Structural features of composite materials made of hydrolyzed birch wood

Structural features and physical and mechanical characteristics of plate composite materials are investigated. The materials are obtained from hydrolyzed birch wood by hot pressing without the addition of binding components. Wood processing is carried out by the method of explosive autohydrolysis without chemical reagents. The influence of pre-moistening of wood on the structure and properties of the composite material is studied. The structural features of the amorphous and crystalline components of the composite material are studied. It was found that the composite material obtained from pre-dried and pre-moistened wood retains the crystalline phase that is present in the original wood. Changes in the structure of wood when obtaining composite materials based on it occur in the amorphous component. Based on the temperature dependences of the dynamic shear modulus and the tangent of the angle of mechanical losses, information on the glass transition temperature of a complex of amorphous components of a composite material is obtained. It was found that the region of transition of lignin and hemicellulose macrochains from a glassy to a highly elastic state in the composite material is shifted towards low temperatures in comparison with the original wood. The offset is more than 70K. It is assumed that structural plasticization is the main cause of the detected effect. Pre-moistening of wood does not affect the position of the temperature transition in the amorphous component of the composite material. The study of the diffusion and sorption of water vapor in the samples of the material shows the presence of large structural inhomogeneities. Diffusion processes obey Fick’s second law and correlate with the density of samples. Data on density, static bending strength, water absorption and swelling characteristics of composite material samples were obtained. It is shown that the use of pre-moistening of wood before barothermal treatment significantly improves the structural uniformity of the resulting material. The value of the dynamic shear modulus at room temperature in comparison with the same indicator for the material obtained on the basis of dry wood increases three times. Mechanical losses are reduced, mechanical strength increases.

EXPRESS: Two-Trace Two-Dimensional Correlation Spectroscopy (2T2D-COS) Study of the Crystallization Behavior of Bioplastics

A pair of ATR IR spectra obtained during the crystallization of bioplastic copolymer poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] or PHBHx from the melt by spontaneous cooling were examined using the two-trace two-dimensional correlation spectroscopy (2T2D-COS) analysis. Unlike conventional difference spectra, 2T2D spectra showed unexpected details for the patterns of spectral intensity changes, clearly revealing the existence of two distinct populations of crystalline contributions, attributed to the well-ordered primary crystals and the less ordered secondary crystals, in addition to the amorphous component. The 2T2D spectrum sorts out highly overlapped bands associated with different constituents of the system, based on the fundamental properties and constraint imposed on a pair of spectra. Hetero-mode asynchronous 2T2D correlation analysis between the congested CH-stretching region and better resolved carbonyl-stretching region further indicates that the increase in the intensities of certain methyl and methylene bands during the crystallization process is mostly associated with the growth of the well-ordered primary crystals of PHBHx instead of the formation of the secondary crystals in the confined inter-lamellar space.

Fourier transform infrared spectroscopy of developing bone mineral: from amorphous precursor to mature crystal

The developing bone mineral is comprised by an amorphous component prior to apatite crystallization.

Surface quality of products with heterogeneous coatings during mechanical processing

It is shown that when machining products from materials with heterogeneous structure, possibilities of management of a condition of a blanket are significantly limited. As an example of management, cutting processing of products from materials with heterogeneous structure – turning of high-strength flame evaporated coverings is considered. Because for an amorphous component of heterogeneous coverings the lack of deformation hardening is peculiar considerable deformation of the cut-off material is observed at their processing and characteristic shaving is formed. Highintensity thermobaric impact on the processed heterogeneous material leads to partial crystallization in a thin blanket with the high content of an amorphous phase. As a result of researches the criterion which quantitatively estimates the statistics, which complexly characterize uniformity of structure of materials and dispersion of their properties, is offered. The criterion allows defining ability of materials to be exposed to cutting without carrying out long experiments.

Modification of physical properties of poly(L-lactic acid) by addition of methyl-β-cyclodextrin

Poly(L-lactic acid) (PLLA) is a biodegradable plastic and one of the most famous plastics made from biobased materials. However, its physical strength is insufficient compared to general-purpose plastics. In this study, the effect of methylcyclodextrin (MeCD) addition on the structure and physical properties, especially the drawing behavior, of PLLA was investigated. Through thermal analysis, it was found that MeCD addition lowers the crystallinity and enhances the mobility of PLLA. The sample containing approximately 17% MeCD was drawn to more than 1000% at 60 °C, although PLLA fractured at a strain of less than 100%. Differential scanning calorimetry (DSC)-Raman in situ measurements also revealed decreases in the glass transition temperature (T g), cold crystallization temperature (T c), and melting point (T m), and improvement in structural distribution with temperature. DSC-Raman measurements simultaneously supplied information about crystallinity and thermal properties. Thus, it was concluded that MeCD had high affinity for PLLA, and the addition of MeCD increased the amorphous component of PLLA and enhanced the drawability.

The First X-ray Powder Diffraction Measurements on Mars

The CheMin instrument on the Curiosity rover measures XRD and XRF data using Co radiation in transmission geometry. It has analyzed <150 μm portions of eolian soil (Rocknest) and two drill-hole powders (John Klein and Cumberland) from a mudstone [1, 2, Figure 1]. XRD data for Rocknest soil revealed plagioclase, forsteritic olivine, augite, and pigeonite. John Klein and Cumberland are similar, with much less Fe-forsterite and more magnetite than Rocknest. Data were analyzed via Rietveld methods (Topas), and profiles were modeled using beryl-quartz data measured on Mars. CheMin's broad profiles limited analysis of minor phases (<3 wt. %), although the presence of minor phases was evaluated individually for every sample by including each in the Rietveld model and evaluating their effect on the fit. We found no evidence for any perchlorate, carbonate, or sulfate mineral (apart from anhydrite, and bassanite in the mudstones). No phyllosilicate was detected in the soil, but mudstone samples contained two different phyllosilicates, likely trioctahedral smectites. The John Klein XRD pattern had a broad ~10Å peak, whereas Cumberland showed broad peaks at ~13.2Å and ~10Å. The background in all XRD patterns suggested the presence of amorphous/poorly ordered components, which were analyzed using FULLPAT, giving ~27% amorphous content in Rocknest and ~20% in the mudstones. This mineralogy is very similar to that found in soils on the flanks of Mauna Kea volcano, Hawaii. Mineralogy differences between the Rocknest material and the mudstones may be explained by alteration of Fe-forsterite to smectite + magnetite. Combining these results with compositional estimates from unit-cell parameters and bulk chemistry will allow determinations of individual phase compositions, including that of the amorphous component(s). The exact nature of the amorphous component is unclear, but other data show that it is hydrous.

Application of immune and genetic algorithms to the identification of a polymer based on its X-ray diffraction curve

This paper describes how a combination of two methods of artificial intelligence, an immune algorithm and a genetic algorithm, can be used to recognize a polymer by the shape of its X-ray diffraction curve. To this end, the hybrid algorithm uses a database which contains theoretical functions describing wide-angle X-ray diffraction curves of different polymers. These curves are compared by the algorithm with the experimental diffraction curve and the most similar are chosen. Such theoretical curves are kept in the immunological memory, and their parameters can be set as the starting ones in the optimization methods used for decomposition of the experimental curve into crystalline peaks and amorphous component. Using this algorithm, the preparation of the starting parameters is much easier and faster. Decomposition is the most important step in polymer crystallinity determination.