The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradi...
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The magnetic and electronic properties of the geometrically frustrated triangular antiferromagnet CuCrO2 are investigated by first principles through density functional theory calculations within the generalized gradient approxi- mations （GGA）＋U scheme. The spin exchange interactions up to the third nearest neighbours in the ab plane as well as the coupling between adjacent layers are calculated to examine the magnetism and spin frustration. It is found that CuCrO2 has a natural two-dimensional characteristic of the magnetic interaction. Using Monte Carlo simulation, we obtain the Neel temperature to be 29.9 K, which accords well with the experimental value of 24 K. Based on non- collinear magnetic structure calculations, we verify that the incommensurate spiral-spin structure with （110） spiral plane is believable for the magnetic ground state, which is consistent with the experimental observations. Due to intra-layer geometric spin frustration, parallel helical-spin chains arise along the a, b, or a＋ b directions, each with a screw-rotation angle of about I20°. Our calculations of the density of states show that the spin frustration plays an important role in the change of d-p hybridization, while the spin-orbit coupling has a very limited influence on the electronic structure.
The multiscale reinforcement and interfacial strengthening on epoxy-based composites by nanoscale complex composed of zero-dimensional silica nanoparticles (SiO 2 ) and one-dimensional multiwalled carbon nanotubes (MW...
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The multiscale reinforcement and interfacial strengthening on epoxy-based composites by nanoscale complex composed of zero-dimensional silica nanoparticles (SiO 2 ) and one-dimensional multiwalled carbon nanotubes (MWCNTs) was examined. The SiO 2 –MWCNT complex was successfully prepared by multi-step functionalization, which was characterized with FTIR, XPS and TEM. Mechanical properties of epoxy (EP) composites were significantly enhanced by SiO 2 –MWCNTs rather than other functionalized MWCNTs, due to synergy reinforcing effect of MWCNTs and SiO 2 as well as enlarged interfacial areas by SiO 2 . The chemically bonded nanoscale interfacial area between glass fiber and matrix was generated and bridged by SiO 2 –MWCNTs, making glass fiber like a branched reinforcement, resulting in strong interfacial adhesion and effective stress transfer. Mechanical properties of SiO 2 –MWCNT/EP composites and GF/SiO 2 –MWCNT/EP composites were even higher than those predicted by Halpin–Tsai model and rule of mixtures, resulting from strengthened interfacial adhesion in the composites, high chemical reactivity of SiO 2 –MWCNTs and additional reinforcing effect of SiO 2 .
Using one ray of light to encode another ray of light is highly desirable because information in optical format can be directly transferred from one beam to another without converting back to the electronic format. On...
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Using one ray of light to encode another ray of light is highly desirable because information in optical format can be directly transferred from one beam to another without converting back to the electronic format. One key medium to accomplish such an amazing task is photoswitchable molecules. Using bis(dithiazole)ethene that can be photoswitched between its ring‐open and ring‐closed states quantitatively with excellent fatigue resistance and high thermal stability, it is shown that quantitative photoreversibility allowed the photoswitching light to control other light travelling through the photoswitchable medium, a phenomenon of transferring information encoded in one light ray to others, thus imparting photo‐optical modulation on the orthogonal light beam.
A carbonization method is reported to improve the thermal conductivity of carbon nanotube (CNT) arrays. After being impregnated with phenolic resins, CNT arrays were carbonized at a temperature up to 1400°C. As a...
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A carbonization method is reported to improve the thermal conductivity of carbon nanotube (CNT) arrays. After being impregnated with phenolic resins, CNT arrays were carbonized at a temperature up to 1400°C. As a result, pyrolytic carbon was formed and connected non-neighboring CNTs. The pyrolysis improved the room temperature conductivity from below 2 W/m·K up to 11.8 and 14.6 W/m·K with carbonization at 800°C and 1400°C, respectively. Besides the light mass density of 1.1 g/cm3, the C/C composites demonstrated high thermal stability and a higher conductivity up to 21.4 W/m·K when working at 500°C.
A novel intumescent flame retardant was incorporated into polypropylene to prepare novel intumescent flame retardant composites (PP/IFR) with good flame retardant properties. The flame retardant mechanism was investig...
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A novel intumescent flame retardant was incorporated into polypropylene to prepare novel intumescent flame retardant composites (PP/IFR) with good flame retardant properties. The flame retardant mechanism was investigated by means of Laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis/infrared spectrometry (TGA-IR), Fourier Transform infrared spectroscopy (FTIR) and Energy Dispersive Spectrometer (EDS). It was found that the IFR could decrease the degradation rate of PP; the formed intumescent char was containing unorganized carbon structure and graphitic structure, and consisting of P, N, O and C elements. FTIR analysis showed that the network with P-O-P and P-O-C were formed. EDS analysis results revealed that some P elements were connected to the polyaromatic rings and could form huge connected network.
The effect of electropulsing treatment(EPT)on the microstructure and mechanical properties of the cold-rolled Mg-6Al-1Zn alloy strip was *** is found that EPT accelerated the recrystallization behaviour of the cold-ro...
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The effect of electropulsing treatment(EPT)on the microstructure and mechanical properties of the cold-rolled Mg-6Al-1Zn alloy strip was *** is found that EPT accelerated the recrystallization behaviour of the cold-rolled Mg-6Al-1Zn alloy strip at a relatively low temperature within a short time of 14 *** the temperature of EPT was 423 K,recovery of Mg matrix happened and fewβ-Mg17Al12 phaseprecipitated in the Mg *** increasing the temperature to 463 K,recrystallization occurred,accompanying dissolution ofβ-Mg17Al12 *** the temperature was increased to 483 K,complete recrystallization took place and obtained fine microstructure of quasi-single-phase-recrystallized *** elongation to failurewas increased from the 6.3%of the rolled strip to 23.5%,while the tensile strength was decreased from 368 MPa to 300 *** increasing the temperature of EPT,the apparent grain growth occurred and both the tensile strength and elongation to failure reduced.A mechanism for rapid recrystallization process during EPT was discussed.
Effect of isothermal annealing on the microstructure evolution of the cold-rolled Mg-9Al-1Zn alloy strip was *** is found that the competition between the precipitation ofβ-Mg17Al12 phase and recrystallization ofα-M...
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Effect of isothermal annealing on the microstructure evolution of the cold-rolled Mg-9Al-1Zn alloy strip was *** is found that the competition between the precipitation ofβ-Mg17Al12 phase and recrystallization ofα-Mg matrix occur under the conditions of various annealing temperature and *** a low annealing temperature(523K),theβ-Mg17Al12 particles precipitate preferentially at locally high deformation area and grow into the lamellar-cluster with an increase in the annealing time,retarding the recrystallization ofα-Mg *** raising the annealing temperature(573～623K),both the precipitation ofβ-Mg17Al12 particles and recrystallization ofα-Mg matrix take *** recrystallization and grain growth are prone to proceed without precipitation ofβ-Mg17Al12 particles when the annealing temperature is 673K.A mechanism for the competitive behavior between the precipitation ofβ-Mg17Al12 phase and recrystallization ofα-Mg matrix at various annealing conditions is discussed.
Titanate nanowires prepared by hydrothermal treatment of Ti02 in NaOH solution have attracted intensive attentions, but the formation mechanism is still under debate. Herein, we report an in-depth study on the formati...
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Titanate nanowires prepared by hydrothermal treatment of Ti02 in NaOH solution have attracted intensive attentions, but the formation mechanism is still under debate. Herein, we report an in-depth study on the formation mechanism through investigating the hydrothermal behavior of various Ti-containing precursors in basic solutions, including Ti, TiN, TiO2, Ti2SnC and Ti2AIN. Based on the results by means of X-ray diffraction （XRD）, transmission electron microscopy （TEM） and Raman spectroscopy, it is demonstrated that the crystal structure of the hydrothermal products is irrespective to the structure of the precursors or the types of basic solution （NaOH or KOH） in use. Alkali ions play an important role in the formation of titanate nanowires. The formation mechanism of the resultant titanate nanowires was proposed to be dissolution-crystallization mechanism.
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