Atomic Forces

This chapter discusses the physics and properties of four types of atomic forces occurring in STM and AFM: the van der Waals force, the hard core repulsion, the ionic bond, and the covalent bond. The general mathematical form of the van der Waals force between a tip and a flat sample is derived. The focus of this chapter is the covalent-bond force, which is a key in the understanding of STM and AFM. The concept of covalent bond is illustrated by the hydrogen molecular ion, the prototypical molecule used by Pauling to illustrate Heisenberg’s concept of resonance. The Herring-Landau perturbation theory of the covalent bond, an analytical incarnation of the concept of resonance, is presented in great detail. It is then applied to molecules built from many-electron atoms, to show that the perturbation theory can be applied to practical systems to produce simple analytic results for measurable physical quantities with decent accuracy.

Contributions of polyelectrolyte complexes and ionic bonding to performance of barrier films for packaging: A review

Barrier films that are used on packages play an important role, especially in the protection of food products. Research is being carried out at an accelerating pace to replace petroleum-based plastic films, which do not biodegrade and are difficult to recycle. This review article considers publications related to the use of polyelectrolyte complexes (PECs) in barrier films as a strategy to decrease the permeation of oxygen and other substances into and out from packages. Research progress has been achieved in using combinations of positively and negatively charged polymers, sometimes together with platy mineral particles, as a way to restrict diffusion through packaging materials. In principle, the ionic bonds within PECs contribute to a relatively high cohesive energy density within such a barrier film, which can resist diffusion of various gases and greasy substances. Resistance to water vapor, as well as aqueous substances, represent important challenges for barrier concepts that depend on ionic bond contributions. Factors affecting barrier performance of PEC-based films are discussed in light of research findings.

Calcium carbonate modified urea–formaldehyde resin adhesive for strength enhanced medium density fiberboard production

Reactions between CaCO3 and CH2O2 during polycondensation of UF resin produce Ca2+. Ionic bond complexation binds Ca2+ with UF resin. The UF resin crystalline percentage decreases from 26.86% to 22.71%. IB strength of resin bonded fiberboard increases from 0.75 to 0.94 MPa.

The discovery of conductive ionic bond in NiO/Ni transparent counter electrode for electrochromic smart windows of ultra-long cycle life

Developing a highly stable electrode has been a research focus for electrochromic smart windows (ECSWs) with an ultralong cycling life. This paper reports a NiO/Ni counter electrode and the discovery...

Can oppositely charged polyelectrolyte stars form a gel? A simulational study

A Langevin MD study of an equimolar mixture of monodispersed oppositely charged di- block four-armed polyelectrolyte stars is presented. We determine the minimal charged block length which results in gels and we study the ionic bond kinetics.

THE VALIDITY MULTIMEDIA INTERACTIVE BASES ANDROID ON IONIC BOND MATERIAL

This research is aims to describe the validity of interactive multimedia based on Android in the ion bonding sub material. This research uses Thiagarajan's 4-D development research consisting of Define; Design; Development and Disseminate. However, this research is limited to the Development stage of Thiagarajan in Ibrahim (2014). Multimedia validity is reviewed from the aspect of content validity and construct validity. This multimedia was validated by 2 Unesa chemistry lecturers and 1 chemistry teacher with the research instrument used in the form of a multimedia validation sheet then the results of the validation resulted in a validation score. Based on data analysis, it can be concluded that android-based interactive multimedia on the ion bond sub-material is valid for use with percentage content validation and construct validity respectively 91.85% and 89.61% with highly valid criteria.