Conducting boron-doped single-crystal diamond films for high pressure research

Epitaxial boron-doped diamond films were grown by microwave plasma chemical vapor deposition for application as heating elements in high pressure diamond anvil cell devices. To a mixture of hydrogen, methane and oxygen, diborane concentrations of 240–1200 parts per million were added to prepare five diamond thin-film samples. Surface morphology has been observed to change depending on the amount of diborane added to the feed gas mixture. Single-crystal diamond film with a lowest room temperature resistivity of 18 mΩ cm was fabricated and temperature variation of resistivity was studied to a low temperature of 12 K. The observed minima in resistivity values with temperature for these samples have been attributed to a change in conduction mechanism from band conduction to hopping conduction. We also present a novel fabrication methodology for monocrystalline electrically conducting channels in diamond and present preliminary heating data with a boron-doped designer diamond anvil to 620 K at ambient pressure.     

Synthesis of thiazolines and thiazolidines

Primary -ethynylamines form thiazolines with isothiocyanates, while secondary -ethynylamines give thiazolidines. Data on the IR, PMR, and UV spectra of the compounds obtained are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 471–474, April, 1972.     

A novel dual surface modification on titanium in dental use: Characterization and topography

This laboratory study aimed to compare, contrast, and evaluate the effect of a novel dual surface modification method on the adhesion strength of resin composite cement to titanium. C.p.-2 grade titanium samples were silica-coated, etched with HNO₃(69vol %) or a blend of HCl (35vol %) and H₃PO₄ (85vol %), for 1 h at 80°C. Surface roughness was measured by surface roughness profilometry, topographic analysis by scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface analyses by energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS). Silanization of all specimens was carried out after SEM, EDX, and AFM analysis, before enclosed mold microshear bond strength testing (EM-μSBS). Adhesion strengths were measured after artificial ageing: 1 day, 1 week, 4 weeks, and 8 weeks by EM-μSBS testing and failure mode analysis by optical microscopy. Polished titanium was used as a control. The highest surface roughness was observed in titanium samples treated with silica-coating + HCl-H₃PO₄ etching. The elemental composition confirmed the presence of Ti, O, C, with Si and Al in samples treated with silica-coating. A gradual decrease in EM-μSBS values was observed in all titanium samples with adhesive and cohesive failure modes. The novel dual surface modification method applied in this study suggests that silica-coating + HCl-H₃PO₄etching strongly affects titanium surface topography and roughness. The presence of Si on silica-coated surface modified titanium before silanization with an experimental silane has a positive effect on the EM-μSBS of titanium samples treated with silica-coating only or silica-coating + HNO₃ etching.     

Tautomerism of 2-arylamino- and 2-benzylaminothiazoline

It was established by means of the IR, UV, and PMR spectra that 2-arylamino-4,4-dialkyl-5-methylenethiazolines have the 2-aryliminothiazolidine structure in the crystalline state and in solutions, whereas the 2-benzylamino derivatives can exist in both the amino and imino forms.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 755–760, June, 1979.     

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

Magnetic ordering temperatures in heavy rare earth metal dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to a pressure of 69 GPa and a temperature of 10 K. Previous studies using magnetic susceptibility measurements at high pressures were able to track magnetic ordering temperature only till 7 GPa in the hexagonal close packed (hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. This is followed by a rapid increase in the magnetic ordering temperatures in the double hcp phase and finally leveling off in the distorted face centered cubic phase of Dy. Our studies reaffirm that 4f-shell remains localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.     

Ab Initio Study of the (DMF) m · (HCl) n (m,n = 0–2) Complexes

Based on the results of ab initio calculations (B3LYP, 6-31++G(d,p)), the structures and stability of the complexes DMFA · HCl, (DMF)₂ · HCl, DFF · (HCl)₂, and (DMF · HCl)₂ are compared. In the complex with a 1 : 1 composition, DMF and HCl form a hydrogen bond of the molecular type. In the heterotrimers with compositions 1 : 2 and 2 : 1, the hydrogen bond noticeably strengthens. In the tetramer (DMF · HCl)₂, the most pronounced proton transfer takes place and two quasi-symmetric hydrogen bridges O···H···Cl are formed and stabilize this complex. The results of calculations are compared with data on the structure of complexes between HCl and DMF obtained by crystal-structure XRD and vibrational spectroscopy in solutions.