Hydroxypropylmethylcellulose (HPMC), which is available in different degrees of substitution and viscosity designations, is one of the most commonly used cellulosic polymers in aqueous film coating. It is relatively easy to process due to its non-tacky nature and has been known to produce smooth and clear films. For aqueous film coating, it is cost effective to use a coating formulation containing a high concentration of polymer without affecting the viscosity or spray rate and compromising on the quality of the film coat. Hence, it is ideal to use a polymer of low viscosity grade. The rheological properties of HPMC with various viscosity grades were determined. It was found that HPMC Methocel E3 had the lowest viscosity and was the least affected by the increase in polymer concentration. Additives can modify the film properties, including the glass transition temperature of the coating polymer. Glass transition temperature influences the viscosity of the coating solution and the mechanical properties, adhesion and permeability of the film coat. Various concentrations of different additives were incorporated in HPMC formulations to study the effect on these properties. Some long-chain fatty acids were included in the study to investigate if their hydrophobic carbon chains could retard moisture permeation of HPMC films. It was observed that HPMC films containing water-soluble additives produce films with clarity similar to those without additives, whereas those with hydrophobic additives tend to be patchy or hazy in appearance. A vinyl pyrrolidone / vinyl acetate copolymer (S630) was investigated for its influence on HPMC films, comparing the results with a commonly used plasticizer, polyethylene glycol (PEG) and another copolymer, polyvinyl alcohol (PVA). Intrinsic properties of the solutions, such as viscosity and glass transition temperature, were evaluated. / The effect of S630 on the film properties, such as physical appearance, surface roughness, moisture permeation and mechanical properties, as well as its ability to promote better adhesion of the film coat to the core surface, were compared. S630 was found to be effective both as a film-former and plasticizer, reducing the glass transition temperature and viscosity, but enhancing the tensile strength, elongation and work of failure of the cast film. The water vapour permeability was slightly increased but not to the same extent as with polyethylene glycol PEG). A 10% concentration of this copolymer increased the adhesive strength and toughness of the HPMC film coat. Aqueous film coating was carried out in the ultra-coater, using HPMC coating formulations containing 8% w/w of solids, without or with 10% concentration (based on dry weight of total solids) of the additives, PEG, polyvinyl alcohol (PVA) and S630, for coating the tablets. Capsule-shaped lactose tablet cores of specific surface area, hardness, weight, friability and disintegration time were used to study the process variables. Process variables, including air flow rate, temperature and humidity, coating application rate or pump flow rate, atomising air pressure and speed of the rotating disk, were investigated in order to obtain the optimum operating conditions for these solutions. It was found that the process parameters were similar for all the coating formulations containing 8% solid. The additives used in the coating formulations had little influence on the coating process. The ultra-coater was an effective unit for the aqueous film coating of tablets with a batch size of not less than 5 kg.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 64-70). Also available via the Internet.

L’enduction à la racle est l’un des procédés utilisés pour la fabrication des revêtements de sol. Ce procédé consiste à enduire un substrat de plastisol - une suspension de particules de PVC et de charges minérales dans une phase liquide composée de plastifiant - à l’aide d’une racle fixée au-dessus d’un cylindre entraineur. Les sols type vinyle sont fabriqués par étapes successives d’enduction. Lors de l’enduction à la racle de certains plastisols, un défaut de goutte apparait.L’apparition de ces défauts et fortement dépendante de la nature du plastisol, de la géométrie de la racle et des paramètres procédés tels que la vitesse de ligne, l’entrefer entre la racle et le cylindre etc.Cette étude a tout d’abord pour but de déterminer la rhéologie de différentes formulations de plastisol, modèles et industrielles. L’influence de la taille et la distribution des particules de PVC ainsi que l’adjonction et la taille de charges minérales sur le comportement rhéologique est étudiée.Dans un second temps, une modélisation de l’écoulement est développée afin de calculer les taux de cisaillement rencontrés sous la racle, ainsi que le champ de vitesse et les forces exercées. Ce modèle rend possible l’étude de l’influence des paramètres procédés sur les conditions d’enduction.Une étude de l’influence de ces paramètres procédés sur l’apparition du défaut est alors entreprise, en utilisant une racle pilote, pour des formulations modèles et industrielles.Enfin, des corrélations sont établies, pour ces différentes formulations, entre les conditions d’apparition du défaut, la rhéologie du plastisol et les paramètres thermomécaniques de l’écoulement sous la racle. Différents mécanismes d’apparition des défauts sont proposés. / Spread coating is one of the processes used for the manufacturing of resilient floor coverings. It consists in shearing a plastisol, a suspension of PVC particles and mineral fillers in a liquid phase composed of plasticizer and adjuvants, between a fixed knife and a rotating roll supporting a substrate. Cushion floors are made through successive coating steps. Sometimes defects in the form of droplets appear on some of the successive layers.Defect appearance is strongly dependent on the plastisol nature, on the knife geometry and on the processing parameters such as roll velocity, gap between knife and roll, etc.The study first aims at determining the rheology of several plastisol formulations, model or industrial. The influence of PVC particle size and distribution and the addition and particle size of calcium carbonate filler on the rheological behaviour is studied.In a second step, a model of the flow behaviour is developed to highlight the range of shear rates encountered between the knife and the roll, as well as the velocity field and the coating force. This model then allows the investigation of the coater process parameters influence.Then, in a third step, an investigation of the processing parameters influence on the defect appearance is done using a pilot knife-over-roll coater, with both model and industrial pastes.Finally, correlations are established between defect appearance conditions, plastisol rheology and thermomechanical parameters of the flow between knife and roll for these different plastisol formulations. Different mechanisms of this defect development are proposed.

The work in this thesis examines the effects of the application of oxide coatings on the performance of the single crystalline silicon photovoltaic solar cells. A variety of potential oxide materials for solar cells performance enhancement are investigated. These films are silicon oxide, titanium oxide and rare earth ion-doped gadolinium oxysulfide phosphor. This study compares the electrical characteristics, optical properties and surface chemical composition of mono-crystalline silicon cells before and after coating. The first study investigates the potential for using single and double layers of silicon oxide films produced by low-temperature Plasma Enhanced Chemical Vapour Deposition (PECVD) using tetramethylsilane as a silicon precursor and potassium permanganate oxidising agent for efficiency enhancement of solar cells at low manufacturing cost. Deposition of the films contributes to the increase of the conversion energy of the solar cells on one hand while the variety of colours obtained in this study can be of great importance for building-integrated photovoltaic application on the other hand. The obtained results demonstrated a relative enhancement of 3% in the conversion efficiency of the crystalline silicon solar cell. In the second study, the effects of using a single layer of titanium oxide and a stack of silicon oxide and titanium oxide on the performance of solar cell are demonstrated. Moreover, this study shows the use of different sputtering configurations and oxidation methods. The experimental results showed a relative enhancement of 1.6% for solar cells coated with a stack of silicon oxide/titanium oxide. In the third study, silicon cells were coated with a luminescent layer consisting of down-converting phosphor, gadolinium oxysulfide doped with erbium and terbium, and a polymeric binder of EVA using doctor-blade screen printing technique. A relative enhancement of 4.45% in the energy conversion efficiency of PV solar cell was achieved. Also, the effects of combining silicon oxide layers together with the luminescent composite are also presented in this study.

Recently, there has been a significant growth in the use of composites in sectors such as automotive, aerospace and wind energy. Composites are traditionally designed for mechanical performance in terms of strength, stiffness and impact energy absorption; however multifunctionality has become the focus of researchers and designers in recent years. Multifunctional design of composites involve adding functionality such as thermal management, radiation shielding, stealth, structural health monitoring and energy storage at material level rather than adding discrete components afterwards. The aim of the current research is to incorporate multi-functionality at tow-scale both as a processing aid during manufacture and adding additional functionality during subsequent processing. Various laboratory scale machines were developed as a part of this study to identify the ideal way to spread and incorporate metallic materials into the carbon fibre tows, thereby making them multifunctional. Manufacturing processes such as co-mingling of micro-fibres, coating with metallic powder and screen printing of metallic grid lines have been developed in this work. One of the objective of this thesis is to metallise carbon tow in order to use it in conjunction with magnetic tooling, as part of the chopped fibre preforming process developed by the University of Nottingham and Bentley Motors. The performance of the metallised tow has been evaluated using characterisation tests such as magnetic pull force test, bending rigidity test etc. Finite element models have been developed to verify the experimental results of magnetic pull force and bending properties. As observed during the research, the bending properties of the carbon tow were found to influence the accuracy of the finite element modelling significantly. Study into the bending properties of the carbon fibre and Multifunctional carbon tow using two different principles such as carbon tow bending under own weight and bending due to the application of an external force were carried out. In each case the governing mathematical models were also derived.

Ziel der vorliegenden Arbeit ist die Untersuchung der Methode der Laserinduzierten Plasmaspektroskopie (LIPS) zur Bestimmung des Aufmischungsgrades ([Eta]) in durch Laserstrahl-Präzisionsauftragschweißen (LAP) hergestellten Beschichtungen. Grund- und Zusatzwerkstoff müssen sich hierbei in ihrer Elementzusammensetzung voneinander unterscheiden. Als Substratmaterial diente unlegierter Baustahl, als Zusatzwerkstoff wurde Stellit 21 eingesetzt. [Eta] stellt eine wichtige Qualitätskenngröße dar und kann nach vorheriger Kalibrierung des LIPS-Messsystems sowohl offline als auch online detektiert werden. Der Aufmischungsgrad korreliert mit dem detektierten Emissionslinienverhältnis. Im untersuchten Fall besteht in guter Näherung ein linearer Zusammenhang zwischen beiden Größen. Die Vorteile von LIPS gegenüber anderen Verfahren liegen insbesondere in der berührungslosen Analyse und der entfallenden Probenpräparation. Prinzipiell lässt sich das Vorgehen auf andere Werkstoffsysteme übertragen. Das verwendete LISP-Messsystem kann in den Fertigungsprozess integriert werden und steht als Technologiemodul für eine qualifizierte Überwachung des Aufmischungsgrades beim LAP-Prozess zur Verfügung.

Applying a thin film coating is a vital strategy to enhance long term and interface stability of Ni-rich layered oxide cathode materials (NRLOs), especially when they are matched with sulfidic solid electrolytes (SSEs) in solid-state batteries (SSBs). The coating prevents direct contact between the cathode active material (CAM) and the SSE, shielding against parasitic side reactions at the cathode electrolyte interface (CEI). Conventional coatings are based on wet-chemical methods and therefore harmful to the environment and require long-lasting processing and high costs. In this study, we present a versatile, facile and highly-scalable dry-coating method (with suitable equipment up to 500 kg per batch) successfully employed for both multiand single-crystalline LiNi₇.₀Co₀.₁₅Mn₀.₁₅O₂ (NCM70) particles by fumed Li₂ZrO₃ nanostructured particles (LZONPs) via high intensity mixing process. The resulting porous coating layer stays firmly attached at the CAM particle surface without a need of post-calcination step at elevated temperatures. The electrochemical testing results signify enhanced rate capability up to 1.5 mAcm⁻² for both particle types and cyclic stability up to 650 cycles with a capacity retention of 86.1% for singlecrystalline NCM70. We attribute the enhanced performance to the reduced CEI reactions as cathodic charge transfer resistance depressed significantly after dry-coating by LZONPs, being an important step towards sulfidic solid-state batteries.

We present a novel top-electrode spray-coating process for the solution-based deposition of silver nanowires (AgNWs) onto vacuum-processed small molecule organic electronic solar cells. The process is compatible with organic light emitting diodes (OLEDs) and organic light emitting thin film transistors (OLETs) as well. By modifying commonly synthesized AgNWs with a perfluorinated methacrylate, we are able to disperse these wires in a highly fluorinated solvent. This solvent does not dissolve most organic materials, enabling a top spray-coating process for sensitive small molecule and polymer-based devices. The optimized preparation of the novel AgNW dispersion and spray-coating at only 30 °C leads to high performance electrodes directly after the deposition, exhibiting a sheet resistance of 10.0 Ω □−1 at 87.4% transparency (80.0% with substrate). By spraying our novel AgNW dispersion in air onto the vacuum-processed organic p-i-n type solar cells, we obtain working solar cells with a power conversion efficiency (PCE) of 1.23%, compared to the air exposed reference devices employing thermally evaporated thin metal layers as the top-electrode.