Fabrication of yttria stabilized zirconia coatings by a novel slurry method

By adopting a ‘bricks and mortar’ approach, yttria stabilized zirconia (YSZ) coatings were produced on Fecralloy substrates by a novel slurry method. The slurry contained large preformed particles of 10–60 μm, as the ‘bricks’, and concentrated nano-particle slurry, as the ‘mortar’. Green coatings were prepared by spreading the slurry on substrates. Then sintering at 1200 °C was carried out to produce coatings with grain size up to 200 nm. The presence of larger preformed particles hindered the shrinkage of the coatings during drying and sintering. It was observed that the ‘mortar’ could form inter-preformed particle ‘bridging’, an underlying mechanism for the formation of ‘cemented’ preformed particle network. By using different preformed particles, different micro-architectures were obtained and reduced thermal diffusivities were achieved. The microstructure and density of the coatings can also be modified by infiltration of the nano-slurry.     

Synthesis of c-axis preferred orientation ZnO:Al transparent conductive thin films using a novel solvent method

Transparent aluminum doped zinc oxide (ZnO:Al, AZO) conducting thin films with a high-preferential c-axis orientation were synthesized using a new sol-gel formula. The films were deposited using a spin-coating route onto borosilicate glass substrates. We used propylene glycol methyl ether (PGME) as the solvent in place of ethylene glycol monomethyl ether (EGME), which is commonly used because it is easier to deposit onto the substrates. PGME is also superior in terms of health and safety. PGME solvent does not need to settle for several days before use and can be spin-coated as soon as the raw material and solvent are mixed. The effects of this novel solvent on the structural, morphological, electrical and optical properties are discussed using XRD, SEM, a four-point probe and UV-VIS spectrophotometry. It was found that the films produced with PGME showed a high-preferential c-axis orientation and compact microstructure in comparison films produced using EGME. The electrical resistivity of AZO thin films produced with PGME solvent was lowered to 3.474 × 10^− 3Ω cm after annealing in 95 N₂/5H₂ atmosphere. In addition, the optical transmittances of AZO thin films on glass plates were higher than 90% in the visible wavelength region.     

Performance of low pH biofilters treating a paint solvent mixture: continuous and intermittent loading

Two biofilters packed with a reticulated polyurethane foam medium were inoculated with a compost-derived enrichment culture grown under acidic conditions (pH 3.0) and then operated over a period lasting 63 days. Both biofilters were supplied with a humidified gas stream containing a five-component mixture of acetone, methyl ethyl ketone, toluene, ethylbenzene, and p-xylene at a total VOC loading rate 80.3 gm(-3)h(-1) to simulate treatment of air emissions resulting from manufacture of reformulated paint. One biofilter was operated under continuous loading conditions and the other received intermittent loading with contaminants supplied only 8 h/day. Nutrient solution with pH 3.0 was supplied approximately once per week to provide nitrogen and other nutrients. Data are presented which demonstrate that undefined mixed cultures acclimated at low pH can successfully treat paint solvent mixtures in biofilters. The biofilter receiving continuous loading reached high overall removal efficiency (greater than 90% overall removal) 3 weeks after startup, and performance increased over time reaching overall removal in the range of 97-99% after 50 days. Performance of the intermittently loaded biofilter developed more slowly, requiring 6 weeks to stabilize at an overall removal efficiency in excess of 90%. In both biofilters, ketone components were more rapidly degraded than aromatic components, and removal of aromatic compounds was somewhat unstable even after 2 months of biofilter operation. Scanning electron microscopy (SEM) revealed that fungi dominated the microbial populations in both biofilters.     

The change of the diffusivity with the change of the concentration of the solvent in a solution

Summary We consider the convective mass transfer of drops and solid particles with a viscous liquid flow when the diffusion coefficient is arbitrarily dependent on the concentration. We discuss the exact solutions of this problem and we present such a solution for the special case of hyperbolic dependence of the diffusion coefficient on the concentration. The formula for the average Sherwood number is obtained.With 3 Figures     

SUBLIBOX: a proprietary solvent free method for intense vaporization of solid compounds

Chemical vapour deposition and atomic layer deposition using precursors that are solids at ambient temperature and pressure present challenges due to the often low saturating vapour pressure of these compounds. Additional concerns arise from the difficulty to maintain a reproducible and stable precursor flow rate to the deposition chamber and from the possible particle contamination if suitable safeguards are not built into the precursor delivery line. In the present contribution, SUBLIBOX, a pilot industrial scale sublimator is presented. SUBLIBOX is based on a new sublimation process involving gas-solid fluidization technology. Aluminum acetyl-acetonate [Al(acac)3], a promising precursor for the processing of alumina films despite its low saturated vapour pressure, is used as a model, though technologically interesting system. Mass balance measurements, involving trapping of the sublimed precursor at the exit of the sublimation chamber, reveal that SUBLIBOX ensures (a) stable, (b) efficient, (c) reproducible and (d) long term precursor vapour flow rates. The process is particularly well adapted for delivering vapours to CVD reactors for coatings on glass and stainless steel or for producing optical fibbers preforms by various techniques.     

Hermite–Cloud: a novel true meshless method

In this paper, a novel true meshless numerical technique – the Hermite–Cloud method, is developed. This method uses the Hermite interpolation theorem for the construction of the interpolation functions, and the point collocation technique for discretization of the partial differential equations. This technique is based on the classical reproducing kernel particle method except that a fixed reproducing kernel approximation is employed instead. As a true meshless technique, the present method constructs the Hermite-type interpolation functions to directly compute the approximate solutions of both the unknown functions and the first-order derivatives. The necessary auxiliary conditions are also constructed to generate a complete set of partial differential equations with mixed Dirichlet and Neumann boundary conditions. The point collocation technique is then used for discretization of the governing partial differential equations. Numerical results show that the computational accuracy of the Hermite–Cloud method at scattered discrete points in the domain is much refined not only for approximate solutions, but also for the first-order derivative of these solutions.     

Analysis of a digital microstrip optical switch: a novel method

A time domain analysis of an optically controlled digital microstrip switch for microwave integrated circuits on Si substrates is studied. A new model for high-frequency pulse propagation on a microstrip optical switch for different optical parameters is presented. A frequency-dependent macromodel for a microstrip line with a gap is implemented in Spice 3, taking into consideration high-frequency pulse dispersion, conductor and dielectric losses, metallization thickness, gap length, and different optical parameters such as optical energy, surface recombination velocities, and diffusion of generated carriers. In addition, the developed model has been used to optimize the switching frequency, gap length, level of optical power, and suitable substrate material parameters.     

A selection of material using a novel type decision-making method: Preference selection index method

The aim of the current study is to implement a novel tool to help the decision-maker for selection of a proper material that will meet all the requirements of the design engineers. Preference selection index (PSI) method is a novel tool to select best alternative from given alternatives without deciding relative importance between attributes. In the present study, three different types of material selection problems are examined. A validation and consistency test of preference selection index method is performed in present work by comparing results of PSI method with published results of graph theory and matrix approach (GTMA), and technique for order preference by similarity to ideal solution (TOPSIS) method, respectively. The research has concluded that the PSI method is logical and more appropriate for the material selection problems.     

Spray-spinning: a novel method for making alginate/chitosan fibrous scaffold

The subject of our investigations was the process of obtaining alginate/chitosan polyelectrolyte complex (PEC) fibers. In this study, a novel method named “spray-spinning” was developed for the making of these hybrid fibers. In spray-spinning, a chitosan solution was sprayed into a flowing sodium alginate solution and sheared into streamlines. The elongated streamlines subsequently transformed into alginate/chitosan PEC fibers. Average diameter of the fibers increased with the increasing of chitosan concentration used in spinning. The fibers showed a high water-absorbability of about 45 folds of water to their dry weight and retained their integrity after incubation in Minimum Essential Medium (MEM) for up to 30 days. In vitro co-culture experiments indicated that the fibers could support the three-dimensional growth of HepG2 cells and did not display any cyto-toxicity. Moreover, in vivo implanting experiments indicated that the connective tissue cells infiltrated into the implanted fibrous scaffolds in 3 weeks after surgery. These results demonstrated the potential applications of the as-spun fibers in regenerative medicine and tissue engineering.     

Passing of instability points by applying a stabilized Newton–Raphson scheme to a finite element formulation: Comparison to arc-length method

In the vicinity of limit and bifurcation points the global stiffness matrix of a finite element formulation becomes ill-conditioned and at the critical point singular. This disturbs the convergence behavior of the standard Newton–Raphson scheme as well as the arc-length method. The stabilization procedure suggested solves the numerical defects and is thus able to pass critical points. Bifurcation points are passed on the primary path. Branch switching to the secondary path is done automatically. The stabilization procedure and the imperfection force are derived based on the eigenvalues and -vectors of the structure.     

Drug solubility in phospholipid carrier as a predictive parameter for drug recovery in microparticles produced by the aerosol solvent extraction system (ASES) process

The solubility of various drugs in a constant ratio of phosphatidylcholine-cholesterol carrier were studied to investigate their influence on drug recovery in drug-lipid microparticles produced by the aerosol solvent extraction system (ASES) process. Solubility of the drugs in such lipid carrier were determined by using differential scanning calorimetry and confirmed by X-ray powder diffraction study. The results showed that drug possessing relatively high solubility in the lipid carrier used could lead to a higher amount of drug recovered in the drug-lipid microparticles produced. However, too high amount of dissolved drug imposed an adverse effect on the solidification of the lipid carrier during ASES processing, which led to partial film formation in the production column and hence a lower yield of microparticles. Such adverse effect was not the case for the drugs with low solubility in the carrier but there was an incomplete recovery of drug in the produced microparticles due to the partial extraction by the supercritical gas instead. The maximum amount of drug recovered in the ASES-prepared microparticles was found to correlate to the solubility of drug in the lipid carrier so that it might be utilized as a predictive parameter for determining the amount of drug to be incorporated into the microparticles.     

The three-prong method: a novel assessment of residual stress in laser powder bed fusion

ABSTRACT

Residual stress is a major problem for most metal-based laser powder bed fusion (L-PBF) components. Residual stress can be reduced by appropriate build planning and post-process heat treatments; however, it is not always avoidable and can lead to build failures due to distortion and cracking. Accurate measurement of residual stress levels can be difficult due to high equipment set-up costs and long processing times. This paper introduces a simple but novel method of measuring residual stresses via a three-pronged cantilever component, the three-prong method (TPM). The method allows for a quick and easy characterisation of residual stress for a wide range of machine parameters, build strategies and materials. Many different cantilever designs have been used to indicate residual stress within additive manufacturing techniques. All of which share the same shortcoming that they indicate stress in one direction. If the principal component of stress is not aligned with the beam geometry, it will underestimate peak stress values. A novel three-prong design is proposed which covers two dimensions by utilising three adjoined cantilever beams, a configuration which echoes that of hole-drilling where three measurements are used to calculate the stress field around a drilled hole. Each arm of the component resembles a curved bridge-like structure; one end of each bridge is cut away from the base plate leaving the centre intact. Deformation of the beams is then measured using a co-ordinate measurement machine. Stress profiles are then estimated using finite element analysis by meshing the deflected structure and forcing it back to its original shape. In this paper, the new TPM is used to compare the residual stress levels of components built in Ti–6Al–4V with different hatch patterns, powers and exposure times.     

Preparation of a novel fluorescent nanocomposite: CeO2 / ANS by a simple method

For the first time, a novel fluorescent material, composed of CeO₂/ANS nanocomposites was successfully synthesized by a simple ultrasonic method, using CeO₂ nanoparticles and 8-anilino-1-naphthalenesulfonic acid (ANS) as the raw materials. The samples were characterized by scanning electron microscope (SEM), photoluminescence spectroscopy and Fourier transformation infrared spectroscopy (FTIR). The results showed that the PL intensity of the CeO₂/ANS nanocomposites was higher than that of both CeO₂ nanoparticles and ANS powders, and the peak wavelength was also different from the peak wavelength typical of each of the used materials, which suggests that the chemical reaction occurs between CeO₂ nanoparticles and ANS molecules. In addition, the effect of the ANS concentrations on the photoluminescence of the nanocomposites was also investigated.     

A novel method for reducing the dimensionality in a sensor array

Specific types of gas sensors are normally produced by adding different dopants to a common substrate. The advancement of technology has made the fabrication of many dopants and consequently various sensors possible. As a result, in each family of gas sensors, one can find tens of different sensors which are only slightly different in the spectrum of response to various volatile compounds. The wide variety of available gas sensors creates a selection problem for any specific application. Sensor selection/reduction becomes even more important when cost and technology limitations are issues of concern. Accordingly, a methodology by which one can tailor a sensor array to a specific need is highly desirable. In this paper, a novel method is introduced to address this task using data from an electronic nose that uses polymer gas sensors. This method has been delineated based on the geometry of eigenvectors in Karhunen-Loeve expansion. The methodology is general and therefore suitable for many other feature selection problems     

Fibrin nanoconstructs: a novel processing method and their use as controlled delivery agents

Fibrin nanoconstructs (FNCs) were prepared through a modified water-in-oil emulsification-diffusion route without the use of any surfactants, resulting in a high yield synthesis of fibrin nanotubes (FNTs) and fibrin nanoparticles (FNPs). The fibrin nanoconstructs formed an aligned structure with self-assembled nanotubes with closed heads that eventually formed spherical nanoparticles of size ~250 nm. The nanotubes were typically ~700 nm long and 150-300 nm in diameter, with a wall thickness of ~50 nm and pore diameter of about 150-250 nm. These constructs showed high stability against aggregation indicated by a zeta potential of -44 mV and an excellent temperature stability upto 200 °C. Furthermore, they were found to be enzymatically degradable, thereby precluding any long term toxicity effects. These unique fibrin nanostructures were analyzed for their ability to deliver tacrolimus, an immunosuppressive drug that is used widely to prevent the initial phase of tissue rejection during allogenic transplantation surgeries. Upon conjugation with tacrolimus, a drug encapsulation efficiency of 66% was achieved, with the in vitro release studies in PBS depicting a sustained and complete drug release over a period of one week at the physiological pH of 7.4. At a more acidic pH, the drug release was very slow, suggesting their potential for oral-intestinal drug administration as well. The in vivo drug absorption rates analyzed in Sprague Dawley rats further confirmed the sustained release pattern of tacrolimus for both oral and parenteral delivery routes. The novel fibrin nanoconstructs developed using a green chemistry approach thus proved to be excellent biodegradable nanocarriers for oral as well as parenteral administrations, with remarkable potential also for delivering specific growth factors in tissue engineering scaffolds.     

Environmental crazing in a glassy polymer: the role of solvent absorption

According to a recent theory of Andrews and Bevan, the work of solvent craze formation, ₀ is governed by the cavitation properties of a solvated zone of polymer at the craze tip. In particular, the shear yield stress of this zone and its temperature dependence dictate the variation of ₀ with temperature. In order to investigate this matter further, samples of poly-methylmethacrylate were swollen to equilibrium in a variety of alcohols at different temperatures, and the equilibrium polymer fraction ₂ determined as a function of temperature and solvent. The variation of yield stress with ₂, solvent and temperature was also investigated, and the glass transition temperatures determined as functions of ₂ and solvent.The temperature at which the equilibrium swelling was just sufficient to depress the polymerT _g to a co-incident value was found to correspond closely to the characteristic temperature, identified by Andrews and Bevan, at which the temperature dependence of ₀ changes abruptly. This is shown to be in complete accord with the cavitation theory referred to.     

一种全新的激光自动跟踪方法在激光移动通信中的应用

介绍了传统激光移动通信的特点及其不足，提出一种基于MOEMS(微光机电系统)技术的全新的激光自动跟踪方法。给出一个基于这种方法的激光移动通信系统实例，这种系统结构简单、体积小、重量轻、功耗低、控制简便，在一定的角度范围内能够自动跟踪目标实现移动通信。实验研究结果表明，这种系统能够很好地满足激光移动通信所要求的功能。     

A novel method to prepare magnetic nanoparticles: precipitation in bicontinuous microemulsions

A novel method to prepare iron oxide nanoparticles by precipitation in bicontinuous microemulsions is reported. Precipitation reactions were carried out in microemulsions stabilized with a mixture of dodecyltrimethylammonium bromide/didodecyldimethylammonium bromide (3/2, w/w). Nanoparticles were characterized by X-ray diffraction, transmission electronic microscopy (TEM) and vibrating sample magnetometry (VSM), and consisted of magnetite or a mixture of magnetite and maghemite. The particles have an average diameter of 8 nm with a relatively narrow particle size distribution and show possible superparamagnetic behavior. Noticeably higher yields of precipitate are observed for this new approach in comparison with those typicall obtained using reverse microemulsions.     

Thermal,electrical, and physical properties of novel phase stabilized material: hybrid plastilina nanocomposites for effective thermal management in electronics

Journal of Materials Science: Materials in Electronics - To operate efficiently, high-performance devices require excellent heat dissipation to counteract overheating. Therefore, high thermal...