Mechanochemical behavior

A. N. Scian, Lopez. J. M. Porto, and E. Pereira. Mechanochemical activation of high alumina cements— hydration behavior Pt 1. Cement Concrete Res, 21(l) 51-60, January 1991. 

DE De Rossi, P Chiarelli, G Buzzigoli, C Domenici, L Lazzeri. Contractile behavior of electrically activated mechanochemical polymer actuators. Trans Am Soc Artif Intern Organ 32 157-162, 1986. 

The smallest subimit of these fullerene polymers is the C j2o dimer [368], Synthesis and examination of the properties of this molecule are, therefore, of considerable interest. Beside the solid-state mechanochemical reaction of with KCN -described in Section 3.2.3 -the dimer Cj2o can be synthesized at 5 GPa and 200 °C in good yields from a bis(ethylene-difhio)TTF-C5Q complex [369]. Cj2o is a dark brown solid that is almost insoluble in most organic solvents. 1 ts solubility decreases with increasing purity of the sample this behavior is also known for pristine C q. 

Table I. Behavior of Some Polymers Produced by Mechanochemical...

Although the mechanical behavior of tissues has been studied extensively, we know that interpretation of this behavior is made more complex by the time-dependence, also termed viscoelasticity. Therefore, we examine how the time-dependence can be corrected for in terms of the structural components. The goal of the mechanics sections is to relate mechanical behavior to the composition, arrangement, and environmental conditions that affect each tissue type. Finally, we examine how external forces balance with internal forces to modulate mechanochemical transduction. 

We have presented information on the elastic and viscous stress-strain behaviors for a variety of different ECMs in preparation for relating changes in external loading and mechanochemical transduction processes. In order to determine the exact external loading in each tissue that stimulates mechanochemical transduction processes we must take into account the balance between passive loading incorporated into the collagen network in the tissue and active loading applied externally. Inasmuch as the passive load is different for each tissue and is also a function of age (the tension in tissues decreases with age), the net load experienced at the cellular level is difficult to calculate. 

Mackenzie K.J.D, Temuujin J., Jadambaa T.S., Smith M.E., Angerer P., Mechanochemical synthesis and sintering behavior of magnesium alummate spinel. J. Mat. Science 2000 35 5529-35. 

Kojima Y., Isobe T., Senna M. El-Eskandarany M.S., Sumiyama K., Suzuki K. Comparison of mechanical complexation and thermal behavior of metal, oxide and hydrogel mixtures of the Al-Ti-0 system Int. J. Mechanochem. Mech. Alloying 1994. 1 32-41. 

It will be shown in a forthcoming review that a reversible change of conformation of linear macromolecules in solution may result in an appredable change of solution properties, and particularly of their viscosity. Such conformational changes and the resulting effects can be displayed by chemical means, and were actually described several years ago by Kuhn, Katchalsky and coworkers " and more recently by Osada and Saito. They are responsible for the mechanochemical behavior of polymer systems in the solid state, i.e. the conversion of chemical into mechanical energy . ... 

The modification of bitumen with SBS copolymer powder was done using the mechanochemically devuicanized GRT (Zhu et al., 2009). The penetration index, softening point, 5°C ductility, aging behavior, and rheological properties of bitumens modified by 8,10, and 12 wt.% GRT/SBS mixtures were measured. In comparison with the bitumen modified by incorporation of 5.5 wt.% SBS alone, the majority of properties of the blends were improved, except their penetration. Rheological properties indicated that at high temperatures 10 wt.% GRT/SBS-modified bitumen was better than SBS-modifled bitumen. The SEM observation of the fractured surfaces showed that bitumens mixed with the GRT/SBS powder had a better interfacial adhesion with matrix than with SBS alone. 

The molecular mechanism determining the chemical response induced by mechanical loading is crucial to identifying the mechanochemical properties of materials. Although it is challenging to address directly the behavior of the chemical bonds experimentally, the behavior of chemical bonds is reflected in mechanical properties in deformation. Thus, it is crucial to make an effort to measure the mechanical properties of materials and compare them with the computatimial results. From the computational methods, we could find reliable mechanisms that explain the behavior of chemical bonds on the atomic scale. 

Because the rupture and fracture occur over an extremely short time span, computational methods such as molecular dynamics and newly developed MD techniques become essential tools to analyze the structure of materials and the relations between mechanochemical processes and loading conditions. Through the simple MD simulations of HAP crystals, we have shown that the thickness of HAP can affect the behavior of ionic bonds under the tensile loadings, showing the importance of the chemical environments of HAP crystals and the crystal quality. The details of the effects of the HAP crystal quality and the nucleation mechanism would make an interesting follow-up study in the future. 

---