Semiquantitative Investigation of Tablet Coats by Electron Probe Microanalysis

Abstract

The combined, non-destructive techniques of scanning electron microscopy and electron probe X-ray microanalysis were used to investigate the composition of commercial tablets containing a) film and b) sugar coats, before and after a series of processes designed to challenge the integrity of the coat

Elemental analysis and estimations of coat thickness and integrity were rapidly made with a single tablet. Using the process of X-ray mapping, it was possible to identify chemically, discrete subcoats of the sugar coat which were indistinct on the electron micrograph. Analyses of these substrata may prove useful in assessing adherence to correct coating procedures     

Effects of sputtering power on mechanical properties of Cr films deposited by magnetron sputtering

Abstract

Chromium (Cr) films were deposited on plain carbon steel sheets by dc and rf magnetron sputtering as well as by electroplating. Effects of dc or rf sputtering power on the deposition rate and properties such as, hardness, adhesion strength, surface roughness and corrosion resistance of the Cr films were investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microcopy (SEM) analyses were performed to investigate the crystal structure, surface roughness, thickness of the Cr films. Salt fog tests were used to evaluate the corrosion resistance of the samples. The deposition rate, hardness and surface roughness of the Cr film deposited by either dc or rf sputtering increase with the increase in sputtering power but the adhesion strength is nearly independent of the sputtering power. The deposition rate, hardness and adhesion strength of the Cr film deposited by dc sputtering are higher than those of the Cr film deposited by rf sputtering, but rf sputtering offers smoother surface and higher corrosion resistance. The sputter deposited Cr film is harder and has a smoother surface than the electroplated one. The sputter deposited Cr film also has higher corrosion resistance than the electroplated one, which may be attributed to the smoother surface of the sputter deposited film.     

X-ray reflectivity study of bias graded diamond like carbon film synthesized by ECR plasma

Diamond like carbon (DLC) coatings were deposited on silicon substrates by microwave electron cyclotron resonance (ECR) plasma CVD process using plasma of Ar and CH ₄ gases under the influence of negative d.c. self bias generated on the substrates by application of RF (13·56 MHz) power. The negative bias voltage was varied from ?60 V to ?150 V during deposition of DLC films on Si substrate. Detailed X-ray reflectivity (XRR) study was carried out to find out film properties like surface roughness, thickness and density of the films as a function of variation of negative bias voltage. The study shows that the DLC films constituted of composite layer i.e. the upper sub surface layer followed by denser bottom layer representing the bulk of the film. The upper layer is relatively thinner as compared to the bottom layer. The XRR study was an attempt to substantiate the sub-plantation model for DLC film growth.     

The effect of superalloy substrate on the behaviour of high-purity low-density air plasma sprayed thermal barrier coatings

Abstract

Several superalloy-bond coat couples were prepared without ceramic topcoat layers to better understand the effects of superalloy substrate on the oxidation behaviour of NiCoCrAlY bond coats. The same composition NiCoCrAlY bond coats were deposited on three superalloy substrates (Inconel 718, Haynes 188 and Rene’ N5) via argon-shrouded plasma spraying. The specimens were exposed to cyclic oxidation in laboratory air at 1100°C in a bottom loading furnace. Scaling behaviour and rate of aluminum depletion were compared between the various specimens. The bond coats on all three superalloys experienced some form of chemical failure after an extended number of cycles. The number of cycles until chemical failure was shortest for the IN718 specimen followed by the HA188 specimen, both of which experienced complete bond coat chemical failure, and then the Rene’ N5 specimen, which experienced localized chemical failure. The cycles to chemical failure coincide with the cycles to thermal barrier coating (TBC) spallation from previous work, indicating chemical failure of the bond coat is a critical event in the lifetime of TBCs. The effect of bond coat surface finish and porosity on the scaling behaviour has been investigated using specimens with the same superalloy substrate but with different bond coat surface finishes and porosity levels which were produced by utilizing two separate sized starting bond coat metallic powders. Bond coats with minimal porosity and smooth surface finishes did not experience chemical failure, at least in the time frame they were tested; however, oxide scale spallation was more apparent in the smooth bond coats as compared to the specimens with the rough surface finishes and high levels of porosity.     

Semiquantitative Investigation of Tablet Coats by Electron Probe Microanalysis

The combined, non-destructive techniques of scanning electron microscopy and electron probe X-ray microanalysis were used to investigate the composition of commercial tablets containing a) film and b) sugar coats, before and after a series of processes designed to challenge the integrity of the coat

Elemental analysis and estimations of coat thickness and integrity were rapidly made with a single tablet. Using the process of X-ray mapping, it was possible to identify chemically, discrete subcoats of the sugar coat which were indistinct on the electron micrograph. Analyses of these substrata may prove useful in assessing adherence to correct coating procedures     

Microstructural characterization of the failures of thermal barrier coatings on Ni-base superalloys

Abstract

Typical thermal barrier coating (TBC) systems consist of a nickel-base superalloy substrate coated with a MCrAlY or diffusion aluminide bond coat, onto which is deposited a yttria-stabilized zirconia (YSZ) TBC. The bond coats are usually deposited via diffusion aluminizing processes or low pressure plasma spray processes (LPPS). The YSZ can be deposited by air plasma spraying (APS) or electron beam physical vapor deposition (EBPVD). A layer of thermally-grown oxide (TGO), which is usually alumina, forms between the bond coat and YSZ during TBC deposition and subsequent high-temperature exposure. The conventional wisdom is that APS coatings tend to fail in the YSZ and that EBPVD coatings tend to fail at the interface between the TGO and bond coat. However, current research has shown that the situation is much more complex and that the actual fracture path can be a function of the type of bond coat, the type of high-temperature exposure, and coating process parameters. This paper describes the results of a study of the failure of state-of-the-art EBPVD TBCs deposited on NiCoCrAlY and platinum-modified diffusion aluminide bond coats. The failure times and fracture morphology are described as a function of bond coat type. The failure times were found to be a strong function of temperature for both bond coats. The failure for NiCoCrAlY bond coats was found to initiate at defects in the coating, particularly at the TGO/YSZ interface, but the fracture propagated primarily along the TGO–bond coat interface. The failure times and morphologies for platinum-modified diffusion aluminide bond coats depended strongly on bond coat surface preparation. The mechanisms for failure of the two bond coats are described. Also, the effects of modifications to the bond coats and variations in processing parameters on these mechanisms are presented.     

An atomic force microscope study of surface roughness of thin silicon films deposited on SiO/sub 2/

Atomic force microscope analysis, with a resolution of /spl lsim/1.1 nm, shows that peak-to-peak surface roughness (/spl Delta/h/sub p-p/) of amorphous silicon films thinner than /spl ap/50 nm on silicon dioxide can be controlled to better than 5 nm. Low-pressure, chemically-vapor-deposited silicon films on silicon dioxide initially show an approximately linear increase in the surface roughness due to growing nuclei as the deposition progresses, followed by a decrease in the surface roughness as growth nuclei coalesce. A simple model based on random nucleation and nuclei growth displays similar trends. Films deposited on rougher substrates show more surface roughness. Surface treatment during the predeposition cleaning process does not significantly affect /spl Delta/h/sub p-p/. As a means of producing smooth surfaces, films thinner than about 20 nm are first deposited more thickly than needed, and then etched back to the desired dimension; the use of a binary HNO/sub 3/ and HF etching process improves roughness control. Boron-ion implanted and subsequently crystallized 45-nm-thick Si films show significant smoothing with /spl Delta/h/sub p-p//spl ap/2.2 nm. Thin amorphous silicon films deposited by source evaporation are attractive because they can be deposited at room temperature, and have smoother surfaces (/spl Delta/h/sub p-p//spl ap/2.5 nm) than comparable films produced by chemical vapor deposition.     

Interplay of CaF2

Abstract

The radiative decay of surface plasmon polaritons has been investigated in an attempt to characterize the surface roughness of Ag films prepared under different conditions. The polaritons were excited by the method of attenuated total reflection of light. The films were deposited on the face of a 60° BK-7 glass prism at a rate that was deliberately fixed in two different ranges (centred on 0·1 and 10 nms^?1) and in some cases a CaF₂ underlayer was used to roughen the film surfaces. The intensity of the scattered light emitted from the opposite face of the films was measured as a function of direction for each using the same sensitivity scale and was correlated with the preparation of the film. It was found that on nominally smooth substrates fast-deposited thinner films give out more light and are deduced to have greater short wavelength (300–600 nm) roughness amplitude. There is also evidence for long wavelenth (7μm) periodic roughness due to the prism substrate itself. On CaF₂ roughened surfaces the light output from the films is further increased and the peak intensity is backward directed with respect to the exciting laser beam direction. Here roughness on a lateral scale of 350 nm is responsible. Also, elastic scattering of surface plasmon polaritons at grain boundaries reduces the light output from fast deposited, small grain, films on CaF₂ roughened surfaces. Overall, a consistent picture of roughness induced radiative polariton decay emerges for all cases studied.     

A High Performance Liquid Chromatographic Method for the Determination of the Amount of Hydroxypropyl Methylcellulose Applied to Tablets During an Aqueous Film Coating Operation

Abstract

A method for determination of the amount of polymer film coat actually applied to tablets as a result of aqueous film coating was developed using gel permeation chromatography (GPC). A styrene-based GPC column (Ultrastyrage]^R 100A) was found to provide good separation of a commercially available polymer film coat (Opadry^R) from other tablet constituents. The assay method is simple, rapid and reproducible with coefficients of variation less than 2.6% in all cases. The assay is sensitive enough to discriminate between tablets containing different levels of microcrystalline cellulose (MCC) when coated simultaneously. The assay was conducted on polymer extracted from the tablets with a solution of 50/50 methanol/methylene chloride. The addition of MCC to tablet formulations was found to increase the amount of film applied, in a competitive coating operation, when all other factors were held constant.     

Thickness of ITO thin film influences on fabricating ZnO nanorods applying for dye-sensitized solar cell

Background and purposeIn order to compare the substrates influence on the properties of ZnO films and nanostructures, in this paper, the ITO substrates with different thicknesses were investigated.MethodITO thin films of different thickness (200 nme500 nm) were deposited on glass substrates by DC sputtering, on which ZnO nanorods were fabricated from as-deposited ZnO films by reducing annealing method.ResultsIt was found that the structural and electrical properties of ITO films were significantly influenced by the ITO film thickness. The roughness of ITO films was increased with increase in thickness. The Hall mobility of ITO films was also increased with the increase of film thickness; in contrast, the resistivity was decreased. The highest Hall mobility of 29.2 cm²/V s and the lowest resistivity of 1.303 × 10⁻⁴ Ω cm were obtained from 500 nm-thick ITO film. The structural properties of ZnO nanorods were significantly influenced by the ITO film thickness. The density of ZnO nanorods gradually decreased with the increase in thickness of ITO film.ConclusionThe overall conversion efficiency of demonstrated dye-sensitized solar cell was 2.11% with a fill factor 0.526, indicating high potential to be used as photoanodes in dye-sensitized solar cell applications.     

Quantitative analysis of electrodeposited tin film morphologies by atomic force microscopy

This study of the electrodeposition of tin on steel substrates demonstrates that it is possible to obtain quantitative information on the thin film growth at industrially relevant substrates using atomic force microscopy (AFM) to monitor the film morphology and X-ray fluorescence (XRF) to measure the average film thickness. The effects of current density and electrolyte temperature on the film morphology, surface roughness, and grain size distribution (GSD) are reported. While the roughness of the substrates used in this study can vary by several hundred nanometers to a micrometer, we are interested in quantitative characterization of the tin films with thickness varying from a few tens of nanometers to several hundred nanometers. This study shows that for the range of film thickness and length scale studied, analysis of the AFM images can provide quantitative characterization of the thin film roughness and grain size distribution at various stages of growth with little interference from the substrate morphological inhomogeneities.     

316L不锈钢和NiTi合金微磁场表面粗糙度对血液相容性的影响

在316L不锈钢、NiTi合金的含SrFe12O19磁性粉末的TiO2薄膜表面用溶胶-凝胶法再涂覆不同层数的TiO2薄膜,以降低材料微磁场表面的微粗糙度,并用扫描电镜、粗糙度仪分析薄膜的表面粗糙度.测试了不同粗糙度的微磁场表面的动态凝血时间和溶血率,研究了微磁场表面的粗糙度对材料血液相容性的影响.结果表明,粗糙度小的微磁场表面的血液相容性比粗糙度大的微磁场表面的血液相容性好.即对于平整光滑的微磁场表面,可以利用微磁场提高材料血液相容性的同时,进一步改善材料的血液相容性.     

Epitaxial growth of SrRuO<Subscript>3</Subscript> thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

Spectrographic ellipsometry study of a liquid crystal display substrate consisting of thin films of SiO2, polyimide and indium tin oxide on glass

Variable angle spectrometric ellipsometry at room temperature is used to determine thin film parameters of substrates used in liquid crystal displays. These substrates consist of sequential thin films of polyimide (PI), on indium tin oxide (ITO),on SiO₂ deposited on a glass backing approximately 1.1 mm thick. These films were studied by sequentially examining more complex systems of films (SiO₂, SiO₂-ITO, SiO₂-ITO-PI). The SiO₂ layer appears to be optically uniform and flat. The ITO film is difficult to characterize. When this surface film's lower surface is SiO₂ and upper surface is an air-ITO-interface it is found that including surface roughness and variation of the optical properties with ITO thickness in the model improved the fit; suggesting that both phenomena exist in the ITO films. However, the surface roughness and graded nature of optical properties could be not determinable by ellipsometry when the ITO is coated with a polyimide film. The PI films are ellipsometrically flat and over the wavelength range from 500 to 1400 nm the real refractive index of polyimide films varying in thickness between 25 and 80 nm is well modeled by a two-term Cauchy model with no absorption. The ellipsometric thickness of the ITO layer is the same as the profilometric thickness; however, the ellipsometric thickness of the polyimide layers is roughly 10 nm larger than that obtained from the profilometer. These final observations are consistent with the literature.     

A Novel Imaging Technique to Investigate the Influence of Atomization Air Pressure on Film–Tablet Interfacial Thickness

A novel X-ray photoelectron spectroscopic (XPS) technique combined with principal component analysis of spectra-to-image datasets was employed to study the effects of atomization air pressure used during the coating process on film–tablet interfacial thickness. Placebo tablet cores were prepared and coated with Eudragit^® RL 30 D. Atomization air pressure was varied from 10 to 20 psi, whereas all other processing parameters were held constant. Higher air pressures generally produced thinner interfaces, although the interfacial region was not uniform across the tablet surface and was dependent on the sampling location. These results demonstrate the suitability of this XPS technique to study the coating–tablet interface. Moreover, the variability in the interfacial thickness illustrates the need to further study such systems.     

Osseointegration evaluation of laser-deposited titanium dioxide nanoparticles on commercially pure titanium dental implants

The nanotechnology field plays an important role in the improvement of dental implant surfaces. However, the different techniques used to coat these implants with nanostructured materials can differently affect cells, biomolecules and even ions at the nano scale level. The aim of this study is to evaluate and compare the structural, biomechanical and histological characterization of nano titania films produced by either modified laser or dip coating techniques on commercially pure titanium implant fixtures. Grade II commercially pure titanium rectangular samples measuring 35?×?12?×?0.25?mm length, width and thickness, respectively were coated with titania films using a modified laser deposition technique as the experimental group, while the control group was dip-coated with titania film. The crystallinity, surface roughness, histological feature, microstructures and removal torque values were investigated and compared between the groups. Compared with dip coating technique, the modified laser technique provided a higher quality thin coating film, with improved surface roughness values. For in vivo examinations, forty coated screw-designed dental implants were inserted into the tibia of 20 white New Zealand rabbits’ bone. Biomechanical and histological evaluations were performed after 2 and 4 weeks of implantation. The histological findings showed a variation in the bone response around coated implants done with different coating techniques and different healing intervals. Modified laser-coated samples revealed a significant improvement in structure, surface roughness values, bone integration and bond strength at the bone-implant interface than dip-coated samples. Thus, this technique can be an alternative for coating titanium dental implants.     

Epitaxial growth of SrRuO3 thin films by RF sputtering and study of surface morphology

We report on the epitaxial growth of SrRuO₃ (SRO) thin films on Pt (111)/γ-Al₂O₃ (111) nSi (111) substrates. The grown thin films are crystalline and epitaxial as suggested by RHEED and XRD experiments. With the use of γ-Al₂O₃ (001)/nSi (001) and γ-Al₂O₃ (111)/nSi (111) substrates, crystalline but not epitaxial films have grown successfully. This result implies that lattice mismatch between nSi and SRO prevents the epitaxial growth of SRO film directly on nSi. However, the buffer Pt (111) layer mitigates lattice mismatch that provides to grow epitaxial film on nSi of quality. Morphological study shows a good surface with moderate roughness. Film grown at 700°C is smoother than the film grown at 750°C, but the variation of temperature does not affect significantly on the epitaxial nature of the films.     

用AFM研究硅基上沉积铜膜生长过程

室温下,利用磁控溅射在P型Si(111)衬底上沉积了铜(Cu)膜.用原子力显微镜(AFM)对不同沉积时间制备的Cu膜形貌进行了观测,研究了磁控溅射沉积Cu膜时膜在硅衬底上成核和生长方式.Cu膜在Si衬底生长时,Cu的临界核以Volmer-Weber模式生长.溅射时,核长大增高为岛状,岛与岛相互连接构成岛的通道,最后形成连续膜.随着沉积的进行,Cu膜表面粗糙度由于晶粒凝聚和合并而增大.当形成连续致密的、具有一定晶向的Cu膜时,粗糙度反而减小.     

Growth behavior and surface topography of different silane coupling agents adsorbed on the silicon dioxide substrate (0001) for vapor phase deposition

The growth behavior and surface topography of the deposited films formed from silane coupling agents on silicon dioxide substrate (0001) via vapor phase deposition was investigated using atomic force microscopy (AFM). The surface topography of the films adsorbed on the silicon dioxide substrates is dissimilar with different silane coupling agents and different deposition conditions: (1) the films adsorbed on the silicon dioxide substrate become smoother with the increasing temperature of the silicon dioxide substrate; (2) the surface roughness of the films increases with the increasing concentration of the silane coupling agent solutions; (3) with the increasing temperature of the carrier gas, the surface roughness of the films decreases firstly and then increases; (4) with the increasing time of deposition, the surface roughness of the films increases firstly, then decreases and subsequently increases again. In experiments, the films adsorbed on the silicon dioxide substrate was rinsed ultrasonically with toluene, the results indicate that the silane coupling agent adsorbed on the substrate by physisorption and chemisorption: the chemisorbed coupling agents present island morphology and the physisorbed coupling agents are deposited on the substrate between the islands to decrease the surface roughness of the film.     

PART 2: The Influence of Solid Inclusions

Abstract

Solids in the form of colour pigments are commonly added to tablet film coats for the purpose of identification. This work examines the effect of their addition on certain mechanical properties of the films. Films were cast from aqueous solutions of hydroxypropylmethylcellulose (HPMC) in which the solids had been dispersed. Titanium dioxide was added in concentrations of up to 40% in the dried film. Two grades (regular and high tinting) of the following aluminium lakes (Colorcon Limited) were also investigated: Brilliant Blue FCF, Erythrosine and Tartrazine. A tensile test was performed on the films using an Instron test machine. In general, the addition of solid particles reduced the tensile strength of the film, shortened the elongation at break and increased the elastic modulus, i.e. the films became more brittle. The influence of storage humidity on these properties is also reported.

Changes in these fundamental properties are correlated with practical problems associated with the addition of solid particles to films. The way in which the presence of solids affects the desirable mechanical properties of tablet film coats is also discussed.