Now showing 1 - 5 of 5
  • Publication
    Shrinkage, hydration, and strength development of limestone calcined clay cement (LC3) with different sulfation levels
    ( 2022) ;
    Rotana Hay
    ;
    Kemal Celik
    This study investigated autogenous shrinkage of limestone calcined clay cement (LC3)-based mixes with various sulfation levels of hemihydrate. Physicochemical evolution and strength development were also monitored. Superior mechanical performance of the mixes was achieved at an optimal sulfation level, although the shrinkage was reduced with the sulfate content. Calorimetry data showed the hemihydrate delayed and broadened the second aluminate peak. Both gypsum and ettringite formed early during hydration, and carboaluminates were observed after 3 days of curing. Ettringite in the LC3 mixes was of smaller sizes in comparison to that in the ordinary Portland cement (OPC) mixes, attributable to the pore refinement in the LC3 matrices. The content of portlandite (Ca(OH)2) was reduced with the curing time due to pozzolanic reactions. The findings demonstrated a coupling effect of both the chemical and microstructural change on the observed autogenous shrinkage and the consequent performance of LC3-based concrete composites.
      37  4
  • Publication
    Hybrid Elastic Organic Crystals that Respond to Aerial Humidity
    ( 2022) ;
    Xu Yu
    ;
    Linfeng Lan
    ;
    Xuesong Yang
    ;
    Baolei Tang
    ;
    Xiaokong Liu
    ;
    Panče Naumov
    ;
    Hongyu Zhang
    Reshaping of elongated organic crystals that can be used as semiconductors, waveguides or soft robotic grippers by application of force or light is now a commonplace, however mechanical response of organic crystals to changes in humidity has not been accomplished yet. Here, we report a universal approach to instigating a humidity response into elastically bendable organic crystals that elicits controllable deformation with linear response to aerial humidity while retaining their physical integrity entirely intact. Hygroresponsive bilayer elements are designed by mechanically coupling a humidity-responsive polymer with elastic molecular crystals that have been mechanically reinforced by a polymer coating. As an illustration of the application of these cladded crystalline actuators, they are tested as active optical transducers of visible light where the position of light output can be precisely controlled by variations in aerial humidity. Within a broader context, the approach described here provides access to a vast range of mechanically robust, lightweight hybrid hygroresponsive crystalline materials.
      27  1Scopus© Citations 2
  • Publication
    Variation in sooting characteristics and cetane number of diesel with the addition of a monoterpene biofuel, α-pinene
    ( 2022) ;
    Alanood Al Zaabi
    ;
    Abhijeet Raj
    ;
    Mirella Elkadi
    ;
    Dalaver Anjum
    ;
    Azhagapillai Prabhu
    ;
    Gerardo D.J. Pena
    ;
    Abraham George
    ;
    Mariam Nasser Al Shebli
    Diesel fuel combustion generates soot particles, which are harmful for human health and the environment. To reduce soot emission, various solutions are proposed in the literature such as the use of metal-additives in fuels, fuel blending with biofuels, and the use of diesel particulate filters. This study analyses the effect of the addition of a bicyclic monoterpene hydrocarbon biofuel, α-pinene to diesel in different proportions on the fuel cetane number, sooting propensity, and the physicochemical properties of soot nanoparticles. The addition of 10% α-pinene to diesel exhibited a synergistic effect on sooting tendency and reduced the threshold sooting index of diesel by 21%, even though α-pinene is an unsaturated hydrocarbon, and had a minimal impact on cetane number, which reduced from 63.5 for diesel to 61.5 for the blended fuel. The influence of α-pinene addition to diesel on soot nanostructural characteristics and reactivity is determined through different characterization approaches including HRTEM, TGA, XRD, SEM-EDX, and EELS. The results indicate that α-pinene addition to diesel imposes curvatures in soot nanostructure, creates relatively smaller fringes (PAHs) in soot, and reduces soot aromatic content to improve soot oxidation rate.
      30  1
  • Publication
    A Low-Temperature-Resistant Flexible Organic Crystal with Circularly Polarized Luminescence
    ( 2022) ;
    Pan, Xiuhong
    ;
    Zheng, Anyi
    ;
    Di, Qi
    ;
    Duan, Pengfei
    ;
    Ye, Kaiqi
    ;
    Naumov, Panče
    ;
    Zhang, Hongyu
    ;
    Yu, Xu
    Flexible organic crystals with unique mechanical properties and excellent optical properties are of paramount significance for their wide applications in various research fields such as adaptive optics and soft robotics. However, low-temperature-resistant flexible organic crystal with circularly polarized luminescence (CPL) ability has never been reported. Herein, chiral organic crystals with CPL activity and low-temperature flexibility (77 K) are fabricated by the solvent diffusion method from chiral Schiff bases, S(R)-4- b romo-2-(((1- p henyl e thyl)imino) m ethyl) p henol (S(R)-BPEMP). The corresponding chiroptical properties for the two enantiomeric crystals were thoroughly investigated, including the measurements of circular dichroism (CD) and CPL. To the best of our knowledge, this is the first report on low-molecular-weight flexible organic crystals with CPL activity, and we believe that the results will give a new impetus to the research of organic crystals.
      4  10
  • Publication
    Organic Single‐Crystal Actuators and Waveguides that Operate at Low Temperatures
    ( 2022) ;
    Linfeng Lan
    ;
    Qi Di
    ;
    Xuesong Yang
    ;
    Xiaokong Liu
    ;
    Panče Naumov
    ;
    Hongyu Zhang
    Applications in extreme conditions, such as those encountered in space exploration, require lightweight materials that can retain their elasticity in extremely cold environments. However, cryogenic treatment of most soft polymeric and elastomeric materials results in complete loss of their ability for elastic flow, whereby such materials that are normally ductile become stiff, brittle, and prone to cracking. Here, a facile method for preparation of hybrid organic crystalline materials that are not only cryogenically robust but are also capable of large, recoverable, and reversible deformation at low temperatures is reported. To that end, flexible organic crystals are first mechanically reinforced by a polymer coating and combined with a thermally responsive polymer. The resulting hybrid materials respond linearly and reversibly to temperatures from −15 to −120 °C without fatigue in air as well as in cold vacuum. The approach proposed here not only circumvents one of the main drawbacks that are inherent to the amorphous nature and has thus far limited the applications of polymeric materials at low temperatures, but it also provides a cost-effective access to a myriad of lightweight sensing, electronic, optical or actuating devices that can operate in low-temperature environmental settings.
      19  1