Teeth Are Harder Than Steel

Hardness of various materials
Infographic created by Grok

Did you know that on a modified Mohs hardness scale that runs from 1 to 10, tooth enamel would rank at 5? That's harder than mild steel at 4.0 to 4.5 and softer than glass at 5.5.

From the Wikipedia Rabbit Hole Day Trip: Bacterial Cellulose

Lightenoughtotravel, Public domain, via Wikimedia Commons

The equivalent of cellulose in other plants (e.g. wood formed from lignin fibres in trees), but made by bacteria. So just like plant cells have a cellulose shell to give them protection and structural integrity, bacteria have something similar. I ended up on this page because I was reading on a homemade tools group about how someone had used the stuff in the same way leather is used, for strapping two parts together. Bacterial cellulose has certain desirable characteristics such as greater tensile strength than plant cellulose and large hydrophilicity (attraction to water) and so may be useful in biomedical applications.

More info in this Wikipedia article.

#MaterialsScience

Asbestos, the Wonder Material

From the Ladybird Book, Rocks and Minerals

From one of my Ladybird books (Rocks and Minerals). I have a slab of this that my father brought me home from the Curragh, used probably for boiler lining. I think I used to use it on a portable gas stove when heating stuff. There was also a layer of asbestos on the gauze mats we placed on tripods in chemistry class in school. That was to prevent the direct flame of a Bunsen burner cracking glass beakers and flasks.

Mars Curiosity Rover: Lessons Learned on Wheel Design

Public domain image courtesy NASA/JPL-Caltech/MSSS.

"The anomalous wheel wear suggests that loads and terrains representative of actual operational conditions were not adequately simulated during life testing"

 

The tyres are made from aluminium. According to this recommendation by JPL, metal fatigue and single event punctures caused by wind-eroded, immobile pyramidal shaped rocks was responsible for the damage.

The Curiosity rover has travelled over 20 miles on the surface of Mars since it landed on the red planet in 2011 as part of the Mars Science Laboratory mission. The robot is about the size of a small car and weighs around 900 kg.

Making Stiff Plastic, Elastic

Various plastic items. Created by Bing Image Creator.

Materials can be elastic, plastic or both. Plastic materials such as soft toffee, chewing gum or plasticine deform when stretched or compressed, but don't return to their original shape when the external force is removed. Elasticity is a property of a material that allows it to regain its original shape when subject to a force. So for instance rubber is elastic and similarly if you flex a steel ruler or stretch a spring, they regain their shape when the force is removed. When a force is applied to a material, it undergoes a strain, which in mechanics (a branch of physics that deals with energy and forces and their effect on bodies) is defined as the ratio of the extension of the material to its original length. The stress in the material is the tensile reaction due to the external force causing the stretching (effectively the material "pulls back" because of nuclear forces in the atoms). For many materials there's a proportional relationship between stress and strain up to a certain point. Eventually a point is reached however when a material no longer behaves elastically, called the elastic limit, beyond which it will deform plastically. If you've ever bent a piece of metal, you'll know that it'll spring back, but if you bend it too much, it'll stay bent. That's because the elastic limit was exceeded. Even glass is elastic and if you push on a glass window or shower door, you can see the glass flexing. However glass has very little plasticity and usually fractures suddenly when stresses are not much greater than the elastic limit.
This article on Phys.org discusses the issues with polymers and making them stiff and elastic. Currently they can be made elastic or stiff, but not both at the same time. Stiff technically means that there's very little strain for a given stress. So steel is stiff but rubber isn't. However a stiff and strong spring such as used in the suspension of a truck or train is still elastic, and can flex and return to its original shape if subject to large forces. That's not the case with plastic and if it's made stiff, it can't stretch elastically. So it behaves more like concrete when stretched, and fractures. A new technique for making polymers will hopefully improve the properties of polymers so they behave better when used for such things as prosthetics and medical implants.

Bike Ride to Investigate the Barrow Way and New Barrow Bridge

© Eugene Brennan

I did a 77 km cycle yesterday following a loop taking in the greenway from Athy to Vicarstown, having previously done the Monasterevin to Vicarstown section. I hadn't been on the new distributor road in Athy before, which has a nice cycle path that runs over the old railway bridge crossing the River Barrow (Bleach Bridge). This was one of the first concrete bridges in Ireland, the branch line crossing it coming off the GSWR mainline near Athy station. The branch served the two collieries south of Athy at Gracefield and Modubeagh and laterally the Tegral factory. The distributor road is carried over a new single-span steel composite bridge. According to Roughan & O’Donovan-AECOM who were appointed to provide technical consultancy services for the Athy Distributor Road project, the bridge consists of two, 80 m steel plate girders, made from weathering steel to reduce future maintenance costs. Weathering steel, also known by the trademark COR-TEN or corten steel is an alloy made by adding copper and other elements to resist corrosion. (Similar to the way stainless steel has chrome added). However weathering steel builds up a patina or weathered coating that resists further corrosion, unlike "normal" steel. Corten steel is used for the Fionn MacCumhaill and his hounds sculpture at junction 12 on the M7 at Ballymany.

© Eugene Brennan

The Most Dense Metals

Image generated by AI using Bing Image Creator

Did you know that the liquid metal mercury has a density of 13.55 grams per cubic centimetre (g/cm³), more dense than lead which has a density of 11.34 g/cm³ ? Gold is even more dense at 19.28 g/cm³. The most dense metal however is osmium, with a density of 22.59 g/cm³ and is the densest naturally occurring element. Most elements don't occur naturally, and have to be refined and extracted from ore which is often a compound of the element of interest and other elements such as oxygen and sulphur. Osmium is too brittle to be used on its own, and alloyed with other metals for applications that require durability such as instrument pivots and electrical contacts. It's also used as an abrasive for polishing optical lenses.

There used to be a bottle of mercury (which was quite weighty) in the BNS in Kilcullen when it was situated in the current library building. Hopefully the mercury was disposed of safely or is now stored properly. There was also a collection of scientific apparatus, glassware, and a balance from a time when science was taught in primary schools. (Before revised curriculums in more recent decades when it was reintroduced, although we did have "Nature Studies" in the 70s). I wonder what happened all that equipment? According to this Irish Times article, science was dropped as a compulsory subject following independence in 1922 (I've run out of my free article quota for this month, so I can't read the full article yet)

Rust, "the pervasive menace" From the Big Picture Science Podcasts

© Eugene Brennan

"Should the Iron Age really be called the “Rust Age”? When using iron, the benefits seem to outweigh the risks—especially if we embrace good maintenance, but the defense department considers rust a huge threat." This podcast from the Big Picture Science team delves into the problem of corrosion.