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Oriented strandboards were constructed from various combinations of mixed hardwood flakes. Fractal dimension of void size (FDVS) in the manufactured samples was studied by means of X-ray computer tomography images and a computer image processing technique. The FDVS value was high in the panel surface layers and decreased toward the panel center, and the FDVS decrement was linear to increased porosity. At the same overall porosity level, the FDVS varied as function of void distribution. FDVS could be a useful additional parameter for characterizing the internal void structure of strand-based wood composites. [ABSTRACT FROM AUTHOR]

A simple and effective mixing carbonization-activation process was developed to prepare rice hull-derived porous Si–carbon materials. The morphologies and pore structures of the materials were controlled effectively without any loading or additions at various carbonization temperatures. The structures of the samples changed from large pores and thick walls after 800 °C carbonization to small pores and thin walls after 1000 °C carbonization. An additional alkali activation–carbonization process led to coral reef-like structures surrounded by squama in the sample that underwent 900 °C carbonization (Act-RH-900). This optimal material (Act-RH-900) had a large specific surface area (768 m2 g−1), relatively stable specific capacitance (150.8 F g−1), high energy density (31.9 Wh kg−1), and high-power density (309.2 w kg−1) at a current density of 0.5 A g−1 in 1 M KOH electrolyte, as well as a good rate performance and high stability (capacitance retention > 87.88% after 5000 cycles). The results indicated that Act-RH-900 is a promising candidate for capacitive applications. This work overcomes the restrictions imposed by the complex internal structure of biomass, implements a simple reaction environment, and broadens the potential applicability of biomass waste in the field of supercapacitors. [ABSTRACT FROM AUTHOR]

Constructing biomass hierarchical porous carbon composite electrodes with ultra-high specific surface area, reasonable distribution of pores, and fast redox atoms for super-capacitors (SCs), is still a constant pursuit goal of current researchers. Herein, biochar containing heteroatoms with micro-meso-macro porous were successfully prepared from soybean straw as the precursor. Remarkably, an exclusive synthesis strategy, via hydrothermal reaction, alkali activation, and acid etching dual chemical treatments at specific carbonization temperature, was applied for controlling pore structure in this work, affording three dimensions (3D) hierarchical porous and a certain disordered graphitized structure of carbon material: SSP-900. SSP-900 exhibits the property of ultra-high specific surface area and reasonable distribution (S BET =1283 m2 g−1, S micro /S BET = 65%, Pore Volume= 0.73 cm3 g−1). Furthermore, it also displays the key merits of electrode materials candidate for SCs, including the superb specific capacity of 357 F g−1 at 0.5 A g−1 in the three-electrode system. Additionally, single electrode of SSP-900//SSP-900 demonstrates a splendid specific capacitance of 320 F g−1 in current density of 0.15 A g−1, the high energy density (11.2 Wh kg−1) and power density (37.8 W kg−1), a great rate capability retention (42%), and outstanding cycling stability up to 10,000 times (only 10% loss of capacitance) in two-electrode system. Its splendid electrochemical performances originate from the synergistic contribution of the special pore structure and built-in redox atom (N and O). As such SSP-900 may be seen as a promising SCs electrode material. This research provides an effective method for controlling the pore structure of biochar to be of great application in the SCs field. • Soybean straw waste is used to prepare 3-D hierarchical porous carbon electrode material. • Carbon materials show micro-meso-macroporous and disordered graphitized structure. • Its performance has been improved by combined alkali activation with acid etching. [ABSTRACT FROM AUTHOR]