<i>In Situ</i> Observation of Solidification in an Organic Peritectic Alloy System

Abstract

Up to date very few organic substances have been reported that show a non-faceted/non-faceted (nf/nf) peritectic phase diagram in a temperature range suitable for direct observation in a micro Bridgman furnace setup. Sturz et al. [1] and Barrio et al. [2] studied the peritectic phase diagram for the organic model alloy TRIS (Tris(hydroxymenthyl)aminomethane) - NPG (Neopentylglycol). The phase diagram is based on thermal analysis by means of DSC measurements [1, 2] and evaluation of lattice parameters measured with x-ray diffractometry [2]. In the current work we present investigations on the system TRIS – NPG that have been obtained by optical investigations of directional solidification in a micro Bridgman-furnace with various initial alloy concentrations and pulling rates in a fixed temperature gradient. The phase diagram [1, 2] was confirmed by direct comparison of DSC measurements and optical investigations. Furthermore we present in situ observations of solidification in the peritectic region. They show a solidification behavior that was clearly distinguishable from the solidification in hyper- and hypoperitectic regions of the phase diagram.

Review of Ammonium Chloride–Water Solution Properties

“…T eq (12) where C T is estimated to be constant (0.005/K) from the fit of eq 12. The value used for d 0 to fit eq 11 was 3 × 10 −10 (m).…”

“…Ammonium chloride was used extensively in modeling metal solidification because it solidifies like metals, and the liquid melt has the advantage of being transparent. − Its melting temperature range is considerably lower that metal’s melting temperature, making the operating conditions much easier for experimental studies in the laboratory. Other metal analogue alloys were used in modeling solidification, such as SCN (succinonitrile), − NPG-TRIS, − or NaCl. , …”

Observation of peritectic couple growth for a hyper-peritectic alloy under microgravity conditions

“…Over the past few years, the authors of this study have employed the organic peritectic metal-like solidifying tris(hydroxymethyl)aminomethane-neopentyl glycol (TRIS-NPG) system [6] to investigate the dynamics of the formation of peritectic layered structures [7][8][9][10]. The advantage of such a transparent model alloy is that it enables in-situ observations of the occurring phenomena.…”

In-situ observation of coupled growth morphologies in organic peritectics

“…It has become obvious from investigations of directional solidified peritectic alloys (Zn-Ag [1], Sn-Cd [2][3][4][5], Cu-Sn [6], Pb-Bi [7][8][9][10][11], Zn-Cu [12][13][14], Sn-Sb [15][16], Ti-Al [17][18], Fe-Ni [19][20][21][22][23][24][25][26][27][28], Ni-Al [29], YBCO [30], Nd-Fe-B [31] and TRIS-NPG [32][33][34]) that peritectic systems show a variety of complex microstructures. Close or below the limit of constitutional undercooling of both solid phases isothermal peritectic coupled growth (PCG), cellular peritectic coupled growth, discrete bands, island bands, and oscillatory tree-like structures were found [35][36][37][38].…”

“…In the present work, the organic non-faceted/non-faceted (nf/nf) peritectic system TRIS (Tris-(hydroxylmenthyl)aminomethane)-NPG (Neopentylglycol) [41] is used as a model substance for metallic solidification by performing in-situ observations of peritectic solidification morphologies which occur close to the critical value for morphological stability [32][33][34]. Both organic substances show a low temperature faceted phase and a transparent non-faceted high temperature phase, which forms in an intermediate concentration range of the peritectic equilibrium, see Figure 1.…”