Microstructure characteristics of coating with amorphous phases prepared from Fe-based alloy powders by plasma spray

In this paper, alloy powders mixed with a molar ratio of Fe ： P ： C of 80 ： 13 ： 7 were sprayed on Q235 steel by plasma spray method to prepare coating with amorphous phases. The phase composition of the mixed alloy powders and prepared coating were characterized by X-ray diffraction （ XRD ）. The morphology and the composition cf the coating were analyzed by scanning eleetron microscopy （SEM） nnd energy dispersive apectroscopy （ EDS ）. In addition, the thermal stability ef the coating with amorphous phases was characterized by differential thermal analyzer （ DTA ）. Tile results showed that, usirtg mixed alloy powders with a molar ratio of Fe： P： C of 80：13：7, the coating containing certain amount of amorphous alloys was suceessathlly prepared through atmospheric plasma spray technique. In the coating, the main phases were determined to be Fe, FeP aad Fe2P. The crystallization of the coating started from about 461°. Tile coating was mechanically adhered to the substrate.

Amorphous phase formation rules in high-entropy alloys

There have been many interesting studies on high-entropy alloys（HEAs）, also known as multi-component（MC） alloys（MCAs）, in recent years. MC metallic-glasses（MGs） have shown the potential to express the advantages of MCAs and MGs in tandem. Amorphous phase formation rules are a crucial issue in the HEA and MCA field. For equal or near-equal atomic ratio alloys, mixed-entropy among the elements has a significant effect on the phase formation. This paper focuses on HEA amorphous phase formation rules. In the first two sections, the recent progress in amorphous phase formation in HEAs and MCAs is reviewed, including the effective factors and correlative parameters related to amorphous phase formation. In the third section, novel MCMGs including high-entropy（HE） bulk-metallic-glass（HE-BMG） and MCMG films developed in recent decades are summarized, and the giant-magnetic-impedance（GMI） effect of MC amorphous fibers is discussed.

Wear and corrosion properties of laser cladded Cu_(47)Ti_(34)Zr_(11)Ni_8/SiC amorphous composite coatings on AZ91D magnesium alloy

To improve the wear and corrosion properties of AZ91D magnesium alloys,Cu-based amorphous composite coatings were fabricated on AZ91D magnesium alloy by laser cladding using mixed powders of Cu47Ti34Zr11Ni8 and SiC.The wear and corrosion behaviours of the coatings were investigated.The wear resistance of the coatings was evaluated under dry sliding wear condition at room temperature.The corrosion resistance of the coatings was tested in 3.5%(mass fraction) NaCl solution.The coatings exhibit excellent wear resistance due to the recombined action of amorphous phase and different intermetallic compounds.The main wear mechanisms of the coatings and the AZ91D sample are different.The former is abrasive wear and the latter is adhesive wear.The coatings compared with AZ91D magnesium alloy also exhibit good corrosion resistance because of the presence of the amorphous phase in the coatings.

Molybdenum based amorphous and nanocrystalline coatings prepared by high velocity oxy-fuel spraying

The high velocity oxy-fuel(HVOF) based thermal spray process has developed as a potential advantageous approach for fabricating various kinds of functional coatings.In this article,the coatings of Mo-based alloy were synthesized using the HVOF process.The microstructure and the mechanical properties of the HVOF-processed coatings were investigated using SEM,TEM,XRD,and hardness and wear tests.Annealing treatment was applied to the as-sprayed coatings to develop the microstructure and its effect on the microstructure and mechanical properties of the coatings was examined.It is found that the HVOF-processed Mo-based alloy coatings are comprised of an amorphous splat matrix embedded with nano-sized crystalline particles.Annealing at temperatures over 950 ℃ results into crystallization of the amorphous matrix.The mechanical properties of the as-sprayed coatings are enhanced with annealing temperature up to 750 ℃ and from 950 to 1050 ℃,keeps constant between 750 and 950 ℃,and reduce over 1050 ℃.The change of the mechanical property with the microstructure was illustrated in the study.

Amorphous Formation in an Undercooled Binary Ni-Si Alloy under Slow Cooling Rate

High undercooling up to 392 K was achieved in eutectic Ni70.2Si29.8 alloy melt by using glass fluxing combined with cyclic superheating. A small quantity of amorphous phase was obtained in bulk eutectic Ni70.2Si29.8 alloy when undercooling exceeds 240 K under slow cooling conditions （about 1 K/s）. The amorphous phase was confirmed by high-resolution transmission electron microscopy and differential scanning calorimetry.

Curie Temperature of the Intergranular Amorphous Phase in Nanocrystalline Fe_(89)Zr_7B_4 Alloy

The FeZrB amorphous alloys for simulating the intergranular amorphous phase in the nanocrystalline Fe 89 Zr 7B 4 soft magnetic materials were obtained by mechanical alloying of a mixture of elemental Fe, Zr and B powders for 25 h. It is shown that the Curie temperature of the simulated intergranular phase alloy is much lower than that of the intergranular phase with the same chemical composition in the nanocrystalline Fe 89 Zr 7B 4 alloy. The possible mechanism is mainly due to the strong ferromagnetic exchange force among the nanocrystalline α Fe grains.

Volcanic emissions and atmospheric pollution:A study of nanoparticles

The influence of emissions of an active volcano on the composition of nanoparticles and ultrafine road dust was identified in an urban area of the Andes.Although many cities are close to active volcanoes,few studies have evaluated their influence in road dust composition.Air quality in urban areas is significantly affected by nonexhaust emissions(e.g.road dust,brake wear,tire wear),however,natural sources such as volcanoes also impact the chemical composition of the particles.In this study,elements from volcanic emissions such as Si>Al>Fe>Ca>K>Mg,and Si-Al with K were identified as complex hydrates.Similarly,As,Hg,Cd,Pb,As,H,Cd,Pb,V,and salammoniac were observed in nanoparticles and ultrafine material.Mineral composition was detected in the order of quartz>mullite>calcite>kaolinite>illite>goethite>magnetite>zircon>monazite,in addition to salammoniac,a tracer of volcanic sources.The foregoing analysis reflects the importance of carrying out more studies relating the influence of volcanic emissions in road dust in order to protect human health.The road dust load(RD_(10))ranged between 0.8 and 26.8 mg m^(−2)in the city.

Structure characteristic and its evolution of Cu-W films prepared by dual-target magnetron sputtering deposition

Immiscible Cu-W alloy thin films were prepared using dual-target magnetron sputtering deposition process. The structure evolution of Cu-W thin films during preparation was investigated by X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy. In the initial stage of dual-target magnetron sputtering deposition process, an amorphous phase formed; then it crystallized and the analogy spinodal structure formed due to the bombardment of the sputtered particles during sputtering deposition process, the surface structure of the film without the bombardment of the sputtered particles was the amorphous one, the distribution of the crystalline and amorphous phase showed layer structure. The solid solubility with the analogy spinodal structure was calculated using the Vegard law. For Cu-13.7%W （mole fraction） film, its structure was composed of Cu-ll%W solution, Cu-37%W solution and pure Cu; for Cu 14.3%W film, it was composed of Cu-15%W solution, Cu-38%W solution, and pure Cu; for Cu-18.1%W film, it was composed of Cu-19%W solution, Cu-36% W solution and pure Cu.

Visible-Light Excitated Photocatalytic Activity of Rare Earth Metal-Ion-Doped Titania

The rare earth ion Ce 4+ doped TiO 2 was prepared by sol-gel method. The average particle sizes are about 10 nm for sol phase and 55 nm for polycrystalline phase. The photocatalytic activities to degrade Reactive Brilliant Red Dye X-3B were investigated. The result reveals that the spectrum response of Ce 4+-TiO 2 has extended to visible region from the UV region(λ<387 nm) of pure TiO 2. Amorphous phase Ce 4+-TiO 2 sol with an electron scavenger (1.0% atom fraction Ce 4+ ion doping amount) shows the capability of the photocatalytic degradation of the dye X-3B as well as the nanocrystallite Ce 4+-TiO 2 with an interband trap site. Despite of the difference in the morphology of Ce 4+-TiO 2 photocatalyst, there is no apparent difference in respect of the decoloring effects. Whereas, polycrystalline phase Ce 4+-TiO 2 exhibits strong photomineralization power in comparison with the amorphous phase. The photocatalytic oxidation mechanisms of the dye molecule mainly involved in the self-photo-sensitization photolysis process by the first excited singlet oxygen ( 1O 2) and photocatalysis process by hydroxyl radicals(·OH) under visible light irradiation.

Magnetic properties of Nd_2Fe_(14)B/α-Fe nanocomposite magnets with yttrium addition

The phase evolution and magnetic properties of Nd9？xYxFe72Ti2Zr2B15 （x = 0,0.5,1,and 2） melt-spun nanocomposite ribbons were studied.It is found that Y addition not only enhances the formability of amorphous phase in the alloy,but also stabilizes the amorphous phase during the annealing treatment.The appropriate content of Y addition effectively enhances the remanence （Jr） of the annealed sample.The residual amorphous intergranular phase in the annealed sample optimizes the squareness of the loop,resulting in an larger maximum energy product （BH）max.The best magnetic properties,Jr = 0.78 T,Hci （coercivity） = 923.4 kA/m,and （BH）max = 98.5 kJ/m3,were obtained from the Nd8YFe72Ti2Zr2B15 ribbon spun at Vs = 4 m/s and annealed at 700°C for 10 min,which is composed of Nd2Fe14B,α-Fe,and amorphous phase.

Impact wear behaviors of Hadfield manganese steel

Impact wear behaviors of Hadfield manganese steel at different impact angles were investigated. The results of impact wear tests show that there exists a critical impact load for Hadfield steel. The wear rate suddenly turns down after some impact cycles when the impact load is greater than the critical load. The critical impact load is smaller than 8.2 J in this research because the nano-sized austenitic grains embedded in amorphous delay the crack propagation in subsurface. From high resolution transmission electron microscope (HRTEM) examination of subsurface microstructure, it is found that a large amount of nano-sized grains embedded in bulk amorphous matrix are fully developed and no martensitic transformation occurs during the impact wear process. The analytical results of worn surface morphology and debris indicate that the initiation of crack, propagation and spalling are restricted in the amorphous phase, resulting in the size distribution of debris in nano-sizes, which is the reason why the wear rate of Hadfield steel is greatly decreased at high impact load.

Fabrication and microstructure of nanostructured Mg-3Ni-2MnO_(2) by ball milling in hydrogen atmosphere

Nanostructured Mg-3Ni-2MnO_(2) was synthesized by ball milling elemental powders of Mg,Ni and MnO_(2) in hydrogen atmosphere.The microstructures of the powder prepared at different milling time were analyzed by X-ray diffractometry(XRD), scanning electron microscopy(SEM)and high resolution electron microscopy(HREM).The milling time is the most key parameter impacting on the grain size and the microstructure of material.With prolonging the milling time,particle size becomes smaller and smaller.But after the ball milling time reaches about 20 h,reduction of grain size becomes slowly.When the milling time is more than 50 h,nanocrystalline fully forms.When the milling time is more than 80 h,there are more amorphous phases in materials.The average particle diameter of material is about 1μm and the grain size is 10-30 nm.

NANOCRYSTALLINE STRUCTURE AND INITIAL PERMEABILITY OF ANNEALED Fe_(73.5)Cu_(1)W_(3)Si_(13.5)B_(9) Alloy

The nanocrystalline structure of annealed Fe73.5 Cu1 W3Si13.5B9 alloy has been investigated by using the XRD and the TEM methods. The relation between the initial permeability and the microstructure of the annealed alloy has been discussed. The crystalline phase in annealed Fe73.5 Cu1 W3Si13.5B9 alloy is the α-Fe(Si) phase with DO3 superstructure. The volume fraction, Si content and degree of order of the αFe(Si) phase increase with increasing annealing temperature. In the temperature range of 490-570℃, the α-Fe(Si) phase has a size of 13 nm, and its grain number increases as the annealing temperature is increased. The DO3 ordered region in the α-Fe(Si) grain is spherical approximately, and its size increases as the annealing temperature increases. The size of the DO3 ordered region is 12.8 nm at the temperature of 570℃,which is close to that of the α-Fe(Si) grain. There is obvious change in the structure of the residual amorphous phase during annealing, and the nearest atomic distance and the short-range order of residual amorphous phase reach maximum and minimum at 530℃, respectively. The initial permeability of annealed Fe73.5 Cu1 W3Si13.5 B9 alloy is not only dependent on the size, volume fraction and Si content of the α-Fe(Si) phase but also related to the structure state of the residual amorphous phase.

Study of the Curing Temperature of 600°C, 700°C and 800°C of Mouyondzi Clay on the Mechanical, Physical and Microstructural Properties of Geopolymer Obtained

This work consists of determining the right curing temperature for Mouyondzi clay, with a view to obtaining a very reactive metakaolinic amorphous phase, which will give us a geopolymer with good physical and mechanical performance. The kaolin-dominant Mouyondzi clay was calcined at 600℃, 700℃ and 800℃ with a heating rate of one degree per minute. In order to achieve the objective of this work, the performance of geopolymer was measured by compressive strength on geopolymer prisms of 28 days of age, by XRD and IRFT of geopolymer powders, calcined clay and raw clay, and by SEM of geopolymer blocks. Analysis of the results shows that the resistance value increases with the curing temperature of the clay and reaches a maximum of 49 MPa at 800℃. At 600℃ we already have 31 MPa, the equivalent of Portland cement with the addition. The XRD confirms the disappearance of clay species from 600℃. At 800℃ there is not yet the appearance of a new crystalline phase. Quartz is the only mineral species present. We can therefore confirm that at 800℃, the geopolymer obtained exhibits higher physical and mechanical performance than the other curing temperatures studied for Mouyondzi clay. This is confirmed by the appearance of a new aluminosilicate phase in the IRFT spectra and in the SEM images appearing as a continuous plate.

Behaviors of Zn2GeO4 under high pressure and high temperature

The structural stability of Zn2GeO4 was investigated by in-situ synchrotron radiation angle dispersive x-ray diffraction. The pressure-induced amorphization is observed up to 10 GPa at room temperature. The high-pressure and hightemperature sintering experiments and the Raman spectrum measurement firstly were performed to suggest that the amorphization is caused by insufficient thermal energy and tilting Zn–O–Ge and Ge–O–Ge bond angles with increasing pressure,respectively. The calculated bulk modulus of Zn2GeO4 is 117.8 GPa from the pressure-volume data. In general, insights into the mechanical behavior and structure evolution of Zn2GeO4 will shed light on the micro-mechanism of the materials variation under high pressure and high temperature.

Amorphous molybdenum sulfide mediated EDTA with multiple active sites to boost heavy metal ions removal

The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated via a facile hydrothermal method mediated by EDTA,which was applied to heavy metal ions(Cu^(2+),Cd^(2+),Pb^(2+),Zn^(2+)and Ni^(2+))removal from aqueous solutions.A case study for Cu^(2+)ions showed that the adsorption capacity of EDTA-MoSx(x=2,3)was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L.Adsorption mechanisms of different sulfide groups and—COOH of EDTA-MoSx(x=2,3)were verified systematically via a series of experiments,characterizations,and density functional theory(DFT)calculations.Both bridging S_(2)^(2-)and—COOH covalently bonded with Cu^(2+)ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx(x=2,3).This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.

Formation of non-equilibrium phases and associated structural transition in the Pd-Ta system induced by ion beam mixing

For the Pd-Ta system characterized by a negative heat of formation of -78 kJ/mol, 200 keV xenon ion beam mixing with nano-sized Pd-Ta multilayered films was conducted to study the non-equilibrium phase formation. The results showed that uniform amorphous alloys can be formed within a composition range of 25 at%-78 at% Ta, which falls in the maximum possible amorphization range of 22 at%-80 at% Ta predicted by the empirical model. Moreover, two metastable crystalline phases both of FCC structure, yet with different lattice constants were obtained. Interestingly, a self-assembled fractal pattern was observed in the Pd52Ta48 multilayered films after irradiation to a dose of 1×1015 Xe+/cm2 and its dimension was determined to be 1.75±0.05. The possible mechanisms for the formation of amorphous and metastable crystalline phases as well as for the growth of the fractal pattern were discussed.

Effect of Cu content on microstructure and mechanical properties of in-situ β phases reinforced Ti/Zr-based bulk metallic glass matrix composite by selective laser melting(SLM)

In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu content on phase formation,microstructure,and mechanical properties is investigated.The average volume fraction and width of theβphase decreases with increasing Cu content,while a more amorphous phase and the(Ti,Zr)_(2)Cu phase forms.In the center zone of the molten pool,theβphase grows in the direction of the temperature gradient,and the amorphous phase distributes among theβphases.This occurs using:sphere morphology(for x=5),a more continuous elongated sphere and network morphology(for x=10),and network morphology(for x=15),respectively.In the edge zone of the molten pool,due to the smaller cooling rate and the existence of a partially molten zone,theβphase becomes coarser,and an amorphous phase forms for more continuous networks.Furthermore,the hardness improves significantly with increasing Cu content.No crack is found for x=5.Although the average volume fraction of theβphase for x=5 is about 90%,the compression yield strength is 1386±64 MPa,reaching to an average level of conventionally fabricated counterparts,due to finer microstructure,and twinning and martensitic transformation of theβphase.

Shear transformation zone dependence of creep behaviors of amorphous phase in a CuZr-based bulk metallic glass composite

The creep behaviors of the amorphous phase in a CuZr-based bulk metallic glass composite(BMGC)are studied by nanoindentation.Samples fabricated via higher cooling rates are found to exhibit more prominent creep,but a smaller shear viscosity.The volume of the shear transformation zones(STZs)in the amorphous phase calculated based on a cooperative shear model increases with the cooling rate.The evolution of excess free volume created during creep deformation is clarified.A looser atomic arrangement leads to a larger STZ volume,thus facilitating creep deformation.This study gives a better understanding of the deformation behaviors of the amorphous phase in BMGCs.

Amorphous Structure and Bonding Chemistry of Aluminium Antimonide（AISb） Alloy for Phase-change Memory Device

With the help of first-principles molecular dynamics calculations, we obtained the atomic picture of amorphous A1Sb（a-A1Sb） for phase-change memory application. Generally, a-A1Sb shows sp3 bonding network, which is the intrinsic characteristic for its good thermal stability. Significant wrong（homogenous） AI-AI bonds can also be observed from the pair correlation function. This hints the amorphous phase may consist of A1 cluster and Sb-rich A1-Sb alloy. Recent experiment has observed the Sb-rich region of AISb alloy can be switched to crystal, on the basis of which, combined with our calculations, we thus propose that on the one hand such a Sb-rich region in a-A1Sb can retain the rapid crystallization like pure Sb solid and on the other hand some AI atoms play the important role of stabilizing Sb rich network with sp3 bonding. The present study offers a microscopic view to understand the phase change mechanism of AlSb alloy for information storage device.