A modification of the precursor infiltration pyrolysis (PIP) method was explored to prepare the integrated doped ceramic matrix and coating by the added Sic nanowires layer and shape-stabilization process. The epitaxi...
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A modification of the precursor infiltration pyrolysis (PIP) method was explored to prepare the integrated doped ceramic matrix and coating by the added Sic nanowires layer and shape-stabilization process. The epitaxial layer of Sic nanowires provided surficial attachments for the precursor. And the shape-stabilization process aggregated loose ceramic particles into a coating. Then the Sic nanowire-reinforced Zrc-Siccoating-matrix integrated c/c (S/SZ-cZ/c) composite was simply prepared by the modified PIP method. The bonding strength between the coating and matrix of the S/SZ-cZ/ccomposite was improved. Through the ablation test, the mass and linear ablation rate of the S/SZ-cZ/ccomposite were 0.46 mg/s and 0.67 mu m/s, which were 60.34 % and 74.91 % lower than those of the Sic nanowire-reinforced c/c-Zrc (S/cZ/c) composite, respectively. The integration of the coating and matrix enabled the formation of a continuous oxide layer of molten SiO2 and ZrO2 in the ablation process, which helped to block the oxygen and heat during the ablation test. Thus the ablation resistance of the materials was systematically and effectively improved.
c++ and concurrent c are both upward-compatible supersets of c that provide data abstraction and parallel programming facilities, respectively. Although data abstraction facilities are important for writing concurrent...
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c++ and concurrent c are both upward-compatible supersets of c that provide data abstraction and parallel programming facilities, respectively. Although data abstraction facilities are important for writing concurrent programs, we did not provide data abstraction facilities in concurrent c because we did not want to duplicate the c++ research effort. Instead, we decided that we would eventually integrate c++ and concurrent c facilities to produce a language with both data abstraction and parallel programming facilities, namely, concurrent c++. Data abstraction and parallel programming facilities are orthogonal. Despite this, the merger of concurrent c and c++ raised several integration issues. In this paper, we will give introductions to c++ and concurrent c, give two examples illustrating the advantages of using data abstraction facilities in concurrent programs, and discuss issues in integrating c++ and concurrent c to produce concurrent c++.
Poor thermal conductivity, especially in thickness direction, is a major obstacle to extend the service lifetime of c/Siccomposite. However, there are few papers focusing on finely designing heat conductive channel b...
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Poor thermal conductivity, especially in thickness direction, is a major obstacle to extend the service lifetime of c/Siccomposite. However, there are few papers focusing on finely designing heat conductive channel but a simply introduction of various modifiers to improve c/Sic thermal conductivity, which leads to less success. Herein, multi-layer graphene sheets were utilized to improve the thermal conductivity of c/Siccomposites via an effective method to design graphene heat conductive channels. To determine the role of graphene sheets in improving thermal conductivity, the effect of the different loading fractions of graphene and microstructure of as-prepared composites were systemically investigated. Results revealed that the thermal conductivity of composites increased by 204% with well-designed graphene heat conductive channels. Besides, compared with the porosity, the orderly aligned heat conductive pathways played a more important role in thermal conductivity. This work provides a new and effective method for preparing well-designed heat conductive channels to enhance thermal conductivity of c/Sic.
The electrical properties of c/Siccomposites could be used for online and in-situ damage monitoring. To investigate alternating current (Ac) impedance response to damage in the c/Siccomposites, monotonic and increme...
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The electrical properties of c/Siccomposites could be used for online and in-situ damage monitoring. To investigate alternating current (Ac) impedance response to damage in the c/Siccomposites, monotonic and incremental cyclic tensile tests were performed. Both Ac impedance and acoustic emission (AE) techniques were applied to clarify the damage evolution during the tests. The relationship between damage and electrical impedance response was investigated and validated via macroscopic equivalent circuit models. The effects of longitudinal deformation and damage on Ac impedance characteristics, including impedance magnitude and phase angle, were obtained from the models. Results showed that the longitudinal deformation increases the impedance magnitude and the phase angle, and the damage causes the impedance magnitude to increase and the phase angle to decrease. The phase angle is significantly sensitive to fiber breakage, which makes the Ac-based method more suitable for online damage monitoring and final failure warning.
A set of experiments was carried out in the system NaAlSi3O8-FeO-NiO-coO-Sic-NaH(2)PO(4)at 1550 degrees c, 4 GPa, and oxygen fugacity (fO(2)) 0.5-2.9 log. units below the iron-wustite (IW) buffer to estimate how c-O-H...
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A set of experiments was carried out in the system NaAlSi3O8-FeO-NiO-coO-Sic-NaH(2)PO(4)at 1550 degrees c, 4 GPa, and oxygen fugacity (fO(2)) 0.5-2.9 log. units below the iron-wustite (IW) buffer to estimate how c-O-H components can affect Ni, co, and P partition between silicate melt and a liquid metallic phase at redox conditions under which the metallic phase is segregated into melting products of the early reduced mantles of the Earth and other planetary bodies. It has been established that the Ni, co, and P partition coefficientsD(\M)(met/sil)between silicate melts saturated with carbon and containing dissolved c-O-H volatiles (mainly in the form of OH groups, H(2)and cH4) at relatively oxidized conditions (fO(2)> IW - 1.5) correspond toD(\M)(met/sil)values expected of metal-silicate melt equilibrium in volatile-free systems at analogousP,T,f(O2), andnbo/tparameters. Under more reduced conditions (fO(2)<= IW - 2), the presence of c-O-H volatiles leads to a decrease inD(\M)(met/sil)for Ni and P compared to that in "dry" melts. This difference increases with decreasingfO(2)and reaches similar to 0.5 and more than one order of magnitude for Ni and P, respectively, atfO(2)= IW - 2.9. The effect of volatiles onD(co)(met/sil)is much weaker, and hence, a decrease infO(2)leads to thatD(Ni)(met/sil)andD(co)(met/sil)converge. The Raman spectra of the experimental glasses and their SIMS analyses for hydrogen show that water content (OH + H2O) in the melts decreases with decreasingfO(2), whereas the contents of cH(4)and complexes with c-H bonds significantly increases. The likely reasons for the decrease inD(\M)(met/sil)under strongly reduced conditions may be changes in the structure of the silicate melts and the origin of complex compounds of siderophile elements with volatiles in these melts.
Metallic foam was introduced as an interlayer to improve the performance of the brazed c/ccomposite-titanium alloy joint, and the interfacial microstructure and residual stress of the brazed joint were investigated. ...
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Metallic foam was introduced as an interlayer to improve the performance of the brazed c/ccomposite-titanium alloy joint, and the interfacial microstructure and residual stress of the brazed joint were investigated. compared with the brazed joint without foam, introducing foam interlayer could achieve the uniform bonding interface, and Ag-based solid solution (Ag(s,s)) became more dispersed and smaller in the center of the brazing seam. The thickness of reaction layer close to c/ccomposite side was less than 1 mu m. Some cu-based solid solution (cu(s,s)) was detected, indicating that cu foam still existed after brazing. The residual stress and its distribution calculated by finite element method (FEM), and the residual stress of the brazed joint decreased from 293 MPa to 228 MPa. The introduction of the foam interlayer could obtain homogeneous microstructure, change stress distribution, and improve mechanical properties of the brazed joints.
Highly diastereoselective 1,3-dipolar cycloaddition of in situ generated c,N-diaryl nitrilimines to (1R)-thiocamphor leads to chiral spiro-1,3,4-thiadiazolocamphane derivatives in good yields. The structures and stere...
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Highly diastereoselective 1,3-dipolar cycloaddition of in situ generated c,N-diaryl nitrilimines to (1R)-thiocamphor leads to chiral spiro-1,3,4-thiadiazolocamphane derivatives in good yields. The structures and stereochemistries of the new cycloadducts were fully established by spectroscopic methods including X-ray diffraction data. The diastereoselectivity observed in this reaction was explained by means of a brief theoretical study.
Based on the oxidation kinetics of c/Siccomposites at 900o-1200oc in stress-oxidation environment, a non-uniform model of oxidation has been suggested in this paper. combined with fiber notch model, curtin's stre...
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Based on the oxidation kinetics of c/Siccomposites at 900o-1200oc in stress-oxidation environment, a non-uniform model of oxidation has been suggested in this paper. combined with fiber notch model, curtin's strength model and BHE model, the non-uniform model is able to predict the failure time and residual strength of c/Siccomposites accurately. Besides, the initial defects of the model (matrix coating crack and open porosity), the effects of coating were taken into account, and the fiber strength and broken ratio were analyzed. Furthermore, the effects of oxidation time, stress, temperature, Si ccoating thickness and volume fraction of fiber on the failure time and residual strength were discussed, and the predicted results showed a good consistency with the experimental data.
Tools for computer-aided teaching and learning provide multiple benefits from the point of view of teaching because it allows emphasizing or illustrating certain issues that are sometimes difficult to emphasize withou...
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Tools for computer-aided teaching and learning provide multiple benefits from the point of view of teaching because it allows emphasizing or illustrating certain issues that are sometimes difficult to emphasize without such type of support. This is exactly the case for the tools to detect if there is any type of problem in a concurrent-c program. These tools provide interfaces that can complement the information given by a compiler with additional information about different types of race conditions and memory leaks that appear in the code. This article aims to address how to integrate a core validation tools for concurrent-c as a web application, allowing you to be accessible through the Internet. This tool has been evaluated in an existing programming course, which has shown to be able to provide additional information useful to the learner and the teacher. There have also been a number of performance measures to establish operational limits designed tool within a course that teaches concurrent-c programming.
We have investigated scintillation and thermally-stimulated luminescence (TSL) dosimetric properties of Al2O3 transparent ceramics doped with different concentrations of c ions (0.001, 0.01 and 0.1%). The samples were...
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We have investigated scintillation and thermally-stimulated luminescence (TSL) dosimetric properties of Al2O3 transparent ceramics doped with different concentrations of c ions (0.001, 0.01 and 0.1%). The samples were synthesized by the Spark Plasma Sintering (SPS) technique. All the samples showed scintillation with emission peaks at 310, 410 and 693 nm under X-ray irradiation. Based on the scintillation decay times measured, the origins of emissions at 310, 410 and 693 nm were attributed to F+ centers, F centers and cr3+ impurity ions, respectively. The samples show notable TSL with a glow curve consisting of peaks at 30, 100, 165, 230, 330 and 405 degrees c with much higher intensities than those of undoped Al2O3 transparent ceramics. A TSL response was confirmed to be linear to the irradiation dose over a range from 0.1 to 1000 mGy.
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