Application of Nanostructured powders synthesized by new ......Reduced powder (200C/1h+700C/1h) Mechano-thermochemical method(I) Burnt out powder, Two-reduction step KIMM Korea Institute

1

2003. 10

Byoung-Kee Kim

Korea Institute of Machinery and Materials,

Application of Nanostructured powders synthesized by new chemical processes

Characteristics of Nanopowder Materials

KIMM Korea Institute of Machinery and Materials

- Enhanced catalytic properties- Enhanced absorption ability- Capilary Condensation

- Enhanced catalytic properties- Enhanced absorption ability- Capilary Condensation

Surface Effect

- Appearance of New Phases- Decrease of Melting Point- Polycrystallization of Single Crystal- Enhanced Scattering Effect of Waves

- Appearance of New Phases- Decrease of Melting Point- Polycrystallization of Single Crystal- Enhanced Scattering Effect of Waves

Bulk Effect

- Electric and heat transfer - Compressability- Solid state reactivity

- Electric and heat transfer - Compressability- Solid state reactivity

Interaction between Nanopowders

~3As6As10NiCatalytic Property

(As : standard Activity)

700℃~200℃~1000℃200220

NiW

SinteringTemperature

20mK2.0mK100AgHeat Transfer

3.4K5.3K90AlTransition

Temperature ofSuperconductivity

2~5%95%100AuLight Absorption(6~10㎛)

1300K430K

933K370K

3040

AuIn

MeltingPoint

~470Oe1030Oe50FeMagneticProperty

Micro-materials

Nano-materials

Size(Å)MaterialsProperty

2

Application Field of Nanopowder Materials


ElectronicOptical

ElectronicOptical MagneticMagnetic

StructuralStructural OthersOthers

◆ Optoelectronic devices◆ Passive electronic

devices◆ IC substrate◆ Thermistor and varistor◆ Piezoelectric actuators◆ CMP

◆ Advanced tones◆ Diagnostic contrast agents◆ Ferrofluids◆ Magnetic Recording◆ Magnetic Refrigerator

◆ Cutting tool ◆ Die

◆ Coating

◆ Abrasive components

◆ Catalysts◆ Chemical sensors◆ Energy storage devices◆ Pigments◆ Membranes

Research of Nanopowders in KIMM


Chemical Sensor, Membranes, Filter, TiO2 photocatalystsChemical/Catalytic

Materials

Thermistor, Varistor, Piezoelectric actuator Cu-Al2O3 electrode, W-Cu heat sink

Electric/Electrode Materials

Ferrofluid, Magnetic refrigerator, Recording media, Hard/Soft Magnets, Fe/Co magnetic materials, Nd-Fe-B hard magnet

Magnetic Materials

Abrasives, Cutting tools, CMP, Wear-resistant componentsWC-Co hard materials

Tool Materials

MaterialsArea

3

Mechanical Properties of WC/CoMechanical Properties of WC/Co

Chemical compositions(contents of Co)Particle size of hard phase(WC)Homogeneity of WC/Co (mean free path)

Chemical compositions(contents of Co)Particle size of hard phase(WC)Homogeneity of WC/Co (mean free path)

Reduction of WC size Decrease of mean free pathReduction of WC size Decrease of mean free path

Hardness Compressive StrengthTRS Strength Wear Resistance

Hardness Compressive StrengthTRS Strength Wear Resistance

Key for high mechanical properties Fabrication of very fine WC Higher homogeneity of WC and Co phases

Key for high mechanical properties Fabrication of very fine WC Higher homogeneity of WC and Co phases


Manufacturing of WC/Co AlloysManufacturing of WC/Co Alloys

APT powder

Calcinations

Reduction

Carburization

Milling(+C)

Milling(+Co)

W, Co metalorganics

Evaporation/Carburization

WC, WC-Co

W,Co chlorides

Spray drying

Reduction/Carburization

Reduction/Carburization

Milling(+C)

Removal of Chlorides

Solid Phase Process Liquid Phase Process Gas Phase Process

G.S. > 300nm G.S. > 100nm

G.S. < 30nm

Korea Institute of Machinery and MaterialsKIMM

4

Temperature(℃)400 800 1200

W2(C,O)

W

W2C

WC

H2/He

He

HeH2/HeH2/CH4

H2/CH4

20nm

10nm

• low pressure(10-3atm)• size: 5nm• low pressure(10-3atm)• size: 5nm

Tem

pera

ture

(℃)

Concentration of Methane

WC

WC+W2C

W2C + W

WC +W2C+ W

Low C

High C

800

1000

1200

1400

sccm 20 40 60 80 100 120 140

Total : 600sccm

n-WC powder n-WC powder


Coating of n- WC,Co powder

Carbon coating WC powder

• WC powder: 4nm• WC powder: 4nm

4nm

Oxide coating Co, Fe powder

• Core(metal)/Shell(Oxide) •Oxide shell : 3nm)• Core(metal)/Shell(Oxide) •Oxide shell : 3nm)

5 nm

Fe

Fe oxide

Co

Co oxide

0 200 400 600 800 1000100

104

108

112

116

Co oxidationWei

ght C

hang

e(%

)

Temperature(oC)

WC(C:10.5%)/CVC WC(C:5.78%)/CVC WC-10Co/TCP Taegutech


5

10 9 8 7 6 5

0

100

200

300

400

500

600

700

Loa

d(kg

f)

Displacement(mm)

10nm-1.0% 10nm-2.0% 100nm-1.0% 100nm-2.0%

2.23.09100nmC

1.852.02100nm(granule)B

0.7718.420nmA(NRL)

A.D.(g/cm3)

BET(m2/g)

Power sizetype

Compactabilityof n-WC powderCompactabilityof n-WC powder

Compact desity 47%

Rearrange of particles


Sinterbility of n-WC/Co powder

Solid sintering temp.

• WC(20nm)+Co(20nm) : 835oC• WC(20nm)+Co(100nm) : 890oC• WC/Co(100nm) : 1010oC• WC/Co(200nm) : 1070oC

• WC(20nm)+Co(20nm) : 835oC• WC(20nm)+Co(100nm) : 890oC• WC/Co(100nm) : 1010oC• WC/Co(200nm) : 1070oC

835oC

890oC

1010oC1070oC

835oC

890oC

1010oC1070oC

20nm→2㎛( x 100)

100nm→1㎛( x 10)

WC/Co(20nm)

WC(20nm)/Co(100nm)

WC/Co(200nm)

WC/Co(100nm)

• sintering temp: WC size(1070→835oC)Co size (890→835oC)

• abnormal grain growth (100 times,)Grain growth inhibitors


6

Plasma sintering/grain growth inhibitorPlasma sintering/grain growth inhibitor

WC-10Co-0.6VCround, 70nm( x 4)

WC-10Co-0.6VCround, 70nm( x 4)

WC-10Cofacetted shape 1㎛ (x 50)

WC-10Cofacetted shape 1㎛ (x 50)

Conventional WC-10Co

Nano. WC-10Co

• High Dislocation Density• Stacking Faults

• Dislocation free WC grains• Twins in WC grains

Plasma sintering


Properties of Nanostructured WC-Co Alloy

>1.0㎛

7

Nano sized Fe and Co Magnetic Materials


Magnetic Fluid : Magnetite(Fe3O4)

Saturation Magnetization of Fe = 2 times of that of Fe3O4Coercivity ; proportional to inverse of particle size (Hc = a+b/D)

Synthesis of nano-sized Fe ⇒ High performance magnetic fluid materials( Saturation Magnetization : 1500emu/cm3, Coercivity : 3000Oe)

Development of Fe based nanopowder for magnetic fluidsby Chemical Vapor Condensation

Development of Fe based nanopowder for magnetic fluidsby Chemical Vapor Condensation


KIMM30 35 40 45 50 55 60 65 70 75 80Co nanoparticles (fcc-type)

Fe nanoparticles (bcc-type)

Inte

nsity

(arb

. uni

t)

2 θ

CoFe

CoreCrystalline Fe

CoreCrystalline Fe Shell

Crystalline Fe oxides

ShellCrystalline Fe oxides

Microstructures of Fe Nanoparticles

5 nm

8


KIMM-10 -8 -6 -4 -2 0 2 4 6 8 10

(d)

(c)

(b)

(a)

Rel

ativ

e Tr

ansm

issi

on

Velocity (mm/s)

Samplesα -Fe(%)

Bulk Middle

Super-paramagnetism

(%)Fe3O4(%)

Mean size(nm)

(a) 2 0 98 0 5.39(b) 20 5 75 0 ~7.0(c) 34 24 21 21 10.32(d) 70 0 10 20 ~12.0

Superpara- Ferro-Ferro-Superpara-

(a) (b) (c) (d)

Superpara-

Ferro-

Mössbauer spectroscopy of Fe nanoparticles


KIMMCoreCrystalline Fe-Co

CoreCrystalline Fe-Co

ShellCrystalline Fe and Co oxides

ShellCrystalline Fe and Co oxides

Twin structureTwin structure

Microstructures of Fe-Co nanoparticles

9


KIMM30 35 40 45 50 55 60 65 70 75 80

Carrier gas: Ar + 6%O2

Carrier gas: He

Carrier gas: Ar

2 θ

BCC Co+ HCP CoBCC CoBCC Co

++ HCP CoHCP Co

BCC CoBCC CoBCC Co

Co oxideCo oxideCo oxide

Phases of Co nanoparticles with carrier gases


KIMMDifferent phases with different Co contentDifferent phases with different Co content Saturation magnetization reaches

highest value near 40 wt% CoSaturation magnetization reaches

highest value near 40 wt% Co

10 15 20 25 30 35 40 45 50 55 6020

40

60

80

100

120

M

s (e

mu/

g)

Co content3 0 4 0 5 0 6 0 7 0 8 0

2θ

Inte

nsity

(arb

. uni

t)

F e -4 7 C o

F e -5 0 C o

F e -4 0 C o

F e -3 4 C o

F e -1 0 C o

F C C -F e (C o )

B C C -F e (C o )

Phases and saturation magnetization

10

Nanostructured TiO2 photocatalytic materials


Decrease of particle size- Improved UV scattering- Enhanced photocatalytic activity- Improved gas sensing property- Enhanced opto-electronic property

Synthesis of nano sized TiO2 powders by Chemical Vapor Condensation process (Non-Agglomerated 10nm powder)


KIMMMicrostructure of Nano-sized TiO2 Powder

Anatase Rutile

20 25 30 35 40 45 50 55 60

Inte

nsity

2θ

size : 10nmloose agglomeratesphases : Anatase + Rutile (

11


KIMMPhase Change Depending on Powder Size

[100] zone axis(110) type planes

Anatasea=3.75Å, c=9.51Å

Anatasea=3.75Å, c=9.51Å Rutile~60nm

Rutile~60nm

Nanostructured W-Cu heat sink materials


Poor sinterability due to the negligible solid solubility between W and Cu

Conventional Process- Infilteration : Low thermal & electric conductivity

due to the addition of sintering activator- Liquid phase sintering : Low properties due to larger W sizeDevelopment of new process to achieve high density nanostructured W/Cu materials, using nanostructuredpowder (W : 60nm)

12

Microstructures of W/Cu Alloys

Mixing methodW:0.51%, Cu:20%

Thermochemical method(W-20wt%-0.5wt%Co)

Mechano-thermochemical method(II)Reduced powder (200C/1h+700C/1h)

Mechano-thermochemical method(I)Burnt out powder, Two-reduction step


Sinterabilty of Nanostructured W/Cu Powders

1000 1100 1200 130020

30

40

50

60

70

80

90

100

Green density

Sintering density Burnt out powder (process I) Reduced powder (process II) Metal mixed powderGreen density Burnt out powder Reduced powder Metal mixed powder

Cu melting pointGreen density

Rel

ativ

e de

nsity

(%)

Sintering temperature (oC)


13

Comparison of Thermal Properties

7.257.887.806.5

(6.8-7.6)5.4

(6.0-7.0)8.0(8.1-8.9)6.5 (7.2-8.0)

ThermalExpansionCoefficient(ppm/K)

221.3245.8233.0170

(180-210141

(180-210242

(180-210207

(180-210)

ThermalConductivity

(W/mK)

223.2223.2223.2300.0294.5240.1223.2Specific

Heat(J/Kg·K)

15.16-L14.85-T

15.43-L15.17-T

15.48-L15.17-T

9.819.8914.6315.94Density(g/㎠)

W-20CuKIMM750-4

W-20CuKIMM700-8

W-20CuKIMM700-8

Mo-20CuThermkon

-70M

Mo-15CuThermkon

-65M

W-20CuThermkon

-83

W-20CuThermkon

-76


Prospect of Nanopowder Materials


Thin Films

Electro-opticalDevice and

Ferroelectrics

SuperhardMaterials

Drilling, Miningand Machine

Tools

ProtectiveCoatings

TransportationEnergy, Chemical

Industries

AdvancedNanocomposites

EnergyAnd Aerospace

Industries

Ceramics Cermet Metals

5 10 15Years

Documents

Application of Nanostructured powders synthesized by new ......Reduced powder (200C/1h+700C/1h) Mechano-thermochemical method(I) Burnt out powder, Two-reduction step KIMM Korea Institute