Papers by Keyword: Chemical Bond

Abstract: Nowadays, a lot of information on structure and properties of a wide variety of substances and materials has been accumulated. Yet, there is a lack of systemic universal approaches to assessing their structure and properties, including developing the effective approaches for monitoring and analysing various materials. It is of special interest in this respect to assess the effects of the chemical bond type on structure and properties of substances and materials. However, searching for necessary data on the effects of chemical bonds on structure of substances and materials is a rather laborious process. The authors, relying on the intermediate nature of chemical bonds of compounds of elements in any metallic and non-metallic material, as well as the system of chemical bonds and compounds developed by them in the form of a “Chemical Triangle”, produced an algorithm for creating a computer programme. It implies systematising of the database on the effect of chemical bond type on its length and energy, structure and various physicochemical and mechanical properties of homo-and heteronuclear compounds and materials. Development of such a specialised computer programme greatly simplifies this process, providing more efficient analysis and control of materials.

Abstract: Lactide (LA) and PEG as raw materials, 2,2-Dimethylol Propionic Acid (DMPA) as initiator, hexamethylene diisocyanate (HDI) as coupling agent, amphiphilic block copolymer PLA-PEG with side carboxyl group was synthesized. A novel PLA-PEG-PTX pro-drug was prepared through the esterification reaction between the side carboxyl group on copolymer and hydroxyl group on paclitaxel. Its structure was characterized with ¹H-NMR and FT-IR. The pro-drug micelles were prepared by solvent evaporation method. The particle size of the micelles was determined by nanoparticle tracking analyzer, the micro structure of the micelles was determined by TEM, and the drug release properties were investigated by dialysis experiments. Results showed that the pro-drug micelles are spherical with core-corona structure and major particles size in 55-85nm. The PLA-PEG750-PTX (molar ratio of LA to DMPA as 40 to 1) pro-drug micelles released paclitaxel slowly and steadily without obvious burst release in buffer solution with pH=7.0, and its cumulative release rate reached to 36% in 10 hours. PLA-PEG750-PTX pro-drug micelles have a certain sustained-release effect, which is beneficial to improve the anti-tumor effect of paclitaxel.

Abstract: The geometric shape of a crystal can be simulated via a thermodynamic model using breaking bond energy calculations. When this model was applied to the case of the KDP crystal, a thermodynamic description of the KDP crystal growth was successfully developed, which was consistent with experimental observations. Additionally, the effect of surface chemistry on the morphology of the KDP crystal was also investigated using the model based on the surface energy of the KDP crystal. These results confirm that bond making and breaking strongly influence the thermodynamic morphology of the KDP crystal during the crystallization.

Abstract: A chemical bond simulation was proposed to quantitatively calculate the growth rate from the kinetic model of the crystal-solution interface. When this approach was applied to the cases of potassium dihydrogen phosphate (KDP) crystals grown from the solution with different surpersaturation, the growth behaviors of KDP crystals were predicted and the calculated results were consistent with the experimental data. These results demonstrate that regulating the distribution of the chemical bonds between the crystal and solution interfaces can effectively control the crystal morphology. Seeding experiments with the chemical bond simulation may have significant potential towards the development of shape-controlled growth with defined conditions.

Abstract: In this article, technology of catalyzed oxidation desulphurization with manganese sand fixed bed was employed to conduct the experiment of catalyzed oxidation desulphurization for unhairing alkali swelling wastewater in leather making, and the catalysts of packings such as manganese sand, dolomite, and coal gangue were used and their performances were compared with each other. The study indicated that the manganese sand has the characteristics of stable and effective process in comparison with several present domestic and foreign catalyzed oxidation methods.

Abstract: The relation among electronic structure, chemical bond and properties of TiC-TiB₂ composite was studied by the first principle method. The ionic interaction between the ions in the interface of the TiC-TiB₂ composite is stronger than that of the inner ions or of the related single phase. There is stronger covalent interaction between the ions in the interface of the TiC-TiB₂ composite. There are differences of densities of state (DOS) among of TiC-TiB₂ composite and related single phases as the interaction between of TiB₂ and TiC phases. The width of DOS for interface Ti 3d is obviously larger than that of corresponding TiB₂ or TiC phase, as the interaction between Ti 3d in interface and others is larger than that between Ti 3d in TiB₂ or TiC phase and others.

Abstract: TiB2-Al2O3 composite was studied by the first principle method. Ti maintains a high positive charge and O increases more charge (absolute value) in the interface, so there is strong ionic interaction among the ions in the interface of TiB2-Al2O3 composite. There is strong covalent interaction among the atoms in the interface of the TiB2-Al2O3. There are some differences of densities of state (DOS) between TiB2- Al2O3 composite and related single phases as the interaction between of TiB2 and Al2O3 phases. The width of DOS of interface Ti 3d is obviously larger than that of inner Ti, and larger than that of TiB2 single phase, which shows that the interaction among atoms in the interface is stronger than that in the center.

Abstract: The related single phases, composites of TiB2/Cu and doped with Fe or Mo series were calculated by the density function and discrete variational method (DFT-DVM) to study the relation among electronic structure, chemical bond and properties. When Fe or Mo is doped into composite, the ionic and covalent bond become stronger, and the interaction between Cu and TiB2 phases also becomes stronger. The influence of doping Mo is more obvious than that of doping Fe. The results are consistent with the experiment that additives of Mo and Fe can improve preparation of TiB2/Cu composite, and effect of additive of Mo is more obvious than that of Fe.

Abstract: Processes of atomic carbon formation can be initiated the most different energy sources – from strong shock waves to electric field of univalent ion. In the system, consisting of atomic carbon, there are fluctuations of energy and density, which result in the spontaneous origin of new solid phases.

Abstract: Shrinking the size of a solid down to nanometer scale is indeed fascinating, which makes all the otherwise constant physical quantities to be tunable such as the Young’s modulus, dielectric constant, melting point, etc. The variation of size also generates novel properties that can hardly be seen in the bulk such as the conductor-insulator and nonmagnetic-magnetic transition of noble metals at the nanoscale. Although the physics of materials at the nanoscale has been extensively investigated, the laws governing the energetic and dynamic behavior of electrons at such a scale and their consequences on the tunable physical properties of nanostructures have not been well understood [C. Q. Sun, Prog Solid State Chem 35, 1-159 (2007); Prog Mater Sci 54, 179-307 (2009)]. The objective of the contribution is to update the recent progress in dealing with the coordination-resolved energetic and dynamic behavior of bonds in the low-dimensional systems with consideration of the joint effect of temperature and pressure. It is shown that the broken-bond-induced local strain and the associated charge and energy quantum trapping at the defect sites perturbs the atomic cohesive energy, electroaffinity, the Hamiltonian and the associated properties of entities ranging from point defects, surfaces, nanocavities and nanostructures. Application of the theories to observations has led to consistent understanding of the behavior of nanometer-sized materials and the interdependence of these entities as well as the means of determining the bond energy through the temperature-dependent measurements.