Yun Zhao - Cochemist

Core/shell structured composites of hollow spherical CoFe2O4 and CNTs as absorbing materials

Co-reporter:Shenli Zhang, Zhengwu Qi, Yun Zhao, Qingze Jiao, Xiang Ni, Yajiao Wang, Yuan Chang, Chang Ding

Journal of Alloys and Compounds 2017 Volume 694() pp:309-312

Publication Date(Web):15 February 2017

DOI:10.1016/j.jallcom.2016.09.324

•Core/shell composites of hollow spherical CoFe2O4 and CNTs were insitu synthesized by CVD.•CoFe2O4 hollow spheres were used as cores, catalysts and magnetic elements simultaneously.•The shell of CNTs uniformly grew on the surface of CoFe2O4 hollow sphere core.•The core/shell composites showed excellent microwave absorbing performance.Core/shell structured composites of hollow spherical CoFe2O4 and CNTs were in situ synthesized using a CVD method with ethanol as a carbon source. CoFe2O4 hollow spheres were used as cores, catalysts and magnetic ingredients simultaneously. It was found that the shell of CNTs uniformly grew on the surface of CoFe2O4 hollow sphere cores. The reflection loss reached −32.8 dB at 11.7 GHz for the core/shell composites with a thickness of 2 mm.

Controllable synthesis of composites of ZSM-5 and KIT-1 using an ionic liquid as template

Co-reporter:Haoliang Xue, Zhuangzhang He, Yun Zhao, Qingze Jiao, Qin Wu, Hansheng Li

Solid State Sciences 2017 Volume 64() pp:29-33

Publication Date(Web):February 2017

DOI:10.1016/j.solidstatesciences.2016.12.010

•ZSM-5/KIT-1 composites were synthesized using an ionic liquid as a template.•The ZSM-5/KIT-1 composites show a crystalline MFI framework and a three-dimensional network of worm-like channels.•The ratio of ZSM-5 and KIT-1 could be simply adjusted by controlling the pre-crystalline time.ZSM-5/KIT-1 composites were synthesized using an ionic liquid as a template. The structures and morphologies of as-obtained products were characterized using an infrared spectroscopy, X-ray diffractometer, N2 adsorption/desorption, scanning electron microscopy and transmission electron microscopy. The resultant zeolites show a fully crystalline microporous MFI zeolite framework and a three-dimensional network of short worm-like channels. Mesopores and microspores of 4.2 and 0.8 nm in diameter coexist in the zeolite composites. Moreover, the ratio of ZSM-5 and KIT-1 could be simply adjusted by controlling the pre-crystalline time. We believe that the strategy for fabricating ZSM-5/KIT-1 through a simple method could potentially promote the large-scale production of zeolite composites.

Synthesis of well-dispersed TiO2@reduced graphene oxide (rGO) nanocomposites and their photocatalytic properties

Co-reporter:Muhammad Sohail, Haoliang Xue, Qingze Jiao, Hansheng Li, Khakemin Khan, Shanshan Wang, Yun Zhao

Materials Research Bulletin 2017 Volume 90(Volume 90) pp:

Publication Date(Web):1 June 2017

DOI:10.1016/j.materresbull.2017.02.025

•TiO2@reduced graphene oxide nanocomposites were successfully prepared using graphene oxide particles as supports.•TiO2 nanoparticles are distributed uniformly on the surface of reduced graphene oxide particles.•TiO2@reduced graphene oxide nanocomposites show better photo catalytic activities than pure TiO2 nanoparticles.In this work, graphene oxide (GO) nanosheets were prepared using a modified Hummers technique and as-obtained GO nanosheets were converted into particles by a spray drying method. Titanium dioxide (TiO2) nanoparticles were grown on the surface of GO particles to get TiO2@reduced graphene oxide (rGO) nanocomposites. Morphologies and structures of as-prepared pure TiO2 nanoparticles, rGO particles and their composites were characterized by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The photocatalytic activities of TiO2@rGO nanocomposites were evaluated using UV-vis spectroscopy for the degradation of methylene blue. All the composites show better photocatalytic activities upon degradation of methylene blue than pure TiO2. The degradation rate of methylene blue is 92% for TiO2@rGO nanocomposites with TiO2 mass ratio of 84 wt%, while it is 71% for pure TiO2. rGO plays a key role in the charge recombination to enhance the electron hole separation.TiO2@reducedgrapheneoxide(rGO) nanocomposites were successfully prepared using spray-dried GO particle as supports. All TiO2@rGO nanocomposites show better photo catalytic activities upon degradation of methylene blue than pure TiO2.Download high-res image (139KB)Download full-size image

In situ synthesis of Mg/Fe LDO/carbon nanohelix composites as absorbing materials

Co-reporter:Shenli Zhang, Qingze Jiao, Chaoxiang Wang, Hui Yu, Yun Zhao, Hansheng Li, Qin Wu

Journal of Alloys and Compounds 2016 Volume 658() pp:505-512

Publication Date(Web):15 February 2016

DOI:10.1016/j.jallcom.2015.10.266

•Mg/Fe LDO/carbon nanohelix composites were in situ synthesized by CVD.•Flakes of Mg/Fe LDHs were used as catalysts and precursor simultaneously.•Mg/Fe LDO/carbon nanohelix showed excellent microwave absorbing property.Mg/Fe layered double oxide (LDO)/carbon nanohelix composites were prepared by an in situ chemical vapor deposition with Mg/Fe layered double hydroxides as catalysts and ethanol as carbon sources. The as-synthesized products were characterized using an X-ray diffractometer, field emission electron microscope, transmission electron microscope, energy-dispersive spectroscope, Raman spectroscope, vibrating sample magnetometer and vector network analyzer. It was found that helical carbon nanotubes deposited on two sides of Mg/Fe LDO flakes. A minimum reflection loss (RL) of −35.0 dB was observed at 11.9 GHz for Mg/Fe LDO/carbon nanohelix composites with a thickness of 3.0 mm, and the effective absorption frequency (RL < −10 dB) ranged from 10.1 to 15.3 GHz. The absorbing performance of the Mg/Fe LDO/carbon nanohelix composites was better than that of Mg/Fe LDOs.

Basic polymerized imidazolide-based ionic liquid: an efficient catalyst for aqueous Knoevenagel condensation

Co-reporter:Libing Ding, Hansheng Li, Yaping Zhang, Kun Zhang, Hong Yuan, Qin Wu, Yun Zhao, Qingze Jiao and Daxin Shi

RSC Advances 2015 vol. 5(Issue 27) pp:21415-21421

Publication Date(Web):18 Feb 2015

DOI:10.1039/C5RA01700A

A novel basic polymerized ionic liquid (BPIL): polymeric 1-[(4-ethenylphenyl)methyl]-3-propylimidazolium imidazolide was synthesized and characterized by Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) and electron spray ionization mass spectrometry (ESI-MS). The BPIL was used as an efficient catalyst for aqueous Knoevenagel condensations with extended substrates. In comparison with common base catalysts, the BPIL showed high catalytic activity, which was ascribed to the cooperation between the strong basicity and the high surface activity. Moreover, the BPIL with high molecular weight has high surface activity and low catalytic activity. In addition, the BPIL was easily recovered and maintained high catalytic activity after five cycles of use in the system using benzaldehyde and malononitrile as substrates.

Preparation of rugby-shaped CoFe2O4 particles and their microwave absorbing properties

Co-reporter:Shenli Zhang, Qingze Jiao, Yun Zhao, Hansheng Li and Qin Wu

Journal of Materials Chemistry A 2014 vol. 2(Issue 42) pp:18033-18039

Publication Date(Web):05 Sep 2014

DOI:10.1039/C4TA04286G

Porous rugby-shaped CoFe2O4 particles were synthesized using a vapor diffusion method in combination with calcination. The morphologies and structures of the as-prepared CoFe2O4 particles were characterized by field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, and N2 adsorption–desorption measurement. Results showed that uniform CoFe2O4 rugbies were about 1.1 μm in length and 500 nm in width at the widest point. Rugby-shaped CoFe2O4 nanoparticles were assembled by the layers of nanoparticles and exhibit porous structures. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained rugby-shaped products exhibited a saturation magnetization of 73.4 emu g−1 and a coercivity of 2218.7 Oe at room temperature. A minimum reflection loss of −34.1 dB was observed at 13.4 GHz for the sample with a thickness of 2.5 mm, and the effective absorption frequency (RL < −10 dB) ranged from 12.3 to 14.9 GHz, indicating the excellent microwave absorption performance of the novel products. The absorbing performance of the CoFe2O4 rugbies was better than that of the CoFe2O4 nanoparticles.

Vapor diffusion synthesis of CoFe2O4 hollow sphere/graphene composites as absorbing materials

Co-reporter:Min Fu, Qingze Jiao, Yun Zhao and Hansheng Li

Journal of Materials Chemistry A 2014 vol. 2(Issue 3) pp:735-744

Publication Date(Web):01 Nov 2013

DOI:10.1039/C3TA14050D

Novel CoFe2O4 hollow sphere/graphene composites were synthesized by a facile vapor diffusion method in combination with calcination at 550 °C. The structure and morphology of as-prepared hybrid materials were characterized by electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Uniform CoFe2O4 hollow spheres with a diameter of about 500 nm and a shell thickness of approximately 50 nm were homogeneously distributed on graphene sheets. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss of −18.5 dB was observed at 12.9 GHz for the CoFe2O4 hollow sphere/graphene composites with a thickness of 2 mm, and the effective absorption frequency ranged from 11.3 to 15.0 GHz. The CoFe2O4 hollow sphere/graphene composites exhibited better microwave absorbing performance than the CoFe2O4 hollow spheres. A possible formation mechanism for CoFe2O4 hollow sphere/graphene composites was proposed.

One-step vapor diffusion synthesis of uniform CdS quantum dots/reduced graphene oxide composites as efficient visible-light photocatalysts

Co-reporter:Min Fu, Qingze Jiao and Yun Zhao

RSC Advances 2014 vol. 4(Issue 44) pp:23242-23250

Publication Date(Web):12 May 2014

DOI:10.1039/C4RA02000F

CdS quantum dots (QDs)/reduced graphene oxide (RGO) composites were synthesized through a one-step vapor diffusion process in the presence of ethylene glycol. The in situ growth of CdS QDs and the reduction of graphene oxide (GO) were completed simultaneously. Fourier transform infrared spectra, X-ray diffraction patterns, X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the reduction of GO. Electron microscopy indicated uniform CdS QDs with size around 4–7 nm were well distributed on the RGO sheets. The transient photocurrent response, electrochemical impedance spectroscopy and diffuse reflectance UV-visible spectra of CdS QDs/RGO composites and CdS were tested to explain the role of RGO for the photocatalytic reaction. As-obtained composites exhibited better photocatalytic properties than pure CdS under visible light irradiation. The influence of different contents of GO on photocatalytic performance was also investigated. A possible photocatalytic mechanism of CdS QDs/RGO composites was proposed.

In situ preparation of polyimide/amino-functionalized carbon nanotube composites and their properties

Co-reporter:Jinhuan Wang;Qingze Jiao;Hansheng Li;Bingzhi Guo

Polymer Composites 2014 Volume 35( Issue 10) pp:1952-1959

Publication Date(Web):

DOI:10.1002/pc.22854

In order to improve the dispersion of carbon nanotubes (CNTs) in polyimide (PI) matrix and the interfacial interaction between CNTs and PI, 4,4′-diaminodiphenyl ether (ODA)-functionalized carbon nanotubes (CNTs-ODA) were synthesized by oxidation and amidation reactions. The structures and morphologies of CNTs-ODA were characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and thermal gravimetric analysis. Then a series of polyimide/amino-functionalized carbon nanotube (PI/CNT-ODA) nanocomposites were prepared by in situ polymerization. CNTs-ODA were homogeneously dispersed in PI matrix. The influence of CNT-ODA content on mechanical properties of PI/CNT-ODA nanocomposites was investigated. It was found that the mechanical properties of nanocomposites were enhanced with the increase in CNT-ODA loading. When the content of CNTs-ODA was 3 wt%, the tensile strength of PI/CNT-ODA nanocomposites was up to 169.07 MPa (87.11% higher than that of neat PI). The modulus of PI/CNTs-ODA was increased by 62.64%, while elongation at break was increased by 66.05%. The improvement of the mechanical properties of PI/CNT-ODA nanocomposites were due to the strong chemical bond and interfacial interaction between CNTs-ODA and PI matrix. POLYM. COMPOS., 35:1952–1959, 2014. © 2014 Society of Plastics Engineers

Preparation of NiFe2O4 nanorod–graphene composites via an ionic liquid assisted one-step hydrothermal approach and their microwave absorbing properties

Co-reporter:Min Fu, Qingze Jiao and Yun Zhao

Journal of Materials Chemistry A 2013 vol. 1(Issue 18) pp:5577-5586

Publication Date(Web):01 Mar 2013

DOI:10.1039/C3TA10402H

Novel NiFe2O4 nanorod–graphene composites were synthesized by a facile one-step hydrothermal process in the presence of 1-propyl-3-hexadecylimidazolium bromide ([PHeIm][Br]). The structure and morphology of as-prepared hybrid materials were characterized by FESEM, TEM, HRTEM, AFM, XRD, FTIR, XPS and Raman spectroscopy. The results showed that uniform NiFe2O4 nanorods with a typical length of about 400 nm and a diameter of about 50 nm were well distributed on graphene sheets. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained composites exhibited a saturation magnetization of 22.5 emu g−1 and a coercivity of 48.67 Oe at room temperature. A minimum reflection loss of −29.2 dB was observed at 16.1 GHz with a thickness of 2.0 mm, and the effective absorption frequency (RL < −10 dB) ranged from 13.6 to 18 GHz, indicating the excellent microwave absorption performance of the novel composites in the range of 13.6–18 GHz. The absorbing performance of the NiFe2O4 nanorod–graphene composites was better than that of the NiFe2O4 nanoparticle–graphene composites.

In situ synthesis of iron-filled nitrogen-doped carbon nanotubes and their magnetic properties

Co-reporter:Qingze Jiao, Liang Hao, Qingyan Shao, Yun Zhao

Carbon 2013 Volume 61() pp:647-649

Publication Date(Web):September 2013

DOI:10.1016/j.carbon.2013.05.043

Iron-filled nitrogen-doped carbon (Fe@CNx) nanotubes were prepared by an in situ chemical vapor deposition with ferrocene as catalyst and ethylenediamine as carbon and nitrogen sources. The as-grown products were characterized using an X-ray diffractometer, transmission electron microscope, X-ray photoelectron spectroscopy, thermogravimetric analyzer and vibrating sample magnetometer. It was found that the “bamboo-like” N-doped carbon nanotubes were filled with 41.1 wt% of Fe nanoparticles. The coercivity and saturation magnetization of Fe@CNx nanotubes were much larger than those of carbon nanotubes and CNx nanotubes.

In situ fabrication and characterization of cobalt ferrite nanorods/graphene composites

Co-reporter:Min Fu, Qingze Jiao, Yun Zhao

Materials Characterization 2013 Volume 86() pp:303-315

Publication Date(Web):December 2013

DOI:10.1016/j.matchar.2013.10.019

•Reduction of GO and formation of ferrites were accomplished in a one-step reaction.•Ionic liquid was used to control 1D growth of ferrite nanorods for the first time.•Cobalt ferrite nanorods/graphene composites showed dielectric and magnetic loss.•Cobalt ferrite nanorods/graphene composites exhibited better absorbing properties.Cobalt ferrite nanorods/graphene composites were prepared by a one-step hydrothermal process using NaHSO3 as the reducing agent and 1-propyl-3-hexadecylimidazolium bromide as the structure growth-directing template. The reduction of graphene oxide and the in situ formation of cobalt ferrite nanorods were accomplished in a one-step reaction. The structure and morphology of as-obtained composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, atomic force microscope, X-ray diffractometer, Fourier transform infrared spectra, X-ray photoelectron spectroscopy and Raman spectroscopy. Uniform rod-like cobalt ferrites with diameters of about 100 nm and length of about 800 nm were homogeneously distributed on the graphene sheets. The hybrid materials showed a saturation magnetization of 42.5 emu/g and coercivity of 495.1 Oe at room temperature. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss (RL) of − 25.8 dB was observed at 16.1 GHz for the cobalt ferrite nanorods/graphene composites with a thickness of 2 mm, and the effective absorption frequency (RL < − 10 dB) ranged from 13.5 to 18.0 GHz. The composites exhibited better absorbing properties than the cobalt ferrite nanorods and the mixture of cobalt ferrite nanorods and graphene.

Preparation of Hollow Co3O4 Microspheres and Their Ethanol Sensing Properties

Co-reporter:Qingze Jiao, Min Fu, Chao You, Yun Zhao, and Hansheng Li

Inorganic Chemistry 2012 Volume 51(Issue 21) pp:11513-11520

Publication Date(Web):October 8, 2012

DOI:10.1021/ic3013602

The hollow Co3O4 microspheres were prepared by a gas–liquid diffusion reaction in the presence of ionic liquid [Bmim][BF4] in combination with calcination at 300 °C. Their structures and morphologies were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy. The growth mechanism of hollow Co3O4 microspheres was proposed. The ethanol sensing properties were measured using a WS-30A gas sensor measurement system. The influence of working temperatures, ethanol concentrations, and specific surface areas of Co3O4 microspheres on the ethanol sensing properties was investigated. The hollow Co3O4 microspheres showed excellent sensitivity to ethanol vapor at a lower operating temperature.

Synthesis of Zn/Co/Fe-layered double hydroxide nanowires with controllable morphology in a water-in-oil microemulsion

Co-reporter:Hongyu Wu, Qingze Jiao, Yun Zhao, Silu Huang, Xuefei Li, Hongbo Liu, Mingji Zhou

Materials Characterization 2010 Volume 61(Issue 2) pp:227-232

Publication Date(Web):February 2010

DOI:10.1016/j.matchar.2009.12.003

The Zn/Co/Fe-layered double hydroxide nanowires were synthesized via a reverse microemulsion method by using cetyltrimethyl ammonium bromide (CTAB) /n-hexane/n-hexanol/water as Soft-Template. ZnSO4, CoSO4, Fe2(SO4)3 and urea were used as raw materials. The influence of reaction temperature, time, urea concentration and Cn (molar ratio of cetyltrimethyl ammonium bromide to water) on the structure and morphology of Zn/Co/Fe-layered double hydroxides was investigated. The samples were characterized using Transmission Electron Microscopy (TEM), Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD) and Infrared Absorption Spectrum (IR). The results indicate that higher temperature is beneficial to the formation of layered double hydroxides, but particles apart from nanowires could be produced if temperature is up to 120 °C. By varying the temperature, reaction time, urea concentration and Cn, we got the optimum conditions of synthesizing uniform Zn/Co/Fe-layered double hydroxide nanowires: 100 °C, more than 12 h, Cn: 30–33, urea concentration: 0.3 M.

Preparation of honeycomb films from nitryl poly(ether ether ketone)s via water-droplet templating

Co-reporter:Pei Zhang;Qingze Jiao;Ye Tian;Qingyun Li;Xiaolin Wang

Journal of Applied Polymer Science 2009 Volume 113( Issue 4) pp:2090-2095

Publication Date(Web):

DOI:10.1002/app.29950

Abstract

The fabrication of honeycomb-patterned films from nitryl poly(ether ether ketone)s (PEEK-NO₂) in a high-humidity atmosphere was reported in this article. PEEK-NO₂ was prepared through acid (nitric acid and sulfuric acid) nitration from poly(ether ether ketone)s (PEEK). The obtained polymer, which was characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) showed excellent solubility and thermal stability. Some influence factors on the pattern formation and the fabrication of the porous structure, such as the solution concentration, the solvent, and the atmosphere humidity, were investigated. The results showed that with the increase of the solution concentration, the aperture of the film diminished gradually; the lower the solvents´ boiling point were, the smaller the films´ apertures were and the more regular the pores´ arrange; only under high-humidity circumstances could obvious and ordered honeycomb films be formed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Preparation and magnetic property of the composite of nitrogen-doped carbon nanotubes decorated with nickel nanoparticles

Co-reporter:Yong Cao, Qingze Jiao, Hongbo Liu, Xinliang Tang, Yun Zhao

Physica E: Low-dimensional Systems and Nanostructures 2009 Volume 41(Issue 10) pp:1824-1827

Publication Date(Web):October 2009

DOI:10.1016/j.physe.2009.07.007

A magnetic composite of nitrogen-doped carbon nanotubes (CNx) decorated with nickel nanoparticles was synthesized by a chemical precipitation and deoxidization method. The decorated CNx were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD pattern showed that CNx, nickel nanoparticles and little nickel oxides coexisted in the composite, TEM observation indicated that nickel nanoparticles were highly dispersed on the outer walls of CNx, Magnetic measurements by VSM demonstrated that the saturated magnetization and remanence of CNx were improved, while the coercivity was lowered after decorating with nickel nanoparticles.

Controlling of morphology of Ni/Al-LDHs using microemulsion-mediated hydrothermal synthesis

Co-reporter:Yun Zhao;Fenfei Xiao;Qingze Jiao

Bulletin of Materials Science 2008 Volume 31( Issue 6) pp:831-834

Publication Date(Web):2008 November

DOI:10.1007/s12034-008-0132-z

A quaternary microemulsion, cetyltrimethylammonium bromide (CTAB)/water/n-hexane/n-hexanol, was selected for the synthesis of Ni/Al-layered double hydroxides (LDHs). Ni/Al-LDHs with nanowire-, spherical-, rod- and tube-like morphologies were prepared via the microemulsion-mediated hydrothermal synthesis. The CTAB concentration played an important role in determining the morphology of Ni/Al-LDHs. The structure, composition and morphology of the obtained Ni/Al-LDH nanostructures were investigated by X-ray diffraction, inductively coupled plasma emission spectroscopy, infrared spectrometer and transmission electron microscopy. A possible formation mechanism of Ni/Al-LDH nanostructures is proposed.

Catalytic synthesis of carbon nanostructures using layered double hydroxides as catalyst precursors

Co-reporter:Yun Zhao, Qingze Jiao, Chunhua Li, Ji Liang

Carbon 2007 Volume 45(Issue 11) pp:2159-2163

Publication Date(Web):October 2007

DOI:10.1016/j.carbon.2007.06.071

Layered double hydroxides with different components but similar iron content such as Fe0.1Mg2Al0.9, Fe0.1Zn2Al0.9 and Fe0.1Cu2Al0.9 were prepared using a coprecipitation reaction. Then mixed oxides were obtained by calcination of these layered double hydroxide precursors, and their catalytic activities were examined during synthesis of various carbon nanostructures. It was found that single-walled carbon nanotubes were synthesized using a Fe0.1Mg2Al0.9 mixed oxide catalyst, while multi-walled carbon nanotubes and carbon nanofibers resulted from Fe0.1Zn2Al0.9 and Fe0.1Cu2Al0.9 mixed oxides as catalysts, respectively.

Effect of microstructures of Pt catalysts supported on carbon nanotubes (CNTs) and activated carbon (AC) for nitrobenzene hydrogenation

Co-reporter:Yun Zhao, Chun-Hua Li, Zhen-Xing Yu, Ke-Fu Yao, Sheng-Fu Ji, Ji Liang

Materials Chemistry and Physics 2007 Volume 103(2–3) pp:225-229

Publication Date(Web):15 June 2007

DOI:10.1016/j.matchemphys.2007.02.045

Pt catalysts supported on carbon nanotubes (CNTs) and activated carbon (AC) were prepared. The structure of the catalysts was characterized using BET, TEM, XPS techniques. The catalytic performance for nitrobenzene hydrogenation was tested. The results show that the mesoporous textures of CNTs make the outer surfaces of CNTs accessible for Pt ion. So Pt particles on CNTs are much smaller, and the proper concentration of surface groups on CNTs makes Pt easy for reducibility. Pt particles on AC are larger due to the microporous texture, and reduction at higher temperature is necessary because of more functional groups on AC. The Pt/CNTs catalysts reduced at lower temperature, exhibit higher activity than the Pt/AC catalysts for nitrobenzene hydrogenation.

Hydrothermal Synthesis of Nanorods and Nanowires of Mg/Al Layered Double Hydroxides

Co-reporter:Yun ZHAO, Qing-ze JIAO, Xue-jia DING, Li-qun ZHANG, Yuan-yuan LIU

Chemical Research in Chinese Universities 2007 Volume 23(Issue 5) pp:622-624

Publication Date(Web):September 2007

DOI:10.1016/S1005-9040(07)60134-2

Preparation of carbon nanofibers over carbon nanotube-nickel catalyst in propylene decomposition

Co-reporter:Yun Zhao;Chunhua Li;Kefu Yao;Ji Liang

Journal of Materials Science 2007 Volume 42( Issue 12) pp:4240-4244

Publication Date(Web):2007 June

DOI:10.1007/s10853-006-0676-5

A variety of structural and morphological forms of carbon nanofibers, which comprise perpendicularly and obliquely stacking graphite fibers and the two composite forms made of outer coaxial graphite tubes and inner perpendicularly or obliquely stacking fibers, were fabricated in catalytically decomposing propylene–hydrogen mixture over carbon nanotube-supported nickel catalysts. The growth mechanism for composite carbon nanofibers was proposed. The different types of carbon filaments are promising to be applied in catalyst support and capsules for drug delivery or nanoscale electrical devices.

Preparation of rugby-shaped CoFe2O4 particles and their microwave absorbing properties

Co-reporter:Shenli Zhang, Qingze Jiao, Yun Zhao, Hansheng Li and Qin Wu

Journal of Materials Chemistry A 2014 - vol. 2(Issue 42) pp:NaN18039-18039

Publication Date(Web):2014/09/05

DOI:10.1039/C4TA04286G

Porous rugby-shaped CoFe2O4 particles were synthesized using a vapor diffusion method in combination with calcination. The morphologies and structures of the as-prepared CoFe2O4 particles were characterized by field emission scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, and N2 adsorption–desorption measurement. Results showed that uniform CoFe2O4 rugbies were about 1.1 μm in length and 500 nm in width at the widest point. Rugby-shaped CoFe2O4 nanoparticles were assembled by the layers of nanoparticles and exhibit porous structures. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained rugby-shaped products exhibited a saturation magnetization of 73.4 emu g−1 and a coercivity of 2218.7 Oe at room temperature. A minimum reflection loss of −34.1 dB was observed at 13.4 GHz for the sample with a thickness of 2.5 mm, and the effective absorption frequency (RL < −10 dB) ranged from 12.3 to 14.9 GHz, indicating the excellent microwave absorption performance of the novel products. The absorbing performance of the CoFe2O4 rugbies was better than that of the CoFe2O4 nanoparticles.

Vapor diffusion synthesis of CoFe2O4 hollow sphere/graphene composites as absorbing materials

Co-reporter:Min Fu, Qingze Jiao, Yun Zhao and Hansheng Li

Journal of Materials Chemistry A 2014 - vol. 2(Issue 3) pp:NaN744-744

Publication Date(Web):2013/11/01

DOI:10.1039/C3TA14050D

Novel CoFe2O4 hollow sphere/graphene composites were synthesized by a facile vapor diffusion method in combination with calcination at 550 °C. The structure and morphology of as-prepared hybrid materials were characterized by electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Uniform CoFe2O4 hollow spheres with a diameter of about 500 nm and a shell thickness of approximately 50 nm were homogeneously distributed on graphene sheets. The electromagnetic parameters were measured using a vector network analyzer. A minimum reflection loss of −18.5 dB was observed at 12.9 GHz for the CoFe2O4 hollow sphere/graphene composites with a thickness of 2 mm, and the effective absorption frequency ranged from 11.3 to 15.0 GHz. The CoFe2O4 hollow sphere/graphene composites exhibited better microwave absorbing performance than the CoFe2O4 hollow spheres. A possible formation mechanism for CoFe2O4 hollow sphere/graphene composites was proposed.

Preparation of NiFe2O4 nanorod–graphene composites via an ionic liquid assisted one-step hydrothermal approach and their microwave absorbing properties

Co-reporter:Min Fu, Qingze Jiao and Yun Zhao

Journal of Materials Chemistry A 2013 - vol. 1(Issue 18) pp:NaN5586-5586

Publication Date(Web):2013/03/01

DOI:10.1039/C3TA10402H

Novel NiFe2O4 nanorod–graphene composites were synthesized by a facile one-step hydrothermal process in the presence of 1-propyl-3-hexadecylimidazolium bromide ([PHeIm][Br]). The structure and morphology of as-prepared hybrid materials were characterized by FESEM, TEM, HRTEM, AFM, XRD, FTIR, XPS and Raman spectroscopy. The results showed that uniform NiFe2O4 nanorods with a typical length of about 400 nm and a diameter of about 50 nm were well distributed on graphene sheets. The magnetic and electromagnetic parameters were measured using a vibrating sample magnetometer and a vector network analyzer, respectively. The obtained composites exhibited a saturation magnetization of 22.5 emu g−1 and a coercivity of 48.67 Oe at room temperature. A minimum reflection loss of −29.2 dB was observed at 16.1 GHz with a thickness of 2.0 mm, and the effective absorption frequency (RL < −10 dB) ranged from 13.6 to 18 GHz, indicating the excellent microwave absorption performance of the novel composites in the range of 13.6–18 GHz. The absorbing performance of the NiFe2O4 nanorod–graphene composites was better than that of the NiFe2O4 nanoparticle–graphene composites.