Preparation of single crystals (process overview).pptx

Single crystals are essential for manufacturing the turbines and this is a brief presentation about how is it made

1. Preparation of Single Crystals

2. Presented by: Eng: Samy Ahmed Samy Eng: AbdulRahman Ahmed Eng: Islam Abubakr Eng: Hassan Reda Submitted to: Dr. Rania Under supervision: Dr. Mohamed Hafez

3. 1-Introduction to single crystals 2-Theoritical background 3-Methods of single crystals preparation 4-Case studies 5-Conclusion 6-References Contents

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8. 1-Introduction to single crystals *Hydrothermal Method* is a synthesis technique used in chemistry and materials science to produce crystals or materials under high temperature and pressure conditions in an aqueous solution. This method is widely used in the preparation of inorganic materials, such as zeolites, metal oxides, and nanomaterials, and can also be applied to organic compounds. Mechanism 1-basic principle The term “hydrothermal” refers to conditions involving high temperature (typically above 100°C) and pressure (above 1 atm), where water is used as a solvent 2 - *High Temperature and Pressure Conditions:* - Water in a conventional setting boils at 100° C at 1 atm pressure, but under pressure, its boiling point increases significantly

9. 1-Introduction to single crystals 3- *Nucleation and Crystal Growth:* - The hydrothermal method is often used to grow crystals, especially in the case of minerals and inorganic compounds. The process begins when the solute (usually metal salts, metal-organic compounds, or other precursors) is dissolved in the water under the high-pressure conditions. 4 - *Role of the Solvent (Water):* - Water in the hydrothermal method plays a crucial role as a solvent and reaction medium. Its high polarity facilitates the dissolution of various solutes (especially inorganic salts) and helps in the transport of ions or molecules to the growing crystal sites. 5 - *Precipitation and Crystal Formation:* - As the temperature of the system is gradually lowered, the solubility of certain compounds decreases, and they precipitate out of solution to form crystals 6 - *Reactions in Hydrothermal Synthesis:* Several types of reaction 7 - *Control Over the Morphology of Crystals:* The morphology of the crystals synthesized through the hydrothermal method can be controlled by adjusting several parameters:

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11. 1-Introduction to single crystals * Chemical Vapor Deposition (CVD) * is a widely used technique for producing thin films, coatings, and sometimes three-dimensional structures of materials. It is primarily used in the semiconductor industry, as well as in the fabrication of materials for electronics, optics, and other advanced applications. The process involves the deposition of solid material from a gaseous phase onto a heated substrate. Mechanism 1. *Introduction of Precursor Gases:* - The CVD process begins by introducing a mixture of precursor gases into a reaction chamber. These precursor gases typically contain the elements or compounds that will form the solid material (e.g., silicon, carbon, metals, or oxides). 2 - *Flow of Precursor Gases:* - The gases are introduced into the reaction chamber, and their flow is controlled through mass flow controllers. The flow of precursor gases typically occurs under a low-pressure environment, and the chamber is maintained at a specific temperature.

12. 1-Introduction to single crystals 3- *Gas Activation (Decomposition):* - As the precursor gases enter the reaction chamber, they are subjected to a variety of conditions that promote their decomposition or chemical reaction. This can be achieved through different methods 4 - *Adsorption of Reacted Species on Substrate:* - Once the precursor gases have been decomposed, the reactive species (atoms, radicals, or ions) travel towards the heated substrate. - These reactive species adsorb onto the surface of the substrate, where they may form bonds with the atoms or molecules already present on the surface, creating the beginning of the film. 5 - . *Surface Reactions and Nucleation:* - At the surface of the substrate, the adsorbed reactive species undergo surface reactions. These reactions may involve the formation of chemical bonds between the precursor species and the atoms on the surface of the substrate. 6 - *Film Growth (Deposition):* - The solid material (the thin film) continues to grow on the substrate as more precursor species are deposited and react on the surface. This process leads to the accumulation of the film layer by layer, building up the desired thickness.

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