Yield, Water and Nitrogen Use of Spring Maize with Straw Mulch under Flat Bed And Ridge-Furrow Planting in Northeast China

Xianju Lu,Zizhong Li,Zenghui Sun 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Controlling the Thickness of Thermally Expanded Films of Graphene Oxide

Chen, Xianjue,Li, Wei,Luo, Da,Huang, Ming,Wu, Xiaozhong,Huang, Yuan,Lee, Sun Hwa,Chen, Xiong,Ruoff, Rodney S. American Chemical Society 2017 ACS NANO Vol.11 No.1

<P>'Paper-like' film material made from stacked and overlapping graphene oxide sheets can be exfoliated (expanded) through rapid heating, and this has until now been done with no control of the final geometry of the expanded graphene oxide material, i.e., the expansion has been physically unconstrained. (As a consequence of the heating and exfoliation, the graphene oxide is 'reduced', i.e., the graphene oxide platelets are deoxygenated to a degree.) We have used a confined space to constrain the expanding films to a controllable and uniform thickness. By changing the gap above the film, the final thickness of expanded films prepared from, e.g., a 10 mu m-thick graphene oxide film, could be controlled to values such as 20, 30, 50, or 100 mu m. When the expansion of the films was unconstrained, the final film was broken into pieces or had many cracks. In contrast, when the expansion was constrained, it never cracked or broke. Hot pressing the expanded reduced graphene oxide films at 1000 degrees C yielded a highly compact structure and promoted graphitization. Such thickness-controlled expansion of graphene oxide films up to tens or hundreds of times the original film thickness was used to emboss patterns on the films to produce areas with different thicknesses that remain connected 'in plane'. In another set of experiments, we treated the original graphene oxide film with NaOH before its controlled expansion resulted in a different structure featuring uniformly distributed pores and interconnected layers as well as simultaneous activation of the carbon.</P>

Graphitization of graphene oxide films under pressure

Chen, Xianjue,Deng, Xiaomei,Kim, Na Yeon,Wang, Yu,Huang, Yuan,Peng, Li,Huang, Ming,Zhang, Xu,Chen, Xiong,Luo, Da,Wang, Bin,Wu, Xiaozhong,Ma, Yufei,Lee, Zonghoon,Ruoff, Rodney S. Elsevier 2018 Carbon Vol.132 No.-

<P><B>Abstract</B></P> <P>Lightweight, flexible graphite foils that are chemically inert, high-temperature resistant, and highly electrically and thermally conductive can be used as component materials in numerous applications. “Graphenic” foils can be prepared by thermally transforming graphene oxide films. For this transformation, it is desirable to maintain a densely packed film structure at high heating rates as well as to lower the graphitizing temperatures. In this work, we discuss the pressure-assisted thermal decomposition of graphene oxide films by hot pressing at different temperatures (<I>i.e.</I>, 300 °C, 1000 °C, or 2000 °C). The films pressed at 1000 °C or 2000 °C were subsequently heated at 2750 °C to achieve a higher degree of graphitization. The combination of heating and pressing promotes the simultaneous thermal decomposition and graphitic transformation of G-O films. Films pressed at 2000 °C as well as films further graphitized at 2750 °C show high chemical purity, uniformity, and retain their flexibility. For films pressed at 2000 °C and then further heated at 2750 °C, the mechanical performances outperform the reported values of the “graphite” foils prepared by calendering exfoliated graphite flakes; the electrical conductivity is ∼3.1 × 10<SUP>5</SUP> S/m and the in-plane thermal conductivity is ∼1.2 × 10<SUP>3</SUP> W/(m·K).</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Maxillary protraction using customized mini-plates for anchorage in an adolescent girl with skeletal Class III malocclusion

Shuran Liang,Xianju Xie,Fan Wang,Qiao Chang,Hongmei Wang,Yuxing Bai 대한치과교정학회 2020 대한치과교정학회지 Vol.50 No.5

The treatment of skeletal Class III malocclusion in adolescents is challenging. Maxillary protraction, particularly that using bone anchorage, has been proven to be an effective method for the stimulation of maxillary growth. However, the conventional procedure, which involves the surgical implantation of mini-plates, is traumatic and associated with a high risk. Three-dimensional (3D) digital technology offers the possibility of individualized treatment. Customized miniplates can be designed according to the shape of the maxillary surface and the positions of the roots on cone-beam computed tomography scans; this reduces both the surgical risk and patient trauma. Here we report a case involving a 12-year-old adolescent girl with skeletal Class III malocclusion and midface deficiency that was treated in two phases. In phase 1, rapid maxillary expansion and protraction were performed using 3D-printed mini-plates for anchorage. The mini-plates exhibited better adaptation to the bone contour, and titanium screw implantation was safer because of the customized design. The orthopedic force applied to each mini-plate was approximately 400–500 g, and the plates remained stable during the maxillary protraction process, which exhibited efficacious orthopedic effects and significantly improved the facial profile and esthetics. In phase 2, fixed appliances were used for alignment and leveling of the maxillary and mandibular dentitions. The complete two-phase treatment lasted for 24 months. After 48 months of retention, the treatment outcomes remained stable.

The Vis-NIR multicolor emitting phosphor Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ for LED towards plant growth

Ziwei Zhou,Niumiao Zhang,Jiayu Chen,Xianju Zhou,Maxim S. Molokeev,Chongfeng Guo 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.65 No.-

Photosynthesis process is the basic for plant growth, which needs energy from the light. The pigments of chlorophyll a, b and bacteriochlorophyll are responsible for the absorption of light, in which blue, red and near-infrared (NIR) light directly or indirectly promote the plant growth and enhancement of nurtiments. It is important for plant to support absorbable light, and phosphhor-converted light emitting diodes (pc-LEDs) are low-cost, energy-saving and enviromental friendly devices for plant growth. To develop a phosphor with emission covering the blue, red and NIR, a series of phosphors Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ with blue, red and NIR multi-emitting were prepared. Their emissions not only match well with the absorption spectra of pigments in the plant, but also could be excited by near ultraviolet (n-UV) LED chip. The crystal structure of host Ba4Gd3Na3(PO4)6F2 was refined from the XRD data and three different crystallographic sites occupied by Eu2+ were determined through low temperature photoluminescence spectra. The energy transfer from Eu2+ to Pr3+ ions was also discussed in detail. Results indicated that the multi-emitting Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ can serve as a phosphor candidate for plant growth LEDs.

Dispersion behavior and thermal conductivity characteristics of Al2O3–H2O nanofluids

Dongsheng Zhu,Xinfang Li,Nan Wang,Xianju Wang,Jinwei Gao,Hua Li 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al2O3–H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al2O3–H2O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al2O3 suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al2O3–H2O nanofluids with an ounce of Al2O3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al2O3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%. Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al2O3–H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al2O3–H2O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al2O3 suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al2O3–H2O nanofluids with an ounce of Al2O3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al2O3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%.

Raman Spectral Band Oscillations in Large Graphene Bubbles

Huang, Yuan,Wang, Xiao,Zhang, Xu,Chen, Xianjue,Li, Baowen,Wang, Bin,Huang, Ming,Zhu, Chongyang,Zhang, Xuewei,Bacsa, Wolfgang S.,Ding, Feng,Ruoff, Rodney S. American Physical Society 2018 Physical Review Letters Vol.120 No.18

<P>Raman spectra of large graphene bubbles showed size-dependent oscillations in spectral intensity and frequency, which originate from optical standing waves formed in the vicinity of the graphene surface. At a high laser power, local heating can lead to oscillations in the Raman frequency and also create a temperature gradient in the bubble. Based on Raman data, the temperature distribution within the graphene bubble was calculated, and it is shown that the heating effect of the laser is reduced when moving from the center of a bubble to its edge. By studying graphene bubbles, both the thermal conductivity and chemical reactivity of graphene were assessed. When exposed to hydrogen plasma, areas with bubbles are found to be more reactive than flat graphene.</P>

Structural insights into hydrogenated graphite prepared from fluorinated graphite through Birch−type reduction

Zhang, Xu,Goossens, Karel,Li, Wei,Chen, Xianjue,Chen, Xiong,Saxena, Manav,Lee, Sun Hwa,Bielawski, Christopher W.,Ruoff, Rodney S. Elsevier 2017 Carbon Vol.121 No.-

<P>Hydrogenated graphite was synthesized through a Birch-type reduction by treating fluorinated graphite ((CFx)(n), x similar to 1.1) with a solution of Li in liquid NH3 followed by the addition of H2O as the proton donor. The conversion was evaluated by Fourier transform infrared spectroscopy, Raman spectroscopy and powder X-ray diffraction. X-ray photoelectron spectroscopy and combustion elemental analysis were used to determine and quantify the chemical composition, giving an empirical formula of C1H0.60O0.06N0.01 for the product with no more than 2 at.% of fluorine atoms remaining. Thermal dehydrogenation of the hydrogenated material - as investigated by thermogravimetric analysis coupled to mass spectrometry - predominately occurs over the range of 350-600 degrees C. The product was also analyzed using scanning electron microscopy, atomic force microscopy and transmission electron microscopy, which collectively supported the formation of hydrogenated graphene sheets through a wet-chemical route. To elucidate the structure of the hydrogenated sample, the material was investigated by solid-state nuclear magnetic resonance spectroscopy. Direct pulse and cross-polarization nuclear magnetic resonance measurements, including spin counting, spectral editing and 2D heteronuclear correlation experiments, revealed the nature of the sp(3)- and sp(2)-hybridized carbon nuclei, and indicated that methine, methylene and quaternary sp(3)-carbon atoms were present in the hydrogenated material. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Role of Graphene in Water-Assisted Oxidation of Copper in Relation to Dry Transfer of Graphene

Luo, Da,You, Xueqiu,Li, Bao-Wen,Chen, Xianjue,Park, Hyo Ju,Jung, Minbok,Ko, Taeg Yeoung,Wong, Kester,Yousaf, Masood,Chen, Xiong,Huang, Ming,Lee, Sun Hwa,Lee, Zonghoon,Shin, Hyung-Joon,Ryu, Sunmin,Kwak American Chemical Society 2017 Chemistry of materials Vol.29 No.10

<P>The process of oxidation of a copper surface coated by a layer of graphene in water-saturated air at 50 degrees C was studied where it was observed that oxidation started at the graphene edge and was complete after 24 h. Isotope labeling of the oxygen gas and water showed that the oxygen in the formed copper oxides originated from water and not from the oxygen in air for both Cu and graphene-coated Cu, and this has interesting potential implications for graphene as a protective coating for Cu in dry air conditions. We propose a reaction pathway where surface hydroxyl groups formed at graphene edges and defects induce the oxidation of Cu. DFT simulation shows that the binding energy between graphene and the oxidized Cu substrate is smaller than that for the bare Cu substrate, which facilitates delamination of the graphene. Using this process, dry transfer is demonstrated using poly(bisphenol A carbonate) (PC) as the support layer. The high quality of the transferred graphene is demonstrated from Raman maps, XPS, STM, TEM, and sheet resistance measurements. The copper foil substrate was reused without substantial weight loss to grow graphene (up to 3 cycles) of equal quality to the first growth after each cycle. It was found that dry transfer yielded graphene with less Cu impurities as compared to methods using etching of the Cu substrate. Using PC yielded graphene with less polymeric residue after transfer than the use of poly(methyl methacrylate) (PMMA) as the supporting layer. Hence, this dry and clean delamination technique for CVD graphene grown on copper substrates is highly advantageous for the cost-effective large-scale production of graphene, where the Cu substrate can be reused after each growth.</P>

Controlled Folding of Single Crystal Graphene

Wang, Bin,Huang, Ming,Kim, Na Yeon,Cunning, Benjamin V.,Huang, Yuan,Qu, Deshun,Chen, Xianjue,Jin, Sunghwan,Biswal, Mandakini,Zhang, Xu,Lee, Sun Hwa,Lim, Hyunseob,Yoo, Won Jong,Lee, Zonghoon,Ruoff, Rod American Chemical Society 2017 Nano letters Vol.17 No.3

<P>Folded graphene in which two layers are stacked with a twist angle between them has been predicted to exhibit unique electronic, thermal, and magnetic properties. We report the folding of a single crystal monolayer graphene film grown on a Cu(111) substrate by using a tailored substrate having a hydrophobic region and a hydrophilic region. Controlled film delamination from the hydrophilic region was used to prepare macroscopic folded graphene with good uniformity on the millimeter scale. This process was used to create many folded sheets each with a defined twist angle between the two sheets. By identifying the original lattice orientation of the monolayer graphene on Cu foil, or establishing the relation between the fold angle and twist angle, this folding technique allows for the preparation of twisted bilayer graphene films with defined stacking orientations and may also be extended to create folded structures of other two-dimensional nanomaterials.</P>