Key Engineering Materials Vols. 562-565

Abstract: We reported on a study upon a Surface-enhanced Raman Scattering (SERS) substrate produced from a large area multi-walled carbon nanotube (MWCNT) films decorated with Au nanoparticles. The morphology and spectrum of the MWCNTs/Au composite structure was characterized with scanning electron microscopy and spectrophotometer. The SERS signals of Rhodamine 6G (R6G) absorbed on the substrate were improved, which could contribute to the enlarged surface area for adsorption of molecules and Localized Plasmon Resonance Effect. The results indicated that it is potential to produce sensitive SERS substrates via further fine-tuning of size, shape of the nanostructure.

Abstract: Based on microelement manufacturing, semiconductor lithography technologies, The sensor chips fabricated to be small volume, high reliability, easy mass production, low cost, can resist to bad environment. In thin film pressure sensor chip, Ni-Cr alloy thin film is the key part, mostly influence the main electrical characteristics of the film pressure sensor chips. The resistance temperature characteristics changes on account of different proportions of Ni-Cr alloys. In this paper, two different proportions of Ni-Cr alloys were deposited and heat treated, the TCR of the alloys were tested, the causes were analyzed.

Abstract: In-situ composite of Al2O3/Fe-Al with Al2O3 fibers were prepared by partial oxidation of oxygen to Fe powder and Al power, crystal phase composition and elemental composition were analyzed by XRD, NORAN. The results indicated that, the crystal composition is determined by Aluminum content, when the content is enough, FeAl3, Al and Al2O3 will be gain, on the contrary, Fe2Al, FeAl, Fe3Al and Al2O3 will be gain; Al2O3 fibers were synthesized via VLS process, the quantity of Al2O3 fibers increased with the Al content, the whisker’s diameter was improved with increasing of sintering temperature.

Abstract: Surface nanocrystallization of 7A52 aluminium alloy was realized via non-equilibrium treatment induced by supersonic particles bombarding. Surface morphology and microstucture of the nanocrystalline surface layer were observed and analyzed by SEM, XRD and TEM, respectively. And the micro-hardness was tested using micro-hardness tester. The results indicated that the coarse grains on surface of 7A52 aluminium alloy could be refined to nanoscale via non-equilibrium treatment induced by supersonic particles bombarding. Average grain size on the superficial layer was approximately 40nm, micro-strain was about 0.12~0.14% and the thickness of nanocrystalline surface layer reached to approximately 80μm. Micro-hardness of the nanocrystalline surface layer was about 1.81times to that of the original substrate.

Abstract: Nanocrystalline cellulose (NCC) was used for improving the formaldehyde (HCHO) emission and bonding strength of urea formaldehyde (UF) resin adhesive in fiberboard and plywood. The original NCC was modified by 3-aminopropyltriethoxysilane (APTES) and the wetting property with UF resin adhesive was improved by 26.4%. The UF resin adhesive with modified NCC was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared (FT-IR). The crystal region of UF resin adhesive was influenced by NCC and the diffraction intensity of the peak at 2θ = 22.82° was enhanced significantly. The thermal stability of UF resin adhesive with 1.0% modified NCC increased by 4.9%. And modified NCC led hydroxyl groups into the UF resin adhesive. HCHO emission and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standards GB/T 17657-1999 and GB/T 9846-2004. The HCHO emission of fiberboard and plywood with 1.5% modified NCC decreased by 13.0% and 53.2%, respectively. The bonding strength of fiberboard increased by 158.3% (from 0.12 MPa of control group to 0.31 MPa of fiberboard with 1.5% modified NCC), while 1.5% modified NCC led to a 23.6% increase in the plywood.

Abstract: To investigate the effects of Si/O bond at the surface of silicon quantum dots (Si QDs) on the electronic properties of Si QDs, first principle calculations have been performed for Si QDs consisting of 10-87 Si atoms (0.6-1.5 nm in diameter) by using the CASTEP software package. In these calculations the Si dangling bonds on the surface of Si QDs are passivated by hydrogen atoms and oxygen. Four different oxygen configurations have been studied, they are double-bonded, backbonded, bridge-bonded and inserted, respectively. We find that a significant reduction of energy gap is caused by the presence of double-bonded oxygen, whereas for other three oxygen configurations there is just a slight reduction on energy gap. As a result, the model which contains Si=O bond is considered the most appropriate to explain the photoluminescence redshifts in oxidized porous silicon.

Abstract: Pure TiO₂, Nd³⁺doped TiO₂ and Nd ³⁺-CTAB co-doped TiO₂ nanometer thin films were prepared by the sol-gel technique with tetrabutyl titanate and neodymium nitrate as raw materials and surfactant cetyltrimethylammonium bromide (CTAB) as template. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Visible absorbance spectroscopy (UV-Vis). The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange. The results show that the all samples calcined at 500°C are all anatase, and there are slight red shifts of the Nd³⁺doped TiO₂ and Nd³⁺-CTAB co-doped TiO₂ films compared with pure TiO₂ films and the red shift of Nd ³⁺-CTAB co-doped TiO₂ is more obvious than that of Nd ³⁺ doped TiO₂, which is beneficial to improve the photocatalytic efficiency. The1.0% Nd³⁺-CTAB co-doped TiO₂ nanometer film calcined at 500°C had excellent photocatalytic efficiencies and the degradation rate of the film is more than 90% after 120 min.

Abstract: The eucalyptus cellulose micro/nano fibrils were prepared by using high intensity ultrasonication with chemical pretreatment. The basic characteristics of cellulose micro/nano fibrils were evaluated by wide-angle X-ray diffraction instrument (WAXD) and scanning electron microscopy (SEM).

Abstract: The properties of abrasives have great influences on the surface qualities of glass substrate, hard disk, etc^[1], during the chemical mechanical planarization (CMP) process. α-Al₂O₃ particles, as one of the most widely used abrasives in CMP slurries, often cause great surface defects because of its high hardness and unfeasible control of agglomeration during the synthesizing process ^[2,3]. In this paper, spherical nanocomposite alumina powders with particle sizes of 10-50 nm were prepared, via a homogeneous precipitation method. The structures and surface morphologies of the alumina nanopowders were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and atomic force microscope (AFM). The results showed that the nanopowders composed of both alpha and theta phase alumina, which had a small particle size and narrow size distributions. The CMP investigations performed on glass substrate showed that the nanocomposite alumina abrasives exhibited a better surface planarization performance than the pure single alpha phase Al2O3 nanopowders, with lower surface roughnesses and less scratches after CMP process. The results indicated that the current processing for the synthesis of nanocomposite Al₂O₃ powders were of great potentials for practical applications of Al₂O₃ based abrasives.

Abstract: Expanded graphite-based carbon/carbon composite (EGC) electrode was prepared by compressed expanded graphite impregnated in sucrose-phosphoric acid solution. The porous texture and microstructure of the composite were analyzed by physical adsorption measurements of N2 adsorption at 77K and SEM. The influence of electrolytic conditions on the phenol degradation was investigated. The results indicated that the EGC electrode was comprised of a graphite framework coated by a thin layer of activated carbon. It could be used as an anode to degrade phenol effectively in the solution by electrochemical oxidation. The data in the experiment showed that the removal efficiency of phenol increased with lowering the initial phenol concentration, increasing the current density and electrolyte concentration.