Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited ...Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.展开更多
The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice co...The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice contraction and microcrystallization was synthesized via a simple one-step method using sodium gluconate.The lattice contraction is attributed to the interaction of carbon in sodium gluconate and iron in NiFe LDH.The NiFe LDH with optimized microcrystallization and lattice contraction shows a low overpotential of 217 mV at a current density of 10 mA cm^(−2) and excellent durability of 20 h at a high current density of 100 mA cm^(−2).The results revealed that a contractive metal–oxygen bond could boost the intrinsic activity of active sites and the microcrystallization promotes an increase in the number of active sites in terms of unit area.The chemical environment of oxygen elemental characterization and resistance at different chronopotentiometry times confirm that the lattice oxygen element is indeed involved in the process of OER,supporting the lattice-oxygen-mediated mechanism of NiFe LDH.Density functional theory calculations reveal that contractive metal–oxygen bonds induced a reduction of the adsorption energy barrier of intermediate products,thus improving the intrinsic catalytic activity.The special characteristics of microcrystallization and lattice contraction of NiFe LDH provide a strategy to improve both the number and the intrinsic activity of active sites in a versatile manner.展开更多
Under hydrothermal environment,we synthesized lanthanide ions doped sodium yttrium fluoride(NaYF4:Er,Tm@NaYF4:Ce,Tb) luminescent microcrystals via an epitaxial growth technique.The structure and morphology of these mi...Under hydrothermal environment,we synthesized lanthanide ions doped sodium yttrium fluoride(NaYF4:Er,Tm@NaYF4:Ce,Tb) luminescent microcrystals via an epitaxial growth technique.The structure and morphology of these microcrystals were examined by SEM,TEM,EDS and XRD measurements.These particles show dual-mode emissions with red upconversion(UC) and green down conversion(DC) as single particles level.The mean length and diameter of these microparticles increase from 0.43 to2.26 μm and from 1.33 to 1.86 μm,respectively.Most interestingly,the photoluminescence properties of NaYF4:Er,Tm@NaYF4:Ce,Tb phosphor crystals are highly dependent on the crystallite size.The microcrystals fluoresce emit dual-mode emissions when they are solid or dispersed in solvents.Benefiting its intensive fluorescence and uniform morphology,these materials hold great potential for security and anti-counterfeiting applications.展开更多
Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material ...Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.展开更多
The effect of hydrate microcrystals such as calcium silicate hydrates ( CSH) and ettringite on the early strength of slag cements was studied. The authors explored the possibility of improving the early strength of th...The effect of hydrate microcrystals such as calcium silicate hydrates ( CSH) and ettringite on the early strength of slag cements was studied. The authors explored the possibility of improving the early strength of the slag cement by applying crystal seed technology. It is shown that slag crystal seeds make the early strength of the cement increased due to the action of hydrate crystal seeds , which speed up the hydration of clinker minerals in the nucleation of ettringite. Therefore, the early strength of the slag cement is obviously improved.展开更多
The effects of different additives on the mechanical properties, microstructures, and wear behavior of corundum abra- sives were investigated. When the number of additive phases increases, the sintering temperature an...The effects of different additives on the mechanical properties, microstructures, and wear behavior of corundum abra- sives were investigated. When the number of additive phases increases, the sintering temperature and wear rate decrease, while the densification and mechanical properties increase. The additive SiO2 is responsible for the development of equiaxed grains, whereas both CaO and MgO promote the development of platelike grains. By controlling the molar ratio of additives, it is pos- sible to obtain different microstructures. With SiO2-MgO-CaO （molar ratio, 2：1：1） as the additives and nano a-Al203 powders as the seed, microcrystalline corundum abrasives with hexagonal platelets were obtained using sol-gel process by sintering at 1300℃ for 0.5 h. The average diameter and thickness of hexagonal platelets are 1.38 μm and 360 nm respectively, the sin- gle-particle compressive strength is 26.44 N, and the wear rate is （3.06±=0.21）× 10^-7 mm^3/（N.m）.展开更多
This article presented an experimental research on washability of microcrystal graphite using float-sink tests.Chemical and X-ray analyses showed that graphite,semi-graphite,meta-anthracite,and anthracite existed toge...This article presented an experimental research on washability of microcrystal graphite using float-sink tests.Chemical and X-ray analyses showed that graphite,semi-graphite,meta-anthracite,and anthracite existed together in this microcrystal graphite sample;and the intergrowth relationship between microcrystal graphite and gangues was very complicated based on optical mineralogy research.The results of float-sink tests revealed that:for the-25+0.5 mm size fraction,about 68%(by weight)of microcrystal graphite was obtained at the density of 2.0 g/cm^3.and the float product met the standard of commercial grade W65;for the-0.5 mm size fraction,58%(by weight)of microcrystal graphite was floated at the density of 2.0 g/cm^3,which met the standard of commercial grade W70.It can be concluded that microcrystal graphite may be upgraded by dense media separation(DMS)providing a float product using as the raw materials of casting or refractories.展开更多
In this work,monodisperseβ-NaLuF_(4):Yb,Er microcrystals with intense upconversion emission were synthesized via a modified hydrothermal method.With the increase of reactant concentration,their production yield is in...In this work,monodisperseβ-NaLuF_(4):Yb,Er microcrystals with intense upconversion emission were synthesized via a modified hydrothermal method.With the increase of reactant concentration,their production yield is increased obviously,and the upconversion emission intensity inβ-NaLuF_(4):Yb,Er microcrystals is also enhanced significantly.The luminescence enhancement should be attributed to minimal internal OH defects,validated by a combination of analytical X-ray diffraction(XRD),energy dispersive spectrum(EDS),and Eu^(3+)structural probe measurements.We also reveal that high Na^(+):RE~(3+)ratio in theβ-NaLuF_(4):Yb,Er microcrystals prepared under Na^(~)+-rich reaction will arouse the increased repulsive energy ofβ-NaLuF_(4)microcrystals between F^(~)-and OH^(~)-anions and then facilitate the substitution of large OH^(-)ions by small F^(~)-ions under F^(~)--rich reaction conditions.Minimal OH^(-)concentrations can limit nonradiative relaxation and promote excitation energy harvesting for high upconversion efficiency.The presented results not only offer a facile method for the simultaneous production yield and luminescence intensity increase ofβ-NaREF_(4)microcrystals,but also uncover a better insight into the upconversion emission alterations,which is favorable to broaden their practical applications.展开更多
LaF3：Yb^3＋ , Er^＋ microcrystals were synthesized by a hydrothermal method, and then, the LaF3： Yb^3＋ , Er^＋ microcrystals were coated with silica. Phase identification of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ ...LaF3：Yb^3＋ , Er^＋ microcrystals were synthesized by a hydrothermal method, and then, the LaF3： Yb^3＋ , Er^＋ microcrystals were coated with silica. Phase identification of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ , Er^＋/SiO2 was performed via XRD. The TEM image showed that the size of LaF3： Yb^3＋ , Er^＋ was 150 nm and LaF3： Yb^3＋ , Er^＋/SiO2 presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ , Er^＋/SiO2 in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF3：Yb^3＋ , Er^＋ microcrystals. At the same time, the green luminescence photo of LaF3： Yb3＋, Er3＋/SiO2 in the PBS buffer was obtained, which indicated that the LaF3： Yb^3＋ , Er^＋/SiO2 could be used in biological applications.展开更多
An investigation was carried out of the resistance to cyclic oxidation of the as-cast normal-grained Co-30Cr-5Al alloy substrate at 1000℃ in air together with its sputtered coating of microcrystallized CoCrAl alloy g...An investigation was carried out of the resistance to cyclic oxidation of the as-cast normal-grained Co-30Cr-5Al alloy substrate at 1000℃ in air together with its sputtered coating of microcrystallized CoCrAl alloy grains sized less than 0.5μm.Acoustie emissi on counts showed that the initially formed Al_2O_3 scale on the bare alloy substrate cracked and spalled severely off after only one or two cycles on cooling and then the worse protective layer of Cr_2O_3 and CoCr_2O_4 spinel occurred on surface.While such substrate coated with sputtered microcrystallized CoCrAl alloy film was not damaged under oxidation even through 100 cycles at 1000℃.In comparison with the normal-grained alloy,the microcrystallized al- loy,coating of similar constitution exhibite excellent resistance to oxide spalling on surface.展开更多
Despite advances in treatment of chronic arthritis,there is still a strong need for the development of long-acting formulations that can enable local and sustained drug release at the inflamed tissues.In this work,we ...Despite advances in treatment of chronic arthritis,there is still a strong need for the development of long-acting formulations that can enable local and sustained drug release at the inflamed tissues.In this work,we fabricated microcrystals of an acid-sensitive stearoxyl-ketal-dexamethasone prodrug for treatment of arthritis.Microcrystals of the prodrug with two sizes were successfully engineered and showed pH-dependent hydrolysis kinetics in vitro.In a collagen-induced arthritis rat model,we evaluated the influence of particle size and injection dose on anti-inflammatory effect after intra-articular injection.Such prodrug demonstrated long-acting anti-arthritis effects with good safety.Our results indicate ketal-based prodrugs are promising for the development of long-acting injectables and may stimulate the development of new treatments for chronic diseases.展开更多
Hexagonal yttrium hydroxide fluoride microcrystals were prepared by a two-step hydrothermal routte using yttrium nitrate, sodium hydroxide and sodium fluoride as raw materials to react in propanetriol solvent. The sam...Hexagonal yttrium hydroxide fluoride microcrystals were prepared by a two-step hydrothermal routte using yttrium nitrate, sodium hydroxide and sodium fluoride as raw materials to react in propanetriol solvent. The samples were characterized by powder X-ray diffraction （XRD）, energy dispersive spectrum （EDS）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, Fourier trans- form infrared spectroscopy （FT-1R）, thermogravimetre and differential-thermogravimetric analysis （TG-DTA）, which revealed that Y（OH）2.14F0.86 microerystals were multi-branched and that the branches of Y（OH）2A4F0.86 microcrystals were composed of hierarchical tubes. This novel multi-branched and intriguing hierarchical tubular structure of yttrium hydroxide fluoride maybe has a potential application in photoelectric crystals. The formation of branched Y（OH）2.14F0.86 microcrystals with hierarchical tubular structure were due to the substitution reaction and Oswald ripening.展开更多
Micro-nano-level photonic waveguide regulation is essential for future on-chip photonic integrated systems and is still of great challenges.We report a molecular design strategy,changing the position of the methyl sub...Micro-nano-level photonic waveguide regulation is essential for future on-chip photonic integrated systems and is still of great challenges.We report a molecular design strategy,changing the position of the methyl substituent makes the arrangement of the three isomer molecules different in their respective crystals.Based on this strategy,three sheet-like crystals with different polygonal morphologies were prepared via solution self-assembly approach.The in-depth optical measurements demonstrated that these three microsheet crystals have different 2D optical waveguide performances related to the shapes.Our work provides a feasible design strategy and material preparation method for realizing precise 2D optical waveguide modulation,which lays the foundation for complex photonic integrated systems in the future.展开更多
Microcrystal muscovite composite superabsorbents（MMCSA） were prepared by water solution polymerization using acrylic acid, acrylamide and itaconic acid as comonomers and microcrystal muscovite as an inorganic additi...Microcrystal muscovite composite superabsorbents（MMCSA） were prepared by water solution polymerization using acrylic acid, acrylamide and itaconic acid as comonomers and microcrystal muscovite as an inorganic additive. Properties, such as water absorbency, salt absorbency, gel strength, water retention capacity and structure of MMCSA characterized by SEM and XRD, were investigated. Water absorbency, salt absorbency, gel strength, water retention capacity and thermostability were enhanced by incorporation of suitable amount of microcrystal muscovite. Water absorption of MMCSA was rapid, requiring 24.55 min to reach 63% of equilibrium absorbency（1218 g/g）. Microcrystal muscovite was physically combined into the polymeric network without destroying its polycrystalline structure and microcrystal muscovite composite superabsorbent had some irregular, undulant, and small microporous holes with sheet-like microcrystal muscovite distributed in the polymeric matrix.展开更多
The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal he...The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal here means an ferromagnetic single crystal with the size which is smaller than L0, and L0 is the critical value of the size of single-domain particles at the external magnetic field intensity H =0.Also, the coercive strength H(Ls) relating to the size of microcrystal Ls is given and quantitatively evaluated with the material SmCo5 as an instance.It is thus concluded that if L0 ＞ Ls ＞ LC, the antimagnetization of microcrystal will be subjected to a multi-domain process just like the particles of a size greater than L0, only if Ls ＜ LC, the anti-magnetizaton will be carried on in accordance with the Stoner-Wohlforth mechanism( LC is the maximum size of microcrystal with MHcth ).It is suggested that the material RECo5 is available to make an advanced magnet with MHC = 2 K/Mc.展开更多
Shuttle-like lead tungstate （PbWOa） microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning...Shuttle-like lead tungstate （PbWOa） microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning electron microscopy show that the lattice distortions of the PbWO4 microcrystals are reduced significantly when the annealing temperature is increased to 873 K. The result from the ultraviolet-visible diffuse reflectance spectroscopy shows that the exciton absorption appears in the sample annealed at 673 K. The self-trapped exciton luminescence due to the Jahn- Teller effect is also observed in the blue band. The interstitial oxygen ions in the WO42- groups are mainly resposible for the enhancement effect of the green luminescence of the annealed samples. The above results are supported by the spectrum analysis of the as-grown and the post-annealed samples using the X-ray photoelectron spectroscopy.展开更多
The key technology and the main mechanism of microcrystallizing leucite to reinforce dental glass ceramics were investigated.The feedstock powders were selected,mixed according to the ratios of the theoretical composi...The key technology and the main mechanism of microcrystallizing leucite to reinforce dental glass ceramics were investigated.The feedstock powders were selected,mixed according to the ratios of the theoretical composition of leucite,ball-milled,melted at 1600℃ and then cooled to room temperature quickly.The cooled clinkers were ball-milled again to 4 μm.After cold-isostatic pressure molded and air sintered at 1500℃ for 1 h,the dental glass ceramics were fabricated.They have following characteristics:excellent mechanical properties (mean compressive strength is 206.6 MPa),low sintering temperature and good reoccurrence to keep steady quality.展开更多
TEM observation on the ionitriding layer was carried out on steels W18Cr4V,38CrMoAl and 1Cr18Ni9Ti,and AES of elementary analysis was also made on the outer surface of ionitrid- ing layer of austenitic stainless steel...TEM observation on the ionitriding layer was carried out on steels W18Cr4V,38CrMoAl and 1Cr18Ni9Ti,and AES of elementary analysis was also made on the outer surface of ionitrid- ing layer of austenitic stainless steel.Perhaps due to the ion-bombardment effect,a microcrystalline structure with texture was affirmed along surface of the ionitriding layer.It may be affected by cathodic sputtering and absorption that the atomic ratio of Cr/Fe in- creases and of Ni/Fe decreases on surface of nitriding layer on austenitic stainless steel 1Cr18Ni9Ti,thus the α-phase microcrystalline structure occurrs.展开更多
The resistances against localized corrosion of 1Cr18Ni9Ti microcrystals with normal grain size and bcc structure obtained hy magnetron sputtering have been compared.The two kinds of microcrystals with (110) and (211) ...The resistances against localized corrosion of 1Cr18Ni9Ti microcrystals with normal grain size and bcc structure obtained hy magnetron sputtering have been compared.The two kinds of microcrystals with (110) and (211) textures respectively were obtained under different sputtering conditions.Both microcrystals were found to have better resistance against local- ized corrosion than the crystal with normal grain.The microcrystal with (110) preferred orientation has larger resistance to localized corrosion than that with (211) preferred orientation.展开更多
Polyhedron lead hydroxide carbonate （2PbCO3·Pb（OH）2 ） microcrystals have been prepared in solution phase via a facile method in the presence of surfactant cetyltrimethylammonium bromide （CTAB）. All the samp...Polyhedron lead hydroxide carbonate （2PbCO3·Pb（OH）2 ） microcrystals have been prepared in solution phase via a facile method in the presence of surfactant cetyltrimethylammonium bromide （CTAB）. All the samples were characterized by powder X-ray diffraction ,pattern （XRD）, field-emission scanning electron mi- croscopy （FE-SEM）, high-resolution transmission electron microscopy （HRTEM）, and selected area electron diffraction （SAED）. The possible growth mechanism was discussed. 2PbCO3·Pb（OH）2 microcrystals were found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） by transesterification of dimethyl carbonate （DMC） with phenol. Compared with some other catalysts, such as AlCl3, ZnCl2, and Mg5（CO3）4（OH）2, 2PbCO3·Pb（OH）2 microcrystals are stable and show relatively high activity at low catalyst amount. When the reaction was carried out at 180 12, with a molar ratio of phenol to DMC of 2：1, a reaction time 14 h, and a catalyst amount 0.2% （molar ratio to phenol）, the selectivity of DPC and methyl phenyl carbonate （MPC） was 14.7% and 78.8%, respectively.展开更多
基金supported by the National Natural Science Foundation of China(2106700421567008+5 种基金21263005)Project of Jiangxi Province Natural Science Foundation China(20133BAB21003)Training Programs of Innovation and Entrepreneurship for Undergraduates of Jiangxi Province(201310407046)The Landing Project of Science and Technology of Colleges and Universities in Jiangxi Province(KJLD14046)Young Scientist Training Project of Jiangxi Province(20122BCB23015)Yuanhang Engineering of Jiangxi Province~~
文摘Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.
基金National Natural Science Foundation of China,Grant/Award Numbers:51874357,51872333,U20A20123。
文摘The lattice-oxygen-mediated mechanism is considered as a reasonable mechanism for the electrochemical catalytic oxygen evolution reaction(OER)of NiFe layered double hydroxides(LDHs).A NiFe LDH with distinct lattice contraction and microcrystallization was synthesized via a simple one-step method using sodium gluconate.The lattice contraction is attributed to the interaction of carbon in sodium gluconate and iron in NiFe LDH.The NiFe LDH with optimized microcrystallization and lattice contraction shows a low overpotential of 217 mV at a current density of 10 mA cm^(−2) and excellent durability of 20 h at a high current density of 100 mA cm^(−2).The results revealed that a contractive metal–oxygen bond could boost the intrinsic activity of active sites and the microcrystallization promotes an increase in the number of active sites in terms of unit area.The chemical environment of oxygen elemental characterization and resistance at different chronopotentiometry times confirm that the lattice oxygen element is indeed involved in the process of OER,supporting the lattice-oxygen-mediated mechanism of NiFe LDH.Density functional theory calculations reveal that contractive metal–oxygen bonds induced a reduction of the adsorption energy barrier of intermediate products,thus improving the intrinsic catalytic activity.The special characteristics of microcrystallization and lattice contraction of NiFe LDH provide a strategy to improve both the number and the intrinsic activity of active sites in a versatile manner.
基金Project supported by the National Natural Science Foundation of China (21271074,51372091)the Teamwork Projects funded by the Guangdong Natural Science Foundation (S2013030012842)+1 种基金Guangdong Provincial Science&Technology Project (2015B090903074)Guangzhou Science&Technology Project (201605030005)。
文摘Under hydrothermal environment,we synthesized lanthanide ions doped sodium yttrium fluoride(NaYF4:Er,Tm@NaYF4:Ce,Tb) luminescent microcrystals via an epitaxial growth technique.The structure and morphology of these microcrystals were examined by SEM,TEM,EDS and XRD measurements.These particles show dual-mode emissions with red upconversion(UC) and green down conversion(DC) as single particles level.The mean length and diameter of these microparticles increase from 0.43 to2.26 μm and from 1.33 to 1.86 μm,respectively.Most interestingly,the photoluminescence properties of NaYF4:Er,Tm@NaYF4:Ce,Tb phosphor crystals are highly dependent on the crystallite size.The microcrystals fluoresce emit dual-mode emissions when they are solid or dispersed in solvents.Benefiting its intensive fluorescence and uniform morphology,these materials hold great potential for security and anti-counterfeiting applications.
基金the National Key R@D Program of China (Grant 2017YFA0204800)the National Natural Science Foundation of China (Grant Nos: 21533010, 21321091, 21525315, 91333116 and 21173169) for their financial supports
文摘Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH_2)_2 PbX_3(FAPbX_3), it has been considered to be a better optoelectronic material than conventional CH_3NH_3-PbX_3(MAPbX_3). Herein, we fabricated a FAPbBr_3 microcrystal-based photodetector that exhibited a good responsivity of 4000 A W-1 and external quantum efficiency up to 106% under one-photon excitation, corresponding to the detectivity greater than 1014 Jones. The responsivity is two orders of magnitude higher than that of previously reported formamidinium perovskite photodetectors. Furthermore, the FAPbBr_3 photodetector's responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W^(-1), which is four orders of magnitude higher than that of its MAPbBr_3 counterparts. The response time of this photodetector is less than 1 ms.This study provides solid evidence that FAPbBr_3 can be an excellent candidate for highly sensitive and fast photodetectors.
文摘The effect of hydrate microcrystals such as calcium silicate hydrates ( CSH) and ettringite on the early strength of slag cements was studied. The authors explored the possibility of improving the early strength of the slag cement by applying crystal seed technology. It is shown that slag crystal seeds make the early strength of the cement increased due to the action of hydrate crystal seeds , which speed up the hydration of clinker minerals in the nucleation of ettringite. Therefore, the early strength of the slag cement is obviously improved.
文摘The effects of different additives on the mechanical properties, microstructures, and wear behavior of corundum abra- sives were investigated. When the number of additive phases increases, the sintering temperature and wear rate decrease, while the densification and mechanical properties increase. The additive SiO2 is responsible for the development of equiaxed grains, whereas both CaO and MgO promote the development of platelike grains. By controlling the molar ratio of additives, it is pos- sible to obtain different microstructures. With SiO2-MgO-CaO （molar ratio, 2：1：1） as the additives and nano a-Al203 powders as the seed, microcrystalline corundum abrasives with hexagonal platelets were obtained using sol-gel process by sintering at 1300℃ for 0.5 h. The average diameter and thickness of hexagonal platelets are 1.38 μm and 360 nm respectively, the sin- gle-particle compressive strength is 26.44 N, and the wear rate is （3.06±=0.21）× 10^-7 mm^3/（N.m）.
基金financially supported by Jingfeng InternationalInvestment Co.,LtdAnhui University of Science & Technology for its support
文摘This article presented an experimental research on washability of microcrystal graphite using float-sink tests.Chemical and X-ray analyses showed that graphite,semi-graphite,meta-anthracite,and anthracite existed together in this microcrystal graphite sample;and the intergrowth relationship between microcrystal graphite and gangues was very complicated based on optical mineralogy research.The results of float-sink tests revealed that:for the-25+0.5 mm size fraction,about 68%(by weight)of microcrystal graphite was obtained at the density of 2.0 g/cm^3.and the float product met the standard of commercial grade W65;for the-0.5 mm size fraction,58%(by weight)of microcrystal graphite was floated at the density of 2.0 g/cm^3,which met the standard of commercial grade W70.It can be concluded that microcrystal graphite may be upgraded by dense media separation(DMS)providing a float product using as the raw materials of casting or refractories.
基金Project supported by the National Natural Science Foundation of China(11504317,51503177)the International Partnership Program of Chinese Academy of Sciences(121522KYSB20190022)。
文摘In this work,monodisperseβ-NaLuF_(4):Yb,Er microcrystals with intense upconversion emission were synthesized via a modified hydrothermal method.With the increase of reactant concentration,their production yield is increased obviously,and the upconversion emission intensity inβ-NaLuF_(4):Yb,Er microcrystals is also enhanced significantly.The luminescence enhancement should be attributed to minimal internal OH defects,validated by a combination of analytical X-ray diffraction(XRD),energy dispersive spectrum(EDS),and Eu^(3+)structural probe measurements.We also reveal that high Na^(+):RE~(3+)ratio in theβ-NaLuF_(4):Yb,Er microcrystals prepared under Na^(~)+-rich reaction will arouse the increased repulsive energy ofβ-NaLuF_(4)microcrystals between F^(~)-and OH^(~)-anions and then facilitate the substitution of large OH^(-)ions by small F^(~)-ions under F^(~)--rich reaction conditions.Minimal OH^(-)concentrations can limit nonradiative relaxation and promote excitation energy harvesting for high upconversion efficiency.The presented results not only offer a facile method for the simultaneous production yield and luminescence intensity increase ofβ-NaREF_(4)microcrystals,but also uncover a better insight into the upconversion emission alterations,which is favorable to broaden their practical applications.
基金Project supported by the National Natural Science Foundation of China (10474096 and 50672030)
文摘LaF3：Yb^3＋ , Er^＋ microcrystals were synthesized by a hydrothermal method, and then, the LaF3： Yb^3＋ , Er^＋ microcrystals were coated with silica. Phase identification of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ , Er^＋/SiO2 was performed via XRD. The TEM image showed that the size of LaF3： Yb^3＋ , Er^＋ was 150 nm and LaF3： Yb^3＋ , Er^＋/SiO2 presented clearly a core/shell structure with 20 nm shell thickness. The upconversion spectra of LaF3： Yb^3＋ , Er^＋ and LaF3： Yb^3＋ , Er^＋/SiO2 in solid state and in ethanol were studied with a 980 nm diode laser as the excitation source. The upconversion spectra showed that the silica shell had little effect on the properties of fluorescence of the LaF3：Yb^3＋ , Er^＋ microcrystals. At the same time, the green luminescence photo of LaF3： Yb3＋, Er3＋/SiO2 in the PBS buffer was obtained, which indicated that the LaF3： Yb^3＋ , Er^＋/SiO2 could be used in biological applications.
文摘An investigation was carried out of the resistance to cyclic oxidation of the as-cast normal-grained Co-30Cr-5Al alloy substrate at 1000℃ in air together with its sputtered coating of microcrystallized CoCrAl alloy grains sized less than 0.5μm.Acoustie emissi on counts showed that the initially formed Al_2O_3 scale on the bare alloy substrate cracked and spalled severely off after only one or two cycles on cooling and then the worse protective layer of Cr_2O_3 and CoCr_2O_4 spinel occurred on surface.While such substrate coated with sputtered microcrystallized CoCrAl alloy film was not damaged under oxidation even through 100 cycles at 1000℃.In comparison with the normal-grained alloy,the microcrystallized al- loy,coating of similar constitution exhibite excellent resistance to oxide spalling on surface.
基金We acknowledge financial support from the National Natural Science Foundation of China(51773098,81670817,81970772,21908019 and 21776044)Natural Science Foundation of Tianjin City of China(18JCYBJC28300)the Fundamental Research Funds for Central Universities(China).
文摘Despite advances in treatment of chronic arthritis,there is still a strong need for the development of long-acting formulations that can enable local and sustained drug release at the inflamed tissues.In this work,we fabricated microcrystals of an acid-sensitive stearoxyl-ketal-dexamethasone prodrug for treatment of arthritis.Microcrystals of the prodrug with two sizes were successfully engineered and showed pH-dependent hydrolysis kinetics in vitro.In a collagen-induced arthritis rat model,we evaluated the influence of particle size and injection dose on anti-inflammatory effect after intra-articular injection.Such prodrug demonstrated long-acting anti-arthritis effects with good safety.Our results indicate ketal-based prodrugs are promising for the development of long-acting injectables and may stimulate the development of new treatments for chronic diseases.
基金Project supported by the China Postdoctoral Science Foundation (20100480947 and 201104510)Postdoctoral Science Foundation of Central South University (1332-74341015511)+1 种基金Doctor Startup Foundation of Hunan University of Science and Technology (E51079)Education and Teaching Fund of Hunan University of Science and Technology (G30953)
文摘Hexagonal yttrium hydroxide fluoride microcrystals were prepared by a two-step hydrothermal routte using yttrium nitrate, sodium hydroxide and sodium fluoride as raw materials to react in propanetriol solvent. The samples were characterized by powder X-ray diffraction （XRD）, energy dispersive spectrum （EDS）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, Fourier trans- form infrared spectroscopy （FT-1R）, thermogravimetre and differential-thermogravimetric analysis （TG-DTA）, which revealed that Y（OH）2.14F0.86 microerystals were multi-branched and that the branches of Y（OH）2A4F0.86 microcrystals were composed of hierarchical tubes. This novel multi-branched and intriguing hierarchical tubular structure of yttrium hydroxide fluoride maybe has a potential application in photoelectric crystals. The formation of branched Y（OH）2.14F0.86 microcrystals with hierarchical tubular structure were due to the substitution reaction and Oswald ripening.
基金the National Natural Science Foundation of China(Nos.21971185,52173177)this project is also funded by the Collaborative Innovation center of Suzhou Nano Science and Technology(CIC-Nano)by the"111"Project of the State Administration of Foreign Experts Affairs of China。
文摘Micro-nano-level photonic waveguide regulation is essential for future on-chip photonic integrated systems and is still of great challenges.We report a molecular design strategy,changing the position of the methyl substituent makes the arrangement of the three isomer molecules different in their respective crystals.Based on this strategy,three sheet-like crystals with different polygonal morphologies were prepared via solution self-assembly approach.The in-depth optical measurements demonstrated that these three microsheet crystals have different 2D optical waveguide performances related to the shapes.Our work provides a feasible design strategy and material preparation method for realizing precise 2D optical waveguide modulation,which lays the foundation for complex photonic integrated systems in the future.
基金Funded by the Sichuan Provincial Science & Technology Pillar Program,China(2010GZ0128)the Opening Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Cheng du University of Technology,China(SKLGP2012K004)
文摘Microcrystal muscovite composite superabsorbents（MMCSA） were prepared by water solution polymerization using acrylic acid, acrylamide and itaconic acid as comonomers and microcrystal muscovite as an inorganic additive. Properties, such as water absorbency, salt absorbency, gel strength, water retention capacity and structure of MMCSA characterized by SEM and XRD, were investigated. Water absorbency, salt absorbency, gel strength, water retention capacity and thermostability were enhanced by incorporation of suitable amount of microcrystal muscovite. Water absorption of MMCSA was rapid, requiring 24.55 min to reach 63% of equilibrium absorbency（1218 g/g）. Microcrystal muscovite was physically combined into the polymeric network without destroying its polycrystalline structure and microcrystal muscovite composite superabsorbent had some irregular, undulant, and small microporous holes with sheet-like microcrystal muscovite distributed in the polymeric matrix.
文摘The expression of critical size of ferromagnetic microcrystal in an external magnetic field with an intensity of H is derived by means of comparing energies of domain structure states.The ferromagnetic microcrystal here means an ferromagnetic single crystal with the size which is smaller than L0, and L0 is the critical value of the size of single-domain particles at the external magnetic field intensity H =0.Also, the coercive strength H(Ls) relating to the size of microcrystal Ls is given and quantitatively evaluated with the material SmCo5 as an instance.It is thus concluded that if L0 ＞ Ls ＞ LC, the antimagnetization of microcrystal will be subjected to a multi-domain process just like the particles of a size greater than L0, only if Ls ＜ LC, the anti-magnetizaton will be carried on in accordance with the Stoner-Wohlforth mechanism( LC is the maximum size of microcrystal with MHcth ).It is suggested that the material RECo5 is available to make an advanced magnet with MHC = 2 K/Mc.
基金supported by the Fundamental Research Funds for the Central Universities,China(Grant Nos.ZYGX2009J046 and ZYGX2009X007)the Sichuan Provincial Young Scientists Foundation,China(Grant No.2010JQ0006)+1 种基金the Royal Society-Research Grant,UK(Grant No.RG090609)the Royal Academy of Engineering-Research Exchanges with China and India Awards in UK
文摘Shuttle-like lead tungstate （PbWOa） microcrystals are synthesized at room temperature using the precipitation method with the cetyltrimethyl ammonium bromide. Results from both the X-ray diffraction and the scanning electron microscopy show that the lattice distortions of the PbWO4 microcrystals are reduced significantly when the annealing temperature is increased to 873 K. The result from the ultraviolet-visible diffuse reflectance spectroscopy shows that the exciton absorption appears in the sample annealed at 673 K. The self-trapped exciton luminescence due to the Jahn- Teller effect is also observed in the blue band. The interstitial oxygen ions in the WO42- groups are mainly resposible for the enhancement effect of the green luminescence of the annealed samples. The above results are supported by the spectrum analysis of the as-grown and the post-annealed samples using the X-ray photoelectron spectroscopy.
文摘The key technology and the main mechanism of microcrystallizing leucite to reinforce dental glass ceramics were investigated.The feedstock powders were selected,mixed according to the ratios of the theoretical composition of leucite,ball-milled,melted at 1600℃ and then cooled to room temperature quickly.The cooled clinkers were ball-milled again to 4 μm.After cold-isostatic pressure molded and air sintered at 1500℃ for 1 h,the dental glass ceramics were fabricated.They have following characteristics:excellent mechanical properties (mean compressive strength is 206.6 MPa),low sintering temperature and good reoccurrence to keep steady quality.
文摘TEM observation on the ionitriding layer was carried out on steels W18Cr4V,38CrMoAl and 1Cr18Ni9Ti,and AES of elementary analysis was also made on the outer surface of ionitrid- ing layer of austenitic stainless steel.Perhaps due to the ion-bombardment effect,a microcrystalline structure with texture was affirmed along surface of the ionitriding layer.It may be affected by cathodic sputtering and absorption that the atomic ratio of Cr/Fe in- creases and of Ni/Fe decreases on surface of nitriding layer on austenitic stainless steel 1Cr18Ni9Ti,thus the α-phase microcrystalline structure occurrs.
文摘The resistances against localized corrosion of 1Cr18Ni9Ti microcrystals with normal grain size and bcc structure obtained hy magnetron sputtering have been compared.The two kinds of microcrystals with (110) and (211) textures respectively were obtained under different sputtering conditions.Both microcrystals were found to have better resistance against local- ized corrosion than the crystal with normal grain.The microcrystal with (110) preferred orientation has larger resistance to localized corrosion than that with (211) preferred orientation.
基金Sponsored by the National Natural Science Foundation of China (20671011,20331010,90406002 and 90406024)"111"Project (B07012) Key Laboratory of Structural Chemistry Foundation,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences(060017)
文摘Polyhedron lead hydroxide carbonate （2PbCO3·Pb（OH）2 ） microcrystals have been prepared in solution phase via a facile method in the presence of surfactant cetyltrimethylammonium bromide （CTAB）. All the samples were characterized by powder X-ray diffraction ,pattern （XRD）, field-emission scanning electron mi- croscopy （FE-SEM）, high-resolution transmission electron microscopy （HRTEM）, and selected area electron diffraction （SAED）. The possible growth mechanism was discussed. 2PbCO3·Pb（OH）2 microcrystals were found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate （DPC） by transesterification of dimethyl carbonate （DMC） with phenol. Compared with some other catalysts, such as AlCl3, ZnCl2, and Mg5（CO3）4（OH）2, 2PbCO3·Pb（OH）2 microcrystals are stable and show relatively high activity at low catalyst amount. When the reaction was carried out at 180 12, with a molar ratio of phenol to DMC of 2：1, a reaction time 14 h, and a catalyst amount 0.2% （molar ratio to phenol）, the selectivity of DPC and methyl phenyl carbonate （MPC） was 14.7% and 78.8%, respectively.
