Query: Effect of the TiO2 amounts on microwave absorption properties of Ni/TiO2 heterostructure composites

Candidate papers:

abstract: Abstract Hybrid core/shell Ni/TiO2 composites were prepared with different contents of tetrabutyl orthotitanate (TBOT) The microwave absorption properties of the Ni/TiO2 composites have been studied in the range of 1 18 GHz. The amount of TiO2 is found to have a great impact on the microwave absorption of this metal semiconductor composite. The microwave absorption properties of Ni/TiO2 heterostructure prepared at 2 mL TBOT were highly enhanced compared with other two samples. The excellent microwave absorption properties are due to the proper complementarities between magnetic loss and dielectric loss, geometrical effect, the natural resonance and multipolarization. The multiple dielectric resonances are attributed to interfacial polarization and the magnetic resonances are ascribed to natural resonance.
author_names: Biao Zhao

Gang Shao

Bingbing Fan

Yongqiang Chen

Rui Zhang
title: Effect of the TiO2 amounts on microwave absorption properties of Ni/TiO2 heterostructure composites
year: 2014

abstract: Photoexcited semiconductor nanoparticles undergo charge equilibration when they are in contact with metal nanoparticles. Such a charge distribution has direct influence in dictating the energetics of the composite by shifting the Fermi level to more negative potentials. The transfer of electrons to Au nanoparticles has now been probed by exciting TiO(2) nanoparticles under steady state and laser pulse excitation. Equilibration with the C(60)/C(60) redox couple provides a means to determine the apparent Fermi level of the TiO(2) Au composite system. The size dependent shift in the apparent Fermi level of the TiO(2) Au composite (20 mV for 8 nm diameter and 40 mV for 5 nm and 60 mV for 3 nm gold nanoparticles) shows the ability of Au nanoparticles to influence the energetics by improving the photoinduced charge separation. Isolation of individual charge transfer steps from UV excited TiO(2) Au C(60) has provided mechanistic and kinetic information on the role of metal in semiconductor assisted photocatalysis and size dependent catalytic activity of metal semiconductor nanocomposites.
author_names: Vaidyanathan Ravi Subramanian

Eduardo E Wolf

Prashant V Kamat
title: Catalysis with TiO2/gold nanocomposites. Effect of metal particle size on the Fermi level equilibration.
venue: Journal of the American Chemical Society
year: 2004

abstract: Climate change and the consumption of non renewable resources are considered as the greatest problems facing humankind. Because of this, photocatalysis research has been rapidly expanding. TiO2 nanoparticles have been extensively investigated for photocatalytic applications including the decomposition of organic compounds and production of H2 as a fuel using solar energy. This article reviews the structure and electronic properties of TiO2, compares TiO2 with other common semiconductors used for photocatalytic applications and clarifies the advantages of using TiO2 nanoparticles. TiO2 is considered close to an ideal semiconductor for photocatalysis but possesses certain limitations such as poor absorption of visible radiation and rapid recombination of photogenerated electron/hole pairs. In this review article, various methods used to enhance the photocatalytic characteristics of TiO2 including dye sensitization, doping, coupling and capping are discussed. Environmental and energy applications of TiO2, including photocatalytic treatment of wastewater, pesticide degradation and water splitting to produce hydrogen have been summarized.
author_names: Shipra Mital Gupta

Manoj Tripathi
title: A review of TiO2 nanoparticles
year: 2011

abstract: In this study, yolk shell Ni@SnO2 composites with a designable interspace were successfully prepared by the simple acid etching hydrothermal method. The Ni@void@SnO2 composites were characterized by X ray diffraction, Fourier transform infrared spectroscopy, X ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that interspaces exist between the Ni cores and SnO2 shells. Moreover, the void can be adjusted by controlling the hydrothermal reaction time. The unique yolk shell Ni@void@SnO2 composites show outstanding electromagnetic wave absorption properties. A minimum reflection loss (RLmin) of 50.2 dB was obtained at 17.4 GHz with absorber thickness of 1.5 mm. In addition, considering the absorber thickness, minimal reflection loss, and effective bandwidth, a novel method to judge the effective microwave absorption properties is proposed. On the basis of this method, the best microwave absorption properties were obtained with a 1.7 mm thick absorber layer (RLmin= 29.7 dB, bandwidth of 4.8 GHz) The outstanding electromagnetic wave absorption properties stem from the unique yolk shell structure. These yolk shell structures can tune the dielectric properties of the Ni@air@SnO2 composite to achieve good impedance matching. Moreover, the designable interspace can induce interfacial polarization, multiple reflections, and microwave plasma.
author_names: Biao Zhao

Xiaoqin J Guo

Wanyu Zhao

Jiushuai Deng

Gang Shao

Bingbing Fan

Zhongyi Bai

Rui Zhang
title: Yolk Shell Ni@SnO2 Composites with a Designable Interspace To Improve the Electromagnetic Wave Absorption Properties.
venue: ACS applied materials interfaces
year: 2016

abstract: Jenny Schneider, Masaya Matsuoka, Masato Takeuchi, Jinlong Zhang, Yu Horiuchi, Masakazu Anpo, and Detlef W. Bahnemann* +Institut fur Technische Chemie, Leibniz Universitat Hannover, Callinstrasse 3, D 30167 Hannover, Germany +Faculty of Engineering, Osaka Prefecture University, 1 Gakuen cho, Sakai Osaka 599 8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China
author_names: Jenny Schneider

Masaya Matsuoka

Masato Takeuchi

Jinlong Zhang

Yu Horiuchi

Masakazu Anpo

Detlef W Bahnemann
title: Understanding TiO2 photocatalysis: mechanisms and materials.
venue: Chemical reviews
year: 2014

abstract: Herein, Ni doped ZnO TiO2 composites were prepared by facile sol gel approach and were characterized by X ray diffraction (XRD) transmission electron microscopy (TEM) UV visible diffuse reflectance spectroscopy (UV Vis DRS) X ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) The results indicated that the Ni ions can be incorporated into the lattice of TiO2 structure and replace Ti. The introduction of Ni expanded light absorption of TiO2 to visible region, increased amount of surface hydroxyl groups and physically adsorbed oxygen (as the electronic scavenges) and then enhanced separation rate of photogenerated carriers. The photodegradation test of reactive brilliant blue (KN R) under simulated solar light indicated that Ni doped ZnO TiO2 composites have better photocatalytic activities, as compared to those of TiO2 and ZnO TiO2.
author_names: Xiao-Hang Zou

Xiaoli Dong

Limei Wang

Hongchao Ma

Xinxin Zhang

Xiufang Zhang
title: Preparation of Ni Doped ZnO TiO2 Composites and Their Enhanced Photocatalytic Activity
year: 2014

abstract: A combination nanostructured matrix with metal Au nanoislands and semiconductor TiO2 nanowires is presented to enhance both desorption and ionization efficiency in laser desorption/ionization (LDI) mass spectrometry. The heterostructure of Au nanoislands on TiO2 nanowires was fabricated via (1) TiO2 nanowire synthesis through a modified wet corrosion method and (2) Au nanoisland formation through thermal annealing of a sputtered Au layer on the TiO2 nanowires. Herein, the synergistic effect of this heterostructure for highly efficient ion production was experimentally elucidated in terms of the formation of high temperature on the surface of Au and the creation of a Schottky barrier at the Au TiO2 interface. Finally, four types of immunosuppressors were analyzed to demonstrate the improved ionization performance of the heterostructure for LDI mass spectrometry.
author_names: Moon-Ju Kim

Tae Gyeong Yun

Joo-Yoon Noh

Jong-Min Park

Min-Jung Kang

Jae-Chul Pyun
title: Synergistic Effect of the Heterostructure of Au Nanoislands on TiO2 Nanowires for Efficient Ionization in Laser Desorption/Ionization Mass Spectrometry.
venue: ACS applied materials interfaces
year: 2019

abstract: Core shell microspheres with Ni cores and two phases of TiO2 (anatase, rutile) shells have been successfully synthesized. The crystal structure, morphology and microwave absorption properties of the as prepared composites were analyzed by X ray diffraction, field emission scanning electron microscopy, energy dispersive X ray spectroscopy, transmission electron microscopy, and vector network analysis. The core shell rutile TiO2 coated Ni exhibits better antioxidation ability than that of pure Ni due to the presence of the rutile TiO2 shell, which is confirmed by the thermal gravimetric analysis (TGA) In comparison with bare Ni, these two composites show better microwave absorption properties. The minimum reflection loss (RL) is 38.0 dB at 11.1 GHz with a thickness of only 1.8 mm for the Ni@TiO2 (rutile) composite. The enhanced absorption capability arises from the efficient complementarities between the magnetic loss and dielectric loss, multiple interfacial polarization, high thermal conductivity of rutile TiO2 and microwave attenuation constant. These results show that the thin high efficiency rutile TiO2 coated Ni composite is a great potential microwave absorbing material for practical applications.
author_names: Biao Zhao

Gang Shao

Bingbing Fan

Wanyu Zhao

Yajun Xie

Rui Zhang
title: Facile preparation and enhanced microwave absorption properties of core shell composite spheres composited of Ni cores and TiO2 shells.
venue: Physical chemistry chemical physics PCCP
year: 2015

abstract: Uniform BaTiO(3) nanotubes were synthesized via a simple wet chemical route at low temperature (50 degC) The as synthesized BaTiO(3) nanotubes were characterized using powder X ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X ray photoelectron spectroscopy. The results show that the BaTiO(3) nanotubes formed a cubic phase with an average diameter of ~10 nm and wall thickness of 3 nm at room temperature. The composition of the mixed solvent (ethanol and deionized water) was a key factor in the formation of these nanotubes; we discuss possible synthetic mechanisms. The microwave absorption properties of the BaTiO(3) nanotubes were studied at microwave frequencies between 0.5 and 15 GHz. The minimum reflection loss of the BaTiO(3) nanotubes/paraffin wax composite (BaTiO(3) nanotubes weight fraction 70% reached 21.8 dB ~99.99% absorption) at 15 GHz, and the frequency bandwidth less than 10 dB is from 13.3 to 15 GHz. The excellent absorption property of BaTiO(3) nanotubes at high frequency indicates that these nanotubes could be promising microwave absorbing materials.
author_names: Yaofeng Zhu

Li Zhang

Toshiaki Natsuki

Ya Fu

Qingqing Ni
title: Facile synthesis of BaTiO3 nanotubes and their microwave absorption properties.
venue: ACS applied materials interfaces
year: 2012

abstract: Highly uniform core shell composites, polypyrrole@polyaniline (PPy@PANI) have been successfully constructed by directing the polymerization of aniline on the surface of PPy microspheres. The thickness of PANI shells, from 30 to 120 nm, can be well controlled by modulating the weight ratio of aniline and PPy microspheres. PPy microspheres with abundant carbonyl groups have very strong affinity to the conjugated chains of PANI, which is responsible for the spontaneous formation of uniform core shell microstructures. However, the strong affinity between PPy microspheres and PANI shells does not promote the diffusion or reassembly of two kinds of conjugated chains. Coating PPy microspheres with PANI shells increases the complex permittivity and creates the mechanism of interfacial polarization, where the latter plays an important role in increasing the dielectric loss of PPy@PANI composites. With a proper thickness of PANI shells, the moderate dielectric loss will produce well matched characteristic impedance, so that the microwave absorption properties of these composites can be greatly enhanced. Although PPy@PANI composites herein consume the incident electromagnetic wave by absolute dielectric loss, their performances are still superior or comparable to most PANI based composites ever reported, indicating that they can be taken as a new kind of promising lightweight microwave absorbers. More importantly, microwave absorption of PPy@PANI composites can be simply modulated not only by the thickness of the absorbers, but also the shell thickness to satisfy the applications in different frequency bands.
author_names: Chunhua Tian

Yunchen Du

Ping Xu

Rong Qiang

Ying Wang

Ding Ding

Jianlei Xue

Jun Ma

Hongtao Zhao

Xijiang Han
title: Constructing Uniform Core Shell PPy@PANI Composites with Tunable Shell Thickness toward Enhancement in Microwave Absorption.
venue: ACS applied materials interfaces
year: 2015