LECTURE 10.1LECTURE 10.1

LECTURE OUTLINELECTURE OUTLINE

Weekly DeadlinesWeekly DeadlinesCRRA #5 Processing of SulfurCRRA #5 Processing of Sulfur

Concept MapConcept MapSelf-Review QuestionsSelf-Review Questions

Electronic Properties IElectronic Properties I

Lesson# 10 Name Properties, Part 2: Electronic Properties

Lectures Monday: Lecture 10.1 CRRA #5 Processing of Sulfur

Wednesday: Lecture 10.2 Electronic Properties

Required Book Reading 1 (For the End-of-Lesson Quiz)

Part E: The Materials Science Tetrahedron II: Properties Chapters 28, and 29

Required Book Reading 2 (For the Lesson 11 Pract ice Quiz)

Part F: The Materials Science Tetrahedron III: Processing Chapters 32 and 34

Animations Mike Fleck: “The Nature of Electricity,” “A Gedanken (Thought) Experiment,” and “Swan Lamp”

Ian Harrison: “Electronic Properties of Materials” Biographies Mineral of the Week

Camera-Ready Review Article (CRRA)

CRRA Report # 5: OPTIONAL SUBMISSSION, due Wednesday

Practice Quiz Practice quizzes (5 questions each) are available. There are also practice quizzes in Perception. Questions are similar to those in the main quiz database. A complete “prototype” end-of-lesson (practice) quiz is found in the Lesson 10 Lecture Notes folder.

End-of-Lesson Quiz Quiz 10 will consist of ~ 20 questions for a total of 50 points. Quizzes are “individualized” but questions are taken from a large database. The material covered will be the book reading and animations.

CRRA #5CRRA #5

Processing Concept MapProcessing Concept Map

CRRA #5CRRA #5

Processing: Self-Review QuestionsProcessing: Self-Review Questions

General CommentGeneral Comment

Overkill! The essay contains far more content than I would ever expect in a student essay. However, it is as complete an essay as I could write on the subject. Even so, it only scores ten out of twenty!

Are the geological/geochemical processes, through which the raw material(s) is/are created described?

Yes (1). It is a qualified yes. Beginning at the bottom of the first page, the formation of native sulfur, via volcanic activity is mentioned: “According to Davis and Detro (1992), early civilizations

obtained what little sulfur they required by either: (i) harvesting the native element formed from volcanic activity. This

native sulfur was formed through the reaction between the gasses SO2 and H2S as:

SO2 + 2H2S 2H2O + 3S.”

However, the formation of sulfur deposits as part of the cap-rock on oil deposits is not described. So I will give myself one point!

Are the biological/biogenic processes through which the raw material(s) is/are created described?

No (0). There is nothing on the biogenic formation of sulfur in this essay component, although it is mentioned in the structures component.

Are the geographical locations of the raw materials presented? Are political implications addressed?

Yes (1). The text does describe the sulfur deposits in Sicily, Texas, and Louisiana. See Section 5.3“Vast deposits of sulfur had been found in, e.g.,

Louisiana and Texas, but were buried below layers of, e.g., clay, rock and quicksand (Partington 1937).”

However, political implications are not addressed—hence, one point.

Are mining methods, including “beneficiation”/concentration described?

Yes (2). The Frasch process is presented in some detail, both in the text (Section 5.3) and in Figure 3.

Is the primary processing/extraction of the material from the raw material presented?

Yes (2). The extraction of the elemental sulfur from pyrite (FeS2) is described in the text and with respect to Figure 1a.

Figure 1. Scanned images of woodcuts from De Re Metallica (from Agricola, 1556). Figure 1a) depicts the formation of elemental sulfur from fool’s gold (FeS2) and/or chalcopyrite (CuFeS2). Relatively large lumps of the ore are loaded into an earthenware pot (see far left of figure), which contains several perforations in its base (see center foreground). The ore-containing pots are placed over circular holes in iron plates and heated with wood. The liquid sulfur drips through the perforations in the base of the pots and then into a second series of pots, the latter containing water.

Figure 1b) shows the distillation of elemental sulfur from a “sulfur/earth” mixture. The mixture of sulfur (perhaps 15-25%) and materials such as gypsum and limestone is put in a flat-bottomed pot, which sits atop a furnace. The pots are covered with lids, which are sealed with “lute” (which was probably a mixture of clay and powdered charcoal). A spout from the flat-bottomed pot feeds into a second pot (B). The impure sulfur boils in the first pot and is transported to the second pot via the spout where it condenses to a liquid, which is tapped into a wooden trough.

Are the methods for purifying originally impure materials (i.e. secondary processing) discussed?

Yes (2). The purification of sulfur, through the process of distillation, is discussed (also see Figures 1b and 2b).

Figure 2a) is a schematic diagram of an environmental disaster—a calcaroni, or sulfur kiln (from Partington, 1937). The kiln is loaded with lumps of the sulfur/rock mixture and covered with a layer of powdered sulfur. When the latter is ignited, a fraction of the sulfur is melted and collected in a reservoir at the bottom. The vertical channels are air vents.

Figure 2b) shows a sulfur refinery (from Partington, 1937). Sulfur is boiled in an iron retort and the sulfur vapors are condensed in a brickwork chamber. Note the similarity between this process and that described by Agricola in 1556 (Figure 1b).

Are tertiary processing methods introduced (e.g., casting, extrusion, rolling, and cutting)?

No (0).

Are the processing methods related to the physical properties of the material?

No (0). Although it is implicit in the description of the Frasch process that sulfur has a low melting point, it is not explicitly stated.

Are environmental issues related to primary, secondary, or tertiary processing addressed?

Yes (2). Section 5.4, “Non-Discretionary Sulfur,” relates to environmental concerns:“The increasing environmental concerns of the

latter half of the twentieth century saw a quickening in the amount of sulfur recovered from the waste gasses of various industrial processes and a concomitant decrease in the amount of discretionary sulfur needed.”

Is the final assembly, which might involve a joining process (gluing, welding, soldering) described?

No (0).SCORE: 10/20.

ELECTRONIC PROPERTIES IELECTRONIC PROPERTIES I

Metallic ConductionMetallic ConductionOhm’s LawOhm’s LawNumber of Free Electrons/AtomNumber of Free Electrons/AtomDrift VelocityDrift VelocityFree Electron/Electron Hole PairsFree Electron/Electron Hole PairsThe Group IV ElementsThe Group IV Elements

ELECTRICAL CONDUCTIVITY ELECTRICAL CONDUCTIVITY IN A METALIN A METAL

CONDUCTIVITY AND OHM’S CONDUCTIVITY AND OHM’S LAWLAW

The current that flows through a material is The current that flows through a material is proportional to the voltage (or electrical proportional to the voltage (or electrical pressure difference).pressure difference).

Or:Or:

I I V VOr:Or:

I = I = VVWhereWhere is called the conductivityis called the conductivity

CONDUCTIVITY AND OHM’S CONDUCTIVITY AND OHM’S LAWLAW

The current that flows alongthe wire is equal to the number of charge carriers (electrons) multiplied by their “drift velocity” multiplied by the charge on the electron.

Or:

I = qnv

CONDUCTIVITIES OF CONDUCTIVITIES OF MATERIALSMATERIALS

For metals:For metals:n/atom ~ 1n/atom ~ 1

For non-metals:For non-metals:n/atom ~ 0n/atom ~ 0

For semiconductors:For semiconductors:n is small, but finiten is small, but finite

For metals, the For metals, the conductivity (s) depends conductivity (s) depends on how the drift velocity on how the drift velocity varies with with varies with with something such as something such as temperature.temperature.

THE DRIFT VELOCITY AND THE THE DRIFT VELOCITY AND THE CONDUCTIVITY OF METALSCONDUCTIVITY OF METALS

In metals, the variation in In metals, the variation in conductivity is related to the conductivity is related to the variation in the drift variation in the drift velocity of the electrons.velocity of the electrons.

The drift velocity decreases The drift velocity decreases as the frequency of atomic as the frequency of atomic collisions increases.collisions increases.

The drift velocity decreases The drift velocity decreases as temperature increases.as temperature increases.

The drift velocity decreases The drift velocity decreases as the solute level increases.as the solute level increases.

EFFECT OF “PURITY” AND EFFECT OF “PURITY” AND TEMPERATURE ON METALLIC TEMPERATURE ON METALLIC

CONDUCTIVITIESCONDUCTIVITIES

HOW ARE FREE ELECTRONS CREATED HOW ARE FREE ELECTRONS CREATED IN A COVALENTLY BONDED IN A COVALENTLY BONDED

SEMICONDUCTOR?SEMICONDUCTOR?

Free electron/electron hole pairs may be Free electron/electron hole pairs may be created by:created by:light light √√√√heatheat √√ √√electric field electric field xxxx

CREATION OF A FREE CREATION OF A FREE ELECTRON/ELECTRON-HOLE ELECTRON/ELECTRON-HOLE

PAIRPAIR

IONIZATION ENERGIES OF IONIZATION ENERGIES OF THE GROUP IV ELEMENTS ITHE GROUP IV ELEMENTS I

For diamond-C, the outer-For diamond-C, the outer-shell electrons are in the shell electrons are in the L-shell. They are so L-shell. They are so closely bound that the closely bound that the ionization energy is ionization energy is prohibitively high. prohibitively high. Diamond-C is a Diamond-C is a prototypical electrical prototypical electrical insulator.insulator.

n/atom ~ 0n/atom ~ 0

IONIZATION ENERGIES OF IONIZATION ENERGIES OF THE GROUP IV ELEMENTS IITHE GROUP IV ELEMENTS II

For lead, the outer-shell For lead, the outer-shell electrons are in the P-shell. electrons are in the P-shell. They are so loosely bound They are so loosely bound that lead’s outer-shell that lead’s outer-shell electrons are free at room electrons are free at room temperatures. Lead is a temperatures. Lead is a prototypical electrical prototypical electrical conductor.conductor.

n/atom ~ 1n/atom ~ 1

IONIZATION ENERGIES OF IONIZATION ENERGIES OF THE GROUP IV ELEMENTS IIITHE GROUP IV ELEMENTS III

For silicon and For silicon and germanium, the germanium, the ionization energies are ionization energies are such that their electrical such that their electrical properties are midway properties are midway between those of a between those of a “typical” insulator and a “typical” insulator and a “typical” conductor. “typical” conductor. They are elemental They are elemental semiconductors!semiconductors!