Bone growth around silicon nitride implants - An evaluation by scanning electron microscopy

Silicon nitride has demonstrated to be a potential candidate for clinical applications because it is a non-cytotoxic material and has satisfactory fracture toughness, high wear resistance and low friction coefficient. In this paper, samples of silicon nitride, which were kept into rabbits` tibias for 8 weeks, and the adjacentbone tissue were analysed by scanning electron microscopy in order to verify the bone growth around the implants and the interaction between the implant and the bone. Bone growth occurred mainly in the cortical areas, although it has been observed that the newly bone tends to grow toward the marrow cavity. Differences were observed between the implants installed into distal and proximal regions. In the first region, where the distance between the implant and the cortical bone is greater than in the proximal region, the osteoconduction process was evidenced by the presence of a bridge bone formation toward the implant surface. The results showed that silicon nitride can be used as biomaterial since the newly bone grew around the implants. (c) 2007 Elsevier Inc. All rights reserved.

Tissue response around silicon nitride implants in rabbits

The chemical and dimensional stability associated with suitable fracture toughness and propitious tribological characteristics make silicon nitride-based ceramics potential candidates for biomedical applications, mainly as orthopedic implants. Considering this combination of properties, silicon nitride components were investigated in relation to their biocompatibility. For this study, two cylindrical implants were installed in each tibia of five rabbits and were kept in the animals for 8 weeks. During the healing time, tissue tracers were administrated in the animals so as to evaluate the bone growth around the implants. Eight weeks after the surgery, the animals were euthanized and histological analyses were performed. No adverse reactions were observed close to the implant. The osteogenesis process occurred during the entire period defined by the tracers. However, this process occurred more intensely 4 weeks after the surgery. In addition, the histological analyses showed that bone growth occurred preferentially in the cortical areas. Different kinds of tissue were identified on the implant surface, characterized by lamellar bone tissue containing osteocytes and osteons, by a noncalcified matrix containing osteoblasts, or by the presence of collagen III, which may change to collagen I or remain as a fibrous tissue. The results demonstrated that silicon nitride obtained according to the procedure proposed in this research is a biocompatible material. (c) 2007 Wiley Periodicals, Inc.

Chemical bonding and composition of silicon nitride films prepared by inductively coupled plasma chemical vapor deposition

Thin silicon nitride films were prepared at 350 degrees C by inductively coupled plasma chemical vapor deposition on Si(100) substrates under different NH(3)/SiH(4) or N(2)/SiH(4) gas mixture. The chemical composition and bonding structure of the deposited films were investigated as a function of the process parameters, such as the gas flow ratio NH(3)/SiH(4) or N(2)/SiH(4) and the RF power, using X-ray photoelectron spectroscopy (XPS). The gas flow ratio was 1.4, 4.3, 7.2 or 9.5 and the RF power, 50 or 100 W. Decomposition results of Si 2p XPS spectra indicated the presence of bulk Si, under-stoichiometric nitride, stoichiometric nitride Si(3)N(4), oxynitride SiN(x)O(y), and stoichiometric oxide SiO(2), and the amounts of these compounds were strongly influenced by the two process parameters. These results were consistent with those obtained from N 1s XPS spectra. The chemical composition ratio N/Si in the film increased with increasing the gas flow ratio until the gas flow ratio reached 4.3, reflecting the high reactivity of nitrogen, and stayed almost constant for further increase in gas flow ratio, the excess nitrogen being rejected from the growing film. A considerable and unexpected incorporation of contaminant oxygen and carbon into the depositing film was observed and attributed to their high chemical reactivity. (C) 2010 Elsevier B.V. All rights reserved.

X-ray photoelectron spectroscopy analysis of zirconium nitride-like films prepared on Si(100) substrates by ion beam assisted deposition

Thin zirconium nitride films were prepared on Si(l 00) substrates at room temperature by ion beam assisted deposition with a 2 keV nitrogen ion beam. Arrival rate ratios ARR(N/Zr) used were 0.19, 0.39, 0.92, and 1.86. The chemical composition and bonding structure of the films were analyzed with X-ray photoelectron spectroscopy (XPS). Deconvolution results for Zr 3d, Zr 3p(3/2), N 1s, O 1s, and C 1s XPS spectra indicated self-consistently the presence of metal Zr-0, nitride ZrN, oxide ZrO2, oxymnide Zr2N2O, and carbide ZrC phases, and the amounts of these compounds were influenced by ARR(N/Zr). The chemical composition ratio N/Zr in the film increased with increasing ARR(N/Zr) until ARR(N/Zr) reached 0.92, reflecting the high reactivity of nitrogen in the ion beam, and stayed almost constant for ARR(N/Zr) >= 1, the excess nitrogen being rejected from the growing film. A considerable incorporation of contaminant oxygen and carbon into the depositing film was attributed to the getter effect of zirconium. (C) 2007 Elsevier B.V. All rights reserved.

Luminescence studies on nitride quaternary alloys double quantum wells

We present theoretical photoluminescence (PL) spectra of undoped and p-doped Al(x)In(1-xy)Ga(y)N/Al(X)In(1) (X) (Y)Ga(Y)N double quantum wells (DQWs). The calculations were performed within the k.p method by means of solving a full eight-band Kane Hamiltonian together with the Poisson equation in a plane wave representation, including exchange-correlation effects within the local density approximation. Strain effects due to the lattice mismatch are also taken into account. We show the calculated PL spectra, analyzing the blue and red-shifts in energy as one varies the spike and the well widths, as well as the acceptor doping concentration. We found a transition between a regime of isolated quantum wells and that of interacting DQWs. Since there are few studies of optical properties of quantum wells based on nitride quaternary alloys, the results reported here will provide guidelines for the interpretation of forthcoming experiments. (C) 2008 Elsevier B.V. All rights reserved.

Efficient synthesis of selenol esters from acid chlorides mediated by indium metal

This article describes an efficient and easy one-pot route for the synthesis of a wide range of selenol esters from acyl chloride with diselenides in the presence of indium metal. A variety of functional groups can be tolerated within the diorgano diselenide and the acyl chloride coupling partner. (C) 2009 Elsevier Ltd. All rights reserved.

Mild and efficient one-pot synthesis of chiral beta-chalcogen amides via 2-oxazoline ring-opening reaction mediated by indium metal

A simple and efficient procedure for the synthesis of beta-seleno and beta-thio amides via the ring-opening reaction of chiral 2-oxazolines in the presence of indium metal has been developed. Features of this method include the following: (i) easily and accessible starting materials; (ii) indium metal is more stable and less expensive then its respective salts; (iii) useful to excellent yields of beta-chalcogen amides derivatives. (C) 2008 Elsevier B. V. All rights reserved.