Partially hydrogenated and fluorinated graphene: Structure, roughness, and negative thermal expansion

Thermal expansion coefficient of hydrogenated amorphous carbon

The coefficient of thermal expansion ~CTE! of hydrogenated amorphous carbon (a-C:H) was investigated as a function of the concentration of sp hybridization. The CTE, determined using the thermally induced bending technique, depends on the concentration of sp bonded carbon, increasing to the value of graphite as the sp concentration approaches 100%. By using a combination of the thermally induce...

Exchange interactions and frustrated magnetism in single-side hydrogenated and fluorinated graphene

Negative Thermal Expansion

Introduction Many materials which we encounter in everyday life expand on heating. This fact of life is easily highlighted with a simple experiment that we are all familiar with and involves a metallic sphere passing through a metal ring. At room temperature, the sphere is of such a size that it can easily pass through the ring, but after the sphere is heated, it will have expanded with the res...

Novel Synthesis of Slightly Fluorinated Graphene Quantum Dots with Luminescent and Paramagnetic Properties through Thermal Cutting of Fluorinated Graphene

A novel approach has been developed to synthesize slightly fluorinated graphene quantum dots (GQDs-F) through thermal cutting of highly fluorinated graphene. The fluorinated graphene with substantial structure defects is fragile and is readily attacked. The direct evaporation of abundant CFn (n = 2, 3) groups near structure defects lead to the loss of adjacent skelton C atoms, and the fluorinat...

Negative Thermal Expansion in Ba0.5Sr0.5Zn2SiGeO7

Solid solutions with the composition Ba0.5Sr0.5Zn₂Si2-xGexO₇ and BaZn₂Si2-xGexO₇ were prepared with different values of x using a conventional mixed oxide route. Both compounds exhibit very different thermal expansion, which is due to the different crystal structures. Ba0.5Sr0.5Zn₂Si2-xGexO₇ solid solutions exhibit the structure of high-temperature BaZn₂Si₂O₇ and show negative thermal expansion...