ABSTRACT
In the present work, the temperature-dependent phase behavior of a C10E4 based microemulsion is studied in different meso-macroporous glasses, as a function of their pore diameter. The phase behavior in these pores is investigated by small-angle X-ray scattering (SAXS). The crucial parameter we discuss based on the SAXS results is the domain size of the bicontinuous phase. Using a simplified model to fit the scattering data, we can observe the microemulsion inside the pores. These experiments reveal a temperature-dependent change in domain sizes of the bicontinuous microemulsion only for large pores.
ABSTRACT
In an in-depth study of the mechanism of cation release from carboxymethyl cellulose hydrogels synthesized through Schiff base reaction, we analyze the differences in the release kinetics of potassium, calcium, and iron cations with Peleg model at pH values of pHâ 3.5 and pHâ 8.5 using ICP-OES (inductively coupled plasma optical emission spectroscopy) technique.
ABSTRACT
Hydrothermal carbonization (HTC) is an efficient thermochemical method for the conversion of organic feedstock to carbonaceous solids. HTC of different saccharides is known to produce microspheres (MS) with mostly Gaussian size distribution, which are utilized as functional materials in various applications, both as pristine MS and as a precursor for hard carbon MS. Although the average size of the MS can be influenced by adjusting the process parameters, there is no reliable mechanism to affect their size distribution. Our results demonstrate that HTC of trehalose, in contrast to other saccharides, results in a distinctly bimodal sphere diameter distribution consisting of small spheres with diameters of (2.1 ± 0.2) µm and of large spheres with diameters of (10.4 ± 2.6) µm. Remarkably, after pyrolytic post-carbonization at 1000 °C the MS develop a multimodal pore size distribution with abundant macropores > 100 nm, mesopores > 10 nm and micropores < 2 nm, which were examined by small-angle X-ray scattering and visualized by charge-compensated helium ion microscopy. The bimodal size distribution and hierarchical porosity provide an extraordinary set of properties and potential variables for the tailored synthesis of hierarchical porous carbons, making trehalose-derived hard carbon MS a highly promising material for applications in catalysis, filtration, and energy storage devices.
ABSTRACT
In this work, a continuous flow setup for in situ investigation of microgel growth with small-angle X-ray scattering (SAXS) is established. Poly(N-n-propylacrylamide) (PNNPAM) and poly(N-isopropylacrylamide) (PNIPAM) microgels are synthesized in H2O at different residence times inside a continuous flow reactor. The microgels are investigated by in situ SAXS and ex situ photon correlation spectroscopy. The size of the microgels was found to be reproducible in independent experiments with run times of up to 7 h. Already the scattering curves of the microgels with a time of residence of 15 min show a well-defined form factor. Further analysis of the scattering profiles confirms the spherical shape of the microgels. At a residence time of 2 min, the scattering intensity is significantly lower corresponding to a smaller particle size. The experimental conditions remain constant over time, which is crucial for long-time experiments. The PNNPAM system is found to be more suitable for the flow reactor experiment with in-line SAXS as it shows less polymer deposition in the tubing and forms particles with lower polydispersity. The presented reactor is characterized by a compact design and offers a plug-and-play setup close to the sample environment. This work paves the way for investigations of microgel growth at e.g. synchrotron X-ray beamlines.
