Stable, highly concentrated suspensions for electronic and ceramic materials applications

1991 ◽  
Vol 6 (5) ◽  
pp. 1082-1093 ◽  
Author(s):  
I. Sushumna ◽  
R.K. Gupta ◽  
E. Ruckenstein

Highly concentrated solid-in-liquid suspensions find applications in a number of areas such as electronics, ceramics, paints, coatings, etc. Highly loaded, stable suspensions which exhibit desirable rheological characteristics (moderate viscosity, shear thinning behavior, thixotropy, and a small yield stress, for example), and which have high thermal or electrical conductivities are frequently sought after. We describe here some techniques which can be used to obtain such highly concentrated suspensions. These involve employing mixed size grades of particles and effective dispersants. For thermal paste applications, for example, compliant pastes of up to 78 vol. % solids with thermal conductivity values as high as 6 W/mK (hence, a few times greater than the values reported previously by others), low electrical conductivity, and moderate viscosity have been prepared by mixing different particle size grades of materials such as Al2O3, SiC, AlN, Al, and diamond. Effective dispersants, both commercial as well as those synthesized in our laboratory as novel variations of previously known molecular architectures, have been used to facilitate the achievement of these very high loading and stable suspensions.

Author(s):  
Yao Yao ◽  
Jared Fry ◽  
Morris Fine ◽  
Leon Keer

Due to the limitation of available experimental data for thermal conductivity of lead free solder and Intermetallic Compound (IMC) materials, the Wiedemann-Franz-Lorenz (WFL) relation is presented in this paper as a possible solution to predict thermal conductivity with known electrical conductivity. The method is based upon the fact that heat and electrical transport both involve the free electrons. The thermal and electrical conductivities of Cu, Ni, Sn, and different Sn rich lead free solder and IMC materials are studied by employing the WFL relation. Generally, the analysis to the experimental data shows that the WFL relation is obeyed in both solder alloy and IMC materials especially matches close to the relation for Sn, with a positive deviation from the theoretical Lorenz number. Thus, with the available electrical conductivity data, the thermal conductivity of solder and IMC materials can be obtained based on the proper WFL relation, vice versa. With the reduction of size of electronic devices and solder interconnects, it has been observed experimentally that solders fail by crack nucleation and propagation near the interface of IMC and bulk solder. A coupled thermal-electrical finite element analysis is performed to study the behavior of lead free solder/IMC interconnects under different electrical current densities. The joule heating, temperature concentration and electrical current concentration effects with a crack propagating near the interface of solder and IMC are investigated numerically. Solder and IMC material properties predicted using the WFL relation are adopted in the computational model. The effects of different thermal and electrical conductivities of solder and IMC materials on interfacial crack tip temperature are analyzed in the present study. By applying the WFL relation, the amount of experiments required to determine the material properties for different lead free solder/IMC interconnects can be significantly reduced, which can lead to pronounced saving of time and cost.


2011 ◽  
Vol 484 ◽  
pp. 57-60
Author(s):  
Takafumi Kusunose ◽  
Tohru Sekino ◽  
Koiichi Niihara

The electrically conductive AlN with high thermal conductivity were successfully fabricated by sintering AlN with a composite additive of 1wt.% Y2O3 and 4wt.% CeO2 in carbon-reduced atmosphere at over 1600 °C. The sudden increase in electrical conductivity is thought to be caused by transition of grain boundary phase from rare-earth oxide to rare-earth oxycarbide. Their electrical conductivities and thermal conductivities increased with increasing sintering temperature. Additionally, sintering temperature influenced the resultant microstructures.


2016 ◽  
Vol 881 ◽  
pp. 117-122
Author(s):  
Flavia dos Reis Gonçalves ◽  
Daniel Thomazini ◽  
Maria Virginia Gelfuso

In this work, CaCuxTiyO12 ceramics (2.7 ≤ x ≤ 3.3 and 3.25 ≤ y ≤ 4.75), related to excess and deficiency of CuO-TiO2 eutectic phase have been synthesized by coprecipitation method. The crystalline phases in the ceramics were identified by X-ray diffraction patterns, and the pellets have mainly presented CCTO and also exhibited CuO, TiO2 and CaTiO3 as secondary phases. The thermal conductivity of the ceramics was determined using the laser flash method in the temperature range of 300-1000 K. It was observed a decrement in thermal conductivity values as the amount of the eutectic phase decreased. The electrical DC conductivity has been measured by the two-probe method from 300-1000 K and it has been noted that both grain size and amount of eutectic phase influenced the electrical conductivity results.


It is shown that single crystals of gallium can be produced with considerable ease, and that these crystals show greater anisotropism in their conducting properties than those of other metals. At normal temperatures the electrical conductivities for the three axial directions c : a : b are in the ratio 1:3.2:7, and the expansion coefficients are in the ratio 1:0.7:1.9. Results are given showing that these ratios persist down to —180° C with relatively little change. From preliminary observations at normal temperature it seems that the thermal conductivity varies much as does the electrical conductivity and that the mechanical properties will also prove to be markedly anisotropic.


1999 ◽  
Vol 14 (5) ◽  
pp. 1949-1958 ◽  
Author(s):  
E. M. Carrillo-Heian ◽  
O. A. Graeve ◽  
A. Feng ◽  
J. A. Faghih ◽  
Z. A. Munir

The role of the electrical conductivity of the product and of the thermal conductivities of the reactants on self-propagating combustion synthesis was investigated through modeling studies. Similar studies were made to investigate the role of the relative density of the reactants. The effect of an imposed electric field on the results of the modeling analysis was considered. For any given imposed field, the wave velocity exhibited a maximum at a given normalized thermal conductivity, electrical conductivity, and relative density. The results are discussed in terms of the Joule heat contribution of the field and are compared with experimental observations.


2006 ◽  
Vol 317-318 ◽  
pp. 491-494 ◽  
Author(s):  
Jae Chun Lee ◽  
Jun Suh Yu ◽  
Jae Hoon Sung ◽  
Sung Park ◽  
Sung Chul Choi

Porous ceramic fiber composites were coated with pyrolytic carbon by the decomposition of infiltrated phenolic resin in a nitrogen atmosphere at 800. The amount of carbon coating was varied to tailor the electrical conductivity of the carbon-coated composites. The electrical and thermal conductivity of the composites were measured at room temperature using a two-point method and a hot-wire one, respectively. Up to 30 wt% pyrolytic carbon, the electrical conductivity σ shows linearly increasing tendency and is fitted by the effective conductivity according to the parallel rule of a mixture σeff = ΣΧi ·σi with an effective conductivity of pyrolytic carbon σc= 0.42 S/cm. The thermal conductivity of the coated composites is in the range 0.05-0.08 W/mK and increases with carbon content.


The anomalous physical properties of bismuth, particularly as regards the reduction of the thermal and electrical conductivities in magnetic fields, have claimed the attention of a number of workers in the past. Most of the published data refers to the electrical conductivity, owing, no doubt, to the greater ease of measurement; and but little reliable work appears to have been done on the thermal conductivity, at any rate in the case of single crystals. Lounds (1902) carried out thermal-conductivity measurements employing magnetic fields up to about 5000 gauss, but the accuracy of his results was prescribed by the limitations of the method and the smallness of his crystals. Kapitza (1928) undertook an extensive investigation on the electrical conductivity of single crystals using very intense momentary fields. Banta (1932) published thermal-conductivity values using fields up to 8000 gauss, while more recently de Haas and Capel (1934) have made thermal measurements, in the absence of a field, at liquid-air and liquid-hydrogen temperatures. The results of a preliminary investigation (Kaye and Higgins 1929 a ) at the National Physical Laboratory on the change in thermal conductivity of bismuth single crystals in transverse magnetic fields were published in 1929. In this work, specimens, which were cut in the form of disks 25 mm. in diameter and 2 mm. thick from a large crystal grown by Bridgman’s method (1925), were tested in a “plate” type of apparatus, field strengths up to 11,000 gauss being employed in a 38 mm. air gap.


MRS Bulletin ◽  
2003 ◽  
Vol 28 (11) ◽  
pp. 815-818 ◽  
Author(s):  
Brian Derby ◽  
Nuno Reis

AbstractInkjet printing is an attractive method for patterning and fabricating objects directly from design or image files without the need for masks, patterns, or dies. In order to achieve this with metals or ceramics, it is often necessary to print them as highly concentrated suspensions of powders in liquids. Such liquid suspensions must have physical properties appropriate to the inkjet delivery mechanism. These properties are presented using a nondimensional formalism to illustrate the requirements for both drop formation and spreading on impact. Further critical issues relevant to inkjet printing of particulate suspensions are discussed and illustrated with experiments on a model alumina-containing colloidal suspension.


Alloy Digest ◽  
2005 ◽  
Vol 54 (12) ◽  

Abstract Wieland K-88 is a copper alloy with very high electrical and thermal conductivity, good strength, and excellent stress relaxation resistance at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CU-738. Producer or source: Wieland Metals Inc.


Alloy Digest ◽  
1977 ◽  
Vol 26 (5) ◽  

Abstract Copper Alloy No. 815 is an age-hardenable cast copper-chromium alloy. It is characterized by high electrical and thermal conductivities combined with medium hardness and strength in the age-hardened condition. It is used for components requiring high electrical conductivity or high thermal conductivity. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as casting, heat treating, machining, and joining. Filing Code: Cu-332. Producer or source: Copper alloy foundries.


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