Hierarchical porous carbon materials made from cork were fabricated using a facile and green method combined with air activation, without any templates and chemical agents. The influence of air activation on the texture and other surface characteristics of the carbon materials were evaluated by various characterization techniques. Results indicate that air oxidation can effectively improve the surface area and the hierarchical porous structure of carbon materials, as well as increase the number of oxygen-containing functional groups on the carbon surface. The specific surface area and the pore volume of the carbon material activated by air at 450 °C (C800-M450) can reach 580 m²/g and 0.379 cm³/g, respectively. These values are considerably higher than those for the non-activated material (C800, 376 m²/g, 0.201 cm³/g). The contents of the functional groups (C–O, C=O and O–H) increased with rising activation temperature. After air activation, the adsorption capacity of the carbon materials for methylene blue (MB) and methyl orange (MO) was increased from 7.7 and 6.4 mg/g for C800 to 312.5 and 97.1 mg/g for C800-M450, respectively. The excellent dye removal of the materials suggests that the porous carbon obtained from biomass can be potentially used for wastewater treatment.

Thermal modification or heat treatment can cause the loss of mechanical property of wood. In this study, Poplar (Populus tomentosa Carr.) and spruce (Picea obies Mast.) were heat treated at 180, 200, and 220 °C for 2–10 h. Changes of color (L*, a* and b*) and mechanical strength including modulus of elasticity (MOE), modulus of rupture (MOR) and shear strength after heat treatment were analyzed. Time-temperature superposition methods were used to quantify color and mechanical strength. The prediction models of MOR, MOE and shear strength were assessed with support vector regression model (SVR) based on color parameters. The trends of color change and mechanical strength after heat treatment were highly consistent. The values of apparent activation energy (E _a ) calculated from color parameters (110.6–187.2 kJ/mol) were identical to those from mechanical strengths (103.2–219.2 kJ/mol). Color parameters were used as input variables, and the MOE, MOR, and shear strength were output parameters in the established SVR model. Gaussian radial basis function (RBF) was found to be a kernel function for SRV model. Optimal hyperparameters in SVR model were obtained using cross-validation and grid search. The determination coefficients for MOE, MOR, and shear strength were 0.903, 0.835, and 0.865, respectively for poplar. The high correlation suggested that wood mechanical strength can be predicted non-destructively through measuring color parameters after heat treatment.

Bamboo shoot is renewable biomass rich in carbon and nitrogen. To take advantage of its sources of carbon and nitrogen, hierarchical porous nitrogen-doped carbon materials derived from bamboo shoot were acquired via a one-step method in this study. The obtained carbons were characterized by using XRD, Raman, N₂ sorption, SEM, TEM, XPS, etc. The carbon calcinated at 700 °C with KHCO₃ treatment (BSC) displays a large surface area (1475.5 m² g⁻¹) and typically porous structure from micro- to macropores, a self-nitrogen content, and many defects, which could offer transport channels and active sites for lithium ions while used as carbon anode. Based on the above features and the synergistic effects among them, BSC exhibits the typical electrochemical performance of a carbon-based anode material, with a specific capacity as high as 611.3 mA h g⁻¹ (a Coulombic efficiency of 98.7%) after 100 cycles at a current density of 0.1 A g⁻¹. Meanwhile, it also has a good rate performance and excellent cycling properties (436.1 mA h g⁻¹ after 300 cycles at 0.1 A g⁻¹) compared with NBSC (carbon directly carbonized at 700 °C). Thus, it is promising for further improvements made to porous carbon derived from biomass and used as anode in the application of energy storage, and could be a guideline for the preparation of high-value-added carbon materials derived from biomass.

The magnitudes of the color changes in heat-treated wood are closely related to the chemical composition of the wood, and changes in the chemical composition are the essential reasons for changes in the mechanical properties of heat-treated wood. The response relationships among the color parameters of heat-treated wood and the chemical composition were constructed to provide a scientific basis for regulating the mechanical properties with the color. The effects and linear correlations of the lightness indicators (L^*) for poplar (Populus tomentosa Carr.) and spruce (Picea asperata Mast.) after heat treatment were related to the chemical compositions of the heat-treated woods by constructing relationships between the L^* values. The relative content of cellulose in the heat-treated poplar downward trend and was significantly positively correlated with the L^* value; however, the correlation with the L^* value for the heat-treated spruce was insignificant. The L^* value of the heat-treated wood was significantly positively correlated with the relative contents of hemicellulose, and was significantly negatively correlated with lignin. The L^* value of the heat-treated wood had a superior response relationship with the crystallite sizes. Therefore, the constructed response relationship provides a theoretical basis for accurate and nondestructive testing of the mechanical properties of heat-treated wood by using the color parameters as rapid detection indicators.

Effects of different boiling treatments were evaluated relative to various physical properties of cork from Quercus variabilis before and after treatment, including volume, density, hardness, compression resilience ratio, and color. The boiling water treatment decreased the density, hardness, and lightness of cork. Water absorption amount of cork boiled at 100 °C for 30 min to180 min increased from 28.85% to 52.50%, and expansion in the radial direction was 15.4% to 19.5%. The total color difference (ΔE*) of cork gradually increased with increased boiling time. The values of the compression resilience ratio of all corks after a pressure release at 24 h were >80%. Cork samples boiled at 100 °C for 60 min, and then dried under different temperatures (140 °C to 240 °C), had volume expansion between 35.6% and 65.3%. With increased drying temperature, the ΔE* of cork increased. Cork boiled at 100 °C for 60 min followed by microwave irradiation of different times (2 min to 8 min) had volume expansion of 39.7% to 54.5%. Microwave treatment had little influence on cork color. The sodium hydroxide solution boiling treatment decreased cork lightness, while the hydrogen peroxide-treated cork lightness increased with the increasing of solution concentration, and ΔE* slightly increased.