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Plasma deposited thermocouple
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Plasma deposited thermocouple

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  • 1. SHAHINA P.AS8 EIROLL NO:61 1
  • 2. CONTENTS INTRODUCTION TEMPERATURE MEASUREMENT LYOPHILIZATION PROCESS PRINCIPLE OF FREEZE DRYING PROBLEMS OF FREEZE DRYING PROPOSED SYSTEM PLASMA SPUTTERED TC REALIZATION CONCLUSION 2
  • 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. 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. 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. 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. 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.  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. 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
  • 10. GRAPHICAL REPRESENTATION OF FREEZE DRYING 10
  • 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. 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. 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. 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.  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.  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. 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.  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. •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. •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.  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. 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.  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. 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. 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. CONCLUSION An innovative way to create non invasive temperature sensor Temperature mapping can be obtained Accurate measurement 26
  • 27. REFERENCES IEEE wikipedia 27
  • 28. THANK YOU 28