Lecture 3 Properties of Nanomaterial- Surface to Volume Ratio.ppt
- 1. Lecture 2 Learning Outcomes: 1. Surface to volume ratio and its effect 2. Surface states and its advantages
- 2. What Is Nano ? Nanotechnology: A more generalized description of nanotechnology was subsequently established by the National Nanotechnology Initiative, which defines nanotechnology as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers. IUPAC Definition: a nanoparticle is a particle of any shape with dimensions in the range of 10−9 to 10−7 m. 7 Introduction to nanotechnology
- 3. Introduction to nanotechnology 3 History of Nanotechnology As far back as the fourth century, nanoparticles were used by artisans for generating a glittering effect on the surface of pots. One the left is a famous artifact called the Lycurgus Cup resides in the British Museum in London. What makes this cup unique is that its color changes from green (when illuminated from the outside) to red (when illuminated from within) due to nanoparticles of gold and silver in the glass. Modern scientific evaluation of colloidal nanoparticles did not begin until Michael Faraday's work of the 1850s. He provided the first description, in scientific terms, of the optical properties of nanometer-scale metals in his classic 1857 paper. In 1959, Richard Feynman first introduced the concept of nanotechnology in his talk “There's Plenty of Room at the Bottom,” in which he described the possibility of synthesis via direct manipulation of atoms. The term "nano-technology" was then first used by Norio Taniguchi in 1974. With the invention of electron microscopes, analyses on small matters become much easier. Thus research on nanotechnology flourishes quickly. To date, nanotechnology has become an interdisciplinary bridge due to unique properties of nanomaterials, widely applied to pharmacy, therapeutics, electromagnetics and catalysis.
- 4. 4 Three (of several) Senses of Small • Size and surface area effects 1 nm – 100 nm Fundamental materials properties remain the same but size, shape and surface area alter some behaviors work function, solubility, chemical potential, contaminate sorption • Critical Size and Characteristic Length Scale Interesting or unusual properties because the size of the system approaches some critical length (includes quantum effects). Many characteristics of material may have normal or nearly normal behavior • New (Non-extensive) Properties Systems not large enough to have extensive properties. Particles become effectively polymorphs of “bulk” materials and statistical homogeneity may not be valid. n = 1 n = 3 n = 2 n = 4 n = 5 Energy / (h 2 /8ml 2 ) 25 16 1 4 9 0 size d V= correlation length d = range of intermolecular forces • Kelvin equation for solubility • Gibbs-Thompson relation for chemical potential What do we we mean by small particle and why does their chemistry change?
- 6. DIFFERENCE BETWEEN BULK AND NANOMATERIALS BULK carbon as graphite Nano carbon as graphene
- 8. AN EXAMPLE TO START WITH
- 9. THE FIRST DIFFERENCE – SURFACE TO VOLUME
- 10. WHAT IT DOES ? • The large surface area to volume ratio of nanoparticles opens many possibilities for creating new materials and facilitating chemical processes. In conventional materials, most of the atoms are not at a surface; they form the bulk of the material. • In nanomaterials, this bulk does not exist. Indeed, nanotechnology is often concerned with single layers of atoms on surfaces. Materials with this property are unique. For example, they can serve as very potent catalysts or be applied in thin films to serve as thermal barriers or to improve wear resistance of materials.
- 13. An example of nano and bulk coating on surface