manwithoutborders:

clearscience:

A battery scientist’s trivial dilemma
You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)
Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:
3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO
The 303/357 is a silver oxide battery having the overall reaction:
Zn + Ag2O = 2 Ag + ZnO
They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

Being a chemist, I’m more loyal to representing mixed oxides in the longhand format, MnO+Mn2O3. I don’t think the reaction in a battery is vigorous enough to produce “actual” Mn3O4. Is it common for battery scientist to use Mn3O4 over Mn2O3 as the product, I’m going to have to tear open a dead battery and check this on XRD. 

It’s a good point. However, if the battery is discharged at a sufficiently slow rate (20 hours or slower) you do observe the well-formed spinel structure of Mn3O4. Opening the battery and using a standard XRD will result in a collection of products that are difficult to distinguish. By using a synchrotron beam to do diffraction through the battery without opening it, a good Mn3O4 structure is observed. The Clear Science staff will have a paper out about this soon … our preliminary paper on the technique is here.
We aren’t the first people to identify Mn3O4 as the slow-rate product. The Handbook of Batteries gives the same reaction as we have written above. (Wikipedia lists a different reaction, which is not well supported by the literature.)

manwithoutborders:

clearscience:

A battery scientist’s trivial dilemma

You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)

Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:

  • 3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO

The 303/357 is a silver oxide battery having the overall reaction:

  • Zn + Ag2O = 2 Ag + ZnO

They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

Being a chemist, I’m more loyal to representing mixed oxides in the longhand format, MnO+Mn2O3. I don’t think the reaction in a battery is vigorous enough to produce “actual” Mn3O4. Is it common for battery scientist to use Mn3O4 over Mn2O3 as the product, I’m going to have to tear open a dead battery and check this on XRD. 

It’s a good point. However, if the battery is discharged at a sufficiently slow rate (20 hours or slower) you do observe the well-formed spinel structure of Mn3O4Opening the battery and using a standard XRD will result in a collection of products that are difficult to distinguish. By using a synchrotron beam to do diffraction through the battery without opening it, a good Mn3O4 structure is observed. The Clear Science staff will have a paper out about this soon … our preliminary paper on the technique is here.

We aren’t the first people to identify Mn3O4 as the slow-rate product. The Handbook of Batteries gives the same reaction as we have written above. (Wikipedia lists a different reaction, which is not well supported by the literature.)

A battery scientist’s trivial dilemma
You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)
Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:
3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO
The 303/357 is a silver oxide battery having the overall reaction:
Zn + Ag2O = 2 Ag + ZnO
They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

A battery scientist’s trivial dilemma

You may find yourself hunting through all the batteries at the drugstore, trying to find an LR44 to buy instead of a 303/357. All because you want to be ‘faithful’ to MnO2. (By the way, this particular day you won’t find one.)

Functionally, these button cells are essentially interchangeable, but they have different active materials inside them. The LR44 is an “alkaline” battery which has the overall reaction:

  • 3 MnO2 + 2 Zn = Mn3O4 + 2 ZnO

The 303/357 is a silver oxide battery having the overall reaction:

  • Zn + Ag2O = 2 Ag + ZnO

They both give you a potential of about 1.5 V. Actually, the silver oxide battery voltage is a little higher, and its capacity is a bit bigger. But if you’ve been concentrating on MnO2 for a couple years in your work … you know … your loyalty might kick in.

"In a first for laser-driven fusion, scientists at a US lab say they have reached a key milestone called fuel gain: they are producing more energy than the fuel absorbed to start the reaction."

Laser-sparked fusion power passes key milestone  |  New Scientist

Okay, okay, okay, okay, guys. Scientists at the National Ignition Facility have taken the first itty bitty baby steps towards fusion and I’m having trouble containing my excitement.

First of all, they’re using 192 laser beams, which are pointed at a gold chamber that converts the lasers into X-ray pulses, which then squeeze a small fuel pellet and make it implode and undergo fusion. That anyone ever figured out even how to do this is completely nutso.

Secondly, the lead researcher is named Omar Hurricane. I have never in my life heard a better name. He sounds like a comic book character. Please someone write a comic starring Omar Hurricane and his band of laser-wielding scientists.

And then there’s what it actually means. So far, they’ve been able to get 15 kilojoules of energy out of a fuel pellet that was blasted with 10 kilojoules. But, as The Guardian points out, much more energy is delivered by the lasers (and lost in the conversion to X-rays): “The lasers unleash nearly two megajoules of energy on their target, the equivalent, roughly, of two standard sticks of dynamite.” 

Even so, this is a hugely significant tiny step forward toward recreating the clean energy production that happens in the heart of stars.

(via chels)

Due to a peculiarity of nuclear physics, you can release energy either by 1) breaking apart heavy atoms, or 2) forcing together light atoms. Breaking apart is called fission and forcing together is called fusion. We already know how to generate energy by man-made fission, but generating energy by man-made fusion remains an aspiration. (Of course, we know how to build bombs both ways. Nuclear and thermonuclear bombs respectively.)

Essentially, solar power is fusion, though. Because the sun is a fusion reactor, and its light lands on our planet and makes everything happen. 

(via chels)

By connecting zinc and copper discs separated by brine-soaked cloth, a zinc-hydrogen cell in made. Alessandro Volta studied the effect produced when metals were connected this way. One of his papers (from 1769) was called De vi attractiva ignis electrici or “On the attractive force of electric fire.” In the 1800s the concept of a battery began to be developed. By connecting several cells, stacking them, a higher voltage is produced. The word voltage comes from his name.
This is essentially the same idea as a citrus battery, where instead of brine you have citrus juice.

By connecting zinc and copper discs separated by brine-soaked cloth, a zinc-hydrogen cell in made. Alessandro Volta studied the effect produced when metals were connected this way. One of his papers (from 1769) was called De vi attractiva ignis electrici or “On the attractive force of electric fire.” In the 1800s the concept of a battery began to be developed. By connecting several cells, stacking them, a higher voltage is produced. The word voltage comes from his name.

This is essentially the same idea as a citrus battery, where instead of brine you have citrus juice.

Batteries are electrochemical cells. Electrochemical cells are two electrochemical half-reactions coupled to each other. A zinc-hydrogen battery, which is what you make if you make a citrus battery, has:
a hydrogen-forming half-reaction that happens at 0 V
a zinc-dissolving half-reaction that happens at -0.76 V
In reality, half-reactions cannot exist independently. They must always be coupled to make a cell. This is because otherwise you have electrons without a home. 

Batteries are electrochemical cells. Electrochemical cells are two electrochemical half-reactions coupled to each other. A zinc-hydrogen battery, which is what you make if you make a citrus battery, has:

  1. a hydrogen-forming half-reaction that happens at 0 V
  2. a zinc-dissolving half-reaction that happens at -0.76 V

In reality, half-reactions cannot exist independently. They must always be coupled to make a cell. This is because otherwise you have electrons without a home. 

The Clear Science Staff got an email from a producer for National Geographic a few weeks ago, and they wanted to record us explaining how a citrus battery works. (That’s us in the video BTW.) It’s for a science/comedy show that comes out next year called Duck Quacks Don’t Echo.

You put nails made out of two different metals into some acidic fruit, like an orange. If one is zinc and one is copper, you essentially make a zinc-hydrogen cell.

The battery half-reactions are 1) zinc electrodissolution (anode):

Zn → Zn2+ + 2e-

and 2) hydrogen formation (cathode):

2H+ + 2e- → H2

The zinc electrodissolution obviously happens on the surface of the zinc nail, and releases electrons. These electrons are at a low potential and want to flow to someplace at high potential. The hydrogen formation has a higher potential, and occurs when the protons (H+) in the fruit acid meet the electrons at the copper nail to form hydrogen gas (H2).

So if the two nails are connected, electrons will want to flow from the zinc nail to the copper nail. In between these two nails you place something like a cell phone. Flowing electrons are electricity, and so when they flow through the phone charger it’s electricity to charge the phone. This is how batteries work.

Carbon bonded to other carbon, which is a kind of reduced carbon, is what we use for energy. What kind of energy you ask? Well, how about food, which is a kind of reduced carbon. Food is sugars, proteins, fats, etc, which are all carbon chains. Also how about fossil fuels like gasoline (let’s call that octane). The bonds between the carbons have energy in them, and we get that energy out by digesting them or burning them.
Other carbon chains you might like: animals (which you eat), plants (which you eat), you, everyone you know, fossil fuels (which you burn), most polymers like plastic bags, soda bottles, and on and on and on.
The Clear Science staff is kind of over-simplifying here: there are other elements in these molecular chains, like H, O, and N. But anything organic is based on carbon chains, so you can think of them as being reduced carbon.

Carbon bonded to other carbon, which is a kind of reduced carbon, is what we use for energy. What kind of energy you ask? Well, how about food, which is a kind of reduced carbon. Food is sugars, proteins, fats, etc, which are all carbon chains. Also how about fossil fuels like gasoline (let’s call that octane). The bonds between the carbons have energy in them, and we get that energy out by digesting them or burning them.

Other carbon chains you might like: animals (which you eat), plants (which you eat), you, everyone you know, fossil fuels (which you burn), most polymers like plastic bags, soda bottles, and on and on and on.

The Clear Science staff is kind of over-simplifying here: there are other elements in these molecular chains, like H, O, and N. But anything organic is based on carbon chains, so you can think of them as being reduced carbon.

The Clear Science staff was going to answer the question "Is there a decay rate in heat at distance from a flame/heat source?" To do that let’s consider one way that heat transports from one place to another: conduction.
Heat is energy. Say we have a flame on the left and no flame on the right. The flame is there because some chemical reaction is happening: chemical bonds are breaking and their energy is being liberated. Because of this the temperature of the flame is high, like 1500 degrees. On the right temperature is only room temperature or 20 degrees.
Heat moves by conduction from high temperatures to low ones. This is a basic property of the universe, and it is described by Fourier’s law. Written above in “math language,” what it says in English is "heat flux is proportional to the negative of the temperature gradient." Or: heat fluxes from high temp to low.

The Clear Science staff was going to answer the question "Is there a decay rate in heat at distance from a flame/heat source?" To do that let’s consider one way that heat transports from one place to another: conduction.

Heat is energy. Say we have a flame on the left and no flame on the right. The flame is there because some chemical reaction is happening: chemical bonds are breaking and their energy is being liberated. Because of this the temperature of the flame is high, like 1500 degrees. On the right temperature is only room temperature or 20 degrees.

Heat moves by conduction from high temperatures to low ones. This is a basic property of the universe, and it is described by Fourier’s law. Written above in “math language,” what it says in English is "heat flux is proportional to the negative of the temperature gradient." Or: heat fluxes from high temp to low.

We mentioned a recent paper that examined silicon/carbon fibers for use in batteries. Shown above is a TEM image from the paper. From it you can tell the fibers are essentially hollow carbon fibers with a layer of silicon around the outside edge.
Transmission electron microscopes (TEMs) work by shooting a beam of electrons through a sample. The sample has to be quite thin to let the electrons through, but since these fibers are around 100 nm thick that is fine. The important thing is that the image is made with electrons. This is different than the sort of images you’re used to, such as those made with cameras, regular microscopes, or even your eyes: all of those images are made by light. Electrons have a smaller wavelength than light, and so electron microscopes work at extremely high resolution: in some cases you can make out individual atoms with them.
Why would anyone care about silicon-coated nano-fibers? Because lithium ions can be stored inside silicon, and that makes these fibers well-suited to storing lithium for lithium ion batteries. Some researchers think we may be able to extend the life of batteries using these.

We mentioned a recent paper that examined silicon/carbon fibers for use in batteries. Shown above is a TEM image from the paper. From it you can tell the fibers are essentially hollow carbon fibers with a layer of silicon around the outside edge.

Transmission electron microscopes (TEMs) work by shooting a beam of electrons through a sample. The sample has to be quite thin to let the electrons through, but since these fibers are around 100 nm thick that is fine. The important thing is that the image is made with electrons. This is different than the sort of images you’re used to, such as those made with cameras, regular microscopes, or even your eyes: all of those images are made by light. Electrons have a smaller wavelength than light, and so electron microscopes work at extremely high resolution: in some cases you can make out individual atoms with them.

Why would anyone care about silicon-coated nano-fibers? Because lithium ions can be stored inside silicon, and that makes these fibers well-suited to storing lithium for lithium ion batteries. Some researchers think we may be able to extend the life of batteries using these.

Let’s talk about some recent science work on lithium-ion batteries, and the journal article reporting the work. Scientists tell each other about their work through articles (or “papers”). This one is called: In Situ TEM Investigation of Congruent Phase Transition and Structural Evolution of Nanostructured Silicon/Carbon Anode for Lithium Ion Batteries.
Sometimes titles are hard to understand unless you break them down into pieces:
TEM is transmission electron microscopy
in situ means they’re doing some experiment and watching it happen inside the TEM
phase transition means atoms are going from one arrangement to another
structural evolution means the experiment is changing the material somehow
nanostructured means the size they’re looking at is less than 1000 nanometers
an anode is the negative electrode in a battery
lithium ion batteries are like computer or cell phone batteries
This paper is in a journal called Nano Letters. Under the title is a list of names. These are the authors. Basically that is everyone who did the science work, dreamed it up, paid for it, or wrote the paper. (This C&EN article on the paper summarizes and contains a link to it.)

Let’s talk about some recent science work on lithium-ion batteries, and the journal article reporting the work. Scientists tell each other about their work through articles (or “papers”). This one is called: In Situ TEM Investigation of Congruent Phase Transition and Structural Evolution of Nanostructured Silicon/Carbon Anode for Lithium Ion Batteries.

Sometimes titles are hard to understand unless you break them down into pieces:

  • TEM is transmission electron microscopy
  • in situ means they’re doing some experiment and watching it happen inside the TEM
  • phase transition means atoms are going from one arrangement to another
  • structural evolution means the experiment is changing the material somehow
  • nanostructured means the size they’re looking at is less than 1000 nanometers
  • an anode is the negative electrode in a battery
  • lithium ion batteries are like computer or cell phone batteries

This paper is in a journal called Nano Letters. Under the title is a list of names. These are the authors. Basically that is everyone who did the science work, dreamed it up, paid for it, or wrote the paper. (This C&EN article on the paper summarizes and contains a link to it.)