A SiC nanowires-reinforced SiC matrix composite was fabricated using chemical vapour infiltration (CVI) process. SiC nanowires with thin carbon coating were grown directly in a fibrous preform prior to the CVI matrix densification. The nanowires consist of single crystal β phase SiC and uniform carbon shell coating of ∼5 nm, with diameters of several tens to 100 nm. The volume fraction of the nanowires in the fabricated composite is ∼5%. Contributions of the nanowires to the mechanical properties of the composite are expected.
"Consequently, they are widely used to fabricate structural and functional composites for extremely harsh environment  . Nowadays, various synthesis methods have been explored to produce β-SiC whiskers, including chemical vapor deposition using silicon precursor   , carbon template of carbon nanotubes to β-SiC whiskers  , thermal evaporation  , carbothermal reduction , etc. Generally, the growth mechanisms of SiC whiskers are involved in vapor–solid (VS) and vapor– liquid–solid (VLS) mechanisms    . "
[Show abstract][Hide abstract] ABSTRACT: Silicon carbide whiskers have been synthesized by using reactive graphite as a template. Natural graphite flake was firstly activated using chemical oxidation and thermal oxidation methods. After that, the reactive graphite sources were mixed with silicon powder and heated in the coke bed at 1200 and 1400 °C. The structural evolution of graphite and morphologies of SiC whiskers were studied with the aids of XRD, SEM, TEM and EDS techniques. The results showed that natural graphite flake can be activated into reactive graphite such as oxidized graphite and expanded graphite with much more defects using thermal and chemical oxidation methods. The expanded graphite with a great deal of defects has higher reactivity than natural graphite flake and oxidized graphite and accelerates the formation of long and thick SiC whiskers. It is proposed that the vapor–solid mechanism is predominant for the growth of β-SiC whiskers in this system. During heating-up, Si or SiO vapors meet with the activated carbon atoms on graphite substrate to form SiC nucleus. Then these vapors continually deposit on the SiC nucleus following the SiC whiskers which grow along the 〈111〉 direction.
Ceramics International 01/2014; 40(1):1481–1488. DOI:10.1016/j.ceramint.2013.07.032 · 2.61 Impact Factor
"Thus, regardless of their favorable biological properties, the poor mechanical properties of HAp bioceramics have severely hindered their clinical applications (Hench 1991; Yaszemski et al. 1996). Therefore, a number of studies have been focused on the improvement of the mechanical properties of HAp bioceramics (Shen et al. 2001; Suchanek et al. 1997), and studies have shown that the mechanical properties of the ceramics could be reinforced remarkably by one dimensional (1-D) nanoscale building blocks such as nanorods, nanofibers, and nanotubes (Ramay and Zhang 2004; Yang et al. 2004; Kobayashi and Kawai 2007). However, ultrastructural examination of deproteinated bone reveals that individual 25–50 nm HAp crystal is the essence of bone in terms of mechanical properties and bioresorbability, and plays an important role in biomineral formation (Shi et al. 2009). "
[Show abstract][Hide abstract] ABSTRACT: Hydroxyapatite (HAp) nanostructures may be an advanced candidate in biomedical applications for an apatite substitute of bone
and teeth than other form of HAp. In contrast, well-defined size and shape control in synthesizing HAp nanostructures is always
difficult. In this study, hydroxyapatite nanorods (HAp NRs) were prepared by simple hydrothermal method with controlling the
reaction time without using any surfactant or templating agents. The nanostructure clearly depicts the growth stages of the
HAp NRs by increasing the reaction time. The synthesized HAp has the rod like morphology with uniform size distribution with
the aspect ratio of about 8–10. Transmission electron microscopic (TEM) and high resolution TEM (HRTEM) images show that the
growth direction of the HAp is parallel to the (001) plane. The interplanar distances measured in segments (fringes) of the
HRTEM micrograph were ~0.35nm, corresponding to the interplanar spacing of the (002) plane of the hexagonal HAp. X-ray diffraction
(XRD) measurements indicate that the improved crystallinity of the HAp by increasing the reaction time. The mechanical studies
reveal that the improved tensile strength and the abrasion resistance are observed for the HAp nanorods reinforcing with high
molecular weight polyethylene (HMWPE).
KeywordsNanorods–Hydroxyapatite–Polyethylene–TEM–Mechanical properties–Biocompatible implants–Nanomedicine
Journal of Nanoparticle Research 05/2011; 13(5):1841-1853. DOI:10.1007/s11051-010-9932-3 · 2.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present some results on the statistics of the packet error
process and on the resulting throughput of TCP when a smart antenna
system is used to transmit signals from a base station to wireless
users. Multiple users are assumed to be present, and the propagation
environment considered includes frequency selective fading. The main
results presented involve the tradeoffs between various systems
parameters. It is shown that smart antennas have the potential to
improve the wireless channel adequately, thereby essentially solving the
performance problems which affect TCP. It is also shown that the whole
complexity of these scenarios can be essentially summarized by the
fading rate (Doppler frequency) and by the average packet error rate,
thereby allowing the introduction of the concept of an "equivalent
single-antenna system" and the scalability of the many available results
for the latter case
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