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Akimi4 [234]
3 years ago
10

You are investigating surface hardening in iron using nitrogen gas. Two 5 mm thick slabs of iron are separately exposed to nitro

gen environments at 850°C and 950°C, respectively. Both situations have achieved a steady-state diffusion condition. The concentration of nitrogen at the higher pressure surface at each temperature is 4 kg/m3 . What is the concentration of nitrogen on the lower pressure surface of each slab slab given that the diffusion flux is 9.0 x 10 -8 kg/(m2 *s)?

Engineering
1 answer:
Luden [163]3 years ago
4 0

Answer and Explanation:

The explanation is attached below

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An FCC iron-carbon alloy initially containing 0.20 wt% C is carburized at an elevated temperature and in an atmosphere wherein t
weeeeeb [17]

Answer:

the  temperature T at which the treatment is carried is out is  1274.24 K

Explanation:

Fick's second Law posits that the rate of change of concentration of diffusing species is directly proportional to the second derivative of the concentration.

Using the expression of the Fick's second Law:

\mathbf{\frac{C_x-C_o}{C_s-C_o} = 1- erf(\frac{x}{2\sqrt{Dt} })}

where;

C_o = initial concentration

C_x = the depth of the concentration

C_s = surface concentration

erf(\frac{x}{2\sqrt{Dt} })} = Gaussian error function.

Let variable z be used for the expression of the Gaussian error function.  erf(\frac{x}{2\sqrt{Dt} })}

Then, from the above equation:  replacing C_x with 0.35 ; C_o  with 0.2 and C_s  with 1.0; we have:

\mathbf{\frac{0.35-0.2}{1.0-0.2} = 1- erf( z)}

erf (z) = 0.8125

we obtain the error function value close to 0.8125 from the error function table and we did the  interpolation to obtain the exact value of variable  corresponding to 0.8125.

The table below shows the tabular form of the error function value close to 0.8125 .

Value for z                                                   Value for erf (z)

0.9                                                                0.797

z                                                                    0.8125

0.950                                                            0.8209  

From above; we can find  the value of variable  corresponding to the error function 0.8125 .

i.e

\frac{z-0.9}{0.95-0.9} =\frac{0.8125-0.797}{0.8209-0.797}

z = 0.932

However, the temperature dependence relation for the diffusion coefficient D can be expressed as:

z = \frac{x}{\sqrt{Dt} }

where;

z = 0.932

x = 3.5 mm = 0.0035 m

t = 50 h = 180000 sec

0.932 = \frac{0.35}{2\sqrt{D*180000} }

D = 1.958*10^{-11} m^2/s

Finally, the temperature T at which the treatment is carried is out is calculated as:

\mathbf{D=D_o \ exp \ (-\frac{Q_d}{RT}) }

From the table ‘Diffusion data’, we  obtain the values of temperature-independent pre exponential and activation energy for diffusion of carbon in FCC Fe.

D_o = 2.3*10^{-5} \ m^2/s

Q_d = 148, 000 \ J/mol

Replacing all values needed for the above equation; we have:

1.958*10^{-11}= (2.3*10^{-5})exp(\frac{-148,000}{(8.31)T})

8.51*10^{-7}=exp(\frac{-17,810}{T})

In(8.51*10^{-7})=(\frac{-17,810}{T})

-13.977 = -17,810/T

T = -17,810/ - 13.977

T = 1274.24 K

Hence, the  temperature T at which the treatment is carried is out is  1274.24 K

5 0
3 years ago
Why might a hospital patient prefer to interact with a person instead of robot?
MrMuchimi
A person would prefer to be able for the doctor/ nurse to visually see their symptoms and the problem, which a robot can not do, which would lead to a misdiagnosis
7 0
3 years ago
Write SQL queries to answer the following questions: What are the names of the course(s) that student Altvater took during the s
amm1812

Answer:

See explanations

Explanation:

Consider the following Venn diagram to retrieve the name of course that student Altvater took during semester I-2015.

• In above Venn diagram inner Ellipse represent the subquery part, this subquery part select the Student ID from STUDENT table.

• Second sub query is used to determine the SectionNo of all student whose studentID retrived in the first subquery

• Finally the main query displays the CourseName from COURSE table.

6 0
3 years ago
In the situation shown below, what would the Moon look like from Earth? Sun, Earth and Moon Four Moon Views A. View A B. View B
Blababa [14]

Answer:

where is the picture?

Explanation:

3 0
3 years ago
If i build thing a and thing a builds thing b did i build thing b
postnew [5]

Answer:

<h3>Yes</h3>

Explanation:

If you build thing "a" and thing "a" builds thing "b" you <u>indirectly</u> build thing "b".

3 0
3 years ago
Read 2 more answers
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