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Plasma deposited thermocouple

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Plasma deposited thermocouple

  1. 1. SHAHINA P.AS8 EIROLL NO:61 1
  3. 3. INTRODUCTION Describes the realization of temperature sensor Based on plasma sputtered thermocouple Realized in vacuum with quite pure materials Negligible oxidation Accurate measurement Made inert Thickness of few nanometers Application in lyophilization process 3
  4. 4. TEMPERATURE MEASUREMENT Temperature is local parameter Thermocouples for temperature measurement Can be less invasive Consumes negligible power Realize in flexible and cylindric probes 4
  5. 5. With these advantages, but thermocouple Alter temperature distribution Metalic materials react with surrounding environment These 2 problems occur in preeze drying of lyophilization process 5
  6. 6. LYOPHILIZATION PROCESS Process of drying a substance by sublimation Preliminary frozen at -20⁰c Pressure reduced to few pascals So sublimates slowly Leaving dried powder Most pharmaceutical powders are made by this method 6
  7. 7. Principle of freeze drying Drying by sublimation Frozen liquid to gaseous state Transfer of ice to water vapour Function of pressure and ice temperature Expensive Requires specialized equipment 7
  8. 8.  Freeze drying consists of 3 stages Freezing Primary drying Secondary drying During freezing solution- solid During 1⁰ drying ice removed by sublimation 2⁰ drying is for isothermal desorption 8
  9. 9. Advantages of freeze drying• Do not need refrigeration• Can be stored at ambient temperatures• Can be completely reconstituted with water• Stable over 2 year life 9
  11. 11. PROBLEM OF FREEZE DRYING When pressure reduced, drying begins Product tyemperature decreases Sublimation is endothermic Most of energy is by radiation ie, quite low at low temperature too Lead to temperature of product go down -50⁰ c to -70 ⁰c Turns long lyophylization times 11
  12. 12. Possible solution is To model drying process Supply heatBut this lead to another problem Thermal conductivity between shelf and product is higherie ,sublimatiom is slower 12
  13. 13. A good and easy solution is that To monitor the temperature inside the product in several points within the chamber But it will alter drying proceess And intoxicate the materialSo possible solution is….. To measure temperature near to product Not in contact Eg: on external wall of vial 13
  14. 14. PROPOSED SYSTEMFig. 1. Two thermocouples deposited on the external part of avial tocheck the deposition effectiveness on curved surfaces.The vial shows twocopper/copper-nickel thermocouples bothwith a junction at the top of the vial, but with the other junctionat different heights. In the picture also the wires used to collectthe thermocouple voltage 14
  15. 15.  Extremely thin and sealed TC Deposited via plasma sputtering For local measurement- thin TC Low response time Sealed devices for specific applications Present proposal uses a protective Siox thin film 15
  16. 16.  Thickness of few tens of nm To avoid contact between metal and drying substance This way TC can deposited on vial internal surface Able to follow temperature changes accurately Without altering the lyophilized material 16
  17. 17. PLASMA SPUTTEREDTHERMOCOUPLE A TC can be made by 2 different materials To form 2 junction To measure voltage Proportional to temperature difference Materials are… iron, copper, constantan, chromel, alumel, platinum, rhodium; each couple having specific electrical and chemical properties. 17
  18. 18.  Several metal couples for drying process Choice related to Thermoelectric power Easiness of plasma deposition Chemistry of TC/Siox interface In order to ensure good adhesion 18
  19. 19. •To optimize plasma process few considerationsare Plasma pretreatment to improve adhesion To reduce no: of defects of deposited coating To improve barrier properties Plasma pretreatment carried out in noble as well as reactive gases Such as oxygen and hydrogen 19
  20. 20. •According to metal Iron –pretreatment in oxygen plasma Aluminum- metal surface reduction by hydrogen glow discharge All these require 2 step deposition But Cu and Ni not require surface modification So all specimens made of T type TC(Cu/CuNi) Thermoelectric power -50 μV/◦C 20
  21. 21.  Thickness of active materials Thin layer allows non invasive sensors But high electrical resistance Thick layer alows more invasive Produces low resistance, but large sputtering times So here proposed range 50nm to 500nm 21
  22. 22. REALIZATION To realize Cu/CuNi strips the active materials deposited on glass substrate Glass substrate is for good adhesion Depositions done at room temperature 100 w of input power by argon as discharge gas Deposition rate forCu and constantan .1nm/s 22
  23. 23.  Siox protective layer to coat thermocouple Without exposing samples to air and environmental contaminations 2 step deposition is required for deposit Siox loyer The SiOx film can be deposited by using a plasma which is fed with constant tetraethoxysilane (TEOS),oxygen and argon flow rate of 1, 20 and 20 sccm respectively, at 5 Pa of pressure and 100 W of input power. The thickness in this case was selected to about 200 nm. 23
  24. 24. Fig. 4. The first prototype of inert thermocouple (ITC). The picture showsthree strips which are sputtered on a flat glass to form two thermocouples.The TCs are covered by a 185 nm layer of SiOx which is the responsiblefor the translucent aspect 24
  25. 25. Fig. 7. A FESEM image of the cross section of the constantan/SiOxinterface. The constantan thickness is of about 150 nm, while theSiOx layer has a thickness of about 185 nm. The SiOx protectinglayer appears quite compact so that a quite good protection shouldbe expected. 25
  26. 26. CONCLUSION An innovative way to create non invasive temperature sensor Temperature mapping can be obtained Accurate measurement 26
  27. 27. REFERENCES IEEE wikipedia 27
  28. 28. THANK YOU 28