查看更多>>摘要：Rare earth(RE)elements are excellent modifiers for non-metallic inclusions that inevitably appear in steel and affect steel properties.This paper reviews the research status of inclusions modification by RE elements and the changes it cause on steel properties.First,the inclusion changes caused by RE modi-fication are described.Generally,after adding pure RE,the main evolution of inclusions occurs as M→M+RE-Al-O→ RE-Al-O+RE2O2S→ RE2O2S+RE-S/RE2O2S+RE-O with an increase in the RE content(M represents the inclusions before RE addition).The type of final inclusion obtained after RE modification is related to the relative contents of S and O in the steel.Moreover,fine,regular,and uniformly distributed inclusions can be obtained with appropriate RE addition.However,the effective-ness of inclusions modification by adding both RE and non-RE elements is closely related to the order of their addition.Second,the applications and advantages of thermodynamic calculations in the study of RE-modified inclusions are introduced.Third,the changes in the corrosion resistance,impact properties,and other properties of steel caused by the modification of inclusions by RE are reviewed.Finally,the perspectives and trends of inclusions modified by RE elements in the steel industry are presented.
查看更多>>摘要：Three lanthanide ions and a rigid(1,1'-biphenyl)-2,4,6-tricarboxylic acid(H3bptc)ligand led to the iso-structural lanthanide metal-organic frameworks(Ln-MOFs){[Ln(bptc)(H2O)3]·3H2O}n(Lnbptc,Ln=Eu,Tb,Gd,EuxTb1-x,EuxGd1-x,TbxGd1-x,and Eu0.12Tb0.52Gd0.36).The density functional theory(DFT)and time-dependent DFT calculation were expanded on H3bptc,which point to the occurrence of"antenna effect".The minor diameter samples of Eubptc,Tbbptc,and Gdbptc can also be attained via the micro-wave synthesis and employed for handwriting anticounterfeiting.Interestingly,the typical red emission of Eu3+and green emission of Tb3+could be fine-tuned by Gd3+via chemical mixing to be full-color emissions bimetallic doped EuxTb1-xbptc,EuxGd1-xbptc,and TbxGd1-xbptc.The above synthetic bime-tallic MOFs can be fixed in positioning boxes of quick response(QR)codes with diverse emission for anticounterfeiting.The message can be decoded under the irradiation of 365 nm ultraviolet lamp while invisible in the daylight.Notably,the trimetallic doped Eu0.12Tb0.52Gd0.36bptc emits white light with the CIE color coordinate(0.34,0.34).Furthermore,Tbbptc is demonstrated to be a sensitive probe toward nitrobenzene and acetone with multiple mechanisms.
查看更多>>摘要：Rare earth co-doped phosphor for fluorescence intensity ratio(FIR)thermometer has gained increasing attention in recent years.Herein,the novel Tb3+and Eu3+co-doped K3SrBi(P2O7)2(KSBP)phosphate phosphors were reported.The crystal structure of the title phosphor was determined using Rietveld refinement and proved to have a three-dimensional structure.The time-resolved spectroscopy reveals that there is almost no energy transfer between Tb3+and Eu3+.More importantly,Tb3+and Eu3+emissions show different thermal quenching behaviors,which claims the potential of this material for application in optical thermometer.The FIR of the typical KSBP:0.02Tb3+,0.04Eu3+sample demonstrates a polynomial relationship as a function of temperature and the absolute and relative sensitivity are 0.025 K-1 and 0.59％/K,respectively.In general,our study reports a novel and potential KSBP:Tb3+,Eu3+phosphate phosphor that is promising for use in high-sensitive FIR thermometers.
查看更多>>摘要：A novel layered perovskite tantalate phosphor Sr3LaTa3O12∶Sm3+(SLTO∶Sm3+)with orange-red emission was obtained for the first time via the solid-phase synthetic method.The phase purity,surface morphology,element distribution and luminescent properties of the SLTO∶xSm3+(x=0.01 mol％-0.30 mol％)phosphors were investigated.Under 408 nm excitation,the optimum doped SLTO∶0.10Sm3+phosphor emits orange-red light at 598 nm with the highest emission peak(4G5/2 → 6H7/2).The critical energy transfer distance is 1.687 nm.The prepared SLTO∶0.10Sm3+phosphor has excellent thermal stability with temperature quenching temperature(To.5＞500 K)and high activation energy(Ea=0.25 eV).Through calculation,the chromaticity coordinates of all samples are concentrated in the orange-red area,and the color purity reaches 99％.The fabricated white light-emitting diode(w-LED)has a good correlated color temperature(5132 K),a high Ra(89),and the CIE chromaticity coordinates(0.340,0.327).Consequently,the superiority of orange-red-emitting tantalate SLTO∶Sm3+phosphors for w-LEDs is demonstrated.
查看更多>>摘要：In order to improve the multi-ion cooperative transition,we proposed and exploited a novel nanoscale effect,namely the nanoshell effect in bulk materials.Based on the effect,an optimal material structure was designed by coating the surfaces of CaF2∶Yb3+micron size particles with ZrO2.An about 2 times higher intensity of cooperative luminescence is observed upon laser excitation at 980 nm.Dynamical analysis exhibits that the novel effect plays a key role in improving the performance of cooperative transitions.Our results also suggest that the nanoshell effect in bulk materials is likely to be significant in some special cases,which have not been reported yet in the literature.
查看更多>>摘要：A promising series of HoyNdxPb(1-x-y)F2(x=0,0.01,0.02,0.03,0.04;y=0.02)crystals was grown by the Bridgman method.The influence of the Nd3+ions concentration on mid-infrared(～2.0,～2.9 and～3.9 μm)fluorescence emissions of Ho3+ions in the PbF2 crystal excited by 808 nm laser diode was investigated in this work.The energy transfer mechanism between Nd3+ions and Ho3+ions under different concen-trations of the Nd3+ions was systematically analyzed.The results show that the Nd3+ions have good sensitization and deactivation effect on the Ho3+ions to stimulate the mid-infrared fluorescence emissions.The experimental analysis proves that the sensitization efficiency of the Nd3+ions is relatively stable at around 93.45％with varying Nd3+-doping concentrations.Concentration dependence studies indicate that the concentration of the Nd3+ions has significant influence on mid-infrared emissions.When the doping concentration of the Nd3+ions is up to 2.0 at％,the intensity of～2.0,～2.9 and～3.9 μm emissions all reach the maximum.The output characteristics of a 3.9 μm laser are simulated,and it is found that with the increase of the Nd3+-doping concentration,the peak power,pulse width,and peak energy all meet the trend of first increasing and then decreasing,and Ho0.02Nd0.02Pb0.96F2 crystal displays the best performance.All the results show that the Nd3+/Ho3+co-doped PbF2 crystals might act as a useful optical medium for mid-infrared laser applications.
查看更多>>摘要：In this study,a series of Gd3+-doped mixed Ni-Cu-Zn ferrites with composition of Zn0.5Ni0.3Cu0.2Fe2-x GdxO4(x=0,0.025,0.05,0.075,0.1)was prepared using self-ignition sol-gel method.The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix.A rise in the Gd3+concentration leads to an increase in crystallite size and lattice parameter.In Fourier transform infrared spectra,two main absorption bands belonging to the spinel structure are observed.The high-frequency bands(v1)represent the tetrahedral complex,while the low-frequency bands(v2)signify the octahedral complex.The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV,depending on their size.The magnetic characteristics of the material,such as saturation magnetization and coercivity are significantly altered with the concentration of Gd3+in the solution.Using Rhodamine B(RhB)as a model organic pollutant,an in-depth investigation of the photocatalytic activity of the compounds was carried out.The present outcomes show that adding an adequate amount of Gd3+significantly enhances the number of hydroxyl radicals produced by the ferrite,in turn,increasing the photocatalytic activity of the material.Mechanism elucidated by scavenger studies reveals that·OH and holes are the primary reactive radicals responsible for the degradation process.Prepared photocatalysts show an insignificant performance loss in five consecutive cycles.Thus,it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.
查看更多>>摘要：In dye-photocatalysis,widening the wavelengths absorption range of catalysts as well as aborting the recombination of the photoexcited charge carriers(electrons-holes pairs)are of paramount significance.In the current study,we report the photocatalytic characteristics of four compositions composed of TiO2,Ti0.97Cu0.03O2,Ti0.965Cu0.03La0.005O2 and Ti0.96Cu0.03La0.01O2 powders for two harmful dyes(Congo red and methylene blue).The X-ray diffraction technique verified the configuration of mixed anatase and rutile phases in pure TiO2 and Ti0.97Cu0.03O2 powders while Ti0.965Cu0.03La0.005O2 and Ti0.96Cu0.03La0.01O2 powders possess anatase phase only.The changes of the band gap structure and dimensions of the unit cell volume of TiO2 confirm the substitution of Ti4+sites by Cu2+and La3+ions.Remarkable widening of wavelengths absorption with formation of long absorption tails were found in TiO2(3.13 eV)through insertion of La3+plus Cu2+ions.Ti0.965Cu0.03La0.005O2 and Ti0.96Cu0.03La0.01O2 samples exhibit a visible light band gap of 2.3 and 2.7 eV,respectively.Based on SEM images,incorporation of Cu2+and La3+ions influences the surface morphology of TiO2.The resulting Ti0.97Cu0.03O2,Ti0.965Cu0.03La0.005O2 and Ti0.96Cu0.03La0.01O2 powders present enhanced photocatalytic activity towards Congo red dye degrada-tion compared to pure one under natural solar spectrum.The best Ti0.96Cu0.03La0.01O2 catalyst exhibits superior photocatalytic activity of 96％for 10 ppm CR dye in 20 min as well as above average photo-catalytic efficiency of 63％for 30 ppm CR dye in 120 min.As well,it showed acceptable photodegradation activity of 52％for 30 ppm MB solution in 140 min of sunlight irradiation.The heightened photo-degradation efficiency of Ti0.96Cu0.03La0.01O2 catalyst can be clarified in terms of higher charge carriers'separation(Cu2++e-→ Cu+,La3++e→ La2+),oxygen vacancies,full anatase phase structure as well as the wide range of visible light absorption.
查看更多>>摘要：Herein,we attempted to engineer oxygen vacancies on the surface of LaCoO3 perovskite through simple post-treatments(acid or reductive thermal treatments).Acid treatment induces oxygen vacancies through the selective etching of the La cations,whereas thermal treatment in a reducing atmosphere generates oxygen vacancies by directly removing lattice oxygen.The characterization results confirm that the number of surface oxygen vacancies,which are crucial in various catalytic oxidation reactions,considerably increases in the LaCoO3 catalysts treated with acid or reducing gas.Acid treatment enriches the oxygen vacancies while maintaining the structure of the LaCoO3 catalysts,which can not be achieved through reductive thermal treatment.Therefore,the acid treatment is considered a promising technique for oxygen vacancy engineering of perovskite catalysts for tuning their catalytic activities.Furthermore,the catalytic activities of the posttreated LaCoO3 catalysts for CO oxidation were evaluated and are noted to be considerably better than those of the pristine LaCoO3 catalyst due to their abundant oxygen va-cancies.Consequently,we conclude that the oxygen vacancies of perovskite catalysts can be effectively engineered via two simple methods and play a significant role in CO oxidation.
查看更多>>摘要：The sulfated CeO2/Al2O3 catalysts with different sizes of CeO2 nanoparticles were prepared by using pure H2O or acetic acid solution as impregnation solvent,and the influence of sizes of CeO2 nanoparticles on the catalytic performances of the sulfated CeO2/Al2O3 catalyst was studied.The catalytic performance tests show that the sulfated CeO2/Al2O3 catalyst using acetic acid solution as impregnation solvent has better catalytic activity and the resistance to K+poisoning than the sulfated CeO2/Al2O3 catalyst using pure H2O as impregnation solvent.The excellent catalytic performances can be ascribed to the smaller sizes of CeO2 nanoparticles in CeO2/Al2O3 catalyst using acetic acid solution,which results in larger amount of adsorbed sulfate species,surface acid sites,surface active oxygen species and excellent redox property.These features are helpful for improving the catalytic performances of sulfated CeO2/Al2O3 catalyst using smaller amount of CeO2 to cut the costs.
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