Polymer surface deformation under semicontact-mode AFM scanning

An experiment and a computer simulation are presented concerning the tip-induced deformation of polyethylene under semicontact-mode AFM scanning. The dependence is investigated of the deformation on normalized amplitude of scanning with due regard to cantilever damping. The measured and the simulated deformation curve are found to agree for sufficiently large normalized scanning amplitudes. Otherwise, the experiment and the simulation diverge. Reasons for this disagreement are suggested within the context of different physical processes influencing the deformation.     

Improving proton conductivity and ionic selectivity of porous polyolefin membranes by chitosan deposition

The paper presents a new method for modifying polyolefin membranes using chitosan deposition in order to apply them as a separator in the redox flow batteries with an aqueous electrolyte. Chitosan is deposited from an aqueous carbonic acid under high pressure of saturating carbon dioxide, which allows to increase the affinity of the composite membrane to aqueous electrolyte and, as a consequence, to increase the proton conductivity. In addition, the deposition of a chitosan film makes it possible to reduce the pore size, which means an increase in the ionic selectivity of the porous membrane. In the article, membranes modified with chitosan for different times were obtained. It was shown that as a result of the proposed treatment, the ionic selectivity of membranes increases from 0.2·10⁷ ms·min/cm³ to 5·10⁷ ms·min/cm³.     

Platinum cross-linked chitosan hydrogels synthesized in water saturated with CO2 under high pressure

The creation of biocompatible composite hydrogels from renewable biopolymers with stabilized functional platinum nanoparticles seems to be an important scientific task. The formation of such hydrogels in a unique medium of carbonic acid under high pressure CO₂ is promising due to its sterilizing ability under pressure, biocompatibility after decompression and environmental friendliness. In the present work, stable chitosan hydrogels with platinum nanoparticles were obtained in such solutions. The hydrogel nature of the composites was confirmed by rotational rheology. The physicochemical characteristics were studied using Fourier transform infrared, X-ray photoelectron, ultraviolet–visible spectroscopies, transmission electron, scanning electron and atomic force microscopies. It was found that nanoparticles of oxidized Pt of approximately 4.5 nm in size are stabilized by chitosan in the composite. The resulting chitosan/Pt hydrogels were also tested for antimicrobial activity and shown strong activity against Gram-positive bacteria (B. subtilis and B. coagulans) and slight activity against E. coli.     

Technology of welding of products made of steel 15Kh5M with control of thermal cycles

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 9, pp. 31–34, September, 1993.     

Radial Distribution of the Temperature in a Well

Journal of Engineering Physics and Thermophysics - A theoretical investigation of the radial temperature distributions in the upward and downward flows of fluid in the borehole of a production well...     

Scanning tunneling microscope—A nanoelectronic measuring instrument

The advantages of using the scanning tunneling microscope for accurate measurements when solving problems in nanotechnology are considered. The results of noise measurements made using the scanning tunneling microscope are presented and it is shown that the fundamental limination on the spatial resolution along the normal to the surface of the sample being investigated is due to low-frequency fluctuations of the tunnel current. The limit sensitivity of the microscope is determined. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 58–61, April, 1998.     

Measuring the quantum efficiency of multielement photodetectors in the spectral range between 180 and 800 nm

An automatic system for measuring the quantum efficiency of multielement photodetectors applied in atomic emission spectral analysis is created. Results of measuring the quantum efficiency of BLPP-369 photodiode lines with different dopants and coating layers, and also lines of CCDs (Sony ILX-526A) are presented. It is shown that the quantum efficiency of photodiode lines between 180 and 360 nm is 0.3–0.5, which is 2–5 times greater than for ILX-526A CCDs with phosphor. The spread of quantum efficiency values of photodiodes in one BLPP-369 line is no more than 10%, and about 30% for lines from different batches.