Tetsuya Inagaki

Difference of the Crystal Structure of Cellulose in Wood after Hydrothermal and Aging Degradation: A NIR Spectroscopy and XRD Study

The change of crystalline structure in hydrothermally treated hinoki wood was investigated by means of Fourier-transform near-infrared spectroscopy in combination with a deuterium exchange method and X-ray diffraction. The results were compared with analogous data of dry-exposed archeological wood taken from an old wooden temple. Although the decomposition of the amorphous regions in cellulose and hemicelluloses, which corresponds to an increase of the degree of crystallinity, was observed for both, archeologically and hydrothermally treated wood, the increase of crystallite thickness was confirmed only for hydrothermally treated wood. The increase of the average size of crystallites corresponds well to the measured decrease of the deuteration accessibility of the crystalline regions. As the accessibility of the crystalline regions decreased for both, D(2)O and t-butanol, it is assumed that due to the expansion of the crystalline domains by hydrothermal treatment several elementary fibrils are arranged at distances below 0.3 nm.

Magnetovolume effects in manganese nitrides with antiperovskite structure

Abstract Magnetostructural correlations in antiperovskite manganese nitrides were investigated systematically for stoichiometric and solid solution Mn3Cu1−xAxN (A = Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, In, Sn or Sb). This class of nitrides is attracting great attention because of their giant negative thermal expansion, which is achieved by doping Ge or Sn into the A site as a relaxant of the sharp volume contraction on heating (spontaneous volume magnetostriction ωs) because of the magnetovolume effects. The physical background of large ωs and mechanism of how the volume contraction becomes gradual with temperature are central concerns for the physics and applications of these nitrides. An entire dataset of thermal expansion, crystal structure and magnetization demonstrates that the cubic triangular antiferromagnetic state is crucial for large ωs. The intimate relationship between ωs and the magnetic structure is discussed in terms of geometrical frustration related to the Mn6N octahedron and magnetic stress concept. The results presented herein also show that ωs depends on the number of d electrons in the A atom, suggesting the important role of the d orbitals of the A atom. Not all the dopants in the A site, but the elements that disturb the cubic triangular antiferromagnetic state, are effective in broadening the volume change. This fact suggests that instability neighboring the phase boundary is related to the broadening. The relation between the gradual volume change and the local structure anomaly is suggested by recent microprobe studies.

Near-infrared spectroscopic monitoring of the water adsorption/desorption process in modern and archaeological wood.

We investigated the adsorption/desorption mechanism of water and the variation of water adsorption for modern and archaeological wood using near-infrared spectroscopy. A mixture model of water was used to decompose the near-infrared difference spectra into three components (free water molecules (S0), those with one OH group engaged in hydrogen bonding (S1), and those with two OH groups engaged in hydrogen bonding (S2)) based on a principal component analysis. The variations of each water component with relative humidity could be explained by proposing a model that describes water absorption in three stages. It was concluded that the aging phenomenon in wood is due to the decrease of adsorption sites on hemicellulose and amorphous cellulose.

Conversion of magnetic structure by slight dopants in geometrically frustrated antiperovskite Mn3GaN

We found that a few percent of Fe dopants at the Mn sites alters the antiferromagnetic spin structure of Mn3GaN and induces a first-order antiferromagnetic-ferromagnetic phase transition accompanied by a large volume change. The drastic conversion of the spin alignment originates from phase competition due to a geometrical frustration in the Mn6N octahedron. This result demonstrates that the magnetic and other unique related properties of manganese antiperovskites are controllable by element substitution. Comparing with the ferromagnetic state in Mn3Ga(N1−xCx), we discuss a possible spin structure that accounts for the conversion of the magnetic states.

Near-infrared spectroscopic investigation of the hydrothermal degradation mechanism of wood as an analogue of archaeological objects. Part I: softwood.

The degradation mechanism of softwood due to the variation of strength was analyzed in conjunction with spectroscopy and chemometrics, where the sample was thermally treated with a steam atmosphere. Near-infrared (NIR) spectra, chemical composition, oven-dried density, equilibrium moisture content, compressive Youngs modulus parallel to the grain, and cellulose crystallinity of artificially degraded hinoki cypresses as an analogue of archaeological objects were systematically measured. Partial least squares (PLS) regression analysis was employed to predict compressive Youngs modulus using NIR spectra and some kinds of wood properties as independent variables. Good prediction models were obtained for both independent variables. The scores and the loading plots derived from PLS analysis were applied to consistently explain the mechanism of hydrothermal degradation. It was suggested that the variation of compressive Youngs modulus with hydrothermal treatment was governed by two main components, that is, depolymerization of polysaccharides and variation of cellulose crystallinity.

Assessment of variations in air-dry wood density using time-of-flight near-infrared spectroscopy

Abstract Non-destructive measurement of wood density using reflectance and transmittance near-infrared spectroscopy (NIRS) has already been reported by several researchers. However, these methods do not allow an independent determination of the spectral contributions of the absorption and scattering effects. In this study, time-of-flight NIRS (TOF-NIRS) was used to measure wood density of seven softwood and hardwood species. A curve fitting procedure was used to resolve the diffusion equation and compute the absorption (µa) and reduced scattering coefficients () from the time-resolved profiles (TRPs) acquired from the wood samples. Statistical parameters were also computed from TRPs and correlated with the wood air-dry density as well as with both optical coefficients. A simple linear regression model was built to relate air-dry wood density to µa (R2 = 0.56, root mean square error [RMSE] = 0.047 g/cm3, p value < 0.05). Results obtained were in good agreement with the modified Beer–Lambert law for turbid media. The square root of the / ratio (which was well correlated with the photons mean path length) was used to correct for the distortion due to scattering in absorbance NIR spectra acquired using reflectance spectroscopy. This research demonstrates the potential of TOF-NIRS to assess wood density and to correct reflectance spectra for scattering effects.

Fast online NIR technique to predict MOE and moisture content of sawn lumber

Abstract A fast online grading apparatus for sawn lumber based on near-infrared (NIR) spectroscopy has been developed. The method is based on a novel wavelength dispersive NIR spectrophotometer equipped with a diffraction grating linear sensor and high-intensity lighting. It was possible to acquire spectra from the entire surface of Hinoki cypress lumber sections traveling on a conveyor belt at a speed of 120 m min-1. Additionally, predictive models for moisture content (MC) and modulus of elasticity (MOE) under various MC conditions were developed from the NIR spectra with the aid of partial least squares regression (PLSR) analysis. Both the MC and MOE predictive models demonstrated sufficient levels of prediction accuracy for use on high-speed conveyor belts, and the results of various experiments indicate that the developed device could be applied for the online quality certification of sawn lumber in commercial sawmills.

Prediction of oven-dry density of wood by time-domain terahertz spectroscopy

Abstract Wood is relatively transparent to terahertz (THz) radiation with wavelengths in the submillimeter range. This radiation has a high potential for sensing and imaging wood with a good spatial resolution. THz is especially sensitive to moisture content, fiber alignment, and density – all of which are critical in the manufacturing of wood products. In this work, a systematic study was undertaken on 46 very different wood species by means of THz time-domain spectroscopy with density determination in focus. The dielectric response of wood was modeled based on the Maxwell-Garnett effective medium theory. The dielectric function of the cell wall material was found to be extremely consistent over this large number of species with very different properties. This renders possible to determine wood density by THz time-domain spectroscopy. A strong correlation between the measured and predicted densities has been observed for all the samples investigated.

Effects of nitrogen deficiency on the magnetostructural properties of antiperovskite manganese nitrides

Giant negative thermal expansion in antiperovskite manganese nitrides Mn3AN (A = Zn, Ga, etc.) is achieved by substituting Ge for A as a “relaxant” to the sharp volume change associated with the magnetic transition. We have studied the effects of nitrogen deficiency on the broadening of volume change. Although the broadening increases with decreasing nitrogen content for Mn3Cu0.5Ge0.5N1-δ, the sharp volume change is robust against nitrogen deficiency in Ge-free Mn3GaN1-δ. Nitrogen deficiency probably does not broaden the volume change by itself; rather it probably assists the broadening in conjunction with the Ge dopant. The origin of the broadening is discussed in terms of local lattice distortion of the Mn6N octahedra.

Determination of true optical absorption and scattering coefficient of wooden cell wall substance by time-of-flight near infrared spectroscopy.

The true absorption coefficient (μa) and reduced scattering coefficient (μ´s) of the cell wall substance in Douglas fir were determined using time-of-flight near infrared spectroscopy. Samples were saturated with hexane, toluene or quinolone to minimize the multiple reflections of light on the boundary between pore-cell wall substance in wood. μ´s exhibited its minimum value when the wood was saturated with toluene because the refractive index of toluene is close to that of the wood cell wall substance. The optical parameters of the wood cell wall substance calculated were μa = 0.030 mm(-1) and μ´s= 18.4 mm(-1). Monte Carlo simulations using these values were in good agreement with the measured time-resolved transmittance profiles.