Structure and Properties of Electrochemically Synthesized, - - PowerPoint PPT Presentation

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Structure and Properties of Electrochemically Synthesized, - - PowerPoint PPT Presentation

Jun 19, 2023 384 likes •709 views

Structure and Properties of Electrochemically Synthesized, Self-assembled, Functionalized Nickel Oxide Nanowires Y. Bhargava, S. Thorne, T.S. Mintz, T. Cohen-Hyams, Y. Suzuki, V. Radmilovic, and T.M. Devine Department of Materials Science and

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SLIDE 1

Structure and Properties of Electrochemically Synthesized, Self-assembled, Functionalized Nickel Oxide Nanowires

  • Y. Bhargava, S. Thorne, T.S. Mintz, T. Cohen-Hyams,
  • Y. Suzuki, V. Radmilovic, and T.M. Devine

Department of Materials Science and Engineering University of California, Berkeley

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SLIDE 2

Electrochemically Synthesized NiO Nanowires

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SLIDE 3

Overview

  • Discovery of Method of Synthesis
  • Structure and Composition
  • Four Factors Controlling Growth
  • Mechanism of Synthesis
  • Properties of Nanowires
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SLIDE 4

Oxidation of Alloy 600 in high temperature water (288°C)

Alloy 600 (Ni-16Cr-8Fe) PWR Primary Water 2 ppm Li + 1200 ppm B De-oxygenated with H2

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SLIDE 5

Conditions of Potential and pH

  • f Alloy 600 in PWR

Peter Scott

Oxidation of Alloy 600 in high temperature water (288°C)

Alloy 600 (Ni-16Cr-8Fe) PWR Primary Water 2 ppm Li + 1200 ppm B De-oxygenated with H2

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SLIDE 6

Conditions of Potential and pH

  • f Alloy 600 in PWR

Peter Scott

Potentials for growing Nanowires in pH 6.75

Oxidation of Alloy 600 in high temperature water (288°C)

Alloy 600 (Ni-16Cr-8Fe) PWR Primary Water 2 ppm Li + 1200 ppm B De-oxygenated with H2

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SLIDE 7

Oxidation of Alloy 600 (Ni-16Cr-8Fe) at high potentials (-25 mV vs SHE) in 288°C Water with 2 ppm Li + 1200 ppm B

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SLIDE 8

Samples in titanium autoclave with sapphire window

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SLIDE 9

SERS of Films Formed in Aqueous Solutions at 288°C

LASER

P . F . F

  • c

u s i n g O p t i c s

Spectrometer

C C D

Focus Lens N.F. Collection/ Collimation Lens

Samples Reference Electrode

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SLIDE 10
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SLIDE 11

Overview

  • Discovery of Method of Synthesis
  • Structure and Composition
  • Four Factors Controlling Growth
  • Mechanism of Synthesis
  • Properties of Nanowires
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SLIDE 12

Size of NiO Nanowires

10 20 30 40 50 60 1-5 15-20 30-35 45-50 60-65 75-80 90-95 105-110 120-125 135-140 Diameter (nm) Count

Mean diam = 25 nm Length = 25 µm

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SLIDE 13

AEM Data

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SLIDE 14

Composition of Nanowires

O 49% Fe 4% Ni 47% O Fe Ni

N = 15

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SLIDE 15

Nanowires are Single Crystals

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SLIDE 16

Overview

  • Discovery of Method of Synthesis
  • Structure and Composition
  • Four Factors Controlling Growth
  • Mechanism of Synthesis
  • Properties of Nanowires
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SLIDE 17

4 Factors Control Nanowire Formation

  • Composition of Aqueous Solution

– pH 6.75 => nanowires – pH 5.5 => no nanowires

  • Temperature

– 288°C and 238°C => nanowires – 25°C => no nanowires

  • Substrate Composition
  • Potential
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SLIDE 18

Substrate Composition

500nm 500nm 500nm

Alloy 600 (Ni-15.5a/o Cr-8a/o Fe) 70a/o Ni – 30a/o Cr Ni-20a/oCr-10a/o Mo

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SLIDE 19

4 Factors Control Nanowire Formation

  • Composition of Aqueous Solution

– pH 6.75 => nanowires – pH 5.5 => no nanowires

  • Temperature

– 288°C and 238°C => nanowires – 25°C => no nanowires

  • Substrate Composition

– 16Cr-8Fe; 30Cr; 20Cr-10Mo => nanowires – Pure Ni, Cr, Fe => no nanowires

  • Potential: oxidizing
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SLIDE 20

Overview

  • Discovery of Method of Synthesis
  • Structure and Composition
  • Four Factors Controlling Growth
  • Mechanism of Synthesis
  • Properties of Nanowires
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SLIDE 21

(2) -850 mV/1 hr

(1) -1600 mV/ 1 day

3 Step Process for Synthesizing NiO Nanowires

Alloy 600 (Ni-16Cr-8Fe) PWR Primary Water 2 ppm Li + 1200 ppm B De-oxygenated with H2

(3) -25 mV/0.5h - 4h

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SLIDE 22

3 Step Process for Synthesizing NiO Nanowires

(1) -1600 mV vs SHE @ 288°C remove air-formed oxide

Aqueous Solution

(2) -800 mV Form CrxOy (3a) > -600 mV Planar NiO

Alloy 600

(3b) -25 mV/4 h

Alloy 600 Alloy 600

NiO Nanowires

Aqueous Solution Alloy 600

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SLIDE 23

[Ni++] determines growth morphology of NiO

[OH-]EQUIL [Ni++]EQUIL Concentration Alloy 600 Distance into water [Ni++] > [Ni++]EQUIL NiO = nanowires [Ni++] > [Ni++]EQUIL NiO = planar

Ni++ + 2 OH- --> NiO + H2

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SLIDE 24

Growth of NiO Nanowires with Potentiostatic Conditions

Ni++ OH- [OH-] [Ni++]

Planar NiO NiO Nanowire Alloy 600 CrxOy

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SLIDE 25

Growth of NiO Nanowires with Dissolved O2

Ni++ O2 [O2] [Ni++]

Planar NiO NiO Nanowire Alloy 600 CrxOy

1/2 O2 + H2O + 2 e- --> 2 OH-

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SLIDE 26

Overview

  • Discovery of Method of Synthesis
  • Structure and Composition
  • Four Factors Controlling Growth
  • Mechanism of Synthesis
  • Properties of Nanowires
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SLIDE 27

Magnetic Properties: Methodology

  • SQUID magnetometer capable of measuring magnetic flux

caused by magnetic samples

– Can control applied magnetic field, temperature, and z-pos of sample

SQUID Rod

Straw Straw Stoppers Gel Tab Tape w/Nanowires Into SQUID

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SLIDE 28

Magnetic Hysterisis

Remnant Field: ~80 Oe Coercivity: ~0.03 emu/g

  • 0.30
  • 0.20
  • 0.10

0.00 0.10 0.20 0.30

  • 3000.00
  • 2000.00
  • 1000.00

0.00 1000.00 2000.00 3000.00 4000.00

Applied Field (Oe) Long Moment (emu/g)

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SLIDE 29

Growth of NiO Nanowires with Dissolved O2

Ni++ O2 [O2] [Ni++]

Planar NiO NiO Nanowire Alloy 600 CrxOy

RESULTS => Nanowires are electrically conductive

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SLIDE 30

Summary

  • Electrochemical method of synthesizing dense

arrays of self-assembled, functionalized, NiO nanowires (25 nm diam, 25 µm length)

  • Technique might be capable of synthesizing other
  • xide nanowires (e.g., FexOy and CorOs)
  • Growth of nanowires by cellular breakdown of

planar oxide/water interface

  • NiO nanowires are ferromagnetic and electrically

conductive

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SLIDE 31

EDS Results

6.66 3.47 37.14 36.28 191.47 189.39 6.91 10.62 RSD 3.14 2.55 1.41 2.03 0.20 0.27 3.38 2.21 STD 47.21 73.44 3.79 5.60 0.10 0.14 48.89 20.82 Avg

51.253 76.153 4.072 5.757 44.67 18.089 18 51.609 75.459 5.294 7.365 43.096 17.174 17 44.004 70.17 5.038 7.643 0.038 0.054 50.918 22.13 16 45.449 71.751 4.455 6.692 50.094 21.555 15 49.426 76.396 1.664 2.447 0.58 0.795 48.328 20.36 14 50.233 75.204 4.416 6.29 45.35 18.505 13 45.59 71.084 5.472 8.118 48.936 20.796 12 47.709 76.054 1.132 1.717 51.158 22.228 11 41.999 69.988 3.127 4.958 0.127 0.187 54.745 24.865 7 47.265 74.01 3.276 4.88 49.458 21.108 6 44.814 71.527 3.778 5.737 0.379 0.536 51.028 22.198 5

At % Wt % At % Wt % At % Wt % At % Wt % Ni Fe Cr O