課程名稱︰材料科學
課程性質︰必帶
課程教師︰宋家驥
開課學院：工學院
開課系所︰工程科學與海洋工程學系
考試日期（年月日）︰2008/4/16
考試時限（分鐘）：180
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Midterm-exam
1.(a)briefly cite the main differences between ionic, covalent, and metallic
bonding.
(b)state the pauli exclusion principle.(8pt)
2.what type of bonding predominates in (a) metals (b) ceramics (c) polymers?
(5pt)
3.iron titanate, FeTiO3, forms in the ilmenite crystal structure which
consists of an HCP arrangement of O-2 ions. If the ionic radius of Fe2+,
Ti4+,O2- is 0.077, 0.061, and 0.140nm respectively. (a)which type of
interstitial site will the Fe2+ ions occupy? why?(4pt) (b) which type of
interstitial site will the Ti4+ ions occupy? why?(4pt) (c) what fraction
of the total tetrahedral sites will be occupied?(1pt) (d) what fraction of
the total octahedral sites will be occupied?(1pt)
4.a sheet of BCC iron 1mm thick was exposed to a carburizing gas atmosphere on
the other side at 725度C. after having reached steady state, the iron was
quickly cooled to room temperature. the carbon constrations at the two
surfaces of the sheet were determined to be 0.012 and 0.0075wt%.
(a) iron has an atomic radius of 0.124nm, and an atomic weight of 55.85
g/mol. compute its density.(10pt)
(b)compute the diffusion coefficient if the diffusion flux is 1.4*10^-8
kg/m^2*s. the density of carbon is 2.25g/cm^3.(6pt)
5.polymers for engineering use can be classified as:
(a)thermoplastic,(b)thermosetting, and(c)elastomeric. Fill in the type ID
for each polymer listed in the following table. Answer example:I-a,II-b
(5pt)
name of polymer type ID
natural rubber I
polyethylene(PE) II
polyester(PET) III
phenol-formaldehyde(bakelite) IV
polyvinyl chloride(PVC) V
6.for both FCC and BCC crstal structures, there are two different types of
interstitial sites. in each case, one site is larger than the other, which
site is normally occupied by impurity atoms. for both FCC and BCC crystal
strcutures, compute the radius r of an impurity atom that will just fit
nto one of these sites in terms of the atomic radius R of the host atom.
(10pt)
7.For a bronze alloy, the stress at which plastic deformation begins is 275
Mpa, and the modulus of wlasticity is 115Gpa.
(a) what is the maximum load that may be applied to a specimen with a
cross-sectional area of 325mm^2 without plastic deformation?
(b)If the original specimen length is 115mm, what is the maximum length
to which it may be strentched without causeing plastic deformation?(10pt)
8.matching (a)isotactic,(b)syndiotactic,(c)atactic,(d)cis-,(e)trans- (5pt)
ANS Figure
I H H H H H R H H
c c c c c c c c
H R H R H H H R
II HHHHHHHH
CCCCCCCC
HRHRHRHR
III HHHRHHHR
CCCCCCCC
HRHHHRHH
IV CH3 CH2-
C===C
-CH2 H
V CH3 H
C===C
-CH2 CH2-
ANSWER example:I-a II-b...
the molecular structures above can be classified in to two schemes of
isomerism.fill in the corresponding molecular structures.(5pt)
Geometrical isomer:VI________ Stereo isomers: VII_________
9.determine the composition, in atom percent, of an alloy that consists
of 97wt% aluminum and 3wt% copper. (the atomic weight of copper and
aluminum is 63.55 and 26.98 respectively)(10pt)
10.for some applications, it is necessary to harden the surface of a steel
(or iron-carbon alloy) above that of its interior. One way this may be
accomplished is by increasing the surface concentration of carbon in a
process termed carburizing; the steel piece is exposed, at an elevated
temperature, to an atmophere rich in a hydrocarban gas,such as methane
(CH4).consider one such alloy that initially has a uniform carbon
concentration of 0.25wt% and is to be treated at 950度C. if the
concentration of carbon at the surface is suddenly brought to and
maintained at 1.20wt%, how long will it take to achieve a carbon content
of 0.80wt% at a position 0.5mm below the surface? the diffusion coefficient
for carban in iron at his temperature is 1.6*10^-11 m^2/s;
assume that the steel piece is semi-infinite.(10pt)
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