Molecular Beam Epitaxy of Highly Crystalline Monolayer Molybdenum Disulfide on Hexagonal Boron Nitride

Fu, Deyi,Zhao, Xiaoxu,Zhang, Yu-Yang,Li, Linjun,Xu, Hai,Jang, A-Rang,Yoon, Seong In,Song, Peng,Poh, Sock Mui,Ren, Tianhua,Ding, Zijing,Fu, Wei,Shin, Tae Joo,Shin, Hyeon Suk,Pantelides, Sokrates T.,Zho American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.27

<P>Atomically thin molybdenum disulfide (MoS2), a direct-band-gap semiconductor, is promising for applications in electronics and optoelectronics, but the scalable synthesis of highly crystalline film remains challenging. Here we report the successful epitaxial growth of a continuous, uniform, highly crystalline monolayer MoS2 film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS2 grown on h-BN primarily consists of two types of nucleation grains (0 aligned and 60 degrees antialigned domains). By adopting a high growth temperature and ultralow precursor flux, the formation of 60 degrees antialigned grains is largely suppressed. The resulting perfectly aligned grains merge seamlessly into a highly crystalline film. Large-scale monolayer MoS2 film can be grown on a 2 in. h-BN/sapphire wafer, for which surface morphology and Raman mapping confirm good spatial uniformity. Our study represents a significant step in the scalable synthesis of highly crystalline MoS2 films on atomically flat surfaces and paves the way to large-scale applications.</P>

Seismic behavior and strength of L-shaped steel reinforced concrete column-concrete beam planar and spatial joints

Zongping Chen,Deyi Xu,Jinjun Xu,Ni Wang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.3

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

Stability of heavy metals in soil washing residue with and without biochar addition under accelerated ageing

Shen, Zhengtao,Hou, Deyi,Zhao, Bin,Xu, Wendi,Ok, Yong Sik,Bolan, Nanthi S.,Alessi, Daniel S. Elsevier 2018 Science of the Total Environment Vol.619 No.-

<P><B>Abstract</B></P> <P>Soil washing residue (SWR), which typically concentrates the washed toxic metals and is comprised of high contents of clay particles, may pose risks to the surrounding environment. This study aims to simulate accelerated ageing to assess the stability of selected metals (Cd<SUP>2+</SUP> (132mg/kg), Cu<SUP>2+</SUP> (248mg/kg) and Pb<SUP>2+</SUP> (3470mg/kg)) in a SWR (89.68% of clay) with and without biochar treatment. The soil was incubated under constant moisture and wet-dry cycles (accelerated ageing), respectively, and the mobility and fractions of heavy metals in the soils with and without biochar treatment were examined. Under the constant moisture condition, biochar addition at 5% w/w reduced the leached Cd<SUP>2+</SUP> (by 1.81%) and Cu<SUP>2+</SUP> (by 8.70%) from SWR at day 1 and the leached Cu<SUP>2+</SUP> (by 51.08%) and Pb<SUP>2+</SUP> (by 25.36%) from SWR at day 14; however, the leached metals in the TCLP solution from the biochar-amended soils still exceed the regulatory limits (1mg/L for Cd<SUP>2+</SUP>, 5mg/L for Pb<SUP>2+</SUP>, no regulatory limits for Cu<SUP>2+</SUP>). Conversely, accelerated ageing (14days) significantly increased the fractions of exchangeable Cd<SUP>2+</SUP> (from 3.63–3.94% to 6.21–6.29%) and Pb<SUP>2+</SUP> (from 0.025–0.027% to 0.034–0.041%) as well as the TCLP leachabilities of Cd<SUP>2+</SUP> (from 2.91–3.28% to 3.46–3.73%), Cu<SUP>2+</SUP> (from 0.08–0.10% to 0.03–0.06%) and Pb<SUP>2+</SUP> (from 0.25–0.35% to 0.52–0.57%) in the soils, as compared with those incubated under constant moisture, regardless of biochar addition. This study reveals challenges associated with stabilising SWR due to the presence of residual fine-grained particles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cd<SUP>2+</SUP> and Pb<SUP>2+</SUP> in soil washing residue (SWR) exceeds TCLP regulation limit. </LI> <LI> Heavy metal mobility in SWR was reduced by biochar addition. </LI> <LI> Accelerated ageing mobilised heavy metals in SWR regardless of biochar addition. </LI> <LI> Accelerated ageing show SWR poses long-term risks to the environment. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Wavelet Noise Elimination & Its Application in Acoustic Leak Detection of Fast Reactor Steam Generator

Liu Zhanhui,Niu Xiaodong,Mu Guangyu,Shang Deyi,Xu Zhiwen,Guo Xiaoxin,Pang Yunjie 대한전자공학회 2005 ITC-CSCC :International Technical Conference on Ci Vol.2005 No.4

Organo-layered double hydroxides for the removal of polycyclic aromatic hydrocarbons from soil washing effluents containing high concentrations of surfactants

Zhang, Ming,Zhao, Cheng,Li, Jinye,Xu, Liheng,Wei, Fang,Hou, Deyi,Sarkar, Binoy,Ok, Yong Sik Elsevier 2019 Journal of hazardous materials Vol.373 No.-

<P><B>Abstract</B></P> <P>Disposal of soil washing effluent (SWE) resulting from the surfactant-enhanced remediation of soil containing hydrophobic organic contaminants (HOCs)is complicated because of the presence of high levels of surfactants. The synthesized layered double hydroxides (LDHs), modified with sodium dodecyl sulfonate (SDS) in different loading amounts (organo-LDHs),were evaluated in this study as sorbents for the removal of two typical HOCs, phenanthrene (PHE) and pyrene (PYR),from a simulative SWE. The results showed that the organo-LDHs can effectively sorb PHE and PYR from the SWE within an equilibrium time of 2 h. All isotherms were linear and the sorption capabilities of the organo-LDHs increased almost linearly with the increase in the amount of SDS loaded on the LDHs. Besides, the surface areas of the organo-LDHs decreased sharply with the increase in SDS loading owing to the hindrance of the exposed surface of the LDHs by the incorporated SDS. These findings indicated that partitioning dominated the sorption process rather than adsorption, and the strong affinity of HOCs towards the organic phase in LDHs assisted in the effective removal of polycyclic aromatic hydrocarbons (PAHs) from the SWE. Furthermore, the sorption capabilities of organo-LDHs towards PHE and PYR at the higher loading amounts of SDS were much greater than that of commercial activated carbon at the higher concentration ranges of PAHs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dodecyl sulfonate anion modified LDHs are employed for the removal of PHE and PYR in soil washing effluent (SWE). </LI> <LI> Organo-LDHs showed superior performance in PHE removal from SWE than that of commercial activated carbon. </LI> <LI> Partitioning of PHE and PYR in the organic fraction of the organo-LDHs was the main mechanism. </LI> <LI> Using organo-LDHs for the separation of HOCs from surfactants in SWE facilitated reuse of the surfactants. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

The potential value of biochar in the mitigation of gaseous emission of nitrogen

Thangarajan, Ramya,Bolan, Nanthi S.,Kunhikrishnan, Anitha,Wijesekara, Hasintha,Xu, Yilu,Tsang, Daniel C.W.,Song, Hocheol,Ok, Yong Sik,Hou, Deyi Elsevier 2018 Science of the Total Environment Vol.612 No.-

<P><B>Abstract</B></P> <P>Nitrogen (N) losses through gaseous emission of ammonia (NH<SUB>3</SUB>) and nitrous oxide (N<SUB>2</SUB>O) can contribute to both economic loss and environmental degradation. This study examined the effect of biochar and a chemical nitrification inhibitor, dicyandiamide (DCD), on N transformation and N losses via gaseous emission of NH<SUB>3</SUB> and N<SUB>2</SUB>O from agricultural soils treated with a range of organic and inorganic N sources. The addition of DCD reduced N<SUB>2</SUB>O emission from both organic and inorganic N sources treated soils by 75%, but increased ammonium (NH<SUB>4</SUB> <SUP>+</SUP>) concentration and subsequently induced high NH<SUB>3</SUB> emission from the soils. In contrast, the addition of biochar reduced both N<SUB>2</SUB>O and NH<SUB>3</SUB> emissions from organic and inorganic N sources treated soils by 23% and 43%, respectively. The effectiveness of biochar and DCD in reducing NH<SUB>3</SUB> volatilization and N<SUB>2</SUB>O emission depends on the nature of the N sources and their initial mineral N concentration. The study demonstrated that biochar can be used to mitigate N losses resulting from NH<SUB>3</SUB> volatilization and N<SUB>2</SUB>O emission.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biochar and dicyandiamide (DCD) effects on N transformation and losses were studied. </LI> <LI> DCD decreased N<SUB>2</SUB>O emission from N sources applied soil but increased NH<SUB>3</SUB> emission. </LI> <LI> Although DCD significantly reduced N<SUB>2</SUB>O emission, biochar decreased total N loss by 25%. </LI> <LI> Biochar can replace chemical nitrification inhibitors thereby mitigating gaseous N loss. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>