Silicio. Materiales y materias primas.

Name: Silicio. Materiales y materias primas.
Uploaded: 2013-08-12T04:42:36.000Z
Duration: 56 min 48 s

Silicon: The Element That Changed Humanity

Introduction to Silicon

Silicon is a versatile material used in glass manufacturing, body implants, fertilizers, and microelectronics.

It has had a significant impact on humanity, particularly during the information age.

Abundance and Composition of Silicon

Silicon makes up about 20% of the Earth's crust and is the second most abundant element after oxygen.

Found in group 14 of the periodic table, silicon typically exists combined with oxygen as silicates or silicon oxides.

Historical Significance

Various historical figures from different eras have utilized silicon-related materials, including Stone Age humans and Aztec warriors.

Officially discovered in 1823, its use dates back to prehistoric times when early humans created tools from flint (silica).

Development Through Ages

Flint was crucial for developing civilization by enabling fire-making technology.

Obsidian was widely used for sharp tools like arrowheads by ancient tribes due to its glass-like properties.

Evolution of Understanding Silicon

Clay and glass are also silicon-based materials that have been used since ancient times.

Initially thought to be an element until 1787; it was later identified as an oxide compound.

The Properties of Silicon

Production and Characteristics

The first successful isolation of silicon occurred in 1823 by Swedish chemist Jöns Jacob Berzelius.

In 1854, Saint Claire Deville produced silicon through electrolysis.

Role in Electronics

Silicon's unique atomic structure allows it to function as a semiconductor essential for electronics and solar cells.

Atomic Structure Insights

Each silicon atom bonds with four neighboring atoms through shared electrons, creating a stable structure.

Conductivity Properties

While generally a poor conductor when bonded tightly, excitation (e.g., by sunlight photons) can free electrons to conduct electricity.

Applications of Silicon

Semiconductor Functionality

When excited, silicon acts as a conductor; otherwise, it behaves as an insulator—making it vital for microelectronics.

Types of Crystalline Structures

Microcrystalline: Crystals range from nanometers to micrometers.

Polycrystalline: Crystals approximately one centimeter in size.

Monocrystalline: A single crystal form that can be large (up to one meter long).

Amorphous vs. Crystalline Forms

Silicon: From Sand to Technology

The Importance of Silicon in Industry

Bangalore, with a population of 6 million, is the second industrial center in India and has a significant relationship with silicon due to its vast software industry.

The term "Silicon Valley" refers to California's region known for housing numerous tech companies since the 1960s, highlighting silicon's critical role in high technology.

Applications of Silicon Beyond Electronics

Silicon has various applications that do not require high-purity crystalline material; it is used in alloys, ceramics, glass manufacturing, and as an abrasive (silicon carbide).

Dioxide silicon is essential for concrete and brick production and plays a role in Portland cement manufacturing.

In agriculture, silicon serves as a fertilizer derived from primary mineral-rich sand.

Production Process of Silicon

The initial step involves converting sand into metallurgical-grade silicon by reducing silica dioxide with carbon at temperatures exceeding 3,000°C.

This process yields liquid silicon with 98% to 99% purity at a cost of $1-$2 per kilogram; however, only a tiny fraction is further purified for semiconductor use.

Purification Methods for High-Purity Silicon

Ultra-pure silicon can be obtained through physical or chemical methods. Physical methods exploit impurity solubility differences during solidification.

The Czochralski method involves melting one end of a silicon bar to gradually draw heat along it while allowing impurities to concentrate at the melted end.

Chemical Processes for Semiconductor Grade Silicon

Chemical methods target more easily purifiable compounds like trichlorosilane produced from metallurgical-grade silicon.

The Siemens process reduces trichlorosilane with hydrogen to recover high-purity semiconductor-grade silicon but requires significant energy input, raising costs to $60-$70 per kilogram.

Transitioning from Pure Silicon to Functional Devices

To create solar cells or integrated circuits efficiently, pure silicon must be transformed into crystalline form.

The most common technique for achieving this is the Czochralski growth method where molten silicon crystallizes around a seed crystal under controlled conditions.

Final Steps in Solar Cell Production

Controlled impurities are introduced during crystallization (doping), which tailors the properties of the resulting material.

Thin wafers (~300 microns thick), cut from cylindrical ingots containing doped silicone, are processed chemically post-cutting to remove surface damage before being fashioned into solar cells or electronic devices.

Historical Context and Evolution of Electronics

Silicon and Microelectronics: A Historical Overview

The Evolution of Transistors

The necessity for housing 10 million transistors in modern computers highlights the advancements in microelectronics.

An area of nearly 1,000 square meters represents the history of silicon and microelectronics; transistors developed in 1947 replaced early 20th-century vacuum tubes used in telephony and radios.

Vacuum tubes consumed significant energy, had fragile glass casings, and were bulky. The invention of transistors by three American physicists addressed these issues, paving the way for further innovations like integrated circuits.

Transistors utilize semiconductor materials such as silicon and germanium. Significant advancements occurred within a decade post-invention, leading to various types of transistors being developed.

In 1958, circuits were invented to couple transistors directly onto silicon wafers, marking the birth of integrated circuits.

Integrated Circuits and Their Impact

Commonalities among automobiles, cell phones, computers, and microwaves can be summarized with "IC" (integrated circuits); large-scale integration began in the 1980s with initial ICs containing only one transistor.

As technology progressed, more components were added to integrated circuits based on their level of integration: SSI (≤12 components), MSI (12–99), LSI (100–999), VLSI (10,000–99,999), and ULSI (≥100,000).

Microprocessors: The Brain of Computers

The microprocessor is an integrated circuit that processes information by tracking keystrokes and mouse movements through programs and operating systems; Intel's first microprocessor from 1971 contained about 2,000 transistors.

Modern microprocessor technology allows for over 200 million transistors per chip. Moore's Law states that transistor dimensions halve approximately every eighteen months since the early '70s.

Solar Energy Conversion

Various cultures have historically revered the sun due to its life-sustaining energy; since the 19th century efforts have been made to convert solar energy into electricity—culminating in photovoltaic technology reliant on silicon.

Early Developments in Solar Cells

Initial attempts at solar energy conversion faced commercial viability challenges until breakthroughs led to practical applications using silicon-based cells starting from a solid-state selenium cell created in 1876.

In 1953, a Bell Labs physicist discovered that specially treated silicon produced significantly more electricity than selenium when exposed to sunlight—this discovery spurred further research into photovoltaic conversion.

Advancements in Photovoltaic Technology

February 1954 marked a milestone with the announcement of the first solar cell capable of generating sufficient electricity for electrical equipment—a breakthrough reported by major media outlets like The New York Times.

By transforming solar energy directly into electricity without maintenance needs or reliance on battery storage capacity limitations encouraged researchers to explore solar cells as power sources for early spacecraft.

Space Applications of Solar Cells

Solar cells were first utilized on satellites in 1958 with Vanguard I employing six small silicon modules powering a germanium transistor signal received for over four years.

Telstar I became the first commercial communications satellite using silicon solar cells in 1962; efficiency improved from around ten percent in the '70s to approximately fifteen percent by late '80s. Today’s photovoltaic technology approaches thirty percent efficiency.

Space Technology and Solar Cells in Argentina

Launch of the Argentine Satellite

The Space Shuttle Endeavour launched an Argentine satellite, developed by the National Commission on Space Activities (CONAE). This satellite included a set of monocrystalline silicon solar cells manufactured at the National Atomic Energy Commission (CNEA), marking Argentina's first experiment with locally produced solar cells in space.

Development of Solar Cell Technology

The Solar Energy Group at CNEA has extensive experience in solar energy, particularly in photovoltaic conversion, which transforms sunlight directly into electricity using solar cells. They had the technology to manufacture these cells domestically.

CNEA collaborated with CONAE to place locally made silicon cells on an experimental satellite called SAC. This partnership was a significant challenge that they accepted enthusiastically.

Adapting Technology for Space Conditions

Transitioning from terrestrial to space applications required rapid adaptation of cell technology. They needed to ensure that panels could withstand harsh space conditions, as the lifespan of solar cells is affected by degradation due to proton and electron bombardment.

The design process involved ensuring that initial energy output exceeded requirements so that even after degradation over time, sufficient power would still be available for satellite operations.

Achievements and Future Directions

Argentina now possesses locally manufactured solar cells qualified for space use. This achievement instills pride as it demonstrates successful operation aboard a satellite.

Following this initial success, CNEA's Solar Energy Group is working with an interdepartmental team at the Constituent Atomic Center on developing solar panels for future national space missions.

Technical Aspects of Satellite Operations

Two silicon sensors were integrated into one of the solar panel designs for a mission called SAC-D Aquarius. These sensors measure radiation levels; if aligned correctly, they receive equal radiation signals.

The satellite employs a gyroscope system to maintain proper orientation of its solar panels based on sensor feedback regarding radiation equality between both sides.

Historical Context and Material Use

The first selenium solar cell was created in 1876 when man had not yet achieved sustained flight. Initially, silicon-based solar cells found their primary application in space after years of development.

Common materials used in photovoltaic cells include gallium arsenide and silicon. Differences exist between terrestrial and space modules primarily concerning environmental protection against factors like particle bombardment and thermal cycles affecting longevity.

Applications and Current Trends

Photovoltaic systems are widely used today for various applications including powering homes, emergency phones along highways, toys, calculators, and autonomous garden lights among others.

Silicon remains the predominant material found in photovoltaic cells today. Monocrystalline and polycrystalline silicons are commonly used; while polycrystalline is slightly less efficient than monocrystalline, it offers cost advantages.

Conclusion: Evolution of Silicon Technology