Porous Properties of Nano-fibriform Silica from Natural Chrysotile

With the TEM and physical gas adsorption techniques, porous properties of nano-ribriform silica （MLD： 92.73%） from natural chrysotile are studied in this paper. The results indicate that porous nano-fibriform silica results from brucite octahedral sheets of nature chrysotile dissolved completely and Si-O tetrahedral sheets collapsed by acid leaching. Its length is at a micron or nanometer scale. There are two types of pores： pores among neighboring fibers and pores in nanoriber. These pores （less than 6.5 nm in diameter, mostly 2.1 nm and 3.8 nm） all belong to mesopores. The pores in fibers consist of those among SiO2 particles, those among aggregates, remnant nanotubes and capillary tubes. Nanoribriform silica proves better than the traditional silica as a carrier of catalyzer and a filler for reinforce rubber and plastics.

FORMATION AND PROPERTIES 0F POROUS SILICON LAYER ON HEAVILY DOPED n-Si

The anodic voltammetric curves of heavily doped n-Si in HF solution, on which three different regions have emerged, and were plotted, A porous silicon layer with fine morphology was formed in linear region.

Polarization properties of porous anodic alumina with Y-branched Cu nanowires

Porous anodic alumina （PAA） templates with branch structure are fabricated by the two-step anodic oxidation processes, and then the Y-branched Cu nanowires are synthesized in the templates using an alternating current （AC） deposition method. We observe the morphology image of the samples by scanning electron microscopy （SEM）, and measure the transmission spectrum and the polarization spectrum of the samples by the spectrophotometer. The results show that PAA films with Y-branched Cu nanowires have better transmittance in the near infrared region. An extinction ratio of 15 - 18 dB and an insertion loss of 0.1 - 0.4 dB are obtained in this region. Therefore PAA with Y-branched Cu nanowires can be used as a near-infrared micropolarizer, and this kind of micropolarizer would have a promising future in the field of photoelectricity integration.

Fabrication and Properties of Porous Si_3N_4 Ceramic with High Porosity

A novel process combining oxidation-bonding and sintering was developed to fabricate porous Si3N4 ceramic with high porosity. After sintering at 1800℃, the SiO2 in porous Si3N4 ceramic transforms into Si2N2O because of the reaction of SiO2 and Si3N4 . Due to the reaction of SiO2 and carbon, the porosity of porous Si3N4 ceramic increases obviously from 40.2% to 76.8% with the weight decreasing by 35.6%. As the porosity increases, the dielectric constant and loss of the porous Si3N4 ceramic decrease obviously from 3.08 to 1.61 and from 3.70×10（-3） to 0.74×10（-3） , but due to the production of Si2N2O whose mechanical properties are much higher than SiO2 and the increase of the bonding strength among Si3N4 particles, the flexural strength and the fracture toughness of the porous Si3N4 ceramic decrease from 55 to 39 MPa and from 0.7 to 0.5 MPa·m（1/2） , respectively, but its Vickers hardness increases from 1.2 to 1.3 GPa.

Synthesis and Application of a Zeolite-containing Composite Material Made from Spent FCC Catalyst

Novel composite material with a wide pore distribution was synthesized by an in situ technique using spent FCC catalyst as raw material. The characterization results indicated that the composite material contained 56.7% of zeolite Y and exhibited a much larger specific surface area and pore volume as well as strong hydrothermal stability. Fluid catalytic cracking(FCC) catalyst was prepared based on the composite material. The results indicated that the as-prepared catalyst possessed a unique pore structure that was advantageous to the diffusion-controlled reactions. In addition, the attrition resistance, activity and hydrothermal stability of the studied catalyst were superior to those of the reference catalyst. The catalyst also exhibited excellent nickel and vanadium passivation performance, strong bottoms upgrading selectivity, and better gasoline and coke selectivity. In comparison to the reference catalyst, the yields of the gasoline and light oil increased by 1.61 and 1.31 percentage points, respectively, and the coke yield decreased by 0.22 percentage points, and the olefin content in the produced gasoline reduced by 2.51 percentage points, with the research octane number increased by 0.7 unit.

Electron Beam Melted Beta-type Ti–24Nb–4Zr–8Sn Porous Structures With High Strength-to-Modulus Ratio

Electron beam melting （EBM） has been used to manufacture β-type Ti-24Nb-4Zr-8Sn porous compo- nents with 70% porosity, EBM-produced components have favorable structural features （i.e. smooth strut surfaces, fewer defects） and an （α ＋ β）-type microstructure, similar to that subjected to aging treat- ment. EBM-produced components exhibit more than twice the strength-to-modulus ratio of porous Ti- 6A1-4V components having the same porosity. The processing-microstructure-property relationship and deformation behavior of EBM-produced components are discussed in detail. Such porous titanium com- ponents composed of non-toxic elements and having high strength-to-modulus ratio are highly attractive for biomedical applications.

MgO-based adsorbents for CO2 adsorption:Influence of structural and textural properties on the CO_2 adsorption performance

A series of MgO-based adsorbents were prepared through solution–combustion synthesis and ball-milling process.The prepared MgO-based powders were characterized using X-ray diffraction,scanning electron microscopy,N_2 physisorption measurements,and employed as potential adsorbents for CO_2 adsorption.The influence of structural and textural properties of these adsorbents over the CO_2 adsorption behaviour was also investigated.The results showed that MgO-based products prepared by solution–combustion and ball-milling processes,were highly porous,fluffy,nanocrystalline structures in nature,which are unique physico-chemical properties that significantly contribute to enhance their CO_2 adsorption.It was found that the MgO synthesized by solution combustion process,using a molar ratio of urea to magnesium nitrate（2：1）,and treated by ball-milling during 2.5 hr（MgO-BM2.5h）,exhibited the maximum CO_2 adsorption capacity of 1.611 mmol/g at 25℃ and 1 atm,mainly via chemisorption.The CO_2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area,total pore volume,pore size distribution and crystallinity.The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO_2adsorption–desorption times,without any significant loss of performance,that supports the potential of MgO-based adsorbent.The results confirmed that the special features of MgO prepared by solution–combustion and treated by ball-milling during 2.5 hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO_2 capture technologies.

Comparison between oxide-reduced and water-atomized copper powders used in making sintered wicks of heat pipe

Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced （OR） powders were compared with one from water-atomized （WA） powder. The green specimens were sintered at temperatures from 800 to 1000 ℃ in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR - 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.