Extractive Metallurgy of Niobium

A.K. Suri, C. K. Gupta, A. K. Suri

• Publisher: Routledge
• Year: 2017
• Print ISBN: 9780849360718
• eBook ISBN: 9781351448963
• Topic: Physical Sciences
• Subtopic: Materials Science

The growth and development witnessed today in modern science, engineering, and technology owes a heavy debt to the rare, refractory, and reactive metals group, of which niobium is a member. Extractive Metallurgy of Niobium presents a vivid account of the metal through its comprehensive discussions of properties and applications, resources and resource processing, chemical processing and compound preparation, metal extraction, and refining and consolidation. Typical flow sheets adopted in some leading niobium-producing countries for the beneficiation of various niobium sources are presented, and various chemical processes for producing pure forms of niobium intermediates such as chloride, fluoride, and oxide are discussed. The book also explains how to liberate the metal from its intermediates and describes the physico-chemical principles involved. It is an excellent reference for chemical metallurgists, hydrometallurgists, extraction and process metallurgists, and minerals processors. It is also valuable to a wide variety of scientists, engineers, technologists, and students interested in the topic.

Chapter 1

Properties and Applications of Niobium

I. INTRODUCTION

The world of metals is diverse and absorbing. The properties of metals are extremely varied. A definition of metals is that they are solid bodies, malleable and lustrous. Indeed, iron, aluminum, copper, gold, silver, lead, tin, and other metals fully justify this definition. But there are no rules without exceptions, and one of the 80 or so metals in nature, i.e., mercury, is liquid under ordinary conditions. The example of mercury and its antipod, tungsten, illustrates the enormous range of properties characterizing metals. Mercury will not freeze even at below-zero freezing temperatures and solidifies only at −38.9°C. Tungsten, in comparison, will not be consumed by the hottest of flames and melts at almost 3400°C. Lithium being half as heavy as water, does not sink. Silver conducts electricity with characteristic ease and utmost rapidity, while titanium has the opposite property. The electrical conductivity of titanium is only a 300th part that of silver. However, for all their differences, metals have one thing in common — they all belong to one large family, although some of them may be regarded as no more than distant relations.

The credit for grouping the metals to form the large family one recognizes today goes to Dmitry Ivanovich Mendeleyev. It was only in 1869 that he devised the periodic table and all the elements discovered up to that time were assigned a place. They were grouped primarily on the basis of atomic weight, as well as similarities in physical and chemical properties. Elements with different characteristics and different behaviors were assigned positions as far away from one another as possible.

On discovery, niobium was assigned positon No. 41 (fifth period, fifth row). A partial view of the placement is shown in Figure 1.

A historical account of niobium is given below. The remainder of the chapter has been organized essentially into two parts. The first part is on the properties and the second on applications of this metal.

II. HISTORICAL^{1, 2, 3, 4}

Man’s acquaintance with many metals actually began in prehistoric times. One of the oldest and most celebrated metals is copper and this, along with gold, silver, iron, tin, lead, and mercury, makes up the magnificient seven of the metals, those that people have intimately known from the earliest times. The history of metals abounds in amazing incidents, at times romantic, humorous, mythological, tragic, or superstitious. Take, for instance, gold: never was a metal destined to play so sinister a role in the age-old history of humankind. For its sake wars were waged, nations and states were annihilated, and the most dreadful of crimes committed. No words can adequately describe the sorrow and suffering caused by this beautiful yellow metal. Gold is often described as the king of metals, highly valued, glorified, and worshipped. Yet, it enjoys practically no freedom. Rather, it is an eternal prisoner. The minute it is freed from the earth’s depths it is imprisoned again in unassailable safes, armor-plated vaults, and concrete-lined, underground, well-guarded storage. Such is the gloomy story of gold.

Returning to the metal with which we are concerned, like gold its history is a mixed picture, as will be described in the following sections.

A. Discovery

It will not be out of context if we strike the historical note with a story. It is about the Phrygian King Tantalus, the favorite son of Zeus. Wanting to impress the gods he had invited to a feast, he treated them to the flesh of his own son Pelops. Incensed by his cruelty and utterly senseless and deplorable act, the gods cursed Tantalus to perpetual thirst, hunger, and fear. Since then, Tantalus has been standing in the lower world, up to his chin in clear water, branches overgrown with ripe fruits bending low to him. When Tantalus opens his mouth to quench his thirst, the water flows away from his lips and when he raises his hand to get the fruit, the wind blows the branch high but the sinner is too weak to reach it. And above, an overhanging rock threatens to crush him at any minute. That is how the Greek myth tells about the torments of Tantalus. But more about its connection with our metal later.

In the middle of the 17th century, in the basin of the Columbia river, in North America, a heavy black mineral with golden veins of mica was found and, along with other specimens collected in different parts of the New World, was sent to the British Museum. The mineral was kept there in a glass case as a specimen of iron ore for nearly 150 years. In 1801 Charles Hatchett became interested in the beautiful mineral, analyzed it, and found that it contained iron as well as manganese and oxygen. It also contained an unknown element which, when tested, formed a substance with the properties of an oxide. Hatchett called it columbium. A year later in 1802 a Swedish scientist, Andres Ekeberg, found another new element in some Scandinivian minerals. The Swedish scientist remembered very well the Greek mythological story when time after time he repeated his futile attempt to dissolve the oxide of the new elements in acids. He called the element he discovered in 1802 tantalum, in honor of the mythological Tantalus. Apparently, this name was to symbolize the difficulties (torments of Tantalus) in the chemical dissolution of the oxide.

The names of many metals speak for themselves: hydrogen — producing water; carbon — producing coal; mendelevium, einsteinium, fermium, curium, and kurchatorium — all honor outstanding scientists; europium, americium, francium, germanium, and californium speak of the places where they were found. Adding to the last grouping is the name columbium, given after the country of its origin, Columbia (America was then called Columbia).

Hatchett’s columbium and Ekeberg’s tantalum were strikingly similar, and they were taken as chemical twins (Figure 2). In fact, many chemists were misled and, after long argument, arrived at the conclusion that the two were one and the same element, tantalum. Among the many chemists, mention may be made of the German chemist, Friedrich Wohler. He, too, failed to grasp the relationship between the two elements and the confusion lasted for more than 40 years. It was only in 1844 that the German chemist Heinrich Rose was successful in clarifying the situation. He proved that columbium was a different element from tantalum. Since the two elements were obviously related to each other in many respects, Rose g...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Chapter 1 Properties and Applications of Niobium
• Chapter 2 Sources and Their Treatment Procedures
• Chapter 3 Chemical Processing
• Chapter 4 Reduction Processes
• Chapter 5 Purification and Consolidation
• Chapter 6 Autobiography
• Index