Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation ac...Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation activity were studied.Several different carbon materi-als were produced from them by oxida-tion in air(350℃,300 mL/min)fol-lowed by carbonization(1000℃ in Ar),and the effect of the cross-linked structure on their structure and sodium storage properties was investigated.The results showed that the two pitch fractions were obviously different after the air oxidation.The TS fraction with a low degree of condensation and abundant side chains had a stronger oxidation activity and thus introduced more cross-linked oxygen-containing functional groups C(O)―O which prevented carbon layer rearrangement during the carbonization.As a result,a disordered hard carbon with more defects was formed,which improved the electrochemical performance.Therefore,the carbon materials derived from TS(O-TS-1000)had an obvious disordered structure and a larger layer spacing,giving them better sodium storage perform-ance than those derived from the TI-PS fraction(O-TI-PS-1000).The specific capacity of O-TS-1000 was about 250 mAh/g at 20 mA/g,which was 1.67 times higher than that of O-TI-PS-1000(150 mAh/g).展开更多
A 16-channel arrayed waveguide grating(AWG)with an 800 GHz channel spacing in the O-band has been developed and fabricated based on silica planar lightwave circuit(PLC)technology.By extending the wave⁃length allocatio...A 16-channel arrayed waveguide grating(AWG)with an 800 GHz channel spacing in the O-band has been developed and fabricated based on silica planar lightwave circuit(PLC)technology.By extending the wave⁃length allocation from 8 channels to 16 channels as specified in IEEE 802.3bs,we increased the number of chan⁃nels and boosted transmission capacity to meet the 1.6 Tbps and higher-speed signal transmission requirements for future data centers.Through optimizing the AWG structure,it has achieved insertion loss(IL)better than-1.61 dB,loss uniformity below 0.35 dB,polarization-dependent loss(PDL)below 0.35 dB,adjacent channel cross⁃talk under-20.05 dB,ripple less than 0.75 dB,center wavelength offset under 0.22 nm and 1 dB bandwidth ex⁃ceeding 2.88 nm.The AWG has been successfully measured to transmit 53 Gbaud 4-level pulse amplitude modu⁃lation(PAM4)signal per channel and the total transmission speed can reach over 1.6 Tbps.展开更多
This data set collects,compares and contrasts the capacities and structures of a series of hard carbon materials,and then searches for correlations between structure and electrochemical performance.The capacity data o...This data set collects,compares and contrasts the capacities and structures of a series of hard carbon materials,and then searches for correlations between structure and electrochemical performance.The capacity data of the hard carbons were obtained by charge/discharge tests and the materials were characterized by XRD,gas adsorption,true density tests and SAXS.In particular,the fitting of SAXS gave a series of structural parameters which showed good characterization.The related test details are given with the structural data of the hard carbons and the electrochemical performance of the sodium-ion batteries.展开更多
In order to meet the urgent need of infrared search and track applications for accurate identification and positioning of infrared guidance aircraft,an active-detection mid-wave infrared search and track system(ADMWIR...In order to meet the urgent need of infrared search and track applications for accurate identification and positioning of infrared guidance aircraft,an active-detection mid-wave infrared search and track system(ADMWIRSTS)based on"cat-eye effect"was developed.The ADMWIRSTS mainly consists of both a light beam control subsystem and an infrared search and track subsystem.The light beam control subsystem uses an integrated opto-mechanical two-dimensional pointing mirror to realize the control function of the azimuth and pitch directions of the system,which can cover the whole airspace range of 360°×90°.The infrared search and track subsystem uses two mid-wave infrared cooled 640×512 focal plane detectors for co-aperture beam expanding,infrared and illumination laser beam combining,infrared search,and two-stage track opto-mechanical design.In this work,the system integration design and structural finite-element analysis were conducted,the search imaging and two-stage track imaging for external scenes were performed,and the active-detection technologies were experimentally verified in the laboratory.The experimental investigation results show that the system can realize the infrared search and track imaging,and the accurate identification and positioning of the mid-wave infrared guidance,or infrared detection system through the echo of the illumination laser.The aforementioned work has important technical significance and practical application value for the development of compactly-integrated high-precision infrared search and track,and laser suppression system,and has broad application prospects in the protection of equipment,assets and infrastructures.展开更多
Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application,especially for selection of suita...Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application,especially for selection of suitable dielectric materials for high-power microwave transmission devices and reliable power transmission.Pure magnesium oxide(MgO),a kind of ceramic dielectric material,possesses great application potential in high-power microwave transmission devices due to its high theoretical dielectric strength,low dielectric constant,and low dielectric loss properties,but its application is limited by high sintering temperature during preparation.This work presented the preparation of a new type of multiphase ceramics based on MgO,which was MgO-1%ZrO_(2)-1%CaCO_(3-x)%MnCO_(3)(MZCM_(x),x=0,0.25,0.50,1.00,1.50,in molar),and their phase structures,morphological features,and dielectric properties were investigated.It was found that inclusion of ZrO_(2) and CaCO_(3) effectively inhibited excessive growth of MgO grains by formation of second phase,while addition of MnCO_(3) promoted the grain boundary diffusion process during the sintering process and reduced activation energy for the grain growth,resulting in a lower ceramic sintering temperature.Excellent performance,including high dielectric strength(Eb=92.3 kV/mm)and quality factor(Q×f=216642 GHz),simultaneously accompanying low dielectric loss(<0.03%),low temperature coefficient of dielectric constant(20.3×10^(–6)℃^(–1),85℃)and resonance frequency(–12.54×10^(–6)℃^(–1)),was achieved in MZCM1.00 ceramics under a relatively low sintering temperature of 1350℃.This work offers an effective solution for selecting dielectric materials for high-power microwave transmission devices.展开更多
Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors,particularly in terms of their high-frequency response.However,the charge storage and electrolyte ion response me...Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors,particularly in terms of their high-frequency response.However,the charge storage and electrolyte ion response mechanisms of different nitrogen dopants at high frequencies are still unclear.In this study,melamine foam carbons with different configurations of surfacedoped N were formed by gradient carbonization,and the effects of the configurations on the high-frequency response behavior of the supercapacitors were analyzed.Using a combination of experiments and first-principle calculations,we found that pyrrolic N,characterized by a higher adsorption energy,increases the charge storage capacity of the electrode at high frequencies.On the other hand,graphitic N,with a lower adsorption energy,increases the speed of ion response.We propose the use of adsorption energy as a practical descriptor for electrode/electrolyte design in high-frequency applications,offering a more universal approach for improving the performance of N-doped carbon materials in supercapacitors.展开更多
ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to...ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to the conventional preparation method,reactive synthesis allows for the more facile production of ultra-high temperature ceramics with fine particle size and homogeneous composition.In this work,ZrSi_(2),B4C,and C were used as raw materials to prepare ZrB_(2)-SiC via combination of tape casting and reactive melt infiltration herein referred to as ZBC ceramics.Control sample of ZrB_(2)-SiC was also prepared using ZrB_(2)and SiC as raw materials through an identical process designated as ZS ceramics.Microscopic analysis of both ceramic groups revealed smaller and more uniformly distributed particles of the ZrB_(2)phase in ZBC ceramics compared to the larger particles in ZS ceramics.Both sets of ceramics underwent cyclic oxidation testing in the air at 1600℃for a cumulative duration of 5 cycles,each cycle lasting 2 h.Analysis of the oxidation behavior showed that both ZBC ceramics and ZS ceramics developed a glassy SiO_(2)-ZrO_(2)oxide layer on their surfaces during the oxidation.This layer severed as a barrier against oxygen.In ZBC ceramics,ZrO_(2)is finely distributed in SiO_(2),whereas in ZS ceramics,larger ZrO_(2)particles coexist with glassy SiO_(2).The surface oxide layer of ZBC ceramics maintains a dense structure because the well-dispersed ZrO_(2)increases the viscosity of glassy SiO_(2),preventing its crystallization during the cooling.Conversely,some SiO_(2)in the oxide layer of ZS ceramics may crystallize and form a eutectic with ZrO_(2),leading to the formation of ZrSiO_(4).This leads to cracking of the oxide layer due to differences in thermal expansion coefficients,weakening its barrier effect.An analysis of the oxidation resistance shows that ZBC ceramics exhibit less increase in oxide layer thickness and mass compared to ZS ceramics,suggesting superior oxidation resistance of ZBC ceramics.展开更多
(Gd,Lu)_(2)O_(3)∶Eu scintillation ceramics have promising applications in the high-energy X-ray imaging.Eu0.1Gd0.6Lu1.3O3 nano-powders with pure phase were prepared from the precursor calcined at 1050℃for 4 h by the...(Gd,Lu)_(2)O_(3)∶Eu scintillation ceramics have promising applications in the high-energy X-ray imaging.Eu0.1Gd0.6Lu1.3O3 nano-powders with pure phase were prepared from the precursor calcined at 1050℃for 4 h by the co-precipitation method.Using the synthesized nano-powders as initial material,Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics were fabri-cated by vacuum pre-sintering at different temperatures for 2 h and hot isostatic pressing(HIP)at 1750℃for 3 h in ar-gon.The influence of pre-sintering temperature on the microstructure,optical and luminescence properties was investi-gated.The Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics pre-sintered at 1625℃for 2 h combined with HIP post-treatment show the high-est in-line transmittance of 75.2%at 611 nm.The photoluminescence(PL)and X-ray excited luminescence(XEL)spectra of the Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)transparent ceramics demonstrate a strong red emission peak at 611 nm due to the^(5)D_(0)→^(7)F_(2) transition of Eu^(3+).The PL,PLE and XEL intensities of the HIP post-treated Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics show a trend of first ascending and then descending with the increase of pre-sintering temperature.The thermally stimulated lumines-cence(TSL)curve of the HIP post-treated Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics presents one high peak at 178 K and two peaks with lower intensities at 253 K and 320 K.The peak at 320 K may be related to oxygen vacancies,and the lumines-cence peak at 178 K is related to defects caused by the valence state changes of Eu^(3+)ions.展开更多
Sodium-ion batteries are economical and environmentally sustainable energy storage batteries.Among them,β-NaMnO_(2),a promising sodium-ion cathode material,is a manganese-based oxide with a corrugated laminar structu...Sodium-ion batteries are economical and environmentally sustainable energy storage batteries.Among them,β-NaMnO_(2),a promising sodium-ion cathode material,is a manganese-based oxide with a corrugated laminar structure,which has attracted significant attention due to its structural robustness and relatively high specific capacity.However,it has short cycle life and poor rate capability.To address these issues,Ti atoms,known for enhancing structural stability,and Cu atoms,which facilitate desodiation,were doped intoβ-NaMnO_(2) by first-principles calculation and crystal orbital Hamilton population(COHP)analysis.β-NaMn_(0.8)Ti_(0.1)Cu_(0.1)O_(2) exhibits a notable increase in reversible specific capacity and remarkable rate properties.Operating at a current density of 0.2C(1C=219 mA·g^(–1))and within a voltage range of 1.8–4.0 V,the modified material delivers an initial discharge capacity of 132 mAh·g^(–1).After charge/discharge testing at current densities of 0.2C,0.5C,1C,3C,and 0.2C,the material still maintains a capacity of 110 mA h·g^(–1).The doping of Ti atoms slows down the changes in the crystal structure,resulting in only minimal variation in the lattice constant c/a during the desodiation process.Mn and Cu engage in reversible redox reactions at voltages below 3.0 V and around 3.5 V,respectively.The extended plateau observed in the discharge curve below 3.0 V signifies that Mn significantly contributes to the overall battery capacity.This study provides insights into modifyingβ-NaMnO_(2) as a cathode material,offering experimental evidence and theoretical guidance for enhancing battery performance in Na-ion batteries.展开更多
The accepted doping ion in Ti^(4+)-site of PbZr_(y)Ti_(1–y)O_(3)(PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor(Q_(m)),since the acceptor coupled by oxygen vacancy beco...The accepted doping ion in Ti^(4+)-site of PbZr_(y)Ti_(1–y)O_(3)(PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor(Q_(m)),since the acceptor coupled by oxygen vacancy becomes defect dipole,which prevents the domain rotation.In this field,a serious problem is that generally,Qm decreases as the temperature(T)increases,since the oxygen vacancies are decoupled from the defect dipoles.In this work,Q_(m) of Pb_(0.95)Sr_(0.05)(Zr_(0.53)Ti_(0.47))O_(3)(PSZT)ceramics doped by 0.40%Fe_(2)O_(3)(in mole)abnormally increases as T increases,of which the Qm and piezoelectric coefficient(d_(33))at room temperature and Curie temperature(TC)are 507,292 pC/N,and 345℃,respectively.The maximum Qm of 824 was achieved in the range of 120–160℃,which is 62.52%higher than that at room temperature,while the dynamic piezoelectric constant(d_(31))was just slightly decreased by 3.85%.X-ray diffraction(XRD)and piezoresponse force microscopy results show that the interplanar spacing and the fine domains form as temperature increases,and the thermally stimulated depolarization current shows that the defect dipoles are stable even the temperature up to 240℃.It can be deduced that the aggregation of oxygen vacancies near the fine domains and defect dipole can be stable up to 240℃,which pins domain rotation,resulting in the enhanced Q_(m) with the increasing temperature.These results give a potential path to design high Q_(m) at high temperature.展开更多
High-temperature piezoelectric vibration sensors are the preferred choice for structural health monitoring in harsh environments such as high temperatures and complex vibrations.Bismuth layer-structured CaBi_(4)Ti_(4)...High-temperature piezoelectric vibration sensors are the preferred choice for structural health monitoring in harsh environments such as high temperatures and complex vibrations.Bismuth layer-structured CaBi_(4)Ti_(4)O_(15)(CBT)high-temperature piezoelectric ceramics,with high Curie temperature(TC),are the key components for piezoelectric vibration sensors operating at temperatures exceeding 500℃.However,their low piezoelectric coefficient(d_(33))greatly limits their high-temperature applications.In this work,a novel Bi^(3+)self-doping strategy was employed to enhance the piezoelectric performance of CBT ceramics.The enhancement is attributed to an increase in the number of grain boundaries,providing more sites for space charge accumulation and promoting formation of space charge polarization.Furthermore,given that space charge polarization predominantly occurs at low frequencies,dielectric temperature spectra at different frequencies were used to elucidate the mechanism by which space charge polarization enhances piezoelectric properties of CBT ceramics.Excellent overall performance was achieved for the CBT-based high-temperature piezoelectric ceramics.Among them,TC reached 778℃,d_(33) increased by more than 30%,reaching 20.1 pC/N,and the electrical resistivity improved by one order of magnitude(reaching 6.33×10^(6)Ω·cm at 500℃).These advancements provide a key functional material with excellent performance for practical applications of piezoelectric vibration sensors at 500℃and above.展开更多
Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+),Cr^(3+)(YAGG:Ce^(3+),Cr^(3+)),as a persistent luminescent material,has advantages of high initial luminescence intensity and long persistent time,which is promising in persistent lumine...Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+),Cr^(3+)(YAGG:Ce^(3+),Cr^(3+)),as a persistent luminescent material,has advantages of high initial luminescence intensity and long persistent time,which is promising in persistent luminescent material applications.At present,YAGG:Ce^(3+),Cr^(3+)powders exhibit good persistent performance,but their persistent performance of ceramics still needs to be further improved to meet the new requirements.In this work,(Y_(0.998)Ce_(0.002))_(3)(Al_(1-x)Cr_(x))_(2)Ga_(3)O_(12) ceramics with different Cr^(3+)doping concentrations were prepared by solid-state reaction,including air pre-sintering,hot isostatic pressing(HIP)post-treatment and air annealing,to investigate the effects of Cr^(3+)doping concentration on the microstructure,optical properties and persistent performance of the ceramics.The results showed that as the doping concentration of Cr^(3+)increased from 0.025%to 0.2%(in atom),no significant effect of Cr^(3+)concentration on the morphology of pre-sintered ceramics or HIP post-treatment ceramics was observed,but the in-line transmittance gradually increased while the persistent performance gradually decreased.Among them,YAGG:Ce^(3+),Cr^(3+)ceramics doped with 0.025%Cr^(3+)showed the strongest initial luminescence intensity exceeding 6055 mcd/m^(2) and a persistent time of 1030 min after air pre-sintering combined with HIP post-treatment and air annealing.By optimizing the Cr^(3+)doping concentration and the fabrication process,the persistent luminescence(PersL)performance of the YAGG:Ce^(3+),Cr^(3+)ceramics was obviously improved.展开更多
Silicon-carbide-fiber-reinforced silicon-carbide-ceramic-based matrix(SiC/SiC)composites possess excellent properties such as low density,high strength and high temperature resistance,showing a potential application f...Silicon-carbide-fiber-reinforced silicon-carbide-ceramic-based matrix(SiC/SiC)composites possess excellent properties such as low density,high strength and high temperature resistance,showing a potential application for structural components in the aerospace field,but their oxidation behavior remains largely unknown.In this study,Yb_(2)Si_(2)O_(7)modified SiC/SiC(SiC/SiC-Yb_(2)Si_(2)O_(7))mini-composites were prepared by introducing Yb_(2)Si_(2)O_(7)as anti-oxidation phase into SiC fiber bundles via Sol-Gel and depositing SiC matrix by chemical vapor deposition(CVD).Influence of Yb_(2)Si_(2)O_(7)on microstructure,mechanical property and oxidation behavior of SiC/SiC mini-composites was investigated.The results showed that after oxidation in air at 1200 and 1400℃for 50 h,the tensile strength retentions of SiC/SiC mini-composites were 77%and 69%,respectively,and the fracture morphology exhibited flat.The Yb_(2)Si_(2)O_(7)introduced by Sol-Gel partially distributed in layers,contributing to the toughening of the material.On the fracture surface,there was interlayer debonding,which extended energy dissipation mechanism of SiC/SiC mini-composites.Tensile strength of SiC/SiC-Yb_(2)Si_(2)O_(7)mini-composites at room temperature was 484 MPa.After oxidation in air at 1200 and 1400℃for 50 h,the tensile strengths decreased to 425 and 374 MPa,resulting in retention rates of 88%and 77%,respectively.It displayed typical non-brittle fracture characteristics.The interface oxygen content of SiC/SiC mini-composites at the fracture surface was higher than that of SiC/SiC-Yb_(2)Si_(2)O_(7)mini-composites,indicating that introduction of Yb_(2)Si_(2)O_(7)could alleviate oxygen diffusion towards the interface,and therefore improve the oxidation resistance of SiC/SiC-Yb_(2)Si_(2)O_(7)mini-composites.展开更多
In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this s...In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this study,continuous carbon fiber reinforced Li_(2)O-Al_(2)O_(3)-SiO_(2)(C_(f)/LAS)glass ceramic composites doped with SiC particles(SiC_(p))were prepared by slurry immersion winding and hot pressing sintering.Effect of matrix crystallinity on ablative properties of the composites under ultra-high heat flux was investigated.By utilizing heat absorption and low thermal conductivity characteristics associated with SiO_(2)gasification within composite materials,both surface and internal temperatures of these materials are effectively reduced,thereby ensuring the safe operation of aircraft and electronic devices.Results indicate that the average linear ablation rate of composites doped with 10%(in mass)of SiC_(p)significantly decreases at a heat flux of 20 MW/m^(2).Transmission electron microscope observation reveals that the doped glass matrix exhibits increased crystallinity,reduced internal stress,and minimized lattice distortion,thereby enhancing the composites’high-temperature performance.However,excessive SiC_(p)doping leads to reduced crystallinity and deteriorated ablation performance.Ultimately,the average linear ablation rate of C_(f)/LAS composites with 10%(in mass)SiC_(p)at 20 MW/m^(2)heat flux is comparable to that of commercial carbon/carbon composites,accompanied by providing lower thermal conductivity and higher bending strength.This novel high-performance C_(f)/LAS composite is cost-effective,short-cycled,and suitable for mass production,offering promising potential for widespread application in ablation-resistant components of hypersonic vehicles.展开更多
Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2...Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment.展开更多
A toughener that can effectively improve the interlaminar toughness in carbon fiber composites is crucial for various applications.We investigated,the toughening effects of phenolphthalein-based cardo poly(ether sulfo...A toughener that can effectively improve the interlaminar toughness in carbon fiber composites is crucial for various applications.We investigated,the toughening effects of phenolphthalein-based cardo poly(ether sulfone)(PES-C)on E51/DETDA epoxy and its carbon fiber composites(CFCs).Scanning electron microscopy showed that the phase structures of PES-C/epoxy blends change from island(of dispersed phase)structures to bi-continuous structures(of the matrix)as the PES-C content increased,which is associated with reaction-induced phase separation.After adding 15 phr PES-C,the glass transition temperature(T_(g))of the blends increased by 51.5℃,and the flexural strength,impact strength and fracture toughness of the blends were improved by 41.1%,186.2%and 42.7%,respectively.These improvements could be attributed to the phase separation structure of the PES-C/epoxy sys-tem.A PES-C film was used to improve the mode-II fracture toughness(G_(IIC))of CFCs.The G_(IIC) value of the 7μm PES-C film toughened laminate was improved by 80.3%compared to that of the control laminate.The increase in G_(IIC) was attributed to cohesive failure and plastic deformation in the interleaving region.展开更多
Bioceramics have attracted extensive attention for bone defect repair due to their excellent bioactivity and degradability.However,challenges remain in matching the rate between bioceramic degradation and new bone for...Bioceramics have attracted extensive attention for bone defect repair due to their excellent bioactivity and degradability.However,challenges remain in matching the rate between bioceramic degradation and new bone formation,necessitating a deeper understanding of their degradation properties.In this study,density functional theory(DFT)calculations was employed to explore the structural and electronic characteristics of silicate bioceramics.These findings reveal a linear correlation between the maximum isosurface value of the valence band maximum(VBM_(Fmax))and the degradability of silicate bioceramics.This correlation was subsequently validated through degradation experiments.Furthermore,the investigation on phosphate bioceramics demonstrates the potential of this descriptor in predicting the degradability of a broader range of bioceramics.This discovery offers valuable insights into the degradation mechanism of bioceramics and holds promise for accelerating the design and development of bioceramics with controllable degradation.展开更多
Because of its high purity and excellent orientation, mesophase pitch is a superior precursor for high-performance car-bon materials. However, the preparation of top-notch mesophase pitch faces challenges. Catalytic p...Because of its high purity and excellent orientation, mesophase pitch is a superior precursor for high-performance car-bon materials. However, the preparation of top-notch mesophase pitch faces challenges. Catalytic polycondensation at low temperat-ures is more favorable for synthesizing mesophase pitch, because it circumvents the high-temperature free radical reaction of other thermal polycondensation approaches. The reaction is gentle and can be easily controlled. It has the potential to significantly im-prove the yield of mesophase pitch and easily introduce naphthenic characteristics into the molecules, catalytic polycondensation is therefore a preferred method of synthesizing highly spinnable mesophase pitch. This review provides a synopsis of the selective pre-treatment of the raw materials to prepare different mesophase pitches, and explains the reaction mechanism and associated research advances for different catalytic systems in recent years. Finally, how to manufacture high-quality mesophase pitch by using a cata-lyst-promoter system is summarized and proposed, which may provide a theoretical basis for the future design of high-quality pitch molecules.展开更多
Significant progress has recently been made in enhancing the power conversion efficiency(PCE)of perovskite solar cells(PSCs).The electron transport layer(ETL),as an essential component of PSCs,significantly influences...Significant progress has recently been made in enhancing the power conversion efficiency(PCE)of perovskite solar cells(PSCs).The electron transport layer(ETL),as an essential component of PSCs,significantly influences the performance of devices.Traditional spin-coating method for preparing the ETL fails to fully cover the cusp of FTO transparent conductive glass substrate,leading to direct contact between perovskite film and FTO substrate,which induces charge recombination and reduces the performance of PSCs.To address this issue,an in-situ growth method was proposed to prepare conformal SnO_(2) films on FTO glass substrates in this study.The resulting SnO_(2) films are not only dense and uniform,fully covering the cusp of the FTO glass substrates and reducing the contact area between the FTO substrates and the perovskite films,but also facilitating the formation of perovskite films with large grain sizes.Moreover,the conformal SnO_(2) films can improve the charge extraction at the SnO_(2)/perovskite interface,reduce the trap density and trap-assisted recombination in PSCs,and thus enhance the PCE of PSCs.Through comparative experiments,it is found that the PSCs with in-situ grown SnO_(2) films show an improved PCE of 21.97%,which significantly increased compared to that with spin-coated SnO_(2) films(20.93%).All above data demonstrate that the as-prepared SnO_(2) film can serve as an ideal ETL.It is worth mentioning that this method avoids the use of corrosive hydrochloric acid and toxic thioglycolic acid,and it can also be extended to ITO flexible transparent conductive substrates in the future.展开更多
The utilization of nickel-based catalysts as alternatives to expensive platinum-based(Pt-based)materials for the hydrogen evolution reaction in acidic electrolytes has attracted considerable attention due to their pot...The utilization of nickel-based catalysts as alternatives to expensive platinum-based(Pt-based)materials for the hydrogen evolution reaction in acidic electrolytes has attracted considerable attention due to their potential for enabling cost-effective industrial applications.However,the unsatisfied cyclic stability and electrochemical activity limit their further application.In this work,nickel-molybdenum(Ni-Mo)alloy catalysts were successfully synthesized through a comprehensive process including electrodeposition,thermal annealing,and electrochemical activation.Owing to the synergistic interaction of molybdenum trinickelide(Ni_(3)Mo)and molybdenum dioxide(MoO_(2))in Ni-Mo alloy,the catalyst display superior overall electrochemical properties.A low overpotential of 86 mV at 10 mA/cm^(2)and a Tafel slope of 74.0 mV/dec in 0.5 mol/L H_(2)SO_(4)solution can be achieved.Notably,remarkable stability with negligible performance degradation even after 100 h could be maintained.This work presents a novel and effective strategy for the design and fabrication of high-performance,non-precious metal electrocatalysts for acidic water electrolysis.展开更多
文摘Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation activity were studied.Several different carbon materi-als were produced from them by oxida-tion in air(350℃,300 mL/min)fol-lowed by carbonization(1000℃ in Ar),and the effect of the cross-linked structure on their structure and sodium storage properties was investigated.The results showed that the two pitch fractions were obviously different after the air oxidation.The TS fraction with a low degree of condensation and abundant side chains had a stronger oxidation activity and thus introduced more cross-linked oxygen-containing functional groups C(O)―O which prevented carbon layer rearrangement during the carbonization.As a result,a disordered hard carbon with more defects was formed,which improved the electrochemical performance.Therefore,the carbon materials derived from TS(O-TS-1000)had an obvious disordered structure and a larger layer spacing,giving them better sodium storage perform-ance than those derived from the TI-PS fraction(O-TI-PS-1000).The specific capacity of O-TS-1000 was about 250 mAh/g at 20 mA/g,which was 1.67 times higher than that of O-TI-PS-1000(150 mAh/g).
基金Supported by the National Key Research and Development Program of China(2021YFB2800201)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB43000000)。
文摘A 16-channel arrayed waveguide grating(AWG)with an 800 GHz channel spacing in the O-band has been developed and fabricated based on silica planar lightwave circuit(PLC)technology.By extending the wave⁃length allocation from 8 channels to 16 channels as specified in IEEE 802.3bs,we increased the number of chan⁃nels and boosted transmission capacity to meet the 1.6 Tbps and higher-speed signal transmission requirements for future data centers.Through optimizing the AWG structure,it has achieved insertion loss(IL)better than-1.61 dB,loss uniformity below 0.35 dB,polarization-dependent loss(PDL)below 0.35 dB,adjacent channel cross⁃talk under-20.05 dB,ripple less than 0.75 dB,center wavelength offset under 0.22 nm and 1 dB bandwidth ex⁃ceeding 2.88 nm.The AWG has been successfully measured to transmit 53 Gbaud 4-level pulse amplitude modu⁃lation(PAM4)signal per channel and the total transmission speed can reach over 1.6 Tbps.
基金supported by the National Natural Science Foundation of China(22379157)CAS Project for Young Scientists in Basic Research(YSBR-102)+2 种基金Institute of Coal Chemistry,Chinese Academy of Sciences(SCJC-XCL-2023-13,SCJCXCL-2023-10)Talent Projects for Outstanding Doctoral Students to Work in Shanxi Province(E3SWR4791Z)Fundamental Research Program of Shanxi Province(202403021222485).
文摘This data set collects,compares and contrasts the capacities and structures of a series of hard carbon materials,and then searches for correlations between structure and electrochemical performance.The capacity data of the hard carbons were obtained by charge/discharge tests and the materials were characterized by XRD,gas adsorption,true density tests and SAXS.In particular,the fitting of SAXS gave a series of structural parameters which showed good characterization.The related test details are given with the structural data of the hard carbons and the electrochemical performance of the sodium-ion batteries.
基金Supported by the Fundamental Scientific Research Plan of China(JCKY2021130B033)。
文摘In order to meet the urgent need of infrared search and track applications for accurate identification and positioning of infrared guidance aircraft,an active-detection mid-wave infrared search and track system(ADMWIRSTS)based on"cat-eye effect"was developed.The ADMWIRSTS mainly consists of both a light beam control subsystem and an infrared search and track subsystem.The light beam control subsystem uses an integrated opto-mechanical two-dimensional pointing mirror to realize the control function of the azimuth and pitch directions of the system,which can cover the whole airspace range of 360°×90°.The infrared search and track subsystem uses two mid-wave infrared cooled 640×512 focal plane detectors for co-aperture beam expanding,infrared and illumination laser beam combining,infrared search,and two-stage track opto-mechanical design.In this work,the system integration design and structural finite-element analysis were conducted,the search imaging and two-stage track imaging for external scenes were performed,and the active-detection technologies were experimentally verified in the laboratory.The experimental investigation results show that the system can realize the infrared search and track imaging,and the accurate identification and positioning of the mid-wave infrared guidance,or infrared detection system through the echo of the illumination laser.The aforementioned work has important technical significance and practical application value for the development of compactly-integrated high-precision infrared search and track,and laser suppression system,and has broad application prospects in the protection of equipment,assets and infrastructures.
基金Student Training Program for Innovation and Entrepreneurship of Hangzhou Institute for Advanced Study,UCAS(CXCY20230305)Chinese Academy of Sciences Key Project(ZDRW-CN-2021-3-1-18)。
文摘Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application,especially for selection of suitable dielectric materials for high-power microwave transmission devices and reliable power transmission.Pure magnesium oxide(MgO),a kind of ceramic dielectric material,possesses great application potential in high-power microwave transmission devices due to its high theoretical dielectric strength,low dielectric constant,and low dielectric loss properties,but its application is limited by high sintering temperature during preparation.This work presented the preparation of a new type of multiphase ceramics based on MgO,which was MgO-1%ZrO_(2)-1%CaCO_(3-x)%MnCO_(3)(MZCM_(x),x=0,0.25,0.50,1.00,1.50,in molar),and their phase structures,morphological features,and dielectric properties were investigated.It was found that inclusion of ZrO_(2) and CaCO_(3) effectively inhibited excessive growth of MgO grains by formation of second phase,while addition of MnCO_(3) promoted the grain boundary diffusion process during the sintering process and reduced activation energy for the grain growth,resulting in a lower ceramic sintering temperature.Excellent performance,including high dielectric strength(Eb=92.3 kV/mm)and quality factor(Q×f=216642 GHz),simultaneously accompanying low dielectric loss(<0.03%),low temperature coefficient of dielectric constant(20.3×10^(–6)℃^(–1),85℃)and resonance frequency(–12.54×10^(–6)℃^(–1)),was achieved in MZCM1.00 ceramics under a relatively low sintering temperature of 1350℃.This work offers an effective solution for selecting dielectric materials for high-power microwave transmission devices.
文摘Nitrogen doping has been widely used to improve the performance of carbon electrodes in supercapacitors,particularly in terms of their high-frequency response.However,the charge storage and electrolyte ion response mechanisms of different nitrogen dopants at high frequencies are still unclear.In this study,melamine foam carbons with different configurations of surfacedoped N were formed by gradient carbonization,and the effects of the configurations on the high-frequency response behavior of the supercapacitors were analyzed.Using a combination of experiments and first-principle calculations,we found that pyrrolic N,characterized by a higher adsorption energy,increases the charge storage capacity of the electrode at high frequencies.On the other hand,graphitic N,with a lower adsorption energy,increases the speed of ion response.We propose the use of adsorption energy as a practical descriptor for electrode/electrolyte design in high-frequency applications,offering a more universal approach for improving the performance of N-doped carbon materials in supercapacitors.
基金National Key R&D Program of China(2022YFB3707700)Shanghai Science and Technology Innovation Action Plan(21511104800)+3 种基金National Natural Science Foundation of China(52172111)National Science and Technology Major Project(2017-IV-0005-0042)Key Research Program of the Chinese Academy of Sciences(ZDRW-CN-2021-2-2)Science Center for Gas Turbine Project(P2022-B-IV-001-001)。
文摘ZrB_(2)-based ceramics typically necessitate high temperature and pressure for sintering,whereas ZrB_(2)-SiC ceramics can be fabricated at 1500℃using the process of reactive melt infiltration with Si.In comparison to the conventional preparation method,reactive synthesis allows for the more facile production of ultra-high temperature ceramics with fine particle size and homogeneous composition.In this work,ZrSi_(2),B4C,and C were used as raw materials to prepare ZrB_(2)-SiC via combination of tape casting and reactive melt infiltration herein referred to as ZBC ceramics.Control sample of ZrB_(2)-SiC was also prepared using ZrB_(2)and SiC as raw materials through an identical process designated as ZS ceramics.Microscopic analysis of both ceramic groups revealed smaller and more uniformly distributed particles of the ZrB_(2)phase in ZBC ceramics compared to the larger particles in ZS ceramics.Both sets of ceramics underwent cyclic oxidation testing in the air at 1600℃for a cumulative duration of 5 cycles,each cycle lasting 2 h.Analysis of the oxidation behavior showed that both ZBC ceramics and ZS ceramics developed a glassy SiO_(2)-ZrO_(2)oxide layer on their surfaces during the oxidation.This layer severed as a barrier against oxygen.In ZBC ceramics,ZrO_(2)is finely distributed in SiO_(2),whereas in ZS ceramics,larger ZrO_(2)particles coexist with glassy SiO_(2).The surface oxide layer of ZBC ceramics maintains a dense structure because the well-dispersed ZrO_(2)increases the viscosity of glassy SiO_(2),preventing its crystallization during the cooling.Conversely,some SiO_(2)in the oxide layer of ZS ceramics may crystallize and form a eutectic with ZrO_(2),leading to the formation of ZrSiO_(4).This leads to cracking of the oxide layer due to differences in thermal expansion coefficients,weakening its barrier effect.An analysis of the oxidation resistance shows that ZBC ceramics exhibit less increase in oxide layer thickness and mass compared to ZS ceramics,suggesting superior oxidation resistance of ZBC ceramics.
文摘(Gd,Lu)_(2)O_(3)∶Eu scintillation ceramics have promising applications in the high-energy X-ray imaging.Eu0.1Gd0.6Lu1.3O3 nano-powders with pure phase were prepared from the precursor calcined at 1050℃for 4 h by the co-precipitation method.Using the synthesized nano-powders as initial material,Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics were fabri-cated by vacuum pre-sintering at different temperatures for 2 h and hot isostatic pressing(HIP)at 1750℃for 3 h in ar-gon.The influence of pre-sintering temperature on the microstructure,optical and luminescence properties was investi-gated.The Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics pre-sintered at 1625℃for 2 h combined with HIP post-treatment show the high-est in-line transmittance of 75.2%at 611 nm.The photoluminescence(PL)and X-ray excited luminescence(XEL)spectra of the Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)transparent ceramics demonstrate a strong red emission peak at 611 nm due to the^(5)D_(0)→^(7)F_(2) transition of Eu^(3+).The PL,PLE and XEL intensities of the HIP post-treated Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics show a trend of first ascending and then descending with the increase of pre-sintering temperature.The thermally stimulated lumines-cence(TSL)curve of the HIP post-treated Eu_(0.1)Gd_(0.6)Lu_(1.3)O_(3)ceramics presents one high peak at 178 K and two peaks with lower intensities at 253 K and 320 K.The peak at 320 K may be related to oxygen vacancies,and the lumines-cence peak at 178 K is related to defects caused by the valence state changes of Eu^(3+)ions.
基金National Key R&D Program of China(2022YFB3807700)National Natural Science Foundation of China(22133005,22103093)+4 种基金Science and Technology Commission of Shanghai Municipality(21ZR1472900,22ZR1471600,23ZR1472600)Youth Innovation Promotion Association CAS(2022251)Shanghai Super Post-Doctor Incentive Program(2022665)China Postdoctoral Science Foundation(2023M733621)Shanghai Explorer Program(Batch I)(23TS1401500)。
文摘Sodium-ion batteries are economical and environmentally sustainable energy storage batteries.Among them,β-NaMnO_(2),a promising sodium-ion cathode material,is a manganese-based oxide with a corrugated laminar structure,which has attracted significant attention due to its structural robustness and relatively high specific capacity.However,it has short cycle life and poor rate capability.To address these issues,Ti atoms,known for enhancing structural stability,and Cu atoms,which facilitate desodiation,were doped intoβ-NaMnO_(2) by first-principles calculation and crystal orbital Hamilton population(COHP)analysis.β-NaMn_(0.8)Ti_(0.1)Cu_(0.1)O_(2) exhibits a notable increase in reversible specific capacity and remarkable rate properties.Operating at a current density of 0.2C(1C=219 mA·g^(–1))and within a voltage range of 1.8–4.0 V,the modified material delivers an initial discharge capacity of 132 mAh·g^(–1).After charge/discharge testing at current densities of 0.2C,0.5C,1C,3C,and 0.2C,the material still maintains a capacity of 110 mA h·g^(–1).The doping of Ti atoms slows down the changes in the crystal structure,resulting in only minimal variation in the lattice constant c/a during the desodiation process.Mn and Cu engage in reversible redox reactions at voltages below 3.0 V and around 3.5 V,respectively.The extended plateau observed in the discharge curve below 3.0 V signifies that Mn significantly contributes to the overall battery capacity.This study provides insights into modifyingβ-NaMnO_(2) as a cathode material,offering experimental evidence and theoretical guidance for enhancing battery performance in Na-ion batteries.
基金National Natural Science Foundation of China(U2241242)National Key R&D Program of China(2023YFB3812000,2021YFA0716502)。
文摘The accepted doping ion in Ti^(4+)-site of PbZr_(y)Ti_(1–y)O_(3)(PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor(Q_(m)),since the acceptor coupled by oxygen vacancy becomes defect dipole,which prevents the domain rotation.In this field,a serious problem is that generally,Qm decreases as the temperature(T)increases,since the oxygen vacancies are decoupled from the defect dipoles.In this work,Q_(m) of Pb_(0.95)Sr_(0.05)(Zr_(0.53)Ti_(0.47))O_(3)(PSZT)ceramics doped by 0.40%Fe_(2)O_(3)(in mole)abnormally increases as T increases,of which the Qm and piezoelectric coefficient(d_(33))at room temperature and Curie temperature(TC)are 507,292 pC/N,and 345℃,respectively.The maximum Qm of 824 was achieved in the range of 120–160℃,which is 62.52%higher than that at room temperature,while the dynamic piezoelectric constant(d_(31))was just slightly decreased by 3.85%.X-ray diffraction(XRD)and piezoresponse force microscopy results show that the interplanar spacing and the fine domains form as temperature increases,and the thermally stimulated depolarization current shows that the defect dipoles are stable even the temperature up to 240℃.It can be deduced that the aggregation of oxygen vacancies near the fine domains and defect dipole can be stable up to 240℃,which pins domain rotation,resulting in the enhanced Q_(m) with the increasing temperature.These results give a potential path to design high Q_(m) at high temperature.
基金National Natural Science Foundation of China (51932010)。
文摘High-temperature piezoelectric vibration sensors are the preferred choice for structural health monitoring in harsh environments such as high temperatures and complex vibrations.Bismuth layer-structured CaBi_(4)Ti_(4)O_(15)(CBT)high-temperature piezoelectric ceramics,with high Curie temperature(TC),are the key components for piezoelectric vibration sensors operating at temperatures exceeding 500℃.However,their low piezoelectric coefficient(d_(33))greatly limits their high-temperature applications.In this work,a novel Bi^(3+)self-doping strategy was employed to enhance the piezoelectric performance of CBT ceramics.The enhancement is attributed to an increase in the number of grain boundaries,providing more sites for space charge accumulation and promoting formation of space charge polarization.Furthermore,given that space charge polarization predominantly occurs at low frequencies,dielectric temperature spectra at different frequencies were used to elucidate the mechanism by which space charge polarization enhances piezoelectric properties of CBT ceramics.Excellent overall performance was achieved for the CBT-based high-temperature piezoelectric ceramics.Among them,TC reached 778℃,d_(33) increased by more than 30%,reaching 20.1 pC/N,and the electrical resistivity improved by one order of magnitude(reaching 6.33×10^(6)Ω·cm at 500℃).These advancements provide a key functional material with excellent performance for practical applications of piezoelectric vibration sensors at 500℃and above.
基金National Key R&D Program of China(2023YFB3506600)。
文摘Y_(3)Al_(2)Ga_(3)O_(12):Ce^(3+),Cr^(3+)(YAGG:Ce^(3+),Cr^(3+)),as a persistent luminescent material,has advantages of high initial luminescence intensity and long persistent time,which is promising in persistent luminescent material applications.At present,YAGG:Ce^(3+),Cr^(3+)powders exhibit good persistent performance,but their persistent performance of ceramics still needs to be further improved to meet the new requirements.In this work,(Y_(0.998)Ce_(0.002))_(3)(Al_(1-x)Cr_(x))_(2)Ga_(3)O_(12) ceramics with different Cr^(3+)doping concentrations were prepared by solid-state reaction,including air pre-sintering,hot isostatic pressing(HIP)post-treatment and air annealing,to investigate the effects of Cr^(3+)doping concentration on the microstructure,optical properties and persistent performance of the ceramics.The results showed that as the doping concentration of Cr^(3+)increased from 0.025%to 0.2%(in atom),no significant effect of Cr^(3+)concentration on the morphology of pre-sintered ceramics or HIP post-treatment ceramics was observed,but the in-line transmittance gradually increased while the persistent performance gradually decreased.Among them,YAGG:Ce^(3+),Cr^(3+)ceramics doped with 0.025%Cr^(3+)showed the strongest initial luminescence intensity exceeding 6055 mcd/m^(2) and a persistent time of 1030 min after air pre-sintering combined with HIP post-treatment and air annealing.By optimizing the Cr^(3+)doping concentration and the fabrication process,the persistent luminescence(PersL)performance of the YAGG:Ce^(3+),Cr^(3+)ceramics was obviously improved.
基金National Natural Science Foundation of China(52222202)National Key R&D Program of China(2022YFB3707700)+2 种基金Project of Shanghai Science and Technology Innovation Action Plan(21511104800)Shanghai Pilot Program for Basic Research-Chinese Academy of Science,Shanghai Branch(JCYJ-SHFY-2021-001)Science Center for Gas Turbine Project(P2022-B-Ⅳ-001-001)。
文摘Silicon-carbide-fiber-reinforced silicon-carbide-ceramic-based matrix(SiC/SiC)composites possess excellent properties such as low density,high strength and high temperature resistance,showing a potential application for structural components in the aerospace field,but their oxidation behavior remains largely unknown.In this study,Yb_(2)Si_(2)O_(7)modified SiC/SiC(SiC/SiC-Yb_(2)Si_(2)O_(7))mini-composites were prepared by introducing Yb_(2)Si_(2)O_(7)as anti-oxidation phase into SiC fiber bundles via Sol-Gel and depositing SiC matrix by chemical vapor deposition(CVD).Influence of Yb_(2)Si_(2)O_(7)on microstructure,mechanical property and oxidation behavior of SiC/SiC mini-composites was investigated.The results showed that after oxidation in air at 1200 and 1400℃for 50 h,the tensile strength retentions of SiC/SiC mini-composites were 77%and 69%,respectively,and the fracture morphology exhibited flat.The Yb_(2)Si_(2)O_(7)introduced by Sol-Gel partially distributed in layers,contributing to the toughening of the material.On the fracture surface,there was interlayer debonding,which extended energy dissipation mechanism of SiC/SiC mini-composites.Tensile strength of SiC/SiC-Yb_(2)Si_(2)O_(7)mini-composites at room temperature was 484 MPa.After oxidation in air at 1200 and 1400℃for 50 h,the tensile strengths decreased to 425 and 374 MPa,resulting in retention rates of 88%and 77%,respectively.It displayed typical non-brittle fracture characteristics.The interface oxygen content of SiC/SiC mini-composites at the fracture surface was higher than that of SiC/SiC-Yb_(2)Si_(2)O_(7)mini-composites,indicating that introduction of Yb_(2)Si_(2)O_(7)could alleviate oxygen diffusion towards the interface,and therefore improve the oxidation resistance of SiC/SiC-Yb_(2)Si_(2)O_(7)mini-composites.
基金National Natural Science Foundation of China(U23A6014,52103357)。
文摘In a high heat flux ablative environment,the surface temperature of aircraft rises rapidly,leading to traditional high thermal conductivity materials being ineffective at protecting internal metal components.In this study,continuous carbon fiber reinforced Li_(2)O-Al_(2)O_(3)-SiO_(2)(C_(f)/LAS)glass ceramic composites doped with SiC particles(SiC_(p))were prepared by slurry immersion winding and hot pressing sintering.Effect of matrix crystallinity on ablative properties of the composites under ultra-high heat flux was investigated.By utilizing heat absorption and low thermal conductivity characteristics associated with SiO_(2)gasification within composite materials,both surface and internal temperatures of these materials are effectively reduced,thereby ensuring the safe operation of aircraft and electronic devices.Results indicate that the average linear ablation rate of composites doped with 10%(in mass)of SiC_(p)significantly decreases at a heat flux of 20 MW/m^(2).Transmission electron microscope observation reveals that the doped glass matrix exhibits increased crystallinity,reduced internal stress,and minimized lattice distortion,thereby enhancing the composites’high-temperature performance.However,excessive SiC_(p)doping leads to reduced crystallinity and deteriorated ablation performance.Ultimately,the average linear ablation rate of C_(f)/LAS composites with 10%(in mass)SiC_(p)at 20 MW/m^(2)heat flux is comparable to that of commercial carbon/carbon composites,accompanied by providing lower thermal conductivity and higher bending strength.This novel high-performance C_(f)/LAS composite is cost-effective,short-cycled,and suitable for mass production,offering promising potential for widespread application in ablation-resistant components of hypersonic vehicles.
基金National Key R&D Program of China(2023YFE3812005)International Partnership Program of Chinese Academy of Sciences(121631KYSB20200039)+1 种基金National Center for Research and Development(WPC2/1/SCAPOL/2021)Chinese Academy of Sciences President’s International Fellowship Initiative(2024VEA0005,2024VEA0014)。
文摘Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment.
文摘A toughener that can effectively improve the interlaminar toughness in carbon fiber composites is crucial for various applications.We investigated,the toughening effects of phenolphthalein-based cardo poly(ether sulfone)(PES-C)on E51/DETDA epoxy and its carbon fiber composites(CFCs).Scanning electron microscopy showed that the phase structures of PES-C/epoxy blends change from island(of dispersed phase)structures to bi-continuous structures(of the matrix)as the PES-C content increased,which is associated with reaction-induced phase separation.After adding 15 phr PES-C,the glass transition temperature(T_(g))of the blends increased by 51.5℃,and the flexural strength,impact strength and fracture toughness of the blends were improved by 41.1%,186.2%and 42.7%,respectively.These improvements could be attributed to the phase separation structure of the PES-C/epoxy sys-tem.A PES-C film was used to improve the mode-II fracture toughness(G_(IIC))of CFCs.The G_(IIC) value of the 7μm PES-C film toughened laminate was improved by 80.3%compared to that of the control laminate.The increase in G_(IIC) was attributed to cohesive failure and plastic deformation in the interleaving region.
基金National Key Research and Development Program of China (2023YFB3813000)National Natural Science Foundation of China (52272256)State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology)(2022-KF-77)。
文摘Bioceramics have attracted extensive attention for bone defect repair due to their excellent bioactivity and degradability.However,challenges remain in matching the rate between bioceramic degradation and new bone formation,necessitating a deeper understanding of their degradation properties.In this study,density functional theory(DFT)calculations was employed to explore the structural and electronic characteristics of silicate bioceramics.These findings reveal a linear correlation between the maximum isosurface value of the valence band maximum(VBM_(Fmax))and the degradability of silicate bioceramics.This correlation was subsequently validated through degradation experiments.Furthermore,the investigation on phosphate bioceramics demonstrates the potential of this descriptor in predicting the degradability of a broader range of bioceramics.This discovery offers valuable insights into the degradation mechanism of bioceramics and holds promise for accelerating the design and development of bioceramics with controllable degradation.
文摘Because of its high purity and excellent orientation, mesophase pitch is a superior precursor for high-performance car-bon materials. However, the preparation of top-notch mesophase pitch faces challenges. Catalytic polycondensation at low temperat-ures is more favorable for synthesizing mesophase pitch, because it circumvents the high-temperature free radical reaction of other thermal polycondensation approaches. The reaction is gentle and can be easily controlled. It has the potential to significantly im-prove the yield of mesophase pitch and easily introduce naphthenic characteristics into the molecules, catalytic polycondensation is therefore a preferred method of synthesizing highly spinnable mesophase pitch. This review provides a synopsis of the selective pre-treatment of the raw materials to prepare different mesophase pitches, and explains the reaction mechanism and associated research advances for different catalytic systems in recent years. Finally, how to manufacture high-quality mesophase pitch by using a cata-lyst-promoter system is summarized and proposed, which may provide a theoretical basis for the future design of high-quality pitch molecules.
基金Space Application System of China Manned Space Program。
文摘Significant progress has recently been made in enhancing the power conversion efficiency(PCE)of perovskite solar cells(PSCs).The electron transport layer(ETL),as an essential component of PSCs,significantly influences the performance of devices.Traditional spin-coating method for preparing the ETL fails to fully cover the cusp of FTO transparent conductive glass substrate,leading to direct contact between perovskite film and FTO substrate,which induces charge recombination and reduces the performance of PSCs.To address this issue,an in-situ growth method was proposed to prepare conformal SnO_(2) films on FTO glass substrates in this study.The resulting SnO_(2) films are not only dense and uniform,fully covering the cusp of the FTO glass substrates and reducing the contact area between the FTO substrates and the perovskite films,but also facilitating the formation of perovskite films with large grain sizes.Moreover,the conformal SnO_(2) films can improve the charge extraction at the SnO_(2)/perovskite interface,reduce the trap density and trap-assisted recombination in PSCs,and thus enhance the PCE of PSCs.Through comparative experiments,it is found that the PSCs with in-situ grown SnO_(2) films show an improved PCE of 21.97%,which significantly increased compared to that with spin-coated SnO_(2) films(20.93%).All above data demonstrate that the as-prepared SnO_(2) film can serve as an ideal ETL.It is worth mentioning that this method avoids the use of corrosive hydrochloric acid and toxic thioglycolic acid,and it can also be extended to ITO flexible transparent conductive substrates in the future.
基金supported by the National Natural Science Foundation of China(22179138).
文摘The utilization of nickel-based catalysts as alternatives to expensive platinum-based(Pt-based)materials for the hydrogen evolution reaction in acidic electrolytes has attracted considerable attention due to their potential for enabling cost-effective industrial applications.However,the unsatisfied cyclic stability and electrochemical activity limit their further application.In this work,nickel-molybdenum(Ni-Mo)alloy catalysts were successfully synthesized through a comprehensive process including electrodeposition,thermal annealing,and electrochemical activation.Owing to the synergistic interaction of molybdenum trinickelide(Ni_(3)Mo)and molybdenum dioxide(MoO_(2))in Ni-Mo alloy,the catalyst display superior overall electrochemical properties.A low overpotential of 86 mV at 10 mA/cm^(2)and a Tafel slope of 74.0 mV/dec in 0.5 mol/L H_(2)SO_(4)solution can be achieved.Notably,remarkable stability with negligible performance degradation even after 100 h could be maintained.This work presents a novel and effective strategy for the design and fabrication of high-performance,non-precious metal electrocatalysts for acidic water electrolysis.
