Formation and Stability of Smooth Thin Films with Soft Microgels Made of Poly(N-Isopropylacrylamide) and Poly(Acrylic Acid)

In this work, soft microgels of Poly(N-Isopropylacrylamide) (PNIPAm) at two different sizes and of interpenetrated polymer network (IPN) composed of PNIPAm and Poly(Acrylic Acid) (PAAc) were synthesized. Then, solutions of these different types of microgels have been spin-coated on glass substrates with different degrees of hydrophobicity. PNIPAm particles with a larger diameter form either patches or a continuous layer, where individual particles are still distinct, depending on the dispersion concentration and spin speed. On the other, PNIPAm particles with a smaller diameter and IPN particles form a continuous and smooth film, with a thickness depending on the dispersion concentration and spin-speed. The difference in morphology observed can be explained if one considers that the microgels may behave as colloidal particles or macromolecules, depending on their size and composition. Additionally, the microgel size and composition can also affect the stability of the depositions when rinsed in water. In particular, we find that the smooth and continuous films show a stimuli-dependent stability on parameters such as temperature and pH, while large particle layers are stable under any condition except on hydrophilic glass by washing at 50 °C.

GeTe-Based Alloy Films Prepared by a Room Temperature Solution Process

This article describes the preparation of GeTe-based alloy films using a solution-based technique. The dissolution behavior of GeTe was initially examined by comparing the weight loss of GeTe powder in different solvents, and it was found that, unlike in the cases of n-butylamine and NH4OH, KOH fully dissolved GeTe to form an agglomerate-free solution. X-ray diffraction analysis revealed that the reaction between GeTe and KOH resulted in the formation of rhombohedral GeTe, cubic GeTe4, and hexagonal Te structures after drying. GeTe-based alloy films were then prepared by the spin coating of the GeTe-containing solutions on a silicon substrate. The surface morphology and reflectance properties of the prepared films were found to be highly dependent on the spin speed, with optimization of the spin coating parameter resulting in the deposition of a continuous and smooth film.

Enhancing the Performance of Aqueous Solution-Processed Cu2ZnSn(S,Se)4 Photovoltaic Materials by Mn2+ Substitution

In this work, the Cu2MnxZn1−xSn(S,Se)4 (0 ≤ x ≤ 1) (CMZTSSe) alloy films were fabricated by a sol-gel method. Meanwhile, the effects of Mn substitution on the structural, morphological, electrical, optical, and device performance were studied systematically. The clear phase transformation from Cu2ZnSn(S,Se)4 (CZTSSe) with kesterite structure to Cu2MnSn(S,Se)4 (CMTSSe) with stannite structure was observed as x = 0.4. The scanning electron microscope (SEM) results show that the Mn can facilitate the grain growth of CMZTSSe alloy films. Since the x was 0.1, the uniform, compact, and smooth film was obtained. The results show that the band gap of the CMZTSSe film with a kesterite structure was incessantly increased in a scope of 1.024–1.054 eV with the increase of x from 0 to 0.3, and the band gap of the CMZTSSe film with stannite structure was incessantly decreased in a scope of 1.047–1.013 eV with the increase of x from 0.4 to 1. Meanwhile, compared to the power conversion efficiency (PCE) of pure CZTSSe device, the PCE of CMZTSSe (x = 0.1) device is improved from 3.61% to 4.90%, and about a maximum enhanced the open-circuit voltage (VOC) of 30 mV is achieved. The improvement is concerned with the enhancement of the grain size and decrease of the Cu instead of Zn (CuZn) anti-site defects. Therefore, it is believed that the adjunction of a small amount of Mn may be an appropriate approach to improve the PCE of CZTSSe solar cells.

Higher quantum efficiency and moisture resistance of all-inorganic halide perovskite nanocrystal films in situ fabricated with cyclodextrin

β-Cyclodextrin confines the growth of CsPbBr3 nanocrystals, generating a smooth film with a higher quantum efficiency and a longer moisture resistance.

Solar-blind photodetector based on Ga2O3 nanowires array film growth from inserted Al2O3 ultrathin interlayers for improving responsivity

We propose a method to obtain Ga2O3 nanowire films which combines the benefits of nanowires and thin films by alternative deposition of Ga2O3 and Al2O3 ultrathin layers. The nanowire film-based photodetectors exhibit much higher responsivities than smooth film-based ones.

Investigation of a Prefilming Airblast Atomizer With Respect to Surface Stripping

One commonly used injection system in gas turbines is the prefilming airblast atomizer which creates a fuel film that should disintegrate at the end of the prefilmer. But under certain conditions droplets are separated from the film before reaching the end of the prefilmer. This phenomenon is called surface stripping. For the investigation of those conditions both an experimental and numerical setup are defined. The experiment measures the film thickness on the prefilmer with the help of the planar laser-induced fluorescence technique. For the numerical investigation the volume of fluid method together with a large eddy simulation of OpenFOAM® 2.1.1 is used. After the validation of the numerical model with the experimental data, the dependency of the mean film thickness from the relative velocity of air and water is investigated. It is shown that first the momentum flux ratio is not sufficient in describing the behavior of the film on the prefilmer and second a critical relative velocity has to be exceeded so that surface stripping can take place. Three flow regimes are observed by increasing the relative velocity: smooth film surface, wavy film surface and surface stripping. Due to the surface stripping the transferred fuel mass into the gas phase is increased rapidly.

AFM Study of Magnetron Sputtered Nickel Films Coated on Cenosphere Particles

The morphologies of nanocrystalline nickel film coated on cenosphere particles using magnetron sputtering method were investigated by atomic force microscopy (AFM). The AFM results show the grain sizes and root-mean-square (RMS) roughness values of nickel films increase with the increase of sputtering power or deposition time and the nickel films growth is a three-dimensional island growth mode. The unceasingly variational angular distribution can get rid of the physical shadowing effect of the sputtering and promote a rather smooth film growth. Due to the all-around effect, the final distribution of grains shows a rather smooth morphology with low roughness.

Preparation and Properties of Emulsion Type Sizing Agent for Carbon Fiber

The epoxy resin and polyalkylene glycol allyl glycidyl ether (AEPH) were used to prepare the emulsion type epoxy sizing agents for carbon fiber (CF) by phase inversion emulsification method. Effects of mass ratio of mixed emulsifiers and emulsifiers/resin (ωe/r) and shear rate on stability of emulsion were investigated by centrifugal sedimentation analysis. Scanning electron microscope (SEM) was used to analyze the surface morphology of carbon fiber. Results show that the optimal emulsion was obtained when mass ratio of polyoxyethylene octylphenol ether-10 (OP-10), polysorbate-80 (Tween-80) and sodium dodecyl benzene sulfonate (SDBS) was 65:25:10, ωe/rwas 9% and shear rate was 9000 r/min. The centrifugal sedimentation mass fraction of emulsion is 10.1%. SEM micrograph shows that the sizing agent forms a smooth film covering the carbon fibers.

Electrochromic Performance of NiO Films in Alkaline Medium

An investigation on the electrochromic performance of NiO films in 1M KOH was carried out using cyclic voltammetric technique. The NiO films were deposited on ITO glass substrate using bath solution containing nickel sulfate, sodium acetate and sodium sulfate at pH 6.7 by applying constant current of 0.2 mA cm-2for 300 s at different deposition temperatures (ie: 25 °C, 40 °C and 80 °C). The as-deposited films were undergone post treatment through annealing process at 300 °C for 900 s. The surface morphology of the NiO thin films was characterized by field-emission scanning electron microscopy (FESEM) and the electrochemical properties of both NiO films were measured in 1M KOH electrolyte by cyclic voltammetry (CV). Deposition at 25 °C produced a smooth and compact thin film on the ITO surface. However, when higher temperatures were used (ie: 40 °C and 80 °C), porous structure of NiO formed. The electrochromic performance of the smooth film prepared at 25 ° C showed is better than the porous films. The annealing process has enhanced the stability of NiO film for intercalation and de-intercalation of OH-ions during cycling in 1M KOH. These results show that the temperature (heating and annealing process) has significantly influenced the formation of NiO films on ITO substrates which affected the performance of the electrochromic material.

Synthesis and Property of Water-Soluble Hyperbranched Polyacrylate Emulsion

Hyperbranched polymer is a kind of non-linear polymers with highly branched structure and a lot of terminal groups. It has many advantages, such as high reactivity, good solubility and low viscosity. Hyperbranched polymer has become a focus in modern scientific domain. In this paper, polyester-type water-soluble hyperbranched monomer is prepared by the ring-opening polymerization reaction of maleic anhydride with polyol. Hyperbranched polyacrylate emulsion with 70-110nm was synthesized by emulsion polymerization using methyl methacrylate (MMA), butyl acrylate (BA), acrylic acid (AA) and hyperbranched polymer as comonomer. The effects of dosages and adding order of monomers, concentration of initator, type and amount of chain transfer agent on the polymerization are discussed. The as-prepared emusions were analyzed by FTIR, DSC, SEM. The solid content, particle size, stability of emulsion and morphology and water absorption of film were measured. The results showed that hyperbranched polyacrylate emulsion had low viscosity, high stability and can form very flat and smooth film. Hyperbranched polyacrylate emulsion can be widely applied in modern ink industry for its low cost,simple process and stable quality.