The Effect of Cu Content on the Microstructure and Properties of the Wire Arc Additive Manufacturing Al-Cu Alloy.

Al-Cu alloy has broad application prospects in the field of aerospace due to its excellent performance. In this paper, deposits with different Cu contents were prepared by the wire arc additive manufacturing (WAAM) process, and the effects of Cu content on the microstructure and mechanical properties were investigated. The microstructure of Al-Cu alloy was investigated by metallography, scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), and transmission electron microscope (TEM). The results show that both the number and size of the precipitated θ phases (Al2Cu) in the as-deposited material increase with the increase of Cu content. After the T4 treatment, the solid solution amount of Cu in the matrix showed a trend of first increasing and then remaining stable. When the content of Cu was greater than 5.65%, as the Cu content increased, the number and size of the remaining θ phases both increased. In the peak ageing state, the amount of precipitated θ' phase showed a trend of increasing and then remaining stable. After the T6 treatment, the mechanical properties showed a trend of first increasing and then decreasing with the increase of the content of Cu. When the Cu content was 5.65%, the deposit achieved the best mechanical properties, and the anisotropy of the mechanical properties disappeared. The tensile strength, yield strength, and elongation reached 538 MPa, 478 MPa, and 10.5%, respectively. When the content of Cu was greater than 5.65%, the anisotropy of mechanical properties was obvious, and the fracture mode of the vertical specimen changed from ductile fracture to brittle fracture.

Adsorption of Congo red by fibrous xonotlite prepared from waste silicon residue.

Fibrous xonotlite was synthesized under the conditions of Na2SiO3 concentration of 0.05 mol·L-1, molar ratio of Si/Ca of 1:1, temperature of 220 °C and time of 9 h. It is worth pointing out that the Na2SiO3 solution as raw material was obtained from silicon residue through several procedures. The fibrous xonotlite exhibits excellent adsorption capacity for Congo red. 50 mL solution of Congo red with the concentrations of 100, 150 and 200 mg·L-1 can be almost completely adsorbed by 30 mg of fibrous xonotlite within 10 min, and the adsorption ratios are 94.05%, 95.50% and 94.14%. The Langmuir model describes the adsorption well, indicating the adsorption is monolayer. The adsorption kinetics follows the pseudo-second-order model. The calculated maximum adsorption capacity of fibrous xonotlite for Congo red is 574.71 mg·g-1 at room temperature. Fibrous xonotlite is a potential efficient adsorbent for Congo red owing to its rapid adsorption, high adsorption capacity and regeneration capacity.

Microstructure and Properties of Al-6.0Mg-0.3Sc Alloy Deposited by Double-Wire Arc Additive Manufacturing.

Al-6.0Mg-0.3Sc alloy deposits are prepared by means of a double-wire arc additive manufacturing process. The formation, porosity, metallographic structure, type of precipitated phase, and mechanical properties of the deposit are studied. Double-wire arc forming affords precision advantages over single-wire-arc forming, which is evidenced by the increased surface uniformity of the deposit. Compared with the deposit of single-wire-arc formed, the deposit of double-wire arc formed exhibits only fewer and smaller pores, and the lower process heat yields rapid solidification and tiny precipitate sizes. A larger amount of Mg and Mn is observed to be dissolved in the Al matrix of double-wire arc-formed deposit, which increases the alloy strength, and smaller primary Al3Sc phase, which exhibits excellent grain refinement. Furthermore, the presence of a high amount of Sc solid solution in the matrix of double-wire arc-formed deposit strengthens the alloy, and the melting of the rear wire "heat-treats" the substrate formed by the front wire, promotes secondary Al3Sc phase precipitation, and further strengthens the alloy. Compared with the deposit of single-wire-arc formed, the mechanical properties of double-wire arc-formed deposit show an improvement: the tensile strength, yield strength, and elongation of the horizontally oriented specimens are estimated as 363 MPa, 258 MPa, and 26%, respectively. This successful implementation of the cold metal transfer + pulse process to prepare Al-Mg alloy parts can pave the way to their industrial production. The proposed method can find wide utility in the fields of aviation, aerospace, military, and shipbuilding.

Preparation of spherical flower-like Mg(OH)2 from waste magnesite and its immobilization performance for Cu2+, Zn2+ and Pb2.

Spherical flower-like Mg(OH)2 was successfully synthesized under conditions of Mg2+ concentration of 2 mol·L-1, molar ratio of Mg2+/NH4OH of 1:0.5, temperature of 120 °C and time of 1 h using MgSO4 solution as raw material obtained from waste magnesite through several procedures. Spherical Mg(OH)2 exhibits flower-like structure composed of lamellar crystals. The immobilization ability of spherical flower-like Mg(OH)2 for Cu2+, Zn2+ and Pb2+ obtained at variable dosage and ion concentrations shows it displays an excellent immobilization performance for Cu2+, Zn2+ and Pb2+. 50 mL solution with ion concentrations of 200 mg·L-1 could be almost completely immobilized by 200, 250 and 60 mg Mg(OH)2 within 6 min, and the immobilization efficiencies were 97.55%, 99.99% and 91.56%, respectively. Langmuir model well describes the immobilization process, involving chemisorption emphasized as monolayer.

Effect of Sn Content on the Microstructure and Properties of Wire and Arc Additive Manufactured Al-Cu Alloy Deposits.

Al-Cu-Sn alloy deposits with different Sn contents were prepared by the wire and arc additive manufacturing process. The microstructure and mechanical properties of the deposits were examined by metallography, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and tensile tests. The results indicated that the addition of Sn significantly refined the microstructure of the deposits in their as-deposited state, and the grains were transformed from dendrites to equiaxed crystals with a uniform grain size of ∼30 µm. For the deposits with Sn ≥0.15%, the continuous and elongated θ phase on the grain boundary became block-shaped, and the size of the precipitated phase increased. After T6 heat treatment, the θ phase completely dissolved in the substrate in the deposits with Sn ≤0.1%, whereas the θ-phase solid dissolution was incomplete in the deposits with Sn ≥0.15%; the higher the Sn content, the greater the amount of θ phase remaining. After the T6 treatment, the deposits with an Sn content of 0.25% exhibited cracks distributed along the grain boundaries. The addition of Sn significantly increased the density of the θ' phase, which was diffused and uniform in size; with an increase in the Sn content, the distribution density of the θ' phase in the deposits first increased and then decreased as the peak-aging condition was reached. The addition of Sn could effectively improve the mechanical properties of the deposits, which first increased and then decreased with an increase in the Sn content. The mechanical properties of the deposits were optimal at an Sn content of 0.1%, with a tensile strength of 493 MPa, yield strength of 434 MPa, and elongation of 9.5%.

Study on Microstructural and Mechanical Properties of an Al-Cu-Sn Alloy Wall Deposited by Double-Wire Arc Additive Manufacturing Process.

In this present study, single-wire and double-wire Al-Cu-Sn alloy walls were fabricated by an arc additive manufacturing process. The surface morphology, elemental composition, and microstructure were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) techniques. The mechanical properties of both the single-wire and double-wire walls were studied by mechanical property testing. The results showed that the heat input of the double-wire wall was lower than that of the single-wire wall at the same wire feeding speed. The surface microstructure of the double-wire wall showed a more uniform surface than the single-wire wall. The grains of the double-wire wall were found to be isometric crystals in the as-deposited state. The θ phase of the double-wire wall was dispersed with a smaller grain size in the grain boundary. After T6 heat treatment, the θ phase of the double-wire wall was completely dissolved into the aluminum matrix, and a large amount of θ' enhanced phases were precipitated with a phase spacing of about 15 nm. The mechanical properties of the double-wire wall were shown to have significantly improved performance, which further increased to 490 MPa, 420 MPa, and 12%, respectively. The transverse and longitudinal mechanical properties of the double-wire wall were consistent, and the fracture mode of both was ductile fracture.

Effect of Mg Content on Microstructure and Properties of Al-Mg Alloy Produced by the Wire Arc Additive Manufacturing Method.

In this study, an Al-Mg alloy was fabricated by wire arc additive manufacture (WAAM), and the effect of Mg content on the microstructure and properties of Al-Mg alloy deposits was investigated. The effects on the deposition surface oxidation, geometry, burn out rate of Mg, pores, microstructure, mechanical properties and fracture mechanisms were investigated. The results show that, when the Mg content increased, the surface oxidation degree increased; a "wave"-shaped deposition layer occurred when the Mg content reached 8%. When the Mg content was more than 6%, the burning loss rate of the Mg element increased significantly. With the increase of Mg content, the number of pores first decreased and then increased, and the size first decreased and then increased. When the Mg content reached 7% or above, obvious crystallization hot cracks appeared in the deposit bodies. When the Mg content increased, the precipitated phase (FeMn)Al6 and ß(Mg2Al3) increased, and the grain size increased. When the Mg content was 6%, the comprehensive mechanical properties were best. The horizontal tensile strength, yield strength and elongation were 310 MPa, 225 MPa and 17%, respectively. The vertical tensile strength, yield strength and elongation were 300 MPa, 215 MPa and 15%, respectively. The fracture morphology was a ductile fracture.

Synthesis and photocatalytic degradation ability evaluation for rhodamine B of ZnO@SiO2 composite with flower-like structure.

ZnO@SiO2 composite with flower-like structure was successfully prepared with molar ratio of ZnO/SiO2 = 1:1 based on the optimized synthesizing parameters of spherical SiO2 and flower-like ZnO. SiO2 particles were coated on the flower-like ZnO to form a homogeneous film through the multidimensional polycondensation of Si(OH)4. The photocatalytic degradation ability of ZnO@SiO2 composite for rhodamine B (RhB) obtained at different ZnO/SiO2 molar ratio and the comparison to that of flower-like ZnO showed that ZnO@SiO2 composite with ZnO/SiO2 molar ratio of 1:1 displayed a relatively good photocatalytic degradation ability to degrade RhB, but it was weaker than that of flower-like ZnO. Twenty millilitres of RhB solution at a concentration of 15 mg·L-1 could be completely degraded by 300 mg flower-like ZnO powder within 3 h, while the degrading efficiency was only 82.5% by 300 mg ZnO@SiO2 composite. But ZnO@SiO2 composite showed a better photocatalytic activity than flower-like ZnO at a lower pH value of 4.5.

Direct Growth of MoO2 /Reduced Graphene Oxide Hollow Sphere Composites as Advanced Anode Materials for Potassium-Ion Batteries.

Hollow MoO2 /reduced graphene oxide (MoO2 /rGO) sub-microsphere composites have been fabricated through a simple hydrothermal approach followed by a heat treatment process. When employed as an anode material for potassium-ion batteries, the as-synthesized MoO2 /rGO composite can deliver an initial charge specific capacity of 367.2 mAh g-1 at 50 mA g-1 , and its reversible capacity is 218.9 mAh g-1 after 200 cycles. Even when cycled at 500 mA g-1 , a high charge specific capacity of 104.2 mAh g-1 is achieved after 500 cycles. The excellent cycling capability and rate performance may be ascribed to the synergistic effects of the reduced graphene oxide and the hollow MoO2 spheres, which can increase the electrical conductivity of the composite, as well as resisting the strain arising from the repeated discharge-charge processes. These results indicate that the MoO2 /rGO hollow sphere composites are promising negative electrode materials for potassium-ion batteries.

High-Surface-Area and Porous Co2P Nanosheets as Cost-Effective Cathode Catalysts for Li-O2 Batteries.

To enable lithium-oxygen batteries for practical applications, the design and efficient synthesis of nonprecious metal catalysts with high activity and stable structural properties are demanded. The objective is to accelerate the sluggish kinetics of both oxygen reduction reaction and oxygen evolution reaction by facilitating electronic/ionic transport and improving oxygen diffusion in a porous structure. In this study, high-surface-area and porous cobalt phosphide (Co2P) nanosheets are synthesized via an environmentally safe hydrothermal method, where red phosphorous is used as the phosphorous source. It was found that the as-prepared Co2P/acetylene black (AB) composite delivered enhanced electrochemical performances, such as high capacities of 2551 mA h g-1 (based on the total weight of Co2P and AB) or 5102 mA h g-1 (based on the weight of Co2P or AB) and a good cycle life of more than 1800 h (132 cycles) in lithium-oxygen battery. The rational design of the Co2P/AB porous oxygen electrode structure provides sufficient accessible reaction sites and a short diffusion path for electrolyte penetration and diffusion of O2.

A hybrid gel-solid-state polymer electrolyte for long-life lithium oxygen batteries.

A hybrid gel-solid-state polymer electrolyte has been used as the separator and an electrolyte for lithium oxygen batteries. It can not only avoid electrolyte evaporation but also protect the lithium metal anode during reactions over long-term cycling. Due to its high ionic conductivity and low activation energy, excellent cycling performance is demonstrated, in which the terminal voltage is higher than 2.2 V after 140 cycles at 0.4 mA cm(-2), with a capacity of 1000 mA h g(composite)(-1).

A Metal-Free, Free-Standing, Macroporous Graphene@g-C3N4 Composite Air Electrode for High-Energy Lithium Oxygen Batteries.

The nonaqueous lithium oxygen battery is a promising candidate as a next-generation energy storage system because of its potentially high energy density (up to 2-3 kW kg(-1)), exceeding that of any other existing energy storage system for storing sustainable and clean energy to reduce greenhouse gas emissions and the consumption of nonrenewable fossil fuels. To achieve high energy density, long cycling stability, and low cost, the air electrode structure and the electrocatalysts play important roles. Here, a metal-free, free-standing macroporous graphene@graphitic carbon nitride (g-C3N4) composite air cathode is first reported, in which the g-C3N4 nanosheets can act as efficient electrocatalysts, and the macroporous graphene nanosheets can provide space for Li2O2 to deposit and also promote the electron transfer. The electrochemical results on the graphene@g-C3N4 composite air electrode show a 0.48 V lower charging plateau and a 0.13 V higher discharging plateau than those of pure graphene air electrode, with a discharge capacity of nearly 17300 mA h g(-1)(composite) . Excellent cycling performance, with terminal voltage higher than 2.4 V after 105 cycles at 1000 mA h g(-1)(composite) capacity, can also be achieved. Therefore, this hybrid material is a promising candidate for use as a high energy, long-cycle-life, and low-cost cathode material for lithium oxygen batteries.

A facile approach to synthesize stable CNTs@MnO electrocatalyst for high energy lithium oxygen batteries.

A composite of manganese monoxide loaded onto carbon nanotubes (CNTs@MnO) has been synthesized by a facile approach, in which the CNTs form a continuous conductive network connecting the electrocatalyst MnO nanoparticles together to facilitate good electrochemical performance. The electrocatalyst MnO shows favourable rechargeability, and good phase and morphology stability in lithium oxygen batteries. Excellent cycling performance is also demonstrated, in which the terminal voltage is higher than 2.4 V after 100 cycles at 0.4 mA cm(-2), with 1000 mAh g(-1)(composite) capacity. Therefore, this hybrid material is promising for use as a cathode material for lithium oxygen batteries.

Preparation TiO2 core-shell nanospheres and application as efficiency drug detection sensor.

In this paper, we report the facile preparation of monodisperse titanium dioxide-diltiazem/tetrachlorobismuth core-shell nanospheres (TiO2@DTMBi), in which, diltiazem (DTM)/tetrachlorobismuth (BiCl4) complexes were employed as electroactive materials. The morphology, size, formation, and structure of the obtained TiO2@DTMBi spheres were investigated by transmission electron microscopy, scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and X-ray diffraction. The optimal condition of obtained monodisperse 40-nm TiO2@DTMBi spheres was researched. The results of using TiO2@DTMBi nanospheres as proposed drug sensor indicate a wide linear range (10(-7) to 10(-1) M) and a very low detection limit of 0.20 µg/mL.

Self-assembled organogels formed by L-leucine dihydrazide derivative.

A new organogelator, benzyl (4-methyl-1-oxo-1-(2-hexadecanoylhydrazinyl)pentan-2-yl)carbamate (designated as Cbz-Leu-HdHz), was designed and synthesized, which could self-assemble in many organic solvents and form the thermally reversible physical supramolecular organogels. The gel-sol phase transition temperatures (TGS) were determined as a function of gelator concentration and the corresponding enthalpies (ΔHg) were extracted. SEM, FT-IR and XRD were used for the investigations of the morphology and formation mechanism of organogels in the presence of the Cbz-Leu-HdHz. Based on the XRD data and molecular modeling, it was possible to propose packing modes for the formation of organogelator aggregates.

[Study of blood compatibility on TiO2 coated biomedical Ni-Ti shape memory alloy].

We coated a thin TiO2 film on the surface of Ni-Ti shape memory alloy by activated sputter method in the present work. The blood platelet adherence and antithrombogenicity of the TiO2-coated Ni-Ti alloy were evaluated. The results showed that the platelets on the TiO2-coated Ni-Ti alloy were fewer than those on 316L stainless steel, and no agglomeration or distortion for the platelets on the coated alloy was found, which means less probability of blood coagulation for the alloy. The coagulation time on the coated Ni-Ti shape memory alloy was longer than that on the 316L. Compared with that on the 316L stainless steel, the TiO2 coated Ni-Ti shape memory alloy showed better blood compatibility, indicating that the Ni-Ti alloy with TiO2 coating is a kind of ideal biomedical materials with high clinical value.

Synthesis and adsorption properties of titanosilicates ETS-4 and ETS-10 from fly ash.

ETS-4 and ETS-10 titanosilicates were prepared from fly ash and anatase, as silica and titanium sources respectively, via a hydrothermal procedure for the first time. The fusion of fly ash by alkali was carried out at a relatively low temperature and the use potassium fluoride salt was avoided in the synthesis of ETS. The by-product of this process is mainly NaCl, which is a useful source material for industry. The energy efficiency and yield of the synthesis process was improved by directly recycling the final filtrate after recovering the product viz ETS-4. All the ETS materials were characterized in terms of structural morphology, thermal stability and surface/pore properties. The properties of ETS-4 prepared from fly ash by the filtrate recycling method were comparable to that from commercial sources. The results show that ETS type materials can be prepared from cheaper resources, with good purity, comparable physico-chemical properties as well as excellent adsorption properties with lower environmental impact.

[Preparation of anodic oxidation layer on the surface of pure titanium and its biological activity study].

This paper introduces how TiO2 film was prepared on pure titanium by anodic oxidation. Surface morphology and composition of the oxide film were analyzed by SEM coupled with EDAX. The deposition ability of hydroxyapatite of the anodized titanium in simulated body fluid (SBF) at 37 degrees C was evaluated. The results indicated that the oxide film was rough and honeycomb holes, connecting with each other, could be found on the surface. The holes with the diameter of 1-2 microm were distributed uniformly, which was typical for anodic oxidation. After alkaline treatment, hydroxyapatite deposition on the oxidized specimens in SBF was improved significantly.

The effectiveness of strong afterglow phosphor powder in the detection of fingermarks.

There are numerous types of fluorescent fingermark powders or reagents used with the visualization of latent fingermarks deposited on multicolored substrate surfaces that can present a contrast problem if developed with regular fingermark powders. The developed fingermarks can show bright fluorescence upon exposure to laser, ultraviolet light and other light sources. These kinds of methods share a common concern, where surfaces and other substrates may fluoresce also. To overcome this concern, we have developed a phosphor powder which offers a strong afterglow effect which aid in the establishment of better fingermark detection. With the advent of a phosphor powder no special devices are required and the results obtained from fresh or a few days aged latent fingermarks left on: non-porous; semi-porous and also on some porous surfaces have been good. The strong afterglow effect offered by phosphor powder is also applicable for cyanoacrylate fumed fingermarks. Lift off and photography procedures of the developed fingermarks are incorporated in this paper.

[Determination of naphthenic acids in distillates of crude oil by gas chromatography/chemical ionization-mass spectrometry].

The petroleum carboxylic acids in 200-420 degrees C distillate of crude oil were separated by the extraction with column chromatography on an anion exchange resin. The effect of the composition and structure of naphthenic acids on separation were studied by the infra-red (IR) spectroscopic techniques. Naphthenic acids and iso-butane reagent gas were introduced into the ion source for chemical ionization, in which the ions represented by [M + C4H9]+ were used to calculate the relative molecular mass for each acid. Based on the mass spectra of pure fatty and naphthenic acids, in combination with the z-series formula CnH(2n + z)O2, the naphthenic acids can be classified into fatty, mono-, bi- ... hexa-cyclic types. The results indicated that the relative molecular mass range of naphthenic acids in this distillates was 170-510, and the carbon number range was C10-C35. The contents of bi-cyclic and tri-cyclic naphthenic acids were higher than others.