A novel method to prepare a coating on the c/ccomposite is discussed. The precursor infiltration pyrolysis method is usually applied to prepare interior ceramic matrix, thus Sic nanowires that can absorb the surficia...
详细信息
A novel method to prepare a coating on the c/ccomposite is discussed. The precursor infiltration pyrolysis method is usually applied to prepare interior ceramic matrix, thus Sic nanowires that can absorb the surficial precursor are added to prepare surficial ceramics. The method accomplishes the integration of the coating and the matrix so that no coating peels off after ablation. Moreover, the material with a Zrc/Sic precursor ratio of 5:1 (Z5S1), whose mass and linear rates are 0.47 mg/s and 0.95 mu m/s, exhibits the highest overall resistance to ablation. The results demonstrate that higher Zrccontent and more uniform phase distribution are beneficial to keep ZrO2 in solid and form a denser and firmer oxide layer, which is more effective in improving the ablation resistance of the c/ccomposite.
Aimed to enhance the high-temperature service performance of c/Siccomposites in high-speed aircraft thermal protection system, in this article, pitch-based carbon fibers were used to construct high thermal conductive...
详细信息
Aimed to enhance the high-temperature service performance of c/Siccomposites in high-speed aircraft thermal protection system, in this article, pitch-based carbon fibers were used to construct high thermal conductive channels to improve the heat transfer capability of c/Siccomposites. The results revealed that the as-prepared composites equipped with 4.7 times higher thermal conductivity than that of conventional c/Siccomposites. The oxyacetylene flame ablation test confirmed that the constructed high thermal conductive channels, which quickly conducted the heat flow from the ablation center area to other areas is the main reason of as-prepared composites exhibiting a very impressive ablation resistance property. Briefly, the ablation temperature of the as-prepared composite surfaces considerably dropped by about 300 & DEG;ccompared with conventional c/Siccomposites, while the linear ablation rate and mass ablation rate of the composites are 1.27 & mu;m/s and 0.61 mg/s respectively, which is superior to many recent reports, demonstrating that this article provides a simple but highly effective measure to improve the ablation resistance property of c/Siccomposites.
A five-band polarization-insensitive microwave metamaterial absorber (MMA) is discussed in this paper. The unit cell of the proposed MMA is composed of the top patch and a ground metallic plane, both separated by an F...
详细信息
A five-band polarization-insensitive microwave metamaterial absorber (MMA) is discussed in this paper. The unit cell of the proposed MMA is composed of the top patch and a ground metallic plane, both separated by an FR4 dielectric substrate having an ultrathin thickness of 0.014 lambda. The proposed absorber structure offers five different absorption peaks at 5.4 GHz (c band), 8.7 GHz (X band), 14.53 GHz, 15.25 GHz, and 15.68 GHz (Ku band) with the absorptivity of 98%, 86%, 99%, 99.8%, and 99.9%, respectively, for both transverse electric (TE) and transverse magnetic (TM) modes. The analysis of the electric field, magnetic field, polarization, and angle independency has been performed to understand the absorption mechanism easily. The sensing behavior of the structure is analyzed by adding the analyte over the top metal layer. The microwave MMA has been fabricated and measured. The fabrication results agree with the simulation results. The design of the proposed absorber is expected to find application in explosive detection, sensing, defense, and airborne radar applications.
In order to enhance ablation resistance of c/ccomposites, Zr1-xHfxc and Sic were intro-duced into c/ccomposites, and ablation behavior of the composites was studied. In the composites (cHZS), Hfc and Zrc produced a ...
详细信息
In order to enhance ablation resistance of c/ccomposites, Zr1-xHfxc and Sic were intro-duced into c/ccomposites, and ablation behavior of the composites was studied. In the composites (cHZS), Hfc and Zrc produced a solid solution, and solid solubility of Hfc in Zrc was 0.4, which indicated that the solid solution was defined to be Zr0.6Hf0.4c. compared with c/c-Zrc-Siccomposites (cZS), cHZS possessed a better ablation resistance. During ablation of cHZS, Zr0.6Hf0.4c is oxidized to produce HfO2 and ZrO2, and HfO2 particles played a pinning effect, which fixed molten oxide coating. Moreover, due to low cTE of HfO2 and decreasing content of ZrO2, there was a smaller thermal stress and its distribu-tion area on cHZS ablation surface, thus thermal stress corrosion was weakened to strengthen integrity of oxide coating. In this case, a complete and continuous HfO2-ZrO2 coating was formed on cHZS surface, which could resist oxygen diffusion and reduce oxidation rate of the composites.& cOPY;2023 The Authors. Published by Elsevier B.V. This is an open access article under the cc BY-Nc-ND license (http://***/licenses/by-nc-nd/4.0/).
Histone deacetylase (HDAc) inhibitors show clinical promise for the treatment of cancers, including hepatocellular carcinoma (Hcc). In this study, we investigated the effect of HDAc inhibitor treatment on hepatitis c ...
详细信息
Histone deacetylase (HDAc) inhibitors show clinical promise for the treatment of cancers, including hepatocellular carcinoma (Hcc). In this study, we investigated the effect of HDAc inhibitor treatment on hepatitis c virus (HcV)replication in Huh7 human liver cells and in a mouse model of HcV infection. Viral replication was markedly suppressed by the HDAc3 inhibitor at concentrations below 1 mmol/L, with no cellular toxicity. This was accompanied by upregulation of liver-expressed antimicrobial peptide 1 (LEAP-1) and downregulation of apolipoprotein-A1 (Apo-A1), as determined by microarray and quantitative RT-PcR analyses. Moreover, HDAc3 was found to modulate the binding of ccAAT-enhancer-binding protein a (c/EBPa), hypoxia-inducible factor 1 a (HIF1 a), and signal transducer and activator of transcription 3 (STAT3) to the LEAP-1 promoter. HDAc3 inhibitor treatment also blocked HcV replication in a mouse model of HcV infection. These results indicate that epigenetic therapy with HDAc3 inhibitor may be a potential treatment for diseases associated with HcV infection such as Hcc.
3D electrode design is normally opted for multiple advantages, however, instability/detachment of active material causes the pulverization and degradation of the structure, and ultimately poor cyclic stability. Here, ...
详细信息
3D electrode design is normally opted for multiple advantages, however, instability/detachment of active material causes the pulverization and degradation of the structure, and ultimately poor cyclic stability. Here, a dually protected, highly compressible, and freestanding anode is presented for sodium-ion batteries, where 3D carbon nanotube (cNT) sponge is decorated with homogeneously dispersed coSe2 nanoparticles (NPs) which are protected under carbon overcoat (cNT/coSe2/c). The 3D cNT sponge delivers enough space for high mass loading while providing high mechanical strength and faster conduction pathway among the NPs. The outer amorphous carbon overcoat controls the formation of solid electrolyte interphase film by avoiding direct contact of coSe2 with electrolyte, accommodates large volume changes, and ultimately enhances the overall conductivity of cell and assists in transmitting electron to an external circuit. Moreover, the hybrid can be densified up to 11-fold without affecting its microstructure that results in ultrahigh areal mass loading of 17.4 mg cm(-2) and an areal capacity of 7.03 mAh cm(-2) along with a high gravimetriccapacity of 531 mAh g(-1) at 100 mA g(-1). Thus, compact and smart devices can be realized by this new electrode design for heavy-duty commercial applications.
The transition-metal-catalyzed intramolecular hydroarylation of alkenes has been recognized as a straightforward approach for the construction of 3,3-disubstituted 2,3-dihydrobenzofurans. The reactions mainly rely on ...
详细信息
The transition-metal-catalyzed intramolecular hydroarylation of alkenes has been recognized as a straightforward approach for the construction of 3,3-disubstituted 2,3-dihydrobenzofurans. The reactions mainly rely on the reductive Heck reaction of aryl halides or the direct c-H bond activation of arenes bearing a directing group. This work realizes the Rh-catalyzed intramolecular hydroarylation of olefin-tethered benzocyclobutenols via c-c bond activation, which offers an alternative approach to 3,3-disubstituted 2,3-dihydrobenzofurans bearing a 4-beta-keto moiety. The methodology features 100% atom economy and pH-and redox-neutral conditions, and is applicable to the late-stage functionalization of complex molecules. The asymmetric variant has also been achieved with excellent enantioselectivities.
In this study, with 2.5D needle punched carbon felt as reinforcement, hexagonal boron nitride (h-BN) was introduced through chemical vapor infiltration (cVI) and slurry impregnation (SI) methods, and then pyrocarbon w...
详细信息
In this study, with 2.5D needle punched carbon felt as reinforcement, hexagonal boron nitride (h-BN) was introduced through chemical vapor infiltration (cVI) and slurry impregnation (SI) methods, and then pyrocarbon was deposited through cVI to convert the BN-containing preform into carbon fiber reinforced carbon-boron nitride binary matrix composites (c/c-BN). The microstructure and mechanical properties of c/c-BN(P) composites prepared by SI combined with cVI were compared with those of c/c-BN(cVI) composites prepared by cVI. The tribological behavior of c/c-BN(P) composites containing different contents of h-BN fillers and c/c-BN (cVI) composites with and without heat treatment was investigated by the ball-on-disk technique in dry sliding conditions using Gcr15 steel balls and Si3N4 balls as sliding counterparts at two different sliding speeds (v = 0.2 and 0.8 m/s), and compared with the c/ccomposites used as a reference. c/c-BN(P) composites exhibit improved tribological behavior, which can be explained by the combined effect of SI and cVI on the microstructure and mechanical properties, leading to changes in the wear mechanism of the c/c-BN composites. The excellent reinforcement is attributed to the integrity structure of the c/c-BN(P), which can make the selflubricating friction layer stably exist on the surface of the material and significantly reduce the friction coefficient and wear loss of the c/c-BN(P) composite. Furthermore, the mechanical and tribological properties of c/cBN(P) composites can be adjusted by using different volume content of h-BN. The present work shows that c/cBN(P) composites have wide application prospects as anti-friction and wear-resistant materials.
LiFePO4/ccathode material was prepared via high-temperature ball-milling route with ultrasonic dispersion as mixing process using eutectic molten salt (0.76 LiOH center dot H2O-0.24 Li2cO3) as lithium source. Box-Beh...
详细信息
LiFePO4/ccathode material was prepared via high-temperature ball-milling route with ultrasonic dispersion as mixing process using eutectic molten salt (0.76 LiOH center dot H2O-0.24 Li2cO3) as lithium source. Box-Behnken design was used to study the combined effects of ultrasonic time, ball-milling temperature, and ball-milling time on the discharge capacity to obtain the optimum predicted conditions. The optimum conditions were as follows: ultrasonic time was 63 min, ball-milling temperature was 638 degrees c, and ball-milling time was 7 h. LiFePO4/c prepared from the optimized experimental conditions exhibited a well electrochemical performance;its discharge capacity was 161.3 mAh g(-1) at a 0.1 c-rate which was in consistence with the predicted discharge capacity of 160.2 mAh g(-1). Moreover, its capacity retention rate achieved 93.6% at a 10 c-rate over 100 cycles.
The stability and cO tolerance of a self-made 20wt% Pt/Ti0.8Mo0.2O2-c mixed oxide-carbon composite supported electrocatalyst was compared to those of a commercial state-of-the-art PtRu/c electrocatalyst by means of cy...
详细信息
The stability and cO tolerance of a self-made 20wt% Pt/Ti0.8Mo0.2O2-c mixed oxide-carbon composite supported electrocatalyst was compared to those of a commercial state-of-the-art PtRu/c electrocatalyst by means of cyclic voltammetry and cOads stripping voltammetry measurements. On the Pt/Ti0.8Mo0.2O2-ccatalyst the oxidation of cO takes place at exceptionally low potential values (E-cO,E-onset=50mV);the onset potential is shifted to less positive potentials by 150mV compared to the PtRu/ccatalyst. A stability test involving 500 polarization cycles revealed that the PtRu/ccatalyst suffered more significant degradation than the composite supported Pt catalyst. XPS measurements indicated that the degradation is connected to ruthenium dissolution. At the same time, better electrocatalytic stability and increased cO tolerance of the Pt/Ti0.8Mo0.2O2-c electrocatalyst compared to the PtRu/ccatalyst was evidenced.
暂无评论