SESAM mode-locked Tm:LuYO3 ceramic laser generating 54-fs pulses at 2048 nm.

Mode-locked laser operation near 2.05 µm based on a mixed sesquioxide Tm:LuYO3 ceramic is demonstrated. Continuous-wave and wavelength-tunable operation is also investigated. Employing a GaSb-based semiconductor saturable absorber mirror as a saturable absorber, a maximum average output power of 133 mW is obtained for a pulse duration of 59 fs. Pulses as short as 54 fs, i.e., eight optical cycles are generated at a repetition rate of ∼78MHz with an average output power of 51 mW. To the best of our knowledge, this result represents the shortest pulse duration ever achieved from Tm-based solid-state mode-locked lasers.

Direct air capture (DAC) of CO2 using polyethylenimine (PEI) "snow": a scalable strategy.

We have developed a cross-linked polyethyleneimine non-porous material (PEI "snow") for direct air capture (DAC) of CO2. This new hydrogel is green, inexpensive, readily scalable and can be fabricated through simple crosslinking of PEI with triglycidyl trimethylolpropane ether (TTE) in 10 minutes. It demonstrates outstanding DAC performance (overall CO2 uptake efficiency of approximately 50 mg g-1 of sorbent) at lab scale (sorbent weight roughly 60 g, air flow rate 2000 ml min-1) and the CO2 can be desorbed using low-grade waste steam.

Preventing Hydrate Adhesion with Magnetic Slippery Surfaces.

Hydrate formation is a common challenge in the oil and gas industry when natural gas is transported under cold conditions in the presence of water. Coatings are one of the solutions that have shown to be a promising approach to address this challenge. However, this strategy suffers from the intrinsic existence of a solid-liquid interface causing a high rate of hydrate nucleation and high hydrate adhesion strength. This proof-of-concept study highlights the performance of a magnetic slippery surface to prevent hydrate adhesion at atmospheric pressure using tetrahydrofuran hydrates. The coating consisted of a hydrocarbon-based magnetic fluid, which was applied to a metal surface to create an interface that lowered the hydrate adhesion strength on the surface. The performance of these new surfaces under static and dynamic (under fluid flow) conditions shows that the magnetic coating gel can be a potential inhibitor for hydrate adhesion as it reduced the torque value after the formation of hydrates.

Polyethylenimine "Snow": An Emerging Material for Efficient Carbon Removal.

Amine-functionalized solid adsorbents are one of the most promising alternatives to the conventional "amine scrubbing" for carbon capture with a number of prominent examples being reported. However, their widespread application in industry is unfulfilled due to their overall performance and complex fabrication, which relies on a porous support. In this "proof of concept" study, we report an approach for generating a new type of material called polyethylenimine (PEI) 'snow', which can be prepared for use in under 15 min. The material does not require a support, and the resulting CO2 uptake is the highest reported to date for PEI-functionalized materials. This was achieved through a rigorous material program that identified conditions where a material with the requisite properties could be generated. From experimental measurements, the virtual dryness of the PEI snow results in fast CO2 absorption kinetics, which is comparable to conventional solid adsorbents, but its CO2 uptake (451.5 mg CO2/g PEI) is the highest reported so far. Breakthrough curves demonstrate the outstanding CO2 selectivity over N2 and CH4 (above 1000), with the potential for post-combustion capture and natural gas sweeting. This strategy can be applied in affordable and efficient gas treatment for various large point sources.

Rational design and fabrication of an alkali-induced O/W emulsion stabilized with cellulose nanofibrils (CNFs): implication for eco-friendly and economic oil recovery application.

In this work, an alkali-induced oil in water (O/W) emulsion stabilized with cellulose nanofibrils (CNFs) was proposed to advance the development of enhanced oil recovery (EOR) approaches. The reactive species in the crude oil were first determined by FT-ICR MS. Subsequently, direct measurements of emulsion rheology, morphology, drop size distribution, and interfacial tensions (IFTs) were performed. Particular interest was placed on the stability and variation of the average drop diameter of the emulsions to reveal the underlying stabilizing mechanisms. The results showed that the introduction of L-CNFs (containing lignin segment) and CNFs could significantly prohibit the coalescence of drops and thus improve the stability of the emulsions. L-CNFs and CNFs were irreversibly absorbed at the oil-water interface forming a solid "armor" on the drops with 63.1% of the oil-water interface being covered by CNFs. This finally led to the generation of highly stable O/W emulsions. This work demonstrated the potential of CNFs as promising "green" interface stabilizers for emulsion flooding EOR particularly for in situ surfactant generation scenarios.

Scalable synthesis of core-shell microgel particles using a 'dry water' method.

This proof-of-concept study demonstrates a facile and scalable 'dry water' method for producing micrometer-sized microgel particles by use of 'water-in-air' droplets as micro-reactors. Solid microgel particles could be easily produced by this method with no further purification. The microgel particles comprise of porous hydrophobic shells and hydrophilic cores and could absorb both oil and water. The swelling of the particles could be triggered by a surfactant under a wide range of conditions.

A Highly Tunable Approach to Enhance CO2 Capture with Liquid Alkali/amines.

A diverse range of alkali/amine infused hydrogels (AIHs) were generated by incorporating the liquids into a hydrogel particle for carbon capture application. As a consequence, the CO2 uptake was significantly enhanced owing to the increased contact area. This AIHs technique was highly tunable as it could be applicable to varying species of alkali chemicals and it was found that their molecular structure and architectures could impact the CO2 uptake. Compared to stirred bulk alkali/amine solutions, the CO2 absorption capacity of AIHs was increased by 400% within 30 min with a low hydrogel loading (10 w/w%). In addition, the recyclability of various AIHs was assessed and was found to be extremely encouraging. The effect of salinity on the performance of AIHs was also investigated and high salinity was found to have a minimal effect on CO2 absorption. Most importantly, the preparation of AIHs is fast and straightforward with few wastes and byproducts formed in the preparation process. In all, extensive investigations were presented and the AIHs were found to be a highly tunable and effective approach to enhance CO2 capture with liquid alkali/amines.

Investigations on the driving forces of the fluorocarbon surfactant-assisted spontaneous imbibition using thermogravimetric analysis (TGA).

Spontaneous imbibition is crucial for the development of matrix-fractured petroleum reservoirs. To improve the ultimate oil recovery, it is essential to demonstrate the role of the surfactant solution on the imbibition process. In this study, spontaneous imbibition experiments were carried out using self-prepared oil sand that to investigate the dependence of oil recovery on the concentration of a fluorocarbon surfactant (FS-30). Emulsion and solubilization were assessed to identify the correlation between oil-water interface properties and spontaneous imbibition. Moreover, thermogravimetric analysis (TGA) was also applied to accurately determine the imbibition recovery and look into the influence of components of crude oil on spontaneous imbibition. The maximum ultimate oil recovery in this work was 70.8% using 0.3 wt% FS-30, when the oil-solid adhesion tension, the capillary pressure (P C) and solubilization factor (S F) attained extreme values of -3.7002 mN m-1, 4.8751 MPa and 242.7 mL g-1, respectively. It was found that the surface activator played a critical role in promoting the imbibition process through altering the contact angle and interfacial tension. A negative adhesive tension and a positive capillary pressure would accordingly be generated, which facilitated the departure of oil droplets from the rock surface. In addition, it was observed that a lower solubilization factor and higher emulsion stability could favour spontaneous imbibition. Finally, heavier components in oil sands were more prone to be displaced than lighter counterparts, especially when the surfactant concentration was relatively high. This study may shed light on the effect of surfactants on spontaneous imbibition and thus is of great significance in understanding the underlying mechanism of the imbibition process.