Shock-wave method

E-BN (E = explosion) is described as high pressure phase by a few scientists. For synthesis shock wave methods [25, 26] were used and also reactions at normal pressure with photon [27] or electron [28, 29] assistance. In a special three-dimensional phase-diagram (pressure, temperature, electrical field) the existence of the metastable E-BN was described [30]. 

Today BN synthesis by shock-wave methods is mainly used to produce superhard boron-carbon-nitrogen mixtures called heterodiamond [182, 183]. 

The p-T phase diagram of sulfur is about the most complicated amongst the chemicd elements, and many open questions still exist with respect to phase boundaries, structures in detail, and kinetics of phase transitions in the solid as well as in the hquid state. Not only the molecular and crystalline variety of sulfur contributes to this complexity but also the metastabihty of high-pressure phases which is related to the application of different experi-mentd procedures. For example, early structural studies on the p-T phase diagram of sulfur could not be performed in-situ. Therefore, in these experiments the sulfur samples were quenched from a selected temperature-pressure point to STP conditions. The results obtained by such a procedure depend strongly on the variables AT and Ap as well as on their time derivatives (gradients), dT/dt and dp/dt, respectively. Especially, dynamic compression (shock wave) methods may introduce further complications since melting of... 

Depending on the method of their preparation, the individual nanodiamond particles do not exist as isolated crystallites, but they form tightly bound agglomerates. Apart from unordered sp - and sp -hybridized carbon, they may also include other impurities. The latter may originate either from synthesis or purification, for example, finely dispersed material from the reactor walls may contaminate the sample (Section 5.3). This is especially true for material produced by the detonation or shock wave method, whereas hydrogen-terminated diamond nanoparticles do not show this effect. 

Another voluntary omission concerns dynamic (shock wave) methods. These methods have provided precious knowledge of the behaviour of high-density matter indeed they form the basis of our understanding of equations of state at high pressures and temperatures, and the high-pressure scale is founded upon such measurements. But their use requires too much highly... 

Pressure measurements above 5 GPa are presently based on a pressure scale which is derived from a combination of theoretical (or semiempirical) equation-of-state calculations and multiple comparisons with results obtained from shock-wave methods. 

Experimental shock-wave methods, or Brillouin scattering techniques used to measure elastic constants at either ambient, or non-ambient conditions. 

Other EoS have not been considered in this brief outline for the sake of brevity Poirier and Tarantola (1998), Jackson and Rigden (1996), Kumar and Bedi (1996), Holzapfel (1996), Kumar (1995). Also the use of the Rankine-Hugoniot equations related to shock wave methods (Ahrens 1987) is not discussed here. 

The plots are significantly curved, especially at high temperatures. The authors have been able to compare these plots with experimental data taken from various sources, each in a different temperature range. This includes the authors own results (31) on the reaction between H2 and CH s, obtained by the shock-wave method. The agreement is quite close in particular, the points obtained experimentally at temperatures above 1000 K lie way above the straight line extrapolated from the low-temperature results. The tunnel effect was taken into account in these calculations (see Section VLB) but does not seem to affect the plot appreciably. The authors calculate the activation parameters which best fit their calculated curves, and find dEajdT to be higher than predicted by the classical limit of the partition functions. 

Investigations by Fischer et al. [Fi 72], carried out with pressure jump and shock-wave methods, revealed that, in alcoholic solution, the rate-determining step of the formation and dissociation of transition metal halides was the departure of a coordinated solvent molecule from the coordination sphere of the metal. 

Zar] Dynamic yield, fractiue stress, shock wave method < 680°C / single crystal / 35Co-28Ni-25Fe, mass%... 

In Sect. 3.3.3, a peculiar dynamics in the hybrid PU-PHEMA semi-IPNs was discussed. In the work described in [239,240], a series of PU-PHEMA-ND nanocomposites with different matrix compositions and ND contents of 0.25, 1, or 3 wt% were studied. Their nanostructure, glass transition dynamics, and elastic properties were investigated in the combined CRS/AFM/DSC experiments. We revealed a possibility of large and specific impact of low content of 3D nanofiller on polymer matrix, without performing a special functionalization of its surface. For preparing nanocomposites, the NDs obtained by the shock-wave method, with the particle sizes of 2-lOOnm and specific surface area of 220m g were used. NDs were introduced into the reaction mixture at the stage of PU synthesis. 

Alongside the acoustic methods of measuring relaxation times at lower temperatures, the shock-wave method has also widely been used. 

The kinetics of micellization of perfluorinated surfactants has been investigated by Hoffmann and co-workers [74-80] by pressure jump and a shock wave method with conductivity detection [74-80]. Hoffmann and Ulbricht [75] also used a temperature jump relaxation technique [81] with optical detection, utilizing a pH indicator (thymol blue) to observe relaxation processes of a 1 1 mixture of perfluorooctanoic acid and its sodium salt. For micellar systems in which fast relaxation times could be measured, the parameters k /n, k lcr, a ln, and k /n were calculated. 

The pressure-jump method and a shock-wave method with conductivity detection have been used by Hoffmann and co-workers in their studies of micelles formed by perfluorinated surfactants [187-193]. The pressure-jump and shock-wave techniques were utilized in micellization studies on cationic surfactants with perfluorinated counterions as well [191]. 

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