With the intensive development of ultrafast spectroscopic techniques, reaction dynamics and transition states can be investigated
at the subpicosecond time scale (0.05–3 ps). Aqueous ionic solutions represent a paradigm for the characterization of elementary
chemical steps at the microscopic level. The discrimination of very short-lived electronic states during electron transfers
in molecular liquids provide guidance for further theoretical developments on non-reactive and reactive dynamics in complicated
many body systems.
All complexes of the series [MO2L2]+ (M=Tc, Re; L=ethylenediamine (en), 1,3-diaminopropane (1,3-dap)) have been synthesized and their chemical reactivities investigated. The following properties were studied: stability of the aqueous solutions at different pH values, substitution kinetics, lipophilicity and protein binding. The complexes show very similar reactivity in aqueous solution. From a radiopharmaceutical point of view, no significant difference in their in vivo behavior is expected.
Authors:F. Awaja, F. Daver, E. Kosior, and F. Cser
Recycled poly(ethylene terephthalate) (R-PET) was chain extended with pyromellitic dianhydride (PMDA) in a commercial size
twin-screw reactive extrusion system. Temperature-modulated differential scanning calorimetry (TMDSC) was used to evaluate
the effect of the chain extension process on the thermal transitions and crystallinity of R-PET. Reactive extruded recycled
PET (RER-PET) samples were tested based on different PMDA concentration and reactive extrusion residence times. The glass
transition temperature (Tg) did not show a significant change as a function of PMDA addition or the extrusion residence time. Melting temperature (Tm) and crystallisation temperature (Tc) decreased with increasing PMDA concentration and with increasing extrusion residence time. RER-PET samples showed double
melting peaks, it is believed that different melting mechanism is the reason behind this phenomenon. The crystallinity of
RER-PET samples is lower than that of R-PET. RER-PET samples at constant PMDA concentration showed a decrease in crystallinity
with increasing extrusion residence time. Results suggest that the reactive extrusion process is more dependent on PMDA concentration
rather than reactive extrusion process residence time.
Upgrading of the efficiency of industrial power-production systems and environmental aspects, e.g. reduction of emission of greenhouse gases, is of particular interest to the Polish power sector, inherently depending on its own coal resources and coal processing technologies. Some information on fuel suitability for particular processing technology can be obtained from its reactivity. In this paper a procedure for testing coal chars reactivity, and the results obtained, in the process of steam gasification of coal in a laboratory-scale fixed-bed reactor are presented. The procedure is based on gas chromatographic analysis of a synthesis gas produced in the process. Chemometric methods (for example as hierarchical clustering) enabled discovery of the similarities and dissimilarities of coal samples and investigation of the relationships between the reactivity of coal chars and selected physical and chemical properties important in the steam gasification process.
In this paper, several small-scale screening test methods were discussed on evaluating the thermal hazard of reactive substances.
Generally the sensitivities of DSC and ARC are not high enough to evaluate the thermal hazards for all reactive substance,
especially, for those of complex reactions containing a phase and/or chemical reaction mechanism change in the lower temperature
range. Using the C80, however, the reaction can easily be detected in the lower temperature range due to its high sensitivity.
Therefore, the C80 gives generally more accurate results than DSC and ARC. Data from C80 and Dewar vessel were compared and
it indicates that the Dewar vessel has also high enough sensitivity to evaluate the thermal hazard and determine the heat
flux in lower temperature range of reactive substances.
Authors:L. Zane Miller, Jeremy L. Steinbacher, Tania I. Houjeiry, Ashley R. Longstreet, Kendra L. Woodberry, B. Frank Gupton, Banghao Chen, Ron Clark, and D. Tyler McQuade
Monodisperse silica microcapsules are typically fabricated using hard templating methods. Though soft templating methods are known, none yet provides a fast and easy method to produce monodisperse capsules. Herein, we describe a mesofluidic strategy whereby monodisperse droplets of reactive silica precursors are formed using a snap-off mechanism via a T junction. Both the mesofluidic system and the composition of the reactive silica formulation are critical features. Using solid- and solution-state 29Si nuclear magnetic resonance, scanning electron microscopy, and optical microscopy, we have developed models for why some formulations form exploding capsules, why some capsules contain crystalline materials, and why some capsules have thin or thick walls.
Thermal reactivity of eleven nitramines has been examined by means of non-isothermal differential thermal analysis, and the
data were analyzed according to the Kissinger method. The reactivity was expressed as the EaR−1 slopes of the Kissinger relationship. Electronic charges, qN, at nitrogen atoms of the nitramine molecules were calculated by means of ab initio DFT B3LYP/6-31G** method. The relationships
were confirmed between the slopes EaR−1 and the q values for the nitro groups that are primarily split off. Conclusions are made in relation to the mechanism of
initiation of polynitro compounds in general.
The reactivity of Zn3 V2 O8 towards ZnMoO4 was investigated by using DTA and XRD methods. A new compound of the formula Zn2.5 VMoO8 was found. It crystallises in an orthorhombic system. The melting temperature was determinated to be 8455C.
The reactivity of iron(III) orthovanadate(V) towards zinc divanadate(V) in the solid state was investigated over the whole
component concentration range. On the base of DTA and XRD measurements the phase diagram of the FeVO4-Zn2V2O7 system in the subsolidus area was constructed for the whole component concentration range.
Authors:B. Liu, P. Thomas, A. Ray, and J. Guerbois
of MgO obtained from calcination of magnesium carbonate at different temperatures
has been investigated by means of hydration in a constant relative humidity
environment at 40°C for periods up to 24 days. Natural magnesite and AR
grade basic MgCO3 calcined in the range of 500–1000°C
was characterised in terms of surface area, crystallite size, morphology,
and hydration rate.
It was found that the hydration rate is dependent
on the surface area and crystallite size where temperature was the main variable
affecting them. The most reactive MgO was produced at the lowest calcination
temperature with the highest surface area and the smallest crystallite size.
The basic MgO specimens showed higher degree of hydration compared to the
natural MgO specimens due to the smaller surface area and larger crystallite
size. The low MgO content of the starting natural magnesite is also attributable
to the lower reactivity. This preliminary study serves as a mean to investigate
potential utilisation of reactive MgO as a supplementary cementitious material
in eco-friendly cements.