Exothermic Differential Scanning Calorimetry Research Articles

Quantification of crystallinity during indomethacin crystalline transformation from α- to γ-polymorphic forms and of the thermodynamic contribution to dissolution in aqueous buffer and solutions of solubilizer.

The thermodynamic properties and dissolution of indomethacin (INM) were analyzed as models for poorly water-soluble drugs. Physical mixtures of the most stable γ-form and metastable α-form of INM at various proportions were prepared, and their individual signal intensities proportional to their mole fractions were observed using X-ray powder diffraction and Fourier transform infrared spectrometry at standard temperature. The endothermic signals of the α-form, with a melting point of 426 K, and that of the γ-form, with a melting point of 433 K, were obtained by differential scanning calorimetry (DSC). Furthermore, an exothermic DSC peak of the α/γ-phase transition at approximately 428 K was obtained. As we computed the melting entropy of the α-form and that of its transformation, the frequency of the transition was quantitatively determined, which indicated the maximum of the α/γ-phase transition at an α-form proportion of 68%. Subsequently, the thermodynamic contributions of the α- and γ-forms were analyzed using a Van't Hoff plot for solubility in aqueous solutions at pH 6.8. The dissolution enthalpies for α- and γ-forms were 28.2 and 31.2 kJ mol-1, respectively, which are in agreement with the quantitative contribution predicted by the product of the temperature and melting entropy. The contribution of melting entropy was conserved in different dissolution processes with aqueous solvents containing lidocaine, diltiazem, l-carnosine, and aspartame as solubilizers; their γ-form Setschenow coefficients were -39.6, +82.9, -17.3, and +23.2, whereas those of the α-form were -39.7, +80.4, -16.7, and +22.7, respectively. We conclude that the dissolution ability of the solid state and solubilizers indicate their additivity independently.

Precipitation in lean Mg–Zn–Ca alloys

While lean Mg–Zn–Ca alloys are promising materials for temporary implants, questions remain on the impact of Zn and Ca on the microstructure. In this context, the precipitation of Zn and Ca in Mg-1.5Zn-0.25Ca (in wt.%), initially extruded at 330°C, towards Mg–Ca binary precipitates or Ca–Mg–Zn ternary precipitates was probed in a multiscale correlative approach using atom probe tomography (APT) and analytical transmission electron microscopy (TEM). Particular focus was set on the ternary precipitate phase whose structure is debated. In the as-extruded material, the binary precipitates are made of hexagonal C14 Mg2Ca containing up to about 3 at.% of Zn. The ternary ones are based on the hexagonal Ca2Mg5Zn5 prototype structure with a composition close to Ca3Mg11Zn4, as deduced from atomically resolved EDS mapping and scanning TEM imaging, supported by simulations. The precipitation sequence was scrutinized upon linear heating from room temperature to 375°C, starting from the solutionized material. Three exothermic differential scanning calorimetry (DSC) peaks were observed, at respectively 125, 250 and 320°C. Samples were taken after the peak decays, at respectively 205, 260 and 375°C for structural analysis. At 205°C, APT analysis revealed Ca-rich, Zn-rich and Zn‒Ca-rich clusters of about 3 nm in size and with a number density of 5.7 × 1023 m−3. At 260°C, APT and TEM showed mono-layered Zn‒Ca-rich Guinier‒Preston (GP) zones of about 8 nm in size and with a number density of 1.3 × 1023 m−3. At 375°C, larger and highly coherent elongated precipitates were found, with a size of about 50 nm. They occur as binary Mg–Ca precipitates or ternary Ca2Mg6Zn3 precipitates, as deduced from scanning TEM-based energy dispersive X-ray spectroscopy (EDS) and nanodiffraction in TEM. Here, the binary precipitates outnumber the ternary ones, while in the as-extruded material the ternary precipitates outnumber the binary ones, which corresponds well to the calculated phase diagram. We correlated the microstructure to hardness probed by Vickers testing. The largest hardening relates to the end of the 125°C DSC peak and thus to GP zones, which outperform the hardening induced by the nanometer-sized clusters and the larger intermetallic particles. The complexity of the precipitation sequence in lean Mg–Zn–Ca alloys is discussed.

Omega‐3 fatty acid‐fortified butter: Preparation and characterisation of textural, sensory, thermal and physico‐chemical properties

The influence of adding flaxseed oil (2.9–5.1%) and flaxseed–whey protein concentrate (WPC) emulsion (4.8–8.6%) to cream as an omega‐3 fatty acid source was evaluated on the thermal, sensory and physico‐chemical properties of the developed butter. Pulsed nuclear magnetic resonance analysis revealed lower saturated fat content in the fortified butter than control butter. Differential scanning calorimetry exotherms and endotherms also corroborated these findings. Fortified butter prepared with 6.8% flaxseed oil–WPC emulsion had 3.7 times more alpha‐linolenic acid content than control and provided nearly 25% of the recommended dietary allowance in one serving. The developed butter exhibited improved spreadability.

Multi-scale thermal stability study of commercial lithium-ion batteries as a function of cathode chemistry and state-of-charge

This paper takes a critical look at the materials aspects of thermal runaway of lithium-ion batteries and correlates contributions from individual cell components to thermal runaway trends.An accelerating rate calorimeter (ARC) was used to evaluate commercial lithium-ion cells based on LiCoO2 (LCO), LiFePO4 (LFP), and LiNixCoyAl1-x-yO2 (NCA) at various states of charge (SOC). Cells were disassembled and the component properties were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and temperature-resolved X-ray diffraction (TR-XRD).The whole cell thermal runaway onset temperature decreases and peak heating rate increases with SOC due to cathode destabilization. LCO and NCA cathodes are metastable, with NCA cells exhibiting the highest thermal runaway rates. By contrast, the LFP cathode is stable to >500 °C, even when charged. For anodes, the decomposition and whole cell self-heating onset temperature is generally independent of SOC. DSC exotherm onset temperatures of the anodes were generally within 10 °C of the onset of self-heating in whole cell ARC. However, onset temperatures of the cathodes were typically observed above the ARC onset of whole cell runaway. This systematic evaluation of component to whole cell degradation provides a scientific basis for future thermal modeling and design of safer cells.

Thermal Stability of Athermal ω‐Ti(Fe) Produced upon Quenching of β‐Ti(Fe)

This work shows the formation of the athermal ω phase in alloy Ti–4 wt% Fe. The alloy under study, heat treated at 800 °C for 100 h and subsequently water quenched, is investigated using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The thermal stability of ω‐Ti(Fe) is investigated by differential scanning calorimetry (DSC). The DSC measurements show a cascade of several thermic events between 160 and 450 °C, and one strong and sharp exothermic DSC peak at ∼480 °C. The phase transformations and other microstructural changes behind these events are explained by complementary use of XRD, electron backscatter diffraction (EBSD), and TEM analyses that are performed on samples heated stepwise in the DSC apparatus. These experiments indicate that the embryos of athermal ω‐Ti(Fe) grow up to ∼400 °C and start to decompose into an α‐Ti(Fe) + β assemblage already at 450 °C. At ∼480 °C, the decomposition of the athermal ω‐Ti(Fe) phase is practically finished. Thermal stability of athermal ω‐Ti(Fe) is compared with the thermal stability of ω‐Ti(Fe) produced in a high‐pressure torsion (HPT) process, indicating a higher thermal stability of ω‐Ti(Fe) in the non‐deformed alloys.

Stored energy in ultrafine-grained 316L stainless steel processed by high-pressure torsion

The energy stored in severely deformed ultrafine-grained (UFG) 316L stainless steel was investigated by differential scanning calorimetry (DSC). A sample was processed by high-pressure torsion (HPT) for N=10 turns. In the DSC thermogram, two peaks were observed. The first peak was exothermic and related to the annihilation of vacancies and dislocations. During this recovery, the phase composition and the average grain size were practically unchanged. The energy stored in dislocations was calculated and compared with the heat released in the exothermic DSC peak. The difference was related to the annihilation of vacancy-like defects with a concentration of ∼5.2×10−4. The second DSC peak was endothermic which was caused by a reversion of α′-martensite into γ-austenite, however in this temperature range dislocation annihilation and a moderate grain growth also occurred. The specific energy of the reverse martensitic phase transformation was determined as about −11.7J/g.

Non-isothermal Characterization of the Precipitation Hardening of a Cu-11Ni-19Zn-1Sn Alloy

The precipitation hardening of a Cu-11Ni-19Zn-1Sn alloy has been studied by means of Differential Scanning Calorimetry (DSC), High-Resolution Transmission Electron Microscopy (HRTEM), and hardness measurements. The calorimetric curves, in the range of temperatures analyzed, show the presence of one exothermic reaction followed by an endothermic one. The exothermic DSC peak is due to the segregation of Cu2NiZn precipitates and it is associated to a noticeable improvement of the mechanical properties of the alloy. The endothermic effect is associated to the dissolution of the Cu2NiZn precipitates into the copper matrix for restoring the starting Cu-11Ni-19Zn-1Sn homogeneous solid solution. The reaction mechanisms of these processes have been proposed from the kinetic analysis of the exothermic and endothermic DSC signals. The results obtained point out that tin plays a decisive role on the precipitation hardening of the alloy, because age hardening is not observed in the case of a Cu-Ni-Zn ternary alloy of similar composition.

Semibatch RAFT copolymerization of acrylonitrile and N-isopropylacrylamide: Effect of comonomer distribution on cyclization and thermal stability

Utilizing reversible addition-fragmentation chain transfer (RAFT) polymerization, the composition profile of PAN-based copolymers becomes a tunable parameter in preparing carbon fiber precursors. In this work, poly(acrylonitrile-co-N-isopropylacrylamide) copolymers were prepared via a semibatch process mediated by 2-cyano-2-propyl dodecyl trithiocarbonate (CPDT). The monomer reactivity ratios were determined by the Fineman-Ross (FR), Kelen-Tüdos (KT), and non-linear least squares (NLLS) models. The number average sequence length of acrylonitrile (AN) was found to be highly dependent on the content of N-isopropylacrylamide (NIPAM). NIPAM was introduced at controlled rates into a reaction vessel in attempt to facilitate its distribution in the polymer backbone. These semibatch copolymers were evaluated based on their ring-closing cyclization efficiency, which was characterized by differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Significantly, DSC exotherms were reduced and cyclization occurred much faster reaching a greater thermal stability when NIPAM was introduced at slow feed rates.

Curing study and evaluation of epoxy resin with amine functional chloroaniline acetaldehyde condensate

Purpose – The purpose of this paper was to check effectiveness of amine functional chloroaniline acetaldehyde condensate (AFCAC) as a new curing agent for diglycidyl ether of bisphenol A (DGEBA) resin. For this purpose, first AFCAC was synthesised, characterised and then curing reaction was carried out. Design/methodology/approach – Equimolecular mixture of AFCAC and DGEBA was subjected to curing reaction, and the reaction was followed by differential scanning calorimetry (DSC) analysis. The kinetic studies of this curing reaction were also carried out from those DSC exotherms. The mechanical properties, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) of cured epoxy were also reported. Findings – DSC results reflected the effective first order curing reaction of AFCAC with epoxy resin. Mechanical properties reflected appreciable rigidity of AFCAC cured epoxy matrix and TGA showed that the cured epoxy networks were thermally stable up to around 297°C. Research limitations/implications – The curing agent AFCAC was synthesised by using chloroaniline and acetaldehyde in acid medium. There are some limitations for this procedure. The synthetic procedure is pH dependent. So reaction cannot be done at any pH value. The reaction must also be carried out at room temperature without any heating. To obtain low molecular weight curing agent, chloroaniline and acetaldehyde cannot be taken in equimolecular ratio because the equimolecular mixture of them produces high molecular weight condensate. This was shown in our previous publication. Some implications are also there. By changing amine and aldehyde other curing agents could be synthesised and the curing efficiency of those for epoxy resin could also be studied. Originality/value – Experimental results revealed the greater suitability of AFCAC as curing agent for DGEBA resin and novelty of AFCAC cured matrix in the field of protective coating, casting, adhesives, etc.

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II) Ions

The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA) has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC) were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity decrease caused by oxidative system, indicating HA protection from degradation, SEC analysis suggested that some other mechanisms leading to the bucillamine transformations without the decay of the viscosity may come into a play as well. Nonetheless, the link between the reduction of chemiluminescence intensity and disappearance of the differential scanning calorimetry exotherm at 270 °C for fragmented HAs indicates a particular role of the bucillamine in preventing the decrease of HA viscosity.

Investigation on the reaction of iron powder mixture as a portable heat source for thermoelectric power generators

This paper reports our investigation on the thermal behavior and ignition characteristics of iron powder and mixtures of iron with other materials such as activated carbon and sodium chloride in which iron is the main ingredient used as fuel. Thermal analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis were used to characterize the materials and for further understanding of reaction kinetics of the pyrophoric iron mixtures. The experimental results demonstrated that iron micron particles react exothermically to the oxygen in atmosphere and produced iron oxide with ignition temperature of 427.87 °C and heat generation of 4,844 J g−1. However, in this study, the pyrophoric iron mixture acts as a heat source for the thermoelectric power generators, the final mixture composition is determined to compose of iron powder, activated carbon, and sodium chloride with the mass ratio of approximately 5/1/1. The mixture generated two exothermic peaks DSC curves that showed ignition temperature of 431.53 and 554.85 °C and with a higher heat generation of 9,366 J g−1 at higher temperature. The effects of test pan materials and heating rate on the ignition were also examined by DSC method. Kinetic data such as the activation energy (Ea), the entropy of activation (ΔS#), enthalpy of activation (ΔH#), and Gibbs energy of activation (ΔG#) on the ignition processes was also derived from the DSC analysis. From the ignition temperature, heat generation, and kinetics test data, the mass ratio of 5/1/1 proved to generate the most amount of heat with high temperatures for the standalone thermoelectric power generators.

Preparation and Characterization of Poly (Acrylonitrile-co-1-Acryloylpyrrolidine- 2-Carboxylic Acid) with High Molecular Weight

1-acryloylpyrrolidine-2-carboxylic acid (APCA) monomer was copolymerized with acrylonitrile (AN) by aqueous suspension polymerization. High molecular weight (HMW) copolymers of AN and APCA [poly(AN-co-APCA)] with different copolymer composition were successfully prepared by employing azobisisobutyronitrile (AIBN) as initiator and polyvinyl alcohol (PVA) as dispersant in a H2O/N,N-dimethylformamide (DMF) mixture at 60°C. The PAN homopolymer and copolymers were characterized by elemental analysis (EA), nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The EA results indicated that the content of oxygen increased significantly in PAN copolymers with increasing APCA content. The APCA copolymer composition calculated from the EA was higher than that from 1H NMR spectra. The FTIR spectra of PAN and poly(AN-co-APCA) with different monomer ratios confirmed that the contents of APCA units in the copolymer chains increased with increasing APCA content in the feed. The DSC exotherms revealed that copolymerization with APCA could slow the rate of the exothermic reactions during the heat-treatment processes. The XRD results indicated that the PAN homopolymer and copolymers poorly crystallized and the crystallinity decreased with increasing APCA contents.

High temperature thermal stability of ultrafine-grained silver processed by equal-channel angular pressing

The high temperature thermal stability of the ultrafine-grained (UFG) microstructures in low stacking-fault-energy silver was studied by differential scanning calorimetry (DSC). The UFG microstructures in two samples having purity levels of 99.995 and 99.99 at.% were achieved by four passes of equal-channel angular pressing at room temperature. The defect structure was studied by electron microscopy, X-ray line profile analysis, and positron annihilation spectroscopy before and after the exothermic DSC peak related to recovery and recrystallization. The heat released in the DSC peak was correlated to the change of defect structure during annealing. It was found for both compositions that a considerable fraction of stored energy (~15–20 %) was retained in the samples even after the DSC peak due to the remaining UFG regions and a large density of small dislocation loops in the recrystallized volumes. The larger impurity level in Ag yielded a higher temperature of recrystallization and a lower released heat. The latter observation is explained by the much lower vacancy concentration before the DSC peak which is attributed to the segregation of dopants at grain boundaries resulting in a smaller free volume in the interfaces.

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)4X2, where M = Cu, X = Cl, NO3 and CH3COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)4Cl2 complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.

Crystallization and melting behavior of HDPE in HDPE/teak wood flour composites and their correlation with mechanical properties

AbstractThe nonisothermal crystallization behavior and melting characteristics of high‐density polyethylene (HDPE) in HDPE/teak wood flour (TWF) composites have been studied by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) methods. Composite formulations of HDPE/TWF were prepared by varying the volume fraction (ϕf) of TWF (filler) from 0 to 0.32. Various crystallization parameters evaluated from the DSC exotherms were used to study the nonisothermal crystallization behavior. The melting temperature (Tm) and crystallization temperature (Tp) of the composites were slightly higher than those of the neat HDPE. The enthalpy of melting and crystallization (%) decrease with increase in the filler content. Because the nonpolar polymer HDPE and polar TWF are incompatible, to enhance the phase interaction maleic anhydride grafted HDPE (HDPE‐g‐MAH) was used as a coupling agent. A shift in the crystallization and melting peak temperatures toward the higher temperature side and broadening of the crystallization peak (increased crystallite size distribution) were observed whereas crystallinity of HDPE declines with increase in ϕf in both DSC and WAXD. Linear correlations were obtained between crystallization parameters and tensile and impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Curing study of epoxy resin by new aromatic amine functional curing agents along with mechanical and thermal evaluation

To cure diglycidyl ether of bisphenol A (DGEBA) resin, with new curing agents like amine functional aniline formaldehyde condensates (AFAFC) and amine functional chloroaniline formaldehyde condensates (AFCFC) as a function of concentration of the curing agents, an investigation was carried out. The AFAFC and AFCFC were synthesized from the reaction of aniline and formaldehyde and chloroaniline and formaldehyde, respectively, in acid medium and characterized by FT-IR and NMR spectroscopic analyses, elemental analysis, viscosity measurements, mole of primary and secondary amine analysis and gel permeation chromatography (GPC) analysis. Equimolecular mixture of curing agent and epoxy resin was subjected to curing reaction and the reaction was followed by differential scanning calorimetry (DSC) analysis. The DSC exotherms showed the occurrence of effective curing reaction and the cure kinetics studied from those exotherms revealed that the curing reactions were first order. The mechanical properties, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) of cured epoxy were also reported.

Polymorphic occurrence and crystallization rates of tristearin/tripalmitin mixtures under non‐isothermal conditions

AbstractThe effect of composition and cooling rate on polymorphic occurrence and crystallization rates in binary mixtures of tripalmitoylglycerol (PPP) and tristearoylglycerol (SSS) has been studied using differential scanning calorimetry (DSC), light microscopy and X‐ray diffraction under constant cooling rates. In general, β and β' polymorphs were observed at cooling rates of 0.5 K/min and less, and the α form at higher cooling rates. Double peaks were observed in the DSC exotherms of mixtures containing more than 30% SSS. The X‐ray data showed that, when cooling at 0.5 K/min, the double peaks correspond to the crystallization of the α and β' forms. However, when cooling at 1 K/min and higher, the double peaks appear to arise from the crystallization of two α phases – one PPP rich and the other SSS rich. Light microscopy experiments also show two distinct morphologies, which corroborates this view. The apparent SSS‐rich phase crystallizes as irregular spherulites whereas the apparent PPP‐rich phase forms a fine crystal mass. Analyses of thermograms relating to the α form show that the amount of supercooling at the onset of crystallization is virtually independent of composition. However, peak width information shows that, once started, pure‐component samples crystallize faster than mixtures.

Influence of whitening on the degree of conversion of dental adhesives on dentin

The aim of this study was to analyze the extent of polymerization of different adhesive systems on whitened dentin. One adhesive of each class was investigated: Adper Scotchbond Multi Purpose (3M ESPE); One-Step (Bisco); Clearfil Protect Bond (Kuraray); and Xeno III (Dentsply DeTrey). Dentin disks were treated with Opalescence Xtra Boost (Ultradent) for 30 min and bonded immediately after 24 h or after 14 d of storage in 100% humidity at 37 degrees C. Unbleached dentin disks were prepared as controls. The extent of polymerization of bonded interfaces was obtained with differential scanning calorimetry (DSC) at 20, 40 and 60 s, and the data were statistically analyzed. The extent of polymerization obtained from DSC exotherms of adhesives applied immediately after whitening was significantly lower compared with controls. An increased extent of polymerization after storage was confirmed for all adhesives, and no difference with controls was found after 14 d. A prolonged irradiation time increased the curing rate for all the tested adhesives. This study supports the hypothesis that polymerization of the adhesive is reduced after dentin whitening and that delayed adhesive application reverses the polymerization inhibition. Prolonged polymerization intervals may counteract the inhibition of polymerization caused by the whitening procedure. Nevertheless, further in vivo studies should validate this issue.

Synergistic Interaction of Xyloglucan and Xanthan Investigated by Rheology, Differential Scanning Calorimetry, and NMR

A new synergistic interaction between tamarind seed xyloglucan and xanthan was found and investigated by rheology, differential scanning calorimetry (DSC), and NMR. The effect of the acetyl and pyruvate groups in the side chain in xanthan on the synergistic interaction was also examined. The shear moduli G' and G' ' of the mixture solution of xyloglucan and native (or acetate-free) xanthan increased steeply at around 22 degrees C upon cooling. An exothermic DSC peak appeared at the same temperature. A drastic decrease in the of the acetyl and pyruvate groups of the xanthan side chain was observed from 1H NMR spectra only in the mixture at low temperatures (<25 degrees C). It was found that the pyruvate group is more restricted in the mixture solution compared with the acetyl group. The mixture of xyloglucan and pyruvate-free xanthan showed no synergistic interaction. We concluded that this synergistic interaction is caused by the intermolecular binding between xyloglucan and xanthan, and, in the heterotypic junction zones, the xanthan side chain becomes a new state that is different from both the coil and helix states.

Nanocrystallization of gas atomized Cu47Ti33Zr11Ni8Si1 metallic glass

Cu47Ti33Zr11Ni8Si1 metallic glass powder was prepared by gas atomization. Decomposition in the amorphous alloy and primary crystallization has been studied by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The glassy powder exhibits a broad DSC exotherm prior to bulk crystallization. Controlled annealing experiments reveal that this exotherm corresponds to a combination of structural relaxation and nanocrystallization. A uniform featureless amorphous contrast is observed in the TEM prior to the detection of nanocrystals of 4–6 nm in size. High-resolution TEM studies indicate that this nanocrystalline phase has a close crystallographic relationship with the γ–CuTi phase having a tetragonal structure. The product of the main crystallization event is also nanocrystalline, hexagonal Cu51Zr14, having dimensions of 20 nm. However, there is no evidence for possible amorphous phase separation prior to the nanocrystallization events.