Narrow Results

Antimony-platinum bilayers were prepared on titanium substrates by the two-step electrodeposition in the usual baths, and then surface alloys were formed by the atom diffusion in the solid phase. The simple antimony layer was little influenced by the substrate in both the measurements of X-ray diffraction and the i - E characteristic in a sulfuric acid solution. Regarding the bilayers, the catalytic activity in hydrogen evolution reaction was very sensitive to the presence of platinum, while the hydrogen adsorbability was quite insensitive. An interaction between antimony and platinum was confirmed by the appearance of a new dissolution wave in the electrochemical measurement and the occurrence of a new diffraction in the X-ray diffraction pattern after the heat-treatment of about 400°C. Although the new diffraction disagreed with any of the reported alloys, clear diffraction pattern of PtSb₂ alloy was observed, when the bilayers were heat-treated at about 600°C for one hour. Considering the penetration depth of X-ray, the alloying of antimony and platinum seems to occur also at low temperatures at least at the top surface.

Pure and antimony doped barium titanate powders were prepared by polymeric precursors method through Pechini process, which was carried out as a three-stage process from organometallic complex. Obtained powder was pressed into pellets and sintering was performed at 1300 °C for 8 h with heating rate of 10 °C min-1. The formation of phase and crystal structure of pure and Sb-doped barium titanate was approved by XRD analysis, Raman and IR spectroscopy. The influence of Sb doping on microstructure of barium titanate ceramics was investigated by scanning electron microscopy. Therefore, the relation between grain size, structure and properties of the obtained ceramics was analyzed. Influence of Sb doping on barium titanate properties was discussed.

We present the first results concerning the atomic structure and morphology of ultrathin Sb layers deposited on the Ni(111) face in ultrahigh vacuum at the substrate temperature ranging from 150 to 700 K obtained with the use of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and directional elastic peak electron spectroscopy (DEPES). The AES results indicate that the antimony layer on the Ni(111) at T < 200 K grows in the Frank–van der Merwe mode. For temperature around 250 K, the flat two atomic layer islands ("wedding cakes") seem to grow after completion of the first antimony monolayer. At T ≥ 300 K, a Sb–Ni surface alloy is formed. DEPES measurements indicate that the atomic structure of Sb layers deposited at T = 150 K is completely amorphous, while better and better pronounced maxima appear in DEPES profiles when the sample temperature increases from 300 to 450 K. LEED patterns corresponding to p(1 × 1), p(2 × 2) and structures have been observed for 150 K ≤ T ≤ 250 K. A possible model for the last structure is proposed. After annealing the deposited layer at T > 500K, the structure appears.

The atomic structure of ultrathin lead and antimony layers deposited on the Ni(111) face in ultrahigh vacuum at a substrate temperature ranging from 150 to 900 K was investigated with the use of low-energy electron diffraction (LEED). LEED patterns corresponding to p(1×1), p(3×3), p(4×4), structures and p(1×1), p(2×2), , structures for the adsorption of Pb and Sb, respectively, on the Ni(111) face were observed. Experimental LEED intensity-versus-energy [I(V)] spectra have been collected for the clean Ni(111) and for the , , structures. The I(V) curves obtained for the clean Ni(111) structure are in good agreement with experimental spectra from the literature.

Growth of Ge, Al and Sb on highly oriented pyrolytic graphite (HOPG) was systematically investigated using in situ scanning tunneling microscopy (STM). At room temperature (RT), three dimensional (3D) clusters of all three elements nucleate and grow at the step edges and defect sites of HOPG. The clusters of Al and Ge form chains, while Sb islands are mostly isolated. With further deposition at RT, Al clusters grow and coarsen into faceted islands with craters on the top (111) facets, whereas ramified single- and double-layer cluster islands are observed for Ge. When deposited or annealed at T ≥ 175°C, Ge forms crystallites but with randomly oriented facets. As spherical Sb islands grow beyond certain size, (111) facets appear on the top. Additionally, crystalline 2D films and 1D nanorods are observed for Sb deposited at RT. At T ≈ 100°C and higher flux, only the 2D and 1D Sb islands are formed. These different growth behaviors reflect the unique nature in which the atoms (molecules), clusters and crystallites of each element interact with HOPG surface and with each other.

Germanium was deposited onto highly oriented pyrolytic graphite (HOPG) with and without antimony in ultra-high vacuum. The surface morphology was analyzed using in situ scanning tunneling microscopy (STM) at room temperature (RT). The film grows exclusively in 3D island mode and was affected significantly by substrate defects. At initial stage, nucleation of cluster occurred at step edges and defect sites. Later, we found various types of Ge nanostructures on HOPG in different deposition conditions and stages, including cluster chains, cluster islands, nanowires, and double layer ramified islands at RT. Compact Ge islands were observed when depositing at a substrate temperature of 450 K or after an annealing at 600 K following RT deposition. In addition, the pre-deposited Sb on graphite enhances the sticking probability and suppresses the surface diffusion of Ge atoms, resulting in a significant increase in Ge cluster island density on HOPG terraces.

The aim of our investigation is focused on studying the effect of dopant dose loss during annealing treatments on heavily doped surface layers, obtained by recoil implantation of antimony in silicon. We are interested particularly by the increase of sheet resistance consequently to the shallow junctions obtained at the surface of substrate and the contribution of the dopant dose loss phenomenon following the high concentration of impurities at the surface. In this work, we report some quantitative data concerning the dopant loss at the surface of silicon implanted and its dependence with annealing treatments. Electrical measurements associated with Rutherford backscattering (RBS) technical analysis showed interesting values of sheet resistance compared with classical ion implantation and despite dopant dose loss phenomenon.

Lithium-ion batteries (LIBs) have become commercialized technologies for the modern and future world, but commercial batteries using graphite still have a low specific capacity and are concerned with safety issues. Silicon (Si) and antimony (Sb) nanocomposites have the tendency to be synthesized as high-energy-density anode materials which can be a solution for the above-mentioned problems. This work reported the synthesis methods and characterization of Sb and Si composited with nitrogen-doped graphene (SbSi/NrGO) by facile chemical method and thermal treatment. Si was obtained by magnesiothermic reduction of SiO₂ derived from rice husk, waste from the agricultural process. To study the phases, particle distributions, and morphologies, all prepared composites were characterized. In this experiment, the phase compositions were confirmed as $c$-Si, $t$-Si, SiC, Sb, and shifted peaks of expanded C which were caused by NrGO synthesis. Interestingly, a good distribution of Si and Sb particles on the NrGO surface was obtained in 15Sb15Si/NrGO composition. It could be due to appropriate Sb and Si contents on the NrGO surface area in composite materials. Morphological identification of synthesized products represented the Sb and Si particles in nanoscale dispersed on thin wrinkled-paper NrGO. These results suggested that the synthesis method in this paper is appropriate to prepare SbSi/NrGO nanocomposites to be used as high-performance anode materials in high-performance LIBs for advanced applications.

Recent advances in the chemistry of main group porphyrin complexes are surveyed. New, unprecedented structural types for porphyrin complexes which have been revealed from the recent reports of boron and tellurium porphyrins are described. Advances in the preparation and reactivity of Group 14 (silicon and tin) and Group 15 porphyrin complexes are discussed. A systematic variation in the out-of-plane distortion (ruffling) of light element Group 14 and 15 porphyrin complexes has become apparent now that a significant number of structurally characterized examples are at hand.

New routes to the formation of macrocyclic molecules are of high interest to the supramolecular chemistry community and the chemistry community at large. Here we describe the incorporation of heterocyclic core units into discrete macrocycles via the utilization of a pnictogen-assisted self-assembly technique. This method allows for the rapid and efficient formation of discreet macrocyclic units from simple dithiol precursors in high yields with good control over macrocycle size. Up to this point, this technique has been reported on primarily benzylic thiol systems with very little incorporation of endohedral heteroatoms in the resulting assemblies. This study demonstrates the effective incorporation of heterocyclic core molecules allowing for the formation of a more functional cavity, resulting in the formation and crystallization of novel furan- and thiophene-based disulfide dimer and trimer macrocycles, respectively, that are isolated from a range of other larger discrete macrocycles that assemble as well. These disulfide macrocycles can be trapped as their more kinetically stable thioether congeners upon sulfur extrusion.

Effects of bismuth and antimony additions on the microstructure and mechanical properties of Mg-9Al-0.8Zn-0.2Mn (AZ91) alloy have investigated. The results indicated that small amount of bismuth or antimony additions to the alloy of AZ91 results in significant increases in yield strength and creep resistance but slight decreases of ductility at elevated temperatures up to 200 °C. The highest creep resistance has been obtained from the alloy with combined additions of bismuth and antimony. Microstructural observations reveal that the additions of bismuth or antimony have the effect on refining the β (Mg₁₇Al₁₂) precipitates in the as-cast alloys and suppressing discontinuous precipitation of the β phase effectively during aging process. Some needle-shaped Mg₃Bi₂ or Mg₃Sb₂ particles distributed mainly at grain boundaries have been observed in the alloys with bismuth or antimony additions. Both of Mg₃Bi₂ and Mg₃Sb₂ have high thermal stability at elevated temperatures and play important roles of improving creep resistance of the alloys at elevated temperatures.