Microstructure and Corrosion Resistance of Electrodeposited Ni-Cu-Mo Alloy Coatings

This paper deals with the electrodeposition of Ni-Cu-Mo ternary alloy coatings on low-carbon steel substrate from an aqueous citrate sulfate bath. The structures and microstructure of coatings were characterized by scanning electron microscopy and x-ray diffractometry. The corrosion resistance of coatings was investigated by potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy techniques. The results show that the Ni-Cu-Mo coatings are mainly composed of fcc-Ni phase and a small amount of NiCu phase. Ni-Cu-Mo coatings exhibit a nodular surface morphology, and the roughness of electroplated coating increases with the increasing of Na₂MoO₄·2H₂O in the bath. The corrosion performance of the coatings is significantly affected by the Mo content of the alloy coating and their surface morphology. The coating prepared in bath containing 40 g/L Na₂MoO₄·2H₂O has the highest corrosion resistance in 3.5 wt.% NaCl solution, while that prepared in bath containing 60 g/L (or more) Na₂MoO₄·2H₂O shows a lower corrosion resistance due to the presence of microcracks on the coating surface.     

通过水性还原法用NaBH4制备纳米铜颗粒过程中反应参数对制备过程的影响（英文）

通过水溶液还原法制备纳米铜颗粒,研究了不同反应条件对制备纳米铜的影响。制备纳米铜的最优条件是:当溶液 pH为12、温度为 313K、1%的明胶作为分散剂时,将0.4mol/L NaBH4加入含有 1.2mol/L 氨水的0.2mol/L CuSO4溶液中。此外,进行了一系列实验来模拟反应进程。结果表明,氨水能改变反应进程。当溶液 pH为10时,氨水将Cu2+转化为铜氨络合物,然后被 NaBH4还原为铜颗粒。当溶液pH为12时,氨水将Cu2+转化为氢氧化铜,然后被 NaBH4还原为铜颗粒。     

Microstructure, Mechanical Properties, and Pyroconductivity of NiFe2O4 Composite Reinforced with ZrO2 Fibers

NiO-Fe₂O₃-ZrO_2f composites were fabricated by a two-step sintering process. No phase transformation for ZrO_2f was observed. The as-prepared NiO-Fe₂O₃-ZrO_2f ceramic showed excellent mechanical properties because of the introduction of ZrO₂ fiber. The values for both the bending strength and fracture strength of 3 wt.% ZrO_2f-reinforced NiFe₂O₄ samples reached the maximum values of ~89.0 MPa and ~4.67 MPa m^1/2, respectively, The toughness mechanism is mainly attributed to fibers’ fracture, crack deflection, fibers’ pull-out, and fibers’ debonding. The conductivity of ZrO_2f-reinforced NiFe₂O₄ is dependent on temperature and ZrO_2f content. When the electrolytic temperature is up to 950 °C, the conductivity value of the sample reinforced with 4 wt.% ZrO₂ fibers is 0.63 S/cm, which has been improved by 37.8% compared with the conductivity value of 0.45 S/cm for the un-doped samples. The main conductive mechanisms of ZrO₂ fiber in the matrix are the one based on the substitution of Zr⁴⁺ ions to produce quasi-free electrons, and the other based on oxygen ionic conducting mechanism.     

Electrochemical characteristics of 316l stainless steel processed with a thermally treated Ni- and Cr-rich surface coating

The influence of a thermally treated Ni-Cr rich protective coating on the corrosion behavior and contact resistance of stainless steel in a 0.1NH₂SO₄+ 2 ppmHF electrolyte at 80 °C was evaluated using electrochemicals, interfacial contact resistance (ICR) measurements and X-ray photoelectron spectroscopy. Through a low-cost, continuous production line, the Ni-rich coating film for stainless steels was developed by dipping steel samples in acrylic resin and CrO₃ solutions with different levels of NiSO₄·6H₂O added as a nickel source. Each sample was then heated at 800 for 10 min in a hydrogen-reducing environment. It was shown that an increase in residual Ni content in the surface coating noticeably lowered the interfacial contact resistance and raised the corrosion resistance, depending on the remaining nickel content and the thickness of the surface coatings. In support of the XPS depth profile, this was ascribed to the relative enrichment of the Ni element and the detectable reduction of oxygen content in the coating, which could be associated with the significant evaporation of acrylic resin that occurred during thermal treatment. The optimum Ni composition in the resultant coating film, achieved through the addition of 15 wt.% NiSO₄·6H₂O to the acrylic resin and CrO₃ solution, was estimated to be about 10 wt.%.     

The Electrodeposition of Iron-Zinc Alloys

Methods are given for depositing iron-zinc alloys of 3 to 90% zinc content from sulphate baths and attention is drawn to the useful properties of these deposits. Under a given set of plating conditions the iron-zinc ratio in the deposit is directly proportional to that in the bath. Lowering either the current density or the pH raises the zinc content of the deposit. Some baths have a levelling action, since bright deposits can be prepared from them on an etched surface. Examples of such baths are: (i) FeSO₄-7H₂O 248, ZnSO₄-7H₂O 8·8, (NHJ₄)₂SO₄ 118, KCl 10, citric acid 0·5 g./l., operated at pH 1·7, 50°G, 200 amps./ft.² and giving a 6% zinc alloy of 560 D.P.N, hardness;

(ii) FeSO₄-7H₂O 174, ZnSO₄-7H₂O 88, (NH₄)₂ SO₄ 118, KCl 10, citric acid 0·5 g., Teepol 0·4 ml./l., operated at pH 1·7, 50°C, 180 amps./ft.² and giving a 60% zinc alloy of 350 D.P.N, hardness.

The throwing power of the baths is comparable with that of a bright nickel bath. Pitting can be overcome by using a wetting agent (Teepol or Lubrol W) and operating at high temperature (80° C.) and low pH (<1·8). Under these conditions the deposits are usually matt and light grey in colour.

Alloys with zinc contents >ca. 30% have electrode potentials in N/10 KCl nearly equal to that of pure zinc. In the C.R.L. beaker test, the alloys with zinc contents between 30 and 90% are, in general, more corrosion resistant than pure zinc. Various applications of these alloys are proposed, including their use as an undercoat for paints and chromium plating and for decorative finishes indoors.

Deposition of iron-zinc alloys from chloride baths is dealt with briefly. A matt, corrosion-resistant alloy of 60% zinc content can be obtained, at pH 1·8, 50° C., and 50 amps./ft.², from a vigorously stirred bath of the following composition:—FeCl₂·4H₂O 177, ZnCl₂ 42, NH₄Cl 100, KCl 15, citric acid 0·5 g./l.

A colorimetrie method for the analysis of zinc in the presence of iron is described.     

Synthesis of LiFePO<Subscript>4</Subscript> using FeSO<Subscript>4</Subscript>·7H<Subscript>2</Subscript>O byproduct from TiO<Subscript>2</Subscript> production as raw material

As the byproduct of TiO₂ industrial production, impure FeSO₄·7H₂O was used for the synthesis of LiFePO₄. With the purified solution of FeSO₄·7H₂O, FePO₄·xH₂O was prepared by a normal titration method and a controlled crystallization method, respectively. Then LiFePO₄ materials were synthesized by calcining the mixture of FePO₄·xH₂O, Li₂CO₃, and glucose at 700°C for 10 h in flowing Ar. The results indicate that the elimination of FeSO₄·7H₂O impurities reached over 95%, and using FePO₄·xH₂O prepared by the controlled crystallization method, the obtained LiFePO₄ material has fine and sphere-like particles. The material delivers a higher initial discharge specific capacity of 149 mAh·g⁻¹ at a current density of 0.1C rate (1C = 170 mA·g⁻¹); the discharge specific capacity also maintains above 120 mAh·g⁻¹ after 100 cycles even at 2C rate. Thus, the employed processing is promising for easy control, low cost of raw material, and high electrochemical performance of the prepared material.     

Separation and Precipitation of Nickel from Acidic Sulfate Leaching Solution of Molybdenum-Nickel Black Shale by Potassium Nickel Sulfate Hexahydrate Crystallization

Nickel was separated and precipitated with potassium nickel sulfate hexahydrate [K₂Ni(SO₄)₂·6H₂O] from acidic sulfate solution, a leach solution from molybdenum-nickel black shale. The effects of the potassium sulfate (K₂SO₄) concentration, crystallization temperature, solution pH, and crystallization time on nickel(II) recovery and iron(III) precipitation were investigated, revealing that nickel and iron were separated effectively. The optimum parameters were K₂SO₄ concentration of 200 g/L, crystallization temperature of 10°C, solution pH of 0.5, and crystallization time of 24 h. Under these conditions, 97.6% nickel(II) was recovered as K₂Ni(SO₄)₂·6H₂O crystals while only 2.0% of the total iron(III) was precipitated. After recrystallization, 98.4% pure K₂Ni(SO₄)₂·6H₂O crystals were obtained in the solids. The mother liquor was purified by hydrolysis-precipitation followed by cooling, and more than 99.0% K₂SO₄ could be crystallized. A process flowsheet was developed to separate iron(III) and nickel(II) from acidic-sulfate solution.     

Formation and growth mechanism of a manganese phosphate coating on an as-cast Zr–Al binary alloy

The preparation of a manganese phosphate coating on an as-cast Zr–Al alloy is described. The alloy consisted of an α phase (α-Zr) and a β phase (Zr₂Al), where α-Zr is the matrix and Zr₂Al spreads along the grain boundaries discontinuously. The coating was divided by cracks to exhibit a network structure. The manganese phosphate coating showed a combination of crystalline and amorphous structure. The film consists of small particles densely packed. It is uniform and compact. The formation of the phosphate coating on substrates treated for short periods was investigated. Mn₅(PO₄)(OH)₂·H₂O and MnZr(PO₄)₂·4H₂O phases were found in the manganese phosphate coatings. The grain particles are preferentially deposited on the β phase rather than on the α phase.     

Effects of synthesized 4PbO·PbSO4 on the Initial capacity and cycle performance of lead dioxide electrode prepared by cementation leady oxide

The service life of lead-acid batteries is often limited by disintegration of the positive active mass structure. It is known that the latter depends on the phase composition, crystal morphology and paste density. In general, the electrode whose active mass is prepared from 4PbO·PbSO₄ pastes (denoted by 4BS_pas) has about 30% longer cycle lives than those obtained by 3PbO·PbSO₄·H₂O. Therefore, the initial capacity and cycle performance of lead dioxide electrodes prepared from 10, 30 and 50 wt.% 4BS_syn (chemically synthesized 4PbO·PbSO₄) addition with regard to the amount of cementation leady oxide were examined. Lead oxide (denoted by cementation leady oxide) was prepared by the pulverization of sponge lead prepared from a cementation reaction under the conditions of 90°C and 1.0 wt%HCl solution. 4BS_syn crystals were chemically synthesized in 40.1 wt.%H₂SO₄ with \-PbO. Without 4BS_syn, crystals lead dioxide electrode has shown a higher initial capacity than any other 4BS_syn contents and cycle performance was the best although the initial capacity is relatively low for 50 wt.% 4BS_syn.     

Humidity-sensitive property of Fe2+ doped polypyrrole

A simple chemical method was employed to form Fe²⁺ doped polypyrrole (PPY) by the introduction of hydrated ferric chloride (FeCl₃·6H₂O) during the polymerization of pyrrole, where FeCl₃·6H₂O played a role of oxidant for the polymerization and the in situ forming reduced product (FeCl₂·2H₂O) was well doped in PPY. The resultant Fe²⁺ doped PPY species were characterized by using various techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electronic microscope (FE-SEM). Humidity-sensitive properties of the samples were also examined. The Fe²⁺ doped PPY exhibited a fast response to humidity change (about 20 s), in which great changes of more than three orders (nearly four) of magnitude in impedance was observed when relative humidity was varied over the whole range. The improved properties may be related to the presence of the hydrophilic Fe²⁺, and a possible mechanism was also provided.     

Characterization of Hydrogen Permeation in Armco-Fe during Cathodic Polarization in Aqueous Electrolytic Media

The study of hydrogen permeation behavior in Armco-Fe showed that 0.1 M H₂SO₄ was a more effective medium for cathodic polarization compared to 0.1 M NaOH. When both electrolytes were “poisoned” with 1.00 g/L Na₂HAsO₄ · 7H₂O, as hydrogen recombination inhibitor, the corresponding hydrogen permeation levels were 3.5 × 10⁻⁵ A/cm² in 0.1 M H₂SO₄ while 0.75 × 10⁻⁵ A/cm² in 0.1 M NaOH. The breakthrough times were less than 30 s in 0.1 M H₂SO₄, while about 100 s in the NaOH. With varying amounts of “poisons”, peak permeation of hydrogen (1.75 × 10⁻⁵ A/cm²) was achieved with 10 g/L Na₂HAsO₄ · 7H₂O in 0.1 M H₂SO₄, while the least permeation resulted with 10 g/L (NH₂CSH₂) Thiourea addition for same level of 1.00 mA/cm² cathodic polarization.     

疏水性硼酸镧纳米棒的制备及其在菜籽油中的摩擦磨损性能(英文)

采用水热法合成油酸修饰的硼酸镧纳米棒(OA/La BO3·H2O),利用X射线衍射和扫描电镜等测试技术对其微观结构进行表征,并在四球摩擦试验机上考察其在菜籽油中的摩擦磨损性能。结果表明,所制备的OA/La BO3·H2O为直径约50 nm、长达500 nm的疏水性纳米棒。OA/La BO3·H2O能显著提高菜籽油的抗磨减摩性能;当OA/La BO3·H2O的添加量为1%(质量分数)时,菜籽油的抗磨减摩性能最佳。     

Solid-Liquid Equilibrium for Quaternary System Na2SO4-NaCl-H2O2-H2O at 283.15 K

The solid-liquid phase equilibrium for the quaternary system Na₂SO₄-NaCl-H₂O₂-H₂O was studied at 283.15 K by Schreinemaker’s wet residues method. The solubility data for the quaternary system were measured, and the phase diagram was constructed. When the concentration of hydrogen peroxide employed in the experiments was below 50 mass%, four solid phases were present in the quaternary system, which corresponded to NaCl, Na₂SO₄·10H₂O, Na₂SO₄·0.5H₂O₂·H₂O, and 4Na₂SO₄·2H₂O₂·NaCl. The phase diagram of the quaternary system included two invariant points and four crystalline zones. The crystalline region of 4Na₂SO₄·2H₂O₂·NaCl was larger than those of NaCl, Na₂SO₄·10H₂O, or Na₂SO₄·0.5H₂O₂·H₂O.     

TiC含量对激光选区熔化Inconel 625合金微观组织及表面摩擦磨损性能的影响

为了提高3D打印镍基高温合金强度、硬度及耐磨性能,使用激光选区熔化技术(Selective laser melting,SLM)制备添加不同质量分数TiC增强Inconel 625合金材料,并对比添加不同质量分数TiC(4 wt.%和8 wt.%)所制备的SLM TiC/Inconel 625试样的摩擦磨损性能。结合X射线衍射仪(XRD),金相显微镜(OM),扫描电子显微镜(SEM)及能谱分析(EDS)等材料表征手段对TiC/Inconel 625试样的物相分布,微观组织结构及磨损前后的元素分布进行对比分析。结果表明,随着TiC含量的增高,SLM TiC/Inconel 625硬度从325 HV_(0.2)(不含TiC)升高到了587 HV_(0.2)(SLM 8 wt.%TiC/Inconel 625),磨损率也由22.4×10~(-5)mm~3/(N·m)下降为9.8×10~(-5)mm~3/(N·m)。其中,平均摩擦磨损系数最小的为SLM 4 wt.%Ti C/Inconel 625 (COF=0.47)。综合对比可以发现通过添加适量的TiC颗粒可以有限改善SLM Inconel 625的硬度及耐磨损性能。     

Electrochemical behavior of zirconium in molten NaCl-KCl-K<Subscript>2</Subscript>ZrF<Subscript>6</Subscript> system

The electrochemical reduction of Zr4+(complex) ions in NaCl-KCl-K2ZrF6 molten salt on Pt electrode was investigated using cyclic voltammetry and square wave voltammetry at 1023 K.Two cathodic reduction peaks related to Zr4+/Zr2+ and Zr2+/Zr steps were observed in the cyclic voltammograms.The result was also confirmed by square wave voltammetry.The diffusion coefficient of Zr4+(complex) ions at 1023 K in NaCl-KCl-K2ZrF6 melt,measured by cyclic voltammetry,is about 4.22×10-6 cm2/s.The characterization of the deposits obtained by potentiostatic electrolysis at different potentials was investigated by XRD,and the results were well consistent with the electrochemical reduction mechanism of Zr4+(complex) ions.     

Preparation of Al-Si Master Alloy by Electrochemical Reduction of Fly Ash in Molten Salt

An electrochemical method on preparation of Al-Si master alloy was investigated in fluoride-based molten salts of 47.7wt.%NaF-43.3wt.%AlF₃-4wt.%CaF₂ containing 5 wt.% fly ash at 1233 K. The cathodic products obtained by galvanostatic electrolysis were analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy, and energy-dispersive spectrometry. The result showed that the compositions of the products are Al, Si, and Al_3.21Si_0.47. Meanwhile, the cathodic electrochemical process was studied by cyclic voltammetry, and the results showed the reduction peak of aluminum deposition is at ?1.3 V versus the platinum quasi-reference electrode in 50.3wt.%NaF-45.7wt.%AlF₃-4wt.%CaF₂ molten salts, while the reduction peak at ?1.3 V was the co-deposition of aluminum and silicon when the fly ash was added. The silicon and iron were formed via both co-deposition and aluminothermic reduction. In the electrolysis experiments, current efficiency first increased to a maximum value of 40.7% at a current density of 0.29 A/cm², and then it decreased with the increase of current density. With the electrolysis time lasting, the content of aluminum in the alloys decreased from 76.05 wt.% to 48.29 wt.% during 5 h, while the content of silicon increased from 15.94 wt.% to 37.89 wt.%.     

Microwave Power Absorption in Materials for Ferrous Metallurgy

The characteristics of microwave power absorption in materials for ferrous metallurgy, including iron oxides (Fe₂O₃, Fe₃O₄ and Fe₀.₉₂₅O) and bitumite, were explored by evaluating their dielectric loss (Q _E) and/or magnetic loss (Q _H) distributions in the 0.05-m-thick slabs of the corresponding materials exposed to 1.2-kW and 2.45-GHz microwave radiation at temperatures below 1100°C. It is revealed that the dielectric loss contributes primarily to the power absorption in Fe₂O₃, Fe_0.925O and the bitumite at all of the examined temperatures. Their Q _E values at room temperature and slab surface are 9.1311 × 10³ W m^?3, 23.7025 × 10³ W m^?3, and 49.5999 × 10³ W m^?3, respectively, showing that the materials have the following heating rate initially under microwave irradiation: bitumite > Fe_0.925O > Fe₂O₃. Compared with the other materials, Fe₃O₄ has much stronger power absorption, primarily originated from its magnetic loss (e.g., Q _H = 1.0615 × 10⁶ W m^?3, Q _H/Q _E = 2.4185 at 24°C and slab surface), below its Curie point, above which the magnetic susceptibility approaches to zero, thereby causing a very small Q _H value at even the surface (Q _H = 1.0416 × 10⁵ W m^?3 at 880°C). It is also demonstrated that inhomogeneous power distributions occur in all the slabs and become more pronounced with increasing temperature mainly due to rapid increase in permittivity. Characterizing power absorption in the oxides and the coal is expected to offer a strategic guide for improving use of microwave energy in ferrous metallurgy.     

The influence of carbonaceous surface impurities on excrescence initiation in the rimming steel/CO2/CO system

The influence of surface carbon contamination in determining the sites of excrescence growth has been studied, for the reaction of rimming steel in carbon dioxide containing 1·5%CO + 1000 ppm H₂O + 10 ppm CH₄ at 17·25 × 10⁶ N m^?2 and 450°C. Patterns visible in the oxide layer in the early stages of oxidation can be attributed to hydrocarbon impurities remaining on surfaces not rigorously cleaned. The impurity can accumulate at specific areas on the surface and can then accelerate oxidation such that excrescences start growing early in the normally protective stage. Surface cleaning procedures and their limitations for corrosion studies are discussed.     

Synthesis and Properties of La2O3-Doped 8 mol% Yttria-Stabilized Cubic Zirconia

In this study, 8 mol% yttria-stabilized cubic zirconia (8YSZ) powder as a matrix material and 0-15 wt.% La₂O₃ powder as an additive were used to determine the effect of La₂O₃ addition and its amount on the phase stability, microstructure, sintering, and mechanical properties of 8YSZ. Colloidal processing was used to mix the powders uniformly and to obtain a homogenous microstructure. XRD results showed the existence of only a cubic crystal structure for 1 and 5 wt.% La₂O₃ addition amounts. However, La₂Zr₂O₇ with a hexagonal and cubic crystal structure was observed in 8YSZ specimens doped with 10 and 15 wt.% La₂O₃. Further, up to 5 wt.% La₂O₃ was completely dissolved in the crystal structure of the specimens; however, above 5 wt.%, La₂O₃ reacted with 8YSZ at high temperatures and formed pyrochloric La₂Zr₂O₇. Grain size measurements revealed that the grain size of 8YSZ increased up to 1 wt.% La₂O₃ addition, and then decreased beyond this amount. The hardness and fracture toughness of 8YSZ decreased and increased, respectively, with the increasing La₂O₃ amount.     

Corrosion Products Formed on Copper exposed to humid SO2-containing atmospheres

X-ray diffraction analyses have been performed on samples of electrolytic copper (min. 99,9% Cu) exposed to humid atmoshperes at SO₂-supplies of 10 and 100μg SO₂ per cm² surface area per hour (10 and 100 ppm SO₂. respectively). During the SO₂ -exposures copper (II) sulphate (CuSO₄ · 5 H₂O) were the only crystalline phases formed in detectable amounts. Interruption of the SO₂- supply resulted in the formation of copper (I) oxide and antlerite (CuSO₄) · 2Cu (OH)₂. During prolonged exposure brochanite (CuSO₄ · 3Cu(OH)₂) and langite (CuSO₄· 3Cu(OH)₂) and langite (CuSO₄ · Cu(OH)₂ · 2H₂O) were also formed i. E. the Cu:S ratio of the basic copper sulphates increased with time. The formation of antlerite was preceeded by formation of an unidentified intermediate compound, probably a basic copper sulphate with a Cu:S ratio of less than three, and a simultaneous transformation of the copper (II) sulphate and copper (I, II) sulphite formed during the SO₂-exposure.