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
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
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
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
To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorp...To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions.The results revealed that the adsorption of Dy and Al,as well as the desorption of K,followed the Langmuir model.The maximum ion-exchangeable capacity of Dy was higher(9.39 mmol.kg^(-1))than that of Al(6.30 mmol.kg^(-1)).The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were2.0 and 2.6.The analysis of X-ray absorption fine structure(XAFS)and density functional theory(DFT)revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds.Dy was adsorbed as[Dy(H_(2)O)_(10)]^(3+),and Al was adsorbed as[Al(OH)_(2)(H_(2)O)_(4)]^(+).In particular,the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite.Based on the above insights,the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances(6.04 A for Dy and 3.69 A for Al)and lower adsorption energies(-223.72 kJ.mol^(-1)for Dy and-268.33 kJ.mol^(-1)for Al).The maximum ionexchangeable capacity is related to the change of the surface electrical properties of kaolinite.The zeta potential was increased to-7.3 mV as the protonation resulted from aluminum adsorption,while Dy adsorption had a minor effect,maintaining a value of-17.5 m V.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
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 this paper,a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO_(4)as a leaching agent.The results indicate that with increasing the concentration of MgSO_...In this paper,a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO_(4)as a leaching agent.The results indicate that with increasing the concentration of MgSO_(4)from 0.5 wt%-1.0 wt%to 2.0 wt%-4.0 wt%,the peak concentrations of rare earths increase from 1.87 to 3.59 to 5.49-10.21 g/L,and the collection periods of leach solution are sho rtened from 0.85 to 1.54 to 0.31-0.47(liquid-to-ore ratio).When the rare earth ore is leached with leaching agent solution with high initial pH(3.0-5.0),the rare earths and aluminum are predominantly leached by Mg^(2+)instead of H+.However,H+participate in the leaching process of rare earths and aluminum at lower initial pH(1.5-3.0)of the leaching agent solution.Especially,when the initial pH of leaching agent solution is 2.0,a large amount of aluminum is leached when the liquid-to-ore ratio is greater than 1.2.Based on the above insights,increasing the initial pH(3.0-5.0)of leaching agent solution in the injection stage using high-concentration MgSO_(4)(>1.0 wt%)can increase the peak concentration of rare earths in the leach solution and shorten the collection period.However,in the injection stage using low MgSO_(4)concentration(<1.0 wt%),an initial pH of leaching agent solution of 2.0 is selected to reduce the leaching amount of aluminum and the consumption of MgSO_(4).Comparing to the Leaching process using constant MgSO_(4)concentration(2.0 wt%,initial pH of 5.0),the leaching efficiency of rare earths using a multi-stage leaching process is approximately equal(about 94.6%)under optimal conditions.The leaching amount of aluminum is reduced by 16.9%.The consumption of MgSO_(4)is reduced by 67.1%.展开更多
As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials,many strategies have been utilized to improve the oxygen storage capacity.Here in this study,we report a ...As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials,many strategies have been utilized to improve the oxygen storage capacity.Here in this study,we report a simple and facile approach to prepare a SO_(4)^(2-)-modified La,Y-doped ceria-zirconia material(SO/CZLY-f)with high oxygen storage capacity.Due to the additional redox process between SO_(4)^(2-)and S^(2-),oxygen storage capacity of SO/CZLY-f(745.3μmol O_(2)/g)is about 1.6 times higher than that of La,Ydoped ceria-zirconia material without SO_(4)^(2-)modification.Moreover,the catalytic activities and stability of the corresponding Pd-only three-way catalyst were measured.Compared to that of Pd@CZLY-f,the operation window of CO,full conversion temperature of HC and NO over Pd@SO/CZLY-f are obviously widened and lowered,respectively.After aging treatment at 1100℃for 4 h,the superiority of aged Pdloading composite is still maintained.展开更多
Ultra-high purity Yb_(2)O_(3) is the critical material of many high-tech materials such as laser glass and fiber,in which impurities seriously affect the laser color quality,intensity and power.In order to reduce the ...Ultra-high purity Yb_(2)O_(3) is the critical material of many high-tech materials such as laser glass and fiber,in which impurities seriously affect the laser color quality,intensity and power.In order to reduce the influence of impurities on the properties of laser materials,the purification process of Yb_(2)O_(3) was studied by comparing two kinds of resins(RT-1 and RS-1)using improved ion-exchange chromatography(IEC)method.In this study,through the synergistic improvement of resin structure and eluting system,the environmental pollution caused by ammonia water in the traditional IEC method was reduced,and the requirements of high temperature and pressure were cut.The ion exchange behavior and impurity removal mechanism in the resin column during the loading and eluting process were compared and analyzed.The experimental results show that RS-1 resin is all superior to RT-1resin in elements selectivity,ion exchange capacity and impurities removal rate.After separation and purification by IEC with RS-1 resin,the total removal rate of rare earth impurities was 77.59%and that of non-rare earth impurities was 95.86%when Yb recovery was more than 70%,both higher than that of RT-1 resin(73.26%and 83.18%).This indicates that the improved IEC method is very effective in separating and removing different metal impurities from Yb_(2)O_(3).The pilot test results of IEC method separating and purifying Yb_(2)O_(3) with RS-1 resin show that the purity of Yb_(2)O_(3) can be increased from 99.9929%to 99.9997%by IEC method.It has exhibited huge potential of preparing ultra-high purity Yb_(2)O_(3),especially the deep removal of non-rare earth impurities.展开更多
Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,ph...Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,physical and chemical properties of multi-doped cerium zirconium mixed oxides,a series of La and Y doped cerium zirconium mixed oxides(CZLYs)were synthesized via a co-precipitation method,and the physical and chemical properties of CZLYs were systemically characterized by XRD,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-TPR).The results show that co-precipitation temperature is an important parameter to influence the crystal size,oxygen storage capacity and thermal stability of CZLYs.When the co-precipitation temperature was 60℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.展开更多
In light of the difficult removal of harmful impurity tungsten(W)in Ce metal,in this paper a combined vacuum gravity sedimentation-directional solidification method was innovatively designed and the W separation behav...In light of the difficult removal of harmful impurity tungsten(W)in Ce metal,in this paper a combined vacuum gravity sedimentation-directional solidification method was innovatively designed and the W separation behavior was investigated.By reducing the electron beam power instantly and gradually at reduction rates of 1,3 and 5 kW/min,it is found that W is enriched at the bottom of ingots as the melt solidifies.The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases,attributed to the k0(W)>1 andρ(W)>ρ(Ce).Overall,the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot,and the purity of Ce increases from 99.932 wt%to 99.995 wt%by this combined method.Additionally,this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.展开更多
With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(...With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(TWCs).To guide the design of next-generation TWCs,it is essential to further develop our understanding of the relationships between microstructure and catalytic performance.Here,Rh/CeO_(2)–ZrO_(2) catalysts were synthesized with different Rh metal dispersion by using a combination of the wet impregnation method and reduction treatment.These catalysts included Rh single-atom catalysts,cluster catalysts,and nanoparticle catalysts.The results showed that the Rh nanoparticle catalyst,with an average size of 1.9 nm,exhibited superior three-way catalytic performance compared to the other catalysts.Based on the catalytic activity in a series of simple reaction atmospheres such as CO+O_(2),NO+CO,and hydrocarbons(HCs)+O_(2) and operando infrared spectroscopy,we found that metallic Rh sites on Rh nanoparticles are the key factor responsible for the low-temperature catalytic performance.展开更多
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 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financially supported by the National Key Research and Development Program of China(No.2021YFC2902203)the Key Research and Development Program of Guangxi Province(No.Guike-AB22080056)+2 种基金Beijing Nova Program(No.20230484379)the Science and Technology Innovation Fund of GRINM(No.2022PD0102)the Central Government Guides Local Science and Technology Development Fund Project(No.246Z4005G)。
文摘To achieve selective leaching of ion adsorption rare earth,it is necessary to thoroughly reveal the differences in the adsorption mechanisms of aluminum and rare earth elements.In this study,we investigated the adsorption processes of Dy and Al on the surface of K–homoionic kaolinite using batch experiments and sequential chemical extractions.The results revealed that the adsorption of Dy and Al,as well as the desorption of K,followed the Langmuir model.The maximum ion-exchangeable capacity of Dy was higher(9.39 mmol.kg^(-1))than that of Al(6.30 mmol.kg^(-1)).The ion exchange stoichiometry ratios of Dy–K and Al–K derived from the Langmuir model were2.0 and 2.6.The analysis of X-ray absorption fine structure(XAFS)and density functional theory(DFT)revealed that Dy and Al were adsorbed onto kaolinite as outer-sphere hydrated complexes via hydrogen bonds.Dy was adsorbed as[Dy(H_(2)O)_(10)]^(3+),and Al was adsorbed as[Al(OH)_(2)(H_(2)O)_(4)]^(+).In particular,the adsorption of Al resulted in protonation of the hydroxyl groups on the surface of the kaolinite.Based on the above insights,the higher ion exchange stoichiometry ratios are attributed to closer adsorption distances(6.04 A for Dy and 3.69 A for Al)and lower adsorption energies(-223.72 kJ.mol^(-1)for Dy and-268.33 kJ.mol^(-1)for Al).The maximum ionexchangeable capacity is related to the change of the surface electrical properties of kaolinite.The zeta potential was increased to-7.3 mV as the protonation resulted from aluminum adsorption,while Dy adsorption had a minor effect,maintaining a value of-17.5 m V.
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)+2 种基金the Science and Technology Innovation Fund of GRINM(2022PD0102)the Major Program of Qingyuan Innovation Laboratory(00122004)the Beijing Nova Program(20230484379)。
文摘In this paper,a multi-stage leaching process for the weathered crust elution-deposited rare earth ore was proposed using MgSO_(4)as a leaching agent.The results indicate that with increasing the concentration of MgSO_(4)from 0.5 wt%-1.0 wt%to 2.0 wt%-4.0 wt%,the peak concentrations of rare earths increase from 1.87 to 3.59 to 5.49-10.21 g/L,and the collection periods of leach solution are sho rtened from 0.85 to 1.54 to 0.31-0.47(liquid-to-ore ratio).When the rare earth ore is leached with leaching agent solution with high initial pH(3.0-5.0),the rare earths and aluminum are predominantly leached by Mg^(2+)instead of H+.However,H+participate in the leaching process of rare earths and aluminum at lower initial pH(1.5-3.0)of the leaching agent solution.Especially,when the initial pH of leaching agent solution is 2.0,a large amount of aluminum is leached when the liquid-to-ore ratio is greater than 1.2.Based on the above insights,increasing the initial pH(3.0-5.0)of leaching agent solution in the injection stage using high-concentration MgSO_(4)(>1.0 wt%)can increase the peak concentration of rare earths in the leach solution and shorten the collection period.However,in the injection stage using low MgSO_(4)concentration(<1.0 wt%),an initial pH of leaching agent solution of 2.0 is selected to reduce the leaching amount of aluminum and the consumption of MgSO_(4).Comparing to the Leaching process using constant MgSO_(4)concentration(2.0 wt%,initial pH of 5.0),the leaching efficiency of rare earths using a multi-stage leaching process is approximately equal(about 94.6%)under optimal conditions.The leaching amount of aluminum is reduced by 16.9%.The consumption of MgSO_(4)is reduced by 67.1%.
基金Project supported by the Beijing Nova Program(Z181100006218030)Major State Research Development Program of Hebei province(20374202D)。
文摘As the oxygen redox ability shows great effects on the catalytic performances of ceria-zirconia based materials,many strategies have been utilized to improve the oxygen storage capacity.Here in this study,we report a simple and facile approach to prepare a SO_(4)^(2-)-modified La,Y-doped ceria-zirconia material(SO/CZLY-f)with high oxygen storage capacity.Due to the additional redox process between SO_(4)^(2-)and S^(2-),oxygen storage capacity of SO/CZLY-f(745.3μmol O_(2)/g)is about 1.6 times higher than that of La,Ydoped ceria-zirconia material without SO_(4)^(2-)modification.Moreover,the catalytic activities and stability of the corresponding Pd-only three-way catalyst were measured.Compared to that of Pd@CZLY-f,the operation window of CO,full conversion temperature of HC and NO over Pd@SO/CZLY-f are obviously widened and lowered,respectively.After aging treatment at 1100℃for 4 h,the superiority of aged Pdloading composite is still maintained.
基金financially supported by the National Key R&D Program of China(No.2020YFC1909004)China Postdoctoral Science Foundation(Nos.2020M680615 and 2021T140581)the Youth Fund Project of GRINM。
文摘Ultra-high purity Yb_(2)O_(3) is the critical material of many high-tech materials such as laser glass and fiber,in which impurities seriously affect the laser color quality,intensity and power.In order to reduce the influence of impurities on the properties of laser materials,the purification process of Yb_(2)O_(3) was studied by comparing two kinds of resins(RT-1 and RS-1)using improved ion-exchange chromatography(IEC)method.In this study,through the synergistic improvement of resin structure and eluting system,the environmental pollution caused by ammonia water in the traditional IEC method was reduced,and the requirements of high temperature and pressure were cut.The ion exchange behavior and impurity removal mechanism in the resin column during the loading and eluting process were compared and analyzed.The experimental results show that RS-1 resin is all superior to RT-1resin in elements selectivity,ion exchange capacity and impurities removal rate.After separation and purification by IEC with RS-1 resin,the total removal rate of rare earth impurities was 77.59%and that of non-rare earth impurities was 95.86%when Yb recovery was more than 70%,both higher than that of RT-1 resin(73.26%and 83.18%).This indicates that the improved IEC method is very effective in separating and removing different metal impurities from Yb_(2)O_(3).The pilot test results of IEC method separating and purifying Yb_(2)O_(3) with RS-1 resin show that the purity of Yb_(2)O_(3) can be increased from 99.9929%to 99.9997%by IEC method.It has exhibited huge potential of preparing ultra-high purity Yb_(2)O_(3),especially the deep removal of non-rare earth impurities.
基金the Hebei Key Research and Development Program,China(No.20374202D)the Hebei High Level Talent Team Building,China(No.205A1104H).
文摘Due to the oxygen storage and release properties,cerium zirconium mixed oxides are recognized as the key material in automotive three-way catalysts.To reveal the effects of co-precipitation temperature on structure,physical and chemical properties of multi-doped cerium zirconium mixed oxides,a series of La and Y doped cerium zirconium mixed oxides(CZLYs)were synthesized via a co-precipitation method,and the physical and chemical properties of CZLYs were systemically characterized by XRD,N_(2) adsorption−desorption,TEM,XPS,oxygen storage capacity(OSC)and hydrogen temperature programmed reduction(H_(2)-TPR).The results show that co-precipitation temperature is an important parameter to influence the crystal size,oxygen storage capacity and thermal stability of CZLYs.When the co-precipitation temperature was 60℃,the best redox properties and thermal stability of CZLYs were obtained.After thermal treatment at 1100℃for 10 h,the specific surface area and oxygen storage capacity of the corresponding aged sample were 15.42 m^(2)/g and 497.7μmol/g,respectively.In addition,a mechanism was proposed to reveal the effects of co-precipitation temperature on the structure and properties of CZLYs.
基金Project supported by the National Key Research and Development Program of China(2022YFC2905203)the NationalScience and Technology Major Project of China(J2019-VI-0023-0140)。
文摘In light of the difficult removal of harmful impurity tungsten(W)in Ce metal,in this paper a combined vacuum gravity sedimentation-directional solidification method was innovatively designed and the W separation behavior was investigated.By reducing the electron beam power instantly and gradually at reduction rates of 1,3 and 5 kW/min,it is found that W is enriched at the bottom of ingots as the melt solidifies.The enrichment effect is much better than that of single purification method and the enrichment degree increases as the beam reduction rate decreases,attributed to the k0(W)>1 andρ(W)>ρ(Ce).Overall,the minimum content of W impurity can decrease from 630 to 0.1 ppm at the top of the ingot,and the purity of Ce increases from 99.932 wt%to 99.995 wt%by this combined method.Additionally,this paper provides a new method for the removal of high density and low evaporation coefficient impurities in low vapor pressure rare earth metals.
基金supported by the National Key Research and Development Program of China(No.2022YFB3504202)the National Natural Science Foundation of China(No.52204376)Youth Foundation of Hebei Province(No.E2022103007).
文摘With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles,new challenges have arisen for the low-temperature performance of three-way catalysts(TWCs).To guide the design of next-generation TWCs,it is essential to further develop our understanding of the relationships between microstructure and catalytic performance.Here,Rh/CeO_(2)–ZrO_(2) catalysts were synthesized with different Rh metal dispersion by using a combination of the wet impregnation method and reduction treatment.These catalysts included Rh single-atom catalysts,cluster catalysts,and nanoparticle catalysts.The results showed that the Rh nanoparticle catalyst,with an average size of 1.9 nm,exhibited superior three-way catalytic performance compared to the other catalysts.Based on the catalytic activity in a series of simple reaction atmospheres such as CO+O_(2),NO+CO,and hydrocarbons(HCs)+O_(2) and operando infrared spectroscopy,we found that metallic Rh sites on Rh nanoparticles are the key factor responsible for the low-temperature catalytic performance.
