Activated carbon derived from rice husk by NaOH activation and its application in supercapacitor

Four activated carbon(AC) samples prepared from rice husk under different activation temperatures have been characterized by N2adsorption–desorption isotherms, thermogravimetric analysis(TGA–DTA), Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The specific surface area of AC sample reached 2681 m2 g 1under activation temperature of 800 1C. The AC samples were then tested as electrode material; the specific capacitance of the as-prepared activated carbon electrode was found to be 172.3 F g 1using cyclic voltammetry at a scan rate of 5 mV s 1and 198.4 F g 1at current density 1000 mA g 1in the charge/discharge mode.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

Porous SiC ceramics fabricated by quick freeze casting and solid state sintering

Porous SiC ceramics with uniform microstructure were fabricated by quick freezing in liquid nitrogen and solid state sintering.Poly(vinyl alcohol)(PVA) was added as binder and pore morphology controller in this work.The microstructure and mechanical properties of porous SiC ceramics could be controlled by the composition of the aqueous slurries.Both solid content of the slurries and PVA content impacted on the pore structures and mechanical properties of the porous SiC ceramics.The solid content of slurries and PVA content varied from 60 to 67.5 wt%and 2-6 wt%,respectively.Besides,the grain morphology of ceramics was also tailored by changing the sintering temperature from 2050 to 2150 ℃.Porous SiC ceramics with an average porosity of 42.72%,flexural strength of 59.28 MPa were obtained at 2150 ℃ from 67.5 wt% slurries with 2 wt% PVA.     

Core loss analysis of Finemet type nanocrystalline alloy ribbon with different thickness

Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability,magnetization and low core loss.In this paper,Fe_(73.5)Cu_1Nb_3Si_(15.5)B_7(at%)nanocrystalline alloy ribbons,with ultra-thin thickness of 14μm,and also 18 and 22μm,were prepared by a planar flow casting method with a single roller device.Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing.The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10–100 kHz,at induction amplitudes of 100–500 m T,at room temperature.It was found that the excess eddy current loss P_(ex)was the dominant factor in the overall core loss above 10 k Hz.The toroidal samples made of the 14μm thickness ribbon exhibit very low total core loss of 48 W/kg at a frequency of100 kHz and magnetic flux density of 300 mT.The ratio of the P_(ex)was up to 89%at 100 kHz.The ribbon with lower thickness exhibits lower P_(ex)and therefore lower total core loss.The domain structure evidences were found.It indicates that the ribbons with small thickness are preferable for application in high frequency condition.     

Preparation and catalytic effect of porous Co3O4 on the hydrogen storage properties of a Li-B-N-H system

A porous Co_3O_4 with a particle size of 1–3 μm was successfully prepared by heating Co-based metal organic frameworks MOF-74(Co) up to 500 °C in air atmospheric conditions. The as-prepared porous Co_3O_4 significantly reduced the dehydrogenation temperatures of the LiBH_4-2LiNH_2 system and improved the purity of the released hydrogen. The LiBH_4-2LiNH_2-0.05/3Co_3O_4 sample started to release hydrogen at 140 °C and released hydrogen levels of approximately 9.7 wt% at 225 °C. The end temperature for hydrogen release was lowered by 125 °C relative to that of the pristine sample. Structural analyses revealed that the as-prepared porous Co_3O_4 is in-situ reduced to metallic Co, which functions as an active catalyst, reducing the kinetic barriers and lowering the dehydrogenation temperatures of the LiBH_4-2LiNH_2 system. More importantly, the porous Co_3O_4-containing sample exhibited partially improved reversibility for hydrogen storage in the LiBH_4-2LiNH_2 system.     

Preparation and characterization of poly(vinylidene fluoride) composite membranes blended with nano-crystalline cellulose

Poly(vinylidene fluoride) (PVDF) composite membranes blended with nano-crystalline cellulose (NCC) for ultrafiltration were prepared by a Loeb-Sourirajan (L-S) phase inversion process.The effects of NC...     

Properties of garnet-type Li6La3ZrTaO12 solid electrolyte films fabricated by aerosol deposition method

The garnet-type Li_6La_3ZrTaO_(12)(LLZT) solid electrolyte films were fabricated by aerosol deposition(AD)method.Ball-milled LLZT powder with a cubic garnet structure and a particle size of 1-2 urn was used as raw material and deposited directly on a SUS316L or a glass substrate via impact consolidation.As-deposited LLZT film has a cubic garnet structure but contains Li_2CO_3 and La_2Zr_2O_7 phases.SEM observation revealed that the film consists of LLZT particles fractured into submicron size.The impurity phase formation during AD process was caused by the local heating by the collision between LLZT particles and deposition surface and reaction with CO_2.The Li~+ ion conductivity of LLZT film was estimated to be 0.24 × 10~(-5)S cm~(-1) at room temperature.Electronic conductivity of LLZT film was confirmed to be around 10~(-12) S cm~(-1),indicating the dominant Li~+ ion conduction of LLZT film.     

Preparation, microstructure and degradation performance of biomedical magnesium alloy fine wires

With the development of new biodegradable Mg alloy implant devices, the potential applications of biomedical Mg alloy fine wires are realized and explored gradually. In this study, we prepared three kinds of Mg alloy fine wires containing 4 wt% RE(Gd/Y/Nd) and 0.4 wt% Zn with the diameter less than 0.4 μm through casting, hot extruding and multi-pass cold drawing combined with intermediated annealing process. Their microstructures, mechanical and degradation properties were investigated. In comparison with the corresponding as-extruded alloy, the final fine wire has significantly refined grain with an average size of 3–4 μm, and meanwhile shows higher yield strength but lower ductility at room temperature. The degradation tests results and surface morphologies observations indicate that Mg–4Gd–0.4Zn and Mg–4Nd–0.4Zn fine wires have similar good corrosion resistance and the uniform corrosion behavior in SBF solution. By contrast, Mg–4Y–0.4Zn fine wire shows a poor corrosion resistance and the pitting corrosion behavior.     

The enhanced corrosion resistance of UMAO coatings on Mg by silane treatment

The surface silanization was carried out on ultrasonic micro-arc oxidation(UMAO) coatings on pure magnesium using KH550 as silane coupling agent(SCA). The surface morphology, chemical bonds and corrosion resistance of the silane films were investigated by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR) and electrochemical workstation, respectively. The results showed that hybrid coatings were successfully prepared on pure magnesium by UMAO-Na OH(1 mol/L, 2 mol/L, 3 mol/L)-SCA processing. The organic films with Si–O–Mg bonds are helpful for the reduction of the pores in UMAO coatings. The pores decreased with increasing Na OH concentration. Compared with single UMAO treatment, the corrosion potentials(Ecorr) of magnesium plates with UMAO-Na OH(1 mol/L,2 mol/L, 3 mol/L)-SCA treatment increased by 29 m V, 53 m V and 75 m V, respectively, meanwhile the corrosion current density(Icorr) reduced one to two orders of magnitude. It indicated that the corrosion resistance of the coatings was improved by silane treatment.     

A facile and green preparation of durian shell-derived carbon electrodes for electrochemical double-layer capacitors

A facile and green preparation of high surface area activated carbons with mixed microporosity and mesoporosity from durian shell waste is reported in this work. The pore structure and surface chemistry of the parent carbon were modified by the combination of ultrasonication and microwave irradiation techniques. The effects of temperature and time in the ultrasonication treatment and power output and time in the microwave irradiation were studied. The electrochemical performance of carbon electrodes for supercapacitors was tested by cyclic voltammeter (CV) and galvanostatic charge–discharge. The results show that the capacitive energy storage of electrodes is critically dependent on the microporosity and surface chemistry of activated carbons. The highest electrode capacitance in this work was 103.6 F/g that prepared from activated carbon modified at an ultrasonication temperature of 323.15 K for 10 min and microwave power output of 900 W for 10 min.     

Hydrothermal synthesis of AlPO4-5: Effect of precursor gel preparation on the morphology of crystals

This paper reports on the effect of precursor gel preparation on the microstructural formation of aluminophosphate-5 (AlPO4-5) molecular sieves in the hydrothermal synthesis. The morphology of AlPO4-5 crystal changed from sphere to ellipse with two symmetrical craters when the aluminophosphate precursor gel was prepared via dropwise addition of acid and TEA under strong stirring, and continuous stirring overnight during the gel aging process. The results also showed that both of well-crystallized spherical and elliptical AlPO4-5 crystals covered by the fibrous crystals could be hydrothermally synthesized at 150 oC for 4 h or longer. The average particle size of spherical AlPO4-5 samples was about 35–45 mm in diameter, whereas the elliptical AlPO4-5 exhibited approximately 13 mm in width and 15 mm in length.     

Effect of Sr on microstructure and aging behavior of Mg–14Li alloys

The as-cast and as-extruded Mg–14 wt%Li–x Sr ( x=0.14, 0.19, 0.39 wt%) alloys were,respectively, prepared through a simple alloying process and hot extrusion. The effects of Sr addition on microstructure and aging behavior of the Mg–14 wt%Li–xSr alloys were studied. The results indicated that β(Li) and Mg2Sr were the two primary phases in the microstructures of both as-cast and as-extruded Mg–14 wt%Li–xSr alloys. Interestingly, with the increase of Sr content from 0.14 wt% to 0.39 wt%, the grain sizes of the as-cast and as-extruded Mg–14 wt%Li–xSr alloys markedly decreased from 5000mm and 38mm to 330 mm and 22mm respectively, while no obvious changes of the micro-hardness and microstructure of the as-extruded alloys were observed during the aging treatment.     

La2O3–Al2O3 –SiO2 glass-infiltrated 3Y-TZP all-ceramic composite for the dental restora tive application

The 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) powder had three particle size distributions, while the fine one was lower than 100 nm. The 3Y-TZP compact was prepared by dry-pressing under pressures ranged from 10 to 30 MPa and then presintered at 1250°C for 2 h. The matrix dry-pressed under the pressure of 20 MPa had a porosity of 16.7% and could be easily processed by computer aided design and computer aided manufacturing (CAD/CAM), and which had been infiltrated by the La2O3–Al2O3–SiO2 glass at 1200°C for 4 h. The flexural strength and fracture toughness of the composite were 710.7 MPa and 6.51 MPa m^1/2, respectively. The low shrinkage (0.3%) of the composite can satisfy the net-shape fabrication standard. XRD results illustrated that zirconia in the La2O3–Al2O3–SiO2 glass-infiltrated 3Y-TZP all-ceramic composite was mainly in the tetragonal phase. SEM and EDS results indicated that the pores of the matrix were almost filled by the La2O3–Al2O3 –SiO2 glass     

Effect of pickling processes on the microstructure and properties of electroless Ni–P coating on Mg–7.5Li–2Zn–1Y alloy

The electroless plating Ni–P is prepared on the surface of Mg–7.5Li–2Zn–1Y alloys with different pickling processes.The microstructure and properties of Ni–P coating are investigated.The results show that the Ni–P coatings deposited using the different pickling processes have a different high phosphorus content amorphous Ni–P solid solution structure,and the Ni–P coatings exhibit higher hardness.There is higher phosphorus content of Ni–P amorphous coating using 125 g/L Cr O3and 110 ml/L HNO3(w68%)than using 180 g/L Cr O3and 1 g/L KF during pre-treatment,and the coating structure is more compact,and the Ni–P coatings exhibit more excellent adhesion with substrate(Fcup to22 N).The corrosion potential of Ni–P coating is improved and exhibits good corrosion resistance.As a result,Mg-7.5Li-2Zn-1Y alloy is remarkably protected by the Ni–P coating.     

Grain size-dependent electrical resistivity of bulk nanocrystalline Gd metals

The electrical resistivity of the as-consolidated and coarse-grained bulk gadolinium(Gd) metals was studied in the temperature range of 3-315K.The experimental results showed that with decrease in the grain size of Gd grains from micrometer to nanometer range,the room temperature electrical resistivity increased from 209.7 to 333.0 μΩcm,while the electrical resistivity at the low temperature of 3K was found to increase surprisingly from 16.5 to 126.3 μΩcm.The room temperature coefficient resistivity(TCR) values were obtained as 39.2×10-3,5.51×10-3 and 33.7×10-3K-1.The ratios of room temperature to residual resistivity [RRR=ρ(300K)/ρ(3K)] are 2.64,11.0,respectively,for the as-consolidated samples at 280℃ and 700℃ with respect to that of the coarse-grained sample.All results indicate the remarkable influence of the nanostructure on the electrical resistivity of Gd due to the finite size effect and large fraction of grain boundaries.     

Synthesis of dental resins using diatomite and nano-sized SiO2 and TiO2

The mechanical properties of dental composites were improved by porous diatomite and nano-sized silica (OX-50) used as co-fillers.The resin composites,filled with silanized OX-50 and silanized diatomit...     

Experimental and numerical analyses of pure copper during ECFE process as a novel severe plastic deformation method

In this paper,a new severe plastic deformation method called equal channel forward extrusion(ECFE) process has been proposed and investigated by experimental and numerical approaches on the commercial pure copper billets. The experimental results indicated that the magnitudes of yield strength,ultimate tensile strength and Vickers micro-hardness have been markedly improved from 114 MPa,204 MPa and68 HV as the annealed condition to 269 MPa,285 MPa and 126 HV after the fourth pass of ECFE process,respectively. In addition,scanning electron microscopy observation of the samples showed that the average grain size of the as-received state which is about 22 μm has been reduced to 1.4 μm after the final pass. The numerical investigation suggested that although one pass ECFE process fabricates material with the mean effective strain magnitude of about 1,the level of imposed effective plastic strain gradually diminishes from the circumference to the center of the deformed billet.     

Modification performance on 4032 Al alloy by using Al–10Sr master alloys manufactured from different processes

The microstructures and modification performance on 4032 aluminum alloy of the Al–10Sr master alloy wire prepared from "direct reaction-hot extrusion" and the trapezoidal block from "direct reaction" were systemically studied by using optical metallurgical microscope, XRD and SEM. It was found that the preparation processes exhibited a significant effect on the microstructures of the Al–10Sr, which thereby influenced its modification performance. It has been found that when the Al–10Sr alloy wire was used, a desirable modification was obtained after 2 min and reached to the best performance at 60 min, and the optimum Sr addition amount was 0.04–0.06 wt%, and the good modification performance was kept even after 300 min. However, when the Al–10Sr alloy trapezoidal block was used, a desirable modification was started after 30 min and reached to the best performance as long as 120 min, and the optimum Sr addition amount was 0.06–0.08 wt%, and the effective modification period was only180 min. Therefore, comparing with the Al–10Sr alloy trapezoidal block, the Al–10Sr alloy wire had better modification efficiency, which not only reduced the Sr addition amount of about 30%, but also greatly decreased the incubation time and improved the ability of anti-fading.     

Highly dispers ed iron species created on alkali-treated zeolite for ammonia SCR

Alkaline treatment using sodium hydroxide was introduced to obtain a hierarchical pore structure in H-ZSM-5 zeolite.Fe-exchanged zeolite catalysts were prepared by impregnation on the original and alkali-treated zeolites,and were evaluated for NOx reduction by NH3,NO oxidation,and NH3 oxidation reactions.The highly dispersed iron species as active sites can be obtained by controlling the pore structure and particle size of zeolite.Therefore,the Fe/ZSM-5 catalyst treated mildly by sodium hydroxide before iron exchange,which contains amounts of highly dispersed Fe species,obtains over80% NOx conversion at a wide temperature range of 250-500℃.     

Influence of withdrawal rate on the porosity in a third-generation Ni-based single crystal superalloy

The influence of withdrawal rate on the porosity in a third-generation Ni-based single crystal superalloy was investigated by a quantitative evaluation method. The results showed that the withdrawal rate obviously effected on the average area fraction, number and diameter of porosities except their radius ratios. In consideration of the microstructure observation for dendrite arms, an optimized withdrawal rate was obtained with a minimum porosity level as about 125 μm s~(-1). Simultaneously, a threshold value for the acceptance level of porosities might be set as about 0.1% in order to fulfill the requirements for Ni-based single crystal casting in laboratory scale. Finally, the formation reason of porosity was discussed and it was concluded that the feeding for the volume shrinkage of the last solidified eutectic liquids from the residual liquids and the isolating effect of the morphologies of dendrite arms might be two key factors in controlling the porosities level in Ni-based single crystal superalloy.     

Fabrication of fine spongy nanoporous Ag-Au alloys with improved catalysis properties

Fine NP-AgAu(nanoporous AgAu) alloys with spongy structure was fabricated by chemical dealloying from rapidly solidified amorphous precursors Ag_(38.75-x)Cu_(38.75)Si_(22.5)Au_x(x=0, 0.5, 1 and 5). The results indicate that the addition of small content Au in precursor can refine both the ligaments and pores obviously. Among the present components of the precursors, NP-AgAu alloys dealloying from Ag_(37.75)Cu_(38.75)Si_(22.5)Au_1 had the finest spongy structure. The size of pores was 5–10 nm and the grain size of ligaments was 10–20 nm. It also had the highest surface area of 106.83 m~2g~(-1) and the best catalytic activity towards electro-oxidation of formaldehyde with the peak current of 665 mA mg~(-1).