Investigation Of Interfacial Interactions Research Articles

Investigation of the interfacial interactions in epoxy nano-composites filled with functionalized graphene based fillers

ABSTRACTThis work discusses the investigation of filler-matrix interfacial interactions in epoxy matrices filled with different loadings of graphene based fillers – graphene oxide (GO) and n-butylamine functionalized graphene oxide (GO-ButA). To probe whether the matrix cure reactivity has any influence on these interactions, two different curing agents have been used – a polyetheramine based and an aliphatic amine based to process the nano-composites. Interfacial interactions have been extensively investigated using rheology, DMA and fractographic analysis. As a complementary technique for a better understanding of these interactions, the use of dielectric spectroscopy has been explored. Rheology and dielectric spectroscopy confirm the fillers’ participation in the cure reaction. DMA and fractography show strong interfacial interaction signatures in the slow curing polyetheramine epoxies. The fast curing aliphatic amine epoxies are found to be less amenable in promoting these interactions. However, the filler dispersion quality is observed to be fairly impervious to the curing agent used. Besides surface functionalities of the fillers, the interfacial interactions are seen to be influenced by factors like cure reactivity of epoxy matrices too. Interestingly the thermal stability of the nano-composites is found to be influenced cumulatively by the interfacial interactions and the thermal stability of the fillers.

Comparative characterization of chip to epoxy interfaces by molecular modeling and contact angle determination

An investigation of interfacial interaction has been performed between three epoxy molding compound materials and a native silicon dioxide layer (SiO2) usually found at chip surfaces. The epoxy materials were an industry oriented epoxy molding compound Epoxy Phenol Novolac (EPN), its filled variety EPNF (with silica particles) and a model aromatic epoxy11,3-Bis(2,3-epoxypropoxy)-benzene and a 1,2diamino(ethane)2 hardener in a 2:1 mixing ratio.1 (212). All systems are described in full in [1] and [2]. The free surfaces of the solid materials were experimentally analyzed by contact angle measurements of three different liquids (water, methylene-iodide (MI) and glycerol). Results are compared to interfacial energies obtained by analysis of the interfaces in bimaterial molecular models, yielding reasonable agreement. A qualitative prediction regarding the influence of water on the interfacial strength between chip and molding compound is attempted.

Reinforcement and interphase of polymer/graphene oxide nanocomposites

Polymer/graphene (oxide) nanocomposites exhibit enhanced mechanical properties at low volume fractions of graphene-based nanofillers. An understanding of the reinforcement behaviour was developed through the investigation of interfacial interactions between graphene oxide (GO) nanoplatelets and polymer matrix (PLLA, PCL, PS or HDPE) by combination of microstructure characterization and micromechanical modeling methods. The interfacial interaction determines the degree of dispersion of GO in polymers, interfacial adhesion strength as well as reinforcement efficiency, which can be tailored by the surface chemistry of GO and functionality of polymers. Homogeneous dispersion of GO nanoplatelets with high aspect ratios was found in PLLA and PCL matrices, as well as in lower polar polymer PS due to the preferable interactions between the aromatic rings and the graphene layers, while stacked GO layers with a lower aspect ratio were observed in HDPE matrix even with the presence of an organic compatibilizer. The theoretical elastic moduli of the four kinds of polymer/GO nanocomposites calculated by using the Halpin–Tsai model or a combination of Laminate theory and Mori–Tanaka model underestimated the experimental results. Considering the interfacial interactions, an effective volume fraction was introduced to the above composite models which interpreted the experimental data well. The interphase zone was thus quantified by using micromechanical modeling based on the measured mechanical properties of polymer/GO nanocomposites.

Modeling and Investigation of Interfacial Interaction between PLA and One Type of Deficient Hydroxyapatite

A model of one type of deficient hydroxyapatite (D-HA) was constructed, and the interaction mechanism between polylactide acid (PLA) and the (001) surface of D-HA was also investigated for the first time employing density functional theory (DFT) in the Perdew, Burke, and Ernzerhof (PBE) generalized gradient approximation (GGA). First, a mathematical model of D-HA was abstracted from experimental facts, through which a group of special values and the nonstoichiometric formula, Ca(8)[(HPO(4))(3)(PO(4))(2)(CO(3))](OH)(2), were obtained. Next, a stable configuration of D-HA was achieved with the method of searching stable structure gradually. After the most stable configuration was identified, our attention mainly turns to the results concerning the (001) surface of D-HA. Methyl lactate was employed to act as PLA monomer estimating the interaction behavior between PLA and D-HA. Simultaneously, to achieve an accurate description of hydrogen bonds (hbs), a plane wave energy cutoff of 700 eV was used. Significantly, we observed that there were two P-OHs on the surface, but only one can form a hydrogen bond with PLA; also, besides the interaction between carbonyl oxygen (C=O) in the PLA and calcium ions in the D-HA, there are two kinds of hbs interactions: one type is the medium stronger hbs between the C=O and the hydrogen in HPO(4)(2-) with the bond length of 1.69 A and bond energy of about 48 kJ mol(-1); the other is the weak hbs between the oxygen in phosphate and the hydrogen in methyl/methylene with the average bond length of about 2.48 A and bond energy of about 9 kJ mol(-1). PDOS was also employed to characterize the existence of hbs. Our results may have potential promotion to investigate the properties of polymeric nanocomposites.

Investigation of interfacial interaction and structural transition for epoxy/nanotube composites by positron annihilation lifetime spectroscopy

Positron annihilation lifetime spectroscopy was employed to study the effect of amine modification on interfacial interaction and structural transition for epoxy/multiwalled carbon nanotube (MWNT) composites. Temperature dependence of orthopositronium lifetimes suggests that sample with amine-modified MWNTs possesses the highest glass transition temperature compared with unmodified samples and neat epoxy resin, which indicates that stronger interfacial interactions exist between epoxy matrix and amine-modified MWNTs, as a result of the covalent bonds and other weak forces. This is testified by interaction parameter β calculated in terms of the positron annihilation parameter.

Investigation of Interfacial Interaction and Microstructure for Epoxy/CNTs Nanocomposites by PALS

Epoxy nanocomposites with multi-walled carbon nanotubes (MWNTs) were prepared. The interaction between MWNTs and epoxy matrix and microstructure were systematically investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and the positron annihilation technology (PAT) respectively. The glass transition temperatures were determined by the variation of the free volume size.

Transferwear During Cu CMP

We conducted fundamental investigation of interfacial interactions between copper and polyurethane surfaces. Using in situ surface analysis techniques we were able to evaluate effects of water molecules on both materials surfaces during rubbing. Evidence of transferring elements between copper and urethane surfaces due to friction was found. Further investigation on pad wear indicated that transfer wear was taking a major role during copper CMP and mixed wear modes dominated pad wear.

Investigation of interfacial interaction between uncoated and coated carbon fibres and the magnesium alloy AZ91.

Unidirectionally reinforced metal-matrix composites with a fibre volume content between 63 and 68% were processed by squeeze casting using T800 H carbon fibres and the magnesium alloy AZ91. The surface of the fibres was prepared by thermal desizing of the fibres or by deposition of a pyrolytic carbon (pyC) coating. Different interfacial conditions could be identified by transmission electron microscopy (TEM) and the single-fibre push-in test. TEM confirmed the formation of needle-like phases at the fibre surface or, for coated fibres, within the pyrolytic carbon coating. During loading by the Vickers type indenter an intense response was observed for composites of coated fibres and the magnesium alloy. This could by caused by stick-slip effects within the pyrolytic carbon coating.