Shear strength measurements of hafnium diboride thin solid films

Lee, Jung‐Kyu; Polychronopoulou, Kyriaki; Cloud, Andrew N.; Abelson, John R.; Polycarpou, Andreas A.

doi:10.1016/j.wear.2014.06.017

Cited by 7 publications

(5 citation statements)

References 31 publications

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“…Also, the covalent bond between rGO and xPVAm and entanglement of xPVAm chains happening during the cross-linking enhances the stress transfer and shear strength. Shear strength of all PVAm/GO films is comparable to ultrahard ceramic coatings such as HfB 2 on silicon (τ c = 4.3 GPa) . However, the adhesive strength is much smaller due to the viscoelastic nature of polymer and weak GO bonding (σ a = 1.1 for as-deposited HfB 2 films).…”

Section: Resultsmentioning

confidence: 85%

“…The scratch force is increased linearly to reach the critical load ( P c ). P c is defined as the load required to rapture/delaminate the film and identified by a sudden change in the normal displacement . The critical load can be used to measure the shear and adhesive strengths at the coating–substrate interface.…”

Section: Resultsmentioning

confidence: 99%

“…P c is defined as the load required to rapture/delaminate the film and identified by a sudden change in the normal displacement. 52 The critical load can be used to measure the shear and adhesive strengths at the coating−substrate interface. Interfacial stress transfer is an important factor to study.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Shear strength of all PVAm/GO films is comparable to ultrahard ceramic coatings such as HfB 2 on silicon (τ c = 4.3 GPa). 52 However, the adhesive strength is much smaller due to the viscoelastic nature of polymer and weak GO bonding (σ a = 1.1 for as-deposited HfB 2 films).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Nanoindentation and nanoscratch experiments are an effective way to measure these properties. − The hardness and elastic modulus can be obtained through the Oliver–Pharr method . In addition, scratch testing is typically used to measure the friction coefficient and gain insight into the interfacial shearing required for both single-layer and multilayered coating removal. − …”

Section: Introductionmentioning

confidence: 99%

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Influence of Graphene Reduction and Polymer Cross-Linking on Improving the Interfacial Properties of Multilayer Thin Films

Humood

Qin

Song

et al. 2016

ACS Appl. Mater. Interfaces

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Graphene is a versatile composite reinforcement candidate due to its strong mechanical, tunable electrical and optical properties, and chemical stability. However, one drawback is the weak interfacial bonding, which results in weak adhesion to substrates. This could be overcome by adding polymer layers to have stronger adherence to the substrate and between graphene sheets. These multilayer thin films were found to have lower resistance to lateral scratch forces when compared to other reinforcements such as polymer/clay nanocomposites. Two additional processing steps are suggested to improve the scratch resistance of these films: graphene reduction and polymer cross-linking. Graphene/polymer nanocomposites consisting of polyvinylamine (PVAm) and graphene oxide (GO) were fabricated using the layer-by-layer assembly (LbL) technique. The reduced elastic modulus and hardness of PVAm/GO films were measured using nanoindentation. Reducing GO enhances mechanical properties by 60-70% while polymer cross-linking maintains this enhancement. Both graphene reduction and polymer cross-linking show significant improvement to scratch resistance. Particularly, polymer cross-linking leads to films with higher elastic recovery, 50% lower adhesive and plowing friction coefficient, 140 and 50% higher adhesive and shear strength values, respectively, and lower material pileup and scratch width/depth.

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Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%