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表面与界面化学

表面与界面化学试卷(a)2005

1.① surface tension: Surface tension is defined as the force acting at right angles to any line of unit length on the liquid surface or surface tension is the work required to increase the area of a surface isothermally and reversibly by unit amount. (3 points)

②CMC: CMC is the concentration above which micelle formation becomes appreciable. (3 points)

③solubilisation: Surfactant solutions above the CMC can solubilise otherwise insoluble organic material by incorporating it into the interior of the micelles. This is known as micellar solubilisation. (3 points)

④interface: The point, area, or surface along which two substances or other qualitatively different things meet. (3 points)

⑤coverage: a measure of the extent of adsorption of a species onto a surface. Usually defined as ? ? N / N m , Where Nads is the number of adsorbate atoms per unit area and Nm ads

is the number of atoms adsorbated per unit area to produce one complete layer on the surface. (3 points)

⑥unit mesh: the unit cell of a two-dimensional surface structure. (3 points)

⑦surface atom density: the number of atoms per unit surface area。 (3 points)

⑧surface activity: The strong adsorption of such materials at surfaces or interfaces in

the form of an orientated monomolecular layer is termed surface activity.

(3 points)

2. (1) (a) Intercepts: a,a,?.

(b)Reciprocals: 1/a,1/a,0.

So the Miller index is (110). （5 points）

(2) the (110) face contains two atoms per unit cell. The

area of the (110) unit cell face is 21/2a2. So the face atom density Ns=2/(21/2a2)= 21/2/a2（5 points）

(3) the unit mesh is shown in the following figure as dashed lines. （5 points）

(4) The CN in a bcc crystal is 8 (2 points). So, we can estimate the value of the energy Eb required to break each M-M bond as Eb??Hv, where NA is the Avogadro number(2 4NA

points). If we were to separate the bulk and form two (110) planes each with Ns surface atoms, the two bonds would be broken per surface atom(2 points). The surface energy, ?, is therefore given by ?(110)?2EbNs?Hv22?Hv(2 points) ??2224NAa4NA?a

3. P/(V(P0-P))?104 (cm-3)

4.17 16.67

P/P0 0.04 0.2

The slop and the intercept are 0.0078125, 0.0001045 respectively. (3 points)

Vm=1/(0.0078125+0.0001045)=126.31 cm3 (3 points)

The specific sruface area

A=N0?Vm/m22400=6.02?1023?16.2?10-20?126.31/1.5/22400

=367m2/g (4 points)

4. Read off a number of pairs of values of pressure (P) and temperature (T) which yield the same surface coverage, (5 points) and then plot a line of ( ln P ) v's (1/T), the slope of which yields the adsorption heat. (5 points)

5. (1)In spreading wetting, the contact angle should be zero. (2 points)

For adhesion wetting, the contact angle should less than 180 degree (2 points)

For immersional wetting, the contact angle should less than 90 degree (2 points)

(2)glyceryl monostearate. (3 points)

6. The real space overlayer structures for c(2?4) and (1?2) are shown in the Fig.(a) and Fig.(b), respectively.

(a) (3points) (b) (3points)

Pd atoms

O atoms

The corresponding LEED patterns are shown as Fig (c) and Fig.(d)

Pd spots

O spots

7. (1) the work of adhesion Wa= ?w+?O-?wO=72.8+21.8-50.8=43.8mN m-1 (4 points)

(2) the work of cohesion for n-octane Wc=2?O=2?21.8=43.6 mN m-1(2 points)

the work of cohesion for water Wc’=2?w=2?72.8=145.6 mN m-1(2 points)

(3) the initial spreading coefficient of n-octane on water

S=?w-(?O+?wO)=72.8-(21.8+50.8)=0.2 mN m-1(4 points)

表面与界面化学试卷(a)2007

1.①surface tension: Surface tension is defined as the force acting at right angles to any line of unit length on the liquid surface or surface tension is the work required to increase the area of a surface isothermally and reversibly by unit amount. (3 points)