Hysteresis high pressure

Adsorption-desorption isotherms of hydrocarbons on activated carbons usually exhibit hysteresis loops which may be limited with a closing point at a given relative pressure (High Pressure Hysteresis, HPH) or may persist down to very low pressure (LPH). LPH is observed less frequently than HPH and has not been so extensively studied. 

Which theoretically have neutral frameworks, show more rapid upswings at lower p/p than the carbons, possibly due in part to the presence of -OH groups at defect sites. Furthermore, VPI-5 is unusual in that it has a clear step at p/p = 0.02-0.06. Low pressure hysteresis was observed for each of these adsorbents, a small hysteresis loop was found even with the narrowest molecular sieve carbons. For the microporous carbons, it was noted that the hysteresis loop broadens as the pore width increased indicating that the high-pressure hysteresis is related to the process of capillary condensation. Again VPI-5 is unusual as it has a double hysteresis loop which closes at p/p - 0.07 the loop at lower p/p is associated with the step and cannot be explained by capillary condensation. 

The hysteresis loops to be found in the literature are of various shapes. The classification originally put forward by de Boer S in 1958 has proved useful, but subsequent experience has shown that his Types C and D hardly ever occur in practice. Moreover in Type B the closure of the loop is never characterized by the vertical branch at saturation pressure, shown in the de Boer diagrams. In the revised classification presented in Fig. 3.5, therefore. Types C and D have been omitted and Type B redrawn at the high-pressure end. The designation E is so well established in the literature that it is retained here, despite the interruption in the sequence of lettering. 

For solid nitrogen five modifications are known that differ in the packing of the N2 molecules. Two of them are stable at normal pressure (transition temperature 35.6 K) the others exists only under high pressure. At pressures around 100 GPa a phase transition with a marked hysteresis takes place, resulting in a non-molecular modification. It presumably corresponds to the a-arsenic type. Electrical conductivity sets in at 140 GPa. 

Dissipation via Quantum Chemical Hysteresis during High-Pressure Compression A First-Principles Molecular Dynamics Study of Phosphates. 

With 7 = 0.072 Nm-1 and 5 = 10 nm the effective pressure is of the order of P = 72 x 10s Pa. Such a high pressure can change the surface structure, cause mechanical deformation at the moving wetting line [250], and can lead to contact angle hysteresis [251-253], especially on soft polymer surfaces. 

When the mercury pressure is reduced, hysteresis is usually observed. This will reflect some of the mercury being permanently trapped in ink-bottle pores and, as such, the ink-bottle pore volume is given by the residual mercury entrapped when the mercury pressure is reduced to atmospheric pressure. Hysteresis, however, can also result from structural damage sustained due to the very high mercury pressures involved. 

Figure 13.6 Piezoelectric coefficient d and tan<5p of a single phase Bi4Ti30i2 ferroelectric ceramic with highly anisotropic grains, at room temperature. On the right are shown charge-pressure hysteresis loops at selected frequencies, with a clockwise hysteresis at 0.07 Hz and counter-clockwise hysteresis at 70 Hz. See [17] for details.

The mercury porosimetry intrusion-extrusion data is shown in Fig. 3. Two types of behaviour can be observed. In the case of mN2 and mEl the pores are filled at relatively low pressure and the extrusion curve is horizontal with negligible hysteresis. mVT4 and mlO show intrusion at higher pressures and hysteresis on extrusion - reintrusion corresponding to this high pressure region. 

Because of hysteresis effects the pressure for formation of the hydride may be higher than the dissociation pressure shown in Fig. 1, 1.12.1. The values of x shown in Table 1 are the approximate hydrogen content of the hydride when it is formed initially, but they usually increase with Hj pressure. At high pressure (150 MPa), the maximum possible hydrogen content in these intermetallic compounds is nine H atoms per formula unit. ... 

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