Current assisted processing, including flash sintering

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1 Current assisted processing, including flash sintering Salvatore Grasso*, Theo Saunders, Elinor Grace Castle, Peter Tatarko, Mike Reece School of Engineering and Material Science, Queen Mary University of London, UK Jon Binner, Ji Zou School of Metallurgy and Materials University of Birmingham, UK Omar Cedillos-Barraza, Eugenio Zapata-Solvas, Samuel Humphry-Baker, William E. Lee, Centre for Advanced Structural Ceramics, Department of Materials, Imperial College London, UK Andrew Duff, Thomas Mellan, Michael W. Finnis, Department of Materials, Thomas Young Centre, Imperial College, London, UK Welcome to visit us:

2 Outline Flash sintering work - Overview of flash sintering and Electric Current Assisted Sintering - Flash sintering some examples: - Electrical conductors (ZrB 2, HfB 2 ) - Semiconductors (SiC, B 4 C) - Ionic conductors (3YSZ, 8YSZ) - Flash joining - Synthesis and recrystallization. (not enough time) MagMat (not just electric field) 2

3 Heating Elements Sintering powders Sintering powders Hot Pressing vs Electric Current Assisted Sintering (ECAS Die Pressure Supply Die Current Pressure Supply Punch Punch Hot pressing Undirected heating ECAS Directed heating Because of the direct heating mode, we cannot use in both cases the same approach to investigate the process.

4 Largest SPS in the world?? Machine size 12x 6x5 m 3 Sample size Ф> 40 cm 4

5 Automation for Industrial Applications What Dr Fritish about company. Say we want to sinter a 30 cm dimeter SiC disc, 1. Graphite die A and 3V. 2. Dieless 9V and A. 1. The heating speed is 100 C/min 2. The heating speed can be extreme C/min that is what flash sintering is about 5

6 What is flash sintering? 10 mm Flash Sintering of Nanograin Zirconia in <5 s at 850 C, Cologna et al., J Am Cer Soc,

7 Some definitions: What is FS? SPS Insulating Sample SPS Conductive Sample Flash-SPS Conductive Sample Sample current density <10A/cm 2 Sample current density A/cm 2 Sample current density >400A/cm 2 Review of flash sintering materials modelling and methods, Yu, Grasso et al. Advances in Applied Ceramics

8 Materials compositions: FS and glowers Nernst Glowers compositions ZrO 2 (Y 2 O 3 ), TiO 2, KAlSi 3 O 8, NaAlSi 3 O 8,MgO, Porcelain, Glasses, CaF(PO 4 ) 3,topaz, Ce 2 O 3, ThO 2, U 2 O 3, BeO, Y 2 O 3, Er 2 O 3, Nd 2 O 3, CaO, Co 2 O 3, Cr 2 O 3, SnO 2, ZnO, PbO, CaCO 3, CaSO 4 others (La 0.6 Sr 0.4 ) (Co 0.2 Fe 0.8 )O 3 /Gd 0.1 Ce 0.9 O 2 Ce 0.8 Gd 0.2 O 1.9 BaCe 0.8 Gd 0.2 O 3 δ Ce 0.8 Gd 0.2 O 1.9 Ce 0.9 Gd 0.1 O 1.95 Ce 0.8 Sm 0.2 O 1.9 YSZ 3YSZ 8YSZ Pure Y 2 O 3 Yu, Grasso et al. Advances in Applied Ceramics

9 Number of publications and sample size Dense ZrB 2 : φ 20 h 6 mm Dense SiC: φ 70 h 6 mm 20 Number of published papers Green dody: mm First paper, Cologna et al. 5 Submitted Jun Year Yu, Grasso et al. Advances in Applied Ceramics

10 FSPS processing of a wider range of materials system Reference ZrB 2 and HfB 2 J Am Ceram Soc 2014, 97, (8), SiC, pure and various additives B 4 C with or without graphene -Crystal Growth & Design 2016, 16, (4), J Am Ceram Soc 2016, 99, (5), Scientific reports 2016, papers in preparation + 2 papers in preparation NdFeB Journal of Magnetism and Magnetic Materials 2016, 417, Mg 2 Si Journal of Materials Chemistry C 2017, 5, (6), hbn TiB 2 Journal of the European Ceramic Society 2017, 37, (8),

11 Flash spark plasma sintering (FSPS) of pure ZrB2, J. Am. Ceram. Soc., 97 [8] (2014) Flash spark plasma sintering (FSPS) of α- and ß-SiC, J. Am. Ceram. Soc., 99 [5] (2016) Review of flash sintering: Materials, mechanisms, and modelling, Adv. Appl. Ceram., 2017 VOL. 116, NO. 1, Flash Spark Plasma Sintering (FSPS): far from equilibrium materials consolidation Structural materials 2014 (June) FSPS ZrB (June) FSPS α and β SiC Timeline of Flash Sintering work carried at Queen Mary University of London (QMUL) Functional materials 2015 (Dec) Contactless flash SiC and B 4 C 2016 (Jan) Electro-texturing 2016 (May) FSPS Nd -Fe-B magnets 2016 (Jul) FSPS hbn TiB (May) Review on Flash sintering 2016 (Aug) FSPS Mg 2 Si thermoelectrics 2016 (Aug) Flash Joining C f /SiC

12 A quick summary PRESSURE TEMPERATURE From 100 MPa To 1 C From 2100 C To 2500 C Nano WC fully dense C binderless Highest melting point material and HEC Heating rate From 100 C/min to C/min Flash work -Ultrafast processing with heating rate of > C/minute. This greatly accelerate the sintering kinetics -Electrical fields effects not limited to joule heating -Electrochemical -Peltier - electroplasticity

13 (a) (b) Development of UHT (2500 ᵒC) and high pressure SPS (500 Ф 20 mm ZrB2 35 s Ф 20 mm SiC 17s Flash Sintered samples Ф 60 mm SiC 55 s (c) (d) Oxidation retardation by application of an electric filed Conditions of plasma formation Understand electric field effects in UHTC Large HfB 2 Ф 30 mm h 55 mm billets densified at QMUL and machined at ICL for Arc jet AFRL

14 Outline Flash sintering work - Overview of flash sintering and Electric Current Assisted Sintering - Flash sintering some examples: - Electrical conductors (ZrB 2, HfB 2 ) - Semiconductors (SiC, B 4 C) - Ionic conductors (3YSZ, 8YSZ) - Opening Up new opportunities - Flash joining MagMat (not just electric field) 14

15 Previous work on ZrB 2. No preheating! S Grasso et al. Journal of the American Ceramic Society 97 (8),

16 SPS Flash sintered samples (a) (b) (c) 10 s 1452 ᵒC 15s 1708 ᵒC 25s 2027 ᵒC 35s 2198 ᵒC Flash SPS SPS conventional Heating rate 5000 ᵒC/min 100 ᵒC/min Time duration 35 seconds minutes Energy consumption 0.2 kwh 4 kwh

17 SPS Flash sintered samples > 60 minutes < 35 seconds

18 Outline Flash sintering work - Overview of flash sintering and Electric Current Assisted Sintering - Flash sintering some examples: - Electrical conductors (ZrB 2, HfB 2 ) - Semiconductors (SiC, B 4 C) - Ionic conductors (3YSZ, 8YSZ) - Opening Up new opportunities - Flash joining - Synthesis and recrystallization MagMat (not just electric field) 18

19 SiC Experiments S Grasso et al. Flash Spark Plasma Sintering (FSPS) of α and β SiC, J. Am. Ceram. Soc., 1 10 (2016)

20 Experimental Set up: Need versatile preheating!! (a) Experimental set up used for FSPS of β SiC (10%wt B 4 C) materials in presence of a graphite felt. (b) The preheating of the sample is obtained with current flowing through the graphite felt. (c) The sintering of SiC is achieved by currents flowing through the SiC sample. 20

21 Experimental Set up Photograph of (a) sample (β SiC (10%wt B 4 C)) embedded inside a graphite felt ring. (b) punches/graphite felt/sample assembly. (c) FSPS set up before FS. (d) Photographs of S1-4 samples. The displacement (mm) as recorded by SPS furnace and relative density are given. Figure 2 21

22 Sample temperature animation (ᵒC) Felt 22

23 Sample temperature Heating rate approaching ᵒC/minute (a) 2 mm (b) (a) Simulated temperature distribution (axial symmetric view) inside the S4 SiC sample (β SiC (10%wt B 4 C)) at time instant 47 s. (b) The simulated sample temperature (sample centre its mid thickness) are plotted along with measured SPS power as function of time. 23

24 Evidence of high temperature >2300 C (a) 2300 ᵒC, 30 s S4 (b) 10 µm 10 µm 5 µm Fracture surfaces of β SiC (10%wt B4C); (a) refers to the reference sample sintered at 2300 ᵒC for 30 s and (b) sample S4 24

25 7 m Getting more power -a pressing force of 50 to 2500 kn a working temperature of up to 2200 C (max. temperature of the die up to 2400 C). -Combined heating power 1 MW 25

26 Ф 60 mm the largest FSPS sample ever produced so far 1 pound coin Ф 22.5 mm Photograph (a) of the obtained α SiC crack free sample with diameter of 60 mm is shown (RD=98%). SPS recorded data (b) during FSPS performed on a hybrid SPS machine which allowed preheating of the sample by using induction heating. SPS power, displacement (piston travel), temperature measured by the top pyrometer are plotted. 26

27 Outline Flash sintering work - Overview of flash sintering and Electric Current Assisted Sintering - Flash sintering some examples: - Electrical conductors (ZrB 2, HfB 2 ) - Semiconductors (SiC, B 4 C) - Ionic conductors (3YSZ, 8YSZ) - Flash joining - Synthesis and recrystallization. (not enough time) MagMat (not just electric field) 27

28 Title: MagMat Materials Engineering in Magnetic Fields (MagMat) Research topic: Set up a versatile, wide-bore, high field (15T) magnet and to build supporting stages for materials synthesis and processing in magnetic fields. The objective of research is to enable, in the UK, technologies based on Materials Engineering in strong Magnetic fields and to accelerate a wide range of multidisciplinary research driven by the need of UK manufacturing for new and innovative process. Partners (UK): 20 UK university as in the expression of interest Duration: 5y (started May 2015) Total budget: 0.7 M Type of funding: UK, EPSRC, Capital Equipment funding Key Staff: S. Grasso, MJ Reece

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30 What is about? Texturing of dia/paramagnetic materials. Texturing can be 1,2 and 3D Gao, Suzuki, Grasso, Sakka, Reece J eu cer soc (6), Thinking of many processing techniques in SMF. + Slip casing Freeze casting EPD Thermo magnetic processes?? Arcs??

31 Conclusions Flash work -We can achieve bulk heating rates well above C/min, because of this we are likely to make new materials. Design materials properties by modulating electric fields. -Rapid heating seems to accelerate densification - The FSPS can promote and maintain defects during sintering. Defect Genomics. -Flash process in the material induce a clearly non equilibrium features. There are great potentials for industry: Nanostructured and metastable materials both for functional and structural application The process allows design of grain boundary (doping, vacancies and mis-orintation) Production rates and energy saving surpass greatly other techniques

32 200 nm Grant No. EP/K008749/1 (Material Systems for Extreme Environments)

33 Overview of the research Multidisciplinarity Step 1 Green presintering Cold press Step 2 Preheating Felt induction Step 3 Sintering Configs. I/V, pressure Time, etc. Step 4 Understand relationships parameters microstructures Colloidal chem. Ceramics Sintering Theory Microscopy Power electronics Mechanical testing Thermography Physics Colloidal route Arc Controls and probing Properties Electro chemistry Plasmas FEM Data logging