Hybrid-particulate composites

Dib Di Berardino, M. F., Pearson, R. A. Fracmre behavior of epoxy-based, hybrid particulate composites. Mater. Res. Soc. Symp. Proc. 515 (1998) 239-244. 

Kim N H and Kim H S, Toughening in hybrid particulate composites, Fifth international conference on composite science and technology, American University of Sharjah, United Arab Emirates, Feb 1-3, 2005, pp.149-154. 

Kinloch AJ, Maxwell DL et al (1985) The fracture of hybrid-particulate composites. J Mater Sci 20 4169... 

Source Characterization. All receptor models, even the source/receptor hybrids, require input data about the particulate matter sources. The multivariate models, which can conceivably be used to better estimate source compositions, require an initial knowledge of the chemical species associations in sources. 

In this study we have employed the simultaneous collection of atmospheric particles and gases followed by multielement analysis as an approach for the determination of source-receptor relationships. A number of particulate tracer elements have previously been linked to sources (e.g., V to identify oil-fired power plant emissions, Na for marine aerosols, and Pb for motor vehicle contribution). Receptor methods commonly used to assess the interregional impact of such emissions include chemical mass balances (CMBs) and factor analysis (FA), the latter often including wind trajectories. With CMBs, source-strengths are determined (1) from the relative concentrations of marker elements measured at emission sources. When enough sample analyses are available, correlation calculations from FA and knowledge of source-emission compositions may identify groups of species from a common source type and identify potential marker elements. The source composition patterns are not necessary as the elemental concentrations in each sample are normalized to the mean value of the element. Recently a hybrid receptor model was proposed by Lewis and Stevens (2) in which the dispersion, deposition, and conversion characteristics of sulfur species in power-plant emissions... 

The sol-gel method is widely used to obtain oxide layers on the walls of microchannels. This method is advantageous because a large variety of compositions can be produced, and porosity and surface texture can be tailored. The sol-gel method is also used for the preparation of particulate porous catalytic supports [155,201,202], The colloidal metal oxide sols can be prepared by various methods such as reactions of metal salts with water or by hydrolysis and polycondensation of metal alkoxides. The latter is the most versatile procedure and has been investigated extensively. Often the sol contains varying concentrations of solid particles, and the procedure is no longer a sol-gel but rather a hybrid method, with the coating medium being a mixture between a sol and a suspension (Table 3). 

For the N22 CMC system, remaining open porosity in the CVI SiC matrix was filled by room-temperature infiltration of SiC particulate or slurry casting, followed by the melt-infiltration (MI) of silicon metal near 1400°C. This yielded a final composite with 2% closed porosity within the fiber tows and 0% porosity between the tows. The final composite system (often referred to as a slurry-cast MI composite) typically displayed a thermal conductivity about double that of a full CVI SiC composite system in which the CVI matrix process was carried to completion. Also the composite did not require an oxidation-protective over-coating to seal open porosity. Decreasing the porosity of the hybrid matrix also increased the N22 CMC elastic modulus, which in turn contributed to a high proportional limit stress. However, since the filler contained some low-modulus silicon, the modulus increase was not as great as if the filler were completely dense SiC. 

Hybrid aluminosilicate glass matrix composite with Nicalon fibre and SiC particulate reinforcement Fracture strength 778 MPa-827 MPa (depending of SiC particulate content) High-lemperature aerospace applications [74]... 

K. P. Gadkaree, Particulate-Fibre-Reinforced Glass Matrix Hybrid Composites, J. Mat. Sci. 27, 3827-3834... 

The pressure casting technique was used by Cheng and workers [78] to fabricate carbon fiber reinforced Al composites with the hybridization of a small amount of particulates or... 

SiC whiskers. The particulates or whiskers were uniformly distributed among the carbon fibers and preforms prepared from the treated fibers were directly infiltrated by molten A1 under applied stress. It was found that the longitudinal tensile strengths of hybrid composites were greatly improved, although their fiber volume fractions were quite low compared to those of conventional composites. With this hybridization method, it is also practical to tailor the fiber volume fraction of composites from 60 to 25 vol%, which is not possible in direct infiltration of fiber preforms by pressure easting. The results obtained lead to the conclusion that particulate or whisker additions do not act directly as reinforcements, but as promoters to improve the infiltration performances of fiber preforms and consequently, increase the strength transfer efficiency of carbon fibers. The addition of particulates or whiskers can also improve other properties of the composites, such as hardness and wear resistance. 

Singh B, Gupta M, Verma A (1995) Mechanical behaviour of particulate hybrid composite laminates as potential building materials. Construct Build Mater 9 39 14... 

Composites can be classified by the form of reinforcement dispersed in the matrix thus, according to this systematization, it is possible to have particulate composites (when at least one of the constituents is in the particle form), or fibrous composites (when at least one of the constituents is in the fiber form). These main categories are described hereinafter, as well as a third group of hybrid composites. 

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