Plasma Device And Technology
#1

Presented By
Arun Kumar Soni

[attachment=9839]
Introduction
Plasma:-
-
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. The basic premise is that heating a gas dissociates its molecular bonds, rendering it into its constituent atoms. Further heating leads to ionization (a loss of electrons), turning it into a plasma: containing charged particles, positive ions and negative electrons
History
Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879 (he called it "radiant matter"). The nature of the Crookes tube "cathode ray" matter was subsequently identified by British physicist Sir J.J. Thomson in 1897, and dubbed "plasma" by Irving Langmuir in 1928,[ perhaps because it reminded him of a blood plasma. Langmuir wrote:
Except near the electrodes, where there are sheaths containing very few electrons, the ionized gas contains ions and electrons in about equal numbers so that the resultant space charge is very small. We shall use the name plasma to describe this region containing balanced charges of ions and electrons.
Plasma - Fourth State of Matter
Generation of artificial plasma

plasma is generated when an electrical current is applied across a dielectric gas or fluid (an electrically non-conducting material) as can be seen in the image below, which shows a discharge tube to be considered as a simple example (DC used for simplicity).
The potential difference and subsequent electric field causes the bound electrons (negative) to be pulled toward the anode (positive electrode) while the nucleus (positive) is pulled to the cathode (negative electrode).[30] As the voltage is increased, the current stresses the material (by electric polarization) beyond its dielectric limit (termed strength) into a stage of electrical breakdown, marked by a spark, where the material transforms from being an insulator into a conductor (as it becomes increasingly ionized). This is a stage of avalanching ionization, where collisions between electrons and neutral gas atoms, create more ions and electrons (as can be seen in the figure on the right). The first impact of an electron on an atom results in one ion and two electrons. Therefore, the number of charged particles increases rapidly (in the millions) only “after about 20 successive sets of collisions”[31], mainly due to a small mean free path (average distance travelled between collisions).
• With ample current density and ionization, this forms a luminous electric arc (essentially lightning) between the electrodes.[Note 1] Electrical resistance along the continuous electric arc creates heat, which ionizes more gas molecules (where degree of ionization is determined by temperature), and as per the sequence: solid-liquid-gas-plasma, the gas is gradually turned into a thermal plasma.[Note 2] A thermal plasma is in thermal equilibrium, which is to say that the temperature is relatively homogeneous throughout the heavy particles (i.e. atoms, molecules and ions) and electrons. This is so because when thermal plasmas are generated, electrical energy is given to electrons, which, due to their great mobility and large numbers, are able to disperse it rapidly and by elastic collision (without energy loss) to the heavy particles
• Cascade process of ionization. Electrons are ‘e−’, neutral atoms ‘o’, and cations ‘+’.
Plasma Categories
Properties

• Plasma Density
• Temperatures
• Debye length
• Plasma frequency
Plasma Density
• For plasma to exist, ionization is necessary. The term "plasma density" by itself usually refers to the "electron density", that is, the number of free electrons per unit volume.
• The degree of ionization of a plasma is the proportion of atoms which have lost electrons, and is controlled mostly by the temperature.
• The degree of ionization α is defined as α = ni/(ni + na) where ni is the number density of ions and na is the number density of neutral atoms.
Temperatures
• Because of the large difference in mass, the electrons come to thermodynamic equilibrium amongst themselves much faster than they come into equilibrium with the ions or neutral atoms. For this reason the "ion temperature" may be very different from (usually lower than) the "electron temperature". This is especially common in weakly ionized plasmas, where the ions are often near the ambient temperature.
• Temperature controls the degree of plasma ionization. A plasma is sometimes referred to as being "hot" if it is nearly fully ionized, or "cold" if only a small fraction (for example 1%) of the gas molecules are ionized. Even in a "cold" plasma the electron temperature is still typically several thousand degrees Celsius.
Debye screening
• A Debye sphere is a volume whose radius is the Debye length, in which there is a sphere of influence, and outside of which charges are screened.
Plasma Frequency
• Consider a neutral plasma, consisting of a gas of positively charged ions and negatively charged electrons. If one displaces by a tiny amount all of the electrons with respect to the ions, the Coulomb force pulls back, acting as a restoring force.
• Application’s
PLASMA WELDING
• Plasma beam is used for fusion welding process. Plasma arc welding is a gas shielding process.
• Done with or without filler wire addition.
• Coalescence of metals is achieved through heat transferred by arc created between tungsten electrode and the workpiece.
• The arc is constricted in a copper alloy nozzle orifice to form a highly collimated arc column
variable polarity plasma arc is used
electrode is +ve for short time(ms)
and –ve for long time(ms)
during former there will be cleaning action which removes the oxides from work piece as heavy ions strike the work piece and during the later there will be penetration.
Advantages:
• Automation is possible
• Low currents are used
• Minimum human exposure is involved
• Ozone emission low.
Disadvantages:
• Complicated torch design
• High maintenance cost
• Protection from electric shocks is required
• Electromagnetic waves hazards.
Used for
In welding titanium and its alloys. Corrosion resistance will not be affected, hence used in welding stainless steel alloys.`
PLASMA CUTTING
It is an erosion process. It utilizes a constricted arc in the form of a high velocity jet of ionized gas to melt the material.
An inert gas is focused under pressure through a small orifice infront of the cutting torch connected to the DC power supply.
In the torch a portion of inert gas is ionized by the electric discharge from the power source. The arc is created between a negative tungsten electrode electrode in the torch through which the gas flows to the work piece.
Plasma arcs are extremely hot and are in the range of 15,000 degrees Celsius.
• Hand-held torches can usually cut up to 2 in (48 mm) thick steel plate, and stronger computer-controlled torches can pierce and cut steel up to 12 inches (300 mm) thick.
Advantages
• Very high quality cuts are obtained
• High speed cuttings can be done
• Automation is possible
• Process is applicable to all metal and alloys
Disadvantages
• Hazardous fumes and gases, high level of noise.
• Proper clothing, helmets etc is very much essential.
PLASMA SPRAYING
• Molten metallic or non metallic material is sprayed on to a prepared substrate to form a coating.
• The sprayed material is in the powder form. It is propelled by a stream of ionized gas on to the substrate. The particles striking the surface gets flattened to form thin platelets.
• The substrate surface which can be kept below 473K eliminating metallurgical changes in base material.
• The temperature is as high as 1100 deg cel. The powder size is 10-44 microns for free flow. Spherical powders are best.
• Powders of Al. Ni, Cr, WC-CO are sprayed by this technique.
• Thickness of coating is 0.0025 - 0.075mm. The hardness of coating is 150 – 350 VHN.
• This technique is used in shafts, liners, pistons, valves, cast metal rams.
Advantages
• Oxidation of powder is minimal
• Highly dense coating are produced
• Mechanical and metallurgical properties are superior due to high temperature and high velocity as well.
• Decomposition of powder is minimised.
Disadvantages
• Very high temperatures are required
• Process is noisy
• Radiation hazards and toxic fumes, high volume of waste products.
TOKOMAK NUCLEAR FUSION REACTOR
• The chamber itself is usually of the two layer kind.
• Plasma is produced inside a thin corrugated stainless shell 0.2-0.3mm thick. This thin inner chamber is known as liner and is inserted into a thick outer copper envelope.
• The space between the liner and the outer envelope is evacuated to a very low pressure. This enables one to maintain clean vaccum condition since the liner can be baked by passing a current through it. And thereby degassing it.
• The biggest of such Tokomak installation developed in Russia can produce a current of 2.5 to 3*105 amps with a stabilizing longitudinal magnetic field of 40000 oe. Such an installation, plasma filament can exist for 0.005-0.02sec. A maximum temperature of 20 lakhs deg.cel. can be achieved so far.
Plasma Medicine
• Plasma medicine is an innovative and emerging field combining plasma physics, life sciences and clinical medicine to use physical plasma for therapeutic applications. Initial experiments confirm that plasma can be effective in in vivo antiseptics without affecting surrounding tissue and, moreover, stimulating tissue regeneration. Based on sophisticated basic research on plasma-tissue interaction, first therapeutic applications in wound healing, dermatology and dentistry will be opened.
CONCLUSIONS
• Plasma technology is widely used in metallurgy and materials processing for welding, cutting, spraying, sintering, melting, surface treatment etc.
• It holds a great assurance for the future with plasma engines, electricity production, nuclear reactors economically on a large scale.
Reply
#2

The monitors of those first plasma was fairly small devices, and materials to create expensive and difficult to obtain. The lower cost of these materials in today's world, coupled with the rise of technology, brought them great TVs in widespread use and their market penetration is likely to grow as prices continue to fall.
Reply

Important Note..!

If you are not satisfied with above reply ,..Please

ASK HERE

So that we will collect data for you and will made reply to the request....OR try below "QUICK REPLY" box to add a reply to this page
Popular Searches: plasma science and fusion center mit, plasma technology waste to energy, ppt slides on plasma tv technology, new plasma tv technology 2012**dy consumer attitude toward sony tv, plasma technology in textile, new plasma tv technology 2012, plasma technology systems,

[-]
Quick Reply
Message
Type your reply to this message here.

Image Verification
Please enter the text contained within the image into the text box below it. This process is used to prevent automated spam bots.
Image Verification
(case insensitive)

Possibly Related Threads...
Thread Author Replies Views Last Post
  LAMP TECHNOLOGY (LINUX,APACHE,MYSQL,PHP) seminar class 1 3,472 04-04-2018, 04:11 PM
Last Post: Guest
  5 Pen PC Technology project topics 95 98,878 21-08-2015, 11:18 PM
Last Post: Guest
  Jini Technology computer science crazy 10 13,663 19-08-2015, 01:36 PM
Last Post: seminar report asees
  3D-OPTICAL DATA STORAGE TECHNOLOGY computer science crazy 3 8,502 12-09-2013, 08:28 PM
Last Post: Guest
Question 4g wireless technology (Download Full Report ) computer science crazy 35 33,870 15-03-2013, 04:10 PM
Last Post: computer topic
  FACE RECOGNITION TECHNOLOGY A SEMINAR REPORT Computer Science Clay 25 35,285 14-01-2013, 01:07 PM
Last Post: seminar details
  TWO WAY STUDENT INFORMATION SYSTEM USING CELLULAR TECHNOLOGY smart paper boy 3 3,471 24-12-2012, 11:24 AM
Last Post: seminar details
  TOUCH SCREEN TECHNOLOGY seminar projects crazy 1 3,276 06-12-2012, 12:12 PM
Last Post: seminar details
  Brain finger printing technology seminar projects crazy 43 48,041 05-12-2012, 02:41 PM
Last Post: seminar details
  A survey of usage of Data Mining and Data Warehousing in Academic Institution and Lib seminar class 1 2,119 29-11-2012, 12:56 PM
Last Post: seminar details

Forum Jump: