MATERIAL SCIENCE AND METALLURGY

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14 Νοε 2013 (πριν από 3 χρόνια και 4 μήνες)

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MATERIAL SCIENCE AND METALLURGY

5 MARKS

1.History

See also:

History of ferrous metallurgy
,

Chalcolithic
,

Bronze Age
,

Iron
Age
,

Metallurgy in Pre
-
Columbian America
,

Metallurgy in pre
-
Columbian
Mesoamerica
,

and

History of metallurgy in the Ind
ian subcontinent

The first evidence of human metallurgy dates from the 5th and 6th
millennium

BC, and was found in the archaeological sites
of

Majdanpek
,

Yarmovac
and

Plocnik
, all three in

Serbia
. To date, the earliest
copper smelting is found at the

Belovode

site,
2

these examples include a copper
axe from 5500 BC belonging to the

Vinča culture
.
3

Other signs of human
metallurgy are found from the third millennium

BC in places
like

Palmela

(Portugal),

Los Millares

(Spain), and

Stonehenge

(United Kingdom).
However, as often happens with the study of

prehistoric

times, the ultimate
beginnings cannot be clearly defined and new discoveries are continuous and
ongoing.

Silver
,

copper
,

tin

and meteoric

iron

can also be found native, allowing a limited
amount of

metalworking

in early cultures. Egyptian weapons made from meteoric
iron in about 3000 BC were highly prized as "Daggers from Heaven".
4

However, by
learning to get copper and

tin

by heating rocks and combining those two metals
to make an

alloy

called

bronze
, the technology of metallurgy began about 3500
BC with the

Bronze Age
.

The extraction of

iron

from its ore into a workable metal is much more difficult. It
appears to have been invented by the

Hittites

in about 1200

BC,
beginning
the

Iron Age
. The secret of extracting and working iron was a key factor in the
success of the

Philistin
es
.
4
5

Historical developments in ferrous metallurgy can be found in a wide variety of
past cultures and

civilizations. This includes the ancient and medieval kingdoms
and empires of the

Middle East

and

Near East
, an
cient

Iran
, ancient

Egypt
,
ancient

Nubia
, and

Anatolia

(
Turkey
),

Ancient Nok
,

Carthage
,
the
Greeks

and

Romans

of ancient

Europe
, medieval Europe, ancient and
medieval

China
, ancient and medieval

In
dia
, ancient and medieval

Japan
, amongst
others. Many applications, practices, and devices associated or involved in
metallurgy were established in ancient China, such as the innovation of the

blast
furnace
,

cast iron
,

hydraulic
-
pow
ered

trip hammers
, and double acting
piston

bellows
.
6
7

A 16th century book by

Georg Agricola

called

De re metallica

describes the highly
developed and complex processes of mining metal ores, metal extraction and
metallurgy of the time. Agricola has
been described as the "father of metallurgy".
8


2.Extraction

Extractive metallurgy

is the

practice of removing valuable metals from an

ore

and
refining the extracted raw metals into a purer form. In order to convert a
metal

o
xide

or

sulfide

to a purer metal, the ore must
be

reduced

physically,

chemically
, or

electrolytically
.

Extractive metallurgists are interested in three primary streams: feed,
concentrate (valuable metal oxide/sulfide), and

tailings

(waste). After mining,
large pieces of the ore feed are broken through crushing and/or grinding in order
to obtain particles small enough where each particle is either mostly
valuable or
mostly waste. Concentrating the particles of value in a form supporting
separation enables the desired metal to be removed from waste products.

Mining may not be necessary if the ore body and physical environment are
conducive to

leaching
. Leaching dissolves minerals in an ore body and results in
an enriched solution. The solution is collected and processed to extract valuable
metals.

Ore bodies often contain mor
e than one valuable metal. Tailings of a previous
process may be used as a feed in another process to extract a secondary product
from the original ore. Additionally, a concentrate may contain more than one
valuable metal. That concentrate would then be pr
ocessed to separate the
valuable metals into individual constituents.


3.Etymology

Main article:

Chemistry (etymology)

The word

chemistry

comes from the word

alchemy
, an earlier set of practices that
encompassed elements of chemistry, metallurgy, philosophy, astrology,
astronomy, mysticism and medicine; it is commonly thought of as the quest to
turn lead or another common starting material into gold.
8

The word

alchemy

in
turn is derived from the

Arabic

word al
-
kīmīā (
ءاي مي ك لا
). The Arabic term is
borrowed from the Greek
χημία

or

χημεία
.
9
10

This may have

Egyptian

origins.
Many believe that al
-
kīmīā is derived from χημία, which is in turn derived from
the word

Chemi

or

Kimi
, which is the ancient name
of

Egypt

in

Egyptian
.
9

Alternately, al
-
kīmīā may be derived from χημεία, meaning
"cast together".
11

An alchemist was called a 'chemist' in popular speech, and later the suffix "
-
ry"
was added to this to describe the art of the chemist as "chemistry".

Definitions

In retrospect, the definition of chemistry has changed over
time, as new
discoveries and theories add to the functionality of the science. Shown below are
some of the standard definitions used by various noted chemists:



Alchemy

(330)


the study of the composition of waters, movement, growth,
embodying,
disembodying, drawing the spirits from bodies and bonding the
spirits within bodies (
Zosimos
).
12



Chymistry

(1661)


the subject of the material principles of mixed bodies
(
Boyle
).
13



Chymistry

(1663)



a scientific art, by which one learns to dissolve bodies, and
draw from them the different substances on their composition, and how to
unite them again, and exalt them to a higher perfection (
Glaser
).
14



Chemistry

(1730)


the art of resolving mixed, compound, or aggregate bodies
into their principles; and of composing such bodies from those princ
iples
(
Stahl
).
15



Chemistry

(1837)


the science concerned with the laws and effects of
molecular
forces (
Dumas
).
16



Chemistry

(1947)


the science of substances: their structure, their
properties,
and the reactions that change them into other substances (
Pauling
).
17



Chemistry

(1998)


the
study of matter and the changes it undergoes
(
Chang
).
18


20 MARKS

1.The

modern definition of chemistry

Classically, before the 20th century, chemistry was defined as the science of the
nature of matter and its transformations. It was therefore clearly distinct from
physics which was not concerned with such dramatic transforma
tion of matter.
Moreover, in contrast to physics, chemistry was not using much of mathematics.
Even some were particularly reluctant to using mathematics within chemistry. For
example,

Auguste Comte

wrote in 1830:

Every attempt to employ mathematical methods in the study of chemical
questions must be considered profoundly irrational and contrary to the spirit of
chemistry.... if mathematical analysis should ever hold a prominent p
lace in
chemistry
--

an aberration which is happily almost impossible
--

it would occasion
a rapid and widespread degeneration of that science.

However, in the second part of the 19th century, the situation changed
and

August Kekule

wrote in 1867:

I rather expect that we shall someday find a mathematico
-
mechanical explanation
for what we now call atoms which will render an account of their properties.

After the discovery by

Ernest Rutherford

and

Niels Bohr

of the atomic structure in
1912, and by

Marie

and

Pierre Curie

of

radioactivity
, scientists had to change their
viewpoint on the nature of matter. The experience acquired by chemists was no
longer pertinent to the study of the whole nature of matter but only to aspects
related to the

electron cloud

surrounding the atomic

nuclei

and the movement of
the latter in the

electric field

induced by the former (see

Born
-
Oppenheimer
approximation
). The range of chemistry was thus restric
ted to the nature of
matter around us in conditions which are not too far (or exceptionally far)
from

standa
rd conditions for temperature and pressure

and in cases where the
exposure to radiation is not too different from the
natural
microwave
,

visible

or

UV

radiations on Earth. Chemistry was therefore re
-
defined as the science of matter that deals with the composition, structure, and
properties of substance
s and with the transformations that they undergo.
citation
needed

However the meaning of matter used here relates explicitly to substances
made of atoms and molecules, disregarding the matter within the atomic nuclei
and its nuclear reaction or matter within highly ionized plasmas. This does not
mean that chemistry is ne
ver involved with plasma or nuclear sciences or even
bosonic fields nowadays, since areas such as Quantum Chemistry and Nuclear
Chemistry are currently well developed and formally recognized sub
-
fields of
study under the Chemical sciences (Chemistry), but
what is now formally
recognized as subject of study under the Chemistry category as a science is always
based on the use of concepts that describe or explain phenomena either from
matter or to matter in the atomic or molecular scale, including the study of

the
behavior of many molecules as an aggregate or the study of the effects of a single
proton on a single atom, but excluding phenomena that deal with different (more
"exotic") types of matter (e.g. Bose
-
Einstein condensate, Higgs Boson, dark
matter, nake
d singularity, etc.) and excluding principles that refer to intrinsic
abstract laws of nature in which their concepts can be formulated completely
without a precise formal molecular or atomic paradigmatic view (e.g. Quantum
Chromodynamics, Quantum Electrod
ynamics, String Theory, parts of Cosmology
(see

Cosmochemistry
), certain areas of Nuclear Physics (see

Nuclear Chemistry
),
etc.). Nevertheless the field of chemistry is still, on our human scale, very broad
and the claim that

chemistry is everywhere

is accurate.


2.From fire to atomism

Arguably the first chemical reaction used in a controlled
manner was

fire
.
However, for millennia

fire

was simply a mystical force that could transform one
substance into another (burning wood, or boiling water) while producing heat and
light. Fire affected many aspects of early societies. These ranged from the most
simple facets of everyday life, such as c
ooking and habitat lighting, to more
advanced technologies, such as pottery, bricks, and melting of metals to make
tools.

Philosophical

attempts to rationalize why different substances

have different
properties (color, density, smell), exist in different states (gaseous, liquid, and
solid), and react in a different manner when exposed to environments, for
example to water or fire or temperature changes, led ancient philosophers to
postu
late the first theories on nature and chemistry. The history of such
philosophical theories that relate to chemistry, can probably be traced back to
every single ancient civilization. The common aspect in all these theories was the
attempt to identify a sm
all number of primary

elements

that make up all the
various substances in nature. Substances like air, water, and soil/earth, energy
forms, such as fire and light, and mo
re abstract concepts such as ideas, aether,
and heaven, were common in ancient civilizations even in absence of any cross
-
fertilization; for example in Greek, Indian, Mayan, and ancient Chinese
philosophies all considered air, water, earth and fire as

primary elements
.
citation
needed

Atomism

can be traced back to

ancient Greece

and

ancient India
.
2

Greek atomism
dates back to 440 BC, as what might be indicated by the book

De Rerum
Natura

(The Nature of Things)
3

written by the Roman

Lucretius
4

in 50 BC. In the
book was found ideas traced back to

Democritus

and
Leucippus
, who declared
that atoms
were the most indivisible part of matter. This coincided with a similar
declaration by

Indian

philosopher

Kan
ada

in his

Vaisheshika

sutras

around the
same time period.
2

In much the same fashion he discussed the existence of

gases
.
What Kanada declared by sutra, Democritus declar
ed by philosophical musing.
Both suffered from a lack of

empirical

data. Without scientific proof, the existence
of atoms was easy to deny.

Aristotle

opposed the existence of atoms in 330 BC.

Much of the early development of purification methods is described by

Pliny the
Elder

in his

Naturalis Historia
. He made attempts to explain those methods, as
well as making acute observations of the state of many minerals.


3.Technology

Virtual reality and
cyberspace

Virtual reality

(VR) is a term that applies to

computer
-
simulated

environ
ments
that can simulate physical presence in places in the real world, as well as in
imaginary worlds.



Reality
-
Virtuality Continuum.

The

Virtuality Continuum

is a continuous scale ranging between the completely
virtual, a

Virtuality
, and the completely real: Reality. The reality
-
virtuality
continuum therefore encompasses all possi
ble variations and compositions of real
and
virtual

objects. It has been described as a concept in

new media

and

computer
science
, but in fact it could be considered a matter of

anthropology
. The concept
was fir
st introduced by Paul Milgram.
21

The area between the two extremes, where both the real and the virtual are
mixed, is the so
-
called

Mixed reality
. This in turn is said to consist of
both

Augmented Reality
, where the virtual augments the real, and

Augmented
virtuality
, where the real augments the virtual.

Cyberspace
, the world's computer
systems considered as an
interconnected whole, can be thought of as a virtual
reality; for instance, it is portrayed as such in the

cyberpunk

fiction of

William
Gibson

and others.

Second life

and

MMORPGs

such as

World of Warcraft

are
examples of artificial environments or

virtual worlds

(falling some way short of
full virtual reality) in c
yberspace.

"RL" in internet culture

On the Internet, "
real life
" refers to life in the real world. It generally
references

life

or

consensus reality
, in contrast to an environment seen
as

fiction

or

fantasy
, such as

virtual reality
,

lifelike experience
,

dreams
,

novels
,
or

movies
. Online, th
e

acronym

"IRL" stands for "in real life", with the meaning
"not on the Internet".
22

Sociologists

engaged in the study of the Internet have
determined that someday, a distinction between online and real
-
life worlds may
seem "quaint", noting that certain types of online

activity, such as sexual
intrigues, have already made a full transition to complete legitimacy and
"reality".
23

The

abbreviation

"RL" stands for "real life". For example, one can
speak of "meeting in RL" someone whom one has met in a

chat

or on an
Internet
forum
. It may also be used to express an inability to use the Internet for a time
due to "RL problems".


4.From modal logic to philosophical tool

From this groundwork, the theory of possible worlds becam
e a central part of
many philosophical developments, from the 1960s onwards


including, most
famously, the analysis of

counterfactual conditionals

in
terms of "nearby possible
worlds" developed by

David Lewis

and

Robert
Stalnaker
. On this analysis, when
we discuss what

would

have happened

if

some set of conditions

were

the case,
the truth of our claims is determined by what is true at the nearest possible world
(or the

set

of nearest possible worlds) where the conditions
obtain. (A possible
world W
1

is said to be near to another possible world W
2

in respect of R to the
degree that the same things happen in W
1

and W
2

in respect of R; the more
different something happens in two possible worlds in a certain respect, the
"furt
her" they are from one another in that respect.) Consider this conditional
sentence: "If George W. Bush hadn't become president of the U.S. in 2001, Al
Gore would have." The sentence would be taken to express a claim that could be
reformulated as follows:
"In all nearest worlds to our actual world (nearest in
relevant respects) where George W. Bush didn't become president of the U.S. in
2001, Al Gore became president of the U.S. then instead." And on this
interpretation of the sentence, if there is some nea
rest world to the actual world
(nearest in relevant respects) where George W. Bush didn't become president but
Al Gore didn't either, then the claim expressed by this counterfactual would be
false.

Today, possible worlds play a central role in many debates

in philosophy,
including especially debates over the

Zombie Argument
,
and

physicalism

and

supervenience

in the

philosophy of mind
. Many debates in
the

philosophy of religion

have been reawakened by the use of possible worlds.
Intense debate has also emerged over the

onto
logical

status of possible worlds,
provoked especially by

David Lewis
's defense of

modal realism
, the doctrine that
talk about "possible worlds" is best explained in terms of innumerable,

really
existing

worlds beyond the one we live in. The fundamental question here
is:

given

that modal logic works, and that some possible
-
worlds
semantics for
modal logic is correct,

what has to be true

of the world, and just what

are

these
possible worlds that we range over in our interpretation of modal statements?
Lewis argued that what we range over are real, concrete

worlds

that exist just as
unequivocally as our actual world exists, but that are distinguished from the
actual world simply by standing in no spatial, temporal, or causal relations with
the actual world. (On Lewis's account, the only "special" property that
the

actual
world has is a

relational one: that

we

are in it. This doctrine is called
"the indexicality of actuality": "actual" is a merely

indexical

term, like "now" and
"here".) Others, such as

Robert Adams

and
William Lycan
, reject Lewis's picture as
metaphysically extravagant, and sugge
st in its place an interpretation of possible
worlds as consistent, maximally complete sets of descriptions of or propositions
about the world, so that a "possible world" is conceived of as a
complete

description

of

a way the world could be



rather than a

world that is
that way
. (Lewis describes their position, and similar positions such as those
advocated by

Alvin Plantinga

and

Peter Forrest
, as "
ersatz

modal realism", arguing
that such theories try to get the benefits of possible worlds semantics for modal
logic "o
n the cheap", but that they ultimately fail to provide an adequate
explanation.)

Saul Kripke
, in

Naming and Necessity
, took explicit issue with Lewis's
use of possible worlds semantics, and defended a

stipulative

account of possible
worlds as purely

formal

(logical) entities rather than either really existent worlds
or as some set of
propositions or descriptions.