Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate ...Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate due to carbon deposition or sintering.Single-atom Ni/CeO_(2)catalysts with suitable metalsupport interactions may provide a new strategy for developing highly active and coking-resistant nickel-based catalysts.In this work,we investigated the properties of the catalytic models of singleatom Ni loaded on CeO_(2)(111),CeO_(2)(110)and CeO_(2)(100),as well as their catalytic DRM performance with the density functional theory method(DFT).The interaction of CeO_(2)with different low-index crystal planes and single-atom Ni can be explained by the anchoring effect of surface O ions on Ni.Adsorption energies,growth patterns of Ni clusters,and migration studies of Ni atoms all indicate that the CeO_(2)(100)surface has the strongest anchoring effect on isolated Ni atoms,followed by the CeO_(2)(110)surface,with the CeO_(2)(111)surface being the weakest,Methane activation studies have shown that the activation ability of Ni_(1)/CeO_(2)(110)for methane strongly depends on the coordination environment of Ni,By contrast,methane activation by Ni on Ni_(1)/CeO_(2)(111)exhibits better activity and stability.Moreover,the Ni—CeO_(2)interaction correlates well with the DRM reaction performance.Interactions that are too strong anchor Ni atoms well but are not optimal for DRM activity.Ni_(1)/CeO_(2)(110)has relatively moderate interactions,promotes the^(*)CH_(4)→^(*)CH process,and has good resistance to carbon deposition.The metalsupport interaction-DRM reactivity(or stability)relationship is vital for the design of"super"highactivity and high-stability DRM catalysts.展开更多
Fischer-Tropsch synthesis （FTS） is an increasingly important approach for producing liquid fuels and chemicals via syngas-that is, synthesis gas, a mixture of carbon monoxide and hydrogen-generated from coal, natura...Fischer-Tropsch synthesis （FTS） is an increasingly important approach for producing liquid fuels and chemicals via syngas-that is, synthesis gas, a mixture of carbon monoxide and hydrogen-generated from coal, natural gas, or biomass. In FTS, dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles, which depend on the particle size, morphology, and crystallographic phase of the nanoparticles. In this article, we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active, selective, and stable FTS catalysts.展开更多
Calcium modified lead titanate nanocrystal material Pb0.85Ca0.15TiO3 was synthesized by means of a solgel method.The changes of crystal structure and grainsize of the samples were investigated under different conditio...Calcium modified lead titanate nanocrystal material Pb0.85Ca0.15TiO3 was synthesized by means of a solgel method.The changes of crystal structure and grainsize of the samples were investigated under different conditions of heat treatment.the results show that the tetragonal symmetry is reduced and the ferroelectricparaelectric phase transformation temperature is decreased with the reduce of the grainsize of the sample.the critical grainsize for the ferroelectricparaelectric phase transformation at room temperature was calculated.The change regularities of the lattice constant and tetragonality with the grainsize are discussed.展开更多
Based on the available experimental and compu- tational capabilities, a phenomenological approach has been proposed to formulate a hypersurface in both spatial and temporal domains to predict combined specimen size an...Based on the available experimental and compu- tational capabilities, a phenomenological approach has been proposed to formulate a hypersurface in both spatial and temporal domains to predict combined specimen size and load- ing rate effects on the material properties [ 1-2]. A systematic investigation is being performed to understand the combined size, rate and thermal effects on the properties and deformation patterns of representative materials with different nanos- tructures and under various types of loading conditions [3- 16]. The recent study on the single crystal copper response to impact loading has revealed the size-dependence of the Hugoniot curve. In this paper, the ＂inverse Hall-Petch＂ behavior as observed in the impact response of single crystal copper, which has not been reported in the open literature, is investigated by performing molecular dynamics simulations of the response of copper nanobeam targets subjected to impacts by copper nanobeam flyers with different impact velocities. It appears from the preliminary results that the ＂inverse Hall-Petch＂ behavior in single crystal copper is mainly due to the formation and evolution of disordered atoms and the interaction between ordered and disordered atoms, as compared with the physics behind the ＂inverse Hall-Petch＂behavior as observed in nanocrystalline materials展开更多
The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that t...The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that the Curie temperature(T_c) of Fe_(45)Cr_(15)Mo_(14)C_(15)B_6 Y_2 Ni_3 BMG with different annealing condition reaches a highest value of 95 K. The value of magnetic entropy change △S_M(T) of Sample 3 reaches a maxima of 0.48 J/(kg·K) at Tc temperature, which result from the interaction among the precipitated phases of(Fe,Cr)_(23)(C,B)_6, Fe_3 Mo_3 C and residual amorphous phase. Based on the experiment results, it can be obtained that the Curie temperature, magnetocaloric effect can reach their optimal value at low temperature, when the content of amorphous phase and precipitated phases type run up to certain value. The magnetic properties of Sample 1 with full amorphous phase and Sample 4 with full crystalline phase will both decrease.展开更多
Nickel-based single-crystal superalloys are the key materials for the manufacturing and development of advanced aeroengines. Rhenium is a crucial alloying element in the advanced nickel-based single-crystal superalloy...Nickel-based single-crystal superalloys are the key materials for the manufacturing and development of advanced aeroengines. Rhenium is a crucial alloying element in the advanced nickel-based single-crystal superalloys for its special strengthening effects. The addition of Re could effectively enhance the creep properties of the single-crystal superalloys; thus, the content of Re is considered as one of the characteristics in different-generation single-crystal superalloys. Owing to the fundamental importance of rhenium to nickel-based single-crystal superalloys, much progress has been made on understanding of the effect of rhenium in the single-crystal superalloys. While the effect of Re doping on the nickelbased superalloys is well documented, the origins of the socalled rhenium effect are still under debate. In this paper,the effect of Re doping on the single-crystal superalloys and progress in understanding the rhenium effect are reviewed. The characteristics of the d-states occupancy in the electronic structure of Re make it the slowest diffusion elements in the single-crystal superalloys, which is undoubtedly responsible for the rhenium effect, while the postulates of Re cluster and the enrichment of Re at the c/c0 interface are still under debate, and the synergistic action of Re with other alloying elements should be further studied.Additionally, the interaction of Re with interfacial dislocations seems to be a promising explanation for the rhenium effect. Finally, the addition of Ru could help suppress topologically close-packed（TCP） phase formation and strengthen the Re doping single-crystal superalloys.Understanding the mechanism of rhenium effect will be beneficial for the effective utilization of Re and the design of low-cost single-crystal superalloys.展开更多
A series of bowlic cyclotriveratrylenes（CTV） with peripheral groups with different lengths were synthesized.These compounds were investigated by diferential scanning calorimetry and hot stage coupled polarizing micr...A series of bowlic cyclotriveratrylenes（CTV） with peripheral groups with different lengths were synthesized.These compounds were investigated by diferential scanning calorimetry and hot stage coupled polarizing microscopy.Several CTV derivatives show thermotropic liquid crystalline properties.The experimental results of their thermotropic liquid crystalline behavior indicate that the clear points,the entropy changes of melting points,the crystallization temperatures,and their entropy changes all exhibited an evident odd-even effect except the melting points,which decreased monotonously with the increase of the length of the alkoxy groups.The parameter values of CTVs with even number carbon atoms were larger than those of CTVs with odd number.When the length of alkoxyl chains was even longer,a monotonous decrease occured.Nevertheless,in the case of the entropy changes of both melting points and crystallization temperatures,the effect was valid for all the six species,and therefore,the whole curves presented as a zig-zag form.展开更多
Organic field-effect transistors are of great importance to electronic devices.With the emergence of various preparation techniques for organic semiconductor materials,the device performance has been improved remarkab...Organic field-effect transistors are of great importance to electronic devices.With the emergence of various preparation techniques for organic semiconductor materials,the device performance has been improved remarkably.Among all of the organic materials,single crystals are potentially promising for high performances due to high purity and well-ordered molecular arrangement.Based on organic single crystals,alignment and patterning techniques are essential for practical industrial application of electronic devices.In this review,recently developed methods for crystal alignment and patterning are described.展开更多
Magnetization and magnetocaloric effect （MCE） of as-cast Gd-based bulk metallic glass （BMG） Gd24Er32Co24A120 and the crystallized samples were investigated. Reentrant-spin-glass-like behavior was observed in the a...Magnetization and magnetocaloric effect （MCE） of as-cast Gd-based bulk metallic glass （BMG） Gd24Er32Co24A120 and the crystallized samples were investigated. Reentrant-spin-glass-like behavior was observed in the as-cast sample. With increasing degree of crystallization, the magnetic frustration increased, which could be seen from the increased divergence of the zero-field-cooled and field-cooled magnetization behavior （i.e., the spin-glass-like freezing behavior）. The Curie temperature and magnetization decreased after crystallization. The as-cast BMG showed a large maximum magnetic entropy change （- △Sm） of 9.9 （J kg^-1 K^-1） under a field change of 5 T, which was comparable with that of Gd metal and other Gd-based metallic glasses. The maximum - △Sm reduced to 6.7 （J kg^-l K^-1） after crystallization, which was still superior to the Fe-/Co-based amorphous alloys. Their good MCE combining with high electrical resistivity, outstanding mechanical properties, tunable nature, and sufficiently soft magnetic property makes them to be attractive candidate for magnetic refrigerants in the low-temperature range.展开更多
[Zn(POM)_2Br_2](POM is 3-Methyl-4-Nitropyridine-1-Oxide),C_(12)H_(12)Br_2N_4O_6Zn, Mr=533.44,triclinic,P1,a=11.450(3),b=13.027(2),c=6.605(1),α=101.25(1),β=96.96(2), γ=108.06(2)°,V=901.2(4)~3,Z=2,D_c=1.97g·...[Zn(POM)_2Br_2](POM is 3-Methyl-4-Nitropyridine-1-Oxide),C_(12)H_(12)Br_2N_4O_6Zn, Mr=533.44,triclinic,P1,a=11.450(3),b=13.027(2),c=6.605(1),α=101.25(1),β=96.96(2), γ=108.06(2)°,V=901.2(4)~3,Z=2,D_c=1.97g·cm^(-3),(MoK_α)=0.71069,F(000)=520, μ=58.21cm^(-1),final R=0.040 for 2192 observed reflections,T=296K.The compound is a mononuclear complex,containing a tetrahedrally coordinated zinc atom.展开更多
In this paper, we examine the transmission of a probe field through a one dimensional photonic crystal (1DPC) when the sixth layer of the crystal is doped with four level atoms. We analyze effects of the external driv...In this paper, we examine the transmission of a probe field through a one dimensional photonic crystal (1DPC) when the sixth layer of the crystal is doped with four level atoms. We analyze effects of the external driving field on the passage of weak probe field across the photonic crystal. It is found that for the phase time delay of the probe photons, intensity of the driving field switches the Hartman effect from sub to superluminal character. It is interesting to note that in our model, the superluminal transmission of the probe pulse is accompanied by a negligibly small absorption of the incident beam. It ensures that the probe field does not attenuate while passing through the photonic crystal. A similar switching of the Hartman effect may be obtained by adjusting detuning of the probe field related to the excited states of the four-level doping atoms.展开更多
The effect of pressure on the variation of the crystallization phases of the Zr55Cu30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD) and different...The effect of pressure on the variation of the crystallization phases of the Zr55Cu30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mode of crystallization and products of crystallization of the Zr55Cu30Al10Ni5 bulk glass were quite different under different pressure. At ambient pressure, the crystallization products consisted of NiZr2 and CuZr2, while at pressure of 1 GPa and 3 GPa, the alloys crystallized into NiZr2 and Cu10Zr7, respectively. The alloy was nearly not crystallized and only a small amount of Cu10Zr7 was precipitated under 5 GPa. DSC proved that the mode of the crystallization under high pressure was different from that at ambient pressure.展开更多
The bimodal random crystal field （A） effects are investigated on the phase diagrams of spin-3/2 Ising model by using the effective-field theory with correlations based on two approximations： the general van der Wae...The bimodal random crystal field （A） effects are investigated on the phase diagrams of spin-3/2 Ising model by using the effective-field theory with correlations based on two approximations： the general van der Waerden identity and the approximated van der Waerden identity. In our approach, the crystal field is either turned on or turned off randomly for a given probability p or q = 1 -p, respectively. Then the phase diagrams are constructed on the （A,kT/J） and （p,kT/J） planes for given p and A, respectively, when the coordination number is z = 3. Furthermore, the effect of randomization of the crystal field is illustrated on the （△,kT/J） plane for p = 0.5 when z - 3,4, and 6. All these are carried out for both approximations and then the results are compared to point out the differences. In addition to the lines of second-order phase transitions, the model also exhibits first-order phase transitions and the lines of which terminate at the isolated critical points for high p values.展开更多
Sodium paranitrophenolate dihydrate (NPNa·2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single ...Sodium paranitrophenolate dihydrate (NPNa·2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single crystals of dimension upto 18 mm×6 mm×3 mm are obtained by isothermal solvent evaporation technique. The solubility of the crystal in different solvents was measured gravimetrically. The single crystals of NPNa·2H2O show variation in physical properties and growth rate in different solvents. Methanol or ethanol solution yields crystals of bipyramidal shape with clear morphology. However, methanol grown crystal is exhibiting improved hardness parameters and possesses excellent thermal stability as compared to water grown crystals. The effects of solvent on hardness parameter along with thermal and optical properties of NPNa·2H2O was revealed in this paper.展开更多
In this article,we review recently achieved Kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.With an increasing applied electric fi...In this article,we review recently achieved Kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.With an increasing applied electric field,the induced inplane birefringence of LCs shows quadratic nonlinearity.The theoretical calculations and experimental details are illustrated.With an enhanced Kerr constant to 130 nm/V2,this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.展开更多
The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 （KNN） crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. T...The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 （KNN） crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The full potentiallinearized augumented plane wave plus local orbitals （APW-LO） method and the supercell method are used in the calculation for the KNN crystal with and without the La doping. The results show that the piezoelectricity originates from the strong hybridization between the Nb atom and the O atom, and the substitution of the K or Na atom by the La impurity atom introduces the anisotropic relaxation and enhances the piezoelectricity at first and then restrains the hybridization of the Nb-O atoms when the La doping content further increases.展开更多
In this paper we study the gain saturation induced mode-coupling control in solid state ring laser devices based on the stimulated Raman effect of the polar crystals in.order to realize solid state ring laser gyroscop...In this paper we study the gain saturation induced mode-coupling control in solid state ring laser devices based on the stimulated Raman effect of the polar crystals in.order to realize solid state ring laser gyroscopes. We theoretically investigate the mode coupling induced by gain saturation between clockwise （CW） and counterclockwise （CCW） propa- gating laser modes. Because the CW and CCW running waves are pumped with counter-propagating lasers respectively, the independent coexistence can be ensured.展开更多
The quartz crystal microbalance（QCM） is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Contr...The quartz crystal microbalance（QCM） is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey＇s and Kanazawa＇s theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.展开更多
By using the re-derived formulae for both line-strength of electricdipole transition and simple J-mixing coefficients within the 4f shell in a rare-earthion, the spectroscopic properties of the luminescent material Eu...By using the re-derived formulae for both line-strength of electricdipole transition and simple J-mixing coefficients within the 4f shell in a rare-earthion, the spectroscopic properties of the luminescent material Eu3+ =Y2O3 and laser crystals Tb3+:=YAlO3 and Nd3+:YVO4, are investigated in detail. On the basis of three fitting Ω parameters and the effective reduced matrix elements, the spectral linestrengths, spontaneous emission probabilities, fluorescent branching ratios and lifetimeare calculated. The better agreement between theoretical results and experimental dataindicates the importance of J-mixing in the spectroscopic study of laser crystals.展开更多
基金Project supported by the Major Science and Technology Projects in Yunnan Province(202302AG050005)。
文摘Energy shortages and global warming are driving the focus on the greenhouse gases CH_(4)and CO_(2).The main reason why dry reforming of methane(DRM)has yet to be industrialized is its catalytic tendency to deactivate due to carbon deposition or sintering.Single-atom Ni/CeO_(2)catalysts with suitable metalsupport interactions may provide a new strategy for developing highly active and coking-resistant nickel-based catalysts.In this work,we investigated the properties of the catalytic models of singleatom Ni loaded on CeO_(2)(111),CeO_(2)(110)and CeO_(2)(100),as well as their catalytic DRM performance with the density functional theory method(DFT).The interaction of CeO_(2)with different low-index crystal planes and single-atom Ni can be explained by the anchoring effect of surface O ions on Ni.Adsorption energies,growth patterns of Ni clusters,and migration studies of Ni atoms all indicate that the CeO_(2)(100)surface has the strongest anchoring effect on isolated Ni atoms,followed by the CeO_(2)(110)surface,with the CeO_(2)(111)surface being the weakest,Methane activation studies have shown that the activation ability of Ni_(1)/CeO_(2)(110)for methane strongly depends on the coordination environment of Ni,By contrast,methane activation by Ni on Ni_(1)/CeO_(2)(111)exhibits better activity and stability.Moreover,the Ni—CeO_(2)interaction correlates well with the DRM reaction performance.Interactions that are too strong anchor Ni atoms well but are not optimal for DRM activity.Ni_(1)/CeO_(2)(110)has relatively moderate interactions,promotes the^(*)CH_(4)→^(*)CH process,and has good resistance to carbon deposition.The metalsupport interaction-DRM reactivity(or stability)relationship is vital for the design of"super"highactivity and high-stability DRM catalysts.
基金financial support by NWO-VICI and NWO-TOP grants awarded to Emiel J.M.Hensen
文摘Fischer-Tropsch synthesis （FTS） is an increasingly important approach for producing liquid fuels and chemicals via syngas-that is, synthesis gas, a mixture of carbon monoxide and hydrogen-generated from coal, natural gas, or biomass. In FTS, dispersed transition metal nanoparticles are used to catalyze the reactions underlying the formation of carbon-carbon bonds. Catalytic activity and selectivity are strongly correlated with the electronic and geometric structure of the nanoparticles, which depend on the particle size, morphology, and crystallographic phase of the nanoparticles. In this article, we review recent works dealing with the aspects of bulk and surface sensitivity of the FTS reaction. Understanding the different catalytic behavior in more detail as a function of these parameters may guide the design of more active, selective, and stable FTS catalysts.
文摘Calcium modified lead titanate nanocrystal material Pb0.85Ca0.15TiO3 was synthesized by means of a solgel method.The changes of crystal structure and grainsize of the samples were investigated under different conditions of heat treatment.the results show that the tetragonal symmetry is reduced and the ferroelectricparaelectric phase transformation temperature is decreased with the reduce of the grainsize of the sample.the critical grainsize for the ferroelectricparaelectric phase transformation at room temperature was calculated.The change regularities of the lattice constant and tetragonality with the grainsize are discussed.
基金supported in part by the U.S.Defense Threat Reduction Agency(HDTRA1-10-1-0022)the National Key Basic Research Special Foundation of China(2010CB832704)+2 种基金the National Natural Science Foundation of China(10721062)the 111 Joint Program by the Chinese Ministry of EducationState Administration of Foreign Experts Affairs(B08014)
文摘Based on the available experimental and compu- tational capabilities, a phenomenological approach has been proposed to formulate a hypersurface in both spatial and temporal domains to predict combined specimen size and load- ing rate effects on the material properties [ 1-2]. A systematic investigation is being performed to understand the combined size, rate and thermal effects on the properties and deformation patterns of representative materials with different nanos- tructures and under various types of loading conditions [3- 16]. The recent study on the single crystal copper response to impact loading has revealed the size-dependence of the Hugoniot curve. In this paper, the ＂inverse Hall-Petch＂ behavior as observed in the impact response of single crystal copper, which has not been reported in the open literature, is investigated by performing molecular dynamics simulations of the response of copper nanobeam targets subjected to impacts by copper nanobeam flyers with different impact velocities. It appears from the preliminary results that the ＂inverse Hall-Petch＂ behavior in single crystal copper is mainly due to the formation and evolution of disordered atoms and the interaction between ordered and disordered atoms, as compared with the physics behind the ＂inverse Hall-Petch＂behavior as observed in nanocrystalline materials
基金supported by the National Natural Science Foundation of China(51741105)
文摘The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that the Curie temperature(T_c) of Fe_(45)Cr_(15)Mo_(14)C_(15)B_6 Y_2 Ni_3 BMG with different annealing condition reaches a highest value of 95 K. The value of magnetic entropy change △S_M(T) of Sample 3 reaches a maxima of 0.48 J/(kg·K) at Tc temperature, which result from the interaction among the precipitated phases of(Fe,Cr)_(23)(C,B)_6, Fe_3 Mo_3 C and residual amorphous phase. Based on the experiment results, it can be obtained that the Curie temperature, magnetocaloric effect can reach their optimal value at low temperature, when the content of amorphous phase and precipitated phases type run up to certain value. The magnetic properties of Sample 1 with full amorphous phase and Sample 4 with full crystalline phase will both decrease.
基金financially supported by the National Basic Research Program of China(No.2009CB623701)the National Natural Science Foundation of China(Nos.11374174,50971075 and 51390471)
文摘Nickel-based single-crystal superalloys are the key materials for the manufacturing and development of advanced aeroengines. Rhenium is a crucial alloying element in the advanced nickel-based single-crystal superalloys for its special strengthening effects. The addition of Re could effectively enhance the creep properties of the single-crystal superalloys; thus, the content of Re is considered as one of the characteristics in different-generation single-crystal superalloys. Owing to the fundamental importance of rhenium to nickel-based single-crystal superalloys, much progress has been made on understanding of the effect of rhenium in the single-crystal superalloys. While the effect of Re doping on the nickelbased superalloys is well documented, the origins of the socalled rhenium effect are still under debate. In this paper,the effect of Re doping on the single-crystal superalloys and progress in understanding the rhenium effect are reviewed. The characteristics of the d-states occupancy in the electronic structure of Re make it the slowest diffusion elements in the single-crystal superalloys, which is undoubtedly responsible for the rhenium effect, while the postulates of Re cluster and the enrichment of Re at the c/c0 interface are still under debate, and the synergistic action of Re with other alloying elements should be further studied.Additionally, the interaction of Re with interfacial dislocations seems to be a promising explanation for the rhenium effect. Finally, the addition of Ru could help suppress topologically close-packed（TCP） phase formation and strengthen the Re doping single-crystal superalloys.Understanding the mechanism of rhenium effect will be beneficial for the effective utilization of Re and the design of low-cost single-crystal superalloys.
基金Supported by the National Natural Science Foundation of China(No.20774077)the Natural Science Foundation of Fujian Province,China(No.E0510003, E0710025)the Project of Science and Technology of Xiamen City,China(No.3502Z20055013)
文摘A series of bowlic cyclotriveratrylenes（CTV） with peripheral groups with different lengths were synthesized.These compounds were investigated by diferential scanning calorimetry and hot stage coupled polarizing microscopy.Several CTV derivatives show thermotropic liquid crystalline properties.The experimental results of their thermotropic liquid crystalline behavior indicate that the clear points,the entropy changes of melting points,the crystallization temperatures,and their entropy changes all exhibited an evident odd-even effect except the melting points,which decreased monotonously with the increase of the length of the alkoxy groups.The parameter values of CTVs with even number carbon atoms were larger than those of CTVs with odd number.When the length of alkoxyl chains was even longer,a monotonous decrease occured.Nevertheless,in the case of the entropy changes of both melting points and crystallization temperatures,the effect was valid for all the six species,and therefore,the whole curves presented as a zig-zag form.
基金supported by the 973 Program(No.2014CB643503)National Natural Science Foundation of China(Nos.51373150,51461165301)Zhejiang Province Natural Science Foundation(No.LZ13E030002)
文摘Organic field-effect transistors are of great importance to electronic devices.With the emergence of various preparation techniques for organic semiconductor materials,the device performance has been improved remarkably.Among all of the organic materials,single crystals are potentially promising for high performances due to high purity and well-ordered molecular arrangement.Based on organic single crystals,alignment and patterning techniques are essential for practical industrial application of electronic devices.In this review,recently developed methods for crystal alignment and patterning are described.
文摘Magnetization and magnetocaloric effect （MCE） of as-cast Gd-based bulk metallic glass （BMG） Gd24Er32Co24A120 and the crystallized samples were investigated. Reentrant-spin-glass-like behavior was observed in the as-cast sample. With increasing degree of crystallization, the magnetic frustration increased, which could be seen from the increased divergence of the zero-field-cooled and field-cooled magnetization behavior （i.e., the spin-glass-like freezing behavior）. The Curie temperature and magnetization decreased after crystallization. The as-cast BMG showed a large maximum magnetic entropy change （- △Sm） of 9.9 （J kg^-1 K^-1） under a field change of 5 T, which was comparable with that of Gd metal and other Gd-based metallic glasses. The maximum - △Sm reduced to 6.7 （J kg^-l K^-1） after crystallization, which was still superior to the Fe-/Co-based amorphous alloys. Their good MCE combining with high electrical resistivity, outstanding mechanical properties, tunable nature, and sufficiently soft magnetic property makes them to be attractive candidate for magnetic refrigerants in the low-temperature range.
文摘[Zn(POM)_2Br_2](POM is 3-Methyl-4-Nitropyridine-1-Oxide),C_(12)H_(12)Br_2N_4O_6Zn, Mr=533.44,triclinic,P1,a=11.450(3),b=13.027(2),c=6.605(1),α=101.25(1),β=96.96(2), γ=108.06(2)°,V=901.2(4)~3,Z=2,D_c=1.97g·cm^(-3),(MoK_α)=0.71069,F(000)=520, μ=58.21cm^(-1),final R=0.040 for 2192 observed reflections,T=296K.The compound is a mononuclear complex,containing a tetrahedrally coordinated zinc atom.
基金Supported in part by the National Natural Science Foundation of China under Grant Nos.11274132 and 11750110411
文摘In this paper, we examine the transmission of a probe field through a one dimensional photonic crystal (1DPC) when the sixth layer of the crystal is doped with four level atoms. We analyze effects of the external driving field on the passage of weak probe field across the photonic crystal. It is found that for the phase time delay of the probe photons, intensity of the driving field switches the Hartman effect from sub to superluminal character. It is interesting to note that in our model, the superluminal transmission of the probe pulse is accompanied by a negligibly small absorption of the incident beam. It ensures that the probe field does not attenuate while passing through the photonic crystal. A similar switching of the Hartman effect may be obtained by adjusting detuning of the probe field related to the excited states of the four-level doping atoms.
文摘The effect of pressure on the variation of the crystallization phases of the Zr55Cu30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mode of crystallization and products of crystallization of the Zr55Cu30Al10Ni5 bulk glass were quite different under different pressure. At ambient pressure, the crystallization products consisted of NiZr2 and CuZr2, while at pressure of 1 GPa and 3 GPa, the alloys crystallized into NiZr2 and Cu10Zr7, respectively. The alloy was nearly not crystallized and only a small amount of Cu10Zr7 was precipitated under 5 GPa. DSC proved that the mode of the crystallization under high pressure was different from that at ambient pressure.
文摘The bimodal random crystal field （A） effects are investigated on the phase diagrams of spin-3/2 Ising model by using the effective-field theory with correlations based on two approximations： the general van der Waerden identity and the approximated van der Waerden identity. In our approach, the crystal field is either turned on or turned off randomly for a given probability p or q = 1 -p, respectively. Then the phase diagrams are constructed on the （A,kT/J） and （p,kT/J） planes for given p and A, respectively, when the coordination number is z = 3. Furthermore, the effect of randomization of the crystal field is illustrated on the （△,kT/J） plane for p = 0.5 when z - 3,4, and 6. All these are carried out for both approximations and then the results are compared to point out the differences. In addition to the lines of second-order phase transitions, the model also exhibits first-order phase transitions and the lines of which terminate at the isolated critical points for high p values.
文摘Sodium paranitrophenolate dihydrate (NPNa·2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single crystals of dimension upto 18 mm×6 mm×3 mm are obtained by isothermal solvent evaporation technique. The solubility of the crystal in different solvents was measured gravimetrically. The single crystals of NPNa·2H2O show variation in physical properties and growth rate in different solvents. Methanol or ethanol solution yields crystals of bipyramidal shape with clear morphology. However, methanol grown crystal is exhibiting improved hardness parameters and possesses excellent thermal stability as compared to water grown crystals. The effects of solvent on hardness parameter along with thermal and optical properties of NPNa·2H2O was revealed in this paper.
基金The funding for the State Key Laboratory on Advanced Displays and Optoelectronics Technologies
文摘In this article,we review recently achieved Kerr effect progress in novel liquid crystal（LC） material：vertically aligned deformed helix ferroelectric liquid crystal（VADHFLC）.With an increasing applied electric field,the induced inplane birefringence of LCs shows quadratic nonlinearity.The theoretical calculations and experimental details are illustrated.With an enhanced Kerr constant to 130 nm/V2,this VADHFLC cell can achieve a 2π modulation by a small efficient electric field with a fast response around 100 μs and thus can be employed in both display and photonics devices.
基金supported by National Nature Science Foundation of China (No.11075110)
文摘The La-dopping effect on the piezoelectricity in the K0.5Na0.5NbO3 （KNN） crystal with a tetragonal phase is investigated for the first time using the first-principle calculation based on density functional theory. The full potentiallinearized augumented plane wave plus local orbitals （APW-LO） method and the supercell method are used in the calculation for the KNN crystal with and without the La doping. The results show that the piezoelectricity originates from the strong hybridization between the Nb atom and the O atom, and the substitution of the K or Na atom by the La impurity atom introduces the anisotropic relaxation and enhances the piezoelectricity at first and then restrains the hybridization of the Nb-O atoms when the La doping content further increases.
文摘In this paper we study the gain saturation induced mode-coupling control in solid state ring laser devices based on the stimulated Raman effect of the polar crystals in.order to realize solid state ring laser gyroscopes. We theoretically investigate the mode coupling induced by gain saturation between clockwise （CW） and counterclockwise （CCW） propa- gating laser modes. Because the CW and CCW running waves are pumped with counter-propagating lasers respectively, the independent coexistence can be ensured.
基金supported by the National Natural Science Foundation of China(Grant No.61672094)
文摘The quartz crystal microbalance（QCM） is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey＇s and Kanazawa＇s theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.
文摘By using the re-derived formulae for both line-strength of electricdipole transition and simple J-mixing coefficients within the 4f shell in a rare-earthion, the spectroscopic properties of the luminescent material Eu3+ =Y2O3 and laser crystals Tb3+:=YAlO3 and Nd3+:YVO4, are investigated in detail. On the basis of three fitting Ω parameters and the effective reduced matrix elements, the spectral linestrengths, spontaneous emission probabilities, fluorescent branching ratios and lifetimeare calculated. The better agreement between theoretical results and experimental dataindicates the importance of J-mixing in the spectroscopic study of laser crystals.
