Jianwen Liu

Bio: Jianwen Liu is an academic researcher. The author has contributed to research in topics: Microstructure & Corrosion. The author has an hindex of 4, co-authored 7 publications receiving 21 citations.

Electrochemical characteristics of iridium coating by double glow plasma discharge process on titanium alloy substrates

Abstract: Iridium coating was fabricated by a double glow plasma discharge process on titanium alloy substrates. The electrochemical behaviours of the coating and the substrate were studied and compa...

The influence of current density and bath temperature on electrodeposition of rhodium film from sulfate–phosphate aqueous solutions

Abstract: Rhodium films were electrodeposited galvanostatically on copper–zinc alloy substrates from sulfate–phosphate aqueous solutions, in order to obtain a smooth, dense, and thick Rh film for electrical contacts. The influence of current density and bath temperature on phases, crystal structure, microstructure, and deposition rate of the film was studied. The phases and crystal structure, as well as microstructure of the film were determined by X-ray diffraction and scanning electron microscopy, respectively. The results showed that the current density and bath temperature had a significant influence on electrodeposition of rhodium film. The particles or aggregates on the surface evolved from fine to coarse and large with the increase of current density and bath temperature. By adjusting the deposition conditions, the optimized current density and bath temperature were 6.4–12.7 mA cm−2 and 50 °C, respectively. The film was composed of polycrystalline phase with monometallic form. The film was uniform and dense at low current density. The thickness of the film was up to 1.38–2.1 μm. At the optimal temperature of 50 °C, the surface of the film was smooth and fine. At the same time, the electrodeposition mechanism of the film was discussed. Rhodium films were electrodeposited from sulfate–phosphate aqueous solutions. The influence of current density and bath temperature on electrodeposition of the film was studied, and at the same time, the electrodeposition mechanism of the film was addressed.

Influence of thiourea on electroless Ni–P films deposited on silicon substrates

Abstract: Electroless nickel–phosphorus films were produced on silicon substrates in alkaline bath solutions, with the addition of thiourea in a concentration range of 1.0–5.0 mg L−1. The influence of thiourea on the chemical composition, morphology and corrosion resistance of the films was studied. The results revealed thiourea had a major influence on plating rate, phosphorus-content and aggregate size. The optimal content of thiourea was 1 mg L−1. Thiourea accelerated the deposition rate at low concentration of 1 mg L−1, but deceased the deposition rate and the phosphorus content at high concentration. The surface of the film without thiourea was smooth and dense. Also, with increasing thiourea content, the surface evolved into coarse nodular morphology with clear intercolonial boundaries. With the addition of 1 mg L−1 thiourea, the film had better corrosion resistance compared to film without thiourea.

Electrodeposition of Iridium-Nickel Thin Films on Copper Foam: Effects of Loading and Solution Temperature on HER Performance of Electrocatalyst in Alkaline Water

Abstract: Developing novel hydrogen evolution reaction (HER) catalysts with high activity, high stability and low cost is of great importance for the applications of hydrogen energy. In this work, iridium-nickel (Ir-Ni) thin films were electrodeposited on a copper foam as electrocatalyst for HER, and electrodeposition mechanism of Ir-Ni film was studied. The morphology and chemical composition of thin films were determined by scanning electron microscopy and energy-dispersive spectroscopy, respectively. The electrocatalytic performances of the films were estimated by linear sweep voltammograms, electrochemical impedance spectroscopy and cyclic voltammetry. The results show that Ir-Ni thin films were attached to the substrate of porous structure and hollow topography. The deposition of Ni was preferable in the electrolyte without the addition of additives, and Ir-Ni thin film was alloyed, resulting in high deposition rate for Ir42Ni58 thin film, and subsequently an increase of Ir content in the thin films of Ir80Ni20 and Ir88Ni12. Ir-Ni thin films with Tafel slopes of 40-49 mV·dec-1 exhibited highly efficient electrocatalytic activity for HER. The electrocatalytic activity of Ir-Ni thin films showed a loading dependence. As the solution temperature raised from 20 oC to 60 oC, the hydrogen evolution performance of Ir-Ni thin films improved. The apparent activation energy value of Ir88Ni12 film was 7.1 kJ·mol-1. Long-term hydrogen evolution tests exhibited excellent electrocatalystic stability in alkaline solution.

Recent developments in research of double glow plasma surface alloying technology: a brief review

Abstract: Higher performance is steadily required in the field of material surface engineering, especially in terms of surface degradation of mechanical parts and repair and renewal of surfaces. By preparing a more reasonable surface design and improving the surface composition and structure of the material, the surface modification layer can provide an important potential solution to the surface degradation problem. The coatings obtained by double glow plasma surface alloying (DGPSA) technology are a compelling method in current and future applications because of a unique combination of characteristics including pollution-free, the gradient distribution of the alloying elements and the strong metallurgical bonding between the alloying layer and the matrix. In recent years, with the increasing requirements for the surface properties of materials in various environments, the layer prepared by DGPSA technology is developing toward alloying, functionalization and nanometer. This review begins with a brief introduction of double glow plasma surface alloying. The recent developments of the double glow plasma surface alloying technology for improving various surface performance are systematically reviewed in the sight of applied material, background, duplex treatment and duplex coating preparation.

Texture orientation, morphology and performance of nanocrystalline nickel coatings electrodeposited from a Watts-type bath: Effects of H3BO3 concentration and plating time

Abstract: Nanocrystalline nickel coatings were electroplated from a Watts-type bath with the addition of H3BO3 ranging of 5–25 g·L−1. In order to study the evolution of preferential orientation of Ni electrodeposits, the microstructure, texture and grain size of the coatings deposited with different H3BO3 contents for different plating times were characterized by optical microscopy, scanning electron microscopy and X-ray diffraction, further the residual stress, microhardness, and abrasion resistance of the texture-oriented coatings were measured by X-ray diffraction, Vickers microhardness tester, and Calotester, respectively. The electrochemical corrosion resistance of the highly texture-oriented coatings and the substrate was evaluated by polarization and electrochemical impedance spectroscopy. The results show the preferential orientation of the coating was gradually changed from (200) to (220) crystal plane with increasing H3BO3 content after plating time of 1 h. The longer the plating time was applied, the higher the degree of Ni (200) orientation was produced at a low H3BO3 concentration of 5 g·L−1. The preferential orientation of the coatings at a high H3BO3 concentration of 25 g·L−1 was changed initially from (111) + (200) to (200) plane, then random orientation, and evolved to (220) plane after plating time of more than 20 min. The stability of various textures of Ni electrodeposits against plating time-H3BO3 concentration was established, and at the same time the microstructure-property relationship was developed. The average grain size of nickel coating was about 50–65 nm. The average residual stresses of the coatings with (200), (200) + (220) and (220) orientations were −64.3 ± 5 MPa, −477.2 ± 57 MPa and −618.0 ± 36 MPa, respectively. The microhardness of the coating increased gradually from 242.52 ± 10HV1 to 269.46 ± 12HV1 with increasing H3BO3 content because of the inverse Hall-Petch and grain orientation. The abrasion and corrosion resistances of (200)-oriented coatings were better than those of (220)-oriented coatings.

Galvanostatic Electrodeposition of Thin-Film Ir–Ni Electrocatalyst on Copper Foam for HER Performance in Alkaline Electrolyte

Abstract: Iridium–nickel (Ir–Ni) film is of great interest for catalytic and corrosive environment applications. Ir–Ni thin films as an electrocatalyst for hydrogen evolution reaction (HER) were galvanostatically electrodeposited on copper (Cu) foam from an electrolyte containing 13.5 mM sodium hexabromoiridate(III) and 40.5 mM Ni sulphate hexahydrate, simultaneously compared with electrodeposited Ir and Ni thin films. The top surface morphology of the film was characterized by scanning electron microscopy. The chemical composition of the film was determined by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy. The electrocatalytic performance was performed by linear sweep voltammogram and cyclic voltammetry. The results showed that Ir–Ni thin film adhered to Cu foam and the surface appeared much rougher than the surface of Ni film. The chemical composition of Ir in the deposit was 80 ± 1.2 at.%. The film was composed of nanograins. The top surface of as-deposited film was mainly composed of metallic state. However, the top surface of the film consisted of oxides states, such as Ni oxides or Ni(OH)2, and Ir oxides after electrochemical measurements. As-deposited Ir–Ni thin film with large real active area exhibited high efficient electrocatalytic activity for HER, and achieved a current density of 10 mA cm2 at an overpotential of 60 mV and a Tafel slope of 40 mV dec−1, which is superior to pure Ir and Ni thin films. The remarkable increase in electrocatalytic activity for Ir–Ni film was ascribed to both increased surface area of active centers due to relatively rough and electrocatalytic synergism of Ir and Ni for the HER. Ir–Ni thin film electrodeposited on a foam copper electrode was used as an electrocatalyst for HER. The surface of as-deposited film was composed of metallic state. As-deposited Ir–Ni thin film with large real active area exhibited high efficient electrocatalytic activity for HER, and achieved a current density of 10 mA cm2 at an overpotential of 60 mV and a Tafel slope of 40 mV dec−1, which is superior to pure iridium and Ni thin films. As-deposited film possessed a good stability by accelerated degradation studies.