Any hints on how to derive the glass viscosity? n=n(0)exp(Q/RT)?

In summary, the glass viscosity can be derived using the equation n=n(0)exp(Q/RT), which applies to thermally activated processes. This equation describes the likelihood of a particle reaching a certain energy, which is connected to the ability of molecules in a viscous fluid to break bonds and move independently.
  • #1
nomisme
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Any hints on how to derive the glass viscosity? n=n(0)exp(Q/RT)?
 
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  • #2
Hi nomisme, welcome to PF. This is a very fundamental equation that applies to all events that involve an activation energy, or an energy "hump" that must be overcome for the process or reaction to occur (these are called thermally activated processes). In the case of viscosity, we're talking about molecules sliding past each other. As the bulk fluid flows, the molecules move along an energy landscape with valleys and peaks corresponding to locations where it's more or less energetically favorable to bond to adjacent molecules. At high temperatures, any bonds are easily broken and each molecule traverses this landscape easily; at lower temperatures, the fluid is more viscous because the molecules are less likely to break these bonds.

The equation describes the general likelihood that a particle at a given temperature will reach a particular energy. It should be clear that this is directly connected to the ability of a molecule in a viscous fluid to break the bonds with its neighbors and continue to move independently. Does this help?
 
  • #3


There are several ways to derive the glass viscosity using the equation n=n(0)exp(Q/RT). One approach is to use the Arrhenius equation, which relates the rate of a chemical reaction to temperature and activation energy. In this case, the viscosity of glass can be considered a type of "reaction" that is affected by temperature and activation energy. By measuring the viscosity at different temperatures and solving for the activation energy using the Arrhenius equation, the viscosity at any given temperature can be calculated. Another approach is to use the Vogel-Fulcher-Tammann (VFT) equation, which takes into account the glass transition temperature and fragility of the material. This equation can be used to derive the viscosity of glass at different temperatures by fitting experimental data to the VFT equation. It is important to note that both of these methods assume that the glass behaves as a simple liquid, and may not accurately predict the viscosity at very low temperatures or high pressures. Other factors such as composition and structure may also affect the viscosity of glass and should be considered when deriving this property.
 

Related to Any hints on how to derive the glass viscosity? n=n(0)exp(Q/RT)?

1. How do you determine the value of n in the equation n=n(0)exp(Q/RT)?

The value of n can be determined experimentally by measuring the viscosity of the glass at different temperatures and using the equation to calculate the value of n for each data point. The values can then be plotted on a graph and the slope of the line can be used to determine the value of n.

2. What is the significance of the variables Q and R in the equation?

Q and R are constants that represent the activation energy and gas constant, respectively. These values are important in determining the viscosity of glass as they take into account the energy required for molecules to move and the influence of temperature on this movement.

3. Can this equation be used for all types of glass?

Yes, this equation can be used for all types of glass as long as the viscosity is measured at different temperatures and the values are within the temperature range for which the equation is valid.

4. How accurate is this equation in predicting glass viscosity?

This equation is a simplified model and may not accurately predict the viscosity of glass in all cases. Factors such as composition and impurities in the glass can also affect its viscosity. However, it is a widely used equation in the scientific community and can provide a good estimate of the glass viscosity.

5. What is the practical application of this equation?

This equation is commonly used in the glass industry to determine the viscosity of glass at different temperatures, which is important in the production and processing of glass. It can also be used in research and development to study the properties of different types of glass and their behavior under different conditions.

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