|
Injection of stored nucleotides from single-walled carbon nanotubes
Zhen-hai Li, Wei Yang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 709-713.
https://doi.org/10.1631/jzus.A1000158
We investigate the possibility of injection of a nucleotide via single-walled carbon nanotubes (SWNTs). The collapse process of an SWNT with a large radius may proceed like falling dominoes. The characteristics of a large radius SWNT are utilized to drive the nucleotide movement in the SWNT, or even to inject the stored nucleotide out of the SWNT. In this process, the lateral section of the collapsed SWNT resembles a dumbbell. Occasionally, the nucleotide in the SWNT will be inbreathed into one of the two dumbbell ends, leading to interference with the injection process. To investigate the random nature of the injection process, a series of simulations on SWNT with different lengths were carried out. It was found that the injection probability was not influenced by the tube length. Freezing the nucleotide at the beginning, or modifying the SWNT at the outlet, may serve to facilitate the injection process, as indicated by the rise in the injection probability.
|
|
Effects of vacancies on interwall spacings of multi-walled carbon nanotubes
Ming-du Ma, Jefferson Zhe Liu, Li-feng Wang, Lu-ming Shen, Quan-shui Zheng
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 714-721.
https://doi.org/10.1631/jzus.A1000174
We use molecular dynamics (MD) simulations to study the effects of vacancies on tube diameters and interwall spacings of multi-walled carbon nanotubes (MWCNTs). Two types of vacancies, double vacancy and three dangling-bond (3DB) single vacancy, are identified to have opposite effects on the tube size change, which explains the inconsistency of the experimentally measured interwall spacings of MWCNTs after electron beam irradiation. A theoretical model to quantitatively predict the shrunk structures of the irradiated MWCNTs is further developed. We also discuss the fabrications of prestressed MWCNTs, in which reduced interwall spacings are desired to enhance the overall elastic modulus and strength.
|
|
Effect of template shape on metal nanoimprinting: a dislocation dynamics study
Yun-he Zhang, Lucia Nicola
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 722-726.
https://doi.org/10.1631/jzus.A1000175
Dislocation dynamics simulations are performed to investigate the effect of template shape on the nanoimprinting of metal layers. To this end, metal thin films are imprinted by a rigid template made of an array of equispaced indenters of various shapes, i.e., rectangular, wedge, and circular. The geometry of the indenters is chosen such that the contact area is approximately the same at the final imprinting depth. Results show that, for all template shapes, the final patterns strongly depend on the dislocation activity, and that each imprint differs from the neighboring ones. Large material pile ups appear between the imprints, such that polishing of the metal layer is suggested for application of the patterns in electronics. Rectangular indenters require the lowest imprinting force and achieve the deepest retained imprints.
|
|
Microstructure and creep properties of high Cr resisting weld metal alloyed with Co
Xue Wang, Liang-fei Zhan, Qian-gang Pan, Zhi-jun Liu, Hong Liu, Yong-shun Tao
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 756-760.
https://doi.org/10.1631/jzus.A1000215
A 9% Cr ferritic steel weld metal containing 1% Co, partially substituted for nickel, was prepared by submerged arc welding (SAW) processing. The microstructure and creep properties of the weld metal were investigated. The microstructure exhibited a fully tempered martensitic structure free of δ-ferrite. The creep properties of the obtained weld metal were inferior to those of the P92 base metal at 600 and 650 °C. The values of A and n for weld metal in the Norton power law constitution at 650 °C are 1.1×10−21 and 8.1, respectively.
|
|
Microstructures and mechanical properties of SiBCNAl ceramics produced by mechanical alloying and subsequent hot pressing
Dan Ye, De-chang Jia, Zhi-hua Yang, Zhen-lin Sun, Peng-fei Zhang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 761-765.
https://doi.org/10.1631/jzus.A1000161
Amorphous SiBCNAl powders were prepared via a mechanical alloying (MA) technique using crystalline silicon (Si), hexagonal boron nitride (h-BN), graphite (C), and aluminum (Al) as starting materials. SiBCNAl powders were consolidated by a hot pressing (HP) technique at 1800 °C under a pressure of 30 MPa in argon and nitrogen. The sintering atmosphere had a great influence on the microstructures and mechanical properties of the ceramics. The two ceramics had different phase compositions and fracture surface morphologies. For the ceramics sintered in argon, flexural strength, fracture toughness, elastic modulus and Vickers hardness were 421.90 MPa, 3.40 MPa·m1/2, 174.10 GPa, and 12.74 GPa, respectively. For the ceramics sintered in nitrogen, the mechanical properties increased, except for the Vickers hardness, and the values of the above properties were 526.80 MPa, 5.25 MPa·m1/2, 222.10 GPa, and 11.63 GPa, respectively.
|
|
Microstructure and mechanical properties of liquid phase sintered silicon carbide composites
Jing-mei Ma, Feng Ye, Yan-ge Cao, Chun-feng Liu, Hai-jiao Zhang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 766-770.
https://doi.org/10.1631/jzus.A1000162
Silicon carbide (SiC) composites were prepared by hot-press sintering from α-SiC starting powders with BaAl2Si2O8 (BAS). The effects of additives on densification, microstructure, flexural strength, and fracture behavior of the liquid phase sintered (LPS) SiC composites were investigated. The results show that the served BAS effectively promotes the densification of SiC composites. The flexural strength and fracture toughness of the SiC composites can reach a maximum value of 454 MPa and 5.1 MPa·m1/2, respectively, for 40% (w/w) BAS/SiC composites. SiC grain pullout, crack deflection, and crack bridging were main toughening mechanisms for the sintered composites.
|
|
Effect of direct quenching on microstructure and mechanical properties of medium-carbon Nb-bearing steel
Ying-li Zhao, Jie Shi, Wen-quan Cao, Mao-qiu Wang, Gang Xie
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 776-781.
https://doi.org/10.1631/jzus.A1000147
The influence of direct quenching (DQ) on microstructure and mechanical properties of 0.19C-1.7Si-1.0 Mn-0.05Nb steel was studied. The microstructure and mechanical properties of reheat quenched and tempered (RQ&T) steel plate were compared with those of direct quenched and tempered (DQ&T) steel plates which were hot rolled at different finish rolling temperatures (1173 K and 1123 K), i.e., recrystallization-controlled-rolled direct-quenched (RCR&DQ) and controlled-rolled direct-quenched (CR&DQ), respectively. The strengths generally increased in the following order: RQ&T<RCR&DQ&T< CR&DQ&T. Strength differences between the CR&DQ&T and RQ&T conditions as high as 14% were observed at the tempered temperature of 573 K. The optical microscopy of the CR&DQ&T steel showed deformed grains elongated along the rolling direction, while complete equiaxed grains were visible in RQ&T and RCR&DQ&T steels. Transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) of the DQ steels showed smaller block width and higher density of dislocations. Inheritance of austenite deformation substructure by the martensite and differences in martensite block width were ruled out as major causes for the strength differences between DQ and RQ steels.
|
|
Estimation of the J-resistance curve for Cr2Ni2MoV steel using the modified load separation parameter Spb method
Chen Bao, Li-xun Cai
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 782-788.
https://doi.org/10.1631/jzus.A1000153
Based on load separation theory, the load separation parameter Spb method is an effective approach for estimating the J-resistance curve from records of load versus displacement directly, using one sharp cracked specimen and an additional reference blunt cracked specimen. However, the effect of the reference blunt cracked specimen on J-resistance determination was not explicitly considered in past work. In this paper, a modified load separation parameter Spb method was developed to eliminate this effect, and then a unique estimation of instantaneous crack length for one sharp cracked specimen could be obtained. Furthermore, a forced blunting calibration method was also adopted to determine the instantaneous crack length in the load inseparable region, referring to a normalization method. Experiments on steam turbine rotator steel Cr2Ni2MoV were carried out to estimate J-resistance curves using an unloading compliance method. By removing unload and reload data from load-displacement records, the J-resistance curve for the same sharp cracked specimen was estimated using the modified separation parameter Spb method. The results indicate that the modified Spb method completely eliminates the effect of the reference blunt cracked specimen on the instantaneous crack length determination of the sharp cracked specimen. However, different J-resistance curves in a small range of crack extension are present when different blunting coefficients are used in the blunting line equation. The J-resistance curve obtained from the modified Spb method agrees well with that obtained from the compliance method.
|
|
Propagation of flexural waves in phononic crystal thin plates with linear defects
Zong-jian Yao, Gui-lan Yu, Yue-sheng Wang, Zhi-fei Shi, Jian-bao Li
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2010, 11(10): 827-834.
https://doi.org/10.1631/jzus.A1000123
The band structures of flexural waves in a phononic crystal thin plate with straight, bending or branching linear defects are theoretically investigated using the supercell technique based on the improved plane wave expansion method. We show the existence of an absolute band gap of the perfect phononic crystal and linear defect modes inside the gap caused by localization of flexural waves at or near the defects. The displacement distributions show that flexural waves can transmit well along the straight linear defect created by removing one row of cylinders from the perfect phononic crystals for almost all the frequencies falling in the band gap, which indicates that this structure can act as a high efficiency waveguide. However, for bending or branching linear defects, there exist both guided and localized modes, and therefore the phononic crystals could be served as waveguides or filters.
|
20 articles
|