7 limited to specific applications with regards to either the material being dried or the particular drying regime or mechanism at work. The lack of carefully obtained experimental data, primarily due to the often complicated nature of the process and the difficulty of making the necessary detailed measurements, is currently hampering the development of the model for the drying process in membranefabrication. It is quite possible that perhaps the numerical predictions are almost as reliable as experimental data. Hence, the motivation of this study is devoted to develop a tool to simulate drying behaviour of ceramic materials and subsequently allow it to be extended to the fabrication of ceramic membrane. Furthermore, the proposed model is enhanced to accommodate an improved intermittent convective drying technique.
This article presents a fully coupled heat and mass transfer model for convective drying of ceramic porous material. A two dimensional mathematical model that coupled mass, heat and gas transfer was developed and integrated with finite element method and the backward difference method to solve the spatial discretization and temporal discretization of the governing equations respectively. The numerical was computed using Skyline solver to capture highly nonlinear and transient process. Two different meshes (coarse and fine) were applied for the rectangular domain as a representative of the drying object. Results show two typical periods during drying namely the constant rate period (CRP) and falling rate period (FRP) which demonstrated a very small difference between both meshes. However, computational time was increased significantly for the finer mesh as compared to coarser mesh due to their high computational complexity. Thus, we can deduce that this model is sufficient to describe the mechanisms controlling the drying process in membranefabrication.
of the PDMS-CNT membrane. During the experiments, initially, the surface charge of the membrane was high, since both the low CNT diameter and high surface charge of the membrane contributed to the high salt rejection of the membrane.The salt rejection was decreased to 97% from 99% in first 10 mins due to concentration polarization but after 10 mins the salt rejection stabilized at 97% and it was constant for remaining time period. After 60 minutes of filtration, concentration polarization reduced the salt rejection contributed by the surface charge of the membrane, as evident from Fig. 7, wherein the experimental results are in agreement with the results reported by Schrott et al. .
Carbon nanomaterials such as fullerenes, graphene oxide, and carbon nanotubes also have excellent potential for water treatment membrane technology because of their antimicrobial properties. Fullerenes are currently mostly recognized for their use in biomedical applications while the other carbon nanomaterials mentioned above have proven their efficacy for membrane improvement. Multi-walled carbon nanotubes (MWNTs) generally exhibit less antimicrobial activity than single-walled carbon nanotubes because of their smaller diameters . However, SWNTs appear to perform with reduced antimicrobial capacity when embedded within a polymeric membrane: a study by Zhao et al. suggests that this reduction is due to the polymer wrapping . Furthermore, Kang et al.  have suggested that the size of carbon nanotubes (CNTs) is a key factor governing their antibacterial effects. This suggests that the main CNT- cytotoxicity mechanism is the cell membrane damage by direct contact with CNTs. Evidence also suggests that generation of oxidative stress can trigger CNTs’ toxicity to microorganisms . Hu et al. have confirmed the antimicrobial activities of graphene oxide and reduced graphene oxide , though to the best of our knowledge, these materials have not been used in any membranes specifically for antimicrobial uses. However, they have, very recently, been used in polymeric membranes to dramatically enhance permeability, hydrophilicity, anti-fouling, selectivity, and mechanical strength [135, 136].
Dr Naznin Sultana was awarded PhD in 2010 at The University of Hong Kong. She is currently serving as an academic staff in Universiti Teknologi Malaysia. She was registered as a Chartered Scientist (CSci) in 2012 by Science Council, UK and as a Chartered Engineer (CEng) in 2014 from Engineering Council, UK. She has interests in both fundamental science and applied research and she has received a number of research grants from Ministry of Higher Education, Malaysia. Her research interests include biomaterials, tissue engineering, fabrication of scaffolds for tissue engineering, cell-biomaterials interactions and surface modification. She has given many international conference presentations for her research work in The Netherlands, Belgium, Hong Kong etc. She has authored a number of technical papers for her research and author of three books. Hui Chung Chang is a post-graduate research student in the Department of Clinical Sciences, Universiti Teknologi Malaysia.
The CA polymer concentrations, TiO 2 concentrations and PVA concentrations are highly influential process variables on membrane performance, especially flux. Based on the experimental results shown in Fig. 9, generally the higher the CA concentration is resulting in lower total flux. The highest total flux value was shown by the M1 membrane with a 14 wt% CA concentration at 2.56 L × m −2 × h −1 × bar −1 then decreased drastically to 0.61 L × m −2 × h −1 × bar −1 with increasing CA concentration to 16 %. While the increase in CA con- centration to 18 % and 20 %, the total reduction of total flux is relatively small ie to 0.54 and 0.2 L × m −2 × h −1 × bar −1 . This phe- nomenon occurs because the membrane with a concentra- tion of CA 14 % swells with the largest volume ratio com- pared to the concentration of 16 %, 18 %, and 20 %. This swelling causes the membrane pore to widen so that the total flux rate increases. In the addition of TiO 2 nano-filler, as seen in Fig. 9 the higher concentration of nano TiO 2 the higher total flux is obtained. This is due to the addition of nanoparticles during membranefabrication prevents the for- mation of clogged pores, other than that the nano-particles also keep the membrane from the compaction caused by pressure driven over the membrane . Membrane coating using PVA gives an effect inversely with the total flux value, the higher of PVA concentration used as the coating agent the flux value decreases significantly. At PVA concentrations of 2 %, 3 %, 4 %, and 5 % the total flux values were 0.60, 0.48, 0.35, and 0.19 L × m −2 × h −1 × bar −1 , respectively. The higher the PVA concentration as a coating material the thicker the layer is formed; this will increase membrane hydrophilic- ity (as shown in Table 5) which also increases increase the resistance for eugenol to pass through the membrane since eugenol itself is considered as hydrophobic substance, this is in accordance with the results shown in Fig. 9.
type of nano-composite membranes, nanomaterials are placed on surface of a substrate. In fact, these method is membrane structure modification in terms of improving the membrane hydrophilicity, pore size, density, surface charge, roughness and enhancement of membrane anti-fouling characteristics. The latter process of membranefabrication (the fourth), can be used for a variety of membranes, due to the least effect on the main membrane structure, so they have the potential of commercial application for existing membranes. In this type, nano-composite can be placed on the membrane surface via self-assembly, electrostatic attraction, coating/deposition, layer-by-layer assembly ,adsorption- reduction, and chemical grafting methods . 15,16
A novel thulium(III) membrane sensor showing a Nernstian response of 20.4±0.3 mV per decade of thulium concentration in the concentration and pH ranges of 1.0×10 -6 to 1.0×10 -2 mol L -1 and 3.4-8.6 respectively is prepared based on the incorporation of 1,1'-(1,4-butanediyl)bis(imidazole) (BYI) into a polymeric membrane sensor. The sensor had a satisfactory selectivity behavior with respect to alkaline, alkaline earth, transition and heavy metal ions and was successfully used in the determination of the fluoride ion in two mouth wash preparations.
Sensor with optimized membrane composition displayed enhanced selectivity, stability, fast and linear response in a wide concentration range of yttrium (III) ion. Also the proposed electrode has been evaluated by its application in the determination of fluoride in mouthwash solution and toothpaste.
A long list of advantages to base materials such as the flexibility and process ability of polymer, as well as the selectivity and thermal stability of the inorganic fillers are contributed from the aforementioned properties. By adding inorganic nanofillers, it may affect the membrane cell in two ways: 1) the uniform nanosized distribution of inorganic filler particles produces a winding diffusion pathway which can hinder the fuel from transferring into the nanocomposite membrane, and 2) the complete morphological structure allows more cations to be mobile and available for conduction . Inorganic fillers have decreased the cluster size of the parent polymer, thus leading to a complete exfoliated morphology structure (referring to 2). These exfoliated structures would acquire the results mentioned by narrowing the size of both ion clusters and some well-distributed inorganic fillers in the nanocomposite membrane, simultaneously increasing proton conductivity of the referred membrane . According to Jaafar et al. , the loading effect of inorganic filler also plays a role in determining the performance of proton conductivity. Moreover, the smaller the size of particles, the larger the surface area of dispersed nanosized particles in a polymer matrix, and therefore a decrease in the degree of crystallinity of polymer segments. In fact, this phenomenon contributes to the larger ionic mobility that eventually increased proton conduction [5, 6].
Iran). The obtained homogeneous solutions were cast onto clean and dry glass plates using a casting knife with a constant thickness of 150 µm. Then, they were dipped into deionized water as non-solvent without prior evaporation time. After exchanging the solvent and non-solvent and precipitation step, membranes were formed. Then they were kept in new containers with fresh deionized water for one day to remove any soluble components in the membrane structures. The membranes were dried between two filter paper sheets at room temperature (25±2 °C) for one day before use. The composition of the used casting solutions is given in Table 1.
high contact angle of 141.0° is observed for this composite fiber which shows the higher hydrophobic nature of the membrane. The prepared polymer composite membrane was soaked in the electrolyte solution and used as polymer electrolyte. Employing the polymer electrolyte, DSSCs were fabricated successfully and their photovoltaic performances were evaluated. The solar-to-light electricity conversion efficiency of the quasi-solid-state solar cells with the electrospun PVdF-PAN-V 2 O 5
In this research, process asymmetric polyetherimide hollow fiber membranes using ethanol (0, 2 and 4 wt%) as non-solvent additive in the polymer dope via phase inversion method were fabricated. Aqueous solution of 1-methyl-2-pyrrolidine (NMP) (90%) was applied as a bore fluid to avoid inner skin layer formation and water was used as the external coagulant. The morphology of fabricated membranes was examined using field emission scanning electron microscope (FESEM). A gas permeation test was conducted using Nitrogen. Fabricated membranes were characterized in terms of pore size, critical water entry pressure, water contact angle and collapsing pressure. The performance of fabricated membranes for carbon dioxide stripping from monoethanolamine solution using a gas - liquid membrane contactor system was studied. The results showed that carbon dioxide stripping flux and efficiency increased by increasing liquid velocity. Also, enhancement of stripping flux by increasing gas velocity was negligible. By increasing MEA solution temperature, stripping flux increased; therefore, liquid phase temperature is a key parameter which needs to be controlled.
Membrane fouling is one of the main challenges encountered in ultra ﬁ ltration (UF) processes and the use of nanoparticles for the improvement of UF performance is a recent trend in membrane technology. In this study, in order to improve surface characteristics of polyethersulfone (PES)-based membranes for greater resistance against biofouling, PES was incorporated with a new type of nanocomposite (NC) in which the NC could be synthesized by blending acid functionalized multiwalled carbon nanotubes (f- MWCNT) with polyvinylpyrrolidone (PVP) in dimethylformamide (DMF). The chemistry of the NCs embedded within the PES membrane matrix was analysed by FTIR, whereas the fabricated membranes were characterized by FESEM, contact angle, water absorption tests, surface pro ﬁ le studies and their ﬁ ltration performances with respect to pure water permeation, antifouling resistance against proteins and ﬂ ux recovery rate. The results revealed that, compared to the pristine PES membrane, the antifouling ability of the PES membrane incorporated with f-MWCNT/PVP NC is greater, recording 81.7% ﬂ ux recovery and 80.2% total resistance (>76% were reversible one). The protein separation results indicated that, the NCs based membrane was able to reject 93.4%, 74.7%, 59.4% and 28.5% for bovine serum albumin (66 kDa), pepsin (34.6 kDa), trypsin (20 kDa) and (14.6 kDa), respectively.
Asymmetric membrane-controlled porosity osmotic pumps of cellulose acetate with different pore forming agents such as glycerol, polyethylene glycol and dibutyl phthalate, were fabricated and studied for osmotic release behavior from the system. The effects of various pore-forming agents on the physical characteristics of the polymer fi lm like tensile strength, weight variation, wall thickness, surface area, porosity and void volume were studied as a function of pore forming agent. The asymmetric membrane capsules were fabricated by dip-coating process using stainless steel mold pins of the shape of capsule body and cap and were evaluated for in situ formation of delivery pores. The effect of pore forming agents on the porosity of asymmetric membrane was characterized by scanning electron microscopy, and also by void volume determination of each membrane. Dye-test revealed that the fabricated systems followed osmotic release. Scanning electron microscopy revealed that the porosity depends upon the concentration and type of pore forming agent used. However no signifi cant effect on the thickness and weight variation of asymmetric membrane capsule were observed, but the tensile strength of the fi lm varied with the concentration and type of pore forming agent used. Film with polyethylene glycol-400 as pore forming agent exhibited good tensile strength. Key words: Asymmetric membrane, cellulose acetate, controlled porosity, dye-test, fi lm, glycerol
1. The CS/Alg PEMCMs were fabricated by depositing polycation and polyanion alternatively onto the hydrolyzed PAN substrate. The following steps were successively carried out: (1) A 1-wt% CS solution was poured onto the hydrolyzed PAN substrate which had been located in a Busher channel under a reduced pressure, excessive CS solution was removed from the Busher channel after 5 min, and then dried completely. (2) After the drying of CS layer, a 1-wt% Alg solution was introduced into the Busher channel under the same condition as the deposition of CS solution above. When the Alg layer was dried, it was rinsed using de-ionized water, and then dried completely before next deposition. (3) Steps (1) and (2) were repeated till the pre-determined deposition cycles were attained. The layer number of n and n+0.5 suggested the CS and Alg layer were on the top surface of the composite membrane, respectively. The resulting PEMCMs are denoted as (CS/Alg) n , or (CS/Alg) n+0.5 , and the subscript n or n+0.5 means the number of
To-date various materials have been employed to produce micro- and nano- pores, including silicon nitride,[22, 23] glass, aluminum oxide, graphene, [26-28] and track etched polymer foils,[29, 30] using a range of fabrication methodologies, typically involving electron beam or focused ion beam (FIB) milling. The length of the pore is often an important consideration, for example for sequencing of long chain molecules such as DNA, single-base discrimination requires high spatial resolution that can be provided by low aspect ratio pores, such as atomically thin graphene.[26, 27] In contrast, investigation of pore- particle translocation dynamics is suited to pores where the length is greater than that of the analyte to facilitate enhanced time resolution and longer event signals.[32, 33] Consideration of the platform material and fabrication methodology is therefore crucial to fabricate pores of appropriate dimensions for analyte detection.
Abstract:-Integrated circuits are complex, containing both active and passive components that are manufactured on a single crystal chip of silicon and interconnected by wires. Chip sizes may vary from 2 mm to 800 mm. Integrated circuits contain insulating, semiconducting and conduction regions. These regions are combined in such a way to produce various electronic components like diode, transistor, MOSFET etc. Day by day I.C complexity has increased from small scale integration (SSI), to medium scale integration (MSI), to large scale integration (LSI), to very large scale integration (VLSI). The fabrication of I.C depends on material, process and design principals which form a highly developed semiconductor technology. Production of integrated circuit is a multistep sequential process like chemical cleaning, oxidation, etching, diffusion, photolithography etc. NMOS, CMOS, bipolar and integrated injection logic bipolar are major and complex I.C technologies. In this paper I explain the basic processing steps of forming number of PN Junction diodes on a single inch circular silicon wafer.
2. 3. 1. Morphological Studies Cross sectional structures of the prepared membranes were monitored using scanning electron microscope (SEM, Philips, Model XL30, and The Netherlands). Before scanning the samples by SEM apparatus, the samples were frozen in liquid nitrogen and fractured. After sputtering with gold, they were observed by the electron microscope. Also for the evaluation of membrane roughness, 3D image metrology software was used. 2. 3. 2. Water Content and Contact Angle The water content was measured as the weight difference between the dried membranes and swollen ones. The wet membranes were weighed initially (OHAUS, Pioneer™, readability: 10 −4 g, OHAUS Corp., USA) and
properties make it an alternative to well-known platinum or rhodium, but its cost is only 15% of that of platinum or rhodium. Due to this, Ru plays an important role in relevant applications. Ru electroplating processes have been developed rapidly for more than ten years in the finishing industry and chemical engineering . Several kinds of non-aqueous (aqueous) electrolytes and fused salt baths have been built for the electrodeposition of Ru. Typical Ru plating electrolytes can be found in several references [7,8]. Compared with electroplating, electroless plating (or chemical plating) has many advantages. It does not require an external Direct Current (DC) power supply. It is available on a variety of different substrates, such as metals, non- metallic, semiconductor and other materials. For fabrication of Pd-based membranes, it is a plating method for dense film with less pin-holes and cracks. What is more, the technology is controllable for uniform membrane coating on large-scale supports with different industrial geometries. Little information is available on electroless plating of thin dense Palladium- Ruthenium (Pd-Ru) membranes [5,6], especially on the electroless deposition of Ruthenium (Ru).