Materials Science
Radius fillet gauges are typically made from hardened steel for durability and accuracy.
- Hardened Steel: This material is chosen for its ability to maintain its shape and resist wear over time, ensuring precise measurements.
Some gauges may also have a protective coating to prevent rust and corrosion, further extending their lifespan.
Fullerenes are a fascinating class of carbon allotropes with unique structures and properties. Here's a breakdown of their preparation and applications:
- Arc Discharge Method: This is the most common method. An arc is struck between two graphite electrodes in an inert atmosphere (like helium or argon). The intense heat vaporizes the carbon, which then cools and condenses into fullerenes, soot, and other carbon structures. (Source)
- Laser Ablation: A pulsed laser beam is focused onto a graphite target in an inert atmosphere. The laser ablates the carbon, forming a plasma that cools and condenses into fullerenes. (Source)
- Chemical Synthesis: While less common for large-scale production of C60, chemical synthesis methods exist for creating specific fullerene derivatives and smaller fullerenes. These methods often involve complex organic chemistry techniques.
- Soot Extraction: The soot produced by the arc discharge or laser ablation methods contains a mixture of fullerenes. These fullerenes are then extracted using organic solvents like toluene or xylene. The different fullerenes can then be separated using chromatography techniques.
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Materials Science:
- Reinforcement in Composites: Fullerenes can be added to polymers and other materials to improve their strength, stiffness, and toughness.
- Superconductors: When doped with alkali metals, some fullerenes exhibit superconductivity at relatively high temperatures.
- Nanotube Production: Fullerenes are used as seeds for the growth of carbon nanotubes.
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Medicine:
- Drug Delivery: Fullerenes can encapsulate drug molecules and deliver them specifically to target cells, reducing side effects.
- Antioxidants: Fullerenes can act as antioxidants, scavenging free radicals and protecting cells from damage.
- Photodynamic Therapy: Fullerenes can be used as photosensitizers in photodynamic therapy for cancer treatment.
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Electronics:
- Organic Solar Cells: Fullerenes are used as electron acceptors in organic solar cells, improving their efficiency.
- Transistors: Fullerenes can be used as active materials in transistors.
- Cosmetics: Due to their antioxidant properties, fullerenes are sometimes used in cosmetic products to protect the skin from damage.
- Catalysis: Fullerenes and their derivatives can be used as catalysts or catalyst supports in various chemical reactions.
It's worth noting that research into fullerene applications is ongoing, and new uses are continuously being explored.
A G.I. sheet, which stands for Galvanized Iron sheet, is coated with Zinc.
The process of galvanization involves coating iron or steel with a thin layer of zinc to protect it from corrosion.
Source: American Galvanizers Association - What is Hot-Dip Galvanizing?
Here's a description of a typical stress-strain diagram for mild steel under tensile load, along with explanations of its key points:
Image Source: Wikipedia
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Proportionality Limit (A):
This is the region where stress and strain are directly proportional, obeying Hooke's Law (Stress = E * Strain, where E is Young's Modulus). Up to this point, if the load is removed, the material will return to its original shape.
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Elastic Limit (B):
This is the point beyond the proportionality limit up to which the material remains elastic. If the load is removed before reaching the elastic limit, the material will still return to its original dimensions. However, beyond the proportionality limit, the stress and strain are no longer proportional.
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Upper Yield Point (C):
This point indicates the stress at which the material starts to deform plastically. It's the point where the material begins to yield significantly without any noticeable increase in stress.
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Lower Yield Point (D):
After the upper yield point, the stress drops down to the lower yield point. This is a more stable yield stress value and is typically used for design purposes. The material deforms plastically at this constant stress.
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Strain Hardening Region (D to E):
In this region, the material undergoes changes in its crystalline structure, resulting in increased resistance to deformation. To further stretch the material, more stress is required.
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Ultimate Tensile Strength (UTS) or Tensile Strength (E):
This is the maximum stress the material can withstand. Beyond this point, the material starts to neck down (localize deformation in a small area).
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Necking Region (E to F):
After reaching the UTS, the cross-sectional area of the specimen starts to decrease rapidly at a particular location (necking). The stress decreases as the material elongates further because the load is now being applied over a smaller area.
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Fracture Point (F):
This is the point where the specimen breaks or fractures.
Important Considerations:
- Ductile Material: Mild steel is a ductile material, meaning it can undergo significant plastic deformation before fracture. This is evident from the extended plastic region (D to F) in the stress-strain curve.
- Engineering Stress vs. True Stress: The stress-strain curve described above is based on engineering stress (load divided by original area). True stress (load divided by instantaneous area) is higher than engineering stress in the necking region.
The gamma (γ) form of iron, also known as austenite, is a high-temperature allotrope of iron with a face-centered cubic (FCC) crystal structure.
Key characteristics include:
- Crystal Structure: Face-centered cubic (FCC).
- Stability: Stable at high temperatures, typically between 912°C (1674°F) and 1394°C (2541°F). Substech
- Non-magnetic: Austenite is paramagnetic (non-magnetic). AZoM
- Solubility: Has a high solubility for carbon, which is important in the heat treatment of steels.
- Ductility: Generally more ductile and formable compared to other allotropes of iron at room temperature.
Austenite is crucial in the heat treatment processes of steel because its FCC structure allows it to dissolve more carbon than ferrite (α-iron). This property is utilized to manipulate the microstructure and mechanical properties of steel through processes like quenching and tempering.