We have studied large (∼6-mm diameter) single crystals of semiconducting synthetic diamonds seed—grown by the temperature-gradient method. EPR, IR spectroscopy and cathodoluminescence have been used ...to examine the defect and impurity composition of the crystals and the distribution of the electrically active impurities in the bulk crystal. Electrophysical measurements of the current–voltage characteristics and temperature dependence of electrical conductivity have been conducted. Contrast in the internal electric fields caused by inhomogeneity in the distribution of acceptor and donor centers is shown to play the decisive role in the electrical properties. Our findings point to considerable promise for the use of the temperature-gradient method to grow large semiconducting diamond single crystals (of the IIb type) with the required electrical properties as well as to the possibility to extend the application of such crystals (or their fragments) to electronics.
A mathematical model of the vibrations of a production system for the turning of blanks is presented. Results of comparative analysis of processes employed for the turning of steel-45 and caprolon ...blanks are presented. The relationship between the mean-arithmetic deviation of the profile of the machined surface of caprolon articles from the maximum values of the energy spectrum of vibration accelerations and the vibration frequencies of the production system corresponding to them during the machining of blanks is established experimentally.
A new method is described for molding epoxy resin objects. Results are provided for polymer body structural studies by scanning electron microscopy and infrared spectroscopy. Results are also ...provided for mechanical and manufacturing tests confirming the expediency and efficiency of including in the production process for manufacture of fiberglass objects combined treatment of polymer binder with nanosecond electromagnetic pulses and an electromagnetic field preceding hardening.
Morphological, structural, and nano-electrical features of the growth defects and sectoral boundaries revealed by selective etching in synthetic boron-doped single crystals of diamond (BDD) and ...multisectoral plates are characterized by a set of scanning probe microscopy (SPM) methods, confocal micro-Raman, and micro-FTIR spectroscopy. Diamond single crystals were grown under high pressure and high temperature conditions (HPHT) in the FeAlBC system. Morphology of dislocation etch pits and micro-defect related pits/protrusions compared both on the growth facets and multisectoral plates cut parallel to the {110} facet of BDD single crystals. Ex situ AFM observation of the etched surface revealed non-homogeneously distributed pits and protrusions over the growth facets correlated with irregular macroscopic growth defects. There is a center-to-periphery gradient of dislocation density in multisectoral plates. The protrusions are homogeneously distributed over plates; some often decorate dislocation pits. Micro-Raman mapping on dislocation pits (boron-rich regions) decorated by low-boron content regions revealed crystalline imperfections in three dimensions, with apparent compressive/tensile strain. The defects were mainly electrically neutral under surface potential mapping by Kelvin probe force microscopy, opposite to the inter-sectoral boundaries having pronounced surface potential steps. The scanning spreading resistance microscopy shows resistivity variations at etching-reviled surface defects and sectoral boundaries if the appropriate DC bias is applied to the SPM tip.
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•Etch pits on single crystals, and multisectoral plates of diamond are investigated.•Inter-sectoral variations of the surface potential and resistivity are characterized.•The maps of local deformation, surface potential and resistivity are correlated over etch pits.•The boron-rich pits were found to be often decorated with low-boron-doped protrusions.
Adducts of cobalt(II) bis(salicylaldiminates) and 2,4,6,8-tetra-
tert
-butylphenoxazin-1-one were synthesized and their molecular and crystal structures were determined. According to the ESR and ...magnetochemical data, the metal atom is in the low-spin trivalent state (Co
III
) due to the intramolecular electron transfer to the redox-active ligand. In the solid state, the mixedligand complexes are stable in air for several months, but in solution at elevated temperatures they dissociate to the starting components. Such a behavior detected by the temperature dependence of the effective magnetic moment is explained by the quantum chemical DFT calculations of the energy barriers of possible valence tautomeric dynamics, whose values were found to be higher than the enthalpy of dissociation.
Given the difficult social and economic situation in Russia, the lives and health of young people are getting increasingly worse, as can be seen from the data of state statistics. In this article, ...the author investigates the self-preservation aspect of the health of college students. The health of any social-demographic group has two characteristics: (1) it is usually determined statistically and characterized by a complex of social and demographic indicators; and (2) while it is objectively conditioned by social and biological factors, it is also affected by the individual's subjective attitude. Thus, the author examines objective aspects (the occurrence of chronic and other diseases, how students spend leisure time) as well as subjective factors (the frequency of visits to medical facilities, the prevalence of harmful habits), and the respondents' attitudes toward their own well-being. Results indicate that the majority of the respondents believe that the main factors determining their state of health are external, objective factors such as the conditions of life and heredity. In the author's opinion, the students do not adequately appreciate the destructive role played by subjective factors such as smoking tobacco, drinking alcohol to excess, and abusing narcotics. It is apparent that state policies designed to instill in young people an active life stance in preserving and strengthening their health will be essential. (Contains 8 notes.)
The Сd(II) complexes with redox amphoteric 2,6-di-(
tert
-butyl)-4-((2-hydroxyphenyl)imino)cyclohexa-2,5-dienone ligands L
1
and L
2
(adducts
I
,
II
, and
III
) are synthesized. The structures of ...coordinated complexes
I
,
II
, and
III
are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 1838319 (
II
) and 1838310 (
III
)) and confirmed by the
1
Н,
13
С, and
113
Cd NMR spectroscopy (for complexes
I
and
III
) and IR spectroscopy data.
New developments of application of X-ray topography in the quasi-forbidden (222) reflection from perfect crystals with diamond lattice to investigate defects are presented. The spatial distribution ...of intensities of (111) and (222) X-ray reflections is correlated with the distribution of point defects in synthetic diamonds of various types. It is shown that X-ray topography in the quasi-forbidden (222) reflection is a promising tool for investigation of weak stress fields in perfect crystals.
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•A new synthesis of redox-active bis-chelate Ru(II) complex Ru(ONO)2.•The RuIII/RuII conversion through the formation of RuIII (ONO)3 intermediate.•Ru(ONO)2 enters into ligand ...substitution only via its radical-anion form.•The structure of Ru(ONO)Py3 is X-ray established.
The redox-active bis-chelate hexacoordinate ruthenium complex 2 Ru(ONO)2 comprising two redox-active 2,4,6,8-tetrakis(tert.-butyl)-9-hydroxyphenoxazin-1-one ligands 1 was synthesized by coupling ruthenium trichloride with 1 or its thallium salt. Reduction of 2 with zinc amalgam produces its radical-anion 2a, which readily reacts with pyridine in aerobic conditions resulting in substitution of one of the tridentate hydroxyphenoxazinone ligand by three pyridine molecules and the formation of a salt of tris(pyridine)(tetra-(tert.-butyl)oxyphenoxazin-1-onate) Ru(II) cation 5. The structure of this salt was established by X-ray crystallography and its redox activity investigated using cyclic voltammetry. The mechanism of the RuIII/RuII conversion observed in this reaction was suggested based on the data of ESR, UV-Vis spectra and DFT B3LYP/6-311++G(d,p)/SDD calculations.
