低场核磁共振测量孔径原理

低场核磁共振测量孔径原理
英文回答：
Nuclear Magnetic Resonance Measurement of Pore Size.
Nuclear magnetic resonance (NMR) is a powerful tool for characterizing the structure of materials, including the size and shape of pores. NMR measurements can be used to determine the pore size distribution, which is important
for understanding the transport properties of materials.
The most common NMR method for measuring pore size is the pulsed-field gradient (PFG) method. In this method, a pulsed magnetic field gradient is applied to the sample, which causes the spins of the hydrogen atoms in the pore fluid to precess at different rates depending on their location in the pore. The resulting signal is then analyzed to determine the pore size distribution.
The PFG method can be used to measure pores with sizes
ranging from a few nanometers to several microns. The accuracy of the measurement depends on the strength of the magnetic field gradient and the duration of the pulse.
Another NMR method for measuring pore size is the relaxation method. In this method, the relaxation times of the hydrogen atoms in the pore fluid are measured. The relaxation times are affected by the size and shape of the pores, and can therefore be used to determine the pore size distribution.
The relaxation method is less accurate than the PFG method, but it can be used to measure pores with sizes ranging from a few nanometers to several hundred microns.
中文回答：
核磁共振测孔原理。

核磁共振（NMR）是一种表征材料结构的强大工具，包括孔隙的尺寸和形状。

NMR测量可用于确定孔隙尺寸分布，这对于理解材料
的输运特性非常重要。

测量孔隙尺寸最常用的NMR方法是脉冲场梯度（PFG）法。

在此方法中，将脉冲磁场梯度施加到样品上，这会导致孔隙流体中氢原子的自旋根据其在孔隙中的位置以不同的速率进动。

然后分析所得信号以确定孔隙尺寸分布。

PFG方法可用于测量尺寸从几纳米到几微米的孔隙。

测量的准确性取决于磁场梯度的强度和脉冲的持续时间。

另一种测量孔隙尺寸的NMR方法是弛豫法。

在此方法中，测量孔隙流体中氢原子的弛豫时间。

弛豫时间受孔隙的尺寸和形状的影响，因此可用于确定孔隙尺寸分布。

弛豫法不如PFG方法准确，但它可用于测量尺寸从几纳米到几百微米的孔隙。