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1.
To investigate the durability, especially the long-term stability of cement-based materials with very low w/b, the air permeability test, carbonation test, capillary absorption rate test and dilation Dotential test were adopted under long-term heat treatment condition. Microstructure of these materials is also analyzed by scannmg electronic microscopy (SEM) and mercury intrusion porosimeter (MIP) in order to further unveil its mechanism and interrelation between microstructure and its properties. The results indicate that in the area investigated, cement-based material with w/b 0.17, like RPC, possesses low porosity and excellent durability. Moreover, its porosity will further decrease under long-term heat treatment compared with normal heat treatment. Its long-term durability is much superior to that of other cement-based materials with w/b 0.25 or 0.35 as high strength concrete (HSC). 相似文献
2.
The precipitation behavior of V(C, N) in steels microalloyed with vanadium was researched using a thermal simulator during single-pass deformation at 800-750 ℃. The V(C, N) precipitates and its nucleation effect on ferrite were investigated by TEM and EDS. The experimental results show that there are two remarkable heterogeneous nucleation effects of V(C, N) particles precipitated before γ →/ α phase change: primary reason is that high coherency between V(C, N) and ferrite promotes V(C, N) to become a nucleating center of intragranular ferrite; secondary reason is that the coarsening of V(C, N) causes locally solute-poor region in austenite, thus expedites the nucleation of intragranular ferrites further. Furthermore, the relationship between the size and shape of V(C, N) was studied, and identification method was provided for distinguishing interphase precipitation and general precipitation to avoid erroneous judgment and misguide. 相似文献
3.
王建南 《武汉理工大学学报(材料科学英文版)》2011,26(6):1044-1048
The study aimed to investigate the adhesion, morphology and proliferation of Sprague Dawley (SD) albino rat bone marrow-derived
mesenchymal stem cells (BMSCs) by inverted microscope, cell counting, MTT test and laser scanning confocal microscop (LSCM).
On the regenerated A yamamai SF film or blend films, the cell morphology was almost the same as that on collagen (collagen type I) film, the cell adhesion
rate was higher than that on plastic cell plate and B mori SF film after 1 h (p < 0.01) of culture, and the cell proliferation was significantly higher than that on collagen film (p < 0.01) and plastic cell plate (p < 0.01), and also obviously better than that on B mori SF film. On the other hand, the viability of BMSCs in the regenerated A yamamai SF porous scaffold was better than that in B mori SF porous scaffold and medical grade polyvinyl alcohol (PVA) sponge. 相似文献
4.
Nanoparticle (NP) is the matter between molecule and bulk material. It has attracted much attention in catalysis, optoelectronics
and biology due to its unique physical and chemical properties. Incorporation of these NPs into the polymer matrix is one
of the best methods to display their special functions, which not only stabilize the NPs but also realize the functional assembly
of NPs and polymers. However, realization of this idea depends largely on the compatibility of NPs and polymers as well as
the interaction between them. Therefore, many methods have been developed to prepare the composites of NPs and polymers in
order to obtain the function expected. In this review, we mainly focus on the combination of in situ method with other methods to synthesize different functional one-dimension, two-dimension as well as bulk composites, which
has been recently developed by our group. The most striking character of our method is the excellent compatibility between
NPs and polymers which ensures a homogeneous distribution of NPs in the polymer matrix. The existence of the polymer network
makes the NPs more stable, and is significant for displaying their functions.
Supported by the National Natural Science Foundation of China (Grant Nos. 2007CB936402, 20534040) and Science Foundation for
Young Teachers of Northeast Normal University (Grant No. 20070306) 相似文献
5.
The Synechocystis sp. PCC 6803 genome harbours a Deg gene family consisting of three members, htrA (degP, slr1204), hhoA (degQ, sll1679) and hhoB (degS, sll1427). This work provided biochemical characterization of HhoA, HtrA and HhoB from Synechocystis sp. PCC 6803. Firstly mature HhoA, HhoB and HtrA from Synechocystis sp. PCC 6803 were cloned and expressed as soluble recombinant his-tagged fusion protein in Escherichia coli. Then the proteolytic activity of HhoA, HhoB and HtrA was tested using casein, bovine serum albumin, five recombinant chromoproteins
and cyanobacterial phycocyanin as substrates in vitro. The experimental results showed that HhoA and HtrA had proteolytic activity on casein, five recombinant chromoproteins and
cyanobacterial phycocyanin. No proteolytic activity of HhoB was found using all substrates in vitro, indicating functional difference among Deg proteases from Synechocystis sp. PCC 6803. Therefore, the results indicated the biochemical properties of HhoA and HtrA on hydrolysis of proteins and
phycobiliproteins in vitro, which implicated that they were proteases possibly involved in phycobiliprotein degradation in vivo. 相似文献
6.
The photocatalytic degradation of E.coli membrane cell by ZnO nanowires was studied using field-emission scanning electron microscope(FE-SEM),fluorescence microscopy,and Attenuated total reflection fourier transform infrared(ATR-FTIR).The outer membrane of E.coli was removed completely in the presence of ZnO nanowires under UV irradiation,and the cells became twisted shapes without a mechanically strong network.After ZnO nanowires photocatalysis,the permeability of the treated cells increased to some degree that could be confirmed by quantum dots labeling technique.Structural changes in the cell wall membrane were revealed by the decay of the characteristic groups bands in ATR-FTIR spectra. 相似文献
7.
The Cu x Si1-x thin films have been grown by pulsed laser deposition (PLD) with in situ annealing on Si (001) and Si (111), respectively. The transformation of phase was detected by X-ray diffraction (XRD). The results showed that the as-deposited films were composed of Cu on both Si (001) and Si (111). The annealed thin films consisted of Cu + η”-Cu3Si on Si (001) while Cu + η’-Cu3Si on Si (111), respectively, at annealed temperature (T a) = 300-600 °C. With the further increasing of T a, at T a= 700 °C, there was only one main phase, η”-Cu3Si on Si (001) while η’-Cu3Si on Si (111), respectively. The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing T a detected by field emission scanning electron microscope (FESEM). It was also showed that the grain size would enlarge with increasing annealing time (t a). 相似文献
8.
Novel straight silicon oxide [SiO
x
(1<x<2)] nanorod Y junctions have been synthesized on Si plate by thermal evaporation of mixed powders of silica and carbon nanofibers
at 1300°C and condensation on a Si substrate without assistance of any catalyst. The synthesized samples were characterized
by means of scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy,
and energy dispersive X-ray spectroscopy. The results suggested that the straight nanorod Y junctions are amorphous and consist
only of elements Si and O, and these rods with diameters about 50–200 nm have a neat smooth surface. The growth of such silicon
oxide nanorods may be a result of the second nucleation on the surface of rods causing a change in the growth direction of
silicon oxide nanorods developed.
Supported by the Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing,
and the Program of Science & Technology Activity for Chinese Homecoming Fellow Abroad and Research Program of Beijing Key
Laboratory for Sensor (Grant No. KM200810772009) 相似文献
9.
This study examined the individual and simultaneous adsorption of SO{in{itx}} (SO{in{it2}}) and NO{in{itx}} (NO-NO{in{it2}})
on activated carbon prepared from waste palm shell. The adsorption process was examined in a fixed bed reactor at low temperatures
(100\2-300\dgC). For individual adsorption without any catalytic activation, SO{in{itx}} showed good adsorption whereas NO{in{itx}}
was very much poor. In the simultaneous adsorption of SO{in{itx}} and NO{in{itx}}, SO{in{itx}} showed greater adsorption affinity
than NO{itx}. For palm shell activated carbon (PSAC) impregnated with metal catalyst (Ni and Ce) the concentration adsorbed
profile showed that the amount of SO{in{itx}} adsorbed decreased regularly, while the amount of the adsorbed NO{in{itx}} increased
irregularly. The properties of the pure and impregnated PSAC were analyzed by BET, SEM and EDX. These investigations indicated
that PSAC impregnated with metal catalyst is the determining factor in the adsorption of SO{in{itx}} and NO{in{itx}} simultaneously.
Supported financially by Yayasan FELDA, Malaysia (Grant No. 6050075) 相似文献
10.
宋玉林 《武汉理工大学学报(材料科学英文版)》2010,25(5):803-806
An IKVAV (Isoleucine-Lysine-Valine-Alanine-Valine)-containing peptide amphiphile molecule (IKVAV-PA) was implanted subcutaneouly
into rat backbone in the middle. Angiogenesis induced by IKVAV-PA was evaluated in vivo. 200 μL of 10, 2, 1 and 0.5 wt% IKVAV-PA solution were added into DMEM/F12 and self-assembled into nanofiber hydrogel. 1 mL of 1% IKVAV-PA (Experimental Group, EG) and 1 mL of 16.67% gelatin (Control
Group, CG) were injected subcutaneously into rat backbone. The specimens were harvested two weeks after injection and examined
immunohistochemically for VEGF(Vascular Endothelial Growth Factor). TEM observations of hydrogels revealed a network of nanofibers,
and there was a significant positive correlation between IKVAV-PA concentration and nanofiber alignment. Light microscopy
observation showed capillary vessel with complete walls formed in hydrogel, with erythrocytes noted inside the vessels in
EG; capillary vessels or erythrocytes were not found within gelatin in CG. Immunohistochemical analysis revealed that there
were VEGF-positive cells within hydrogel, which were not found in CG. Self-assembled hydrogel from IKVAV-PA was able to induce
the angiogenesis in vivo. 相似文献
11.
曹成波 《武汉理工大学学报(材料科学英文版)》2010,25(1):4-7
To study the controlled effect of poly (lactic acid) (PLA), poly lactic-co-glycolic (PLGA) and ethylenediamine (EDA)-maleic anhydride (MAH) modified PLA (EMPLA) for in vitro release of nestorone, rods were prepared using the solvent evaporation method. Amount of drug release in vitro was determined by UV spectrophotometry. Effects of rods diameter, the molecular weight of PLA, the drug percentage and the hydrophilicity of polymers on the release of biodegradable nestorone rods in vitro were investigated. It is indicated that the controlled effect of the biodegradable rods for the release of nestorone in vitro is good. The amount of drug released every week from rods in different diameter is similar to one another. The amount of drug released every week and the accumulative drug released during 12 week were almost in direct proportion with the drug percentage of the rods. The amount of drug released every week is increased as the decreasing of PLA molecular weight. As the hydrophlicity of polymer is improved, the rate of drug release every week is accelerated. The studies show that the plausibility of controlled release of nestorone from PLA, PLGA and EMPLA rods imply the possibility of their application as a controlled delivery system for nestorone. The results show that the greater the molecular weight of PLA is, the slower its degradation is and the slower the drug released; the greater the percentage of nestorone is, the more quickly the drug release. An increase of the hydrophilicity of the polymers will increase their degradation rate and leads to a fast drug release. Anyhow, these rods systems should be further evaluated in vivo. 相似文献
12.
The magnetic properties and structures of [CoPt/Ag]
n
, multilayer films deposited by DC magnetron sputtering have been studied. During the deposited process, two kinds of deposited
sequences, that is Ag layer (FDAG) first deposited or CoPt layer (FDCP) first deposited, have been chosen. The results show
that the microstructures and coercivities were strongly influenced by the deposited sequence and the thickness of films. The
coercivities of [Ag/CoPt]
n
with FDAG are obviously higher than those of [CoPt/Ag]
n
with FDCP. Especially, when the thickness of films is 8 nm, the difference of coercivities between the FDAG film and the
FDCP film is the largest. It is possibly because Ag plays a role of underlayer in FDAG multilayers, which can induce both
the transformation from fcc to fct and the oriented growth along c-axis. In addition, δM curves reveal that the [CoPt/Ag]8 multilayer, film has a lower intergrain interaction than the CoPt/Ag bilayer film. 相似文献
13.
Hexagonal boron nitride ceramic (h-BN) based on the nitridation of B powders was obtained by reaction sintering method. The effects of sintering temperature on the mechanical properties and microstructure of the resultant products were investigated and the reaction mechanism was discussed. Results showed that the reaction between B and N2 occurred vigorously at temperatures ranging from 1 000 °C to 1 300 °C, which resulted in the generation of t-BN. When the temperature exceeded 1 450 °C, transformation from t-BN to h-BN began to occur. As the sintering temperature increased, the spherical particles of t-BN gradually transformed into fine sheet particles of h-BN. These particles subsequently displayed a compact arrangement to achieve a more uniform microstructure, thereby increasing the strength. 相似文献
14.
The microstructure, tensile property and wear resistance of 7075 aluminum matrix composite reinforced with TiC particles prepared by in-situ reaction casting were investigated. The effect of TiC reinforcement on wear behavior was analyzed. The wear mechanism was also discussed. A micro-mechanism model of reaction kinetics for synthesis of TiC was acquired. Results show that TiC could increase the tensile and yield strength, but decrease the elongation. Besides, TiC particles improve the property of wear resistance of 7075 aluminum alloy. The wear mechanisms include abrasive wear and adhesive wear in wear test process. 相似文献
15.
张光富 《武汉理工大学学报(材料科学英文版)》2018,33(3):566-570
The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn2Ge2 (R=Gd, Tb and Dy) were investigated by using the X-ray diffraction method and magnetic measurement. The results showed that the compounds experience two magnetic transitions, namely the second-order paramagnetic to antiferromagnetic transition at temperature TN (TN=368, 423 and 443 K for GdMn2Ge2, TbMn2Ge2 and DyMn2Ge2, respectively) and the first-order antiferromagnetic - ferrimagnetic transition at temperature Tt (Tt=96, 80 and 40 K for GdMn2Ge2, TbMn2Ge2 and DyMn2Ge2, respectively) as the temperature decreases. The temperature dependence of the lattice constant a(T) displays a negative magnetoelastic anomaly at the second-order transition point TN and, at the first-order transition Tt, a increases abruptly for GdMn2Ge2 and TbMn2Ge2, Δa/a about 10-3. Nevertheless, the lattice constant c almost does not change at these transition points indicating that such magnetoelastic anomalies are mainly contributed by the Mn-sublattice. The transitions of the magnetoelastic properties are also evidenced on the temperature dependence of magnetic susceptibility χ. The first-order transition behavior at Tt is explained by the Kittel mode of exchange inversion. 相似文献
16.
The numerical manifold method (NMM) features its dual cover systems, namely the mathematical cover and physical cover, which provide a unified framework for mechanics problems involving continuum and discontinuum deformation. Uniform finite element meshes can be and are usually used to construct the mathematical cover. Though this strategy can handle different kinds of problems in a unified way, it is not economical for cases with steep deformation gradients or singularities. In this paper, using the recovery-based error estimator, an h-adaptive NMM on quadtree meshes is proposed to deal with such cases. The quadtree meshes serve as the mathematical meshes, on which the local refinement is carried out. When the quadtree meshes are refined, the corresponding mathematical cover, physical cover and manifold elements are updated accordingly. To handle the hanging nodes in the quadtree meshes, we resort to mean value coordinates. Comparing to the refinement based on manifold elements, the proposed strategy guarantees consistent structured meshes throughout the adaptive process, thus retaining the unique feature of original NMM. In contrast with polygonal finite element method, an advantage of the proposed method is that the meshes do not need to conform to the crack face and material boundary, which means the adaptive NMM is very suitable for problems with complex geometric boundary. Several representative mechanics problems, including crack problems, are analyzed to investigate the effectiveness of the proposed method. It is demonstrated that the proposed adaptive NMM has higher accuracy and better performance comparing to uniform refinement strategy. 相似文献
17.
李方 《武汉理工大学学报(材料科学英文版)》2011,26(5):950-954
Polyethylene terephthalate (PET,Dacron) was modified by surface immobilization of hirudin with glutaraldehyde(GA) as coupling reagent to improve the blood compatibility.Hirudin-immobilized PETs were characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements.The blood compatibility of the PETs was evaluated by platelet adhesion evaluation and fibrinogen conformational change measurements in vitro.The results showed the decrease of platelet adhesion and activation on hirudin-immobilized PET with increasing of glutaraldehyde concentration.Fibrinogen experiment showed that fibrinogen adherence and conformational changes of PET-HRD were less than those of untreated PET,which made the materials difficult to form thrombus.The proper reason of blood compatibility improvement was low interface tension between hirudin-immobilized PETs and blood,as well as blood proteins,and low ratio of dispersive/polar component of the surface energy(γsd/γsp) and high hydrophilicity. 相似文献
18.
An in-situ polymerization method was employed to synthesize the nanosilica/acrylic/epoxy (SAE) hybrid coating on AISI 430 stainless
steel (430SS), as compared with a traditional blending method. Microstructures of the blending SAE hybrid coating (BC) and
in-situ SAE hybrid coating (ISC) were characterized by transmission electron microscopy (TEM). Corrosion resistance of BC
and ISC on 430SS was evaluated by the neutral salt spray test and potentiodynamic polarization technique. Failure mechanism
of the BC on 430SS was suggested by the microstructures and corrosion behaviors. Serious aggregation of nanosilica particles
in the BC impairs its structural uniformity and induces the flaws formation. These flaws in the BC initiates the failures
of pitting, filiform corrosion and peeling which are accelerated by the O2 concentration cell and H+ self-catalysis in chlorine-containing moist environments. The ISC-coated 430SS shows a more advantageous corrosion resistance
than that of the BC-coated. The ISC-coated 430SS can suffer the salt spray over 1000 h. Besides, it exhibits a high corrosion
potential beyond 0.925 V and good passivation characteristics during the potentiodynamic polarization.
Supported by the National Basic Research Program of China (“973” Program) (Grant No. 2004CB619305) and the National Natural
Science Foundation of China (Grant No. 50571044) 相似文献
19.
The biological method to synthesize thuringiensin and the influence of formate on thuringiensin biosynthesis were investigated. Addition of 1.00 g/L formate to growth medium of bacillus thuringiensis YBT-032 resulted in significant enhancements in productions of citrate, α -ketoglutarate, intracellular adenine and thuringiensin. These results demonstrate that added formate attends metabolism of cell, facilitates carbon metabolic flux in tricarboxylic acid cycle and hexose monophosphate pathway. As a carbon source, formate facilitates cell growth, increases glucose consumption and enhances the ability of cell to synthesis adenine analogues, and subsequently thuringiensin. Thuringiensin production rate significantly enhanced from 6.44 to 8.46 mg·g^-1 · h and transformation ratio from glucose to thuringiensin increased by 43.30%. 相似文献
20.
A new bacterial strain, was designated as strain Acidiphilium cryptum DX1-1, accumulates intracellular poly-β-hydroxybutyrate particles, four methods which have advantages and disadvantages for each were employed to extract PHB. Chloroform-sodium
hypochlorite method is the best in extracting PHB form Acidiphilium cryptum DX1-1. The extraction rate reaches 73%, the purification rate is 92% and molecular weight is 326 kg/mol. Then the PHB extracted
by this method was analyzed by ultraviolet-visible absorption spectroscopy, fourier transform infrared (FT-IR) and nuclear
magnetic resonance (NMR). The results show that PHB from strain DX1-1 has the same biochemical structure and character with
PHB standard. Mass spectrometer (MS) analysis reveals that the long chain of PHB is destroyed when treated by chloroform-sodium
hypochlorite. The differential scanning calorimetry (DSC) of PHB shows PHB from Acidiphilium cryptum DX1-1 has low degree of crystallinity which makes the PHB has a wider range of applications. 相似文献