We report low- and high-temperature Raman spectroscopy of pressure-induced amorphous boron carbide (a-B4C). Coarsening of carbon clusters in a-B4C was characterized during heating, whereas unusual temperature coefficients of a-B4C Raman peak shifts were observed during cooling. These results experimentally evidence that the amorphization of B4C is associated with the destruction of the C–B–C chains and a-B4C is composed of sp2 carbon aromatic rings and boron clusters. This disordered structure with relatively weak carbon sp2 bonds is believed to be responsible for the loss of B4C shear strength at high pressures.

It has been proposed that the essential requirement for artificial materials to bond to living bone is the formation of bonelike apatite on their surfaces in the body. Recent studies have shown that titanium hydrogel and silica gel induce apatite formation on their surface in a simulated body fluid. In this study, the influence of titanium oxide and titanium silicate on the bonding of titanium alloys to bone was studied. Rectangular implants (15 x 10 x 2.2 mm) of titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were implanted into the tibial metaphyses of mature rabbits. At 8 and 24 weeks after implantation, the tibiae containing the implants were dissected out and subjected to a detaching testing. The failure load for titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were, respectively, 0.68 +/- 0.48, 0.22 +/- 0.46, 0.67 +/- 0.59, 2.18 +/- 0.71 and 2.03 +/- 0.41 kgf at 8 weeks, and 2.7 +/- 0.91, 2.58 +/- 1.29, 2.38 +/- 0.41, 3.79 +/- 1.7, and 2.79 +/- 0.87 kgf at 24 weeks after implantation. Histological examination by Giemsa surface staining, CMR, and SEM-EPMA revealed the coated titanium alloy implants directly bonded to bone tissue during early implantation. A Ca-P layer was observed at the interface of the coated implants and the bone. The results of this study indicated that TiO2 and Ti5Si3 can enhance the early bonding of titanium alloys to bone by inducing a Ca-P layer (chemical apatite) on the surface of titanium alloys. It also is suggested that the direct bone contact occurs in relation to the calcium and phosphorus adsorption onto the surface of the titanium passive layer formed during long-term implantation.

Apatite--wollastonite-containing glass--ceramic (A--W . GC) has a strong ability to bond to bone and relatively high mechanical strength. Therefore, as a bulk material it has recently been applied clinically even in load-bearing sites. In this study, we modified A--W . GC by altering its composition ratio with the removal of CaF 2 and the addition of B 2O 3, and examined the potential use of the resulting new glass--ceramic as a material for coating on a titanium (Ti) alloy. The bioactivity of this new coating (NC) material and its bonding ability to bone were investigated mechanically and histologically. After implantation of the Ti alloy plate coated with this material into the tibiae of rabbits for 2, 3, 4, 8, and 25 weeks, a detaching test was performed. The detaching failure load of the NC plates was compared with those of A--W . GC plates, hydroxyapatite (HA) plates, and uncoated Ti alloy plates implanted in the same way. The failure load of NC was as high as that of A--W . GC for all periods, whereas it was significantly higher at 3 and 4 weeks than that of HA. Uncoated Ti alloy showed lower failure loads for all periods, differing significantly from the other materials. There was no breakage or detachment of the coating layer observed after the detaching test. Histological examinations by CMR, Giemsa surface staining, and SEM-EPMA showed that NC bonded directly to bone without any intervening soft tissue layer. A calcium--phosphorus-rich layer (apatite layer) was observed within the coating layer, as is the case in A--W . GC. These results indicate that this new glass--ceramic has earlier bone-bonding ability and high mechanical strength, making it a promising coating material.

Deep-submicron trench profile control using a magnetron enhanced reactive ion etching system for shallow trench isolation Effect of plasma polymerization film on reducing damage of reactive ion etched silicon substrates with CHF3+O2 plasmas J.The surface of polycrystalline diamond films during reactive ion etching in electron cyclotron resonance SF 6 and O 2 plasmas has been examined by scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. A SF 6 plasma required a high voltage in negative substrate biasing in order to achieve an equivalent etching rate to an O 2 plasma. This was ascribed to the codeposition effects and the low mean energy of ions upon impact in a SF 6 plasma. The elemental composition of the amorphous layer formed at the etched film surface in the two plasmas was almost equivalent and mainly composed of carbon and oxygen, except a low concentration (р1%͒ of sulfur and fluorine in the case of a SF 6 plasma. The significant codeposition on diamond surface was the most likely the result of plasma-wall interactions induced by the fragments from SF 6 , and highly responsible for suppressing the ratio of lateral to vertical etching rate leading to anisotropic etching in a SF 6 plasma, in contrast with the little or no codeposition leading to isotropic etching in an O 2 plasma. The results give the substantial implications for the etching process in practical SF 6 /O 2 plasmas utilized in device fabrication.

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