The preparation of a phosphorus doped silicon film from phosphorus containing silicon nanoparticles

Phosphorus containing and octyl-terminated silicon nanoparticles (NPs) are generated by a solution reduction route under room temperature conditions for the first time and characterized by TEM, HRTEM, EDX, 1H/13C/31P NMR, EPR, and PL spectroscopy, then annealed to form a thin film with phosphorus doping confirmed by microprobe elemental analyses.     

Thermal air-oxidized coating on Yb14−xRExMnSb11 ceramics

Journal of Thermal Analysis and Calorimetry - A high sublimation rate of Yb14MnSb11 as a promising thermoelectric material at working temperatures is a critical factor for its space power...     

Functionalization of Silicon Nanoparticles via Silanization: Alkyl, Halide and Ester

The feasibility of using silanization as a general tool to functionalize the surface of silicon nanoparticles (NPs) has been investigated in detail. Silicon NPs were prepared from reduction of silicon tetrachloride with sodium naphthalide. The terminal chloride on the surface of as-synthesized particles was substituted by methanol and water, in sequence. The particles were then silanized by octyltrichlorosilane, 11-bromoundecyltrichlorosilane, or 2-(carbomethoxy)ethyltrichlorosilane. These treatments yielded alkyl-, bromo-, or ester-termini on NP surfaces, respectively. The NPs were characterized by TEM, NMR, FTIR, UV–Vis, and PL spectroscopy. Changes of termination groups brought various functionalities to the NPs, without loss of the photophysics of the original NPs.     

Hydrogen encapsulation in a silicon clathrate type I structure: Na5.5(H2)2.15Si46: synthesis and characterization

A hydrogen-encapsulated inorganic clathrate, which is stable at ambient temperature and pressure, has been prepared in high yield. Na5.5(H2)2.15Si46 is a sodium-deficient, hydrogen-encapsulated, type I silicon clathrate. It was prepared by the reaction between NaSi and NH4Br under dynamic vacuum at 300 degrees C. The Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. The type I clathrate structure has two types of cages where the guest species, in this case Na and H2, can reside: a large cage composed of 24 Si, in which the guest resides in the 6d crystallographic position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position. Solid-state 23Na, 1H, and 29Si MAS NMR confirmed the presence of both sodium and hydrogen in the clathrate cages. 23Na NMR shows that sodium completely fills the small cage and is deficient in the larger cage. The 1H NMR spectrum shows a pattern consistent with mobile hydrogen in the large cage. 29Si NMR spectrum is consistent with phase pure type I clathrate framework. Elemental analysis is consistent with the stoichiometry Na5.5(H2.15)2Si46. The sodium occupancy was also examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The high-angle annular dark-field (HAADF) STEM experimental and simulated images indicated that the Na occupancy of the large cage, 6d sites, is less than 2/3, consistent with the NMR and elemental analysis.     

Room temperature synthesis of surface-functionalised boron nanoparticles

Capped boron nanoparticles have been synthesized at room temperature by a simple route that does not involve the use of flammable boranes.     

Flux growth and structure of two compounds with the EuIn2P2 structure type,AIn2P2 (A = Ca and Sr), and a new structure type,BaIn2P2

Single crystals of the new Zintl phases AIn₂P₂ [A = Ca (calcium indium phosphide), Sr (strontium indium phosphide) and Ba (barium indium phosphide)] have been synthesized from a reactive indium flux. CaIn₂P₂ and SrIn₂P₂ are isostructural with EuIn₂P₂ and crystallize in the space group P6₃/mmc. The alkaline earth cations A are located at a site with m symmetry; In and P are located at sites with 3m symmetry. The structure type consists of layers of A²⁺ cations separated by [In₂P₂]²⁻ anions that contain [In₂P₆] eclipsed ethane‐like units that are further connected by shared P atoms. This yields a double layer of six‐membered rings in which the In—In bonds are parallel to the c axis and to one another. BaIn₂P₂ crystallizes in a new structure type in the space group P2₁/m with Z = 4, with all atoms residing on sites of mirror symmetry. The structure contains layers of Ba²⁺ cations separated by [In₂P₂]²⁻ layers of staggered [In₂P₆] units that form a mixture of four‐, five‐ and six‐membered rings. As a consequence of this more complicated layered structure, both the steric and electronic requirements of the large Ba²⁺ cation are met.     

Low-temperature solution route to macroscopic amounts of hydrogen terminated silicon nanoparticles

A new solution route for preparing gram-scale, hydrogen terminated silicon nanoparticles is presented. Dimethoxyethane and diocytl ether have been used to prepare silicon nanoparticles via a solution reaction between sodium silicide and ammonium bromide. The reaction products are isolated as a clear yellow-orange solution and a dark black powder. Both the solution and the powder have been characterized.     

Structure and thermoelectric characterization of Ba8Al14Si31

A molten Al flux method was used to grow single crystals of the type I clathrate compound Ba8Al14Si31. Single-crystal neutron diffraction data for Ba8Al14Si31 were collected at room temperature using the SCD instrument at the Intense Pulsed Neutron Source, Argonne National Laboratory. Single-crystal neutron diffraction of Ba8Al14Si31 confirms that the Al partially occupies all of the framework sites (R1 = 0.0435, wR2 = 0.0687). Stoichiometry was determined by electron microprobe analysis, density measurements, and neutron diffraction analysis. Solid-state (27)Al NMR provides additional evidence for site preferences within the framework. This phase is best described as a framework-deficient solid solution Ba8Al14Si31, with the general formula, Ba(8)Al(x)Si(42-3/4x)[](4-1/4x) ([] indicates lattice defects). DSC measurements and powder X-ray diffraction data indicate that this is a congruently melting phase at 1416 K. Temperature-dependent resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers.