Download unit - i principles of dynamics (9)

Reg.No:
SNS College of Technology, Coimbatore-35.
(Autonomous)
B.E/B.Tech- Internal Assessment -III
Academic Year 2016-2017(Even)
EighthSemester
Mechanical Engineering
GE402 NANO TECHNOLOGY
MaximumMarks: 50
Answer All Questions
PART - A (5x 1 = 5Marks)
B
Time: 11/2 Hours
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2.
3.
4.
5.
Electrons
Very High Toxic
100000x
Fullerene
50nm
PART - B (5 x 2 = 10 Marks)
6. Define Nano machining.
Nanometric machining is more concerned with the precision rather than the characteristic size of the
product. So nanometric machining is defined as the material removal process in which the
dimensional accuracy of a product can be achieved is 100 nm or better, even towards 1 nm level.
7. List out the types of Top up Nano fabrication techniques.
 Sol gel Process
 CVD
 PVD
8. Distinguish between Contact mode and Tapping mode in SPM.
• Contact Mode: direct physical contact with the sample
•Non-contact Mode:
Tip oscillating at constant distance above sample surface
• Tapping mode:
Intermittent contact, less damaging
9. Recall the Quantum Materials in Nano Technology.
In many of today's most interesting materials strong interactions prevail upon the magnetic
moments, the electrons and the underlying crystal structure, often forming strong links between
these different aspects of the system. Such materials can exhibit exciting physical phenomena
whose description requires new quantum mechanical models to be developed.
10. Write the importance of Scanning Tunneling Microscope.
STM tip should be conducting (metals, like Pt);
•STM plays with the very top (outermost) atom at the tip and the nearest atom on sample; so the
whole tip is not necessarily very sharp in shape, different from the case of AFM, where spatial
“contact” is necessary and crucial for feedback.
PART – C (14+14+7=35 Marks)
11. (a) Describe briefly with neat sketch on LIGA Technology.
LIGA is a hybrid fabrication technique
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-ray lithography using synchrotron radiation
(b) Explain with neat sketch of Molecular Manufacturing Technique.
Molecular manufacturing is a branch of nanotechnology that involves the use of nanoscale
(extremely small) Machine tools and non-biological processes to build structures, devices
and systems at the molecular level. Nanoscale objects have dimensions on the order of a
few nanometers (nm) or less, where 1 nm is equal to a billionth of a meter (10–9 m). Molecular
manufacturing is distinct from nanoscale technology, another major branch of nanotechnology
in which standard size tools are used to manufacture simple nanoscale structures and
devices. Two technological capabilities are key to economically viable molecular
manufacturing, and are essential to reap the tremendous benefits and the full potential of
manufacturing in the 21st century. The first key is the ability to fabricate physical structures
with molecular precision. The second key is the ability to fabricate massive quantities of
molecularly precise structures, or to assemble larger objects from vast numbers of
molecularly precise smaller objects. We will need a theoretical and experimental program
to develop molecularly precise fabrication of diamondoid structures using machine-phase
nanotechnology. We will also need a theoretical and experimental program to develop
methods for massive parallelization of these newly developed machine-phase techniques
for molecularly precise fabrication. This combined effort will result in the full realization of
the tremendous potential for 21st century manufacturing
12. (A) Illuminate with neat sketch of Scanning Probe Microscopy.
SPM provides very high resolution images of various sample properties.
All of these microscopes work by measuring a local property - such as height, optical absorption,
or magnetism - with a probe or "tip“ placed very close to the sample.
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The small probe-sample separation (on the order of the instrument's resolution) makes it possible to
take measurements over a small area. To acquire an image the microscope raster-scans the probe
over the sample
while measuring the local property in question. The resulting image resembles an image on a
television screen in that both consist of many rows or lines of information placed one above the
other. Unlike traditional microscopes, scanned-probe systems do not use lenses, so the size of the
probe rather than diffraction effects generally limit their resolution.
(b) Illuminate with neat sketch of Electrostatic force mode (EFM) & Magnetic force mode
(MFM) in Scanning Probe Microscopy
Electric force microscopy
In EFM the electric tip-sample interaction is used to collect information on the sample properties.
Let us consider a system consisting of a probe, made of cantilever and tip with conducting coating,
and a sample made of a thin layer of a material on a well conducting substrate.
Magnetic force microscopy
Magnetic force microscope (MFM) has been invented by Y. Martin and
H.K.Wickramasinghe in 1987 for studying local magnetic properties. This device is an atomic force
microscope using a tip covered by a layer of ferromagnetic material with specific M( r ) r r
magnetization.
13. Explain any one techniques in Top down Nano Fabrication methods
Ball Milling
Mechanical attrition is a typical example of ‘top down’ method of synthesis of nanomaterials, where
the material is prepared not by cluster assembly but by thestructural decomposition of coarser-grained
structures as the result of severe plastic deformation. This has become a popular method to make
nanocrystalline materials because of its simplicity, the relatively inexpensive equipment needed, and
the applicability to essentially the synthesis of all classes of materials. The major advantage often
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quoted is the possibility for easily scaling up to tonnage quantities of material for various applications.
Similarly, the serious problems that are usually cited are;
1. contamination from milling media and/or atmosphere, and
2. to consolidate the powder product without coarsening the nanocrystallinemicrostructure.
(😎 Discuss on Nano Identation.
Nanoindentation can be used to determine the hardness and elastic modulus of
materials, including layers and coatings <100 nm thick. Nanoscratch tests can
be performed to measure lateral forces during the scratch process. The direct
measurment of friction between fibre and matrix in fibre-reinforced composites
can also be measured by performing a push-out test.
1. Nanoindentation is a powerful technique used for assessing mechanical properties
at nano/micro-scale.
2. It is used for obtaining material parameters like elastic modulus, hardness, plastic
or viscous parameters from experimental readings of indenter load and depth of
penetration.
3. Forces involved are usually in the mili or micronewton range and the depth in the
order of nanometers.
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