Experimental and Numerical Study of Titanium Dioxide Agglomerates

Transcription

1 Experimental and Numerical Study of Titainum Dioxide Agglomerates S. Kozhar Hamburg University of Technology Institute of Solids Process Engineering and Particle Technology

2 Introduction Research objectives DFG-SPP 1486 Partikel im Kontakt - Mikromechanik, Mikroprozessdynamik und Partikelkollektive (PiKo) The aim of our project is to describe the mechanical interactions of finely dispersed particles with diameter of µm by using experimentally calibrated contact models PiKo B4 project Birkenfeld Setting up the measurement system Measurements of particle-particle and particle-wall contact interactions Capturing of the 3D shape of particles Hamburg Determination of materials parameters from experiments Selection and calibration of appropriate contact models for each material DEM/FEM-simulations of single particle and bulk material

3 Experimental set-up 20 mm Microscope Particle Force sensor Piezo drive Current set-up allows to carry out tests of particles at compressive shear and tensile loading with adjustable relative humidity and temperature in climate box Device Minimum value Maximum value Resolution Piezo drive 0 µm 250 µm 0.2 nm Laser vibrometer nm Force sensor mn mn 40 µn Box (Temperature) 15 C 35 C 1 C Box (Relative humidity) 10 % 90 % 2 %

4 Tested materials Titan dioxide particles elastic-plastic Hollow glass particle pure elastic Maltodextrin particles elastic-(visco)plastic

5 Tested material: Titania agglomerates (TiO ) Titania agglomerates TiO were produced by PiKo service project (OVGU) via the sol-gel process without heat treatment. Mechanical characteristics of TiO 2 particles measured by compression Parameter Unit Series 1 TiO 2 (IKTS) Series 2 TiO 2 (IMiP) Equivalent diameter [µm] 39 ± ± 23 Displacement at breakage [µm] 6.7 ± ± 1.6 Breakage force [mn] 98 ± ± 23 Breaking strain [%] 18 ± 12 5 ± 1 Compressive strength [MPa] 92 ± 68 9 ± 7 Young s modulus* [GPa] 3.3 ± ± 0.8

6 Tested material: Titania agglomerates (TiO ) Loading parameters of cyclic compression tests with TiO particles Loading regime A Loading parameter F max = 10 mn B C F max = 21 mn F max = 40 mn D F max,i = mn E F max,1 = 10 mn F max,2 = 20 mn F max,3 = 40 mn

7 Tested material: Titania agglomerates (TiO ) Examples of cyclic compression tests (regimes A, B and C) with TiO particles TiO particles behave elastic-plastically demonstrate cyclic hardening behavior

8 Tested material: Titania agglomerates (TiO ) Examples of cyclic compression tests (regimes C and D) with TiO particles TiO particles behave elastic-plastically demonstrate cyclic hardening behavior

9 Tested material: Titania agglomerates (TiO ) Modelling Average loading-unloading curve of TiO 2 particles in the saturation range approximated with contact models Comparison of the cyclic loading test of the TiO 2 particle with the modified contact model of Walton & Braun

10 Tested material: TiO A and TiO B New agglomerates from PiKo service project (OVGU) TiO TiO B TiO particles high stiffnes high level of SDS content dissimilar to TiO A TiO B particles optical similar to TiO production is dissimilar to TiO must be further investigated

11 Tested material: Titania agglomerates TiO B DSC, TGA and XRD analysis Einwaage 150 C 170 C 250 C 600 C 1000 C nach der Abkühlung [mg] Massenverlust [%] 22,82 ± 8,42 17,54 ± 3,2 17,74 ± 2,6 20,98 ± 1,3 23,07 ± 1,2 23,13 ± 1,5 23,59 ± 0,6 Temperatur der ersten endothermen Spitze [ C] (Entwässerung) Temperatur der zweiten exothermen Spitze [ C] amorph-kristallin (Anatas) Temperatur der dritten exothermen Spitze [ C] kristallin (Anatas)-kristallin (Rutil) 19,70 ± 2, ± ± ± 51

12 Tested material: Titania agglomerates TiO B Compression test Comparison with agglomerates TiO Kennwert Einheit TiO TiO B Äquivalentdurchmesser [µm] 102 ± ± 25 Bruchweg [µm] 5,0 ± 1,6 4,2 ± 2,1 Bruchkraft [mn] 74 ± ± 22 TiO TiO B

13 Tested material: Titania agglomerates (TiO B) Comparing of cyclic compression tests with TiO and TiO B TiO TiO B TiO B particles behave elastic-plastically demonstrate cyclic hardening behavior

14 Tested material: Titania agglomerates (TiO B) Comparing of cyclic compression tests with TiO and TiO B TiO TiO B TiO B particles behave elastic-plastically demonstrate cyclic hardening behavior

15 Real particle shape Spherical particle under compression Simulation of particles with a real shape XMT-Messung STL-Oberfläche Erstellung des Multi- Sphäre-Partikels für DEM- Software (EDEM) Erstellung des Agglomerates für DEM-Software (MUSEN) Erstellung des Volumenmodells für FEM- Software

16 Real particle shape Spherical particle under compression Simulation of particles with a real shape Particle properties E = 0.61 GPa = 0.28 = 2451 kg/m³ e n (Particle-Wall) = 0.3

17 Conclusions and Outlook Known parameters From experiments and measurements compressive strength and breakage strain equivalent restitution coefficient (TiO 2 -Steel ) static friction coefficient (TiO 2 -Glass) sliding friction coefficient (TiO 2 -Glass) agglomerate density From literature Poisson s coefficient Adjustable parameters E-Modulus / contact stiffness Needed (unknown) parameters E-Modulus / contact stiffness at loading/unloading equivalent restitution coefficient (TiO 2 -TiO 2 ) static/sliding friction coefficients (TiO 2 -TiO 2 ) adhesion torsion Future work: 1. Experiments with a bulk 2. Freefall experiments 3. Cooperations with other PiKo-groups

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