Read the text. Make a summary of it.

Nanoparticle

A nanoparticle (or nanopowder or nanocluster or nanocrystal) is a microscopic particle with at least one dimension less than 100 nm.

Nanoparticle research is currently an area of intense scientific research, due to a wide variety of potential applications in biomedical, optical, and electronic fields. Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures.

A bulk material should have constant physical properties regardless of its size, but at the nanoscale this is often not the case.

Size-dependent properties are observed. The properties of materials change as their size approaches the nanoscale and as the percentage of atoms at the surface of a material becomes significant.

For very little materials larger than one micrometer the percentage of atoms at the surface is minuscule relative to the total number of atoms of the material.

The interesting and sometimes unexpected properties of nanoparticles are not partly due to the aspects of the surface of the material, dominating the properties. Nanoparticles exhibit a number of special properties relative to bulk material.

For example, the bending of bulk copper (wire, ribbon, etc.) occurs with movement of copper atoms/clusters at about the 50 nm scale.

Copper nanoparticles smaller than 50 nm are considered super hard materials that do not exhibit the same malleability and ductility as bulk copper.

The change in properties is not always desirable.

Ferroelectric materials smaller than 10 nm can switch their magnetization direction using room temperature thermal energy, thus making them useless for memory storage.

Nanoparticles often have unexpected visible properties because they are small enough to confine their electrons and produce quantum effects.

For example gold nanoparticles appear deep red to black in solution. Nanoparticles have a very high surface area to volume ratio.

 

Prepare for a group debate: “By bridging science business and engineering together it should be feasible to find nanotechnology solutions to global challenges”.

 

 

Unit 6

ELECTRONICS

Read the text and give your partner a detailed account on the most common electronic components.

Electronics

Electronics is at the heart of twenty-first century technology. Without electronics there would be no computers, televisions, radios, mp3 players, mobile phones, cinemas, video games, and almost all domestic appliances. Cars would not start, hospital equipment would not work, and planes would not fly. Most electronic circuits use low voltage and low current so tiny portable entertainment devices are now commonplace.

All electronics depends on the movement of electrons round a circuit. Circuits diagrams are drawn using standard symbols. Switch on presents the symbols for some of the most common electronic components. In addition to symbols, electronic components are labeled using abbreviations such as Sw for a switch, R for a resistor, and C for a capacitor. The value of each component is also shown using standard abbreviations, for example pF is picoFarads.

Relays are electromagnetic switches. They consist of an iron core with a copper coil wound round it. When current flows through the coil, the core becomes a magnet and pulls a movable contact arm towards it. This can make or break circuits just like a switch.

Transformers can step up or step down an ac (alternating current) voltage. They consist of thin metal plates with copper coils wound round them. When a voltage flows through the primary coil it induces a voltage in the secondary coil. Whether the induced voltage is higher or lower depends on the number of turns in the coil.

Potentiometers, variable resistors, are used to change the resistance in a circuit easily. They are used in volume controls, light dimmers, and other applications.

Fixed resistors have standard values. Thermistors vary in resistance according to temperature. Capacitors store electrical energy. They can be charged and discharged very quickly. They are particularly important in high frequency devices such as radios. Electrolytic capacitors are usually larger. They can be connected in one way only and are used to store electricity and to smooth out pulsating signals, for example in power supplies. Diodes allow current to flow through in one direction only. A light emitting diode (LED) produces light when a current flows through it. Transistors contain tiny chips of semiconductor materials. They can be used as switches, as amplifiers, and as oscillators. Logic gates are integrated circuits which provide the basic logic functions used in computers and other devices which use digital electronics. Signals in digital circuits are either on (1) or off (0). Basic logic gates include AND, OR, NAND and NOR.