A Novel Procedure to Obtain Nanocrystalline Diamond/Porous Silicon Composite by Chemical Vapor Deposition/Infiltration Processes

Abstract

Nanocrystalline diamond (NCD) films were formed on porous silicon (PS) substrate by Chemical Vapor Deposition/Infiltration (CVD/CVI) process using a hot filament reactor. This innovative procedure is determinant to grow a controlled three-dimensional diamond structure with diamond grains formation in the pores, covering uniformly the different growth planes. In this CVI process, a piece of reticulated vitreous carbon (RVC) was used, under de PS substrate, as an additional solid source of hydrocarbon that ensures the production of pertinent carbon growth species directly on PS and into its pores. PS substrates were obtained by anodization etching process of n-type silicon wafer in a hydrofluoric acid (HF) solution containing acetonitrile (CH3CN) which result in an uniform and well controlled porous distribution and size when compared with the usual ethanol solution. Depositions were performed using Ar-H2-CH4 where the methane concentration varied from 0 up to 1.0 vol%, to analyze the influence of RVC use as an additional carbon source on growth mechanism. Scanning Electron Microscopy (SEM) and Field Emission Gun (FEG) were used to investigate PS and NCD film morphology. SEM images of NCD showed faceted nanograins with average size from 5 to 16 nm and uniform surface texture covering all the supports among the pores resulting in an apparent micro honeycomb structure. Raman spectra confirmed the existence of sp2-bonded carbon at the grain boundaries. The spectra showed a peak that may be deconvoluted in two components at 1332 cm(-1) (diamond) and 1345 cm(-1) (D band). Two shoulders at 1150 and 1490 cm(-1) also appear and are assigned to transpolyacetylene (TPA) segments at the grain boundaries of NCD surfaces. In addition, X-ray diffraction analyses of all films presented characteristic diamond diffraction peaks corresponding to (111), (220) and (311).

Novel Bio-functional Magnesium Coating on Porous Ti6Al4V Orthopaedic Implants: In vitro and In vivo Study

“…The coating consisted of uniform Mg grains with size of about 1 μm. It was reported that the grain size was controlled by the deposition pressure of the total reactor42. At a low pressure (P Ar  = 10 −2  MPa) it would yield a higher nucleation rate, which resulted in a higher number of grains but of a smaller size.…”

High Surface Area Mesoporous Silicon Nanoparticles Prepared via Two-Step Magnesiothermic Reduction for Stoichiometric CO2 to CH3OH Conversion

“…Common routes to generate mp-Si include electrochemical etching, − metal-assisted chemical etching, chemical vapor deposition, , and metallothermic reduction. ,− Of these, metallothermic reduction using Mg metal offers a scalable and straightforward route to prepare mp-Si using inexpensive raw materials such as rice husks, bamboo, sand, glass, and diatoms. ,,, Magnesiothermic reduction is an exothermic redox reaction between Mg metal and SiO x . The reaction is typically performed at the melting point of Mg metal (650 °C) with temperature held constantly at this point to assist in the diffusion of the atoms in the solid state.…”

“…Common routes to generate mp-Si include electrochemical etching, 15−17 metal-assisted chemical etching, 18 chemical vapor deposition, 19,20 and metallothermic reduction. 3,21−27 Of these, metallothermic reduction using Mg metal offers a scalable and straightforward route to prepare mp-Si using inexpensive raw materials such as rice husks, bamboo, sand, glass, and diatoms.…”

Metallothermic Reduction of Silica Nanoparticles to Porous Silicon for Drug Delivery Using New and Existing Reductants

“…The utility of porous Si is highly dependent on its surface area, crystallinity, morphology, and pore volume, which are often dictated by the synthetic methods used for its preparation. Porous Si can be made by top‐down approaches such as electrochemical etching and metal‐assisted chemical etching or bottom‐up approaches such as chemical vapor deposition, carbothermal reduction, and metallothermic reduction . Among these methods, metallothermic reduction has gained significant attention as it allows for straightforward synthesis of porous Si from inexpensive precursors such as glass, sand, or sol–gel polymers .…”