In this blog post, we explore what inorganic engineering is as a field of study and examine its relevance to advanced industrial materials, focusing on inorganic compounds and metal oxides.
A few years ago, I came across a post on an internet site by a student hoping to enter the Department of Inorganic Engineering. I naturally assumed it was about inorganic materials engineering and eagerly clicked in, only to find the post filled with talk of missiles and bombs, leaving me feeling a bit deflated. I suspect many of you, like that student, probably thought of “weapons” when you first heard the name “Department of Inorganic Materials Engineering.” Even if not to that extent, I imagine many wondered, “What exactly is inorganic engineering?” So, I’d like to take this opportunity to provide a general introduction to inorganic engineering.
The ‘inorganic’ in inorganic engineering is a concept contrasting with the familiar ‘organic’. Organic substances are those that compose living organisms or are produced by them, and they all contain carbon. Therefore, inorganic substances, the opposite of organic, refer to materials that do not contain carbon. For example, proteins and fats that make up our bodies are organic substances, whereas metals like iron or aluminum, and substances like water, salt, and iodine are inorganic. Silica-based soil is a prime example of an inorganic material. Historically, instead of the term ‘inorganic engineering,’ the expression ‘ceramic engineering’ was used, signifying the process of firing clay to create pottery. Today, inorganic engineering is also referred to as ‘ceramic engineering,’ with ‘ceramic’ itself originating from pottery.
However, inorganic engineering does not cover all inorganic substances. Studying ceramics or salt holds little significance in modern times, and metals are so diverse in type and research field that a separate discipline called ‘metallurgical engineering’ exists. So, what specific materials does inorganic engineering study? To understand this, we first need to briefly examine the types of elements existing on Earth.
To date, 118 elements have been discovered, but excluding those synthesized artificially, only 92 exist stably in nature. These elements are broadly divided into metallic elements and non-metallic elements, with metallic elements numbering about 70, far exceeding non-metallic elements. Representative metallic elements include iron, copper, gold, silver, and aluminum, while non-metallic elements include carbon, oxygen, sulfur, and hydrogen. Each element exists as an atom, an extremely small particle. Atoms of various elements combine to form different substances. For example, lead atoms gather to form a lump of lead, while non-metallic carbon atoms combine to form diamond. Salt is a substance formed by the bonding of sodium atoms, a metal, and chlorine atoms, a nonmetal. Even just looking at lead, diamond, and salt, we can see that entirely different substances with distinct properties are created depending on which atoms bond together.
Returning to inorganic engineering, the subject of inorganic engineering research is generally substances formed by the bonding of metal atoms and nonmetal atoms. Salt, mentioned above, is an example of this. Particularly studied in inorganic engineering are materials formed by the bonding of metal atoms and oxygen atoms. These are numerous in type and quantity, possess excellent properties, and thus become major research subjects. They are called ‘metal oxides’ because they are formed through the oxidation process where metals bond with oxygen. Now, let’s examine the importance of metal oxides in current and future industries.
A representative field where metal oxides are currently used is catalysts. A catalyst is a substance that increases the rate of a chemical reaction, helping reactants interact more readily. Catalysts play a crucial role in industry: first, they shorten reaction times, enabling greater output within the same timeframe; second, they allow reactions to occur at relatively lower temperatures and pressures, reducing production costs. Since first gaining attention in the 1830s, catalysts have become essential elements across all industrial sectors.
So how do metal oxides accelerate chemical reactions? Consider a substance reacting with oxygen. Without a metal oxide, the reactant would interact with oxygen in the air. However, atmospheric oxygen exists as stable molecules and does not readily participate in reactions. Adding a metal oxide catalyst, however, provides oxygen atoms, enabling the reaction to proceed rapidly. Compared to atmospheric oxygen, the oxygen atoms provided by the metal oxide are highly unstable and seek to bond quickly with the reactants, thus accelerating the reaction rate.
The above explanation is merely a simplified example for illustrative purposes. The actual mechanisms by which metal oxide catalysts function are far more complex and diverse. Consequently, research on catalysts remains an active field of study.
Metal oxides are also gaining prominence as promising new materials for the future. For example, copper oxide mixed with calcium and barium forms a superconductor. Superconductors are materials that lose electrical resistance below a specific temperature, holding great potential for applications like energy storage devices or magnetic levitation trains. However, most superconductors only exhibit superconductivity below -200°C, making practical application difficult. However, copper oxide superconductors exhibit superconductivity even between -120°C and -150°C, allowing for limited practical use. Continued research raises hopes that a room-temperature superconducting material may one day be discovered or synthesized.
Additionally, recent research is actively exploring the development of novel memory devices using specific metal oxides like titanium oxide. Within metal oxides, oxygen atoms carry a negative charge. When a positive voltage is applied, these oxygen atoms move toward the electrode. When the voltage is removed, the oxygen atoms remain in place. This allows the metal oxide to ‘remember’ the duration for which the voltage was applied. Based on this principle, a device called a ‘memristor’ was developed. Using memristors could enable computers that don’t require booting, and potentially even computers equipped with artificial intelligence.
Beyond this, metal oxides also possess the property that their shape changes when electricity flows through them, and that shape change generates electricity. This makes them useful as piezoelectric materials for exploration and communication equipment, and their ability to withstand high temperatures makes them valuable as heat-resistant materials for use in furnaces.
This concludes our brief introduction to inorganic engineering. To summarize, inorganic engineering primarily studies materials composed of metallic and non-metallic elements, particularly metal oxides formed from metallic elements and oxygen. Currently, metal oxides are widely used as industrial materials like catalysts and are gaining attention as advanced materials such as superconductors and memristor devices. Of course, this does not encompass everything in inorganic engineering. Inorganic engineering involves a wide range of inorganic materials playing crucial roles, and the research topics are truly boundless. While the explanation focused on metal oxides due to space constraints, I want to emphasize that various other inorganic materials, such as nitrides, sulfides, and silicates, are also actively studied.
You might be a bit disappointed that this isn’t the ‘weapons engineering’ you imagined. Nevertheless, I hope this opportunity helped you understand what inorganic engineering is, and that you’ll leave thinking, “This inorganic engineering is actually quite interesting.” Thank you.
