81 votes

Why can a diamond be broken using a hammer if it's the hardest natural substance known?

Hardness and toughness are not the same Hardness and toughness are very different qualities in materials and are weakly related. Hardness is strongly related to the more well-defined quantity of ...
matt_black's user avatar
  • 36.1k
46 votes

Why isn't 'chemically-strengthened glass' made with potassium carbonate to begin with?

The potassium is not added first because the potassium does not intrinsically make stronger glass, it is the substitution of a larger ion for a smaller one at the surface that does. To understand why ...
A.K.'s user avatar
  • 12.5k
35 votes
Accepted

Which is the densest gas known?

Perfluorobutane is inert and has almost twice the density of sulfur hexafluoride. It is non-toxic enough that it is used in fire extinguishers and injected as a contrast agent for ultrasound. Boiling ...
Jonathan Ray's user avatar
30 votes

What easily accessible material has melting point between 500 °C and 590 °C?

Temperature-indicating or thermo crayons are used by welders. These melt at specific temperatures. Not as an endorsement, but to give you an idea of what's available, the crayons from McMaster-Carr ...
Wayne Conrad's user avatar
26 votes

Why isn't 'chemically-strengthened glass' made with potassium carbonate to begin with?

Chemically-strengthened glass is similar tempered glass in that the outside of the glass is under compression, while the inside is not compressed. If all the sodium in chemically-strengthened glass ...
DrMoishe Pippik's user avatar
24 votes

If you put two blocks of an element together, why don't they bond?

Why, when you bring the two bars together so that they touch each other, do they not instantly bond with each other forming one larger bar or block? ... Why do we need to 'weld' two bars together - ...
hBy2Py's user avatar
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21 votes
Accepted

What makes Gorilla Glass more durable with each generation?

Are there other ways of "chemical strengthening" besides cationic exchange that can be utilized to strengthen the glass, keeping it flexible and less fragile at the same time? In a word: No. To ...
A.K.'s user avatar
  • 12.5k
20 votes

What is the @ symbol used for in material science?

The at symbol @ universally means "at the site" or "at the rate of". It is routinely used in supramolecular chemistry to denote guest@host relationship because it follows the ...
andselisk's user avatar
  • 37.6k
20 votes
Accepted

Why use diamond-like carbon instead of diamond?

You balance cost of manufacture and return of investment for the anticipated use. If you read about the methods of production of diamond-like carbon (DLC), e.g., on Wikipedia, e.g. «DLC is typically ...
Buttonwood's user avatar
  • 29.7k
18 votes

What easily accessible material has melting point between 500 °C and 590 °C?

It might not qualify as 'available at home' but MakeItFrom has a database with engineering material you can search: MakeItFrom.com is a curated database of engineering material properties that ...
Glorfindel's user avatar
  • 2,075
15 votes
Accepted

What does "René" mean in René alloys?

Similar to inox for inoxydable (inoxidable), it equally is a French coinage. To tune mechanical properties of iron, mixing additives leads to numerous alloys of iron. In case of rene or rené as ...
Buttonwood's user avatar
  • 29.7k
15 votes

Conception and manufacture of the Avogadro Project's (nearly) perfect silicon sphere (and, what is “atomic feeling”?)

Short answer: The success of the project benefitted from many contributors. According to BIPM and its Avogadro project, there are two spheres (reference). The page equally refers to a publiction ...
Buttonwood's user avatar
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14 votes

Why can a diamond be broken using a hammer if it's the hardest natural substance known?

Diamond has cleavage planes. If you want something nearly unbreakable, try nephrite, which is a tough form of jade used by the ancient Aztecs to make axe heads! Actinolite is another related "tough as ...
rock hound's user avatar
14 votes
Accepted

Can a vacuum on a closed system really “pull” things out of it?

Gasses don't get "pulled", they get "pushed". When you empty a neon tube, you attach a device with almost no air in it to mouth of the tube. The air that is in the tube then pushes ...
Ray Butterworth's user avatar
13 votes

Is there a material that ions can pass through but water can’t?

There are so many materials that allow the passage of ions but not water. They are called ion-exchange membranes. I believe you are interested in water purification based on your previous posts. The ...
AChem's user avatar
  • 40.1k
12 votes

Rubber composition A13 B13 C20 F17 K11 L14

TL;DR I think you might need two more things to interpret this line: the first code part of the standard, and the standard itself - ASTM D2000 (needs to be purchased). These descriptors are not ...
andselisk's user avatar
  • 37.6k
11 votes

What easily accessible material has melting point between 500 °C and 590 °C?

Name Formula m.p./°C Copper(II) chloride $\ce{CuCl2}$ 498 Barium perchlorate $\ce{Ba(ClO4)2}$ 505 Potassium fluoroborate* $\ce{KBF4}$ 530 Antimony trisulfide (stibnite) $\ce{Sb2S3}$ 550 Calcium ...
Maurice's user avatar
  • 28.3k
11 votes

Why I am unable to see any electrical conductivity in Permalloy nano powders?

Nanoparticles are often pyrophoric, and may be coated to prevent spontaneous combustion. The particles' surface might be nitrided, or oxide coated, or coated with an organic chemical. Permalloy itself ...
DrMoishe Pippik's user avatar
10 votes
Accepted

Conception and manufacture of the Avogadro Project's (nearly) perfect silicon sphere (and, what is “atomic feeling”?)

First thing I think we have to differentiate between checking the roundness and the roughness (that in the article seems it is called smoothness) these two properties of the surface necessitate ...
G M's user avatar
  • 9,069
10 votes
Accepted

What is the optimal voltage for storing a 3.7 V lithium polymer battery?

The $\pu{3.6-3.8 V}$ range is a good general choice, but it may be battery-specific. The particular voltage for 40% charge may differ for different cell technologies, e.g. various deviations of ...
Poutnik's user avatar
  • 41.5k
10 votes

Why use diamond-like carbon instead of diamond?

Why do you think that would be preferable? A perfect crystal is rather fragile - diamonds are hard, but they also have perfect cleavage - one good hit and you have two diamonds (or a bunch of shards). ...
Luaan's user avatar
  • 505
10 votes
Accepted

What material properties are unpredictable (not reproducible) but can be measured consistently and at a low cost?

Impossible for a homogeneous material, however ... basically every nonhomogeneous material fits your description. Say the pattern of microphase separation in a copolymer. Or the arrangement of filler ...
Karl's user avatar
  • 12.1k
9 votes
Accepted

(At what temperature) can salt evaporate?

All substances may have a melting and boiling point. I say "may" because in some instances there can be decomposition, for example, before reaching either temperature. Sodium chloride has a melting ...
Pedro O'Verde's user avatar
9 votes
Accepted

Technical name for the holes (missing electrons) in a p-type semi-conductor?

Yes, the technical name is, in fact, an electron hole (typically referred to as simply a hole). It is considered suitable to describe these holes as electric charge carriers with a positive charge ...
Argon's user avatar
  • 1,342
9 votes

What easily accessible material has melting point between 500 °C and 590 °C?

There ought to be an alloy with the desired melting point. It doesn't seem to be commercially available, but you could experiment by obtaining tin or zinc, plus copper powder (or scrap brass / bronze),...
nigel222's user avatar
  • 191
8 votes

Does crystalline glass exist?

As Ivan explained, a glass is by definition amorphous. However, you can take a quartz crystal (silicon dioxide, which is the main ingredient of glass) if it is of high purity and optical quality, and ...
iad22agp's user avatar
  • 9,237
8 votes
Accepted

What are some materials that expand a lot proportionally to heat?

You are looking for thermal expansion and its coefficient. Of course such tables, and diagrams exist (source) as it is of relevance in daily live. Thermometers based on liquid mercury, or alcohol, ...
Buttonwood's user avatar
  • 29.7k
8 votes

What gas has the highest refractive index?

The question has to be more specific to get a specific answer. Even in the table linked in the OP, bromine gas (1.001132) has a higher index of refraction than 1.000773. At zero degrees C, 5462 ...
DavePhD's user avatar
  • 40.6k
8 votes
Accepted

When styrofoam shrinks from pressure, why doesn't it go back to normal after decreasing the pressure?

The structure of styrofoam isn't as perfectly elastic as you think Most styrofoam is created by various mechanisms that blow gases into the polystyrene matrix as it cools. One common process involves ...
matt_black's user avatar
  • 36.1k
7 votes

Why are so many ionic compounds brittle?

They’re brittle because it’s very difficult for dislocations to move through the crystal lattice. Dislocations are what mediate plastic deformation in crystals, so the fact that creating and moving a ...
Chris's user avatar
  • 186

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