Altın Nanoparçacıklarla Katkılandırılan Nematik Sıvı Kristallerin İncelenmesi

Bu çalışmada E7 kodlu nematik sıvı kristal karışım altın nanoparçacıklar ile katkılandırılmıştır. Saf, %3 ve %12 altın nanoparçacıklar (ANP) ile katkılandırılan E7 nematik sıvı kristal karışımının elektriksel ve optiksel özellikleri incelenmiştir. Katkılandırılan ANP ile E7’ nin eşik voltajının düştüğü, dielektrik anizotropisinin arttığı ve optik anizotropisini değiştirdiği gözlemlenmiştir. Bu özelliklerin değişmesiyle sıvı kristal numunenin elektro-optik özellikleri altın nanoparçacık katkılandırma ile iyileşmiştir

Altın Nanoparçacıklarla Katkılandırılan Nematik Sıvı Kristallerin İncelenmesi

Bu çalışmada E7 kodlu nematik sıvı kristal karışım altın nanoparçacıklar ile katkılandırılmıştır. Saf, %3 ve %12 altın nanoparçacıklar (ANP) ile katkılandırılan E7 nematik sıvı kristal karışımının elektriksel ve optiksel özellikleri incelenmiştir. Katkılandırılan ANP ile E7’ nin eşik voltajının düştüğü, dielektrik anizotropisinin arttığı ve optik anizotropisini değiştirdiği gözlemlenmiştir. Bu özelliklerin değişmesiyle sıvı kristal numunenin elektro-optik özellikleri altın nanoparçacık katkılandırma ile iyileşmişti

A theory of melting of molecular crystals .3. The liquid crystalline phase

The Pople and Karasz theory of melting of molecular crystals was modified using the third repulsive energy parameter in our previous paper. The new modified model is applied to study thermodynamics of solid-nematic and nematic-isotropic liquid transitions. The thermodynamic properties are evaluated by the Bragg-Williams approximation. The results are compared with the predictions of the original Pople and Karasz theory and its volume dependence modification, as well as some experimental data

Altın Nanoparçacıklarla Katkılandırılan Nematik Sıvı Kristallerin İncelenmesi

Bu çalışmada E7 kodlu nematik sıvı kristal karışım altın nanoparçacıklar ile katkılandırılmıştır. Saf, %3 ve %12 altın nanoparçacıklar (ANP) ile katkılandırılan E7 nematik sıvı kristal karışımının elektriksel ve optiksel özellikleri incelenmiştir. Katkılandırılan ANP ile E7’ nin eşik voltajının düştüğü, dielektrik anizotropisinin arttığı ve optik anizotropisini değiştirdiği gözlemlenmiştir. Bu özelliklerin değişmesiyle sıvı kristal numunenin elektro-optik özellikleri altın nanoparçacık katkılandırma ile iyileşmişti

A theory of melting of molecular crystals .4. The complete picture of transition temperatures

The Pople and Karasz theory of melting of molecular crystals was modified using the third repulsive energy parameter and applied to study the thermodynamics of melting, solid-solid, solid-nematic and nematic-isotropic liquid transitions in bur series of previous papers. In this study, we give the complete pictures of transition temperatures and compare with the original Pople and Karasz theory and as well as its volume dependence modification which was done by Chandrasekhar et al.

A theory of melting of molecular crystals .1. Theory and evaluation of the thermodynamic properties of melting

The Pople and Karasz theory of melting of molecular crystals, which is based on the theory of melting of inert gas crystals by Lennard-Jones and Devonshire, is extended using a third energy parameter, W ''. The extension is done as follows: the previous repulsive energy parameter W is divided into two parts. The first part is the interaction between molecules which are on different sites with the same orientations, called again W. The second is the interaction between molecules on different sites and also different orientations, namely W ''. W '' is combined with the previous W' and the new W energy parameters by the arithmetic mean including an adjustable parameter. The thermodynamic properties are evaluated by the Bragg-Williams approximation. The theory is applied to plastic crystals and compared with the Pople and Karasz theory. By introducing a physical realistic coupling between orientational and positional order, v, the theory gives a solid state rotational transition and melting transition. For values of v less than or equal to 0.331 the two transitions are separate, while for values of v greater than or equal to 0.331 they coalesce. The quantitative predictions of the theory is compared with experimental results for plastic crystals by plotting entropy and volume changes versus melting/boiling temperature ratios. The agreement between our theory and the experimental data is better than the calculations of the Pople and Karasz theory, as result of the introduction of the parameter W '' in the present theory

Study of melting of molecular crystals by a modified Pople-Karasz model

A new modified model that combines the modified models of Chandrasekhar et al. with those of Keskin and Ozgan, which are based on the Pople-Karasz theory, is applied to study the thermodynamics of melting and solid-solid transitions of molecular crystals. The thermodynamic properties of the disordered system are evaluated relative to those of the perfectly ordered one using the lowest approximation of the cluster-variation method, which is identical to the mean-field approximation. A good agreement is found between the present modified theory and the available experimental data. For melting transitions the agreement is excellent and much better than with the calculations of the Pople-Karasz theory and its previous modified theories. Approximate agreement is obtained for the solid-solid transitions. However, for these transition the experimental agreement with the present modified theory is still better than previous modified theories except at zero and low pressures. (C) 2004 Elsevier B.V. All rights reserved