Question

Q) The catalytic vapor deposition CCVD is one of the most important technique which applied to prepare various type of nanomaterial. These mate used in the production of various type of electronic devices on microscale .

Answer the following: (1) Explain the chemical vapor deposition process for preparing nanomaterials. (2) Make brief comparison between CVD and other conventional methods (3) One of the most important applications is the synthesizing silicon dioxide films which deposit with a uniform shape on substrate made of silicon wafers in the CVD reactor The input stream to the reactor at 25 °C consists of Silane and Oxygen in a ratio 6.0 to 1.0, respectively and the output product exit at 1102 degrees * C . SiH 4 (g)+O 2 (g) SiO 2 (s)+2H 2 (g) you can use the following data : ( Delta hat H f ^ ) SiH 4 (g) =-61.9kJ/mol , ( Delta hat H f ^ ) SiO 2 (s) =-851 kJ/mol (C p ) SiH 4 (g) [kJ/(mol* K)]=0.01118+12.2*10^ -5 T-5.548*10^ -8 T^ 2 +6.84*10^ -12 T^ 3 (C p ) SiO 2 (s) [kJ/(mol* K)]=0.04548+3.646*10^ -5 T-1.009*10^ 3 /T^ 2 Where the temperature in the heat capacity relation are applied in Kelvin .

Answer the following : ( a) Determine the amount in moles for the feed and the product taking 2m ^ 3 of gaseous as a basis to your calculations . Also , calculate the extent of reaction . ( b) Determine the standard heat of reaction using the heat of formation method and the heat of combustion method . (c) Determine the amount of heat absorbed or emerged from the CVD reactor . Is the given CVD reaction exothermic or endothermic ? (d ) Calculate rate of heat transfer in KW if you fed the reactor with 30m ^ 3 / h

Answer 1

1)The Chemical Vapour Deposition is one of the most popular technique for the production and synthesis of nanomaterials.This method is popular for large scale production and also a very simple, economic process.It is a vapour deposition method which uses chemical reactions at the surface of the required substance under high heating conditions.In this process,the substrate material is coated on the surface and the desired products are formed.Generally,these deposition process is carried out through pyrolytic decomposition of gaseous components.The chemical reactions do depend on the process parameters like pressure,temperature,composition of the catalyst which is used and concentaration.For the synthesis of nanomaterials the temperature range is 600 to 1200⁰C respectively.

2)The advantages of this CVD Process over the other conventional process are in this technique the reactants are present in the gaseous form so there are several advantages of the gaseous form whose characteristics plays a vital role.The other advantage is that this process is not a line of sight process.CVD Method can be widely used for coating of various metals,alloys,and also ceramic materials.This method is highly economic with high purity and efficiency.