Calcium deficient hydroxyapatite by precipitation: Continuous process by vortex reactor and semi-batch synthesis

Precipitation of calcium deficient hydroxyapatite nanoparticles in an environmentally benign manner by using only dilute solutions of calcium hydroxide and phosphoric acid without pH adjustment and addition of other chemicals, and water, being the only by-product was investigated by using continuous flow Vortex Reactor (VR) and Semi-Batch Reactor (SBR). The effect of hydrodynamics by changing the Reynolds number of the jets providing residence times of 8.4 ms to 4.37 s for VR, and by changing the stirrer speed between 100 rpm (Re = 2656) and 1000 rpm (Re = 26560) for SBR, on the particle size, particle size distribution, and morphology of the particles was investigated for both systems. It has been shown that it is possible to produce pure phase hydroxyapatite nanoparticles in the desired morphology by changing production system, without resorting to additives. While VR produced rod-like particles with the crystallite size around 4 nm, SBR produced spherical particles with the crystallite size of around 5 nm.     

Mixing of nickel and silicon by incoherent-light-pulse annealing

Mixed layers of Ni and Si were formed by pulsed incoherent-light annealing of Ni thin films evaporated on Si substrates. Incoherent light pulse of 36 μs produced in an arc-discharge plasma system was used as the energy source for annealings. A thin layer (300 Å) of amorphous silicon (a-Si) deposited on 800–1000 Å thick Ni films was found to increase light absorption significantly. The light energy needed to form uniform mixing was measured to be about 23 J/cm². Rutherford backscattering and Auger electron spectroscopy techniques were used for qualitative analysis of a-Si/Ni/Si samples. Optimum operating conditions of the light source was determined.     

Carrier removal profiles from oxygen implanted GaAs

Carrier removal profiles have been measured in annealed, oxygen implanted, n-type GaAs samples. The implants were performed at room temperature with an ion energy of 400 keV. A dose of 1015 O+/cm2 produced a resistivity of about 108 ?/? over a layer 0.6 ?m thick, but no significant electrical compensation was observed from doses less than 1013 O+/cm2. However, doses of 1011 to 5×1012 O+/cm2 produced resistivities of 108 to 109 ?/? without subsequent annealing.     

Carrier removal after H1+, H2+ or H3+ implants into GaAs

It is demonstrated that the carrier removal caused by implanting equivalent doses of H1+ H2+ and H3+ ions into GaAs is identical and approximately independent of the ion energy in the range 300?500 keV. Some recovery of carriers removed occurs at about 250°C.     

Negative X-ray resist produced by proton bombardment

Polymethylmetacrylate (PMMA) films of 580 nm have been irradiated by X-rays through a copper mask. Subsequent proton bombardment of the PMMA films (masked and unmasked regions) changes them, at doses ?2×1013 ions/cm2, from a positive to a negative resist.     

Thermal Resistance of a Tapered Roller Bearing

An apparatus to simulate the thermal behavior of a tapered roller bearing was constructed and used to determine tapered roller bearing thermal behavior. Bearing specimens can be loaded axially and/or radially while rotating. Shaft heating is also provided and mechanical losses measured. An infrared scanner and thermocouples allow for temperature measurement. An analytical model of the bearing and bearing/housing system was also developed and is presented. The model is capable of considering various modes of bearing operation. Experimental and theoretical resistances are compared. Typical thermal resistances from shaft to housing were found to be of the order of 1 K/W.