Pleiades Publishing Ltd

Một phương pháp tổng hợp vi sóng cho các vật liệu nano từ tính đa chức năng với cấu trúc “lõi - vỏ đa lớp” được đề xuất. Các điều kiện tối ưu cho quá trình tổng hợp từng bước một vật liệu dựa trên magnetit Fe3O4 (“lõi”) được sửa đổi bằng các polyme chứa silicon (TEOS + MPTMS), các hạt nano vàng và thuốc chống ung thư doxorubicine (DOX) (“vỏ”) đã được tìm ra. Sử dụng các kỹ thuật thiết bị, thành phần của các vật liệu nano đã chuẩn bị (Fe3O4@TEOS/MPTMS@Aucoll@DOX) được nghiên cứu và kích thước của các hạt được tổng hợp ở các nhiệt độ và tỉ lệ thuốc thử khác nhau được xác định. Các quá trình hấp thụ liên quan đến DOX và các vật liệu nano được tổng hợp được nghiên cứu ở các thời gian tiếp xúc pha khác nhau, nồng độ doxorubicine và pH của môi trường. Khả năng phóng thích có kiểm soát DOX từ bề mặt hạt nano khi thay đổi giá trị pH được chứng minh. Các hạt nano lai đã tổng hợp có thể là triển vọng cho nhiều ứng dụng y sinh, đặc biệt là cho việc vận chuyển thuốc mục tiêu và nhiệt trị liệu cục bộ.

A nanodimensional powder of doped boron carbide has been obtained by means of mechanoactivation in a planetary centrifugal mill and used to produce a nanostructural ceramic material by hot pressing at a temperature of 1900°C and a pressure of 30 MPa. Investigation of a combination of mechanical properties of the nanostructural ceramics showed its advantage over a material obtained using the traditional ceramic technology from the same (micron-sized) initial boron carbide powder. A ballistic armor structure containing the new nanostructural ceramics possesses improved protective properties, which have been confirmed by shooting tests. The introduction of a front layer of the nanostructural ceramics into a test armor structure significantly increased its bullet resistance as compared to that of an analogous structure with a ceramics manufactured using the traditional technology.

Mechanisms of sintering and the structure and mechanical properties of nano- and ultradispersed W-Ni-Fe (WNF) and W-Ni-Fe-Co (WNFC) heavy tungsten alloys are investigated. The effect of tungsten particle sizes on the optimal sintering temperature is studied. The size of particles has been changed by the mechanical activation (MA) of the source W-Ni-Fe coarse-grained (CG) charge and by adding ultradispersed particles obtained using plasmochemical synthesis. Nanodispersed powders and ultradispersed powders (UDPs) have been sintered using the techniques of free sintering and pulse plasma sintering (PPS). It has been revealed that the dependence of the alloy density on heating temperature is nonmonotonic, with the maximum corresponding to the optimum sintering temperature. It has been shown that an increase in the time of MA and acceleration of grinding bodies in the process of MA accompanied by a decrease in the size of alloy particles and formation of nonequilibrium solid solutions lead to a reduction in the optimal sintering temperature. It has been shown that, using planetary high-energy milling methods and high-rate spark plasma sintering, it is possible to obtain ultrastrong tungsten alloys whose mechanical properties (macroelasticity stress and yield stress) substantially exceed analogous properties of commercial alloys.

A novel calorimetry system is presented to use in radiation processing facilities equipped with an electron accelerator. The calorimeter core was fabricated with polystyrene/multiwall carbon nanotube nanocomposite. The nanocomposite samples were made in different weight percentages of MWCNTs namely 0.05, 0.1, 0.28, 1, and 2 wt %. The SEM analysis was applied to demonstrate the dispersion state of the inclusions into the polymer matrix. The electrical percolation threshold was investigated and achieved at about 0.1 wt % of the inclusion. The electrical resistance of the samples was objected as the calorimeter response before and after the electron beam irradiation. A linear response of the resistance-dose curve was observed for all the nanocomposites having the 0.1 and 0.28 wt % of the inclusion at a dose range of ~8 to ~40 kGy. The results showed that the decrease of the MWCNT content leads to increasing the electrical resistance. Furthermore, the thicker sample showed better experimental results in comparison to the thinners. The best results were obtained for the nanocomposite sample containing 0.14 wt % of MWCNT and 5 mm of sample thickness.

The possibility of phase transition of the first kind in a system of free single-domain magnetic clusters is considered. To determine the domain of the system parameters where the phase transtion of the first kind (the domain of stability loss of the homogeneous distribution of the system) is possible, an equation of state of a system consisting of solid spheres of the diameter d containing the point dipole with the moment μ is constructed. It is shown that, taking into account the dipole-dipole interactions, given with accuracy up to the quadratic term in the expansion with respect to (1/kT) in the expression for the second virial coefficient, the equation of state of the system is the Berthelot equation. The value of the critical temperature and the condition under which the phase transition of the first kind (the coexistence of the liquid and gas phases) is possible in the system are determined as functions of the system parameters: the size of the clusters, their dipole moment, and the temperature of the system.

In this paper, we have studied the effect of water-soluble surfactants (C2H5OH and C12H25NaO4S) on the processes of iron hydroxide precipitation and reduction and have showed the possibility of controlling the dispersity of the initial hydroxides and the reduced nanocrystalline metal particles and their size distributions upon the production by chemicometallurgical method.

A hierarchic set of gradually complicated models is suggested. The models describe the contact condition of the mechanical interaction between the atomic force microscope (AFM) probe and the investigated surface while allowing for various factors. A variant of the AFM probe-surface mechanical interaction model is developed which takes into account the simultaneous effect of the probe geometry and the elastic deformations of the AFM cantilever that take place when there is a small or moderate curvature of surfaces under study. A variant of the model of interaction between the AFM probe and the surface of the investigated specimen is discussed, taking into consideration the simultaneous effect of the probe geometry and elastic deformations of the AFM cantilever and the probe contact with the surface under study within the framework of Derjaguin-Muller-Toropov model. Algorithms to determine the AFM probe position are created to optimize computations.

A method for determining local thicknesses and parameters of the electronic structure of thin oxide films, as well as of absolute values of the distance between the tip of the scanning tunneling microscope and the surface of the sample under study, are presented in this work.