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Giant basal spicule from the deep-sea glass sponge Monorhaphis chuni: synthesis of the largest bio-silica structure on Earth by silicatein
Xiao-hong WANG, Xue-hua ZHANG, Heinz C. SCHR?DER, Werner E. G. MüLLER
Front Mater Sci Chin. 2009, 3 (3): 226-240.
https://doi.org/10.1007/s11706-009-0044-x
Like all sponges (phylum Porifera), the glass sponges (Hexactinellida) are provided with an elaborate and distinct body plan, which relies on a filigree skeleton. It is constructed by an array of morphologically determined elements, the spicules. Schulze described the largest siliceous hexactinellid sponge on Earth, the up to 3 m high Monorhaphis chuni, collected during the German Deep Sea Expedition “Valdivia” (1898–1899). This species develops an equally large bio-silica structure, the giant basal spicule (3 m × 10 mm). Using these spicules as a model, one can obtain the basic knowledge on the morphology, formation, and development of silica skeletal elements. The silica matrix is composed of almost pure silica, endowing it with unusual optophysical properties, which are superior to those of man-made waveguides. Experiments suggest that the spicules function in vivo as a nonocular photoreception system. The spicules are also provided with exceptional mechanical properties. Like demosponges, the hexactinellids synthesize their silica enzymatically via the enzyme silicatein (27 kDa protein). This enzyme is located in/embedded in the silica layers. This knowledge will surely contribute to a further utilization and exploration of silica in biomaterial/biomedical science.
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Preparation and cytocompatibility of silk fibroin / chitosan scaffolds
Zhen-ding SHE, Wei-qiang LIU, Qing-ling FENG
Front Mater Sci Chin. 2009, 3 (3): 241-247.
https://doi.org/10.1007/s11706-009-0048-6
One challenge in soft tissue engineering is to find an applicable scaffold, not only having suitable mechanical properties, porous structures, and biodegradable properties, but also being abundant in active groups and having good biocompatibility. In this study, a three-dimensional silk fibroin/chitosan (SFCS) scaffold was successfully prepared with interconnected porous structure, excellent hydrophilicity, and proper mechanical properties. Compared with polylactic glycolic acid (PLGA) scaffold, the SFCS scaffold further facilitated the growth of HepG2 cells (human hepatoma cell line). Keeping the good cytocompatibility and combining the advantages of both fibroin and chitosan, the SFCS scaffold should be a prominent candidate for soft tissue engineering, for example, liver.
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Biogenic nanoparticles and mineral composition in the radula of chiton Acanthochitonrubrolineatus
Chuan-lin LIU, Xiao-jie CHENG, Jian-gao ZHAO, Xia QIAN, Cheng-hua GUO, De-jiao YU, Xi-guang CHEN
Front Mater Sci Chin. 2009, 3 (3): 248-254.
https://doi.org/10.1007/s11706-009-0046-8
Magnetite particles were confirmed to deposit in the radula of chiton Acanthochiton rubrolineatus, and these magnetite particles presented as chip-shaped pieces which were 150 nm in width. Many nano-scale crystals constructed each piece of the magnetite particles. The mean size of a single crystal was 52 nm in diameter. Calcium composites were found to coexist with iron minerals. The total amount of magnetite in the chiton radula was 10% (w/w) of the radula weight, and 41% (w/w) of the total minerals. Eight metal elements were measured in the chiton radula, among which iron was a major element (14.6%, w/w) of the radula, followed by sodium, magnesium, calcium, potassium, chromium, manganese and cobalt in turn.
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Interfacial friction damping characteristics in MWNT-filled polycarbonate composites
Yu-hong MAN, Zheng-cao LI, Zheng-jun ZHANG
Front Mater Sci Chin. 2009, 3 (3): 266-272.
https://doi.org/10.1007/s11706-009-0040-1
The effects of strain, temperature, test frequency, and multi-walled nanotube (MWNT) weight percentage on the interfacial sliding at the tube-polymer interfaces were investigated by dynamic mechanical tests. The storage modulus first increased slightly then reached a plateau and finally decreased sharply with further increasing strain (temperature, frequency) amplitude. Moreover, the changing of the storage modulus of the nanocomposite lagged the loss modulus as a function of strain (temperature, frequency). Furthermore, with the increase of MWNT weight percentage interfacial slip was activated at relative smaller strain, lower temperature, or lower frequency. The possible influence of polymer wrapping carbon nanotubes in the interfacial area on interfacial friction was introduced.
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Surface-hardening effect of B implantation in 6H-SiC ceramics
Heng DU, Zheng-cao LI, Tian MA, Wei MIAO, Zheng-jun ZHANG
Front Mater Sci Chin. 2009, 3 (3): 281-284.
https://doi.org/10.1007/s11706-009-0041-0
This study was conducted on the surface-hardening effect of boron ion implantation in 6H-SiC ceramics. The SiC samples prepared by pressureless sintering were carefully polished, and 500 keV B+ implanted in 6H-SiC ceramics at room temperature and four implantation doses, namely, 1×1015, 5×1015, 1×1016, and 5×1016 cm-2, were chosen. The implanted samples were analyzed by scanning electron microscope and Raman spectra. The Vickers hardness of the samples was evidently increased. The thickness of the damage layer was about 1 μm, which is consistent with the simulated results. The structure of the damage layer was different from the internal part and severely damaged at high doses.
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Simulation analysis of thermal stress during casting process of large-sized alloy steel ingot
Yi-tao YANG, Wei LUO, Meng CHEN, Guang-jie SHAO
Front Mater Sci Chin. 2009, 3 (3): 301-305.
https://doi.org/10.1007/s11706-009-0049-5
To quantitatively analyze the main reasons of common crack in the surface of alloy steel ingot with 5%Cr during production and to propose the direction of improvement, a physical model system, which consisted of steel ingot mold, casting, riser of heat insulation, slag layer, sprue pipe, and runner, was primarily established by three-dimensional CAD software. The joint simulation method concerned with pouring, solidification, temperature field, and cast stress was determined by using ADSTEFAN cast simulation software. The stress distribution of casting and the quantitative effect of shake-out timing were analyzed in detail. An effective plan of decreasing stress was proposed in cooling mode.
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Effect of powder particle size on green properties and stress wave
Jian-zhong WANG, Hai-qing YIN, Xuan-hui QU
Front Mater Sci Chin. 2009, 3 (3): 319-324.
https://doi.org/10.1007/s11706-009-0038-8
In the powder metallurgy (PM) industry, high velocity compaction (HVC) technique is a new way to obtain higher density parts. In this study, three reduced pure iron powders with different particle sizes were pressed by HYP35-2 High Velocity Compaction Machine. A computer controlled universal testing machine was used to measure the bending strength of the green body. The relationships among the particle size, the impact velocity, the green density, the stress wave, the bending strength and the radial springback were discussed. The results show that the powder of -200 mesh is the best option among the three powders for the HVC process. At the identical impact velocity, the green density for the powder of -200 mesh is higher than the other two types of powders, while the bending strength and the radial springback for the powder of -300 mesh is the highest. In addition, the stress waves exhibit similar, pulsed waveforms. As the impact velocity rises up, the duration of the first peak decreases gradually, while that of the stress wave increases slowly. The response time for the powder of -200 mesh is shorter than the other two types of powders.
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Amorphization and crystallization characteristics of TiNi shape memory alloys by severe plastic deformation
Jun-tao LI, Wei-dong MIAO, Yu-ling HU, Yan-jun ZHENG, Li-shan CUI
Front Mater Sci Chin. 2009, 3 (3): 325-328.
https://doi.org/10.1007/s11706-009-0053-9
Differential scanning calorimetry (DSC) was used to determine the crystallization fraction and rate in TiNi alloys by severe plastic deformation. Results showed that the reverse martensitic transformation peak was not observed during the first heating at the rate of 40 K/min in the as-rolled samples, but one exothermic peak was observed at 620 K, which was associated with the amorphous crystallization process. During the second heating, reverse martensitic transformation was recovered. The onset crystallization temperature was low in the initial stage of crystallization with lower heating rates, but the crystallization fraction was found to increase with increasing temperature. However, the crystallization fraction was almost constant in the initial stage of crystallization with a relatively high heating rate. In all heating rates, the amorphous crystallization rates almost always reached maximum as the volumetric fraction of amorphous crystallization rose to 50%.
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18 articles
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