Yukie Saito

Analysis of Functional Group Sited on Multi-Wall Carbon Nanotube Surface

Functionalization of Carbon Nanotube (CNT) plays an important role in creating CNT hybride material. In this study, integrated analysis of functional group sites on the pristine and modified Multi-Wall Carbon Nanotube (MWCNT) surface was comparably conducted to know the effect of acid solution on the surface after purification and functionalization process. Acid treatment removed rest of graphitic and residual catalytic metal particles and suffered degradation, such as nanotube shortening and additional defect generation in the graphitic network. Defects on the side wall due to functionalized group clearly shown in Transmission Electron Image (TEM) images cause a reduction in thermal stability. Functional group sited on the side wall was detected by Attenuated Total Reflectance (ATR) - Fourier Transform Infra Red (FTIR) with the relative concentration of oxygen-containing functional groups determined by Boehm titration.

Lateral thermal expansion of chitin crystals

Measurements of the thermal expansion coefficients (TECs) of chitin crystals in the lateral direction are reported. We investigated highly crystalline a chitin from the Paralithodes tendon and an anhydrous form of β chitin from a Lamellibrachia tube from room temperature to 250 °C, using X-ray diffraction at selected temperatures in the heating process. For a chitin, the TECs of the a and b axes were α a = 6.0 × 10 -5 °C -1 and α b = 5.7 × 10 -5 °C -1 , indicating an isotropic thermal expansion in the lateral direction. However, the anhydrous β chitin exhibited an anisotropic thermal expansion in the lateral direction. The TEC of the a axis was constant at α a = 4.0 x 10 -5 °C -1 , but the TEC of the b axis increased linearly from room temperature to 250 °C, with α b = 3.0-14.6 × 10 -5 °C -1 . These differences in the lateral thermal expansion behaviors of the a chitin and the anhydrous β chitin are due to their different intermolecular hydrogen bonding systems.

Structural data on the intra-crystalline swelling of β-chitin

The intra-crystalline swelling of the highly crystalline β-chitin from Tevnia jerichonana was investigated by X-ray crystallography and Fourier transform infrared (FTIR) spectroscopy, using hydrogenated and deuterated hydrochloric acids as swelling agents. Three levels of swelling were identified that could be defined as inter- and intra-sheet swelling. A moderate and reversible swelling in water and methanol gave crystalline β-chitin cystallosolvates, namely dihydrate and methanolate, respectively. In these, an inter-sheet swelling was observed, corresponding to an expansion of only the b parameter of the unit cell of β-chitin. Under these swelling conditions, the use of deuterated reagents had no effect on the amide NH⋯OC hydrogen bonds that hold the structure of β-chitin together, but only induced a partial and reversible deuteration of the chitin hydroxymethyl groups. A more severe swelling — but still reversible — occurred with 6 N HCl or DCl, which converted the crystals of β-chitin into a paracrystalline gel-like product resulting from inter-sheet+intra-sheet swelling. With this acid strength, the deuteration pattern indicated that a fraction of the amide hydrogen bonds was broken and became susceptible to an irreversible deuteration. A very severe and irreversible swelling occurred with 8 N HCl or DCl. In that case, the inter- and intra-sheet swelling was extensive to the point where all memory of the parallel-chain β-chitin was lost. In addition, this swelling was accompanied by a drastic and rapid depolymerization. The treatment with 8 N HCl led invariably to crystalline α-chitin when the samples were neutralized.

Effects of heat treatment on brittleness of Styrax tonkinensis wood

A new approach is proposed for the evaluation of the brittleness of heat-treated Styrax tonkinensis wood. Heat treatment made wood more brittle when wood was heated at a higher temperature or for a longer time. The brittleness increased to four times that of the control when wood was heated at 200°C for 12 h. For treatment at 160°C, the increase in brittleness without any change in weight is thought to be possibly caused by the relocation of lignin molecules. At higher temperatures, loss of amorphous polysaccharides due to degradation is thought to become the main factor affecting brittleness. The crystallites that were newly formed after 2 h of treatment showed brittleness that was different from that of the inherent crystallites remaining after 12 h of heat treatment. This inherent crystalline cellulose possibly plays a role in brittleness. There is also the possibility of using color to predict the brittleness of heat-treated wood.

Non-destructive Measurement of Moisture Distribution in Wood during Drying Using Digital X-ray Microscopy

The objective of this study was to develop a nondestructive method by which moisture distribution in wood during drying could be predicted. A newly developed digital X-ray microscope was used to measure the moisture content of wood and its accuracy and resolution was evaluated compared to the classic oven-dry method. Small green wood specimens of Sugi (Cryptomeria japonica D. Don) were cut and dried under constant temperature and humidity. As the weight was decreasing during drying, X-ray microscope images of cross section were obtained. From these digital images and specimen weight, the moisture content during drying was measured by the two methods. After the shrinkage of the specimen was canceled, the standard error achieved finally was about 1% moisture content within the experimental range. As the image was divided into small subimages, the clear moisture distribution can be seen. It was found that the image divided into 32 × 32 subimages in each size of 0.625 × 0.625 mm might be valid to determine the moisture distribution, and that the drying rate in early wood is larger than in late wood.

Growth of cone-shaped carbon material inside the cell lumen by heat treatment of wood charcoal

ConclusionsWith treatment at 2500°C, wood cell walls partially transform into a turbostratic carbon structure, which has an X-ray diffraction peak corresponding to a layer plane spacing of 0.343 nm. Despite this change, there was no apparent change within the cell wall seen by SEM.Cone-shaped carbon material was formed inside the cell lumen after treatment at 2500°C. This is not a feature originating from any wood cell organism and seems to result from vaporized carbon or pyrolysis gases that originate within the cell wall.

Structural discrimination of double-walled carbon nanotubes by chiral diporphyrin nanocalipers

In this contribution, we demonstrate the separation of double-walled carbon nanotubes (DWNTs) by host–guest methodology. New chiral diporphyrin nanocalipers with a longer spacer (∼1.9 nm) consisting of carbazole–pyrene–carbazole are rationally designed as a host on the basis of the previous chiral diporphyrin nanocalipers with carbazole–anthracene–carbazole spacer (∼1.4 nm). The chiral nanocalipers are found to recognize the diameter of DWNTs to make diameter distribution much narrower. In addition, the extracted carbon nanotubes (CNTs) exhibited circular dichroism (CD) after removal of the chiral nanocalipers and dissolution in water in the presence of achiral surfactant.

Cone structure of hexagonal carbon sheets stacked in wood cell lumen

Cone-shaped carbon particles were produced inside the cell lumen of sugi (Japanese cedar) charcoal treated at 2500°C. We succeeded in clarifying the structural and morphological features by separating the cone-shaped carbon from the carbonized cell wall by heating to 800°C in air. Cone-shaped carbon is less susceptible to oxidation than the carbonized cell wall. The isolated cone-shaped carbon and carbonized cell wall fracture were observed separately by transmission electron microscopy and selected area electron diffraction. Results revealed that the cone-shaped carbon has a very highly ordered cone structure with regularly stacked hexagonal carbon sheets, whereas the carbonized cell wall has a disordered structure of mosaic-like turbostratic carbon.

Acetylation and stepwise solvent-exchange to modify hydrophilic cellulose whiskers to polychloroprene-compatible nanofiller

The acetylation of cellulose nanofiber (CNF) introduced hydrophobicity to the surface making it compatible with non-polar matrix, and also making it an effective nanofiller for polychloroprene (PCR) composite. The CNF was extracted from oil palm empty fruit bunches. Previously, CNF was dispersed in water, and this water was subsequently substituted with N,N-dimethylacetamide, in which CNF was acetylated by acetic anhydride with a pyridine catalyst. IR spectroscopy revealed that the acetylation extent was controllable by the reaction time. After the reaction, the DMAc was replaced by dichloromethane, and finally mixed with PCR. The CNF–PCR mixture was cast and composite film was formed at room temperature. Structural analysis and mechanical tests indicated that acetylation treatment made CNF compatible with PCR, and that nano-dispersed CNF raised the mechanical strength of the PCR–CNF nanocomposite.

The suitable harvesting season and the part of moso bamboo (Phyllostachys pubescens) for producing binderless boards

The properties of the binderless boards of moso bamboo depending on the harvest seasons and the parts of the height were reported and the optimum harvesting conditions investigated. The binderless boards were prepared from the powdered bamboo harvested each month from June to May, and the parts in height. The hot water extract (HWE), lignin, α-cellulose, and hemicelluloses contents were examined. The board properties were evaluated with internal bonding (IB), water absorption (WA), and thickness swelling (TS). From the experiment, the boards prepared between March and October had higher HWE content and higher IB and lower WA and TS than the ones prepared in other months. The board from the top part showed lower IB and higher WA and TS than the bottom and the middle. The boards prepared from the residue after extraction of HWE showed lower IB than the unextracted samples. These results indicated that for producing board from bamboo, the suitable harvesting season is when HWE contents are higher and that the suitable parts in height for harvesting are the bottom and the middle where lignin contents are not low.