Sohrab Rahimi

Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Wood Science and Technology

Committee Chair

Kaushlendra Singh

Committee Co-Chair

David DeVallance

Committee Member

Jingxin Wang


Non-chemical treatments (steam and ultrasonic vibrations) have been intensively researched and commercialized to make chemical-free wood products with enhanced mechanical properties and decay resistance; however, utilization of high-pressure steam medium involves vapor-phase reactions using high-temperature steam generated at the expense of high energy input. In this research, drying behavior, mechanical properties, and physical characteristics of wood (yellow-poplar) were compared to evaluate influence of reaction media (steam and hot-compressed water) and temperatures (100°C and 140°C). The control (no treatment) was used for reference comparison. For experiments, green samples of yellow-poplar heartwood were used for treatment. The average size of length (longitudinal direction), width (radial direction), and thickness (tangential direction) of the specimens were 22.53, 17.18, and 16.72 mm, respectively. After the treatment, the samples were dried under isothermal temperature condition of 105°C under nitrogen atmosphere to minimize the influence of humidity. Data from drying experiments were used to prepare drying curves, which were fitted with unsteady state molecular transport equation to calculate overall liquid diffusion coefficients. Dimensions, weight, and true volume (excluding pores) of samples were measured for green, treated, and dried samples and this data was used to calculate selected physical characteristics (moisture content, volumetric shrinkage, specific gravity, and total porosity). The dried samples were evaluated for water absorption, volumetric swelling, modulus of elasticity, and compression strength. Statistical analysis of experimental data showed that the reaction media had significantly influenced moisture content, total porosity, diffusion coefficient, and compression strength. Intensified hot-compressed water treated and control samples had the most and least moisture contents (101.10% and 43.56%), respectively. In addition, wet and oven-dry specific gravity of the samples were in range of 0.42 to 0.44 and 0.49 to 0.50, respectively. Additionally, Intensified steam treated and control samples had the most and least total porosity (94.94% and 82.36%), respectively. Furthermore, mild hot-compressed water treated samples showed the greatest compression strength (47.75 MPa). Overall liquid diffusion coefficient of the untreated yellow-poplar was 3.15 x 10-8 m 2/s. Except steam treatment at 140°C, other treatments significantly decreased diffusion coefficient.