Application of nickel nanoparticles in diffusion bonding of stainless steel surfaces презентация

Содержание

Слайд 1Application of Nickel Nanoparticles in Diffusion Bonding of Stainless Steel Surfaces
Santosh

Tiwari and Brian K. Paul
School of Mechanical, Industrial and Manufacturing Engineering
Oregon State University

Слайд 2Microfluidic Technology
Analytical Microfluidics
Arrayed Microfluidics


Слайд 3Emerging Industry

Fuel Processing
Chemical Processing
Heating & Cooling
Nanomaterial Synthesis
Separations


Слайд 4200 µm wide channels

“Number Up” Channels
channel header
channels
Single Lamina


Channels
200 µm wide;

100 µm deep
300 µm pitch
Lamina (24” long x 12” wide)
~1000 µchannels/lamina
300 µm thickness

Patterning:
photochemical machining


Слайд 5“Number Up” Laminae



Device (12” stack)
~ 1000 laminae
= 1 x 106 reactor

µchannels

Laminae (24” long x 12” wide)
~1000 µchannels/lamina
300 µm thickness

Bonding:
diffusion bonding

Patterning:
photochemical machining


Слайд 6Outline
Motivation and Objective
Approach
Results
Summary


Слайд 7Diffusion Bonding: Concept
Initial 'point' contact


b) Yielding and creep leading to

reduced voids

c) Final yielding and creep (some voids left)


d) Continued vacancy diffusion, leaving few small voids

e) Bonding is complete

Слайд 8Diffusion Brazing of SS 316L
Filler materials such as Ni, Cu, Au

etc.
Nickel
Almost 100 % solid solubility in Fe
Good corrosion and wear resistance
Compatible with stainless steel
Temperature depressant materials (TDMs) like Si, B, P etc. added to reduce the melting temperature
Transient liquid phase bonding
Adverse effect of TDMs
Formation of secondary phases
Bond strength and ductility ▼
Additional heat treatment cycle ~ up to 24 hrs
Time and Cost ▲

Слайд 9Analysis of Microchannel Samples
Objective
To Compare the diffusion bonded and
Nickel-Phosphorous (NiP)

diffusion brazed
samples to obtain
the characteristics of bonding
effect of NiP interlayer

Bonding conditions

Слайд 10Scanning Electron Microscopy
SEM image of bond line for diffusion bonded sample
SEM

image of bond line for diffusion brazed sample

two phases present

intermetallic?



Слайд 11Defect Quantification
µm, %


Слайд 12Wavelength Dispersive X-ray Spectroscopy


Слайд 13Nanoscale Materials in Chemistry, Wiley, 2001
Q Jiang, Materials chemistry and physics,

v. 83, 2003, pp. 225-227

Au

Ag

“As the size decreases beyond a critical value, due to the surface –to-volume ratio, the melting temperature decreases and becomes size dependent”

Nano Al : 2nm (200oC) and 9nm (660oC)

Generally, critical value is ~10nm

Effect of NP Size on Properties


Слайд 14Role of Nanoparticles
Nano-sized particles
exhibit lower melting temperature than the bulk

material
lower activation energy required to liberate atoms from the surface
tremendously high surface area causing higher diffusion rate

The densification rate during sintering

Ω: geometric correction factor
γsv: interfacial energy
Dv: volume diffusion co-efficient
G: grain size
Vs: fractional porosity


Слайд 15Outline
Motivation and Objective
Approach
Results
Summary


Слайд 16Objective and Protocol
Objectives
to compare NiNP-brazed samples with diffusion bonded and NiP

diffusion brazed samples
to investigate the microstructural evolution and bond strength of the stainless steel shims bonded using a Ni NP interlayer

Sample Preparation

Materials
Stainless steel 316L shims of 1.0 mm thickness (1”x1”)
Suspension: Nicrobraz binder mixed with Ni nanoparticles
Processing
Laser machining and deburring
Coating of NiNPs: ~5 µm thick
Drying: 200°C for 30 min
Diffusion bonding

Слайд 17Deposition from NP suspension
Spin Coating
Small capital cost
Faster Process
Low contamination
Patterned

surface
Edge effect
Wastage of material

Drip Coating
Small capital cost
Patterned surface
Less wastage of material
Non-uniformity of the coating
Agglomeration
Very crude method


Слайд 18Nicrobraz Binder
A commercially available water based binder (Wall Colmonoy Corporation)
Low viscosity:

better for deposition
Readily wets the surface of clean metal substrates
Excellent adherence and a relatively short drying time
Low content of binder material to minimize outgassing during the bonding cycle
All binding material volatilizes by 540°C leaving behind the compact layer of particles
No residue remains on the parts after brazing, when using nickel-based filler metals
Ideally suited for application of nickel-based brazing filler metals

Слайд 19Film Characterization
Continuous and uniform film
Nanoparticle film (50 to 100 nm dia.)

implying that high diffusion rate still achievable at relatively lower temperatures

SEM images of the (a) coated and (b) dried (200°C, 30 min) nickel nanoparticles film on SS substrate

a

b


Слайд 20Experimental Design


Слайд 21Outline
Motivation and Objective
Approach
Results
Summary


Слайд 22Bonded and Brazed Samples
Surface etched with “Aqua-Regia” (3HCl + HNO3)
Evidence

of phase change!

Слайд 23Experimental Design
Process flow chart for bonding of SS with NiNP

interlayer

Слайд 24Void Fractions
Key findings
2X time makes no statistical difference
Temperature above 800 C

makes little difference
Major advantage going from 750 and 800 C

Слайд 25Bondline Characterization 50 nm Ni on SS
1000X – X-section of nano

Ni bonded SS; 750 C, minutes


500X – X-section of nano Ni bonded SS; 800 C, minutes

Evidence of phase change between 750 and 800 C!


Слайд 26Summary
A 50 nm+ dia. nickel nanoparticle (NiNP) interlayer has been shown

to:
lower the bonding temperature for diffusion brazing
eliminate the use of melting temperature depressants
NiNP-brazing yielded
low void fractions
no deleterious secondary phases
expected require less time at lower temperature than conventional diffusion techniques
50 nm+ dia. NiNPs appear to have gone through phase change between 750 and 800 C
Currently evaluating shear strength of joints

Слайд 27Acknowledgments
This research is sponsored by the National Science Foundation CTS.


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