CN114047092B - Method for measuring free water content of cell wall of balance wood and application thereof - Google Patents
Method for measuring free water content of cell wall of balance wood and application thereof Download PDFInfo
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- CN114047092B CN114047092B CN202111355942.8A CN202111355942A CN114047092B CN 114047092 B CN114047092 B CN 114047092B CN 202111355942 A CN202111355942 A CN 202111355942A CN 114047092 B CN114047092 B CN 114047092B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder
- G01N5/045—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder for determining moisture content
Abstract
The invention belongs to the technical field of wood moisture analysis, and provides a method for measuring free water content of a cell wall during moisture absorption balance or desorption balance of wood and application thereof. The method provided by the invention takes balanced wood (wood with water content less than or equal to 25%, desorption balanced wood or moisture absorption balanced wood) as a measurement standard, and free water does not exist in the cell cavities of the balanced wood, so that the cell wall free water can be distinguished by measuring the nuclear magnetic resonance longitudinal relaxation time data and then utilizing the difference of the longitudinal relaxation time of the cell wall and the cell cavity combined water and the cell wall free water. And quantifying the free water of the cell wall based on the longitudinal relaxation time data by using the formula 1, so as to obtain the content of the free water of the cell wall in the balanced wood. According to the invention, by strictly setting parameters for measuring the longitudinal relaxation time T1 data of the balance timber, accurate measurement results can be ensured.
Description
Technical Field
The invention relates to the technical field of wood moisture analysis, in particular to a method for measuring the free water content of cell walls of balanced wood and application thereof.
Background
The traditional theory of wood science holds that the water in the wood cell wall is bound water and free water is not present. Nakamura et al (1981) and Berthold et al (1996) differentiated the inclusion of freezable and non-freezable bound water in the wood cell wall using a differential scanning calorimeter. More time domain nmr two-dimensional experiments showed that: the wood cell wall contains two moisture states. The existing references mostly measure the moisture content in the wood cell wall and cell cavity by transverse relaxation time and consider the moisture content in the cell wall as bound water inside the wood and the moisture content in the cell cavity as free water inside the wood. The measurement of the moisture inside the wood is performed by the transverse relaxation time because the transverse relaxation time of the moisture in the cell cavity is long and the moisture relaxation time in the cell wall is short, and the data is easy to interpret. Whereas longitudinal relaxation times describe the process of energy exchange of the spin system with the surrounding environment, the data composition is complex and difficult to analyze, so there is little literature on measuring and analyzing longitudinal relaxation times.
Zhang and Balcom et al (Zhang, m., balcom, b.j. (2022) Magnetic Resonance microscope. Instrumentation and Applications in Life Science and Energy Research Engineering, "Magnetic Resonance Studies of Water in Wood Materials", wiley-VCH weinheim.) propose that bound water and free water are both present in the wood cell wall based on nuclear magnetic resonance relaxation theory, and that the bound water of the cell wall should be water on the inner surface of the cell wall pores; the water in the middle of the cell wall pores, i.e. the water which is not contacted with the main component of the wood cell wall, is free water; and the water content of the inner surfaces of the wood cell cavities is considered to be bound water by nature. However, since the transverse relaxation time of the cell wall bound water is very close to the transverse relaxation time of the free water in the cell wall pores, it is impossible to distinguish the bound water from the free water of the cell wall; resulting in an undetectable free water content of the cell wall.
Disclosure of Invention
The present invention is directed to a method for measuring the free water content of the cell wall of balance wood and the application thereof. The method provided by the invention can accurately measure the free water content of the cell wall of the balance wood, and solves the problem that the free water content in the cell wall cannot be measured.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for measuring the free water content of the cell wall of balanced wood, which comprises the following steps:
providing balanced wood; the balance wood comprises wood with the water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
determining longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to a formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: s (t) is the signal obtained by inverting the recovery pulse sequence, ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of signal excitation to one of the echoes in the reverse recovery pulse sequence; ε (t) is the noise signal;
measuring the balance weight W2 and the absolute dry weight W1 of the balance wood;
the cell wall free water content of the balance wood was calculated using equation 2:
wf= (W2-W1) a 11/(a11+a12) formula 2;
in equation 2: wf is the free water content of the cell wall in grams; w2 is the balance weight of the balance wood, and the unit is gram; w1 is the absolute dry weight of balanced wood, and the unit is gram;
the parameters for determining the longitudinal relaxation time T1 data of the balanced timber comprise: adopting reverse recovery pulse sequence; number of scans is 2 n Secondarily, n is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval from the start of signal excitation to one echo in the reverse recovery pulse sequence is 1 ms-3000 ms; the number of sampling points is 16-32, and the sampling points are distributed in pairs at equal intervals.
Preferably, the method for obtaining desorption-balanced wood comprises the following steps:
carrying out desorption balance on original wood to obtain the desorption balanced wood;
the temperature of the desorption equilibrium is 5-80 ℃ and the relative humidity is 30-99.99%.
Preferably, the method for obtaining the moisture absorption balanced wood comprises the following steps:
carrying out moisture absorption balancing on the desorption balanced wood to obtain the moisture absorption balanced wood;
the temperature of the moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
Preferably, the method for obtaining the moisture absorption balanced wood comprises the following steps:
performing absolute drying treatment on the original wood to obtain absolute dried wood; the absolute temperature is 100-105 ℃;
carrying out moisture absorption balance on the absolute dry wood to obtain the moisture absorption balanced wood; the temperature of the moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
Preferably, the method further comprises: cell wall and cell cavity bound water content was obtained using equation 3:
wb= (W2-W1) a 12/(a11+a12) formula 3;
in formula 3, wb is the cell wall and cell cavity bound water content, in grams; w2 is the weight of the balance wood, and the unit is gram; w1 is the weight of the absolute dry wood in grams.
The invention also provides an application of the method for measuring the free water content of the cell wall of the balance wood in the determination of the free water content of the balance hydrophilic pore material.
Preferably, the equilibrium hydrophilic pore material comprises a hygroscopic equilibrium hydrophilic pore material or a desorbing equilibrium hydrophilic pore material.
The invention provides a method for measuring the free water content of the cell wall of balanced wood, which comprises the following steps: providing balanced wood; the balance wood comprises wood with the water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
determining longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to a formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: s (t) is the signal obtained by inverting the recovery pulse sequence, ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of signal excitation to one of the echoes in the reverse recovery pulse sequence; ε (t) is the noise signal;
measuring the balance weight W2 and the absolute dry weight W1 of the balance wood;
the cell wall free water content of the balance wood was calculated using equation 2:
wf= (W2-W1) a 11/(a11+a12) formula 2;
in equation 2: wf is the free water content of the cell wall in grams; w2 is the balance weight of the balance wood, and the unit is gram; w1 is the absolute dry weight of balanced wood, and the unit is gram;
the parameters for determining the longitudinal relaxation time T1 data of the balanced timber comprise: adopting reverse recovery pulse sequence; number of scans is 2 n Secondarily, n is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval from the start of signal excitation to one echo in the reverse recovery pulse sequence is 1 ms-3000 ms; the number of sampling points is 16-32, and the sampling points are distributed in pairs at equal intervals.
The method provided by the invention takes balanced wood (wood with water content less than or equal to 25%, desorption balanced wood or moisture absorption balanced wood) as a measurement standard, and free water does not exist in the cell cavities of the balanced wood, so that the cell wall free water can be distinguished by measuring the nuclear magnetic resonance longitudinal relaxation time data and then utilizing the difference of the longitudinal relaxation time of the cell wall and the cell cavity combined water and the cell wall free water. And quantifying the free water of the cell wall based on the longitudinal relaxation time data by using the formula 1, so as to obtain the content of the free water of the cell wall in the balanced wood. According to the invention, by strictly setting parameters for measuring the longitudinal relaxation time T1 data of the balance timber, accurate measurement results can be ensured.
Further, the present invention obtains the cell wall and cell cavity bound water content by equation 3.
The invention also provides an application of the method for measuring the free water content of the cell wall of the balance wood in the determination of the free water content of the balance hydrophilic pore material. The method is not only suitable for wood, but also suitable for measuring the free water content in all balanced hydrophilic pore materials.
Detailed Description
Term interpretation:
bound water (Bound water): also called "adsorption water", is water that hydrogen bonds with adsorption sites on the main component of the cell wall.
Free water (Free water): the moisture present in the cell cavity is called free water.
Longitudinal relaxation time (longitudinal relaxation time): also known as spin lattice relaxation time (spin-lattice relaxation time), is the relaxation time that the longitudinal magnetization vector undergoes to recover from a minimum to 63% of equilibrium. Is a characteristic quantity for representing the decay speed of the longitudinal magnetization vector.
Moisture absorption of wood: when the water vapor pressure in the wood cell wall microcapillaries is smaller than the water vapor partial pressure of the surrounding air, the microcapillaries absorb moisture from the surrounding air, and the phenomenon that the microcapillaries system in the cell wall can absorb moisture from the humid air is called moisture absorption.
Desorption of wood: when the partial pressure of water vapor in the wood cell wall microcapillaries is greater than the partial pressure of water vapor in the ambient air, the microcapillary system is capable of evaporating moisture into the ambient air, a phenomenon known as desorption.
The invention provides a method for measuring the free water content of the cell wall of balanced wood, which comprises the following steps:
providing balanced wood; the balance wood comprises wood with the water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
determining longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to a formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: s (t) is the signal obtained by inverting the recovery pulse sequence, ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of signal excitation to one of the echoes in the reverse recovery pulse sequence; ε (t) is the noise signal;
measuring the balance weight W2 and the absolute dry weight W1 of the balance wood;
the cell wall free water content of the balance wood was calculated using equation 2:
wf= (W2-W1) a 11/(a11+a12) formula 2;
in equation 2: wf is the free water content of the cell wall in grams; w2 is the balance weight of the balance wood, and the unit is gram; w1 is the absolute dry weight of balanced wood, and the unit is gram;
the parameters for determining the longitudinal relaxation time T1 data of the balanced timber comprise: adopting reverse recovery pulse sequence; number of scans is 2 n Secondarily, n is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval from the start of signal excitation to one echo in the reverse recovery pulse sequence is 1 ms-3000 ms; the number of sampling points is 16-32, and the sampling points are distributed in pairs at equal intervals.
In the present invention, the raw materials used in the present invention are preferably commercially available products unless otherwise specified.
The present invention provides balanced wood.
In the present invention, the equilibrium wood includes wood having a water content of 25% or less, desorption-equilibrium wood, or moisture-absorption-equilibrium wood.
In the present invention, the method for obtaining desorption-balanced wood preferably comprises the steps of:
and carrying out desorption balance on the original wood to obtain the desorption balanced wood. The invention does not limit the water content of the original wood, and the wood with any water content can be used. In the present invention, the temperature of the desorption equilibrium is preferably 5 to 80 ℃, and the relative humidity is preferably 30 to 99.99%; the invention does not limit the desorption balance time, and can ensure that the weight of the original wood is not changed any more under the specific temperature and relative humidity.
In the present invention, the method for obtaining moisture-absorption-balanced wood preferably comprises the steps of:
and carrying out moisture absorption balance on the desorption balanced wood to obtain the moisture absorption balanced wood. In the present invention, the desorption equilibrium wood is preferably the desorption equilibrium wood prepared by the above technical scheme. In the present invention, the temperature of the moisture absorption equilibrium is preferably 5 to 80 ℃; the relative humidity is preferably 30 to 99.99%. The time of the moisture absorption balance is not particularly limited, and the weight of the wood with the moisture absorption balance can not change any more under the specific temperature and relative humidity.
In the present invention, the method for obtaining moisture-absorption-balanced wood preferably further comprises the steps of:
performing absolute drying treatment on the original wood to obtain absolute dried wood;
and carrying out moisture absorption balance on the absolute dry wood to obtain the moisture absorption balanced wood.
In the invention, the temperature of the absolute drying treatment is preferably 100-105 ℃; the invention does not limit the time of the absolute drying, and the absolute drying is only required to reach constant weight. In the present invention, the oven drying is preferably performed in an oven. In the present invention, the temperature of the moisture absorption equilibrium is preferably 5 to 80 ℃; the relative humidity is preferably 30 to 99.99%. The time of the moisture absorption balance is not particularly limited, and the weight of the wood with the moisture absorption balance can not change any more under the specific temperature and relative humidity.
After providing the balancing timber, the balancing timber can be weighed to obtain a balancing weight W2 of the balancing timber.
In the present invention, the cell cavities of the balance wood do not contain free water, but only cell wall bound water and cell wall free water.
After obtaining the equilibrium timber, the present invention determines the longitudinal relaxation time T1 data of the equilibrium timber.
In the present invention, the parameters for determining the longitudinal relaxation time T1 data of the balance wood include: adopting reverse recovery pulse sequence; number of scans is 2 n Secondarily, n is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval from the start of signal excitation to one echo in the reverse recovery pulse sequence is 1 ms-3000 ms; the number of sampling points is 16-32, and the sampling points are distributed in pairs at equal intervals.
After the longitudinal relaxation time T1 data of the balance timber are obtained, fitting the longitudinal relaxation time T1 data according to a formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude 12 of the T11 value; wherein T11< T12;
in equation 1: s (t) is the signal strength, ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of signal excitation to one of the echoes in the reverse recovery pulse sequence; ε (t) is the noise signal.
In the invention, the longitudinal relaxation time T1 data of the balance timber comprises signal intensity corresponding to each sampling point at different time, and the unit of time is s.
In the present invention, the instrument for determining the longitudinal relaxation time T1 data of the balance wood is preferably a time domain nuclear magnetic resonance spectrometer.
The absolute dry weight W1 of the balance wood was determined. In the present invention, the oven-dried weight W1 of the balance wood is preferably obtained by oven-drying the balance wood to obtain oven-dried wood and weighing it to an accuracy of 0.001g. In the invention, the absolute temperature is preferably 100-105 ℃; the invention does not limit the time of the absolute drying, and the absolute drying is only required to reach constant weight. In the present invention, the oven drying is preferably performed in an oven.
After W1, W2, A11 and A12 are obtained, the free water content of the cell wall in the balanced wood is calculated by using a formula 2:
wf= (W2-W1) a 11/(a11+a12) formula 2;
in equation 2: wf is the free water content of the cell wall in grams; w2 is the balance weight of the balance wood, and the unit is gram; w1 is the absolute dry weight of the balance wood in grams.
The invention preferably further comprises: cell wall and cell cavity bound water content was obtained using equation 3:
wb= (W2-W1) a 12/(a11+a12) formula 3;
in formula 3, wb is the cell wall and cell cavity bound water content, in grams; w2 is the weight of the balance wood, and the unit is gram; w1 is the weight of the absolute dry wood in grams.
The invention also provides an application of the method for measuring the free water content of the cell wall of the balance wood in the determination of the free water content of the balance hydrophilic pore material.
In the present invention, the equilibrium hydrophilic pore material includes a hygroscopic equilibrium hydrophilic pore material or a desorbing equilibrium hydrophilic pore material. The method for obtaining the moisture absorption balance hydrophilic pore material or the desorption balance hydrophilic pore material is not particularly limited, and can be well known to those skilled in the art.
In the present invention, the free water preferably includes free water in micropores and mesopores of the hydrophilic pore material.
The method for measuring the free water content of the cell wall at the time of moisture absorption balance or desorption balance of wood and the application thereof provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Weighing the poplar test piece after the poplar test piece is absolute dried, wherein the absolute dry weight is 0.782g; placing the absolute dry test piece into a constant temperature and humidity box with the temperature of 40 ℃ and the relative humidity of 31.6%, 43.2%, 53.2%, 74.7%, 82.3% and 98.2% in sequence, and enabling the test piece to sequentially reach moisture absorption balance in the relative humidity environment to obtain a moisture absorption balance test piece; the moisture absorption balance test piece is taken out, weighed, placed into a sample tube with the diameter of 18mm, and then placed into a German Bruce time domain nuclear magnetic resonance spectrometer (model is Minispec mq 20) for measuring the longitudinal relaxation time (T1). The longitudinal relaxation time (T1) measurement parameters include: the number of scans was 4, the cyclic delay time was 2 seconds, the recovery time was 1 to 3000 milliseconds, the number of sampling points was 20, and the sampling points were equally distributed in pairs.
Fitting the obtained longitudinal relaxation time T1 data according to the formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof, and calculating the free water content of the cell wall of the balanced timber by using the formula 2, wherein the obtained results are shown in the table 1.
TABLE 1 cell wall free Water content of poplar at equilibrium by moisture absorption at different relative humidity
Example 2
Weighing a pine sample after absolute drying, wherein the absolute dry weight is 0.880g; placing the absolute dry test piece into a constant temperature and humidity box with the temperature of 40 ℃ and the relative humidity of 31.6%, 43.2%, 53.2%, 74.7%, 82.3% and 98.2% in sequence, and enabling the test piece to sequentially reach moisture absorption balance in the relative humidity environment to obtain a moisture absorption balance test piece; the moisture absorption balance test piece is taken out, weighed, placed into a sample tube with the diameter of 18mm, and then placed into a German Bruce time domain nuclear magnetic resonance spectrometer (model is Minispec mq 20) for measuring the longitudinal relaxation time (T1). Parameters measured by the longitudinal relaxation time (T1) used: the number of scans was 4, the cyclic delay time was 2 seconds, the recovery time was 1 to 3000 milliseconds, the number of sampling points was 20, and the sampling points were equally distributed in pairs. Fitting the obtained longitudinal relaxation time T1 data according to the formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof, and calculating the free water content of the cell wall of the balanced timber by using the formula 2, wherein the obtained results are shown in the table 2.
TABLE 2 free Water content of cell wall of pine at moisture absorption equilibrium at different relative humidity
Example 3
The poplar green wood test piece is placed in a constant temperature and humidity box with the temperature of 40 ℃ and the relative humidity of 98.2%, 82.3%, 74.7%, 53.2%, 43.2% and 31.6% in sequence, the test piece is enabled to reach desorption equilibrium in the relative humidity environment in sequence, when the desorption equilibrium is reached, the test piece is taken out, weighed and placed in a sample tube with the diameter of 18mm, and then the sample tube with the test piece is placed in a German Bruce time domain nuclear magnetic resonance spectrometer (model Minispec mq 20) for T1 measurement. Parameters used: the number of scans was 4, the cyclic delay time was 2 seconds, the recovery time was 1 to 3000 milliseconds, the number of sampling points was 20, and the sampling points were equally distributed in pairs. After the last T1 measurement was completed, the test piece was weighed after absolute drying, and the absolute dry weight was 0.782g. Fitting the obtained longitudinal relaxation time T1 data according to the formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof, and calculating the free water content of the cell wall of the balanced timber by using the formula 2 to obtain the result shown in the table 3.
TABLE 3 free Water content of cell wall of poplar at equilibrium for desorption at different relative humidity
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (7)
1. A method of measuring the free water content of the cell wall of a balanced wood comprising the steps of:
providing balanced wood; the balance wood comprises wood with the water content less than or equal to 25%, desorption balance wood or moisture absorption balance wood;
determining longitudinal relaxation time T1 data of the balanced wood; fitting the longitudinal relaxation time T1 data according to a formula 1 to obtain a T11 value and a magnitude A11 and a T12 value and a magnitude A12 thereof; wherein T11< T12;
in equation 1: s (t) is the signal obtained by inverting the recovery pulse sequence, ti is the longitudinal relaxation time of the ith moisture component in seconds; ai represents the magnitude of the ith moisture component, ti is the time interval in seconds between the start of signal excitation to one of the echoes in the reverse recovery pulse sequence; epsilon (ti) is the noise signal;
measuring the balance weight W2 and the absolute dry weight W1 of the balance wood;
the cell wall free water content of the balance wood was calculated using equation 2:
wf= (W2-W1) a 11/(a11+a12) formula 2;
in equation 2: wf is the free water content of the cell wall in grams; w2 is the balance weight of the balance wood, and the unit is gram; w1 is the absolute dry weight of balanced wood, and the unit is gram;
the parameters for determining the longitudinal relaxation time T1 data of the balanced timber comprise: adopting reverse recovery pulse sequence; number of scans is 2 n Secondarily, n is more than or equal to 2 and less than or equal to 8; the cycle delay time is 1-2 s; the time interval from the start of signal excitation to one echo in the reverse recovery pulse sequence is 1 ms-3000 ms; the number of sampling points is 16-32, and the sampling points are distributed in pairs at equal intervals.
2. The method according to claim 1, characterized in that the method for obtaining desorption balanced wood comprises the steps of:
carrying out desorption balance on original wood to obtain the desorption balanced wood;
the temperature of the desorption equilibrium is 5-80 ℃ and the relative humidity is 30-99.99%.
3. The method according to claim 1 or 2, characterized in that the method for obtaining moisture-absorbing balanced wood comprises the steps of:
carrying out moisture absorption balancing on the desorption balanced wood to obtain the moisture absorption balanced wood;
the temperature of the moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
4. The method according to claim 1, wherein the method for obtaining moisture-absorbing equilibrium wood comprises the steps of:
performing absolute drying treatment on the original wood to obtain absolute dried wood; the absolute temperature is 100-105 ℃;
carrying out moisture absorption balance on the absolute dry wood to obtain the moisture absorption balanced wood; the temperature of the moisture absorption balance is 5-80 ℃; the relative humidity is 30-99.99%.
5. The method as recited in claim 1, further comprising: cell wall and cell cavity bound water content was obtained using equation 3:
wb= (W2-W1) a 12/(a11+a12) formula 3;
in formula 3, wb is the cell wall and cell cavity bound water content, in grams; w2 is the weight of the balance wood, and the unit is gram; w1 is the weight of the absolute dry wood in grams.
6. Use of the method for measuring the free water content of the cell wall of balance wood according to any one of claims 1 to 5 for determining the free water content in balance hydrophilic pore materials.
7. The use of claim 6, wherein the equilibrium hydrophilic pore material comprises a hygroscopic equilibrium hydrophilic pore material or a desorbing equilibrium hydrophilic pore material.
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| CN103954921A (en) * | 2014-03-13 | 2014-07-30 | 中国科学院电工研究所 | Nuclear magnetic resonance detection method of nanocomposite |
| CN110031495A (en) * | 2019-03-21 | 2019-07-19 | 南京林业大学 | A method of based on magnetic resonance detection engineering bamboo and wood materials crackle |
| CN110618159A (en) * | 2019-11-05 | 2019-12-27 | 湖北民族大学 | LF-NMR determination method for water content of nanmu seeds |
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| CN103954921A (en) * | 2014-03-13 | 2014-07-30 | 中国科学院电工研究所 | Nuclear magnetic resonance detection method of nanocomposite |
| CN110031495A (en) * | 2019-03-21 | 2019-07-19 | 南京林业大学 | A method of based on magnetic resonance detection engineering bamboo and wood materials crackle |
| CN110618159A (en) * | 2019-11-05 | 2019-12-27 | 湖北民族大学 | LF-NMR determination method for water content of nanmu seeds |
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