4 Cl is over 90% when heated for E60 min at elevated temperatures. A slow ramp rate was employed here to ensure the gradual sublimation of NH 4 Cl and the release of HCl, which reacts at the surface of the SnO 2 NWs giving SnCl 4 , according to SnO 2 þ4HCl-SnCl 4 þ2H 2 O .…”

Section: Resultssupporting

confidence: 92%

A systematic study of the nitridation of SnO2 nanowires grown by the vapor liquid solid mechanism

Zervos

Othonos

2012

Journal of Crystal Growth

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Section: Resultssupporting

confidence: 92%

A systematic study of the nitridation of SnO2 nanowires grown by the vapor liquid solid mechanism

Zervos

Othonos

2012

Journal of Crystal Growth

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“…[ 29 ] the sublimation rate of NH 4 Cl increases by a factor of 10 4 when changing the temperature from T = 100 to 600 °C and the typical sublimation weight loss of NH 4 Cl is over 90% when heated for ≈60 min. It is interesting to point out here that this sublimation process is endothermic and the temperature is expected to be reduced only by a few tens °C in the case of NH 4 Cl [ 29 ]. The decomposition of NH 4 Cl enhances the porosity of the Sn melt and more importantly acts as a dispersant increasing the amount of Sn that is transferred into the gas stream.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Tin Nitride Sn x N y Nanowires by Chemical Vapour Deposition

Zervos

Othonos

2009

Nanoscale Res Lett

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Tin nitride (SnxNy) nanowires have been grown for the first time by chemical vapour deposition on n-type Si(111) and in particular by nitridation of Sn containing NH4Cl at 450 °C under a steady flow of NH3. The SnxNynanowires have an average diameter of 200 nm and lengths ≥5 μm and were grown on Si(111) coated with a few nm’s of Au. Nitridation of Sn alone, under a flow of NH3is not effective and leads to the deposition of Sn droplets on the Au/Si(111) surface which impedes one-dimensional growth over a wide temperature range i.e. 300–800 °C. This was overcome by the addition of ammonium chloride (NH4Cl) which undergoes sublimation at 338 °C thereby releasing NH3and HCl which act as dispersants thereby enhancing the vapour pressure of Sn and the one-dimensional growth of SnxNynanowires. In addition to the action of dispersion, Sn reacts with HCl giving SnCl2which in turn reacts with NH3leading to the formation of SnxNyNWs. A first estimate of the band-gap of the SnxNynanowires grown on Si(111) was obtained from optical reflection measurements and found to be ≈2.6 eV. Finally, intricate assemblies of nanowires were also obtained at lower growth temperatures.

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“…4 " 6 Similar experimental configurations have been employed in much earlier work on linear pyrolysis of vaporizable or decomposable materials, in which steady regression rates were measured when the material was pressed against a heated, impermeable flat plate. 7 The potential importance of compressibility in such experiments has been pointed out by Cantrell, 8 who had earlier 9 completed an analysis of such flows including compressibility effects but not considering the simplifications that arise in the limit of large Reynolds numbers, addressed herein.…”

Section: Introductionmentioning

confidence: 99%

Compressibility effects in thin channels with injection

1991

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A theoretical analysis of the inviscid flow between a porous plate and a parallel impermeable plate is performed for small values of the ratio of the plate separation distance to the lateral extent of the plates, for both planar and axisymmetric geometries. The problem of computing the flowfield is reduced to the solution of a single integral equation, which is accomplished numerically. The ratio of specific heats 7 is a parameter of the solution, and parametric results are presented from 7 = 1.0 to 1.67. The flow exhibits choking at a critical value of the lateral extent of the plate, in the vicinity of which the Mach number approaches unity. The results are needed in providing external boundary-layer conditions for studying the flame structure in the viscous region between two counterflowing streams when compressibility is important. IntroductionS UPERSONIC combustion in turbulent mixing layers locally can involve counterflowing streams in which compressibility is important, with the viscous and chemical effects restricted to a narrow layer at the stagnation plane. The outer portions of such counterflows are inviscid and do not experience exothermicity. As a first step toward analyzing the exothermic viscous layer, descriptions are needed of the inviscid counter flow. The present paper provides a solution for a model of the inviscid outer region. The model addresses the flow between a porous plate and a parallel impermeable plate for small values of the ratio of the separation distance between the plates to the lateral extent of the plates. Two such flows can describe the inviscid counter flow, with the viscous layer located at the impermeable plate between them. In addition, laboratory experiments can be designed, involving opposed flow between two porous plates, for studying diffusion-flame combustion under conditions in which compressibility is important. The present analysis provides the external-flow conditions required for the viscous-layer study.Theoretical analyses of flows between porous plates at high Reynolds numbers began with Proudman's study 1 of an incompressible, nonreacting fluid in a two-dimensional channel with porous walls through which the fluid is injected uniformly. Extensions of this work addressed both heat transfer 2 and combustion 3 in the same type of configuration. The last of these studies was directed toward facilitating quantitative interpretation of results of experimental measurements on counter flow diffusion flames. 4 " 6 Similar experimental configurations have been employed in much earlier work on linear pyrolysis of vaporizable or decomposable materials, in which steady regression rates were measured when the material was pressed against a heated, impermeable flat plate. 7 The potential importance of compressibility in such experiments has been pointed out by Cantrell, 8 who had earlier 9 completed an analysis of such flows including compressibility effects but not considering the simplifications that arise in the limit of large Reynolds numbers, addressed herein.A coordin...

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Rate of Sublimation of Ammonium Halides

Cited by 59 publications

References 6 publications

A systematic study of the nitridation of SnO2 nanowires grown by the vapor liquid solid mechanism

A systematic study of the nitridation of SnO2 nanowires grown by the vapor liquid solid mechanism

Synthesis of Tin Nitride Sn x N y Nanowires by Chemical Vapour Deposition

Compressibility effects in thin channels with injection

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