FORMATION OF GRADIENT COATING OF Fe-BASED ALLOY WITH RARE EARTHS BY PLASMA SURFACING

A gradient coating of Fe-based alloy was manufactured with rare earths (RE) by plasma surfacing on Q235 steel substrate. The coatings were studied by using X-ray diffraction(XRD), scanning electron microscope(SEM), differential thermal analyzer(DTA), and electron probe micro-analyzer (EPMA). The results show that the phases of the two kinds of coatings(with and without RE) both include α-Fe, Fe7C3, Fe3C, Cr2B, Fe2B and FeB. The microstructure of F314 coating is mainly hypereutectic, the pro-phases Cr7C3 and Cr2B are loose, crassi, spiculate and contain microcracks. The brittleness of the coating is high, and the average hardness is 787 HV. When 0.8wt% RE was added into the F314 alloy, the microstructure varied from hypoeutectic to hypereutectic continuously, The hardness appears as gradient distribution with the highest value of 773 HV, meanwhile, the brittleness decreases significantly. The formation of gradient structure depends on the fallowing factors: (i) the conversion of RE. The addition of RE lowers the elements point and Fe-C eutectic temperature, thus the base metal melting acutely. (ii) the heating of plasma arc. Graded temperature results in directional solidification, thus the gradient structure forms easily. The main reasons for the hardness decrease with RE addition in the alloy are the ratio of hard phase lowering and the hardness of the hard phase decreasing.

Examination of Plasma Nitriding Microstructure with Addition of Rare Earths

Medium-carbon alloy steel was plasma nitrided with rare earths La, Ce and Nd into the nitriding chamber respectively. The nitriding layer microstructures with and without rare earths were compared using optical microscope,normal SEM and high resolution SEM, as well as TEM. It was found that the extent of the influence on plasma nitriding varies with different contents of rare earth. The effect of plasma nitriding is benefit from adding of Ce or Nd. The formation of hard and brittle phase Fe_(2-3)N can be prevented and the butterfly-like structure can be improved by adding Ce or Nd. However, pure La may prevent the diffusion of nitrogen and the formation of iron nitride, and reduce the depth of diffusion layer.

Analysis of Valence Electron Structure in Compound Layer of Steel 42CrMo Plasma Nitrided with Rare Earth Addition

The valence electron structure (VES) in compound layer of steel plasma-nitrided at 560°C with rare earth (RE) addition was calculated based on the empirical electron theory (EET) of solids and molecules and BLD method. The results show that the presence of RE atoms diffused into surface layer leads to an increase of phase structure factor, which explains the catalyzing and micro-alloying effects of RE.

Effect of rare earths on mechanical properties of plasma nitrocarburized surface layer of 17-4PH steel

The aim of this investigation is to reveal the influence of rare earths(RE) addition on mechanical properties of plasma nitrocarburized 17-4PH steel.The nitrocarburized layers were characterized by optical microscope,scanning electron microscope equipped with energy dispersive X-ray analyzer,X-ray diffractometer,microhardness tester and pin-on-disc tribometer.The results showed that RE atoms could diffuse into the surface layer of 17-4PH steel plasma nitrocarburized at 500 °C for 4 h and did not change the ...

CRYSTAL DEFECTS IN PLASMA NITRIDED LAYER CATALYZED BY RARE EARTH

The microstructure of plasma nitrided layer catalyzed by rare-earth elementshas been studied with TEM. The results show that the grains of gamma ft-Fe_4N phase are refined byrare-earth elements and the plane defects in boundary are increased by rare-earth elements. Theaddition of rare-earth element increases the bombardment effect and the number of crystal defectssuch as vacancies, dislocation loops, twins and stacking faults in gamma ft -Fe_4N phase and canproduce the high-density dislocations in the ferrite of diffusion layer at a distance 0.08mm fromthe surface. The production of a number of crystal defects is one of important reasons whyrare-earth element accelerates the diffusion of nitrogen atoms during plasma-nitriding.

Structure and properties of nanocrystalline rare earth bulks prepared by spark plasma sintering

A series of rare earth bulks with the ultrafine nanocrystalline structure were prepared by applying an 'oxygen-free'(an environmental oxygen concentration less than 0.5 ppm) in-situ synthesis system,where the inert-gas condensation was combined with the spark plasma sintering technology into an entirely closed system.The thermal and mechanical properties of the prepared ultrafine nanocrystalline bulks were characterized and compared with those of the raw polycrystalline bulks.It was found that the specific ...

Behaviour of Rare Earths in Solid Solution in Steel

The contents of rare earth metals(REM) in solid solution in 16 Mn steel were determined by means of inductive coupling plasma (ICP) spectroscopy.The amount of REM in solid solution is only a few ppm in the steel with MnS inclusions, which rises slightly with the increasing of REM content in steel.At RE/S>1.9,the MnS inclu- sions in steel disappear completely,the REM con- tent in solid solution increases rapidly with the in- creasing of REM content.The solubility of cerium in 16 Mn steel(st 52)is less than 0.011 wt—％ at room temperature. The results obtained indicate that REM in sol- id solution reduce the amount of pearlite and in- crease that of ferrite and its microhardness.Dis- solved REM oculd increase temperature of critical points,alleviate band structnre and suppress growth of austenite grains.

Partial Oxidation of Methane with Sol-Gel Fe/Hf/YSZ Catalyst in Dielectric Barrier Discharge: Catalyst Activation by Plasma

A 1% Fe-30% Hf over yttria-stabilized zirconia catalyst in combination with novel plasma-assisted activation techniques for a direct partial oxidation of methane to methanol was tested using dielectric barrier discharge plasma at ambient temperature and atmospheric pressure. However, instead of methanol, the reaction products were dominated by HE, CO, CO2, C2, and H2O. A catalytically activated plasma process increased the production of methanol compared with a noncatalytic plasma process. The maximum selectivity of methanol production was achieved using a catalyst that was treated at higher applied power.

Plasma cell leukemia-one in a million: A case report

BACKGROUND Plasma cell leukemia(PCL) is diagnosed by the presence of an absolute plasma cell count of > 2 × 109/L or 20% plasma cells in the peripheral blood. Because the incidence of PCL is relatively low, our case report study presents a rare opportunity to describe the clinical and pathological characteristics of this leukemia, as well as different modalities of treatment and outcomes of primary PCL(pPCL).CASE SUMMARY A 56-year-old male with a history of hypertension complained of pain in the left flank area which started four months prior to admission. On admission, his vital signs were stable, and physical examination was completely benign. Laboratory evaluation showed hemoglobin of 5.1 g/dL, white blood cell count of 6.6 cells per cubic millimeter with 16% atypical lymphocytes, and platelet count of 51000 per microliter. Peripheral smear showed more than 10%-15% of plasma cells(Figure1), and flow cytometry of peripheral blood confirmed PCL with 24% plasma cells CD138+. Bone marrow biopsy demonstrated 80% plasma cells(38+, 138+, 117+,10-, 19-, 20-, 56-) with 90% cellularity. The Oncology team was consulted, and VCD therapy was started. After completing therapy at 1, 4, 8, and 11 d, the patient was discharged home. The patient was being considered for a bone marrow transplant evaluation within two months of discharge.CONCLUSION PCL is a rare and aggressive form of leukemia with a poor prognosis. Multicenter studies and clinical trials should be conducted to develop accurate criteria for the initial diagnosis and prompt treatment of this disease.

A Survey of 16 Rare Earth Elements in the Major Foods in China

Objective The aim of this survey was to investigate the level of contamination of the most consumed foods in China with 26 rare earth elements （REEs）, and to provide the basic data for establishing and revising food safety standards for REEs. Methods Sixteen REEs in foods were measured by inductively coupled plasma-mass spectrometry （ICP-MS） in the labs of the Centers for Disease Control and Prevention of four provinces and two municipalities, during 2009-2020. Results 2 231 samples were analyzed and 29 221 concentration data of 16 REEs were collected. The REEs levels in the investigated foods varied significantly. The concentrations of cerium （Ce）, dysprosium （Dy）, yttrium （Y）, lanthanum （La）, and neodymium （Nd） were relatively high, while the remaining eleven REEs were at low levels. The mean values of total rare earth element oxides （REOs） in cereals, fresh vegetables, fresh aquatic products, fresh meats and eggs varied from 0.052 mg/kg to 0.337 mg/kg. Conclusion 16 REEs in the major foods were at very low contamination levels in the investigated regions.

Structure and Magnetic Properties of Sm_2Fe_(17)N_x Sintering Magnets Prepared by Spark Plasma Sintering

Bulk Sm2Fe17Nx sintering magnet was fabricated by spark plasma sintering(SPS) technique. The effects of sintering pressure and sintering temperature on the magnetic properties of the Sm2Fe17Nx magnet were investigated. As a result, the density of the magnet is obviously improved with the increase of sintering pressure, but the coercivity drops since Sm2Fe17Nx has decomposed into SmN,α-Fe and N2. When sintering temperature was only above 200℃under 1 GPa sintering pressure, the coercivity even begins to decrease, which indicates that high pressure promotes the decomposition of the Sm2Fe17Nx at lower temperature. The decomposition is also proved by the decrease of nitrogen and increase ofα-Fe in the magnets.

Plasma Nitriding of 722M24 Steel with Pure Lanthanum, Cerium and Neodymium as Sputter Sources

A series of experiments were carried out to investigate the influence of pure rare earth addition on the plasma nitriding response of low alloy steel. For this purpose, pure rare earth metals (La, Ce and Nd) were put into the plasma nitriding furnace as sputter sources during nitriding of 722M24 steel. a variety of experimental and analytical techniques were employed to evaluate the structures and hardening response of the nitrided lavers which included metallography for structural examination, glow discharge spectrometry and secondary ion mass spectrometry for chemical composition profile analysis, X-ray diffraction for phase identification and microhardness testing for hardness profile measurements. The results show that the incorporation of rare earth metals in the glow discharge. during plasma nitriding not only influences the discharge characteristics but also results in the deposition of rare earth atoms and their compounds onto the specimen surface. These significantly affect the response of the investigated steel to plasma nitriding. The extent of the influence on plasma nitriding varies with different rare earth metals.

Effects of Additive CeO_2 on Thermal Shock Resistance of Plasma-Sprayed Cr_2O_3 Coating

The influence of CeO2 with different content on the thermal shock resistance of plasmasprayed Cr2O3 coating was investigated. The thermal shock failure mechanism of coating was also studied. It is found that the thermal shock failure mechanism of coating is thermal stress fatigue destruction, and the destruction takes place at interface of ceramic and bond coating. The experimental results show that the lifetime of coating fracture and failure increase considerably when 3% CeO2 is added into the plasma-sprayed Cr2O3 coating. The suitable content of CeO2 makes the microcracks exist in network form. The microcrack net can release internal stress in coating, delay the crack forming and expanding and decrease holes in coating. Thus the thermal shock resistance increase largely.

Effects of Lanthanum Ion and Its Complexes on Permeability of Pollen Plasmalemma and Pollen Germination

Effects of La 3+ and its complexes on permeability of pollen plasmalemma and pollen germination were studied. La(NO 3) 3 in the range of 1×10 -7 ～1×10 -4 mol·L -1 obviously inhibits the permeability of pollen plasmalemma, while La 3+ EDTA complex has no effect on the permeability. The effects of La 3+ citrate and La 3+ tartrate complexes on permeability of pollen plasmalemma are related to the ratio of ligand to La 3+ . When the ratio is less than 3∶1, the complexes reduce the permeability of pollen plasmalemma, while the ratio reaches 10∶1, and the complexes have not any effect. La 3+ in the range of 2 5～20 μmol·L -1 promotes pollen germination, but the pollen germination is inhibited as the concentration is above 80 μmol·L -1 . The above results indicate that La 3+ and some complex species are beneficial to the reduction of permeability of pollen plasmalemma and the promotion of pollen germination when the concentration is in the range of 1×10 -6 ～1×10 -5 mol·L -1 .

Effect of Yttrium Pre-Implantation on Implantation Behavior of Ti-6Al-4V Alloy in Nitrogen Plasma Immersion Ion Implantation

In order to increase the peak depth of nitrogen atoms during the nitrogen plasma immersion ion implantation of Ti-6Al-4V alloy, the rare earth metal yttrium was applied. In the experiment, yttrium and nitrogen ions were implanted under the voltage of 20 and 30 kV, respectively. In the samples with yttrium pre-implantation for 30 min, the Anger electron spectroscopy (AES) analysis shows that the peak depth of the nitrogen atoms increases from 50 up to 100 nm. It can also be seen from the tribological tests that the wear resistance of these samples is increased remarkably.

Microstructure and magnetic properties of bulk magnets Nd_(14-x)Fe_(76+x)Co_3Zr_1B_6(x=0,0.5,1) prepared by spark plasma sintering

Melt-spun ribbons with nominal composition of Nd14–xFe76+xCo3Zr1B6(x=0,0.5,1) were consolidated into isotropic bulk magnets by spark plasma sintering method.It was found that the Nd content and sintering temperature had significant influence on the density and magnetic properties of the sintered magnets.Homogeneous microstructure and fine grain(50–100 nm) were obtained when sintering below 700 ℃,and the initial magnetization curve showed that the coercivity was controlled by the pinning mechanism.However,ab...

Effect of RE on Cracking Resistance and Microstructure of Coatings Formed by Plasma Jet Surface Metallurgy

Metallurgical coatings of iron-based alloy with RE oxide were prepared on low-carbon steel using a home-made DC-plasma jet surface metallurgy equipment. Scanning electron microscope (SEM), energy dispersive X-ray (EDX) microanalysis and X-ray diffraction analysis (XRD) were employed to observe the microstructure and analyze the chemical compositions of coatings. And the cracking susceptibility of coatings was studied in terms of RE addition. Experimental results show that addition of RE oxide (La_2O_3 and CeO_2) can refine and purify the microstructure, and can reduce the cracking susceptibility of coatings.

Preparation and Properties of Lanthanum Trivalent Ion Doped TiO_2 Nanopowders by Liquid Plasma Spray

The lanthanum trivalent ion doped TiO2 nanopowders were prepared by liquid plasma spray with solution of titanium tetra-tert-butoxide and alcohol as feedstock and La(NO3)3·6H2O as doping component. The photocatalytic activity of samples at different doping concentrations in photocatalytic degradation of methyl orange was discussed. The powders were characterized by Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD), and the effect of doped ion on the pattern, phase composition and crystallite sizes were analyzed. The results indicated that lanthanum trivalent ion doped TiO2 nanopowders could be prepared by liquid plasma spray. Lanthanum trivalent ion doping increased the photocatalytic activity of TiO2 greatly, the optimal doping concentration was 0.5%. The doped powders were the mixture of anatase phase and rutile phase. The contents of anatase phase decreased firstly and then increased with an increase in the contents of lanthanum trivalent ion. Doping lanthanum trivalent ion could make the TiO2 nanopowders uniform and reduced its particle size.

1∶7 Type Nanocrystalline SmCo_6Fe Sintered Magnet Prepared by Spark Plasma Sintering

Bulk nanocrystalline SmCo6Fe sintered magnet was prepared by Spark Plasma Sintering technique (SPS). XRD patterns show that the magnet exhibits a stable TbCu7 structure. TEM observation indicates that the microstructure of the magnet is composed of SmCo6Fe single phase grains with an average grain size of 30 nm. Magnetic measurement shows that under 9 T magnetic field, the coercivity of the magnet reaches 1.12 T; the saturation magnetization and the remanence are 1.13 and 0.67 T, respectively. The magnet has a (BH)max of 75.6 kJ·cm-3.

Synthesis, Composition Optimization, and VUV Photoluminescence Characterization of (Y,Gd)(V,P)O_4∶Eu^(3+) as A Potential Red-Emitting Plasma-Display Panel Phosphor

The synthesis, composition optimization, VUV Photoluminescence (PL) spectra, and optical properties, of (Y,Gd)(V,P)O4∶Eu3+ phosphors were investigated by synchrotron radiation. The VUV PLE spectra and the correlation among VUV PL intensity, λem, and Eu3+, Gd3+, and P-content were established. The PLE spectral studies showed that (Y,Gd)(V,P)O4∶Eu3+ exhibited significant absorption in the VUV range. The VUV PL intensity was found to enhance with PO43- and Gd3+-doping. Furthermore, the chromaticity characteristics of (Y,Gd)(V,P)O4∶Eu3+ were also found to be (0.6614, 0.3286) and compared against (Y, Gd)BO3∶Eu3+ as a reference. Based on the characterization results, we are currently improving and evaluating the potential application of (Y,Gd)(V,P)O4∶Eu3+ as a new red-emitting PDP phosphor.