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Yonghong Hu,Bo Cai,Ziyu Hu,Yanli Liu,Shengli Zhang,Haibo Zeng 한국물리학회 2015 Current Applied Physics Vol.15 No.3
The structural, electronic and optical properties of wurtzite MgZnO with Mg concentration ranging from 0 to 0.5 are studied using the first principle calculations. It's found that the lattice constants c and specific volume V of the MgZnO alloys decrease and their band gap widens as Mg concentration increases, which are in agreement with our experimental results. A particular Mg concentration is found to exist at around 0.375, equals to which the corresponding MgZnO alloy has the minimum width of the top valence band. This indicates that Mg concentration may be used to tune the electronic properties of MgZnO alloy. Meanwhile, it's also found that the energy response range of the optical spectrums decreases with the increase of Mg concentration. There are different energy shifts toward high energy (blue shift) of the peaks in the optical spectrums with the increase of Mg concentration, which are explained by the variations of the density of states in details. So the electronic and optical properties of MgZnO may be tuned through Mg concentration, and our research results may provide meaningful references to the development and design of photoelectric devices.
Prediction on the physical properties of CuInS2 with various anion positions
Yiming Ren,Yonghong Hu,Haibo Zeng,Li Xue 한국물리학회 2018 Current Applied Physics Vol.18 No.3
The effects of various anion displacements (u) on electronic structures, elastic constants, Debye temperature and the minimum thermal conductivity of CuInS2 are studied by first-principles calculation. The lattice constant couples with the anion displacement, however, they are not consistent with the relation proposed by Abrahams and Bernstein. When the anion displacement varies from 0.2 to 0.3, the Cu-S bond length is elongated, while the In-S bond length is shortened, which cause the increase of band gap with anion displacement. The anisotropies of sound velocities and lattice thermal conductivities are also discussed. The results imply that the lattice thermal conductivity along [110] direction is the smallest and decreases with u. These research findings shed light on improving the thermoelectric properties by manipulating u and the direction of propagation.
High-temperature-mixing hydrothermal synthesis of ZnO nanocrystals with wide growth window
Jun Wen,Yonghong Hu,Kongjun Zhu,Yufang Li,Jizhong Song 한국물리학회 2014 Current Applied Physics Vol.14 No.3
High-quality and controllable growth of nanocrystals (NCs) have been attracting great attention. Here, a high-temperature-mixing hydrothermal (HTMH) method was designed to synthesize ZnO NCs with high crystallinity and narrow size distribution in a wide growth window. Compared with conventional hydrothermal (CH) growth, zinc source and alkali precursors were intentionally separated in temperaturerising stage and permitted to mix at the starting of heat preservation stage of HTMH growth. Highly crystalline ZnO NCs with uniform spherical morphology can be formed at alkali concentration and temperature windows as wide as 0.1e0.5 M and 160e200 C, respectively. However, the products via CH method have much larger changes in not only morphology but also size. These results demonstrated that the high-temperature-mixing reaction greatly facilitates nucleation but depresses grain growth. Considering the simplicity and reproducibility, such HTMH method could have wide potentials for the fabrication of various functional nanocrystals.
Enhancement of thermal stability and chemical reactivity of phenolic resin ameliorated by nanoSiO2
Yajun Guo,Lihong Hu,Puyou Jia,Baofang Zhang,Yonghong Zhou 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.1
Phenolic resin has unsatisfactory thermal stability owing to the poor anti-oxidation property of methylene and phenol groups. To overcome this defect, a series of phenolic resin modified by nanoSiO2 based on the tetraethoxysilane (TEOS) was successfully prepared via sol-gel method using phenol as solvent. The effect of nanoSiO2 on the structures and properties of phenolic resin/foam was investigated. TGA and DTG indicated that the initial decomposition temperature of PR-0.5 (TEOS accounted for 0.5% of phenolic resin) was 41.8 oC higher than the neat PR-0. DSC revealed that the peak temperature presented a parabolic shape with the dosage of the TEOS, its maximal value resting on the PR-0.5. FT-IR and XRD demonstrated that chemical crosslink was reacted between PR and nanoSiO2 hydrolyzed by the TEOS, forming new chemical bands. Reactivity analysis illustrated that the free phenol content and the hydroxymethyl group content changed sharply in PF-0.5, implying it has highest reactivity.
Puyou Jia,Meng Zhang,Lihong Hu,Yonghong Zhou 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.3
Vegetable oil based plasticizers have potential use as nontoxic and sustainable plasticizer and as replacements for commonly used phthalate plasticizers. In this study, novel soybean oil based polyol esters (derived from glycerin or pentaerythritol, of which two were acetylated and two were additionally epoxidized) were synthesized and characterized with GPC, FT-IR and 1H NMR. Properties of poly (vinyl chloride) (PVC) plasticized with different soybean oil based polyol ester as main plasticizer were evaluated and compared to that of traditional plasticizers dioctyl phthalate (DOP) and epoxidized soybean oil (ESO). It has been proved that thermal stability of PVC blends could be improved by soybean oil based polyol ester plasticizers. Plasticizing effect of pentaerythritol derived soybean oil polyesters on PVC is better than that of DOP, ESO, and glycerin derived soybean oil polyesters. Tests of migration stability showed that with the increasing of the molecular weight, branching degree of molecular and ester bands of soybean oil based polyol ester, the migration stability was enhanced. This study may lead to the development of new type of PVC materials using soybean oil based polyol ester as main plasticizer.
Synthesis and characterization of glyceryl monooleate-based polyester
Puyou Jia,Caiying Bo,Lihong Hu,Yonghong Zhou 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.3
A unique biobased polyester poly(succinic acid-glyceryl monooleate) (PSAGMO) was synthesized andcharacterized from succinic acid (SA) and glyceryl monooleate (GMO). The polyester was characterized by gel permeationchromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic response spectroscopy(NMR). The polyester was used as the plasticizer of poly (vinyl chloride) (PVC). The mechanical propertiesand the thermodynamic properties of the blends were characterized. The TG-DTA data indicated that the thermal degradationtemperature (Td) of PVC blends plasticized with PSAGMO could increase from 249.3 oC to 255.6 oC. TheDMA showed that the glass transition temperature (Tg) of the PVC blends decreased from 49.5 oC to 35 oC. The mechanicalproperties indicated that the PSAGMO could decrease the tensile strength and increase the elongation at break ofthe PVC blends. This study may lead to the development of new type of PVC plasticizer based on renewable resource.