1. Multi-Property Design
of HV Dielectrics
Michel F. Fréchette
Hydro-Québec’s research institute (IREQ)
Varennes, Québec, Canada
Dielectrics 2011, Institute of Physics, University of Kent, April, UK

2. WHY THIS PRESENTATION?
It has been more than 10 years that the concept of NANODIELECTRICS (2001) have been introduced
What is the status?

3. WHY THIS PRESENTATION?
There was hope for NOVELTY in terms of properties
What is falsely expected ?

4. WHY THIS PRESENTATION?
In the concept there was the allusion to designing the material properties …
Where has it gone ?

5. content
Concept
Achievements
Other than interface
Multi-properties

6. Understanding and using
False effervescence OR
Effervescing pot
All is nano, nano is all and all you need is love
New or not
New look at
New interpretation
Gain in knowledge
Design at nanoscale

7. The definition
A “Nanodielectric” consists of a multi-component dielectric possessing nanostructures, the presence of which resulting into the change of one or several of its dielectric properties.
Nanodielectrics would be found in two material categories of interest: ceramics and polymers.

8. Included in the definition
Dielectrics at first
Presence of nanostructures
Nano scale processes
Intregration producing a macroscopic observable
Dependent on the dimension of the stress
NANODIELECTRICS

9. TOLERANCE .. slight changes in one property
We have been tolerant in regards of the results obtained
.. slight changes in one property
.. large improvement or change
.. still awaiting confirmed novelty

10. Elementals (nanocomposite)+ + +
Stress dimensions
Integrable

11. It depends .. Less nano Large nanometer sizes Agglomerated micron-size
Interface controlled
More nano
Less than 2 nanometers
Nano structuring
Relation BB – B
Less molecules
Improvement ..
Novelty/Design

12. Recipe ● The recipe is often different, dependent on case
● And various factors will affect the end results
Nanostructured microcomposite: Epoxy + micrometric quartz + nanoclay
PE-SiO2 sol-gel: Penetration of the deposit

13. Case 1 a - additives Schema listing some property roles of additives
These compounds added to polymers are essentially chemical in nature and one
characteristic that stands out is their adjunct may reach very small quantities,
e.g. 0.2w% Santonox as antioxidant

14. Case 1 b - polydispersity
Being chemical, the additive corresponds to a composite situation where polydispersity is very low. It is of molecular dimension, see for instance Fig. 1 where some Azo-compounds are depicted and were used to modify the conduction in PE.

15. Self-assembly
Generation of order in systems of components
The example shows an extremely thin layer of molecules (alkanethiols) self-assembled onto a metal surface to impart a water beading effect.

16. Case 2 a

17. Case 2 b - agglomeration
5% wt. SiO2
in HD PE

18. Case 3 - Influence of Chemical Structure and Solubility of Bisamide Additives on the Nucleation of Isotactic Polypropylene and the Improvement of Its Charge Storage Properties
A comparative study on the influence of chemical structure and solubility of a series of low-molecular-weight 1,4-phenylene−bisamides in isotactic polypropylene (i-PP) was conducted to explore their performance as nucleating agents and electret additives. The best β-nucleating efficiency was observed for the symmetrically substituted compounds, whereas the nucleation efficiency was substantially reduced in the presence of n-alkyl-substituents. The charge storage
behavior of i-PP was improved only
for the three
dicyclohexyl-substituted 1,4-phenylene
bisamides at concentrations of 100 ppm
and even below. For example, a film
comprising 10 ppm additive displayed
charge retention of 90% after an
accelerated aging
(annealing for 24 h at 90 °C).
Nils Mohmeyer et al. (2006)

19. Case 4 a A situation involving polyhedral
oligomeric silsesquioxane (POSS) cage structures chemically reacted
into the polymeric network.
These cage structures with
a particle diameter in the range of 1–3 nm can be functionalized to
provide chemical reactivity with various polymer systems.
Examples include octavinyl (R = vinyl group) incorporation for copolymerization
with PMMA, amine groups for incorporation
into polyamides and polyimides.
Hybrid Plastics

20. Case 4 b
The basic POSS® structure can be thought of as a cage of molecular silica comprised of 8 silicon atoms linked together with oxygen atoms. At each of the 8 corners is a substituent which can be just about any chemical group known in organic chemistry.
Hybrid-Plastics

21. Case 4 c
50nm
POSS® molecularly dissolved in PP, each black dot is a 1.5nm POSS® cage
Hybrid-Plastics

22. Case 4 d
Hybrid-Plastics

23. Case 4 b
IBM Research at Almaden

24. Scaling
Sol-Gel
POSS

25. Achievements to change morphology and related properties
Partial nanostructuration of polymer nanocomposites were found:
to change morphology and related properties
to improve partial-discharge resistance,
to suppress space charge formation and affect charge relaxation, and
to prolong the treeing lifetime
to open a way to tailoring/design

26. What’s lacking ?
The possibility to link (clearly and easily) the nano intervention to the macroscopic property
To make the materials with reproducibility and with successful quality control
To establish the stability and ageing of the nanocomposites

27. MORPHOLOGY
● Morphology ●

28. MORPHOLOGY – classi 1
Barium titanate is an oxide of barium and titanium with the chemical formula BaTiO3. It is a ferroelectric ceramic material, with a photorefractive effect and piezoelectric properties. It has five phases as a solid, listing from high temperature to low temperature: hexagonal, cubic, tetragonal, orthorhombic, and rhombohedral crystal structure. All of the structures exhibit the ferroelectric effect except cubic. Barioperovskite is a very rare natural analogue of BaTiO3, found as microinclusions in benitoite.

29. Lattice parameters of BaTiO3 as a function of temperature
Fraction of nano
The internal electric dipoles of a ferroelectric material are coupled to the material lattice so anything that changes the lattice will change the strength of the dipoles (in other words, a change in the spontaneous polarization). The change in the spontaneous polarization results in a change in the surface charge. This can cause current flow in the case of a ferroelectric capacitor even without the presence of an external voltage across the capacitor. Two stimuli that will change the lattice dimensions of a material are force and temperature. The generation of a surface charge in response to the application of an external stress to a material is called piezoelectricity.

30. MORPHOLOGY – classi 2
Dielectric strength as a function of film thickness for polyethylene, using the two types of electrodes. The solid lines represent the linear regressions.

31. Morphology – classi 2

32. HPN-20E-nucleated polyethylene resins display the highest crystallization temperature and the lowest isothermal crystallization half time achievable
EX1. Nucleation
Nucleation technologies fall into three categories: conventional, advanced, and hyper nucleation.

33. EX1. Crystal size and crystallinity

34. EX1. Nano and crystallinity

35. EX1. Crystallinity and conduction
A simple model for hole conduction may be proposed in which lamella regions of high conductance are inter-posed by amorphous regions of low conductance
Hole transport
Within the lamellae the chains will be largely free of disorder
and holes may be expected to be mobile in individual chains
along the c-axis.
Lewis and Llewyllin (2010)

36. EX2. Nanoclay in polymers

37. Nanostructured epoxy microcomposite
The two-step compatibilization creates a diffused ionic layer around the clay platelet, with additional ion clusters dispersed in the matrix.
The high energy clay surface causes solidification of the organic phase up to 6 nm thick
At about 3.6 wt% of clay the stacks with solidified polymer layer around them will occupy the full space and additional organoclay will remain non-dispersed.

38. PP+NanoClay Fuse et al. (2009)
Relative dielectric constant (a) and loss factor (b) as a function of
temperature observed at 10-2 and 104 Hz.

39. PP+NanoClay
Relation between PD charge and surface degradation depth induced by the PDs.
Fuse et al. (2009)

40. EX. 2 INTERPHASE  As concentration increases
S.Raetzke, J.Kindersberger – Role of Interphase on the Resistance to HV Arching, … IEEE DEIS Transactions, 2010

41. EX3. INTERPHASE It is estimated that
for a mere 1% volume fraction of 2 nm particles dispersed in a
matrix, as much as 63% of the volume could be occupied by
the interphase material.
Winey and Vaia (2007)

42. Interphase again A three component material with the
third component being a region around each nanoparticle
which we call the interphase
Illustrations of the interphase region
surrounding the filler particles in a composite system.

43. Interphase Epoxy-nanosilica
Measured (a) real and (b) imaginary parts of the complex permittivity of pure epoxy, nanocomposite (HN) for p v = 0.01, and numerically determined (a) real and (b) imaginary parts of the complex permittivity of pure epoxy, nanocomposite (HN) for p v = 0.01 interphase with i h = 5.5d.
Maity et al. 2010

44. Schematic representation of the interphase in iPP/SiO2 composites
Rui-Juan Zhou • Thomas Burkhart 2011

45. Effect on Breakdown
Weibull scale parameters η for DC breakdown strength for BN-ER as function
of filler size with 0 representing neat ER.
Andritsch et al. (2010)

46. Multi-properties
MULTI-PROPERTIES

47. EX 2-p Thermal conductivity scaled for several polymer cases.
Mesogen content
Thermal conductivity scaled for several polymer cases.
EPAN: a matrix of epoxy with a high load (about 76% wt.) of aluminum nitride

48. Okasaki (2010)
EX 2-p
Relationship of thermal conductivity and filler content
Breakdown strength

49. Micro performance
Micro-alumina 60 vol% filled epoxy composites of 0.2 mm thick was obtainable, and it was elucidated that its thermal conductivity is 4.3 W/m/K, its relative permittivity is 6.0, and its dielectric strength is 16 kV/mm.
Increased Vb by nano
Kozako (2010)

50. Multiphase extra-ordinary
Conductivity in unit of W/m K
Carbon nanotubes, metallic nanofibers, etc

51. Milling B4C Polyvinyl alcohol (PVA) coated nano-B4C powder
TEM morphologies of the nano-B4C/PVA composites milled at 700 rpm for 50min
Young Rang Uhm et al. (2010)

52. Functions separation Nanostructured epoxy
Doped for electrical conductivity
Cold spray or bonding
Multi-phases
Nano, sub-micro, micro
Breakdown and thermal

53. FUTURE Extra-ordinary additive or fillers (mastering)
34/36
FUTURE
Extra-ordinary additive or fillers
(mastering)
Tailoring 2 or more properties at the same time (multi-filler and separation of functions)
Higher-degree self-assembly nanodielectrics (BB and B)

54. CONCLUSION

55. CONCLUSION
Morphology is called to play a key role in designing nanodielectrics
Often nanometric … if so mesoscopic physics in essence

56. THANK YOU !