Engineered eco-friendly composite membranes with superhydrophobic/hydrophilic dual-layer for DCMD system.

Considerable advancements have been made in the development of hydrophobic membranes for membrane distillation (MD). Nonetheless, the environmentally responsible disposal of these membranes poses a critical concern due to their synthetic composition. Herein, an eco-friendly dual-layered biopolymer-based membrane was fabricated for water desalination. The membrane was electrospun from two bio-polymeric layers. The top hydrophobic layer comprises polycaprolactone (PCL) and the bottom hydrophilic layer from cellulose acetate (CA). Additionally, silica nanoparticles (SiO2 NPs) were electrosprayed onto the top layer of the dual-layered PCL/CA membrane to enhance the hydrophobicity. The desalination performance of the modified PCL-SiO2/CA membrane was compared with the unmodified PCL/CA membrane using a direct contact membrane distillation (DCMD) unit. Results revealed that silica remarkably improves membrane hydrophobicity. The modified PCL-SiO2/CA membrane demonstrated a significant increase in water contact angle of 152.4° compared to 119° for the unmodified membrane. In addition, PCL-SiO2/CA membrane has a smaller average pore size of 0.23 ± 0.16 µm and an exceptional liquid entry pressure of water (LEPw), which is 3.8 times higher than that of PCL/CA membrane. Moreover, PCL-SiO2/CA membrane achieved a durable permeate flux of 15.6 kg/m2.h, while PCL/CA membrane showed unstable permeate flux decreasing approximately from 25 to 12 kg/m2.h over the DCMD test time. Furthermore, the modified PCL-SiO2/CA membrane achieved a high salt rejection value of 99.97% compared to a low value of 86.2% for the PCL/CA membrane after 24 h continuous DCMD operation. In conclusion, the proposed modified PCL-SiO2/CA dual-layer biopolymeric-based membrane has considerable potential to be used as an environmentally friendly membrane for the MD process.

Electrospraying of Bio-Based Chitosan Microcapsules Using Novel Mixed Cross-Linker: Experimental and Response Surface Methodology Optimization.

Chitosan microcapsules draw attention due to their biodegradability, biocompatibility, antibacterial behavior, low cost, easy processing, and the capability to be used for different applications. This study utilized the electrospraying technique for the chitosan microcapsules formulation. As a novel cross-linking agent, a mixture of oxalic acid and sodium phosphate dibasic was utilized as a collecting solution for the first time in the electrospraying of chitosan microcapsules. Scanning Electron Microscopy (SEM) was utilized to optimize the spherical morphology and size of the experimentally obtained microcapsules. The different parameters, including chitosan concentration, applied voltage, flow rate, and tip-to-collector (TTC) distance, affecting the microcapsules' size, sphericity, yield, and combined effects were optimized using Surface Responses Methodology (RSM). The Analysis of Variance (ANOVA) was utilized to obtain the impact of each parameter on the process responses. Accordingly, the results illustrated the significant impact of the voltage parameter, with the highest F-values and least p-values, on the capsule size, sphericity, and yield. The predicted optimum conditions were determined as 5 wt% chitosan concentration, 7 mL/h flow rate, 22 kV, and 8 cm TTC distance. The predicted responses at the optimized conditions are 389 µm, 0.72, and 80.6% for the capsule size, sphericity, and yield, respectively. While the validation of the model prediction was conducted experimentally, the obtained results were 369.2 ± 23.5 µm, 0.75 ± 0.04, and 87.3 ± 11.4%, respectively. The optimization process was successfully examined for the chitosan microcapsules manufacturing.

Correlated Electrical Conductivities to Chemical Configurations of Nitrogenated Nanocrystalline Diamond Films.

Diamond is one of the fascinating films appropriate for optoelectronic applications due to its wide bandgap (5.45 eV), high thermal conductivity (3320 W m-1·K-1), and strong chemical stability. In this report, we synthesized a type of diamond film called nanocrystalline diamond (NCD) by employing a physical vapor deposition method. The synthesis process was performed in different ratios of nitrogen and hydrogen mixed gas atmospheres to form nitrogen-doped (n-type) NCD films. A high-resolution scanning electron microscope confirmed the nature of the deposited films to contain diamond nanograins embedded into the amorphous carbon matrix. Sensitive spectroscopic investigations, including X-ray photoemission (XPS) and near-edge X-ray absorption fine structure (NEXAFS), were performed using a synchrotron beam. XPS spectra indicated that the nitrogen content in the film increased with the inflow ratio of nitrogen and hydrogen gas (IN/H). NEXAFS spectra revealed that the σ*C-C peak weakened, accompanied by a π*C=N peak strengthened with nitrogen doping. This structural modification after nitrogen doping was found to generate unpaired electrons with the formation of C-N and C=N bonding in grain boundaries (GBs). The measured electrical conductivity increased with nitrogen content, which confirms the suggestion of structural investigations that nitrogen-doping generated free electrons at the GBs of the NCD films.

Monothetic Analysis and Response Surface Methodology Optimization of Calcium Alginate Microcapsules Characteristics.

Owing to bio-polymer's low-cost, environmental friendliness and mechanically stable nature, calcium alginate microcapsules have attracted much interest for their applications in numerous fields. Among the common production methods, the Electrospraying technique has shown a great potential due to smaller shape capsule production and ease of control of independent affecting parameters. Although one factor at a time (OFAT) can predict the trends of parameter effect on size and sphericity, it is inefficient in explaining the complex parameter interaction of the electrospray process. In the current study, the effects of the main parameters affecting on size and sphericity of the microcapsules using OFAT were optimized to attain calcium alginate microcapsules with an average diameter below 100 µm. Furthermore, we propose a statistical model employing the Surface Responses Methodology (RSM) and Central Composite Design (CDD) to generate a quadratic order linear regression model for the microcapsule diameter and sphericity coefficient. Experimentally, microcapsules with a size of 92.586 µm and sphericity coefficient of 0.771 were predicted and obtained from an alginate concentration of 2.013 w/v, with a flowrate of 0.560 mL/h, a needle size of 27 G and a 2.024 w/v calcium chloride concentration as optimum parameters. The optimization processes were successfully aligned towards formation of the spherical microcapsules with smaller average diameter of less than 100 µm, owing to the applied high voltage that reached up to 21 kV.

Laser-Induced Phosphorus-Doped Conductive Layer Formation on Single-Crystal Diamond Surfaces.

A laser-induced doping method was employed to incorporate phosphorus into an insulating monocrystalline diamond at ambient temperature and pressure conditions. Pulsed laser beams with nanosecond duration (20 ns) were irradiated on the diamond substrate immersed in a phosphoric acid liquid, in turns, and a thin conductive layer was formed on its surface. Phosphorus incorporation in the depth range of 40-50 nm below the irradiated surface was confirmed by secondary ion mass spectroscopy (SIMS). Electrically, the irradiated areas exhibited ohmic contacts even with tungsten prober heads at room temperature, where the electrical resistivity of irradiated areas was greatly decreased compared to the original surface. The temperature dependence of the electrical conductivity implies that the surface layer is semiconducting with activation energies ranging between 0.2 eV and 54 meV depending on irradiation conditions. Since after laser treatment no carbon or graphitic phases other than diamond is found (the D and G Raman peaks are barely observed), the incorporation of phosphorus is the main origin of the enhanced conductivity. It was demonstrated that the proposed technique is applicable to diamond as a new ex situ doping method for introducing impurities into a solid in a precise and well-controlled manner, especially with electronic technology targeting of smaller devices and shallower junctions.

Diode Parameters and Equivalent Electrical Circuit Model of n-Type Silicon/B-Doped p-Type Ultrananocrystalline Diamond Heterojunctions Manufactured Through Coaxial Arc Plasma Deposition.

Coaxial arc plasma deposition (CAPD) was employed to manufacture n-type silicon/boron-doped p-type ultrananocrystalline diamond heterojunctions. Measurement and analysis of their dark current density-voltage curve were carried out at room temperature in order to calculate the requisite junction parameters using the Cheung and Norde approaches. For the calculation based on the Cheung approach, the series resistance (Rs), ideality factor (n) and barrier height (Φb) were 4.58 kΩ, 2.82 and 0.75 eV, respectively. The values of Rs and Φb were in agreement with those calculated using the Norde approach. Their characteristics for alternative current impedance at different frequency values were measured and analyzed as a function of the voltage (V) values ranging from 0 V to 0.5 V. Appearance of the real (Z') and imaginary (Z″) characteristics for all V values presented single semicircles. The centers of the semicircular curves were below the Z' axis and the diameter of the semicircles decreased with increments of the V value. The proper equivalent electrical circuit model for the manufactured heterojunction behavior was comprised of Rs combined with the parallel circuit of resistance and constant phase element.

Diode Parameters of Heterojunctions Comprising p-Type Ultrananocrystalline Diamond Films and n-Type Si Substrates.

In the current research, heterojunctions comprising p-type ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films and n-type Si substrates were formed via pulsed laser deposition. To extract their junction parameters via thermionic emission (TE) theory and Norde model, the measurement of dark current density-voltage curves was carried out under various temperatures ranging from 300 to 60 K. Through TE theory, the ideality factor values at 300 K and 60 K were 2.70 and 8.66, respectively. This justified that a heavy recombination process occurs at the junction interface in addition to another tunneling process at 300 K. The tunneling process is predominant at low temperatures. The barrier height values were 0.78 eV and 0.18 eV at 300 K and 60 K, respectively. The values for series resistance (Rs) calculated via Norde model at 300 K and 60 K were 275.24 Ω and 78.66 kΩ, respectively. The increment of Rs at low temperatures was likely due to the decrease of carrier concentration in the B-doped UNCD/a-C:H films when temperature was decreased.