Pore-forming Material Research Articles

Progress in Metal-Supported Axial-Injection Plasma Sprayed Solid Oxide Fuel Cells Using Nanostructured NiO-Y0.15Zr0.85O1.925 Dry Powder Anode Feedstock

A composite NiO-Y0.15Zr0.85O1.925 (YSZ) agglomerated feedstock having nanoscale NiO and YSZ primary particles was used to fabricate anodes having sub-micrometer structure. These anodes were incorporated into two different metal-supported SOFC architectures, which differ in the order of electrode deposition. The composition of the composite Ni-YSZ anodes is controllable by selection of the agglomerate size fraction and standoff distance, while the porosity is controllable by selection of agglomerate size fraction and addition of a sacrificial pore-forming material. A bi-layer anode was fabricated having a total porosity of 33% for the diffusion layer and 23% porosity for the functional layer. A power density of 630 mW/cm2 was obtained at 750 °C in humidified H2 with cells having the bi-layer anode deposited on the metal support. Cells having the cathode deposited on the metal support showed poor performance due to a significant number of vertical cracks through the electrolyte, allowing excessive gas cross-over between the anode and the cathode compartments.

Preparation of Porous Ceramics Using Different Pore-Forming Agents

In this study, porous ceramics having cordierite crystalline phases were made from kaolin, talc and α-alumina at 1200 °C for 1 h. Coal powders and starch were used as pore-forming materials, respectively. Physical and chemical properties and microstructure of two samples were studied. The study results indicate that the pores of starch samples are homogeneous. Compared to coal powders samples, the porosity of starch samples is higher, but the bending strength is lower than that of coal powders samples.

Improved ethanol, acetone and H2 sensing performances of micro-sensors based on loose ZnO nanofibers

Both one-dimensional nanostructures and porous nanostructures are benefit to the sensing enhancement of semiconducting functional materials. The present paper shows an effective route to combining the advantages of these two nanostructures for a novel type of ZnO nanomaterials. Basically, a pore-forming material is employed in an electrospinning method, and the products are characterized by X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The obtained materials are loose ZnO nanofibers, which own both porous and one-dimensional nanostructures. Micro-sensors are fabricated by sputtering and etching techniques, and the as-prepared nanofibers are used as the functional materials in them. The sensors show improved sensing properties both in sensitivity and response-speeds. The sensitivity is enhanced from 4 to 8 and the response time is shortened from 14 to 10 s when the sensors are exposed to 100 μL/L ethanol at 260°C. Similar results are also observed in acetone and H2 sensing tests. These enhancements are based on the one-dimensional and porous nanostructures of the nanofibers.

In vivo study of five porous bioceramic scaffolds implanted in animal muscle

Objective To investigate the in vivo biological performance of 5 porous bioceramic scaffolds,which were bioglass,β-tricalcium phosphate (β-TCP),hydroxyapatite (HA),β-calcium silicate (β-CS) and α-CS,implanted in rabbit dorsal muscle.Methods The 5 porous bioceramic scaffolds were fabricated by adding pore-forming materials and sintering,and then were investigated by X-ray diffraction,porosity mensuration and biomechanics test.The scaffolds were implanted into rabbit dorsal muscle for 4,8,12,16 weeks,respectively.The samples were analyzed by X-ray,Micro-CT,histological analysis,scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The expression of bone morphogenetic protein (BMP-2) and BMP-7 in the muscle in touch with bioceramic scaffolds were also investigated by polymerase chain reaction (PCR).Results The characteristic analysis of 5 scaffolds showed that the sequence of compressive strength was bioglass＞α-CS＞β-CS＞β-TCP＞HA,the sequence of elasticity modulus was α-CS＜β-TCP＜HA＜β-CS＜bioglass.It was confirmed by X-ray,Micro-CT and histological analysis that the sequence of biodegradability was β-CS＞α-CS＞β-TCP＞bioglass＞HA.The histological observation showed no new bone formation in five scaffolds.A Ca-P layer was formed in the surface of bioglass,α-CS and β-CS,which suggested their in vivo bioactivity.After 16 weeks,the expression of BMP-2 and BMP-7 was found only in β-CS.Conclusion The porous calcium silicate scaffold,which was promising for bone tissue engineering,was with good in vivo bioactivity and biodegradability,without in vivo osteoinductivity. Key words: Silicates; Bone morphogenetic proteins; Rabbits

The characteristics and application of grain-slag media in a biological aerated filter (BAF)

Novel filter media-grain slag particles were prepared using waste material-grain slag, clay and pore-forming material with a mass ratio of 3:2:1. Compared with haydite, grain-slag had higher total porosity, larger total surface area and lower bulk and apparent density. Tests of heavy metal elements in lixivium proved that grain-slag were safe for wastewater treatment. In order to ascertain the application of grain-slag, grain-slag and haydite were applied as the media of biological aerated filters (BAF) to treat municipal wastewater in two lab scale upflow BAFs. The results showed that grain-slag reactor brought a relative superiority to haydite reactor in terms of chemical oxygen demand (CODcr) and ammonia nitrogen (NH3-N) removal at the conditions of water temperature ranging from 20°C to 26°C and DO ≥4.00mgL−1 when hydraulic retention time (HRT) ranging from 1h to 5h. In addition, the detection of the amount of hetero bacteria and nitrobacteria of two biological aerated filters in three HRTs also showed that grain-slag medium was more suitable to the attached growth of nitrobacteria, which is helpful to the improvement of nitrification performance in grain-slag BAF. Therefore, grain-slag application in BAF, as a novel process of treating wastes with wastes, provided a promising way in grain slag waste material utilization.

Synthesis of Nitrogen-Doped Mesoporous TiO<sub>2</sub> Film and its Visible Light Photocatalytic Activity

A visible-light-active nitrogen-doped mesoporous TiO2 (N-TiO2) film was synthesized via sol-gel spin-coating technique, using carbon spheres as pore-forming materials. The as-prepared film was characterized by XRD, BET, SEM, XPS and UV-Vis. The N-TiO2 film showed higher photocatalytic activity in the degradation of dye Reactive Brilliant Red X-3B (C.I. reactive red 2) under visible light irradiation compared with smooth TiO2 film and P25 film. The apparent rate constant of the N-TiO2 film was almost 10 times as that of P25 film.

Fabrication and Properties of Al<sub>2</sub>O<sub>3 </sub>Short Fiber Reinforced Aluminium Matrix Composites

The Poly-crystal alumina short fiber reinforcing 2024 matrix composites was produced by the gas pressure infiltration, and a new apparatus has been developed for the infiltration of MMCs by the gas pressure infiltration technique. The reasonable sintering parameter for the preform were determined.The preform was heated at 450°C to remove the organic binder and pore-forming material, and then heated at 1050°C for 2.5h to obtain the comprehensive properties.Scanning electron microscope was used to observe the tensile fracture of Aluminum matrix composites, and the fracture feature of composites produced in different temperature was analyzed. The melting temperature of 2024Al was 800°C and holding time was 20mins; the infiltration gas pressure was 0.5Mpa and holding time was 20s.And then interface reaction is appropriate between the fiber and matrix ,a good performance of composites was produced.

Preparation of large effective specific surface area reticulate porous ceramics by polymeric foam replication process using recoating technique

Large effective specific surface area reticulate porous ceramics (RPC) were fabricated by a polymeric foam replication process using of two-step route (presintering-recoating). The coating slurries used clay as the major material and silica sol etc. as a binder, while the recoating slurries consisted of lower concentration coating slurries and pore-forming materials such as starch or graphite. The solids-content of the recoating slurries which could effect on the porosity and the coating amount of sintered bodies was optimized in our work. Specific surface area and the pore size distribution of the RPC were measured by intrusive mercury curve. Morphological characteristics of the RPC were investigated by SEM. Comparing with the uncoated RPC, the recoated RPC had still highly porosity (80%) and a higher compressive strength. A lot of pores and apertures left on the surface of the sintered RPC’s after those starch/graphite pore-forming materials were burned out, thus lead to a remarkable increase in the specific surface area. The maximal effective specific surface area (ignore the pores size below 10 microns) of the recoated RPC is 0.52 m2/g, as over ten times as the uncoated RPC.

Synthesis and Characterization of Microporous Hydroxyapatite via Hydrothermal Method

Microporous hydroxyapatite crystals were synthesized from calcium nitrate and phosphorus oxide in water/ethanol solution by hydrothermal method without any pore-forming material and template. The influences of several synthetic parameters have been also analyzed in order to obtain microporous materials with well crystallized and homogeneous in shape. The composition and microstructure of the grown crystals were analyzed by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric analysis (TG), differential thermal analysis (DTA), and transmission electron microscopy (TEM). The results show that perfect hydroxyapatite crystals with hexagonal-dipyramidal phase (70 × 167nm) and micropores (1–2 nm) were obtained in V(water):V(ethanol) = 1:1 at 160°C for 8 h, the hole density was about 3 × 109/cm2.

Preparation of homogeneous nanoporous La 0.6Ca 0.4CoO 3 for bi-functional catalysis in an alkaline electrolyte

Well-dispersed nanoporous La 0.6Ca 0.4CoO 3 catalyst for metal–air batteries was synthesized by a modified amorphous citrate precursor method using Vulcan XC-72R as a pore-forming material. Nanostructural perovskite La 0.6Ca 0.4CoO 3 with a specific surface area of over 210 m 2/g was obtained at 650 °C in air. The electrochemical behaviors of the as-prepared La 0.6Ca 0.4CoO 3 catalysts were studied on classical bilayer gas diffusion electrodes. Compared with the traditional amorphous citrate precursor method, the perovskite La 0.6Ca 0.4CoO 3 prepared by this modified technique illustrated higher electrocatalytic activity mainly due to the high surface area and the novel nanostructure, which would provide potential applications in metal–air batteries and fuel cells.

The Characteristics and Application of Water Quenched Slag Particles (WQSP) as Filter Media

Novel filter media-water quenched slag particles (WQSP) were prepared using waste material- Water quenched slag, clay and pore-forming material with a mass ratio of 3:2:1. Compared with haydite, WQSP had higher total porosity, larger total surface area and lower bulk and apparent density. Tests of heavy metal elements in lixivium proved that SGSP were safe for wastewater treatment. In order to ascertain the application of WQSP ，WQSP and haydite were applied as the media of biological aerated filters (BAF) to treat municipal wastewater in two lab scale upflow BAFs. The results showed that WQSP reactor brought a relative superiority to haydite reactor in terms of chemical oxygen demand (CODcr) and ammonia nitrogen (NH3-N) removal at the conditions of water temperature ranging from 200C to 260C and DO ≥4.00 mg·L-1. Therefore, WQSP application, as a novel process of treating wastes with wastes, provided a promising way in water quenched slag utilization.

A pilot human pharmacokinetic study and influence of formulation factors on orodispersible tablet incorporating meloxicam solid dispersion using factorial design

Meloxicam (MLX) suffers from poor aqueous solubility leading to slow absorption following oral administration; hence, immediate release MLX tablet is unsuitable in the treatment of acute pain. This study aims to overcome such a drawback by increasing MLX solubility and dissolution using PEG solid dispersion (SD), then, to investigate the feasibility of incorporating the SD into orodispersible tablets (ODTs). A 23 full factorial design was employed to investigate the influence of three formulation variables on MLX ODTs. The selected factors: camphor (X1) as pore-forming material, and croscarmellose sodium (X2) as superdisintegrant, showed significant positive influence, while PEG content (X3) was proved to negatively affect both disintegration and wetting times. In addition, isomalt increased disintegration and wetting times when compared to mannitol as diluents. The pharmacokinetic assessment of the optimum ODT formulation in healthy human subjects proved that the faster MLX dissolution by using PEG solid dispersion at pH 6.8 resulted in more rapid absorption of MLX. The rate of absorption of MLX from ODT was significantly faster (p = 0.030) with a significantly higher peak plasma concentration (P = 0.037) when compared to the marketed immediate release MLX tablet with a mean oral disintegration time of 17 ± 3 s.

Preparation and Characterization of Porous Ceramic Support

The porous ceramic support was prepared from cordierite by adjusting the phase composition, grain size of aggregate, additions of pore-forming material and binder. The porous ceramic support had excellent chemical stability and relative high strength with a porosity of 48％and pore size of 128μm. Factors that affected the properties of the support material were analyzed. The pore size of the porous ceramic support was directly proportional to the grain size of the aggregate around firing temperature. The strength of the support material increases with a rise in amount of the binder and firing temperature. The porosity of the support material increases while the strength decreases with a rise in amount of the pore-forming agent.

Spin-coating derived LSM-SDC films with uniform pore structure

LSM and SDC powders were synthesized by glycine-nitrates technique and LSM-SDC composite porous films are deposited by means of spin-coating process using ethyl cellulose as pore-forming material. According to the surface morphology and microstructure of cathode films identified with scanning electron microscopy (SEM), as the content of ethyl cellulose in slurry was increased, the pore distribution in films becomes more uniform and the pore size is getting smaller. It was found that while the slurry contains 10 wt.% ethyl cellulose and 90 wt.% LSM-SDC composite powders, the cathode film has a fine structure, which has smooth surface without cracks, uniform pore distribution, suitable pore size and three-dimensioned interconnected structure.

Cathode structure optimization for air-breathing DMFC by application of pore-forming agents

The cathode catalyst layer in an air-breathing, direct methanol fuel cell (DMFC) has been improved by addition of pore-forming materials, such as ammonium carbonate and ammonium hydrocarbonate. These construct an effective electrode pore structure. During fabrication of the membrane electrode assembly (MEA), these pore-formers decompose, increase the BET surface area of the electrodes, and form additional porosity. Ammonium carbonate predominantly produces macropores, while ammonium hydrocarbonate is effective for mesopores. This results in an increase in electrochemical active area and catalyst utilization. The higher open-circuit voltage with MEAs prepared with pore-forming material indicates improved air transfer through the cathode. The power density is increased by 30–40% with the employment of the pore-forming materials.

Energetic state and condensation of gas molecules in pores

In this work, the effect of the energetic state of gas molecules in pores on a condensation process in the pore was analyzed. An equation of state for real gases was proposed to consider the formation of a liquid in an explicit form; this equation is applicable to describe the state of a gas both outside and within a pore. It was demonstrated that the difference of the energy of gas molecules in a pore from the energy of these molecules in a surrounding space and the corresponding difference between pressures in these volumes have a determining effect on the state of the gas in the pore to change the conditions of condensation in this pore. The effects of these factors were taken into consideration in the derived equations of state. Based on these equations, it was demonstrated that the condensation of a gas in a pore can come into play at outer pressures lower than the saturation pressure in the surrounding space or be lacking when a saturation pressure was reached in the outer volume. The effects of pore radius and volume, as well as parameters that characterize the energetic interaction of gas-phase molecules with the atoms of a pore-forming material, were considered.

Micro-Pore Structure and Mechanical Properties of High Temperature Self-Lubricating Biomimetic TiC/FeCrWMoV Cermets

A new cermet sinter with sweat-gland micro-pore structure has been developed by powder metallurgy technology in vacuum. The effects of the pore-forming materials on micro-pore structure and Y2O3 additions as well mechanical properties of TiC/FeCrWMoV cermets were investigated. Some typical sweat-gland micro-pores were formed while compound additives TiH2 and CaCO3 adding into the sinter matrix. The porosity of the cermet sinters changes from 20% to 28% with the compound additives from 6% to 8%, and the micro-pores of sinters exist a regularized and interpenetrated network structure just like human’s sweat-gland one and obeying to Rayleigh Distribution. As such the sinters could be easily infiltrated with high-temperature solid lubricant. For improving the property of the ceramet sinter, the elements Y2O3 of 0.6～0.8% (vol. fraction ) was also added into the sinter matrix and its effect on the sinter has been also discussed .

PROPERTIES AND MANUFACTURE OF CERAMIC SINTER WITH SWEAT-GLAND PORE-STRUCTURE

A new ceramic sinter with sweat-gland micro pore-structure in which TiC-Fe-W-Cr-Mo-V powder is as the basic material and TiH2 or CaCO3 are as composite pore-forming materials and Al2O3 is as dispersal particles, has been developed by liquid phase sintering. The effects of particles size of TiC-Fe-W-Cr-Mo-V powder, composites of pore-forming materials and sintering craft on the porosity, pore-structure, dimension, distribution and encapsulating properties of cermet sinters have been investigated by a series of experiments. The results show that the new cermet sinter, moulded by 600 MPa pressure, at sintering temperature 1230℃ for 60 min, has a typical sweat-gland micro pore-structure which has the characteristics of both homogeneous and connecting each other. Furthermore, ideal spherical shape and distribution of the pore-diameter, as well as mechanical strength, are also be discussed. It is obvious that the sinter, which the pore-diameter obeying Rayleigh Distribution, can be used as high-temperature self-lubricating materials after filling solid lubricants into it.

Enhancement of the heat and mass transfer in compact zeolite layers

Heat and mass transfer during the adsorption of water on zeolite has been studied both theoretically and experimentally. A dynamic simulation model of a zeolite layer has been developed to estimate the predominant transport resistances and calculations were carried out to assist the simultaneous experimental investigations. On one hand, a metallic matrix was added to the compact zeolite layer to improve the heat transfer. On the other hand, pore-forming materials such as melamine or tartaric acid were used. These organic components are removed during drying of the zeolite so that the mass transfer inside the zeolite is significantly enhanced compared to a granulated zeolite bed. The experimental investigations show that the theoretically deduced possibilities of improving the adsorption process can be realized in the manufactured zeolites. The investigations described here are of interest for the development of adsorption heat pumps. Due to the thermodynamic characteristics the adsorption system zeolite-water is a promising working pair for this application. The investigations show that the main shortcoming of these machines, the thermal output, can be increased significantly.

Preparation of bimodal porous mullite ceramics

Bimodal porous ceramics were prepared based on the needle-like mullite crystals, by leaching the glass matrix of the calcined body of the kaolin and transition metal oxide systems mixed with coal powder or polymethylmethacrylate beads as a pore-forming material. Small and large pores in the bimodal porous ceramics were in the range of 0.06–0.5 and 3–7 Μm, respectively. The small pores originated from gaps between the needle-like crystals, while the large ones originated from the pore formers. However, the large pores were suggested to be ink-bottle type in shape, because the measured size was much smaller by approximately an order of magnitude than the diameter of the pore former. In every case, the total and large pore volumes agreed well with those calculated based on the density and composition of the starting materials and the intrinsic porosity of the mullite ceramics.