Dr Mohammad Sakhawat Hussain

PhD (Aston) FIMF FIMMM CEng

Department of Materials Engineering Faculty of Mechanical Engineering Universiti Teknologi Malaysia

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Direct nano-crystalline Ni plating on titanium surfaces

OUTLINE PRESENTATION

• An innovative process for depositing Ni

directly on Ti surfaces without the need to

pre-treat the substrates with acid/s and pre-

plate with an intermediate metallic layer

• As deposited Ni is nanocrystalline

• Nanomechanical test results to evaluate the

mechanical properties of the as plated

Ti/TiO2/Ni

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Direct plating on Ti

High speed electroplating, which I have

used for the first time to plate nickel on

aluminium, titanium and stainless steel

without any pretreatment process.

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In order to plate nickel on titanium, oxide layers must be

removed first by acid etching and plated with

displacement reaction.

The function of these immersion coatings is the

replacement of the natural oxide always present on Ti

irrespective of the cleaning process, with an oxide free

metal on which adherent metallic coatings can be

deposited.

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D.C Power Supply

(Rectifier)

+

_

Ni Anode

Cathode Flow

Meter

Filter

Magnetic Pump Ni solution

Control unit Temperature composition

A Schematic diagram of the plating equipment designed for depositing Ni directly on titanium.

Out In

Low Speed solution Movement

High Speed solution Movement

Ti base metal

Oxide layer

Ni Deposit

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Schematic Diagram: Aluminium has a porous and a fine compact oxide layer before pure Al can be exposed (the thickness of these oxide layers is less than 10 nanometer).

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Aluminium has a porous and a fine compact oxide layer before pure Al can be exposed (TEM images showing oxide structures enlarged after anodizing )

TEM images showing oxide structure

HIGH SPEED ELECTROPLATING PARAMETERS

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Research Methodology

SOLUTION PREPARATION

Type Constituents Typical Concentration

g/l pH

Watt’s Solution NiSO4.7H2O

NiCl2.6H2O

H3BO3

300 45 38

3.5 – 5.5

Nickel Sulphate Solution

NiCl2.6H2O

H3BO3

300 38

2.5

MORPHOLOGY ANALYSIS

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Research Methodology

• Specimen were cut by cross

section

• Specimen were mounted

using cold mounting

• Sample were grinding and

polished with different

abrasive paper.

• The thickness of nickel layer

were measured using SEM to

determined the effect of

different solution, current

density and temperature

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Mechanism of electroplating and structure of electroplated coatings.

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SEM image – surface view of the Ni deposits showing the mechanism nucleation and growth of nano-crystalline Ni layer

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ADHESION TESTING

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Research Methodology

• Adhesion testing is required to quantify the

strength of the bond between the nickel layer

and aluminium substrate.

• Adhesion testing according to ASTM D6677

and ASTM D3359

• ASTM D6677 - Adhesion testing by knife

• ASTM D3359 - Adhesion testing by tape test

ADHESION ANALYSIS

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Results & Discussion

• The sample of nickel layer which electroplated

on high current density were easily to peeled off

compared to sample which electroplated on low

current density.

I = 1 A at 55 oC I = 1 A at 65 oC

Figure 4.: Nickel plating samples after adhesion testing.

• Hardness – resistance to penetration of a hard indenter • Load is applied • Plastic zone forms • Hardness determined from optical measurements

Background: hardness testing

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Micro- vs nanoindentation

• Force, displacement and time are recorded throughout the test • Optical inspection of hardness impression is not required • No other technique provides quantitative information on both elastic and plastic

properties of thin films and small volumes • Ideal for thin films, coatings, nanocomposites, biomaterials…

Nanoindentation

• Force is applied and optical inspection of hardness impression necessary • No information on elastic modulus • Results less useful for wear prediction • Not suitable for thin films or coatings, or highly localised measurements…

Hardness and micro-hardness testing

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Fig.5. Nanomechanical test results – carried out on plated Al/(Al2O3)/Ni layers. The measured indentation modulus (Er) and hardness shows significant differences between the Ni plated layer and the aluminium base, however, the interface i.e. the oxide layer has very different measured values compared to Ni and Al.

Ni

Al

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HRTEM Image showing 3 distinct layers i.e. Al, the oxide layer and the Ni coating. There is no sign of any porous Al layer.

Improved equipment for direct electroplating by using high speed electroplating process

Product of new equipment

CONCLUSIONS • It has been possible to plate nickel directly on titanium without any pre-

treatment process, using a basic power supply and without any additives

• As plated the Ni is nanocrystalline

• Nanomechanical tests show Ni, aluminium oxide and Al all have different modulus and Hv, however, the oxide layer is much softer than expected and has shown inconsistent properties which indicates that the natural oxide was responsible for this inconsistencies.

• By increasing the temperature, the weight and thickness of the layer also increase.

• Nickel sulphate solution gives higher rate of deposition compare to the watt’s solution.

• Adhesion between nickel and aluminium became low at current above 1 A. Nickel layer is easily to peel off.

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Acknowledgement This work has been sponsored by Research

Management Centre (RMC), Universiti Teknologi

Malaysia.

Industrial Partners:

• Hysitrion Inc. USA

• Micro Materials Ltd, UK

• MEng Research students (Nanomaterials Synthesis Group),

Dept of Materials Engineering, UTM

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THANK YOU

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