The adsorption of dissolved organic matter (DOM) to metal (oxy)hydroxide mineral surfaces is a critical step for C sequestration in soils. Although equilibrium studies have described some of the factors controlling this process, the molecular-scale description of the adsorption process has been more limited. Chemical force spectroscopy revealed differing adhesion strengths of DOM extracted from three soils and a reference peat soil material to an iron (oxy)hydroxide mineral surface. The DOM was characterized using ultrahigh-resolution negative ion mode electrospray ionization Fourier Transform ion cyclotron resonance mass spectrometry. The results indicate that carboxyl-rich aromatic and N-containing aliphatic molecules of DOM are correlated with high adhesion forces. Increasing molecular mass was shown to decrease the adhesion force between the mineral surface and the DOM. Kendrick mass defect analysis suggests that mechanisms involving two carboxyl groups result in the most stable bond to the mineral surface. We conceptualize these results using a layer-by-layer "onion" model of organic matter stabilization on soil mineral surfaces.

Wood-based cellulose nanomaterials (CNs) (specifically, cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs)) are environmentally sourced low-impact materials with remarkable thermal, mechanical, and physical properties. This uniqueness makes them great candidates for creating nanocomposite materials with a wide range of attributes. Investigating the morphological, thermal, and nanomechanical properties of CNs becomes crucial to intelligent development of novel composite materials. An atomic force microscope equipped with a nanoindenter was used to investigate the compression modulus of CNFs and CNCs using two analytical approaches (denoted as Oliver Pharr (OP) and Fused Silica (FS)). The CNC modulus values (ECNC-FS = 21.1 GPa, ECNC-OP = 28.7 GPa) were statistically larger than those obtained from CNFs (ECNF-FS = 12.4 GPa, ECNF-OP = 15.1 GPa). Additionally, the FS analytical approach provided statistically significant lower estimates. Thermal stability of CNFs and CNCs was investigated using thermogravimetric analysis. Significant differences were found between CNF and CNC onset temperatures (OnsetCNC = 228.2 °C, OnsetCNF = 279.9 °C), decomposition temperatures (DTGACNC = 247.9 °C, DTGACNF = 331.4 °C), and residues (ResidueCNC = 34.4%, ResidueCNF = 22.8%). This research enriches the information on thermal stability and nanomechanical performance of cellulose nanomaterials, and provides increased knowledge on understanding the effect of CNs as a matrix or reinforce in composites.

No abstract

The objective of this study was to investigate the effects of material type, screw diameter, and screw length on ultimate failure load and stiffness of four-sided furniture cabinets. In total, 81 four-sided test cabinets were constructed in 1/1 dimensions. Assembly of cabinets was done using nine different sizes of screws ranging from 3.5 by 40 mm to 5 by 50 mm. Panel materials were 18-mm-thick particleboard (PB) and 16- and 18-mm-thick medium-density fiberboard (MDF1, MDF2). Cabinets were anchored at two points located underneath the top panel and tested under static load. Loading procedures of the American National Standards Institute/Kitchen Cabinet Manufacturers Association were followed during the static tests. Test results showed that 18- and 16-mm MDF cabinets yielded higher failure loads and stiffness values compared with the 18-mm PB cabinets. Test results also indicated that increasing either screw diameter or screw length tended to have a positive effect on the failure load and stiffness values. The strongest and most rigid four-sided cabinets were obtained with 4-mm-diameter and 50-mm-long screws if the construction panel material was 18-mm-thick MDF, 5-mm-diameter and 45-mm-long screws if the construction panel material was 16-mm-thick MDF, and 5-mm-diameter and 50-mm-long screws if the construction panel material was 18-mm-thick PB.