Crystallization and glass-transition phenomena were studied for amorphous chlorobenzene (CB)/toluene (TL) binary systems as
the function of composition. Samples were prepared by vapor-deposition onto cold substrates, and their structural changes
due to temperature elevation were monitored with Raman scattering and light transmission. It was found that the crystallization
temperature (Tc) of CB-rich amorphous samples increases as the TL concentration is increased. This is similar to the linear dependence of
glass-transition temperatures (Tg) of many organic compounds on the concentration of additive. Also found was that Tc of TL-rich supercooled-liquids decrease as the CB concentration is increased. Issues related to the two kinds of Tc are discussed briefly.
We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important
observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly
strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree
of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location
of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and
the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong
to the class of relatively strong glass-forming systems.
Authors:Hermínio Digo, Susana Pinto, and Joaquim Moura Ramos
The thermal behaviour of salicylsalicylic acid (CAS number 552-94-3) was studied by differential scanning calorimetry (DSC).
The endothermic melting peak and the fingerprint of the glass transition were characterised at a heating rate of 10C min-1. The melting peak showed an onset at Ton = 144C (417 K) and a maximum intensity at Tmax = 152C (425 K), while the onset of the glass transition signal was at Ton = 6C. The melting enthalpy was found to be ΔmH = 28.90.3 kJ mol-1, and the heat capacity jump at the glass transition was ΔCP = 108.10.1 J K-1mol-1. The study of the influence of the heating rate on the temperature location of the glass transition signal by DSC, allowed
the determination of the activation energy at the glass transition temperature (245 kJ mol-1), and the calculation of the fragility index of salicyl salicylate (m = 45). Finally, the standard molar enthalpy of formation of crystalline monoclinic salicylsalicylic acid at T = 298.15 K, was determined as ΔfHmo(C14H10O5, cr) = - (837.63.3) kJ mol-1, by combustion calorimetry.
Authors:Musa Gogebakan, Ibrahim Karteri, Baris Avar, and Celal Kursun
strength and corrosion resistance. Recently, new Mg-based amorphous alloys such as the Mg–TM–RE (TM = transition metal, RE = rare earth metal) systems with high tensile strength, good ductility and a wide supercooledliquid region have been obtained by
Authors:Krzysztof Papis, Maciej Korwin-Kossakowski, and Elżbieta Wenta-Muchalska
In spite of their cryobiological efficacy, minimum-volume vitrification methods suffer from the risk of microbiological contamination and are technically and/or manually demanding. In this study, the effects of a traditional, slightly modified vitrification method and vitrification using supercooled liquid nitrogen (VitMaster) applied for rabbit morula-stage embryos were compared. Embryos were equilibrated in a solution containing 1,2-propanediol (2.72 M) and glycerol (1.36 M) for 7 min and vitrified in 0.25-ml insemination straws after 1-min exposure to a vitrification solution containing additionally 1.0 M sucrose. Cooling was performed in ‘normal’ or supercooled liquid nitrogen. Regardless of the cooling method applied, high
survival and development rates of vitrified embryos were obtained. All embryos were intact after warming, and 61 out of 65 (93.8%) and 23 out of 24 (95.8%) embryos developed to the blastocyst stage after 48-h
culture of embryos vitrified in ‘normal’ or supercooled liquid nitrogen, respectively. The results suggest higher developmental ability of embryos vitrified in supercooled liquid nitrogen (91.7%
. 83.1% of embryos vitrified traditionally developed to more advanced, expanding and/or hatching blastocyst stages).
survival rate, tested for the traditional vitrification system only, revealed that 36.8% of embryos developed to term. The results show promise for establishing a fully successful method for rabbit embryo vitrification.
Authors:Y. Yoshihashi, H. Iijima, E. Yonemochi, and K. Terada
stability of amorphous drug in solid dispersion was estimated using differential
scanning calorimetry (DSC). Tolbutamide (TB) and flurbiprofen (FBP) were selected
as insoluble drugs in water. Polyvinylpyrrolidone (PVP) was selected as a
polymer for solid dispersion. Solid dispersions of various ratios of TB or
FBP and PVP-K25 were prepared by solvent evaporation method and the induction
period of crystallization from amorphous drug in solid dispersion was measured
by DSC. Compared with FBP, the induction period of crystallization from TB
was delayed by an addition of PVP. The improvement of the physical stability
by the addition of PVP-K25 was estimated from the activation energy of diffusion
of drug molecules and the interfacial free energy between drug crystal and
supercooled liquid of drug in solid dispersion. From thses results, the hindrance
of the diffusivity of the drug molecule might be mainly affected the delay
of the induction period of crystallization of TB and FBP.
Authors:S. Tomitaka, M. Mizukami, F. Paladi, and M. Oguni
Summary Thermal and dielectric properties of 2,2’-dihydroxybenzophenone were studied in relation with the potential progress of crystal nucleation and growth below the ordinary glass transition temperature, Tgα. Differential scanning calorimetry was carried out in a range 100-350 K. The α glass transition was found to occur at Tgα=239 K. Crystallization and fusion were observed to take place when the sample was cooled down to 103 K, but not observed when cooled to 203 K. Crystal nucleation was interpreted as having happened during annealing for a short time at 103 K which is much below the Tgα. Heat capacities were measured in a range 7-350 K by an intermittent heating method with an adiabatic calorimeter. The temperature, enthalpy and entropy of fusion were determined to be 334.46 K, 20.07 kJ mol-1 and 60.01 J K-1mol-1, respectively. Crystal growth was found to proceed even at 220 K below the Tgα, but no glass transition was detected below 220 K. Dielectric losses were measured in a temperature range of 100-250 K and a frequency range of 30Hz-10 kHz. β-Relaxation process was found dielectrically with the activation energy of 22.6 kJ mol-1, and the corresponding glass transition was expected to occur at 76.9 K. It is discussed, based on the “structurally ordered clusters aggregation” model for supercooled liquids and glasses, that the β process is potentially attributed to the crystal nucleation progressing at 103 K.
The subjects of the paper are the mechanism of vitrification
and the glass transition, and a definition of the temperature of the glass
transition. A comprehensive description of the structural changes occurring
in the amorphous phase (‘real’ and ‘semi-ordered’)
in a vicinity of the glass transition is presented. One of the major motivation
of our studies is to investigate the finite size effect of the glass transition
that could be related to the cooperative motion in supercooled liquids. Also,
new formula, describing the relaxation time temperature change, is applied
in order to better reveal themechanismof the supermolecular formation under
different internal and external factors. The results of the basic methods
of thermal analysis, obtained for different polymeric systems, were used in
this study. The proposed approach let us correlate the thermodynamic and the
structural parameters, which are estimated from the experiments, and describe
all well known shapes of the DSC traces, which can be recorded in the glass
transition region. Based on positron annihilation lifetime spectroscopy and
dilatometric results, the significance of the free and the specific volumes
for the activation of the relaxing units is discussed.
Authors:R. Golovchak, O. Shpotyuk, A. Kozdras, B. J. Riley, S. K. Sundaram, and J. S. McCloy
supercooledliquid over time [ 4 – 7 ]. To avoid this effect, the glasses with optimally-constrained covalent networks or almost saturated physical aging should be used in applications where the aging influence is detrimental on the desired glass properties
Authors:Hajnalka Breuer, Ferenc Ács, Kálmán Rajkai, and Ákos Horváth
. Interaction between soil hydrology and boundary-layer development. Bound.-Layer Meteorol. 38. 185–202.
Reisner, J., Rasmussen, R. M. & Bruintjes, R. T., 1998. Explicit forecasting of supercooledliquid water in winter storms using