Melting point, size dependence

In addition to size-dependent melting points, size-dependent specific heats have been observed. At high temperatures, there is an increase in the specific... 

FIGURE 8-30 Heat denaturation of DNA. (a) The denaturation, or melting, curves of two DNA specimens. The temperature at the midpoint of the transition (tj is the melting point it depends on pH and ionic strength and on the size and base composition of the DNA. (b) Relationship between and the G=C content of a DNA. 

The process of crystallization proceeds via two distinct processes crystal nucleation and growth (Garside, 1985). The nucleation kinetics in fine droplets is often different from nucleation in the same liqnid in bulk. In a fine emulsion, the number of droplets exceeds the number of potential nncleation catalysts (impurities) present in the liquid oil. Thus, a proportion of the lipid is effectively catalyst free and must nucleate by other mechanisms. This may either be completely spontaneous homogeneous nucleation or, more probably, some catalytic effect of the droplet surface (Coupland, 2002). In either case, the crystallization temperature is greatly reduced below the melting point and depends both on particle size and on the nature of the emulsifier selected. For example, Higami and co-workers (2003) showed that the crystallization temperature of trilaurin molecules decreased from 18.9 °C, the crystallization temperature of the bulk lipid, to -9.5 °C when emulsified into droplets smaller than 100 nm. 

Any refractory material that does not decompose or vaporize can be used for melt spraying. Particles do not coalesce within the spray. The temperature of the particles and the extent to which they melt depend on the flame temperature, which can be controlled by the fueLoxidizer ratio or electrical input, gas flow rate, residence time of the particle in the heat zone, the particle-size distribution of the powders, and the melting point and thermal conductivity of the particle. Quenching rates are very high, and the time required for the molten particle to soHdify after impingement is typically to... 

Once the small nanoparticles were synthesized, we could easily obtain the monodispersed Au nanoparticles from 3.4 to 9.7 nm in size depending on the heat-treatment temperature from 150 to 250 °C. Thus the heat-treatment method is easily applicable to the metal nanoparticles with relatively low melting points like Ag as well. 

There is another important law that follows from the classical theory of capillarity. This law was formulated by J. Thomson [16], and was based on a Clausius-Clapeyron equation and Gibbs theory, formulating the dependence of the melting point of solids on their size. The first known analytical equation by Rie [17], and Batchelor and Foster [18] (cited according to Refs. [19,20]) is... 

Depending on the size and shape of the polymer particles, solid-state polycondensation (SSP) is performed at temperatures between 220 and 235 °C, which lie above the glass transition temperature ( 70-85 °C) and below the melting point (measured by DSC 245-255 °C) of PET. The temperature range for operation of SSP is rather small because on the one hand, the temperature should be as... 

---