Influence of rare earth nanoparticles and inoculants on performance and microstructure of high chromium cast iron

The high chromium cast irons （HCCIs） with rare earth （RE） nanoparticles or inoculants were fabricated in the casting process. The phase compositions and microstructure were analyzed by X-ray diffraction （XRD） and optical microscopy （OM）, respectively. The hardness and impact toughness were tested by Rockwel-hardmeter and impacting test enginery. And then, the morphology of fracture was researched by scanning electron microscopy （SEM）. The results demonstrated that the phase compositions of HCCIs with addition of RE nanoparticles or inoculants which were M7C3 carbides ＋ α-Fe did not change obviously. However, the prime M7C3 carbides morphology had great changes with the increase of RE nanoparticles, which changed from long lath to granular or island shape. When the content of RE nanoparticles was 0.4 wt.%, the microstructure of high chromium cast iron was refined greatly. The microstructure of carbides was coarser when the addition of RE nanoparticles was higher than 0.4 wt.%. The hardness and impact toughness of HCCIs were improved by addition of RE nanoparticles or inoculants. The impact toughness of HCCIs was increased 36.4% with RE nanoparticles of 0.4 wt.%, but the hardness changed slightly. In addition, the adding of RE nanoparticles or inoculants could reduce the degree of the brittle fracture. Fracture never seemed regular, instead, containing lots of laminates and dimples with the increase of the RE nanoparticles. The results also indicated that the optimal addition amount of the RE nanoparticles was 0.4%, under this composition, the microstructure and mechanical property achieved the best cooperation. In addition, through the study of erosion wear rate, when adding 0.4% RE nanoparticles into the HCCIs, the erosion wear rate got the minimum 0.32×10-3 g/mm2, which could increase 51.5% compared with that without any RE nanoparticles.

Dual-functionalization based on combination of quercetin compound and rare earth nanoparticle

While the nanoparticles like La2O3 and other rare earth oxides were believed to be able to provide effective scavenging hydroxyl radical. Quercetin, a hydrophobic agent, showed some potential antibacterial activity. The present work successfully performed the surface modification of rare earth nanoparticle using facile and general strategy. In specific, the hydrophobic quercetin was grafted on the rare earth nanoparticle through the coupling with silane. The surface modified nanoparticle was characterized by Fourier-transform infrared （FTIR）, thermogravimetric analysis （TGA）, and scanning electron microscopy （SEM）. The surface modification helped to retain both the scavenging hydroxyl radical property of rare earth nanoparticle and the antibacterial activity of quercetin. This dual-function properties showed potential for application in the development of biomedicine such as antioxidant, anti-inflammatory, antibacterial and anticancer.

Coumarin derivative dye sensitized NaYGdF4:Yb,Er nanoparticles with enhanced NIR Ⅱ luminescence for bio-vascular imaging

Lanthanide-doped biocompatible nanoparticles have promising applications in near-infrared second region imaging due to their high chemical stability,enhanced photostability and sharp emission bandwidth.However,the weak light absorption capacity limits the application of rare-earth nanoparticles(RENPs) for bioimaging.We prepared a coumarin-derived dye sensitized NaYGdF4:Yb,Er nanoparticle probe,in which the organic dye enhances photon absorption through the sensitization process,improving the luminescence efficiency of the rare earth particles near 1000 and 1500 nm.In addition,good water solubility and stability of the probe are imparted by coating the particles with amphiphilic polymers distearoyl phosphatidylethanolamine-polyethylene glycol(DSPE-PEG) and polyacrylic acid.This composite probe with good biocompatibility and NIR Ⅱ luminescence properties can be used for vascular imaging,providing a tool for the detection of hematologic-related diseases.

Effect of solvent on luminescence properties of re-dispersible LaF_3:Ln^(3+)(Ln^(3+)=Eu^(3+),Dy^(3+),Sm^(3+) and Tb^(3+)) nanoparticles

LaF3：Ln3＋ （Eu3＋, Dy3＋, Sm3＋ and Zb3＋） nanoparticles were prepared in different solvents such as water, EG （ethylene gly- col）, DMSO （dimethyl sulfoxide） and their mixed solvents at a relatively low temperature of 150 ~C by simple chemical route. All the prepared samples showed hexagonal phase and exhibited spherical morphology. The highest ltmainescence intensity was observed for the samples prepared in EG than the samples prepared in other solvents. However, the sample prepared in water showed anomalously higher luminescence intensity than that of the sample prepared in DMSO.

Low-temperature electrochemical synthesis and characterization of ultrafine Y(OH)_3 and Y_2O_3 nanoparticles

Ultrafine Y（OH）3 nanoparticles were successfully deposited from an additive-free 0.005 mol/L YCl3 low-temperature bath on the steel cathode at the current density of 0.5 mA/cm2 and bath temperature of 10 oC. Heat treatment of the prepared Y（OH）3 nanoparticles at 600 oC in air led to the formation of Y2O3 nanoparticles. Thermal behavior and phase transformation during the heat treatment of Y（OH）3 were investigated by differential scanning calorimetry （DSC） and thermogramimetric analysis （TGA）. The morphologies, crystal structures and compositions of the prepared materials were examined by means of scanning and transmission electron microscopy （SEM and TEM） as well as X-ray diffraction （XRD） and FT-IR spectroscopy. The results showed that the prepared Y（OH）3 nanoparticles was essentially amorphous and composed of well dispersed ultrafine particles with size of 4 nm. After heat treatment, the obtained oxide product was well crystallized cubic phase of Y2O3 nanoparticles with the grain size of around 5 nm. It was concluded that low-temperature cathodic electrodeposition offered a facile and feasible way for preparation of ultrafine Y（OH）3 and Y2O3 nanoparticles.

Upconversion luminescence turning of NaREF4(RE=0.4Y＋0.4La＋0.2(Yb, Er, Tm))nanoparticles and their applications for detecting Rhodamine B in shrimp

Biocompatible NaREF_4（RE=0.4Y＋0.4La＋0.2（Yb,Er,Tm）（molar ratio）） upconversion nanoparticles（UCNPs） with strong visible fluorescence were synthesized by a solvothermal method and subsequent surface modification. Modulated upconversion luminescence emission spectra were obtained via changing the doping. In vitro and in vivo bioimagings were carried out with shrimps. The upconversion nanoprobes with an acidic/PEG hybrid ligand could quickly capture the basic Rhodamine-B（RB） in shrimp cells and formed a close UCNPs@RB system. The residual organic dye RB in shrimps could be detected on the basis of luminescent resonance energy transfer（LRET）. It could be rapidly addressed based on LRET detection that RB residue existed in the shrimps after incubating in the aqueous solution of RB higher than 3 μg/m L for 12 h.

Efficient removal of phosphate from aqueous solution using novel magnetic nanocomposites with Fe_3O_4@SiO_2 core and mesoporous CeO_2 shell

Fe_3O_4@SiO_2 magnetic nanoparticles functionalized with mesoporous cerium oxide（Fe_3O_4@SiO_2@mCeO_2） was fabricated as a novel adsorbent to remove phosphate from water. The prepared adsorbent was characterized by X-ray diffractometry（XRD）, transmission electron microscopy（TEM）, nitrogen adsorption-desorption and vibrating sample magnetometry（VSM）, and its phosphate removal performance was investigated through the batch adsorption studies. Characterization results confirmed that mesoporous cerium oxide was successfully assembled on the surface of Fe_3O_4@SiO_2 nanoparticles, and the synthesized adsorbent possessed a typical core-shell structure with a BET surface area of 195 m^2/g, accessible mesopores of 2.6 nm, and the saturation magnetization of 21.11 emu/g. The newly developed adsorbent had an excellent performance in adsorbing phosphate, and its maximum adsorption capacity calculated from the Langmuir model was 64.07 mg/g. The adsorption was fast, and the kinetic data could be best fitted with the pseudo-second-order kinetic model. The phosphate removal decreased with the increase of solution pH（2 to 10）, while the higher ionic strength slightly promoted the phosphate adsorption. The presence of Cl~– and SO^（2–）_4 could enhance the adsorption of phosphate whereas HCO~–_ 3 had interfering effect on the phosphate adsorption. The adsorption mechanism was studied by analyzing Zeta potential and FTIR spectroscopy, and the results indicated that the replacement of the surface hydroxyl groups by phosphate ions with the formation of inner-sphere complex played a key role in the phosphate adsorption. The spent adsorbent could be quickly separated from aqueous solution with the assistance of the external magnetic field, and the adsorbed phosphate could be effectively desorbed using a 1 mol/L NaOH solution.

Synthesis of high quality Ce：YAG nanopowders by graphene oxide nanosheet-assisted co-precipitation method

（Ce_（0.04）Y_（2.96））Al_5O_（12） phosphor nanoparticles were prepared by a modified co-precipitation method with graphene oxide（GO） nanosheets used as dispersing agent. The GO concentration is controlled at 0.0.005,0.01, 0.02, and 0.03 g/L. The addition of lamellar GO nanosheets in the precipitant solution possibly enhances both the dispersity of precursor particles and the crystallinity of phosphor nanoparticles. Pure Ce-doped YAG phase is obtained by calcining the precipitate at 1000 ℃ for 3 h. The（Ce_（0.04）Y_（2.96））Al_5 O_（12）phosphor nanoparticles have an average size of 64 nm and there is no significant change on particle size with increase of the GO concentration in precipitant solution. The luminescence property of（Ce_（0.04）Y_（2.96））Al_5O_（12） phosphor nanoparticles varies with different concentrations of GO. The photoluminescence emission intensity of the optimum sample with 0.02 g/L GO is about 1.6 times higher than the sample without using GO.