Preparation of a Nickel Layer with Bell-Mouthed Macropores via the Dual-Template Method

A relatively static and unique bubble template is successfully realized on a microporous substrate by controlling the surface tensions of the electrodeposit solution, and a nickel layer containing macropores is prepared using this bubble template. When the surface tension of the solution is 50.2 mN/m, the desired bubble template can be formed, there are fewer bubbles attached to other areas on the substrate, and a good nickel layer is obtained. In the analysis of the macropore formation process, it is found that the size of the bell-mouthed macropores can be tailored by changing the solution stirring speed or the current density to adjust the growth rate of the bubble template. The size change of a macropore is measured by the profile angle of the longitudinal macropore, section. As the solution stirring speed increases from 160 to 480 r/min, the angle range of the bell-mouthed macropores cross-sectional profile is increased from 21.0° to 44.3°. In addition, the angle range of the bell-mouthed macropore cross-sectional profile is increased from 39.3° to 46.3° with the current density increasing from 1 to 2.5 A/dm2. Different from the dynamic hydrogen bubble template, the bubble template implemented in this paper stays attached on the deposition and grows slowly, which is novel and interesting, and the nickel layer containing macropores prepared using this bubble template is applied in completely different fields.

Ultrafast Growth of Large Area Graphene on Si Wafer by a Single Pulse Current

Graphene has many excellent optical, electrical and mechanical properties due to its unique two-dimensional structure. High-efficiency preparation of large area graphene film is the key to achieve its industrial applications. In this paper, an ultrafast quenching method was firstly carried out to flow a single pulse current through the surface of a Si wafer with a size of 10 mm × 10 mm for growing fully covered graphene film. The wafer surface was firstly coated with a 5-nm-thick carbon layer and then a 25-nm-thick nickel layer by magnetron sputtering. The optimum quenching conditions are a pulse current of 10 A and a pulse width of 2 s. The thus-prepared few-layered graphene film was proved to cover the substrate fully, showing a high conductivity. Our method is simple and highly efficient and does not need any high-power equipment. It is not limited by the size of the heating facility due to its self-heating feature, providing the potential to scale up the size of the substrates easily. Furthermore, this method can be applied to a variety of dielectric substrates, such as glass and quartz.

A Quick and Accurate Method to Determine Submicron Size Coating Thickness Using Micro-Indentation along with a Mathematical Model

Hard and adherent wear-resistant thin surface coatings are synthesized on an aerospace alloy AA2219-T6 alloy using plasma-assisted physical vapor deposition. Submicron size TiN coatings with Ti interlayers are deposited and evaluated as a function of different deposition temperatures varying from 100 °C to 200 °C. Features of deposited surface layers are evaluated using different techniques; these include field emission scanning electron microscopy equipped with energy dispersive spectroscopy and X-ray diffraction. Mathematical models developed by Yu. A. Bykov and S. Hogmark are considered to estimate the coating thickness using the Composite Hardness measurements. The values predicted by Bykov’s model grossly underestimated the thickness values and thus a correction factor is proposed. The actual coating thickness is measured by sandwiching the thin coating between the substrate and electrolytically deposited nickel layer; the observations are made using field emission scanning electron microscope. The present study successfully used corrected Bykov’s Model along with micro-indentation proved to be an easy, quick and accurate method to estimate the coating thicknesses of thin hard coatings on the soft substrate over a wide range coating thicknesses.

An In-Situ Electroplating Fabricated Fabry-Perot Interferometric Sensor and Its Temperature Sensing Characteristics

In this study, in-situ electroplating method was used to fabricate a metal joint fixed extrinsic Fabry-Perot interferometric (EFPI) sensor. Specifically, optical fibers were firstly chemical plated with a very thin conductive nickel layer and then electroplated with nickel coating. After that, in-situ electroplating method was used to fix the metallized optical fibers and the capillary steel tube, the reflection spectra changes of the EFPI sensors during the in-situ electroplating process were recorded in real time, and the temperature sensing characteristics of the EFPI sensors were studied assisted by the temperature sensing system. Results show that: (i) optical fibers are well protected by the nickel layer; (ii) the reflection spectra of the EFPI sensors are clear and complete in the whole in-situ electroplating process, it is feasible to fabricate a EFPI sensor with the in-situ electroplating method; (iii) with the increases of temperature, the peak numbers of the reflection spectra of the EFPI sensors increase gradually; (iv) the EFPI sensors with different cavity length based on the in-situ electroplating method show excellent sensing characteristics, the temperature sensitivities reach up to about 700, 600, and 400 pm/°C from room temperature to 400 °C, respectively.

Preparation of Electroformed Copper-Nickel Multi-Nano-Layers and Characterization of Their Electromagnetic Shielding Effectiveness

Thin copper-nickel foil with multi-nano layers was prepared by pulse-electroforming to develop a high performance electromagnetic shielding material for electronic devices. The pulse electroforming conditions of the aqueous solution chemistry were selected based on the aqueous copper-nickel-sulfur phase diagram and an evaluation of the deposition rate using the finite element method based on the current distribution in front of a cathodic electrode. The thermodynamic stability diagram revealed that the coppernickel multi-nano layers could be formed at pH<4 and ΔE>1.0 V in a modified sulfide bath. The electro-formed copper-nickel multi-layer was well produced at the pulse plating conditions of –0.2V_SHE, –0.5 mA/cm², and 25 seconds for copper layer and –1.7 V_SHE, –50 mA/cm² and 80 seconds for nickel layer, which was composed of about 25 nm thick copper and about 30 nm thick nickel rich phases, respectively. The average deposition rate of the copper-nickel foil with multi-nano layers was estimated by the finite element method to be about 0.115 mm/sec, which was in good agreement with the real value of the thin multi-nano layered copper-nickel foil. The effectiveness of the electromagnetic shielding of the copper-nickel mesh with multi-nano layers was more than 30% higher than that of copper mesh in the frequency range of 8.2 and 12.5 GHz.