Nanocsövek előállítása, szerkezete és tulajdonságai = Preparation, structure, and properties of nanotubes

A kutatások célja a szén nanocsövek elektrokémiai úton történő előállítása során keletkező termék tulajdonságainak és a technológiai paraméterek közötti összefüggések kimutatása volt. A gyártási paraméterek között a szén katód alapanyagának morfológiája, a só olvadék összetétele, a hőmérséklet, valamint az elektrokémiai művelet paraméterei (áramsűrűség, potenciál, az elektrolízishez szükséges idő) bizonyultak lényegesnek. Az előállítási műveletekkel kapcsolatban megvizsgáltuk az elektrokémiai fémleválasztás kinetikáját is, amely a nanocső szintézis jobb megértését eredményezte. A nanocsöveket tartalmazó termék megtisztítása és az ehhez a lépéshez szükséges eljárások tanulmányozása képezte második feladatot. Tanulmányoztuk azokat a tisztítási módszereket is, amelyek segítségével a nanocsövek felülete módosítható. A nanocsöveket tartalmazó készítményt alagúteffektuson alapuló mikroszkópos vizsgálatoknak vetettük alá, és a pásztázó tűszondás mikroszkóppal meghatároztuk a csövek méretét, alakját, az egyes típusokba sorolt csövek gyakoriságát. A kísérleti eredményeket statisztikai módszerekkel értékeltük ki. A vizsgálatokat elméleti számításokkal egészítettük ki, amelyek célja annak megállapítása volt, hogy a különböző osztályokba sorolható nanocsövek mennyire stabilak. E vizsgálatok céljából több módszerrel is meghatároztuk a csövek aromás jellegét. | The main aim of this research was to determine the correlation between the parameters of the electrolysis and the experimental properties of the carbon nanotubes. The most important parameters, which could affect the quality of the nanotubes were found to be the morphology of the carbon cathode, the composition of the molten salt, the temperature and the parameters of the electrolysis itself (current density, applied potential, and the time period of electrolysis). In connection with these tasks we also studied the mechanism of metal deposition, which yielded new information on the formation of nanotubes. The second object of these investigations was the purification of nanotubes and the necessary steps needed to accomplish this task. Probes containing nanotubes were be investigated by using scanning-tunneling and atomic force microscopes. These investigations revealed the distribution of the various shapes, and thickness of the tubes. The experimental data were evaluated by using statistical methods. Experimental investigations were completed by theoretical calculations. The aim of these investigations was to determine the stability of various types of nanotubes

Enumeration of Kekulé Structures in Defective Patterns of Rectangular Graphite

The number of Kekulé structures is an indicator of the aromatic character of the underlying polybenzenoid. Graphite is a polybenzenoid. In this paper, a new algorithm is proposed for determining the number of Kekulé structures in rectangular graphite and its incomplete and defective variants. Defective patterns model functionalized structures. Moderate functionalization will cause a slight increase in the aromatic properties of the underlying patterns

An Algorithm for Computation of Bond Contributions of the Wiener Index

The Wiener index Wis usually obtained by adding distances between all pairs of vertices i and j (i, j = 1,2, ...N, where N denotes the total number of vertices). The Wiener index may also he obtained by adding all bond contributions We, i.e. W = L We, and We = L C\u27fj / Cij, where cij denotes the number of all the shortest paths between i and j that include edge e, and Cu denotes the total number of the shortest paths between vertices i and j. The summation has to be performed for all edges e and for all pairs of indices i and i. respectively. It is easy to calculate the bond contributions We for a cyclic graphs or for bridges. The present paper introduces an algorithm, which can be used to obtain bond contributions in cycle - containing graphs

The Detour Index

The detour index w is the sum of all entries in the upper triangle of the detour matrix LI, where the ij-th entry Lli} denotes the length of the longest path between vertices i and j of the underlying graph. The Wiener index Wand w are equivalent for acyclic structures, but are different in cycle-containing graphs. Similarly the hyper-Wiener index F and its analogue the hyper-detour index y are equivalent in acyclic structures and are different in cyclic structures. Several formulas were derived for w and y. Excellent correlations between boiling points and the composite indices (Ww)1I8 and (ry)1I10 were found in a series consisting of 77 cyclic and acyclic alkanes

Wiener Index: Formulas for Non-homeomorphic Graphs

The Wiener index (W) is a graph invariant. Because of its importance, various methods – numerical approaches and analytical formulas – have been proposed to compute W. Earlier formulas of W were derived for homeomorphic structures, polymers, and stars. The formulas are polynomials. In this paper, a method is proposed that allows calculating the coefficients of the polynomials in sets of non-homeomorphic structures

Constructive Enumeration of Chiral Isomers of Alkanes

The problem of exhaustive and non-redundant generation of formulas of chiral isomers of alkanes was considered. The procedure starts with the generation of optimal codes of all N-alkane structures (N denotes the number of carbon atoms.) and then the algorithm determines whether a given structure contains at least a single carbon atom, with four different substituents. In order to accomplish these tasks, two simple rules have been used to delete redundant structures and determine whether two (alkyl) branches are identical or not

Counting Kekulé Structures of Benzenoid Parallelograms Containing One Additional Benzene Ring

Formulas are given for counting Kekulé structures in a special class of benzenoids made up of benzenoid parallelograms to which a single benzene ring is added

On the Nature of Theoretical Research: Comments on Trinajstić\u27s Paper

In a recent paper1 Trinajstić discussed the relationship between theoretical and experimental research. The present paper is an attempt to more thoroughly discuss several problems raised by Trinajstić; namely, what is knowledge, the definition of science and the process of theoretical research