In order to develop a highly sensitive material for nondestructive testing(NDT),(Tb_(0.3) Dy_(0.7))Fe_(1.95) thin films were deposited on FeCo substrates at room temperature by magnetron sputtering and annealed.The ma...In order to develop a highly sensitive material for nondestructive testing(NDT),(Tb_(0.3) Dy_(0.7))Fe_(1.95) thin films were deposited on FeCo substrates at room temperature by magnetron sputtering and annealed.The magnetostrictive properties and the detection efficiency of the composite films were investigated.Results demonstrate that the detection efficiency roughly shows regular consistency with the magnetostrictive strain of the TbDyFe films. Heat treatment has a great effect on the crystalline state and the magnetostrictive strain of the composite materials. The as-deposited(Tb_(0.3) Dy_(0.7))Fe_(1.95) films are amorphous, and the saturation magnetostriction(ls) is only 90 ppm. However, the nanostructured crystalline REFe2 is partially separated out in amorphous matrix after annealing at 600C for 1 h, and the ls increases to 265 ppm. Simultaneously, the detection efficiency of the composite materials is obviously improved compared to that of the as-deposited films. The detection signal of traditional FeCo strip is0.4 V at the excitation power of 1.0 P and frequency of 128 kHz and that of the strip increases significantly by depositing one layer of(Tb_(0.3) Dy_(0.7))Fe_(1.95) film. The detection signal of the composite material annealed at 600C is the best, even reaching saturation value of 2.5 V(1.0 P, 128 kHz). The results may provide us with a method for preparing new materials for NDT.展开更多
Progress of studies on various multi-color long afterglow luminescence materials was reviewed.Two luminescent mechanism of long afterglow behavior were discussed.Further research and development prospects about the ma...Progress of studies on various multi-color long afterglow luminescence materials was reviewed.Two luminescent mechanism of long afterglow behavior were discussed.Further research and development prospects about the materials were proposed.展开更多
With Al2O3, Dy2O3, and SiO2 as starting materials, the basic glass of Al2O3-Dy2O3-SiO2 system was prepared by conventional melting technology, and their thermal expansion coefficients （TECs） at different anneal time...With Al2O3, Dy2O3, and SiO2 as starting materials, the basic glass of Al2O3-Dy2O3-SiO2 system was prepared by conventional melting technology, and their thermal expansion coefficients （TECs） at different anneal time were investigated. TECs of the basic glass, which were heat-treated under different temperature, were also investigated. The result showed that TECs of the basic glass gradually approached a fixed value as the anneal time was extended, which suggested that most of the inner stress had been eliminated. After heat treatment, the contents of Dy2O3, Dy2Si2O7, and a new crystal increased up to 1200 ℃ and decreased below 1250 ℃, which was consistent with the TEC change of crystallized samples. This suggests that the crystal has a direct effect on TECs of the crystallized samples.展开更多
The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the...The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the further development of magnetic properties.Currently,the primary debates re-garding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism.To clarify this mechanism,the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different tem peratures.In this study,it was found that the formation of TbFe_(2) phase is related to the dis-solution of _(2)Fe_(14)B grains during GBDP with Tb.The theory of mixing heat and phase separation further confirms that the Nd_(2)Fe_(14)B phase dissolves to form a mixed phase of Nd and TbFe_(2),which then solidifies into the(Nd,Tb)_(2)Fe_(14)B phase.Based on the discovery of the TbFe_(2) phase,the dissolution-solidification mechanism is considered the primary mechanism for GBDP.This is supported by the elemental content of the two typical core-shell structures observed.展开更多
AlScN piezoelectric films prepared by AlSc alloy sputter targets are essential materials for 5G radio frequency filters.The thermophysical properties of AlSc alloy targets are closely related to their welding processe...AlScN piezoelectric films prepared by AlSc alloy sputter targets are essential materials for 5G radio frequency filters.The thermophysical properties of AlSc alloy targets are closely related to their welding processes and applications.Al-xSc alloys(x=5,10,15,20,25,at%)were prepared by vacuum induction melting,whose purity is mainly determined by the raw materials and the production process.The results reveal that as the Sc content increases from 5at%to 20at%,the volume fraction of the Al_(3)Sc phase in the alloy increases from 26.9%to 80.2%,and the average grain size of the Al_(3)Sc phase increases from 12.9μm to 67.7μm during this period.Additionally,both the coefficient of thermal expansion(CTE)and thermal conductivity(TC)of AlSc alloys exhibit a downward trend.Based on experimental data and first-principles calculations,the effective medium theory and the Turner model effectively predict the TC and CTE of Al-xSc alloys.The optimal characteristic parameter(k0)of the Turner model is determined to be 50.The model predictions align well with the experimental results.展开更多
Ti-Gd alloys with Gd contents of 2 wt%-8 wt% were prepared,and the influence of Gd content on the microstructure,mechanical properties,corrosion behavior,neutron absorption property and density of the alloy weas inves...Ti-Gd alloys with Gd contents of 2 wt%-8 wt% were prepared,and the influence of Gd content on the microstructure,mechanical properties,corrosion behavior,neutron absorption property and density of the alloy weas investigated.The micro structure changes from full lamellar α phase to fine equiaxed crystals,and the area fraction of Gd-rich phase decreases from 3.2% to 1.8% and then increases to 9.1%.Gd has three existing forms:pure Gd,compound oxide of Gd_(2)TiO_(5)and/or Gd_(2)O_(3)and solidifies in the Ti matrix.Ti-4Gd exhibits the best mechanical properties,its tensile strength and elongation is 102 MPa and 49%,respectively.The neutron transmittancy of Ti-8Gd alloy in water is the lowest,which is 3.75%.The corrosion rate of Ti-Gd alloy is 0.00097-0.00238 mm/a,which meets the corrosion standard of small-scale nuclear reactors and containers for spent fuel.展开更多
Aluminum is the main impurity of the weathered crust elution-deposited rare earth ore(WCED-REO).Efficient leaching of rare earths and low leaching of aluminum are of great importance for the leaching of the WCED-REO.T...Aluminum is the main impurity of the weathered crust elution-deposited rare earth ore(WCED-REO).Efficient leaching of rare earths and low leaching of aluminum are of great importance for the leaching of the WCED-REO.The effects of pH,MgSO_(4) concentration and Al^(3+)concentration of the leaching agent solution on the column leaching behaviors of WCED-REO using magnesium sulfate were investigated.Experimental data show that controlling the MgSO_(4) concentration to 0.15 mol/L,pH of the leaching agent solution to 2,the leaching amount of aluminum from the rare earth ore gradually decreases with the increase of Al^(3+)concentration in the leaching agent solution,indicating that Al^(3+)in the leaching agent solution may act as leaching agent to participate in the ion exchange of RE3+,but the leaching amounts of rare earths change insignificantly as the Al^(3+)concentration is increased.Increasing the MgSO_(4) concentration is beneficial to the leaching of aluminum,and when the Al^(3+)concentration is 0.04 mol/L(Al accumulation),the amount of Al^(3+)leached from the rare earth ore increased gradually with increasing the MgSO_(4) concentration.The pH of the leaching agent solution has a significant influence on the leaching of aluminum in the rare earth ore,and the leaching amount of aluminum from the rare earth ore increases gradually with decreasing the pH.When the Al^(3+)conce ntration is 0.04 mol/L(Al accumulation)and the pH of the leaching agent solution is above 2.0,the aluminum in the leaching agent solution can be back-adsorbed onto the rare earth ore,and the amount of the back-adsorbed Al^(3+)increases with increasing the pH of the leaching agent solution.The injection rate of the leaching agent solution has slight effect on the leaching behavior of rare earths and aluminum.In summary,leaching of Al^(3+)and consumption of MgSO_(4) can be reduced by regulating the accumulation of aluminum,MgSO_(4) concentration and pH.展开更多
The lanthanum-cerium-based slurry(LC-slurry)is extensively utilized in the chemical mechanical polishing(CMP)of TFT-LCD glass substrates,optical lenses,and other glass products.Sodium hexametaphosphate(SHMP),as a disp...The lanthanum-cerium-based slurry(LC-slurry)is extensively utilized in the chemical mechanical polishing(CMP)of TFT-LCD glass substrates,optical lenses,and other glass products.Sodium hexametaphosphate(SHMP),as a dispersant,is commonly employed to enhance the dispersion properties of LCslurry for improved polishing performance.However,the tendency of sedimentation to form a compacted sediment layer,which is challenging to redisperse,increases storage difficulty and polishing equipment failure risk,thereby limiting its utilization in CMP.In the present study,sodium carboxymethylcellulose(CMC-Na),a long-chain organic polymer,was employed to enhance the redispersibility of LC-slurry containing SHMP.A comprehensive investigation was conducted on the influence of CMC-Na dosage and slurry pH on dispersibility,redispersibility and polishing performance.Additionally,an analysis was carried out to elucidate the underlying mechanism behind the effect of CMC-Na.The study demonstrates that the LC-slurry,containing 250 ppm SHMP and 500 ppm CMC-Na,exhibits excellent dispersibility and redispersibility.Further polishing tests demonstrate that compared to the LC-slurry containing only SHMP,utilizing the slurry containing both SHMP and CMC-Na at various pH for polishing thin film transistor liquid crystal display(TFT-LCD)glass substrates results in a reduction of both material removal rate(MRR)and surface roughness(Sa).Specifically,when adjusting the slurry to a pH range of 5-6,the MRR can reach up to 330 nm/min,which closely approximates the MRR achieved by LC-slurry containing only 250 ppm SHMP at corresponding pH values.Meanwhile,after polishing,the surface roughness of the glass substrate measures approximately 0.47 nm.展开更多
The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be de...The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process.An efficient,clean,and economical process called the"combined method"was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate(MPREC).The main steps of this process include weak oxidation atmosphere roasting,step leaching of hydrochloric acid,solid-liquid separation,the monazite slag with sulfuric acid roasting water leaching,etc.In this paper,the roasting process of MPREC under a weak oxidation atmosphere was investigated.The study examines the thermal decomposition kinetics,phase transition process,and leaching behavior of MPREC in air/CO_(2)atmosphere.Results show that,the activation energy(Ea)for MPREC thermal decomposition in air and CO_(2)atmosphere are 146 and 320 kJ/mol,respectively.At temperature above 500℃in air or above 700℃in CO_(2)atmosphere,REOF are generated from bastnaesite through an in-situ reaction with CaO,which is decomposed from CaCO_(3),to form CaF_(2)and rare earth oxide(REO).Thus,F is regulated into solid phase.In an oxidizing atmosphere,the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ).In co ntrast,the oxidation of Ce(Ⅲ)in a CO_(2)atmosphere is significantly inhibited.At 700℃,the oxidation rate of Ce in air is 74.09%,while in a CO_(2)atmosphere,it is only 33.83%.The hydrochloric acid leaching experiment shows that,the leaching rate of rare earth after roasting at 600℃under an air atmosphere reaches to 82.9%,and it reaches 87%after roasting at 800℃under a CO_(2)atmosphere.The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.展开更多
NO catalytic oxidation is the key performance of the diesel oxidation catalyst(DOC).We present a facile deposition method for the core-shell rare-earth manganese-zirconium composite oxide that shows the Mn mullite pha...NO catalytic oxidation is the key performance of the diesel oxidation catalyst(DOC).We present a facile deposition method for the core-shell rare-earth manganese-zirconium composite oxide that shows the Mn mullite phase uniform loading on the surface of zirconium-based composite(YMO/CYZO),which demonstrates a superior NO oxidation catalytic performance in simulated diesel combustion conditions and better thermal stability than mullite phase YMn_(2)O_(5)oxide.The NO oxidation at 250℃over YMO/CYZO-a approaches 25.2%in contrast to 13.52%over YMn_(2)O_(5)-a.Then the catalytic performance of YMO/CYZO,YMO and commercial 1 wt%Pt/Al_(2)O_(3)in a NO+O_(2)atmosphere was compared.The maximum conversion rate of YMO/CYZO to NO oxidation is 89.6%at 274℃with a GHSV of 50000 h^(-1),and the performance is superior to that of YMO(82.8%at 293℃)and 1 wt%Pt/Al_(2)O_(3)(68.6%,335℃).The NO-temperature programmed desorption(NO-TPD)and diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)results reveal that YMO/CYZO has multiple NO adsorption sites and high storage capacity.Furthermore,density functional theory(DFT)calculation indicates that YMO/CYZO has lower oxygen vacancy formation energies(E_(v)=0.93 eV)and favorable NO adsorption energies(E_(ads)=2.1 eV).Moreover,in situ X-ray photoelectron spectroscopy(XPS)characterization shows that the core-shell structure of YMO/CYZO has the potential to transmit active oxygen species to help realize Mn3+to Mn4+during the reaction process to enhance the conversion of NO*molecules,while NO oxidation reactions follow the MvK mechanism.展开更多
Rare earth carbonates are essential precursors for the synthesis of oxide materials.In this study,we utilized in situ monitoring equipment to explore the alterations in the crystallization during the coprecipitation s...Rare earth carbonates are essential precursors for the synthesis of oxide materials.In this study,we utilized in situ monitoring equipment to explore the alterations in the crystallization during the coprecipitation synthesis of cerium carbonate.By controlling the crystallization pathway and in the absence of any te mplating agents,we successfully synthesized a unique sphe rical self-assembled cerium oxide particle(Ceria-S).The Ceria-S exhibits excellent polishing performance.The crystallization process of cerium carbonate at 50℃persists for roughly 50 min.During the initial stages of crystallization from 0 to t_(3),the precipitated particles are amorphous.This is followed by a plateau phase of crystal growth from t_(3)to t_(5).Subsequently,during the burst crystallization phase from t_(5)to t_(6),Ce_(2)(CO_(3))_(3)·6H_(2)O and Ce_(2)O(CO_(3))_(2)·nH2O are formed,exhibiting a rod-like crystal morphology.By rapidly drying the precipitated particles at 60℃for 10 min and calcining,Ceria-S is obtained.The Ceria-S,with an average diameter of 180 nm,is assembled from primary cerium oxide nanoparticles of approximately 15 nm.Owing to the self-assembly structure of cerium oxide spherical nanoparticles,they exhibit a significantly larger specific surface area,resulting in an elevated concentration of Ce^(3+)as high as 35.5%.The Ceria-S exhibits a polishing removal rate of 420 nm/min,effectively decreasing the surface roughness(S_(a))of K9 glass from 1.605 to 0.404 nm.展开更多
There has been a continuous effort to improve the thermal stability of subnanometric platinum(Pt)cluster(<2 nm) catalyst because Pt cluster on CeO_(2) support can be mobile and aggregated into nanoparticle on heati...There has been a continuous effort to improve the thermal stability of subnanometric platinum(Pt)cluster(<2 nm) catalyst because Pt cluster on CeO_(2) support can be mobile and aggregated into nanoparticle on heating at elevated temperatures,yet this great challenge remains.In this study,a strategy is reported to improve the thermal stability of subnanometric Pt cluster by hydrothermal deposition method.Based on this method,zirconium(Zr) was precisely doped on surface of Ce_(0.95)Zr_(0.05)O_(2) by accurately controlling Pt subnanometric cluster size.The surface doping of Zr is favorable for forming the Zr-O-Ce site and activating surface lattice oxygen atoms,which results in strong electronic interactions to stabilize the Pt subnanometric cluster.After high-temperature aging treatment at 1000℃/4 h,the single atom Pt supported on CeO_(2) is aggregated into larger sized(>3 nm) nanoparticle.In contrast,the single atom Pt supported on Ce_(0.95)Zr_(0.0)5O_(2) displays less agglomeration into subnanometric cluster with size of(1.4±0.3) nm.Moreover,the CO oxide catalytic performance of Ce_(0.95)Zr_(0.0)5O_(2)-Pt is 26% and 31%higher than that of CeO_(2)-Pt and commercial Al_(2)O_(3)-Pt catalysts,respectively.The experimental and density functional theory(DFT) calculations indicate that the Zr-O-Ce site and Pt subnanometric cluster interface have more defect sites and active oxygen species than CeO_(2)-Pt interface,which activate the Mars van Krevelen(MvK) mechanism,facilitating the catalytic performance.展开更多
The magnetic loss plays a key role in electromagnetic waves(EMW)absorption.However,the magnetic loss ability would obviously draw at high frequency,and the component lacks the dielectric loss ability,resulting in poor...The magnetic loss plays a key role in electromagnetic waves(EMW)absorption.However,the magnetic loss ability would obviously draw at high frequency,and the component lacks the dielectric loss ability,resulting in poor EMW absorption.In this work,we design a core-shell-structured Fe@Sm_(2)Fe_(17)dual magnetic nanoparticle.The 200-nm Sm_(2)Fe_(17)nanoparticles play a key role in maintaining relatively high magnetic loss ability even at high frequency.And the introduction of 3-μm Fe cubes can optimize the dielectric parameters by the interface polarization and thus enhance the impedance matching.Meanwhile,Fe cubes with easy axis vertical to six planes can absorb the EMW with different directions,leading to the enhancement of the EMW attenuation.Especially,the Fe cubes can align the moment of Sm_(2)Fe_(17)nanoparticles,which can increase exchange-coupling interaction between them to further improve the magnetic loss capacity and broaden the effective absorption bandwidth(EAB).Furthermore,the small-sized Sm_(2)Fe_(17)nanoparticles provide a rough surface,which promotes multiple reflections and scattering of the incident EMW.As a result,the optimal EMW attenuation performance with a minimum reflection loss exceeding-51.4 dB and a broadened EAB up to 6.6 GHz at 1.4 mm was achieved in Fe@Sm_(2)Fe_(17)composites with Sm/Fe of 1:12.Our work provides profound insights into developing well-coordinated magnetic-dielectric nanocomposites for EMW absorption engineering.展开更多
In acid treatment technology of Baotou mixed rare earth ore,large quantities of ammonia-nitrogen wastewater are produced in the step of ammonium bicarbonate precipitation to transform rare earth sulfate.In this paper,...In acid treatment technology of Baotou mixed rare earth ore,large quantities of ammonia-nitrogen wastewater are produced in the step of ammonium bicarbonate precipitation to transform rare earth sulfate.In this paper,we adopted a green precipitant magnesium bicarbonate(Mg(HCO3)2) to substitute ammonium bicarbonate to eliminate ammonia-nitrogen pollution.The effects of n(HCO3^-):n(RE^3+),aging temperature and aging time on the crystallization using Mg(HCO3)2 precipitation method were investigated.The results indicate that the rare earths could be completely recovered when n(HCO3^-):n(RE^3+) is higher than 3.15:1.The crystal water content of rare earth carbonates is affected by the aging temperature.The precipitate has a bad filterability when the aging temperature is over 40℃.This can be attributed to the less crystallized water molecules of the hydrated rare earth carbonate precipitation.The mixed rare earth carbonates are prone to be crystalline,and have a good filterability at aging temperatures below 40℃.Meanwhile,the evolution mechanism of crystalline mixed rare earth carbonates is reasonably deduced,the amorphous rare earth carbonates are first dissolute and then recrystallized.Under the optimized aging conditions,the purity of the crystalline precipitate meets the requirements of the fine product standard(GB/T 16479-2008).The filtrated could be used to produce Mg(HCO3)2,thus to realize the recycling of magnesium sulfate.展开更多
To clearly elucidate the oxidative roasting behaviors of the bastnaesite, the thermal decomposition and oxidation of the bastnaesite concentrate in inert and oxidative atmosphere have been investigated in detail. Expe...To clearly elucidate the oxidative roasting behaviors of the bastnaesite, the thermal decomposition and oxidation of the bastnaesite concentrate in inert and oxidative atmosphere have been investigated in detail. Experimental data indicated that the initial decomposition temperature of the concentrate under N2 atmosphere is 150 ℃ higher than that under O2 atmosphere,most likely because the oxidation of the cerium induces the decomposition of the concentrate. For the roasted samples under N2 atmosphere at500 ℃ and above,the oxidation efficiency of the cerium is 19.8%-26.8% because of the fact that rareearth fluorocarbonate is first decomposed to form rare-earth oxyfluoride and CO2, and the cerium oxyfluoride is then partially oxidized by the CO2 gas. The rest cerium in these samples can be further oxidized in air at room temperature, with the oxidation efficiency of the cerium gradually increasing to above 80% in 7 d. This can be attributed to the obvious changes in the inner morphology of the roasted samples under N2 atmosphere at high temperatures, which largely induce the diffusion of the air and improves the oxidation activity of CeOF, and further induces the oxidation of CeOF by the air. XRD and XPS techniques were used to further verify the significant differences in the thermal decomposition behaviors of the bastnaesite concentrate under N2 and O2 atmosphere. Moreover, no oxidation of Pr^（3＋） to Pr^（4＋） in the roasted samples under both N2 and O2 atmosphere is observed. This gives an overall understanding of the oxidative roasting of the bastnaesite concentrate without additives.展开更多
Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent devel...Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent developments in crystal structure,luminescence and applications of phosphors for wide color gamut LED backlight are introduced.As novel red phosphors,Mn4+activate fluoride and aluminate phosphors are advanced in quantum efficiency,thermal quenching and color saturation for their characteristic spectrum with broad excitation band and linear emission.The crystal structure and fluorescence properties of Mn4+doped fluosilicate,fluorogermanate,fluotitanate,as well as Sr4 Al14O25,CaAl12O19 and BaMgAl10O17 phosphors are discussed in detail.A serial of narrow-band red-emitting Eu2+,Eu3+and Pr3+-doped nitride silicates and molybdate phosphors are also introduced.Rare-earth-doped oxynitride and silicate green-emitting phosphors have attracted more and more attention because of the wide excitation,narrow emission,high quenching temperature,high quantum efficiency,such as β-sialon:Eu2+,Ba3Si6O12N2:Eu2+,MSi2O2N2:Eu2+(M=Ca,Sr,Ba),y-AlON:Mn2+and Ca3Sc2Si3O12:Ce3+.All above phosphors demonstrate their adaptability in wide color gamut LCD display.Especially for Mn4+doped fluosilicate red phosphor and β-sialon:Eu2+green phosphor.To achieve an ultra-high color gamut in white LED backlight and against the OLED,innovative narrow-band-emission red and green phosphor materials with independent intellectual property rights are continuously pursed.展开更多
A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology ...A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La_3 Si_6 N_(11):Dy^(3+)/Tb^(3+) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb^(3+) concentration in La_3 Si_6 N_(11):Dy^(3+),Tb^(3+), The mechanism of energy transfer(ET) from Dy^(3+) to Tb^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. The temperaturedependent luminescence measurements of La_(2.83)Si_6 N_(11):0.1 Dy^(3+),0.07 Tb^(3+) were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white lightemitting diodes(w-LEDs) phosphor.展开更多
The development and prospect of rare earth functional biomaterials (REFB) was discussed. From 1979 to 1985, the simple REFB (salts) has been developed, and the fundamental research including forms, effects, toxicity, ...The development and prospect of rare earth functional biomaterials (REFB) was discussed. From 1979 to 1985, the simple REFB (salts) has been developed, and the fundamental research including forms, effects, toxicity, conversion in soil, and analysis methods had been finished. Then, the RE feed additive materials had been developed, and the fundamental research had also been finished. In 1990s, new REFB including RE phosphate fertilizer additive, RE conversional agricultural film additive, RE water-retraining reagent and RE seed coating reagent had been developed out rapidly. They were extended to 1.36 million hectares and big benefit had been got during the last three years. Recently, it was found that RE has some function of antagonizing heavy metals and degradating organophosphors pesticide, so the REFB will be studied as a focus once more, and will become one of the important methods of guaranteeing food security in the future.展开更多
Solid oxide fuel cell is a promising energy conversion system which converts chemical energy into electrical energy directly. Electrolyte is the key component and determines the working temperature. In this paper,ceri...Solid oxide fuel cell is a promising energy conversion system which converts chemical energy into electrical energy directly. Electrolyte is the key component and determines the working temperature. In this paper,ceria and scandia co-doped zirconia electrolytes sintered from 1300 to 1550 ℃ were chosen as research objects. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy were performed to characterize the ceramic samples. The effects of grain size and grain boundary element segregation on the electrical conductivity were focused. Electrochemical impedance spectroscopy was used to calculate the bulk, grain boundary and specific grain boundary conductivity. Results show that the bulk and grain boundary ionic conductivity increases with the increasing grain size.However, the specific grain boundary conductivity decreases with the increasing grain size. This is explained by the fact that Sc^(3+) is segregated at the grain boundary, which leads to higher oxygen vacancy concentration when sintered at lower temperature.展开更多
(Nd(1-x)Cex)(12)Fe(77)Ti5B6(x=0,0.2,0.3,0.4,0.6,0.8)alloys were prepared by melt-spinning and annealing techniques.The phase constitutions,microstructures and magnetic properties were investigated by powder X-ray diff...(Nd(1-x)Cex)(12)Fe(77)Ti5B6(x=0,0.2,0.3,0.4,0.6,0.8)alloys were prepared by melt-spinning and annealing techniques.The phase constitutions,microstructures and magnetic properties were investigated by powder X-ray diffraction(XRD),a differential scanning calorimeter(DSC),a vibrating sample magnetometer(VSM)and a transmission electron microscope(TEM).It is found that with the increase of Ce content,the coercivity of the(Nd(1-x)Cex)(12)Fe(77)Ti5B6 alloys reaches maximum first and then decreases.The maximum coercivity reaches 18.5 kOe obtained in the sample of 20%Ce substituted which is 34%higher than the Ce-free sample.TEM results reveal that the micro structure refinement effect is responsible for the coercivity improvement.This phenomenon implies that in some cases,Ce and Ti co-doping is more beneficial to improving of the coercivity than Ti single doping in Nd-Fe-B alloys.With further Ce addition,magnetic properties deteriorate due to the formation of CeFe2 and TbCu7-type phases.展开更多
基金Project supported by the National Natural Science Foundation of China(51501016)
文摘In order to develop a highly sensitive material for nondestructive testing(NDT),(Tb_(0.3) Dy_(0.7))Fe_(1.95) thin films were deposited on FeCo substrates at room temperature by magnetron sputtering and annealed.The magnetostrictive properties and the detection efficiency of the composite films were investigated.Results demonstrate that the detection efficiency roughly shows regular consistency with the magnetostrictive strain of the TbDyFe films. Heat treatment has a great effect on the crystalline state and the magnetostrictive strain of the composite materials. The as-deposited(Tb_(0.3) Dy_(0.7))Fe_(1.95) films are amorphous, and the saturation magnetostriction(ls) is only 90 ppm. However, the nanostructured crystalline REFe2 is partially separated out in amorphous matrix after annealing at 600C for 1 h, and the ls increases to 265 ppm. Simultaneously, the detection efficiency of the composite materials is obviously improved compared to that of the as-deposited films. The detection signal of traditional FeCo strip is0.4 V at the excitation power of 1.0 P and frequency of 128 kHz and that of the strip increases significantly by depositing one layer of(Tb_(0.3) Dy_(0.7))Fe_(1.95) film. The detection signal of the composite material annealed at 600C is the best, even reaching saturation value of 2.5 V(1.0 P, 128 kHz). The results may provide us with a method for preparing new materials for NDT.
文摘Progress of studies on various multi-color long afterglow luminescence materials was reviewed.Two luminescent mechanism of long afterglow behavior were discussed.Further research and development prospects about the materials were proposed.
基金Project supported by the Ministry of Science and Technology of China (2006CB601104)
文摘With Al2O3, Dy2O3, and SiO2 as starting materials, the basic glass of Al2O3-Dy2O3-SiO2 system was prepared by conventional melting technology, and their thermal expansion coefficients （TECs） at different anneal time were investigated. TECs of the basic glass, which were heat-treated under different temperature, were also investigated. The result showed that TECs of the basic glass gradually approached a fixed value as the anneal time was extended, which suggested that most of the inner stress had been eliminated. After heat treatment, the contents of Dy2O3, Dy2Si2O7, and a new crystal increased up to 1200 ℃ and decreased below 1250 ℃, which was consistent with the TEC change of crystallized samples. This suggests that the crystal has a direct effect on TECs of the crystallized samples.
基金supported by the National Key Research and Development Program of China(2022YFB3505503)the National Natural Science Foundation of China(52201230)+2 种基金the Key R&D Program of Shandong Province(2022CXGC020307)the China Postdoctoral Science Foundation(2022M71204)the Beijing NOVA Program(Z211100002121092).
文摘The grain boundary diffusion process(GBDP)has proven to be an effective method for enhancing the coercivity of sintered Nd-Fe-B magnets.However,the limited diffusion depth and thicker shell struc-ture have impeded the further development of magnetic properties.Currently,the primary debates re-garding the mechanism of GBDP with Tb revolve around the dissolution-solidification mechanism and the atomic substitution mechanism.To clarify this mechanism,the microstructure evolution of sintered Nd-Fe-B magnets during the heating process of GBDP has been systematically studied by quenching at different tem peratures.In this study,it was found that the formation of TbFe_(2) phase is related to the dis-solution of _(2)Fe_(14)B grains during GBDP with Tb.The theory of mixing heat and phase separation further confirms that the Nd_(2)Fe_(14)B phase dissolves to form a mixed phase of Nd and TbFe_(2),which then solidifies into the(Nd,Tb)_(2)Fe_(14)B phase.Based on the discovery of the TbFe_(2) phase,the dissolution-solidification mechanism is considered the primary mechanism for GBDP.This is supported by the elemental content of the two typical core-shell structures observed.
基金National Key Research and Development Program of China(2022YFB3504402,2023YFB3610101)。
文摘AlScN piezoelectric films prepared by AlSc alloy sputter targets are essential materials for 5G radio frequency filters.The thermophysical properties of AlSc alloy targets are closely related to their welding processes and applications.Al-xSc alloys(x=5,10,15,20,25,at%)were prepared by vacuum induction melting,whose purity is mainly determined by the raw materials and the production process.The results reveal that as the Sc content increases from 5at%to 20at%,the volume fraction of the Al_(3)Sc phase in the alloy increases from 26.9%to 80.2%,and the average grain size of the Al_(3)Sc phase increases from 12.9μm to 67.7μm during this period.Additionally,both the coefficient of thermal expansion(CTE)and thermal conductivity(TC)of AlSc alloys exhibit a downward trend.Based on experimental data and first-principles calculations,the effective medium theory and the Turner model effectively predict the TC and CTE of Al-xSc alloys.The optimal characteristic parameter(k0)of the Turner model is determined to be 50.The model predictions align well with the experimental results.
基金Project supported by the National Key R&D Program of China (2023YFB3506703)。
文摘Ti-Gd alloys with Gd contents of 2 wt%-8 wt% were prepared,and the influence of Gd content on the microstructure,mechanical properties,corrosion behavior,neutron absorption property and density of the alloy weas investigated.The micro structure changes from full lamellar α phase to fine equiaxed crystals,and the area fraction of Gd-rich phase decreases from 3.2% to 1.8% and then increases to 9.1%.Gd has three existing forms:pure Gd,compound oxide of Gd_(2)TiO_(5)and/or Gd_(2)O_(3)and solidifies in the Ti matrix.Ti-4Gd exhibits the best mechanical properties,its tensile strength and elongation is 102 MPa and 49%,respectively.The neutron transmittancy of Ti-8Gd alloy in water is the lowest,which is 3.75%.The corrosion rate of Ti-Gd alloy is 0.00097-0.00238 mm/a,which meets the corrosion standard of small-scale nuclear reactors and containers for spent fuel.
基金Project supported by the Major Research Plan of the National Natural Science Foundation of China(91962211)the National Key Research and Development Program of China(2021YFC2902202)the Key Research and Development Program of Guangxi Province(Guike-AB22080056)。
文摘Aluminum is the main impurity of the weathered crust elution-deposited rare earth ore(WCED-REO).Efficient leaching of rare earths and low leaching of aluminum are of great importance for the leaching of the WCED-REO.The effects of pH,MgSO_(4) concentration and Al^(3+)concentration of the leaching agent solution on the column leaching behaviors of WCED-REO using magnesium sulfate were investigated.Experimental data show that controlling the MgSO_(4) concentration to 0.15 mol/L,pH of the leaching agent solution to 2,the leaching amount of aluminum from the rare earth ore gradually decreases with the increase of Al^(3+)concentration in the leaching agent solution,indicating that Al^(3+)in the leaching agent solution may act as leaching agent to participate in the ion exchange of RE3+,but the leaching amounts of rare earths change insignificantly as the Al^(3+)concentration is increased.Increasing the MgSO_(4) concentration is beneficial to the leaching of aluminum,and when the Al^(3+)concentration is 0.04 mol/L(Al accumulation),the amount of Al^(3+)leached from the rare earth ore increased gradually with increasing the MgSO_(4) concentration.The pH of the leaching agent solution has a significant influence on the leaching of aluminum in the rare earth ore,and the leaching amount of aluminum from the rare earth ore increases gradually with decreasing the pH.When the Al^(3+)conce ntration is 0.04 mol/L(Al accumulation)and the pH of the leaching agent solution is above 2.0,the aluminum in the leaching agent solution can be back-adsorbed onto the rare earth ore,and the amount of the back-adsorbed Al^(3+)increases with increasing the pH of the leaching agent solution.The injection rate of the leaching agent solution has slight effect on the leaching behavior of rare earths and aluminum.In summary,leaching of Al^(3+)and consumption of MgSO_(4) can be reduced by regulating the accumulation of aluminum,MgSO_(4) concentration and pH.
基金supported by the National Key Research and Development Program(2021YFB3501103)Guiding Local Funding Projects for Scientific and Technological Development by Central Government in Hebei(216Z1402G)Youth Fund of GRINM Group Co.,Ltd.
文摘The lanthanum-cerium-based slurry(LC-slurry)is extensively utilized in the chemical mechanical polishing(CMP)of TFT-LCD glass substrates,optical lenses,and other glass products.Sodium hexametaphosphate(SHMP),as a dispersant,is commonly employed to enhance the dispersion properties of LCslurry for improved polishing performance.However,the tendency of sedimentation to form a compacted sediment layer,which is challenging to redisperse,increases storage difficulty and polishing equipment failure risk,thereby limiting its utilization in CMP.In the present study,sodium carboxymethylcellulose(CMC-Na),a long-chain organic polymer,was employed to enhance the redispersibility of LC-slurry containing SHMP.A comprehensive investigation was conducted on the influence of CMC-Na dosage and slurry pH on dispersibility,redispersibility and polishing performance.Additionally,an analysis was carried out to elucidate the underlying mechanism behind the effect of CMC-Na.The study demonstrates that the LC-slurry,containing 250 ppm SHMP and 500 ppm CMC-Na,exhibits excellent dispersibility and redispersibility.Further polishing tests demonstrate that compared to the LC-slurry containing only SHMP,utilizing the slurry containing both SHMP and CMC-Na at various pH for polishing thin film transistor liquid crystal display(TFT-LCD)glass substrates results in a reduction of both material removal rate(MRR)and surface roughness(Sa).Specifically,when adjusting the slurry to a pH range of 5-6,the MRR can reach up to 330 nm/min,which closely approximates the MRR achieved by LC-slurry containing only 250 ppm SHMP at corresponding pH values.Meanwhile,after polishing,the surface roughness of the glass substrate measures approximately 0.47 nm.
基金supported by the National Key Research and Development Program of China(2020YFC1909104)National Natural Science Foundation of China(52274355)Major Science and Technology Project of Inner Mongolia Autonomous Region(2021ZD0016)。
文摘The Mountain Pass mine is recognized as one of the world's primary sources of rare earth minerals.These rare earth minerals mainly consist of bastnaesite and a small amount of monazite phosphate,which cannot be decomposed and recovered through conventional oxidative roasting and hydrochloric acid leaching process.An efficient,clean,and economical process called the"combined method"was proposed for the utilization of the Mountain Pass mine to extract rare earths from Mountain Pass rare earth concentrate(MPREC).The main steps of this process include weak oxidation atmosphere roasting,step leaching of hydrochloric acid,solid-liquid separation,the monazite slag with sulfuric acid roasting water leaching,etc.In this paper,the roasting process of MPREC under a weak oxidation atmosphere was investigated.The study examines the thermal decomposition kinetics,phase transition process,and leaching behavior of MPREC in air/CO_(2)atmosphere.Results show that,the activation energy(Ea)for MPREC thermal decomposition in air and CO_(2)atmosphere are 146 and 320 kJ/mol,respectively.At temperature above 500℃in air or above 700℃in CO_(2)atmosphere,REOF are generated from bastnaesite through an in-situ reaction with CaO,which is decomposed from CaCO_(3),to form CaF_(2)and rare earth oxide(REO).Thus,F is regulated into solid phase.In an oxidizing atmosphere,the thermal decomposition of bastnaesite is accompanied by the rapid oxidation of Ce(Ⅲ).In co ntrast,the oxidation of Ce(Ⅲ)in a CO_(2)atmosphere is significantly inhibited.At 700℃,the oxidation rate of Ce in air is 74.09%,while in a CO_(2)atmosphere,it is only 33.83%.The hydrochloric acid leaching experiment shows that,the leaching rate of rare earth after roasting at 600℃under an air atmosphere reaches to 82.9%,and it reaches 87%after roasting at 800℃under a CO_(2)atmosphere.The reduction of Ce oxidation in a weak oxidizing atmosphere significantly improves the leaching rate of Ce.
基金supported by National Natural Science Foundation of China(52204376)Open Project of Yunnan Precious Metals Laboratory Co.(YPML-2023050266)Youth Foundation of Hebei Province(E2022103007)。
文摘NO catalytic oxidation is the key performance of the diesel oxidation catalyst(DOC).We present a facile deposition method for the core-shell rare-earth manganese-zirconium composite oxide that shows the Mn mullite phase uniform loading on the surface of zirconium-based composite(YMO/CYZO),which demonstrates a superior NO oxidation catalytic performance in simulated diesel combustion conditions and better thermal stability than mullite phase YMn_(2)O_(5)oxide.The NO oxidation at 250℃over YMO/CYZO-a approaches 25.2%in contrast to 13.52%over YMn_(2)O_(5)-a.Then the catalytic performance of YMO/CYZO,YMO and commercial 1 wt%Pt/Al_(2)O_(3)in a NO+O_(2)atmosphere was compared.The maximum conversion rate of YMO/CYZO to NO oxidation is 89.6%at 274℃with a GHSV of 50000 h^(-1),and the performance is superior to that of YMO(82.8%at 293℃)and 1 wt%Pt/Al_(2)O_(3)(68.6%,335℃).The NO-temperature programmed desorption(NO-TPD)and diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)results reveal that YMO/CYZO has multiple NO adsorption sites and high storage capacity.Furthermore,density functional theory(DFT)calculation indicates that YMO/CYZO has lower oxygen vacancy formation energies(E_(v)=0.93 eV)and favorable NO adsorption energies(E_(ads)=2.1 eV).Moreover,in situ X-ray photoelectron spectroscopy(XPS)characterization shows that the core-shell structure of YMO/CYZO has the potential to transmit active oxygen species to help realize Mn3+to Mn4+during the reaction process to enhance the conversion of NO*molecules,while NO oxidation reactions follow the MvK mechanism.
基金Project supported by the National Key Research and Development Program(2021YFB3501101)Beijing Nova Program(20220484827)+2 种基金National Natural Science Foundation of China(52304370)Central Government Guidance Local Science and Technology Development Fund Project of Hebei Province(236Z4102G)Natural Science Foundation of Hebei Province(E2022103012)。
文摘Rare earth carbonates are essential precursors for the synthesis of oxide materials.In this study,we utilized in situ monitoring equipment to explore the alterations in the crystallization during the coprecipitation synthesis of cerium carbonate.By controlling the crystallization pathway and in the absence of any te mplating agents,we successfully synthesized a unique sphe rical self-assembled cerium oxide particle(Ceria-S).The Ceria-S exhibits excellent polishing performance.The crystallization process of cerium carbonate at 50℃persists for roughly 50 min.During the initial stages of crystallization from 0 to t_(3),the precipitated particles are amorphous.This is followed by a plateau phase of crystal growth from t_(3)to t_(5).Subsequently,during the burst crystallization phase from t_(5)to t_(6),Ce_(2)(CO_(3))_(3)·6H_(2)O and Ce_(2)O(CO_(3))_(2)·nH2O are formed,exhibiting a rod-like crystal morphology.By rapidly drying the precipitated particles at 60℃for 10 min and calcining,Ceria-S is obtained.The Ceria-S,with an average diameter of 180 nm,is assembled from primary cerium oxide nanoparticles of approximately 15 nm.Owing to the self-assembly structure of cerium oxide spherical nanoparticles,they exhibit a significantly larger specific surface area,resulting in an elevated concentration of Ce^(3+)as high as 35.5%.The Ceria-S exhibits a polishing removal rate of 420 nm/min,effectively decreasing the surface roughness(S_(a))of K9 glass from 1.605 to 0.404 nm.
基金supported by National Natural Science Foundation of China (52204376)Youth Foundation of Hebei Province (E2022103007)+1 种基金Open Project of Yunnan Precious Metals Laboratory Co.(YPML-20240502059)Young Elite Scientists Sponsorship Program by CAST (2021QNRC001)。
文摘There has been a continuous effort to improve the thermal stability of subnanometric platinum(Pt)cluster(<2 nm) catalyst because Pt cluster on CeO_(2) support can be mobile and aggregated into nanoparticle on heating at elevated temperatures,yet this great challenge remains.In this study,a strategy is reported to improve the thermal stability of subnanometric Pt cluster by hydrothermal deposition method.Based on this method,zirconium(Zr) was precisely doped on surface of Ce_(0.95)Zr_(0.05)O_(2) by accurately controlling Pt subnanometric cluster size.The surface doping of Zr is favorable for forming the Zr-O-Ce site and activating surface lattice oxygen atoms,which results in strong electronic interactions to stabilize the Pt subnanometric cluster.After high-temperature aging treatment at 1000℃/4 h,the single atom Pt supported on CeO_(2) is aggregated into larger sized(>3 nm) nanoparticle.In contrast,the single atom Pt supported on Ce_(0.95)Zr_(0.0)5O_(2) displays less agglomeration into subnanometric cluster with size of(1.4±0.3) nm.Moreover,the CO oxide catalytic performance of Ce_(0.95)Zr_(0.0)5O_(2)-Pt is 26% and 31%higher than that of CeO_(2)-Pt and commercial Al_(2)O_(3)-Pt catalysts,respectively.The experimental and density functional theory(DFT) calculations indicate that the Zr-O-Ce site and Pt subnanometric cluster interface have more defect sites and active oxygen species than CeO_(2)-Pt interface,which activate the Mars van Krevelen(MvK) mechanism,facilitating the catalytic performance.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3505900)
文摘The magnetic loss plays a key role in electromagnetic waves(EMW)absorption.However,the magnetic loss ability would obviously draw at high frequency,and the component lacks the dielectric loss ability,resulting in poor EMW absorption.In this work,we design a core-shell-structured Fe@Sm_(2)Fe_(17)dual magnetic nanoparticle.The 200-nm Sm_(2)Fe_(17)nanoparticles play a key role in maintaining relatively high magnetic loss ability even at high frequency.And the introduction of 3-μm Fe cubes can optimize the dielectric parameters by the interface polarization and thus enhance the impedance matching.Meanwhile,Fe cubes with easy axis vertical to six planes can absorb the EMW with different directions,leading to the enhancement of the EMW attenuation.Especially,the Fe cubes can align the moment of Sm_(2)Fe_(17)nanoparticles,which can increase exchange-coupling interaction between them to further improve the magnetic loss capacity and broaden the effective absorption bandwidth(EAB).Furthermore,the small-sized Sm_(2)Fe_(17)nanoparticles provide a rough surface,which promotes multiple reflections and scattering of the incident EMW.As a result,the optimal EMW attenuation performance with a minimum reflection loss exceeding-51.4 dB and a broadened EAB up to 6.6 GHz at 1.4 mm was achieved in Fe@Sm_(2)Fe_(17)composites with Sm/Fe of 1:12.Our work provides profound insights into developing well-coordinated magnetic-dielectric nanocomposites for EMW absorption engineering.
基金supported by the National Science and Technology Support Program of China(2015BAB16B02)the National Natural Science Foundation of China(51504034).
文摘In acid treatment technology of Baotou mixed rare earth ore,large quantities of ammonia-nitrogen wastewater are produced in the step of ammonium bicarbonate precipitation to transform rare earth sulfate.In this paper,we adopted a green precipitant magnesium bicarbonate(Mg(HCO3)2) to substitute ammonium bicarbonate to eliminate ammonia-nitrogen pollution.The effects of n(HCO3^-):n(RE^3+),aging temperature and aging time on the crystallization using Mg(HCO3)2 precipitation method were investigated.The results indicate that the rare earths could be completely recovered when n(HCO3^-):n(RE^3+) is higher than 3.15:1.The crystal water content of rare earth carbonates is affected by the aging temperature.The precipitate has a bad filterability when the aging temperature is over 40℃.This can be attributed to the less crystallized water molecules of the hydrated rare earth carbonate precipitation.The mixed rare earth carbonates are prone to be crystalline,and have a good filterability at aging temperatures below 40℃.Meanwhile,the evolution mechanism of crystalline mixed rare earth carbonates is reasonably deduced,the amorphous rare earth carbonates are first dissolute and then recrystallized.Under the optimized aging conditions,the purity of the crystalline precipitate meets the requirements of the fine product standard(GB/T 16479-2008).The filtrated could be used to produce Mg(HCO3)2,thus to realize the recycling of magnesium sulfate.
基金supported by the National Natural Science Foundation of China(51404035)Beijing Nova program(Z161100004916108)
文摘To clearly elucidate the oxidative roasting behaviors of the bastnaesite, the thermal decomposition and oxidation of the bastnaesite concentrate in inert and oxidative atmosphere have been investigated in detail. Experimental data indicated that the initial decomposition temperature of the concentrate under N2 atmosphere is 150 ℃ higher than that under O2 atmosphere,most likely because the oxidation of the cerium induces the decomposition of the concentrate. For the roasted samples under N2 atmosphere at500 ℃ and above,the oxidation efficiency of the cerium is 19.8%-26.8% because of the fact that rareearth fluorocarbonate is first decomposed to form rare-earth oxyfluoride and CO2, and the cerium oxyfluoride is then partially oxidized by the CO2 gas. The rest cerium in these samples can be further oxidized in air at room temperature, with the oxidation efficiency of the cerium gradually increasing to above 80% in 7 d. This can be attributed to the obvious changes in the inner morphology of the roasted samples under N2 atmosphere at high temperatures, which largely induce the diffusion of the air and improves the oxidation activity of CeOF, and further induces the oxidation of CeOF by the air. XRD and XPS techniques were used to further verify the significant differences in the thermal decomposition behaviors of the bastnaesite concentrate under N2 and O2 atmosphere. Moreover, no oxidation of Pr^（3＋） to Pr^（4＋） in the roasted samples under both N2 and O2 atmosphere is observed. This gives an overall understanding of the oxidative roasting of the bastnaesite concentrate without additives.
基金Project supported by National Key Research and Development Program(2017YFB0404301)
文摘Wide color gamut(WCG) backlight for liquid crystal display(LCD) utilizing white light-emitting diodes(LED) has attracted considerable attention for their high efficiency and color reduction.In this review,recent developments in crystal structure,luminescence and applications of phosphors for wide color gamut LED backlight are introduced.As novel red phosphors,Mn4+activate fluoride and aluminate phosphors are advanced in quantum efficiency,thermal quenching and color saturation for their characteristic spectrum with broad excitation band and linear emission.The crystal structure and fluorescence properties of Mn4+doped fluosilicate,fluorogermanate,fluotitanate,as well as Sr4 Al14O25,CaAl12O19 and BaMgAl10O17 phosphors are discussed in detail.A serial of narrow-band red-emitting Eu2+,Eu3+and Pr3+-doped nitride silicates and molybdate phosphors are also introduced.Rare-earth-doped oxynitride and silicate green-emitting phosphors have attracted more and more attention because of the wide excitation,narrow emission,high quenching temperature,high quantum efficiency,such as β-sialon:Eu2+,Ba3Si6O12N2:Eu2+,MSi2O2N2:Eu2+(M=Ca,Sr,Ba),y-AlON:Mn2+and Ca3Sc2Si3O12:Ce3+.All above phosphors demonstrate their adaptability in wide color gamut LCD display.Especially for Mn4+doped fluosilicate red phosphor and β-sialon:Eu2+green phosphor.To achieve an ultra-high color gamut in white LED backlight and against the OLED,innovative narrow-band-emission red and green phosphor materials with independent intellectual property rights are continuously pursed.
基金supported by the National Key Research and Development Plan(2017YFB0404300,2017YFB0404301)
文摘A novel white-light emitting single-phase phosphor La_3 Si_6 N_(11):Dy^(3+),exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La_3 Si_6 N_(11):Dy^(3+)/Tb^(3+) were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb^(3+) concentration in La_3 Si_6 N_(11):Dy^(3+),Tb^(3+), The mechanism of energy transfer(ET) from Dy^(3+) to Tb^(3+) is confirmed according to the excitation,emission spectra and decay lifetimes curve. The temperaturedependent luminescence measurements of La_(2.83)Si_6 N_(11):0.1 Dy^(3+),0.07 Tb^(3+) were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white lightemitting diodes(w-LEDs) phosphor.
文摘The development and prospect of rare earth functional biomaterials (REFB) was discussed. From 1979 to 1985, the simple REFB (salts) has been developed, and the fundamental research including forms, effects, toxicity, conversion in soil, and analysis methods had been finished. Then, the RE feed additive materials had been developed, and the fundamental research had also been finished. In 1990s, new REFB including RE phosphate fertilizer additive, RE conversional agricultural film additive, RE water-retraining reagent and RE seed coating reagent had been developed out rapidly. They were extended to 1.36 million hectares and big benefit had been got during the last three years. Recently, it was found that RE has some function of antagonizing heavy metals and degradating organophosphors pesticide, so the REFB will be studied as a focus once more, and will become one of the important methods of guaranteeing food security in the future.
基金Project supported by National Natural Science Foundation of China(51504034)Beijing Nova Program(Z181100006218030)
文摘Solid oxide fuel cell is a promising energy conversion system which converts chemical energy into electrical energy directly. Electrolyte is the key component and determines the working temperature. In this paper,ceria and scandia co-doped zirconia electrolytes sintered from 1300 to 1550 ℃ were chosen as research objects. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy were performed to characterize the ceramic samples. The effects of grain size and grain boundary element segregation on the electrical conductivity were focused. Electrochemical impedance spectroscopy was used to calculate the bulk, grain boundary and specific grain boundary conductivity. Results show that the bulk and grain boundary ionic conductivity increases with the increasing grain size.However, the specific grain boundary conductivity decreases with the increasing grain size. This is explained by the fact that Sc^(3+) is segregated at the grain boundary, which leads to higher oxygen vacancy concentration when sintered at lower temperature.
基金Project supported by the National Key Research and Development Program of China(2016YFB0700902)
文摘(Nd(1-x)Cex)(12)Fe(77)Ti5B6(x=0,0.2,0.3,0.4,0.6,0.8)alloys were prepared by melt-spinning and annealing techniques.The phase constitutions,microstructures and magnetic properties were investigated by powder X-ray diffraction(XRD),a differential scanning calorimeter(DSC),a vibrating sample magnetometer(VSM)and a transmission electron microscope(TEM).It is found that with the increase of Ce content,the coercivity of the(Nd(1-x)Cex)(12)Fe(77)Ti5B6 alloys reaches maximum first and then decreases.The maximum coercivity reaches 18.5 kOe obtained in the sample of 20%Ce substituted which is 34%higher than the Ce-free sample.TEM results reveal that the micro structure refinement effect is responsible for the coercivity improvement.This phenomenon implies that in some cases,Ce and Ti co-doping is more beneficial to improving of the coercivity than Ti single doping in Nd-Fe-B alloys.With further Ce addition,magnetic properties deteriorate due to the formation of CeFe2 and TbCu7-type phases.
