研究不同厚度中密度纤维板(medium density fiberboard,MDF)的孔隙分形特征,结合高压压汞试验(mercury intrusion porosimetry,MIP)和N_(2)吸附试验,量化材料孔体积、孔径尺寸和孔径分布等孔隙结构参数。利用FHH(Frenkel-Halsy-Hill)和...研究不同厚度中密度纤维板(medium density fiberboard,MDF)的孔隙分形特征,结合高压压汞试验(mercury intrusion porosimetry,MIP)和N_(2)吸附试验,量化材料孔体积、孔径尺寸和孔径分布等孔隙结构参数。利用FHH(Frenkel-Halsy-Hill)和MIP分形理论模型结合试验结果,计算出不同尺度孔隙下的分形维数,采用分形模型量化孔隙结构的复杂性,揭示不同厚度MDF孔隙分形特征的显著差异。通过分形模型计算得到的分形维数表明,宏观孔分形维数(2.957~2.988)与介观孔分形维数(2.602~2.851)均随厚度增加显著升高(R^(2)>0.90),表明厚板孔隙结构复杂度更高;密度(0.722~0.777 g/cm^(3))对分形维数的影响较弱。此外,分形维数与孔隙结构参数之间存在密切联系,宏观孔分形维数与材料平均孔径、孔隙率呈正相关,介孔分形维数与平均孔径呈负相关,与比表面积呈正相关。研究结果揭示厚度主导的孔隙分形规律,为通过工艺优化调控MDF环保性能提供理论依据。展开更多
This study systematically investigated the microstructure,mechanical properties,and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging(MDF)at 100℃.The mean grain size was remarkab...This study systematically investigated the microstructure,mechanical properties,and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging(MDF)at 100℃.The mean grain size was remarkably decreased from 17.2±0.5µm to 1.9±0.3µm,and 84.4%of the microstructure was occupied by grains of below 1µm in size after applying three MDF passes.Electron backscattered difraction examinations revealed that continuous dynamic recrystallization,progressive lattice rotation,and particle-stimulated nucleation mechanisms were recognized as contributing to microstructural evolution.Furthermore,transmission electron microscopy results showed that nanoparticles of Mg/Zn dynamically formed under high strain MDF,while the initial extrusion fber texture was altered to be<0001>parallel to the fnal forging axis.A synergistic efect of grain refnement,texture evolution,second-phase precipitates,and dislocation strengthening resulted in an increased ultimate tensile strength of 232±5 MPa after three MDF passes.However,this was accompanied by a reduction in the elongation(8±2.1%).Additionally,a high corrosion rate of 0.59 mm/year was measured for the experimental alloy fabricated by 3 MDF passes.In agreement with the latter,electrochemical impedance spectroscopy results indicated that the grain refnement improved the passivation kinetics of the oxide layer.展开更多
The utilization of oil palm biomass in the production of high-value products has increased substantially.Due to the presence of sugars and starches in their tissues,oil palms have an exceptionally low natural resistan...The utilization of oil palm biomass in the production of high-value products has increased substantially.Due to the presence of sugars and starches in their tissues,oil palms have an exceptionally low natural resistance to fungi,making them susceptible to contamination.In this study,the properties of particleboard made from oil palmfibers,namely empty fruit bunches(EFB),oil palm trunks(OPT),and oil palm fronds(OPF)fibers and its poten-tial for fungal attack were evaluated.The chemical composition,spectroscopic characterization,morphological features,and elemental analysis of oil palm biomassfibers were identified and thoroughly examined.The mechan-ical properties and dimensional stability of the boards were assessed based on Japanese Industrial Standards(JIS)and American National Standards Institute(ANSI)guidelines.The density,strength,and moisture resistance of particleboard made from OPTfibers may vary from those made from OPF and EFB due to inherent changes in chemical composition andfiber structure.These differences have an impact on the overall performance of the particleboard.Based on the ANOVA and Tukey’s test results,significant differences in elasticity properties were observed mainly between OPT and otherfibers,while bending strength revealed notable differences between various pairs of particleboards.The evaluation also highlighted variations in dimensional stability and water absorption capabilities.However,bending strength properties did not demonstrate any significant deviations.For the fungi test,fungal activity on the boards was observed over a two-week period in a controlled environment.The study revealed that oil palm-based particleboard exhibited susceptibility to fungal attacks,particularly from Aspergillus sp.,Trichoderma sp.,and Paecilomyces variotii.Thesefindings highlight the necessity for additional treatments to control or prevent fungal growth,thereby enhancing the commercial value of the particleboards.展开更多
文摘This study systematically investigated the microstructure,mechanical properties,and corrosion behavior of an extruded Zn-0.2Mg alloy processed by multi-directional forging(MDF)at 100℃.The mean grain size was remarkably decreased from 17.2±0.5µm to 1.9±0.3µm,and 84.4%of the microstructure was occupied by grains of below 1µm in size after applying three MDF passes.Electron backscattered difraction examinations revealed that continuous dynamic recrystallization,progressive lattice rotation,and particle-stimulated nucleation mechanisms were recognized as contributing to microstructural evolution.Furthermore,transmission electron microscopy results showed that nanoparticles of Mg/Zn dynamically formed under high strain MDF,while the initial extrusion fber texture was altered to be<0001>parallel to the fnal forging axis.A synergistic efect of grain refnement,texture evolution,second-phase precipitates,and dislocation strengthening resulted in an increased ultimate tensile strength of 232±5 MPa after three MDF passes.However,this was accompanied by a reduction in the elongation(8±2.1%).Additionally,a high corrosion rate of 0.59 mm/year was measured for the experimental alloy fabricated by 3 MDF passes.In agreement with the latter,electrochemical impedance spectroscopy results indicated that the grain refnement improved the passivation kinetics of the oxide layer.
文摘The utilization of oil palm biomass in the production of high-value products has increased substantially.Due to the presence of sugars and starches in their tissues,oil palms have an exceptionally low natural resistance to fungi,making them susceptible to contamination.In this study,the properties of particleboard made from oil palmfibers,namely empty fruit bunches(EFB),oil palm trunks(OPT),and oil palm fronds(OPF)fibers and its poten-tial for fungal attack were evaluated.The chemical composition,spectroscopic characterization,morphological features,and elemental analysis of oil palm biomassfibers were identified and thoroughly examined.The mechan-ical properties and dimensional stability of the boards were assessed based on Japanese Industrial Standards(JIS)and American National Standards Institute(ANSI)guidelines.The density,strength,and moisture resistance of particleboard made from OPTfibers may vary from those made from OPF and EFB due to inherent changes in chemical composition andfiber structure.These differences have an impact on the overall performance of the particleboard.Based on the ANOVA and Tukey’s test results,significant differences in elasticity properties were observed mainly between OPT and otherfibers,while bending strength revealed notable differences between various pairs of particleboards.The evaluation also highlighted variations in dimensional stability and water absorption capabilities.However,bending strength properties did not demonstrate any significant deviations.For the fungi test,fungal activity on the boards was observed over a two-week period in a controlled environment.The study revealed that oil palm-based particleboard exhibited susceptibility to fungal attacks,particularly from Aspergillus sp.,Trichoderma sp.,and Paecilomyces variotii.Thesefindings highlight the necessity for additional treatments to control or prevent fungal growth,thereby enhancing the commercial value of the particleboards.
