scholarly journals Effects of polymorphic form and particle size of SiO2 fillers on the properties of SiO2–PEEK composites

2021 ◽  
Vol 11 (04) ◽  
pp. 2150021
Author(s):  
Peng Jie Xue ◽  
Shi Lin Liu ◽  
Jian Jiang Bian
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Expansion ◽  
Dielectric Loss ◽  
Mechanical Strength ◽  
Polymorphic Form ◽  
Fused Silica ◽  
High Frequencies ◽  
Silica Fillers ◽  
Filled Composite

The effects of polymorphic form and particle size of SiO2 fillers on the dielectric, mechanical and thermal properties of SiO2–Polyetheretherketone (SiO2–PEEK) composites were investigated in this paper. Strong low frequency (<10Hz) Debye-like dielectric dispersions could be observed for all samples. The dielectric permittivity at high frequencies of the composite exhibits little morphology or particle size-sensitive characteristics of the SiO2 fillers. All the composites obtained in this case demonstrate the dielectric permittivities of [Formula: see text] at high frequencies. The crystalline [Formula: see text]-cristobalite filled composite exhibits lower dielectric loss and mechanical strength, but larger thermal expansion coefficient and thermal conductivity, compared with the similar particle sized amorphous SiO2 filled one. The crystalline [Formula: see text]-quartz filled composite demonstrates the lowest mechanical strength and highest dielectric loss. An increase in particle size of the spherical fused silica fillers decreases the dielectric loss, while increases the thermal conductivity of the composite. The flexural strength of the composite reaches the maximum value of 113 MPa when the particle size of spherical SiO2 filler is [Formula: see text]m. Particle packing by combining optimal amounts of differently sized spherical fused silica fillers leads to a substantial improvement of mechanical strength (153MPa) coupled with reasonable dielectric and thermal properties due to the synergic effect (dielectric permittivity ([Formula: see text] = 3.35, dielectric loss (tan[Formula: see text] @10 GHz, thermal conductivity ([Formula: see text] = 0.74 W/m*k ([Formula: see text]C), coefficient of thermal expansion ([Formula: see text]C and relative density ([Formula: see text]) = 99.72%).

scholarly journals Opening Material as the Possibility of Elimination Veining in Foundries

2016 ◽  
Vol 16 (3) ◽  
pp. 157-161 ◽  
Author(s):  
M. Hrubovčáková ◽  
I. Vasková ◽  
M. Benková ◽  
M. Conev
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Expansion ◽  
Cast Iron ◽  
Granular Material ◽  
Surface Defects ◽  
Silica Sand ◽  
Iron Castings ◽  
Thermal Dilatation

Abstract The main bulk density representation in the molding material is opening material, refractory granular material with a particle size of 0.02 mm. It forms a shell molds and cores, and therefore in addition to activating the surface of the grain is one of the most important features angularity and particle size of grains. These last two features specify the porosity and therefore the permeability of the mixture, and thermal dilatation of tension from braking dilation, the thermal conductivity of the mixture and even largely affect the strength of molds and cores, and thus the surface quality of castings. [1] Today foundries, which use the cast iron for produce of casts, are struggling with surface defects on the casts. One of these defects are veining. They can be eliminated in several ways. Veining are foundry defects, which arise as a result of tensions generated at the interface of the mold and metal. This tension also arises due to abrupt thermal expansion of silica sand and is therefore in the development of veining on the surface of casts deal primarily influences and characteristics of the filler material – opening material in the production of iron castings.

Preparation and Characterization of Fused Silica Micro-Powders and Ceramics

2011 ◽  
Vol 412 ◽  
pp. 129-132 ◽  
Author(s):  
Jin Ye Niu ◽  
Zhi Wei Chen ◽  
Liu Feng ◽  
Zheng Min Li ◽  
Min Tan
Keyword(s):  
Particle Size ◽  
Thermal Expansion ◽  
Lactic Acid ◽  
Milling Time ◽  
Bending Strength ◽  
Slip Casting ◽  
Volume Density ◽  
Fused Silica ◽  
Lactic Acid Content

Fused silica micro-powders with D50of 1.8μm were firstly prepared by ball milling. Effects of milling time on particle size distribution and microstructures of the powders were discussed. Then, the green compacts with volume density of 1.86g/cm3was obtained by slip casting with lactic acid as dispersant. Effects of lactic acid content on apparent viscosity of the slurry, thickness and density of the green compacts were investigated. Finally, fused silica ceramics with thermal expansion coefficient of 0.56∙10-6/°C, bending strength of 64MPa and volume density of 1.94g/cm3were prepared.

scholarly journals The Effects of Filler Shape, Type, and Size on the Properties of Encapsulation Molding Components

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 98
Author(s):  
Shouyen Chao ◽  
Yowching Liaw ◽  
Jung-Hua Chou
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Coefficient Of Thermal Expansion ◽  
Filler Particle ◽  
Fused Silica ◽  
Molding Compound ◽  
Spherical Silica ◽  
Filler Particle Size ◽  
Size Type ◽  
Better Than

Fillers are essential in the encapsulation molding compound. For three fillers of crystal, spherical, and fused silica, the effects of their size, type, and shape on the viscosity, flow spiral length, thermal conductivity, and coefficient of thermal expansion (CTE) of the compound were explored in this study. The results show that fillers with a larger particle size have a smaller viscosity and flow better; spherical fillers are better than the polygonal ones in this respect. In contrast, both thermal conductivity and CTE increase as the filler particle size increases; the values of these two properties of crystal silica are about twice those of fused silica; the thermal conductivity of polygonal silica is larger than that of spherical silica. On the other hand, the dependence of CTE on the filler shape is insignificant, but is significant to the filler type. The degree of curing of the compound with polygonal silica is also higher than that with either spherical or crystal silica. Namely, curing is affected by both filler type and shape, and can be tuned accordingly to suit specific needs.

Effects of Particle Size on Microstructures and Properties of Si/Al Composites

2013 ◽  
Vol 873 ◽  
pp. 361-365 ◽  
Author(s):  
Wei Chen Zhai ◽  
Zhao Hui Zhang ◽  
Fu Chi Wang ◽  
Shu Kui Li
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Expansion ◽  
Flexural Strength ◽  
Spark Plasma Sintering ◽  
Thermal Conductivity Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
High Strength ◽  
Plasma Sintering ◽  
Spark Plasma

Si/Al composites with different Si particle sizes were fabricated using spark plasma sintering process for electronic packaging. The density, thermal conductivity, coefficient of thermal expansion and flexural strength of the composites were investigated. Effect of Si particle size on structure and properties of the Si/Al composites were studied. The results showed that the Si/Al composites synthesized by spark plasma sintering were composed of Si and Al. Al was uniformly distributed among the Si phase, leading to a high thermal conductivity (>120 W/m·k). The relative density of the Si/Al composites decreased with increasing Si particle size. Small Si particle size produced small grains, leading to a low coefficient of thermal expansion and a high strength. There is an optimal matching among the thermal conductivity, coefficient of thermal expansion and flexural strength when the Si particle size was 44 um.

Computational Design and Development of Alumina-Nickel Droplet Composites

2016 ◽  
Author(s):  
S. Sohail Akhtar ◽  
A. F. M. Arif ◽  
M. U. Siddiqui ◽  
Kabeer Raza ◽  
L. Taiwo Kareem ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Volume Fraction ◽  
Matrix Material ◽  
Microstructural Analysis ◽  
Computational Design ◽  
Minimum Size

Computational design for property management of composite materials offers a cost sensitive alternate approach in order to understand the mechanisms involved in the thermal and structural behavior of material under various combinations of inclusions and matrix material. The present study is concerned with analyzing the elasto-plastic and thermal behavior of Al2O3-Ni droplet composites using a mean field homogenization and effective medium approximation (EMA) using an in-house code. Our material design approach relies on a method for predicting potential optimum thermal and structural properties for Al2O3-Ni composites by considering the effect of inclusion orientation, volume, size, thermal interface resistance, percolation and porosity. The primary goal for designing such alumina-based composites is to have enhanced thermal conductivity for effective heat dissipation and spreading capabilities. At the same time, other functional properties like thermal expansion coefficient, elastic modulus, and electrical resistivity have to be maintained or enhanced. The optimum volume fraction was found to occur between 15 and 20 vol. %Ni while the average nickel particle size of 5 μm was found a minimum size that will enhance the thermal conductivity. The Young’s modulus was found decreasing as the volume fraction of nickel increases, which would result in enhanced fracture toughness. Electrical conductivity was found to be greatly affected by the percolation phenomenon in the designed range of volume fraction minimum particle size. As a validation, Al2O3 composites with 10% and 15% volume fraction Ni and droplet size of 18 μm are developed using spark Plasma Sintering process. Thermal conductivity and thermal expansion coefficient of the samples are measured to complement the computational design. Microstructural analysis of the sintered samples was also studied using optical microscope to study the morphology of the developed samples. It was found that the present computational design tool was accurate enough in predicting the desired properties of Al2O3-Ni composites.

The Effects of Silica Fillers on the Properties of Encapsulation Molding Compounds

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Yowching Liaw ◽  
Jung-Hua Chou
Keyword(s):  
Thermal Conductivity ◽  
Flexural Strength ◽  
Water Absorption ◽  
Absorption Rate ◽  
Coefficient Of Thermal Expansion ◽  
Industrial Applications ◽  
Fused Silica ◽  
Molding Compounds ◽  
Water Absorption Rate ◽  
Silica Fillers

Encapsulation molding compounds (EMCs) are commonly used to protect integrated circuit (IC) chips. Their composition always contains fillers of a large amount (about 70%) and will affect the properties of the compounds. Thus, in order to clarify the filler effects, in this study, three types of silica fillers including crystal silica, edgeless silica, and fused silica were studied experimentally to explore their effects on the compounds. The results show that all of the flow spiral length, glass transition temperature (Tg), coefficient of thermal expansion (CTE), and water absorption rate of the encapsulation molding compounds decrease as the filler amount increases, irrespective of the filler type. In contrast, both thermal conductivity and flexural strength of the compounds increase as the filler amount increases, but also irrespective of the filler type. For the three fillers, the edgeless silica filler has the advantage of a large flow spiral length and can be molded better. It also has a larger thermal conductivity, larger flexural strength, and lower water absorption rate. Hence, for low stress industrial applications, the edgeless silica should be adopted as the filler of the encapsulation molding compounds.

Effects of Particle Size on the Thermal Physical Properties of SiCp/Al Composites

2007 ◽  
Vol 351 ◽  
pp. 131-134 ◽  
Author(s):  
Lin Geng ◽  
Yi Wu Yan
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Expansion ◽  
Room Temperature ◽  
Thermal Loading ◽  
Thermal Residual Stresses ◽  
Powder Metallurgy Process ◽  
The Difference ◽  
Metallurgy Process ◽  
Thermal Physical Properties

The coefficients of thermal expansion (CTEs) of the 20 vol% SiCp/Al composites fabricated by powder metallurgy process were measured and examined from room temperature to 450°C The SiC particles are in three nominal sizes 5μm, 20μm and 56μm. The CTEs of the SiCp/Al composites were shown to be apparently dependent on the particle size. That the larger particle size, the higher CTEs of the composites, is thought to be due to the difference in original thermal residual stresses and matrix plasticity during thermal loading. The thermal conductivity of the composites also increases with particle size increasing.

scholarly journals Properties of Porous AlN Multilayered Ceramic Sandwich Substrates

2002 ◽  
Vol 17 (5) ◽  
pp. 1061-1068 ◽  
Author(s):  
F. Y. C. Boey ◽  
A. I. Y. Tok ◽  
Y. Long ◽  
H. Y. Yeong
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Thermal Expansion ◽  
Integrated Circuits ◽  
Mechanical Strength ◽  
Tape Casting ◽  
Boundary Effects ◽  
Dielectric Substrates ◽  
Interface Cracking ◽  
Tape Cast

The development of denser and higher powered integrated circuits has led to a corresponding demand on the performance of dielectric substrates. This paper reports on the fabrication and properties of an AlN multilayered sandwich substrate comprising porous tape-cast layers sandwiched between nonporous layers. Tapes were produced by nonaqueous tape casting, with the porous tapes produced using polymer microspheres as sacrificial molds. Starting from initially Al2O3-rich tapes, the multilayered sandwich substrates were reaction sintered to produce AlN substrates. No interface cracking or delamination was observed in the substrates as a result of the processing. The added porosity resulted in a decrease in the substrate dielectric constant in correspondence to porosity volume. Mechanical strength of the sandwich substrates was improved over that of nonsandwich porous substrates, while substrates having noninterconnected pores showing higher mechanical strength than substrates with connected pores. Substrates with more than 2% porosity showed porosity-dependent thermal conductivity values, while thermal conductivity of substrates with less than 2% porosity was dependent on grain boundary effects. Thermal expansion coefficient of the substrates was unaffected by porosity levels.

Thermal Conductivity of Fly Ash Cenospheres for Variable Particle Size Ranges

2016 ◽  
Vol 4 (2) ◽  
pp. 19
Author(s):  
MENEZES CRAIG ◽  
RATHOD AJIT P ◽  
WASEWAR KAILAS L. ◽  
◽  
◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Fly Ash ◽  
Fly Ash Cenospheres
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