Annegret Potthoff

• Fraunhofer Institute for Ceramic Technologies and Systems

This paper proposes a new procedure for preparing enameled steels by thermal spraying the ceramic enamel followed by laser sintering and vitrification to obtain a smooth, corrosion-resistant, and anti-fouling coating. This study investigated the influence of enamel formulation, spraying methods, and laser parameters on the coating properties and ch...

Thermally sprayed WC-based hardmetal coatings offer high hardness, good sliding wear and abrasion performance and find large applications in mechanical engineering, valve construction, or offshore applications. WC-Co coatings are mainly produced by high-velocity oxy-fuel spraying (HVOF) from conventional spray feedstock powders. In this work, suspe...

The weathering of plastics is always accompanied by a change in surface properties, especially wettability in the case of water. For plastics weathering in an aquatic environment, wettability plays an important role in transport, sedimentation, and dispersion in the water body. To quantify wettability, contact angle measurement is a fast and conven...

Although, the number of studies focusing on potentially harmful ecotoxicological effects of microplastics is constantly increasing, there remains a lack of environmentally relevant data. Mostly uniform and pristine materials are used for toxicity testing. At the same time, there is an ongoing discussion about potential size-related effects, assumin...

Thermally sprayed WC-based hardmetal coatings offer high hardness, good sliding wear and abrasion performance and find large applications in mechanical engineering, valve construction, or offshore applications. WC-Co coatings are mainly produced by high-velocity oxy-fuel spraying (HVOF) from conventional spray feedstock powders. In our previous wor...

When compared with conventional thermal spraying processes, thermal spraying of suspensions allows to produce coatings with outstanding properties in terms of microstructure, surface topography, and phase compositions, as well as mechanical, electrical or tribological requirements. The use of suspensions as feedstock results in an almost unlimited...

- transit SO268/3 of the research vessel SONNE from Vancouver, Canada to Singapore between May 30 and July 5, 2019 - project MICRO-FATE - Characterization the fate and effects of microplastic particles between hotspots and remote regions in the Pacific ocean - construction of mesocosm on the research vessel for natural weathering of polymers under...

In the context of environmental plastic pollution, it is still under debate if and how the "plastisphere", a plastic-specific microbial community, emerges. In this study, we tested the hypothesis that the first conditioning film of dissolved organic matter (DOM) sorbs selectively to polymer substrates and that microbial attachment is governed in a...

Thermally sprayed WC-Co coatings provide excellent wear resistance and corrosion protection under heavy loads, but their application usually involves additional grinding and polishing steps, which can be 3-4 times costlier than the spraying process itself. There is thus the motivation to develop a process that produces smooth, near-net-shape carbid...

We described in 2017 how weathering plastic litter in the marine environment fulfils two of three criteria to impose a planetary boundary threat related to “chemical pollution and the release of novel entities”: (1) planetary-scale exposure, which (2) is not readily reversible. Whether marine plastics meet the third criterion, (3) eliciting a disru...

It is becoming increasingly important to develop assessment criteria for the quality of nanoplastics studies. This study is an attempt to establish such criteria based on those developed for engineered nanomaterials, the GUIDEnano and DaNa criteria being two representatives. These criteria were applied to studies on polystyrene nanoparticles (PS NP...

Microplastics remain on everyone's lips - but particularly on those of aquatic organisms. Plastic particles are ubiquitous in the environment. Recent scientific studies indicate that most of the plastic particles present in the ocean are transported from land via rivers into the sea (Rochman 2018). During the transportation process plastic debris i...

Microplastics remain on everyone's lips - but particularly on those of aquatic organisms. Plastic particles are ubiquitous in the environment. Recent scientific studies indicate that most of the plastic particles present in the ocean are transported from land via rivers into the sea (Rochman 2018). During the transportation process plastic debris i...

Compositions in the system Cr2O3-TiO2-Al2O3 are among the most used ceramic materials for thermally sprayed coating solutions. Cr2O3 coatings present good sliding wear resistance; Al2O3 coatings show excellent insulation behavior and TiO2 striking corrosion properties. In order to combine these properties, coatings containing more than one oxide ar...

Cr2O3-based coatings offer high hardness, excellent sliding wear performance, and corrosion resistance. Therefore, they are widely applied in the paper industry, as well as for pumps and mechanical sealing systems. Compared to the conventional spray processes, the technology of suspension-HVOF spraying (S-HVOF) allows the production of dense, finel...

Next to ZrO2, compositions in the system Cr2O3-TiO2-Al2O3 are the most used ceramic materials for thermally sprayed coating solutions. Cr2O3 coatings present good sliding wear resistance, Al2O3 coatings show excellent insulation behaviour and TiO2 striking corrosion properties. In order to combine these properties, coatings containing more than one...

The rapid development of nanotechnologies and increased production and use of nanomaterials raise concerns about their potential toxic effects for human health and environment. To evaluate the biological effects of nanomaterials, a set of reliable and reproducible methods and development of standard operating procedures (SOPs) is required. In the f...

Advanced coatings with improved properties have been developed by spraying water-based Cr2O3 suspensions with High Velocity Oxygen Fuel Spraying (S-HVOF). In comparison to conventionally sprayed coatings, suspension sprayed coatings show denser microstructure, reduced surface roughness, improved mechanical properties and corrosion resistance, as we...

The presence of microplastic (MP) in the aquatic environment is recognized as a global-scale pollution issue. Secondary MP particles result from an ongoing fragmentation process governed by various biotic and abiotic factors. For a reliable risk assessment of these MP particles, knowledge about interactions with biota is needed. However, extensive...

Plastic in the global oceans fulfills two of the three conditions for pollution to pose a planetary boundary threat because it is causing planetary-scale exposure that is not readily reversible. Plastic is a planetary boundary threat if it is having a currently unrecognized disruptive effect on a vital Earth system process. Discovering possible unk...

The zebrafish (Danio rerio) embryo (ZFE) is an established test organism to investigate the toxicity of chemicals and is suitable to assess the hazardous potential of nanoparticles. There is little knowledge on metal internalization and distribution in these organisms, as well as on the underlying kinetic processes. To shed light on metal-ZFE inter...

Current activities and first results of the JPI-Oceans funded WEATHER-MIC project

Within the FP7 EU project NanoValid a consortium of six partners jointly investigated the hazard of silver nanoparticles (AgNPs) paying special attention to methodical aspects that are important for providing high-quality ecotoxicity data. Laboratories were supplied with the same original stock dispersion of AgNPs. All partners applied a harmonised...

During the last decade, nanomaterials (NM) were extensively tested for potential harmful effects towards humans and environmental organisms. However, a sound hazard assessment was so far hampered by uncertainties and a low comparability of test results. The reason for the low comparability is a high variation in the (1) type of NM tested with regar...

Research and development work for about one decade have demonstrated many unique thermal spray coating properties, particularly for oxide ceramic coatings by using suspensions of fine powders as feedstock in APS and HVOF processes. Some particular advantages are direct feeding of fine nano- and submicron-scale particles avoiding special feedstock p...

Chromium (III)-oxide (Cr2O3) is a widely used coating material for applications in the printing, paper and textile industry, pumps and mechanical sealing systems. Cr2O3 coatings offer high hardness, excellent sliding wear performance and corrosion resistance. Suspension-HVOF process (S-HVOF) allows the production of dense, finely structured coating...

The application of nanoscale zero-valent iron (nZVI) for subsurface remediation of groundwater contaminants is a promising new technology, which can be understood as alternative to the permeable reactive barrier technique using granular iron. Dechlorination of organic contaminants by zero-valent iron seems promising. Currently, one limitation to wi...

Tribomechanical properties of nanostructured coatings deposited by suspension high velocity oxy-fuel (S-HVOF) and conventional HVOF (Jet Kote) spraying were evaluated. Nanostructured S-HVOF coatings were obtained via ball milling of the agglomerated and sintered WC-12Co feedstock powder, which were deposited via an aqueous-based suspension using mo...

Sliding wear evaluation of nanostructured coatings deposited by Suspension HighVelocity Oxy-Fuel (S-HVOF) and conventional HVOF (JetKote (HVOF-JK) and JP5000 (HVOF-JP)) spraying were evaluated. S-HVOF coatings were nanostructured and deposited via an aqueous based Suspension of the WC–Co powder, using modified HVOF (TopGun) spraying. Microstructura...

The increasing use of zinc oxide (ZnO) nanoparticles in sunscreens and other cosmetic products demands a risk assessment that has to be done in toxicological studies. Such investigations require profound knowledge of the behavior of ZnO in cell culture media. The current study was performed to get well-dispersed suspensions of a hydrophilic (ZnO-hy...

Nanoscale zero-valent iron (nZVI) has recently gained great interest in the scientific community as in situ reagent for installation of permeable reactive barriers in aquifer systems, since nZVI is highly reactive with chlorinated compounds and may render them to harmless substances. However, nZVI has a high tendency to agglomerate and sediment; th...

Suspensions used as feedstocks for atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) spraying enable coatings with a wide variety of thicknesses, morphologies, and properties to be produced. The economic efficiency of the process depends on the availability of suitable additional system components, e.g., suspension feeder and inje...

Photocatalytic properties of titania have been studied very intensively for a variety of applications, including air and water purification. In order to clarify the influence of the phase composition and other parameters, thermal spraying with suspensions was applied to produce photocatalytically active titania coatings starting from two commercial...

Toxicological testing of nanomaterials often involves in vitro studies of nanoscale powders, which, therefore, need to be dispersed. Various dispersion approaches have been described in the literature, with the main differences between them being the sonication method, the medium, and the additives used. In the present study, five dispersion approa...

Suspensions used as feedstocks for atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) spraying enable coatings with a wide variety of thicknesses, morphologies, and properties to be produced. The economic efficiency of the process depends on the availability of suitable additional system components, e.g., suspension feeders and inj...

This paper presents and describes the interactions occurring in polyvinyl-alcohol-containing alumina suspensions containing different multivalent cations. The influence ofMg(+II), Ca (+II), Al (+III) and Zr (+IV) cations was studied systematically by means of surface potential, viscosity, sedimentation and adsorption measurement techniques. The res...

In this work the microstructural characteristics and electrical insulating properties of thermally sprayed alumina coatings produced by suspension-HVOF (S-HVOF) and conventional HVOF spray processes are presented. The electrical resistance at different relative air humidity (RH) levels (from 6 to 97% RH) and values of dielectric strength were inves...

Tungsten carbide (WC) and cobalt (Co) are constituents of hard metals and are used for the production of extremely hard tools. Previous studies have identified greater cytotoxic potential of WC-based nanoparticles if particles contained Co. The aim of this study was to investigate whether the formation of reactive oxygen species (ROS) and micronucl...

The influence of initial pH and energy input during suspension homogenization on the stabilizing performance and coordination type of commercial available polyacrylate dispersant were studied. Additionally to widely used rheology and electroacoustic measurement techniques the alumina suspensions were analysed with centrifugal separation and in situ...

One task in risk assessment of engineered nanoparticles is toxicological studies. A suitable interpretation of these investigations demands a comprehensive physical-chemical characterization. Here, we present an approach to gain well-dispersed nanoparticles in physiological media. Therefore, a step-by-step procedure is demonstrated on two different...

The study investigated the deagglomeration of spinel nanopowders (MgO·nAl2O3, n≈1) from different syntheses in correlation with their resulting performance on green processing and sintering. Transmission results are addressed as a means of evaluating the degree of last pore elimination. As a result, clear transparent components with a thickness of...

Cellular internalisation of industrial engineered nanoparticles is undesired and a reason for concern. Here we investigated and compared the ability of seven different mammalian cell cultures in vitro to incorporate six kinds of engineered nanoparticles, focussing on the role of cell type and particle properties in particle uptake. Uptake was exami...

Palladium/magnetite nanoparticulate catalysts were developed for efficient elimination of halogenated organic pollutants from contaminated wastewater. Particle recovery from treated water can be ensured via magnetic separation. However, in worst-case scenarios, this catalyst removal step might fail, leading to particle release into the environment....

Toxicological investigations on nanoparticles require a comprehensive physico-chemical characterization to get useful information about the powder as well as the behavior of the suspended nanoparticles in water and physiological media. Therefore, we characterized the often used TiO(2) P25 and developed procedures to get stable, homogeneous, and wel...

To assess potential health risks of nanoparticles by means of in vitro or in vivo assays and to determine dose-action curves a defined and reproducible method of particle administration is required. The interpretation of the toxicological results should be based on a comprehensive chemical-physical characterization of the particles used. Therefore,...

Due to their increased production and use, engineered nanoparticles are expected to be released into the aquatic environment where particles may agglomerate. The aim of this study was to explore the role of agglomeration of nanoparticles in the uptake and expression of toxicity in the rainbow trout (Oncorhynchus mykiss) gill cell line, RTgill-W1. T...

Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobalt-doped tungste...

The increasing use of nanoparticles makes it necessary to check up possible toxicological risks of this new materials class. In this paper we describe on two nanopowders (tungsten carbide, titanium nitride) which methods and parameters of a chemical-physical characterization are needed in forefront of toxicological experiments. This includes invest...

Electrosteric and electrostatic stabilization of a commercially available boehmite powder in water was investigated for the purpose of performing milling experiments to reduce the particle size to the nanoscale range. The effect of commercially available dispersing agents based on polyacrylic acid as well as nitric and acetic acid on the particle p...

Little research has to date been done to evaluate the impact of nanoparticles on the environment and humans, despite their use in products such as cosmetics, paint and tyres. Experience with other emerging technologies has shown that they are only accepted by society if possible health effects are analysed and published at an early stage of develop...

The use of nano zerovalent iron (nZVI) for environmental remediation is a promising new technique for in situ remediation. Due to its high surface area and high reactivity, nZVI is able to dechlorinate organic contaminants and render them harmless. Limited mobility, due to fast aggregation and sedimentation of nZVI, limits the capability for source...

The quality of milling product is determined by size distribution and contaminations, resulting from particle-bead contact (mass and size of bead abrasion) and particle - wall contact. Increase of energy in bead mills will decrease the milling time but increase the bead attrition. This interaction was investigated by comminution of an aqueous alumi...

The production of nanoparticles can follow two routes: the bottom-up synthesis and the top-down production via milling of a coarse powder in a ball mill. The possible reduction ratio of the particle size during grinding strongly depends on the stabilisation of the particles in the slip to prevent agglomeration. In-depth knowledge of the interaction...

According to ISO/TC 229, nanomaterials represent structures whose units are usually smaller than 100 nm. In order to recognize size-related risks of these new materials early, toxicological studies have to be conducted at nanoparticles. A relevant assessment for the interpretation of toxicological examinations requires the comprehensive chemical-ph...

Meißner, T. ; Potthoff, A. ; Richter, V.: Physico-chemical characterization in the light of toxicological effects. Inhalation Toxicology 21 (2009), Nr.S1, S.35-39 On page 35, the keywords were incorrectly given, and should read: "Keywords: nanoparticles; toxicity; TiO2; characterization; suspension".