The effects of nano‐C‐S‐H with different polymer stabilizers on early cement hydration

Abstract

A promising approach to accelerate cement hydration known as “seeding technology” has been discovered using nano‐particles to provide additional nucleation sites for growing of C‐S‐H. Two different types of polymer, polycarboxylate (PCE) and polysulfonate (PSE) were used as stabilizer to synthesize nano‐C‐S‐H via co‐precipitation process. The obtained C‐S‐H‐polymer composites were characterized by means of XRD, FTIR, thermogravimetric analysis (TGA), TEM, dynamic laser scattering (DLS), and BET. DLS measurement shows that the particle size of the obtained C‐S‐H‐polymer suspension ranges from 82.6 to 589.9 nm. The results of DLS and BET show that the particle size of the C‐S‐H particles synthesized using PCE polymer as stabilizer is smaller than those synthesized with PSE polymer, and hence the specific surface area is much higher. FTIR and TGA results confirm the presence of the polymers in the obtained C‐S‐H composites particles. XRD results indicate that the presence of the polymers reduces the crystallinity of C‐S‐H due to the absence of the d002 peak at 2θ of 7°. The calorimetry results show that the main hydration peak of cement is dramatically increased by the addition of the C‐S‐H‐polymer composites. It is interestingly found that the acceleration effect of the C‐S‐H‐polymer composites is linearly proportional to the total surface area of the nanoparticles introduced into the cement pastes. At the same time, it is found that the secondary hydration peak, usually known as the sulfate‐depletion peak, is greatly advanced by addition of the C‐S‐H nano‐particles in comparison with the blank cement paste. The acceleration effect of the nano‐C‐S‐H is further verified in a pure C3S system.

Hydrothermal Coating of Patterned Carbon Nanotube Forest for Structured Lithium‐Ion Battery Electrodes

“…Battery measurements performed in half‐cell configuration are summarized in Figure . The charge–discharge curves at 0.05C (Figure a) have a well‐defined voltage plateau at 0.75 V which agrees with the CV measurements (Figure b, 0.01 mV s −1 ) . This voltage plateau corresponds to the conversion of Fe 3+ to Fe 0 , whereas the redox current peak in the CV at 1.75 V corresponds to the oxidation reaction of Fe 0 to Fe 3+ (see Equation 1 in the Introduction) …”

“…α‐Fe 2 O 3 CNT Structure Synthesis : For the synthesis of iron oxide (Fe 2 O 3 ), a published protocol was modified for the use as a microwave‐assisted synthesis . The solution was prepared by dissolving 12.25 × 10 −3 m of iron(III) sulfate hydrate (Fe 2 (SO 4 ) 3 ·H 2 O, 244.98 g mol −1 , Fisher) in 35 mL of deionized (DI) water and 5 mL of glycerol (92.09 g mol −1 , Atom Scientific).…”

“…Alternatively, active battery particle suspensions have been drop‐casted on VACNT forests, but this requires attention to the stability of the CNT forest, and because this does not result in good interfaces between both materials; this often leads to shorter lifetimes . To address this challenge, we developed a protocol that allows for hydrothermal coating of metal oxide nanoparticles (α‐Fe 2 O 3 ‐nanoflakes) directly on patterned CNT forest without damaging the VACNT structures . To the best of our knowledge, one‐step hydrothermal synthesis has not been used to decorate patterned VACNT forests for battery electrodes previously as this process tends to destroy VACNT structures (see further).…”

“…Here, hematite was selected as an anode material to demonstrate this process. Hematite is interesting since it can be synthesized by a variety of well‐documented methods; moreover, it is cost effective and can store 1006 mAh g −1 following a conversion reaction Finally, because hematite nanoparticles are synthesized directly onto the CNT backbones, a binder is only needed locally at the base of the CNT structure to secure it on the Cu current collector foil (see Figure A right), which is advantageous compared to the standard battery electrodes, made from a slurry, which have binder throughout the electrode structure (see Figure A left). This allows to create thick electrodes (here 350 µm) where the top part of the battery is binder free to further enhance transport .…”

Calculation of the optical phonons in ordered Ba2MgWO6 perovskite using short‐range force field model

“…Raman and infrared spectroscopy became a useful tool to probe local disorder at B‐site and octahedral tilting in ordered perovskites by analyzing peak parameters such as intensity, position, width, and possible asymmetry . As a result of disorder, the A 1g mode starts to depict a broadening as a consequence of the antisite defects.…”