scholarly journals Processing and Characterization of High Porosity Aerogel Films

1994 ◽  
Vol 371 ◽  
Author(s):  
Lawrence W. Hrubesh ◽  
John F. Poco
Keyword(s):  
Dielectric Constant ◽  
Molecular Transport ◽  
Solid Material ◽  
Porous Solids ◽  
High Porosity ◽  
Transport Mechanisms ◽  
Mechanical And Electrical Properties ◽  
Highly Porous ◽  
Aerogel Films

AbstractAerogels are highly porous solids having unique morphology among materials because both the pores and particles making up the material have sizes less than wavelengths of visible light. Such a unique morphology modifies the normal molecular transport mechanisms within the material, resulting in exceptional thermal, acoustical, mechanical, and electrical properties. For example, aerogels have the lowest measured thermal conductivity and dielectric constant for any solid material. Special methods are required to make aerogel films with high porosity. In this paper, we discuss the special conditions needed to fabricate aerogel films having porosities greater than 75% and we describe methods of processing inorganic aerogel films having controllable thicknesses in the range 0.5 to 200 micrometers. We report methods and results of characterizing the films including thickness, refractive index, density (porosity), and dielectric constant. We also discuss results of metallization and patterning on the aerogel films for applications involving microminiature electronics and thermal detectors.

Fabrication and Characterization of Spin-On Silica Xerogel Films

1998 ◽  
Vol 511 ◽  
Author(s):  
S. Nitta ◽  
A. Jain ◽  
V. Pisupatti ◽  
W. N. Gill ◽  
P. C. Wayner ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Convective Diffusion ◽  
Ambient Pressure ◽  
Silica Xerogel ◽  
High Porosity ◽  
Thermal Oxide ◽  
Fabrication And Characterization ◽  
Xerogel Films

ABSTRACTXerogel films of high porosity were fabricated using an ambient pressure technique. The same porosity can be obtained with different microstructures by varying the aging time of the films. The dielectric constant of these films as a function of porosity at 1 MHz follows correlations originally developed for bulk aerogels. Diffusion of copper is orders of magnitude faster in these xerogels than in the corresponding thermal oxide. An activation energy of 0.9 eV was estimated based on a convective diffusion model.

scholarly journals Silica Aerogel: An Intrinsically Low Dielectric Constant Material

1995 ◽  
Vol 381 ◽  
Author(s):  
Lawrence W. Hrubesh
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Solid Material ◽  
Dielectric Strength ◽  
Silica Aerogels ◽  
Dielectric Constants ◽  
Porous Solids ◽  
Direct Result ◽  
Low Dielectric ◽  
Normal Transport

AbstractSilica aerogels are highly porous solids having unique morphologies in which both the pores and particles have sizes less than the wavelength of visible light. This fine nanostructure modifies the normal transport mechanisms within aerogels and endows them with a variety of exceptional physical properties. For example, aerogels have the lowest measured thermal conductivity and dielectric constant for any solid material. The intrinsically low dielectric properties of silica aerogels are the direct result of the extremely high achievable porosities, which are controllable over a range from 75% to more than 99.8%, and which result in measured dielectric constants from 2.0 to less than 1.01. This paper discusses the synthesis of silica aerogels, processing them as thin films, and characterizing their dielectric properties. Existing data and other physical characteristics of bulk aerogels (e.g., thermal stablity, thermal expansion, moisture adsorption, modulus, dielectric strength, etc.), which are useful for evaluating them as potential dielectrics for microelectronics, are also given.

Dielectric properties of aerogels

1993 ◽  
Vol 8 (7) ◽  
pp. 1736-1741 ◽  
Author(s):  
L.W. Hrubesh ◽  
L.E. Keene ◽  
V.R. Latorre
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bulk Material ◽  
Solid Material ◽  
Adsorbed Water ◽  
Dielectric Behavior ◽  
Dielectric Constants ◽  
High Porosity ◽  
Microwave Frequencies ◽  
Low Dielectric

We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 K using microwave frequencies (2, 10, and 18–40 GHz) for bulk SiO2-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel densities from 10 to 500 kg/m3. For the same range of densities, the measured loss tangents vary linearly between values of 2 × 10−4 and 7 × 10−2. The observed linearity of the dielectric properties with density in aerogels at microwave frequencies shows that their dielectric behavior is more gas-like than solid-like. The dielectric properties of aerogels are shown to be significantly affected by the adsorbed water internal to the bulk material. For example, water accounts for 70% of the dielectric constant and 70% of the loss at microwave frequencies for silica aerogels. Because of their very high porosity, even with the water content, the aerogels are among the few materials exhibiting such low dielectric properties. Our measurements show that aerogels with greater than 99% porosity have dielectric constants less than 1.03; these are the lowest values ever reported for a bulk solid material.

Synthesis and Characterization of Poly(2,5-benzimidazole) (ABPBI) Grafted Carbon Nanotubes

2009 ◽  
Vol 1240 ◽  
Author(s):  
Ji-Ye Kang ◽  
Su-Mi Eo ◽  
Loon-Seng Tan ◽  
Jong-Beom Baek
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Interfacial Adhesion ◽  
Synthesis And Characterization ◽  
Acylation Reaction ◽  
Single Walled Carbon Nanotube ◽  
Mechanical And Electrical Properties ◽  
Multi Walled Carbon Nanotube

AbstractSingle-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) were functionalized with 3,4-diaminobenzoic acid via “direct” Friedel-Crafts acylation reaction in PPA/P2O5 to afford ortho-diamino-functionalized SWCNT (DIF-SWCNT) and MWCNT (DIF-MWCNT). The resultant DIF-SWCNT and DIF-MWCNT showed improved solubility and dispersibility. To improve interfacial adhesion between CNT and polymer matrix, the grafting of ABPBI onto the surface of DIF-SWCNT (10 wt%) or DIF-MWCNT (10 wt%) was conducted by simple in-situ polymerization of AB monomer, 3,4-diaminobenzoic acid dihydrochloride, in PPA. The resultant ABPBI-g-MWCNT and ABPBI-g-SWCNT showed improved the mechanical and electrical properties.

Dielectric Constant and Loss Tangent Characterization of Thin High-K Dielectrics Using Corner-to-Corner Plane Probing

2006 ◽  
Author(s):  
A. Ege Engin ◽  
Abdemanaf Tambawala ◽  
Madhavan Swaminathan ◽  
Swapan Bhattacharya ◽  
Pranabes Pramanik ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Loss Tangent ◽  
Dielectric Constant And Loss ◽  
High K

Dielectric Characterization of Polyceram Films

1990 ◽  
Vol 180 ◽  
Author(s):  
G. Teowee ◽  
J.M. Boulton ◽  
H.H. Fox ◽  
A. Koussa ◽  
T. Gudgel ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Polyethylene Oxide ◽  
Dielectric Materials ◽  
Inorganic Materials ◽  
Functionalized Polymers ◽  
Multifunctional Materials ◽  
Dielectric Characterization ◽  
Silicon Alkoxides ◽  
Tan Δ

ABSTRACTPolycerams are an emergent class of hybrid, multifunctional materials which combine the properties of organic and inorganic materials. Films have been prepared from silicon alkoxides and reactive, functionalized polymers such as triethoxysilyl modified polybutadiene (MPBD), (N-triethoxysilylpropyl)O polyethylene oxide urethane (MPEOU) and trimethoxysilylpropyl substituted polyethyleneimine (MPEI). Characterization of dielectric constant and tan δ of the films has been carried out over a range of frequency from 500 Hz to 100 kHz; and the results are used to consider the potential of Polycerams as dielectric materials.

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