Do We Use Thorium The Radioactive Carcinogen

Here in berhampur we have a Plant of DAE extracting rare earth materials from sea beach mud. The prime element is Thorium a radioactive element can be used as a nuclear fuel.

But the intresting fact is we are using it in home also. Yes that is inside the picture tube, in gas lamp mantels. In lab its with the Photo MultiPlier Tube (PMT), PMT is are inside almost every analytical instruments.

Why is it used in picture tube ?

Filaments in electronic tubes and television picture tubes have be coated in thorium oxides to produce electrons more easily

Radioactivity:

Thorium oxide coated gas lamp mantles used in ornamental gas lanterns and gas burning camping lamps are radioactive. The thorium oxide is chosen because it can be raised to white heat without decomposing. However, the mantle does become extremely fragile and will powder into a fine ash which can potentially be inhaled or ingested. Thorium is a natural alpha emitter with the potential for increasing lung tumors. Thorium disintegrates to produce radon-220, an alpha particle emitting radioactive gas.

A number of substances have been used as positive contrast agents: silver, bismuth, caesium, thorium, tin, zirconium, tantalum, tungsten and lanthanide compounds have been used as contrast agents. The use of thoria (thorium dioxide) as an agent was rapidly stopped as thorium causes liver cancer.

For conventional dynode materials, such as BeO and MgO, a multiplication factor of 10 can normally be achieved by each dynode stage.

Microchannel plate detector

Scanning Tunneling Microscope(STM) & Atomic Force Microscope (AFM)

STM & AFM

Scanning Tunneling Microscope (STM)

These are devices 2D & 3D Surface analysis of Materials at micrometer resolution. Scanning Tunneling Microscopic is based upon the tunneling theory i.e. an electron may tunnel (or jump) through a barrier when the barrier is thin enough. So produces

an elctric current at the surface. If we can use a microtip probe. we can monitor the tunneling current profile in a 2D surface. Which will give a 2D picture of the atomic structure. But the necessary condition for the probe to get image at atomic scale is that the probe shou

ld be moved at such resolution.

Here comes the role of Piezo transducers, we have used steppers Servos for precison positioning but when the precison we need is of micrometer level we have the only option Piezo Transducers.

As we know Piezo materials produce Structurals change (expand or compress) in the axis of applied field. So for an X Y scan we can use two piezo plates or a single block and the probe at a corner. Commonly we use two piezo plates at two sides.

Some more PIC of AFM

References:

http://www.siint.com/en/products/spm/tec_descriptions/descriptions2_e.html

http://www.ieap.uni-kiel.de/surface/ag-kipp/stm/stm.htm

http://www.quasi.iastate.edu/hot.html

http://sxm4.uni-muenster.de/stm-en/STMElectronics.html (Making DIY STM)

http://www.stm.phas.ubc.ca/Science/Introduction-to-STM.html

http://www.foresight.org/UTF/Unbound_LBW/chapt_4.html

http://www.tutorialsweb.com/nanotech/page-6.htm

http://www.phys.ttu.edu/~tlmde/thesis/DESIGN_AND_CONSTRUCTION.html

http://www.physics.leidenuniv.nl/sections/cm/ip/Onderwijs/Scanning-Probe-Microscopy/Chapters/CHEN%20Chapter%209%20Piezoelectric%20scanner%20213-235.pdf

http://www.nanodic.com/Nanocharacterization/Atomic_Force_Microscopy.htm

http://chemwiki.ucdavis.edu/Wikitexts/UCD_Chem_205%3A_Larsen/ChemWiki_Module_Topics/How_an_FTIR_Spectrometer_Operates

ParaMagnetic Gas Analyser GA-2

This method is primarily for oxygen content analysis. As the method described is suitable for paramagnetic gases its usable for few industrial gases.

Block Diagram Paramagnetic Gas Analyzer

This method is primarily for oxygen content analysis. As the method described is suitable for paramagnetic gases its usable for few industrial gases.

Relative volume magnetic Susceptibilty at 20deg celcius(Zero ref:Nitrogen, 100 ref O2)
Oxygen 100.00
Nitric Oxide 43.00
Air 23.50
Hydrogen 0.24
Carbon monoxide 0.01
Nitrogen 00.00
Nitrogen Oxide -0.20



References:
http://www.habmigern2003.info/suggestions/Problems/oxygen/Oxygen-sensors.html
http://www.fujielectric.com.cn/products/airanalyze/pdf/EDS3-125a.pdf
http://www.systechillinois.com/media/296bae86/paramag_98.PDF
http://www.systechillinois.com/en/paramagnetic-cells_54.html

GAS Analyser -1 (Thermal Conductivity Type)

Thermal Conductivity of Gases different and unique for all. So this property can be used to distinguish gas concentrations in a mixture of gases.

Thermal conductivity of a mixture of gas

where is the thermal conductivity of jth gas whose concentration is ,

so that

from the above equations its confirmed that concentration of a gas in a mixture of gases can be determined from the change in thermal conductivity.

Now we have to make out some way to measure the change in thermal conductivity by addition of the gas in the mixture. So how to measure thermal conductivity of a gas.

Simple, let it conduct heat and see how fast is it conducting. So the arrangement is a hot body surrounded by cold wall and between the hot n cold bodies the media is the "gas mixture". The gas mixture will conduct heat from the hot body(an electrically heated filament) to the surrounding relatively cool walls.

Heat Gained by hot body=

Heat Lost By hot body= Convection Loss+Conduction Loss+ Radiation Loss

At thermal equilibrium heat loss=heat gained

Now we have to monitor temperature at thermal equilibrium

References:

http://www.systechillinois.com/en/thermal-conductivity_52.html

http://www.hitech-inst.co.uk/thermal_conductivity_sensors.php

GAS Analyser

Gas Analysers are of different types based upon different techniques

1. Thermal Conductivity

2. Heat of Reaction

3. Para-magnetic

4. Selective Absorption

5. Electrochemical

6. Optical Spectroscopy(Emission, Absorption, Diffraction)

7. Opacity

8. Humidity & moisture

I will start with the Thermal Conductive Type Gas Analysers