Metals: Atomic Structure and Properties PDF

METALS Atomic Structure of Metals Metallic Atoms - are metals composed of atoms that have relatively few electrons in their outermost energy levels (typically 1-3 valence electrons). These electrons are weakly bound to the nucleus. According to LibreTexts Chemistry (2016), the atoms in metals are...

METALS Atomic Structure of Metals Metallic Atoms - are metals composed of atoms that have relatively few electrons in their outermost energy levels (typically 1-3 valence electrons). These electrons are weakly bound to the nucleus. According to LibreTexts Chemistry (2016), the atoms in metals are arranged in a highly ordered and repeating 3D structure called a metallic crystal lattice. These lattices can have different types of geometries such as: Body-Centered Cubic (BCC) - Atoms are positioned at the corners of a cube with one atom in the center. Examples include iron and chromium. Face-Centered Cubic (FCC) - Atoms are located at the corners and at the centers of each cube face. Examples include aluminum and copper. Hexagonal Close-Packed (HCP) - Atoms form a hexagonal pattern, which is typical in metals like magnesium and zinc. Metallic Bonding of Metals Metallic bonding is the type of bonding you get between metal atoms. Recap: Metallic bonding - bonding of metals to metals Ionic bonding - bonding of metals to nonmetals Covalent bonding - bonding of nonmetals to nonmetals Solid metals consist of giant atoms arranged in a regular pattern while each atoms are surrounded by the electrons in its outermost shell and shares them with all the other metals in the atom which means that all the atoms will become positive ions because they lost negative electrons. Additionally, since all the electrons are free to move about, it is now called delocalized electrons which results in a stronger electrostatic attraction between the positive ions and the negative electrons, and these forces of attraction hold everything together in a regular structure which gives the overall metal strength They are also good conductors of electricity and heat because the delocalized electrons can carry electrical current and thermal energy throughout the structure. Moreover, metals are malleable which means they can be easily bent or hammered into shapes because metals have such a regular structure that allows the different layers to slide over one another. At least for pure metals, if we want harder metals that can't bend easily, we can make alloys. Alloys are made up of two or more different elements by mixing two different metals—or sometimes a metal and a nonmetal that have different sized atoms because it disrupts the regular shape atoms that stop the layers from sliding from one another, which makes the alloy much harder than pure metals. Mechanical Properties of Metals A mechanical property deals with the behavior of materials or metals when they are subjected to external forces or loads. These mechanical properties are considered while designing machine components as it will ensure that the machine will function at its best. Understanding these properties is crucial for selecting the right metal for different engineering and construction applications. Mechanical Properties of Metals: Strength: - Resistance to an external force or it is the capacity or ability to withstand various loads without deformation, bending, or breaking. - 3 types of strengths: 1. Tensile strength 2. Compressive strength 3. Shear strength Ductility: - The ability of a material to undergo significant plastic deformation (stretching or bending) without breaking. - As the temperature increases, metals generally become more ductile. Conversely, as the temperature decreases, metals tend to become less ductile and more brittle. Hardness: - It is the ability of a material to resist scratching, abrasion, indentation, or penetration. - The Brinell hardness test measures hardness by pressing a hardened ball into a material's surface. The Brinell hardness number (BHN) is calculated by dividing the applied load (in kilograms) by the area of the impression (in square millimeters). Some other mechanical properties of metals: Toughness - material's ability to absorb energy and deform without breaking. Elasticity - The property of metal and its ability to return to its shape and size after removal of load or to regain its initial position or shape and size when the applied load is removed. Plasticity - the ability of a material to undergo permanent deformation without breaking. Brittleness - Brittleness is the property of a material that causes it to fracture easily with little to no deformation. Brittle materials break under small loads and are the opposite of tough and ductile materials. Process of Alloying To begin, alloys are made up of two or more different elements by mixing two different metals—or sometimes a metal and a nonmetal that have different sized atoms Alloys can be classified as: Substitutional Alloys - When atoms of the added element replace some of the metal atoms in the crystal structure. Interstitial Alloys - When smaller atoms fit into the gaps between the larger metal atoms. How do we create an alloy? Alloying is the process of combining a metal with one or more other elements (metals or non-metals) to improve or change its properties. We alloy metal because pure metals often have limitations, such as being too soft, too reactive, or prone to corrosion. Alloying helps to overcome these drawbacks and fine-tune the properties for specific applications. So how do we alloy metals? There are a lot of types of alloying, but the most common ones are: Melting and Mixing - where metals are usually alloyed by melting them down, then the alloying elements are added, then mixing the molten metals. Once cooled, the mixture solidifies into an alloy with a different structure and properties than the pure metal. Powder Metallurgy - is a process for making alloys by mixing metal powders and then compacting and sintering them into solid parts. Pure metal powders are mixed together, or with non-metallic powders. Then, the powder is pressed into a die to form the desired shape. Lastly, the powder is heated below its melting point to cause the particles to bond together. Effects of Alloying on the Properties of Metals Increase strength - Alloying can increase the strength of a metal. The addition of carbon, which is the main alloying element of steel, increases the tensile strength of a metal. Increase corrosion resistance - Alloys can have much better high-temperature oxidation resistance than pure metals. Chromium is an element that can increase a metal’s resistance to corrosion and rust. Improved Hardness - Alloying elements like chromium and vanadium can make metals harder and more resistant to wear. Improved Toughness - Alloys like those with nickel become tougher, meaning they can absorb more energy before breaking. Examples of Alloys and its Uses in Daily Life Alloy Composition Uses Duralumin Aluminum and copper Aircraft parts Magnalium Aluminum and magnesium Aircraft parts Propellers for ships, bells, Bronze Copper and tin automobile parts Coins, musical instruments, Brass Copper and zinc utensils Jewelry gold Gold and copper Jewelry Joining copper pipes and Solder Tin and copper electrical components/wires POLYMERS 3.2.1 Explain the structure and properties of polymers, including thermoplastics,thermosets, and elastomers; The Structure of Polymers - Polymers consist of long chains of repeating units called monomers, which form complex structures. The backbone of these chains is carbon, which bonds covalently with other atoms like hydrogen, sharing electrons to complete their atomic structures. Carbon typically bonds with four hydrogen atoms, creating stable molecules. The process of combining these monomers is called polymerization. They are held together by primary bonds (covalent bonds) and secondary bonds (van der Waals and hydrogen bonds). The Four Basic Polymer Structure Linear Polymers - Linear polymers, which look like long strands of spaghetti, are held together by weak van der Waals or hydrogen bonds. These bonds are easy to break with heat, making linear polymers thermoplastic. This means they can be melted and remolded when heated. Branched Polymers - Branched polymers have shorter chains attached to their main backbone, making them less dense due to inefficient packing. These shorter chains prevent strong connections between longer backbones, allowing branched polymers to typically behave as thermoplastics that soften with heat. However, some complex branched polymers resist melting and instead break apart, acting as thermosetting materials. Crosslinked Polymers - Cross Linked polymers are like ladders, where chains connect from one backbone to another via covalent bonds, unlike the weaker van der Waals forces in linear polymers. This strong bonding typically makes crosslinked polymers thermosetting, though some may break their cross links at lower temperatures and act differently. Networked Polymers - Networked polymers are intricate structures with extensive three-dimensional linkages. Due to their heavy interconnections, they remain rigid and can't be softened with heat without damaging their structure, making them thermosetting.  Properties of Polymers - Thermoplastics are polymers that become pliable when heated and solidify upon cooling, allowing for repeated reshaping without significant degradation. They are versatile in manufacturing processes like injection molding and 3D printing, and typically possess good impact resistance and mechanical strength. Examples: include polyethylene (PE), polypropylene (PP), and PVC, and they are commonly used in packaging, consumer goods, automotive parts, and medical devices. - Elastomers are polymers with elastic properties, allowing them to return to their original shape after being deformed. They can stretch significantly and retract due to their cross-linked polymer chains, offering excellent elasticity, resilience, and fatigue resistance.  - Examples: include natural rubber, silicone rubber, and polyurethane elastomers, used in seals, gaskets, tires, footwear, and vibration dampening components. - Thermosets are polymers that chemically react during processing to form a permanently set shape, known as curing. Once cured, they cannot be remolded by heating due to this irreversible hardening. They possess excellent dimensional stability, high temperature, and chemical resistance, making them ideal for use in electronics, aerospace, automotive parts, and household appliances. Examples: including silicone, melamine, polyester, epoxy resins and phenolic resins. 3.2.2 Explain how polymers are made and describe the processes involved (addition and condensation polymerization); How Polymers are Made? Polymers are natural substances made up of macromolecules, which consist of numerous simple chemical units called monomers. They form the basis of much organic matter, including proteins, nucleic acids, and cellulose in plants, as well as minerals like quartz and diamond. Synthetic polymers are created through chemical reactions known as polymerizations, which mainly fall into two categories: addition and condensation. The Difference Between Addition and Condensation Polymerization? - Addition Polymerization: This process involves the linking of monomers with double or triple bonds, without the loss of any small molecules. The reaction typically requires an initiator to start the chain reaction, where the monomers continuously add to the growing polymer chain. This method is common for creating polymers like polyethylene, polypropylene, and polystyrene. - Condensation Polymerization: In contrast, this type of polymerization involves the reaction of monomers with functional groups, resulting in the formation of a polymer and the release of a small molecule, usually water or methanol. This reaction often involves step-growth mechanisms and is used to produce polymers such as nylon, polyester, and polyurethane. 3.2.3 Describe the mechanical and thermal properties of polymers and how they can be modified; Mechanical Properties of Polymers Strength: Compression Yield Strength: It is the ability of the material to withstand pressure without permanent deformation. Tensile Strength: Gauges the maximum stress a material can endure while being stretched or pulled before breaking. Impact Strength: Indicates how well a material can absorb energy from impacts without fracturing. Hardness: It refers to its resistance to surface indentation and scratching. Hard polymers are resistant to hard substances penetrating them. They are employed in the construction of electronics and can tolerate wear and tear as well as scratches. The Shore hardness test measures how hard or soft a plastic or rubber is, using a tool called a Durometer that presses into the material. The results, known as Durometer hardness, are given on either the Shore A scale for softer materials or the Shore D scale for harder ones. The hardness number might include an indentation time since the depth can change over time due to the material's rubbery nature. Elasticity: Elasticity in a polymer is its ability to return to its original shape after being stretched, compressed, or deformed. This is because of the polymer chains' flexibility, which allows them to stretch and then recoil back. Thermal Properties of Polymers Melting Temperature (Tm): The temperature at which the polymer changes from a solid to a liquid state. Glass Transition Temperature (Tg): The temperature at which the polymer shifts from being rigid to more rubbery and flexible. Thermal Expansion: This property determines how much a polymer expands or shrinks when exposed to heat or cold. Thermal Conductivity: Indicates how well a polymer can transfer heat through its structure. Thermal Stability: The resistance of a polymer to thermal degradation and its ability to maintain properties at elevated temperatures. Heat Capacity: The amount of heat required to raise the temperature of the polymer by a given amount. ENGINEERED NANOMATERIALS Definition: Nanomaterials are natural or manufactured materials, either built as a structure or loosely formed together, with an external size of 1 to 100 nanometers. Engineered nanomaterials specifically refer to these tiny materials when they are intentionally designed and manufactured for their unique physical and chemical properties, which makes them distinct from natural nanomaterials. They have significant applications in fields like medicine, electronics, and environmental science due to their unique interactions at the nanoscale. Examples: Nanomaterials can be found naturally in volcanic ash and by-products of combustion. Examples of manufactured or engineered nanomaterials are carbon nanotubes, metal/metal oxide nanoparticles, polymeric nanoparticles, and many more. 3.3.1. Unique properties of nanomaterials: One of the unique properties of nanomaterials is their large surface area compared to bulk material. The reason is nanomaterials, although small, have many more sides exposed on their surfaces. In contrast, bulk material only has its outside layer exposed, lowering the ratio between the material present and the material exposed. Another property of nanomaterials is their increased conductivity, due to their ability to increase the surface area of a material, they maximize conductivity by decreasing the amount of material electricity has to pass through, making conductivity more efficient. Lastly, nanomaterials increase the strength of a material with their unique properties. For example, concrete with nano-particles in its composition is tested to be stronger than regular concrete (https://www.sciencedirect.com/science/article/pii/S2214509523003777). This works under the principle of the unique properties of the nanomaterials and what they add to existing materials, such as strengthening bonds between materials, increasing flexibility, and even improving on aspects such as thermal conductivity and structural rigidity. Unique Properties of Nanomaterials: - Increased Surface Area - With more surface area relative to their volume, nanomaterials have higher reactivity, making them perfect for catalysis or medical applications. - Quantum Effects - At the nanoscale, materials can exhibit quantum effects, leading to unique optical, electrical, and magnetic properties. This is why gold nanoparticles, for instance, look red or purple rather than yellow. - Mechanical Properties - Nanomaterials often possess remarkable strength and flexibility. Carbon nanotubes, for instance, are incredibly strong and lightweight, making them suitable for everything from sports equipment to aerospace engineering. - Electrical Conductivity - Some nanomaterials have superior electrical properties, useful in electronics and nanodevices, Graphene, for example, conducts electricity better than copper. - Thermal Conductivity - Nanomaterials can have high thermal conductivity, making them effective in heat dissipation applications, like in computer chips. 3.3.2. Synthesis of nanomaterials: In the synthesis of nanomaterials, two methods are used; The Top-down approach and the Bottom-up approach. The Top-down approach works when a bulk material is repeatedly broken down until it becomes a nanomaterial. Nanomaterial manufactured using this technique requires the use of fine micromachining. Methods of achieving this are peeling, etching, high-energy milling, and lithography. (I would go more into detail, but fuck you all welcome to college enjoy the self-study :D ) Top - Down Methods - Milling and Grinding - Physically reducing the size of materials using mechanical force. - Laser Ablation - Using high-powered lasers to vaporize materials into nanoparticles. - Electrochemical Methods - Applying electrical currents to erode materials into nanoparticles. The Bottom-up approach works the opposite way as opposed to the Top-down approach. Instead of breaking down material, the material is built atom by atom using a Scanning Tunneling microscope, which allows the nanomaterial to be observed and manipulated, and constructed atom by atom. (I could explain how they work too, but fuck you welcome to college enjoy the self-study :D ) Bottom - Up Methods - Chemical Vapor Deposition (CVD) - Reacting gasses to form solid materials on a substrate. - Sol - Gel Process - Transitioning a solution into a solid gel to form nanoparticles. - Hydrothermal / Solvothermal Synthesis - Using high-pressure and temperature conditions in a liquid medium to grow crystals. (A BOY AND HIS ATOM) 3.3.3. Applications of Nanomaterials in fields of science. Nanomaterials are a great innovation in science, technology, and engineering, and are widely used in fields such as medicine, electronics, and energy. In the medical field, innovations such as nano tablets that send information to doctors about specific conditions of a patient, nano-bots that target certain cancer cells without damaging other cells, carbon nanotubes that help in the delivery of genes to cells and organs, and sensitive drug delivery, nanotechnology have helped in greatly advancing the medical field (https://www.sciencedirect.com/science/article/pii/S2414644723000337). In electronics, nanotechnology has greatly improved electrical efficiency in devices that we rely on such as mobile phones, satellite components, and fine microchips found even in smart fridges. Although nanotechnology is a great innovation in electronics, it comes with its challenges and difficulties. From the difficulty of manufacturing to complications such as the quantum effect the nanotechnology has on its surroundings affecting the properties of the device, the smaller and more efficient the technology gets, the more challenging it becomes to work with (https://www.knowledgenile.com/blogs/how-can-nanotechnology-be-useful-in-electronic-devices ). In energy, nanomaterials are a crucial technological innovation as newer technologies require more efficient batteries, with the ability to improve heat transfer and increase the overall efficiency of energy transfer from source to component, or even making an energy-stringent task like water treating a more efficient process, nanomaterials have improved the energy sector greatly (https://bnrc.springeropen.com/articles/10.1186/s42269-023-00984-4). On the harmful effects of nanoparticles on the health of the environment and its occupants, according to BMC Public Health, “The small sizes of nanoparticles give them the ability to permeate physiological barriers of living organisms, causing harmful biological reactions. Nanoparticles are known to enter the human body through the lung, intestinal tract, or skin, and can be toxic to the brain, cause lung inflammation and cardiac problems. In fact, certain nanoparticles have been found to cause permanent cell damage through organ injury and oxidative stress, due to their size and composition. In a study by Magrez et al. to assess the toxic effect of carbon-based nanoparticles on lung cancer cells, the authors reported findings suggesting that carbon-based nanoparticles cause size-dependent cytotoxicity. The level of toxicity of nanoparticles is suggested to be dependent on factors such as composition of the nanoparticle, size, surface functionality, crystallinity, and aggregation. Moreover, the toxicity of a nanoparticle in an individual is dependent on the genetic make-up of that individual, which is determined by the individual's ability to adapt and respond to toxic substances.” (https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-023-15958-4). Conclusion: Nanomaterials are materials measured on the nanoscale, that if added to materials can greatly improve and change their characteristics. Although nanotech has greatly innovated in fields such as medicine, electronics, and energy, it can also negatively affect the environment and human health.