粉末冶金原理课件11制备

Powder

Metallurgy

PrinciplePowder

Metallurgy

Research

Institute2007Particle

Science

and

Engineering粉末冶金原理(课程分布)

40学时教学方式:

双语讲学

Chinese/English课程内容:

Part

I

Powder

fabrication

粉体制备

PartⅡ

Powder

characterization

性能How

do

the

powders

fabricate？Main

methods

to

fabricate

powdersWhat physic-chemical

phenomenon

could

beobserved

during

powder

fabrication？Which

method

is

suitable

to

sphere

particles？How

about

the

particle

morphologies？How

can

we

obtain

the

high

purity？What

takes

place

during

the

powder

fabri.?Which

condition

to

control

the

particle

size?What

can

we

do?

related

powder

makings.ContinuersWhat

are

the

microstructures

of

the

particles?What

is

the

apparent

density

of

the

powders?Which

equipment

can

measure

the

fine

particles?课时安排Talking

arrangements雾化制粉快速冷凝化学沉积电解制粉还原制粉Atomization

4hrsRSTRapidsolidification

4hrsChemistry

precipitation4hrsElectrical

fabrication

4hrsReduction

8hrs序言

Introduction

2hrsPartⅠ粉末制备28hrs机械研磨

Mechanical

grinding

4hrs参考书籍:ReferencesPowder

Metallurgy

Science粉末冶金原理 黄培云

P/M.

Principle考核成绩

Score

作业30%

卷面考试70%Part

Ⅱ4hrs粉末性能

12hrs颗粒结构Particle

microstructure

4hrs粒度分布Particlesizeanddistribution比表面

Specific

surface

2hrs考试

Testing

2hrs (closebook)What

is

Powder

MetallurgyPowder

metallurgyStudy

of

the

processing

of

metal

powders,including

the

fabrication,

characterization,and

conversionof

metalpowders

intousefulengineering

components.Studyofthe

basiclaws

andmechanisms

ofpowder

fabri.,

powder

compaction,sinteringand

surfacetreatments.R&D

ofnovel

materialsandproducts.Powder

MetallurgyProcessingpowderMicrostructureChemistryPackingSizeShapeFabricationtoolingprocessingMoldRollExtrudeSinterForgeHot

presstestingpropertiesDensityDuctilityMagneticStrengthConductivityMicrostructurePowder

Metallurgy

Processing粉末冶金材料和制品的工艺流程举例原料粉末其它添加剂热压松装烧结粉浆烧注混合压制等静压制轧制挤压烧结烧结预烧结烧缩浸渗

热处理

电镀高温烧结 复压 精整锻造 轧制

挤压 烧结锻打 复烧（浸油）热处理拉丝粉末冶金成品Reasons

for

using

powder

metallurgycostproecisionproductivityEconomic(example:automobilegears)Captiverefractoryreactive(example:tungstenlampfilaments)Uniquealloysmicrostructures(example:stainlesssteel

filters

)Ideal

Applications(example:poroustantalum

capacitors)Iron

and

steelAluminumCopperNickelTungstenStainiess

steelTin0.001

0.01

0.1

1Relative

ProductionThe

futureofpowdermetallurgyA

comparison

of

the

relative

production

for

somecommon

metal

powders,logarithmic

scale.High

volume

production

of

precise,

high

qualitystructural

parts

from

ferrous

alloys;Consolidation

of

high

performance

materials,where

full

density

and

reliability

are

primaryconcerns;Fabrication

of

difficulty

to

process

materials,where

fully

dense

high

performance

alloys

can

befabricated

with

uniform

microstructure;Further

considerations

1Further

considerations

2Economic

consolidation

of

special

alloys,

typicallycomposites

containing

mixed

phase;Synthesis

of

non

equilibrium

materials

such

asamorphous,

microcrystalline,

or

some

special

alloys;Processing

of

complex

parts

with

unique

ingredients(组元）or

uncommon

shapes.粉末冶金发展History

and

development

of

P/M历史部分:武器,生活用具,艺术建筑Weapon,

life

facilities,

arts-construction,

etc.现代部分:硬质合金,高温材料,汽车部件,军事工程Cement

carbide,

refractory

materials,

automobile

parts,equipments

in

defensive,

civilization

products,

etc.目前,

粉末冶金最发达的国家瑞典(Sweden)硬质合金工业非常发达Hoganess,

建立许多子公司,

Be

number

one其次是北美(North

American)和西欧(western

European)

。德国的粉末冶金工业也是处于世界前列-

工具钢.,tooling

steel.美国的粉末冶金公司主要产品用户是汽车制造商

producer，汽车工业auto

vehicle

industry发达，带动了

美国的粉末冶金工业发展，这是因为发达的汽车工业，大量a

huge

of

application

用粉末冶金部件。SametoAmerican，日本Japan的汽车工业的发展带动了粉末冶金工业发展。Different

to

China与中国不一样，the

western

countriesand

Japan西方或日本的粉末冶金工业是由两部分构成

conbined

by

two

part制粉公司：制备各种粉末：Companies

to

fabricate

andsupply

powders制品公司：买进粉末，制备零部件：Companiestofabricate

final

parts能够大量节约材料、lowcast无切削、lesscuting少切削，普通铸造合金切削量在30-50%，粉末冶金产品可少于

5%。Less

or

absent

cutting

machining.“Net

shaping”能够大量节省能源energy

saving能够大量节省劳动labor

saving能够制备其他方法不能制备的材料

specific

materialsand/or

products能够制备其他方法难以生产的零部件the

material

andpart

that

are

difficultly

to

be

produced

by

other

methods粉末冶金技术的优越性与局限性

advantages

and

limitation粉末冶金的特点particularly

points能生产用普通熔炼方法无法生产的具有特殊性能的材料；ability

to

produce

materials

which

cannot

be

produced

by

other

method.①

Porous

materials

and

products,

parts

within

lubricants②

Refractory

metals

such

as

tungsten,

molybdenum,

etc③

Pesudo-alloys,

such

as,

tungsten-copper

alloys④

Composite

materials,

such

as

316

ss

+

bioceramic⑤

Nano-crystalline,

sub-micrometer

crystalline

grain

metal⑥

Special

functional

materials

and

products,

such

asmagnetic

products,

supper

alloys

applied

in

airo-industry.Powder

metallurgy

disadvantages

and

limitationRather

lower

mechanical

properties,

for

their

pores

in

partsSize

and

morphological

limitation,

for

press

machine.Rather

lower

wrought

properties,

for

the

products

maycontain

oxide

that

induce

materials

brittle.Rather

small

industry

background

compared

with

castingand

conventional

materials

industry,

such

iron

and

steelproduced

on

big

scale.1+1>2,

new

materials

and

high

performancePowder

metallurgy

plus

conventional

material

processing粉末冶金新技术Novel

techniques

of

powder

metallurgy快速原形制备技术,RSP粉末注射成形、PIM快速冷凝技术获得非晶粉末、RST粉末溅射成形、powder

spray

forming机械合金化技术、MA温压成形技术,Worm

Comp.纳米粉末技术,Namo-Tech等静压成形-烧结技术,ISP-sintering高性能材料研发，等等.A

Interest

ComparisonMetal

powders:

109

kg/yearIndustry

minerals:

300

times

109

kg/yearCoffee,

tea,

and

tobacco:

1010

kg/yearPowder

metallurgy

is

a

prolonged

growth

phase;Iron

and

steel,

aluminum,

copper,

nickel,

andtungsten

are

the

main

consumption,

worldwide.Automobile

industryGear

partsMechanical

industryP/M

Industry

–200520032004Iron

&

Steel442,799473,804Stainless

Steel8,900

(E)9,350

(E)Copper

&Copper

Base22,63225,204Aluminum50,000

(E)50,000

(E)Molybdenum2,500

(E)2,600

(E)Tungsten3,000

(E)3,500

(E)Tungsten

Carbide5,263

(R)5,891

(R)Nickel10,057

(R)10,110

(R)Tin9351,077546,086

st*581,536

st*(E)

Estimate (R)

Revised*1st=0.9078mt铁基结构合金的高精度highprecise﹑高质量highquality﹑大数量产品。致密高性能材料，主要是理想的密度和牢固性full

density

andreliability。难加工材料的制造，difficulty

to

process

materials全密度具有统一微观结构的高性能合金。4）特殊合金，主要为包含有多相的组分multi-compositescontainingmixedphase，通过增强密度的工艺来制造。

These

will

often

be

fabricated

by

enhanceddensification.5）非平衡nonequilibrium材料的合成例如suchsamorphous非晶，micro-crystalline,or

metastable

alloys微晶和亚稳合金。6）具有独特组分或不常用形状的特殊附件的工艺。粉末冶金未来The

future

of

the

powder

metllurgy30,00025,00020,00015,00010,0005,00001990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004*1

st

=0.9087

mtP/M

Parts Other

Usesst*Copper

and

Copper

base

powder

in

North

AmericaCopper

and

copper-base

powder

in

2004

increased

11.3%

andcopper

powder

base

parts

increased

7%.International

iron

and

steel

powder

Metal

powder

in2004

increased

by

6.5%

to

527,918(mt),

figure

Ironpowder

increased

7%

over

2003

to

430,119mt.1000000900000800000700000600000500000400000300000200000100000Europe**JapanNorthAmericanSt**1st=0.907801994

1996

1998

2000

2002

2004**Reflects

P/M

grade

powders

only

Sourse:MPIF,JPMA,EPMAincludes

stainless

steels

after

1996International

copper

and

copper

basepowders

in

200410000200003000040000019942004Europe**JapanNorthAmerican*st60000500001996

1998

2000

2002**reflects

P/M

grade

powders

only*1st=0.9078source:MPIF,JPMA,EPMAP/M

parts

content

in

a

typical

vehicleNorth

AmericaJapanEurope19807.7kg(17lb)3.03kg(6.7lb)2.5kg(5.5lb)19858.6kg(19lb)3.78kg(8.3lb)19878.8kg(19.5lb)4.3kg(9.5lb)3.2kg(7lb)199010.9kg(24lb)5.55kg(12.21lb)4.1kg(9lb)199412.2kg(27lb)6.64kg(14.6lb)5.7kg(12.5lb)199512.7kg(28lb)6.7kg(14.8lb)6.1kg(13.46lb)199714kg(31lb)6.52kg(14.41lb)199814.9kg(33lb)6.65kg(14.6lb)7.02kg(15.5lb)199915.6kg(34.5lb)7.17kg(15.8lb)7.4kg(16.3lb)200016.3kg(36lb)8.2kg(18lb)200117kg(37.5lb)7.3kg(16lb)8.1kg(17.8lb)200217.7kg(39lb)7.6kg(16.7lb)8.3kg(18.3lb)200318.4kg(40.5lb)8.0kg(17.6lb)8.7kg(19lb)200419.5kg(43lb)9.0kg(19.8lb)North

America

copper

and

copper

base

powder*1

st

=0.9087

mtP/M

Parts Other

Usesst*30,00025,00020,00015,00010,0005,00001990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004Stainless

steel

powder

increased

5%

to

an

estimated8,488

mt.Tungsten

powder

increased

16%

to

3,177

mt

andtungsten

carbide

powder

increased

almost

12%.Although

there

are

about

10

companies

makingaluminum

P/M

parts,

two

players

dominated

the

marketin

North

America.European

iron

and

steel

powder

in

2004

fared

betterthan

North

America,

increasing

by

8.8%

to

172,952mt.Increases

in

iron

powder

in

Japan

did

not

match

NorthAmerica.Estimate

that

that

the

iron

powder

market

now

exceeds908，000mtImpact

of

ChinaIn

the

last

several

years,

China

poses

both

acompetitive

threat

and

potentially

huge

opportunity.It

has

an

estimated

680

P/M

part

makers,

but

onlyabout

five

of

these

are

considered

capable

of

makinghigh

quality

P/M

parts.The

Chinese

P/M

parts

industry

is

experiencing

anestimated

19%

annual

growth

rate.The

typical

passenger

car

in

China

contains

about4.7kg

of

P/M

parts.China

produced

about

85000mt

of

P/M

parts.Chinese

P/M

industry

will

undoubtedly

increase

itsquality

capability

as

more

funds

are

invested,particularly

by

Western

companies.Currentlyrepresentingmore

than

20

non-Chinesethe

U.S,

Europe,

Japan,

Korea,firmsandTaiwan

have

P/M

plants

in

China

mainland.On

the

other

hand,

China

is

beginning

to

impact

theEuropean

automotive

market,

selling

inexpensive

cars.Chapter

2

粉末制备方法Powder

fabrication

methods物理机械法Physic-Mechanical

Protocol机械研磨法制备粉末Milling高温雾化法制备粉末Atomization物理化学法制备粉末氧化物还原法制备粉末reduction

of

metallic

oxides气相沉积法制备粉末precipitation

from

atmosphere

phase液相沉积法制备粉末precipitation

from

liquid

phase电解法制备粉末electrolytic

fabrication

techniques

fromthe

electrode纳米及超细粉末制备技术nano/ultro

fine

powder

preparation从过程的实质来看，大体上可以归纳为两大类，即物理机械法mechanical和物理化学physio-chemical法粉末的生产方法很多，从工业规模industrialscale而言，应用最广泛pervasive

used

method的是还原法

reducing、雾化法和电解而气相沉淀法vapor

decomposition

和液相liquidprecipitation沉淀法在特殊应用时亦很重要。从材质范围来看typeofthematerials，不仅使用金属粉末、也使用合金alloying粉末、金属化合物粉末、ceramics；从粉末外形shape来看，要求使用各种形状的粉末，如生产过滤器时filter，就要求球形粉末；sphericalmorphology,

spherical

particles从粉末粒度来看，要求各种粒度的粉末，从粒度为500~1000um的粗粉末到粒度small

than0.1um的超细粉末superfine

powders。（1）从固态金属与合金制取金属与合金粉末的有机械粉碎法和电化腐蚀法；electricalerosion在固态下制取粉末的方法包括（2）从固态金属氧化物及盐类制取金属与合金粉末的有还原法；从金属和非金属粉末non-metallicpowders、金属氧化物和非金属粉末制取金属化合物粉末的有还原-化合法。

Reducing-chemistrycombined.（1）从金属蒸气冷凝制取金属粉末的蒸气冷凝法；

consolidationfrom

metal

steam在气态制备粉末的方法包括（2）从气态金属羟基物离解制取金属、合金以及包覆粉末的羟基物热离解法;

carbonyl

vapordecomposition。Coated

particles（1）从液态金属与合金制备金属与合金粉末的雾化法；（2）从金属盐溶液置换substitution和还原金属、合金以及包覆粉末的置换法

substitution、溶液氢还原法；liquidhydrogenreduction（3）从金属盐溶液

电解制金属与合金粉末的水溶液电解法

liquid

electrolytic；从金属熔盐电解制金属和金属化合物粉末的熔盐电解法。Meltsaltelectrolysis在液态下制备粉末的方法包括Chapter

3

机械研磨Mechanical

Milling利用机械力将金属或其它材料破碎制取粉末的方法应用非常Pervasive广泛:Suitable

for

脆性粉末制备Brittle

powders陶瓷粉末Ceramic

powder,碳钢Carbon

steel,陶瓷粉末:Hard

alloying

硬质合金;Mixing

and

Blending

混合及合批;机械能—粉末颗表面转化

Mechanical

E-Surface

E

Transformation缺点Disadvantages化学脏化chemicalContamination,dust,Oil油西方:高碳钢high

carbon

steels

and牙科粉末dental

powder银汞合金dental

amalgam

powder铝粉Aluminum

Powder机械夹杂Machining

Impurities最简单的方法(Simplest

method),最简单的设备

(Simplest

Equi.),

最有效(Most

effect)有方法之一.也是能量效能利用率低的方法,能量利用率<10%.Small

than

10%percentBalls

球MaterialsCyindrical

jar

球磨桶仅需要干dry湿wet研磨规律:Grinding

Mechanism球磨如图示过程:A

jar

mill

such

as

diagrammed

in

figure.(a)

Low

speed,

(b)

suitable

speed,

(

c)

high

rotation

speed至少有四种作用力在破碎粉末:冲击：Colliding剪切：Shearing压缩：Compressing磨研：Grinding这些都能形成破碎作用.Crush

Particles.那么破碎脆性brittle粉末所需要冲击colliding力应力与缺陷结构defect和裂纹扩展敏感程度相关.A

view

of

the

action

in

a

jar

mill,

the

impact

ofthe

falling

balls

grinds

the

material

into

powderSEM

of

milled

niobium

powder,prepared

by

hydriding,

milling,

and

vacuumdehydriding leading

to

an

angular

particle

shape公式:Crack

tip

radusCrack

propagation

扩展grinding

efficiency

is

regulated

by

ball

movement

includingcolliding，sliping，friction，compression.

粉末研磨综合有冲击,滑动,摩擦与压缩,研磨效果与球体运动方式相关d

=

(2Er

/

D)1/

2d

:冲击应力E:材料弹模.Elastic

Modalusr:缺陷尺寸.Defect.裂纹尖端曲率半径,裂纹扩展D:粉末尺寸.Partide

Size式表明:Large

particles

require

less

impact

stress

tofracture.粗颗粒粉末只需要小的冲击应力,随粉末颗粒直径变小,冲击应力增大.如果我们知道初始粒度(颗粒尺寸)initial

ParticleSize当要研磨到所需粒度时,需要多少能量可以由一个simplerelationship去估计(estimating)需要的能量.d

=(2Er

/

D)1/

2D1D22

1g:

一个常数

a

constanta:

指数

between

1

and

2这是一个经验工式, a--经验系数.球磨效应影响因素,Factors

to…干/湿. Dry/wet,

脆性/还原性

Brittle/Ductile,Plastic/Rigid粉末粒度Particle

Size球体尺寸Ball

Size旋转速度:Jar

Rotation

on

speed.W

=

g(D-a

-

D-a

)计算:一青铜粉末Boron

Powder

40um,5小时到

20

um,若磨到10um需要多少时间.假设一立方形纳米颗粒晶粒,晶界宽度Width约1.2nm,

如果该晶粒中有20%原子是处于晶界上,估计该晶粒Size.EstimateTotal

energy

change

during

milling由颗粒尺寸变化与总能关系:W

=

g(D-a

-

D-a

)f

iDf

研磨粒度;

Di初始粒度

a=2作业

1

、

复合粉末材料,

屈服强度(yieldingstrength)与第二相关系如下:求:第二相粉末为200nm时,材料的屈服强度,第二相为球形.Sphere

shape

powderParticle

size(mm)ds(MPa)6.4905.91183.61602.8186Decide

ball

的运动Jar

旋转速度最为重要.Behavior球体受力分析:suppose:

only

one

Ball

只有一个球的情况.P:离心力Centrifuge

ForceG:重力G

ForceP1:向心力

A1:临界点R:筒体半径V:

线速度A:

落点Falling

pointRotation

of

small

steel

ball

and

force

action球磨的基本规律Basic

regulation

of

mill球在滚筒中的基本状态转速慢，

泻落状态，摩擦效果grinding转速快，

抛落状态，摩擦,撞击破碎转速快，

抛落状态，撞击破碎colliding假设:we

supposethat只一个球，only

one

ball,球直径比桶直径小球受到两个力作用，Two

force

acting

on

the

ballP

：离心力centrifuge

forceG

：重力gravityV

：线速度linear

velocity

of

the

small

ball.球的受力分析在抛落点平衡时（A点）：二力相等，P＝P’，P

=

magm

=

Gv

2a

=RP

=

G

·

cosaG v

2• =

G

cosag

RP

=

ma

=v

2cosa

=gR所以Relation

of

linear

speed

and

rotate

speed

isv

=

2pRn

=

pRn60

30Force

action

on

the

small

steel

ball

include

centrifuge

andgravity

force,

suppose

only

one

ball

in

the

jar.Thus，

the

critical

rotation

speed

isp

2

Rn2cosa

=g

3022以g＝9.8m/s

代入得：n2

Rcosa

=900v

2cosa

=gR代入得临界状态

当转速加快，球不落下，球转到最高点A1点，此时在这临界状态下，a

=

0n

2

R=

cosa

=

1900转/分R

30

42.4Dn临界＝

=D，

the

diameter

of

thejarIn

fact，in

order

to

obtain

the

efficiency

ground

theexperienced

working

rotation

speed

should

lower

than

thecritical

speed，and

the

experienced

working

speed：工作经验表示：n＝0.6n临界时，可制取细粉fine

particlesn＝0.75n临界时，一般只能制取较粗的粉末coarse

particlesn

=

0.75n临界

=

0.75

·

42.4

/

D

=

32

/

D转/

分

1

D

18 24

d

£

1

~影响球磨效果的因素factors

to

influence

milling

efficiencya、球料比：ratio

of

powder

and

balls，一般粉末填满球体之间的间隙b、球体直径：diameter

of

the

balls选择范围c、研磨介质：medium

空气、protective

atmosphere

，lessen

oxidation，alcohol，

gas，avoiding

assemble（团聚）componentsegeration成分偏析，and

dust（粉尘飞扬）研磨介质:the

excellent

action

of

the

groundmedium：Protective.

Anti-干磨:保护气氛AtmosphereOxidation湿磨:保护和效率;wet

milling湿磨介质:水,乙醇等;milling

mediumwet

grind

split

湿磨尖壁作用,有利于裂纹扩展Crackpropagation减少泠焊.Decrease

cold

weldingIncreasing

the

grinding

efficiency如要产生Colliding

action

冲击作用Experienced

Relation，n实=0.7~0.75n临界如果要Colliding+Slipping

action，n实=0.6n临界Apart

from

above

factors.

There

are:球料比:Ball:Mater

ratio

:4:1~5:1装料比Filling

volume:0.4~0.5

packing球体直径:10~20mmJar

diameter:

300~500mm物料性质

future

of

the

grounding

particles脆性粉末破碎，Brittle

powder延性粉末，ductile

powder，精细分层，fine

lamination，and

cold

welding.Relation

of

powder

surface

area

and

ground

time

is

follow；Sm

粉末极限研磨后的比表面积S0

粉末研磨前的比表面积S

粉末研磨后的表面积,

t

研磨时间,

k

常数氧化铝、氧化锆、炭化硅、钛、镍等都符合这种关系=

ktln

Sm

-

S0Sm

-

S缺点，Disadvantages:Contamination

脏化,Limited

particle

size,Brittle

materials

脆性材料.例1.车削粉研磨a=2.(assumed)Vacuumed

milling8hrs

Di=300µm,Df=110

µm,if

milling

to

75

µm,how

many

hrs

are

needed?8

的1.33

folds,

10.6

hrs.强化球磨:Enhanced

grindinga.

机械合金化Mechanicalalloying

Stirredmill搅拌当球体冲击粉末,产生功能,功能越大,冲击力越大,导致粉末破碎。为了提高球的冲击速度,采用了机械合金化技术。The

input

material

goes

through

a

sequenceof

cold

welding

and

fracture

steps.

As

aconsequence

of

attrition,

the

microstructurebecomes

more

homogeneous

as

sketched

atthe

bottom

of

the

figure.A

view

of

mechanical

alloying

where

therotating

impeller

stirs

a

tank

filled

with

ballsd:

研磨介质(粉体)颗粒直径，粉体直径减少转速增大,时间减少。制备弥散强化。ODS Oxide

DispersionStrengthening

Alloys.

Ni

Base,

Co

Base

,

Fe

BaseSuper

alloys.

Oxide

Particles

Sub.

micrometer

亚微米粉末。Alloying

mechanism

合金化机理:

破碎与冷焊

Fractural/cold

welding导致均匀化homogenization研磨过程所需的能量与搅拌旋转时速度N相关:fit

=cd2

/N1/2

c:经验常数.empirical

Constant高能球磨(Mechanical

alloying

)并不在乎粒度减少,而在乎have

finer

microstructure.

精细结构,

产生复合材料.result

in

Composite

materials。Fe,

Co,

Ni

base

均为韧性ductile

材料,、航空材料、高温合金,

Super-alloys，要的是产生一个结构去达到性能.b.振动球磨Vibratory

Milling粉末靠冲击Colliding碰撞,提高单位时间内球体的碰撞次数,可提高破碎效果,特别是当磨到一定程度,只要小的碰撞,即可使粉末破碎。随着研磨的进行,

粉末平均粒度Mean

particle

size

减小,单位质量(单质体积)粉末表面积增加.

-比表面积:Specific

Surface

Area/per

unit

powder.单位时间内球体的总冲击数empirical

EquationR

:粉末比表面积w:振动频率Freauncyd:球直径d:粉末直径t

:研磨时间e

:振动ApiplinghyR

=f(w,e,d球,d粉,d粉,t)m

:单位时间球磨体总冲击数V:球角体积K:单位体积中球数量B:装填系数N:振动次数/minZ:转动一周球冲击数E:转动一周相邻冲击数m=

V·K·B·n·Z·E

次/minC.行星式球磨:增加球Colliding次数自转+公转Protective

Atmosphere机械合金化,搅拌:非晶,纳米晶,纳米particles,脆性,韧性金属,粉末振动球磨,破碎micrometer

grade纳米级,脆性粉末WC行星式球磨,纳米非晶粉末.研磨过程所需要时间与粉末性质相关。同样用比表面积表达:ln

=t:

milling

time，

k：constantSm：the

limitation

specific

areaSo：

the

initial

specific

areaSt：specific

area

at

t

time=

ktSm

-

S0Sm

-

Stm

t

mS

-S

=(S

-S

)e-ktSt

t时间specific

surface

area.0St

fi

Sm

,

t

›St

越接近SmGrinding

time

increasing.不同性质的粉末,从St

fi

Sm所需的时间不同.Powder

Metallurgy

PrinciplePowder

Metallurgy

Research

Institute2006Chapter

4.

氧化还原制粉方法Chemical

Fabrication.定义:用还原气体(固体)或活泼金属将氧化物还原制备粉末

的过程.(Reduction

of

Oxide

Decompose

of

a

solid

by

a

gas.)1.最简单地.反应平衡常数.Reaction

Equilibrium

ConstantK

=

PH

O

/

PH2

2气体的分压之比.Gas

partial

pressure

.(Ratio)FeO(s)

+

H2

(g)

fi

Fe(s)

+

H2O(g)FeO,Fe3O4,Fe的稳定存在与分压有关温度升高：Fe3O4

FeO

Fe反应速率J与反应过程活化能θ,反应温度T，气体分压比相关：J=Aexp（-θ/RT）A：物质常数，频率因子frequency

factor活化能降低，反应温度升高，提高反应速度，有利于还原进行；Metal

oxides

can

be

produced

by

H2

，

CO，

etc.O2+2H2=2H2OO2+2CO=2CO2O2+C=CO2WO3+H2=WO2+H2OWO2+2H2=W+2H2OTiCl4+2Mg=Ti+2MgCl2Reducing

agents (还原剂)a:

Gas

reducing

agents:

H2,

COb:

Solid

reductant:

C

,

metal,

alkaline

metals;The

necessary

conditions

as

reductant:还原剂对氧的亲和力大于对被还原物质的亲和力--热力学thermo-dynamic

必要条件,Only

fit

thenecessary

condition,

the

reaction

can

gothrough.DiscussionFor

a

close

system,

the

equilibrium

constant,energy,

determines

the

terminal

concentrationratio

of

the

products

to

reactants,For

the

reduction

of

WO3

by

H2,

the

equilibriumconstant

K

is

given

as,K=PH2O/PH2Where

PH2

and

PH2Oare

the

partial

pressure

ofhydrogen

and

water

steam金属物质对氧的亲和力affinity氧离解压Oxide

decomposition

pressureGoing

to

change

with

temperature，and

ingeneral，Temperature

increase，decomposition

pressure

will提高，亲和力

affinity

will

decrease.Thermo

–dynamics

热力学,必要条件.Necessary

ConditionsKinetic

–dynamics

动力学,充分条件.Complementary

condition2.还原过程基本原理热力学基本因素,必要条件,充分条件.(1)

还原过程标准Standard

free

energyX:还原剂. XO:金属氧化物. Me:还原金属.系统中温度一定,各物质离解压一定,通过各物质离解压不同,物质decomposedpressure越低,氧化物越稳定.还原反应化学式:MeO+X=Me+OX1.金属氧化物还原热力学条件

Thermodynamic

condition1）、还原过程标准等压位或自由能free

energy

(焓)的变化如果还原

反应的化学式为X-还原剂,Me-金属氧化物,XO-金属氧化物metaloxide每种氧化物都有各自的离解压，离解压越低，氧化物越稳定MeO有离解压，XO也有离解压decomposedpressure，前者离解压大于后者,MeO才能被X还原，他们的离解反应为：MeO

+

X

=

Me

+

XO(1)(2)上述金属氧化物还原过程标准自由能变化是即ΔZ

φ(2)

<ΔZφ(1)PO2(XO)

<

PO2(MO)2MeO

=

2Me

+

O2O2

(

MeO)DZ

(1)

=

-RT

ln

KP(1)

=

-RT

ln

P2

XO

=

2

X

+

O2O2

(

XO)DZ

(2)

=

-RT

ln

KP(2)

=

-RT

ln

P2DZf

=

1

(DZf(2)

-

DZf(1))

0The

higher

decomposed

pressure,

the

more

unstablethe

metal

oxide,

then

the

greater

the

free

energychange,

the

metal

oxide

will

be

reduced

byreductant.即XO离解反应标准自由能变化应小于MO离解

反应自由能的变化，这样XO才比MO稳定，这时，这时，XO的离解压小于MO的离解压，还原反应

正向进行。氧对X的亲和力大于对Me的亲和力，推广之，对氧的亲和力大于被还原的金属时，都可以作为该金属氧化物的还原剂。金属氧化过程标准自由能变化与温度的关系是：直线关系,截距A

表示在绝对零度

absolutetemperature:T=0时，形成该金属氧化物的自由能DZ

=

A

+

BTC的氧化反应都是随着温度的升高而有利于C的oxidation。Water生成反应的ΔZ°－T关系线在Cu、Co、Fe、Mo、等氧化物的生成线之下，在一定条件下，H2

能还原这些氧化物。In

practice,

the

reaction

system

pressure

equal

to

1,

the

partialpressures

of

PO2

and

PH2

are

small

than

1.DZ

＜0，当T上升,随温度难度增加上升C

+

O2

=

CO22C

+

O2

=

2CODZ

变的越负，即[DZ

]增大，从2H

2

+

O2

=

2H

2OThermo

–dynamic

热力学必要条件•••PMO

〉PXOPMO

=PXOPMO〈PXO还原反应进行反应达到平衡反应逆向进行，金属被氧化离解反应2MeO=2Me+O2DZ

（1）=

-RTlnkp

（1）=

-RTlnPO2（MeO）

（1）平衡常数kp（1）

=PO2（MeO）

（1），DZ

<0

反应进行2XO=2X+O2D

DZ

（2）=

-RTlnRp

（2）=

-RTlnPO2（XO）

（2）

D平衡常数kp（2）

=PO2（XO）

（2），DZ

<0

反应进行等温条件:平衡常数用离解压表示.T不变,以(1)-(2),并除以2,消除分数,得mol数,over/by

2(2)(1)(2)(1)2222(

m

)2

(

X

)=

1

[-

RT

ln

kp+

RT

ln

kp

]=

1

[-

RT

ln

PO+

RT

ln

PO

]M

eO

+

X

=

M

e

+

XO

Z

=

-

RT

ln

kp=

1

[

Z

-

Z

]Thermo-dynamiccondition：

ΔZ°

<

0ΔZ2°

<

ΔZ1°

，or还原剂离解压PO2（X）小于金属氧化物离解压PO2（M）根据离解压与反应过程自由能变量的关系，离解压越大，该物质越不稳定unstable，free

energy

changemore.

In

other

words,

XO离解反应change

of

standardfree

energy

is

小于MO离解反应change

of

standardfree

energy,

XO稳定,MO离解,反应向还原方向进行.碳的氧化反应,

2C+O2=2CO与金属氧化反应不同,温度升高,ΔZ°变得越负,表明温度升高,有利于上述C的氧化反应,CO在高温(elevatedtemperature)ismorestable.CO在高温的离解压很小,excellent

reducing

agent.2H2+O2=2H2O在很多金属Fe,

W,

Cu,

Co,

Ni,Mo氧化反应生成线(氧化反应自由能变化-温度关系曲线)之下,H2O的离解压小于这些金属氧化物离解压,H2O

比这些氧化物稳定,therefore,

H2

couldreduce

these

metal

oxides.

H2

,excellent

reductant.2）实际还原过程:实际还原过程在非标准线以下below

thestandard

line，即此时PO2

标准状态体系的分压等于1,如FeO用CO还原,即（1）-（2）得非标准状态22Fe

+

1

O

=

FeO2

22CO

+

1

O

=

COFeO

+

CO

=

Fe

+

CO2PDZ

=

DZ

＋RT

lnqCO2

CO＝DZ

+

RT

ln

P

PCO

CO2＝DZ

－RT

ln

P

PCO

CO2＝DZ

－4.57DT

ln

P

PPCO2qP

=

PCO（1）（2）即该还原反应与的分压有关, related

to例如reduction

reaction

of

tungsten

oxideWO2+2H2=W+2H2OΔZ=

ΔZ

°-2

x

4.576TlnPH2/PH2OΔZ’=2