
Michael FischlschweigerClausthal University of Technology | TUC · Chair of Technical Thermodynamics and Energy Efficient Material Treatment
Michael Fischlschweiger
Professor
About
86
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Introduction
Professor of Technical Thermodynamics and Energy Efficient Material Treatment at Clausthal University of Technology. Basic research: Thermodynamics and Mechanics of Materials, Non-Equilibrium Thermodynamics and Statistical Field Theory; Applied research: Crystallization of polymers and minerals, Energy conversions in materials and kinetics of phase transitions, Thermal energy storage and PCM, Recycling process simulation and intensification (polymer, minerals)
Additional affiliations
July 2019 - present
Publications
Publications (86)
In response to climate change mitigation efforts, improving the efficiency of heat networks is becoming increasingly important. An efficient operation of energy systems depends on faultless performance. Following the need for effective fault detection and elimination methods, this study suggests a three-step workflow for increasing automation in ma...
This manuscript presents the results from the synthesis and characterization of a slag analogue with a nominal composition of 17 wt% LiMnO2 and 83 wt% Ca2SiO4 encountering fairly high cooling rates in order to study the evolution of Mn-species. The Mn species was also simulated from 1223 K to 1773 K using a thermodynamic model, assuming a homogeneo...
The challenge of obtaining sufficient raw materials is a major concern when it comes to extracting lithium from spent lithium-ion batteries. One way to address this is through pyrometallurgical processing, which leaves undesirable elements such as lithium, aluminum and manganese in the slag. The engineered artificial minerals approach focuses on th...
Pyro-metallurgical processing technology is widely used in the spent lithium-ion batteries recycling to recover valuable metals such as cobalt, nickel and copper, while lithium primarily remains in the slag. The effective valorization of slag, especially lithium recovery, constitutes a significant issue in contemporary pyrometallurgical processes d...
The relationship between macromolecular architecture and crystallization properties is a relevant research topic in polymer science and technology. The average degree of crystallinity of disperse polymers is a well-studied quantity and is accessible by various experimental methods. However, how the different macromolecular species contribute to the...
A better understanding of high temperature processes in slags contributes to facilitate knowledge based design of the solidified product. Here, a slag analogue with a nominal composition of 17 wt% LiMnO2 and 83 wt% Ca2SiO4 was synthesized encountering fairly high cooling rates. The Mn species from 1223 K to 1773 K was simulated using a thermodynami...
Engineered artificial minerals (EnAMs) are the core of a new concept of designing scavenger compounds for the recovery of critical elements from slags. It requires a fundamental understanding of solidification from complex oxide melts. Ion diffusivity and viscosity play vital roles in this process. In the melt, phase separations and ion transport g...
During liquid–solid transformation, bulk mass and thermal diffusion, along with the evolved interfacial latent heat, work in tandem to generate interfacial thermodynamic and kinetic forces, the interplay of which decides the solidification velocity and consequently the solidified phase attributes. Hence, access to interface dynamics information in...
The growing demand for lithium-ion battery (LIB) applications highlights the need for innovative recycling strategies in the context of circular economy. Combined
pyrometallurgical and hydrometallurgical processing routes are gaining more and more attention for lithium recovery. However, further enhancing lithium recycling efficiency is still a gr...
Developing efficient recycling processes with high recycling quotas for the recovery of graphite and other critical raw materials contained in LIBs is essential and prudent. This action holds the potential to substantially diminish the supply risk of raw materials for LIBs and enhance the sustainability of their production. An essential processing...
The Li-Mn-O system is a crucial constituent of cathode materials used in lithium-ion batteries (LIBs). Numerous research teams have focused on enhancing its electrochemical properties and thermal stability at lower temperatures to develop high-performance cathode materials. However, in the recycling of LIBs in pyrometallurgical processing, the high...
The solubility of gases in semicrystalline polymers is a significant property with numerous applications, such as gas-phase polymerization. Although thermodynamic modeling has successfully determined gas solubility in glassy polymers or polymer melts without crystallites, predicting gas solubility in polymers with a semicrystalline morphology remai...
This study investigates the effect of the macromolecular architecture of poly(vinylidene fluoride) (PVDF) on its thermally induced phase separation (TIPS) behavior and polymorphic crystallization in the PVDF/γ-butyrolactone (PVDF/γ-BL) system. Preparative PVDF fractions with specific macromolecular architecture and phase constitution are generated....
Understanding the structure-property-process relationships in pyrolysis-based recycling of polymers offers new possibilities, like, energy-efficient process designs and tailored products. With the consideration of sample size as well as thermal rate effects, the influence of the molecular weight distribution of polystyrene on the pyrolysis kinetics...
Lithium-ion-battery (LIB) recycling through a combined pyro- and hydrometallurgical route is an appropriate method to process batteries with a wide range of cell chemistries and sizes. Copper, Co and Ni are already recovered on an industrial scale by this process route, whereas Li is not. Lithium, Al and Mn are transferred into Ca- and Si-rich slag...
Thermal energy storages represent important devices for the decarbonisation of heat; hence, enabling a circular economy. Hereby, important tasks are the optimisation of thermal losses and providing a tuneable storage capacity, as well as tuneable storage dynamics for thermal energy storage modules which are composed of either sensible or phase chan...
Due to its high energy density combined with lightweight construction, the demand of Li-ion batteries (LIBs) in the field of portable devices, hybrid and batteries driven vehicles is continuously increasing. However, the enormous growth of LIBs manufacturing arises the challenge of recycling the lithium from LIBs after reaching their end of Life. T...
The pyrometallurgical recycling route is essential for recovering valuable metals from spent lithium-ion batteries (LIBs) due to its large processing capacity and ability to handle a broad range of input materials [1]. Besides the recovery of metals such as cobalt and nickel, the effective recovery of lithium from the by-product - lithium-bearing s...
New developments of energy-efficient recycling processes and systems for LIB recycling are required from the perspective of resource circulation, raw material supply and sustainability. One promising approach is based on a combined pyro- and hydrometallurgical treatment. However, tailoring respective slag compositions and processing conditions is a...
Polymer blends made of plastic waste and manufactured by extrusion‐based melt blending are of particular importance for mechanical recycling in the context of tailoring material properties for value‐added applications. For both, property tailoring and for suppressing downcycling, it is inevitable to understand the thermomechanical degradation behav...
Outstanding electroactive properties of certain crystallographic phases of poly(vinylidene fluoride) (PVDF) bring much attention to its melting and crystallisation behaviour for tailoring crystallographic nature. In the past, the focus was put on operating conditions in terms of melting and crystallisation kinetics, whereas a deeper understanding o...
Outstanding electroactive properties of certain crystallographic phases of poly(vinylidene fluoride) (PVDF) bring much attention to its melting and crystallisation behaviour for tailoring crystallographic nature. In the past, the focus was put on operating conditions in terms of melting and crystallisation kinetics, whereas a deeper understanding o...
In this work, a thermodynamic model is developed based on continuous thermodynamics and lattice cluster theory to describe solid–liquid equilibria of polymer–solvent systems, where the polymer shows a certain molecular architecture, semi-crystallinity, and a continuous molecular weight distribution. The new thermodynamic model is validated by predi...
The influence of heat transfer on the solvent absorption kinetics of an epoxy o-cresol novolac resin composite which is applied for the encapsulation of heat emitting devices is investigated theoretically. The fundament of the model is the PC-SAFT equation of state which is extended by a network term for including the arising elastic forces in the...
Gas solubility is an important thermodynamic property, which is crucial for understanding e.g., foaming of polymers, gas removal of materials as well as gas storage. The structure of the polymer and the system conditions influence the solubility strongly. For predicting and understanding gas sorption, consistent thermodynamic models accompanied wit...
Ultrasonic degradation of polymers attracts more and more attention in the field of chemical recycling of polymers due to the promising opportunity to tailor molecular weight and polydispersity of the gained polymer fragments. In this work, the influence of solvent, gas atmosphere, and ultrasound amplitude on the ultrasonic degradation process of p...
In the field of rehabilitation and neuroscience shape memory alloys play a crucial role as lightweight actuators. Devices are exploiting the shape memory effect by transforming heat into mechanical work. In rehabilitation applications, dynamic loading of the respective device occurs, which in turn influences the mechanical consequences of the phase...
The recovery of critical elements in recycling processes of complex high‐tech products is
often limited when applying only mechanical separation methods. A possible route is the
pyrometallurgical processing that allows transferring of important critical elements into an alloy
melt. Chemical rather ignoble elements will report in slag or dust. Va...
The extraordinary properties of shape memory NiTi alloy are combined with the inherent viscoelastic behavior of a silicon elastomer. NiTi wires are incorporated in a silicon elastomer matrix. Benefits include features as electrical/thermal conductivity, reinforcement along with enhanced damping performance and flexibility. To gain more insight of t...
Epoxy resins are often applied to prevent sensitive electronics to come into contact with solvents. Therefore, it is necessary to know the diffusion through the epoxy resins to determine the thickness of the epoxy resins layer for different applications. In this work a diffusion model is developed on the basis of the Perturbed-Chain Statistical Ass...
The solvent absorption of an epoxy o-cresol novolac resin composite has been measured in different aqueous electrolyte solutions (NaCl, CaCl2 and MgCl2) at different salt concentrations from 0.1 to 0.3 mg/l. Next to the total solvent uptake, which was measured by a gravimetric measurement, the absorption of ions was determined by ion chromatography...
Damage and fiber misalignment of woven fabrics during discontinuous polymer processing remain challenging. To overcome these obstacles, a promising switchable elastomeric adherence gripper is introduced here. The inherent surface tackiness is utilized for picking and placing large sheets. Due to the elastomer’s viscoelastic material behavior, the s...
Damage and fibre misalignment of woven fabrics during discontinuous polymer processing remain challenging. To overcome these, a promising switchable elastomeric adherence gripper is introduced here. The inherent surface tackiness is utilized for picking and placing large sheets. Due to the elastomer’s viscoelastic material behavior, the surface pro...
The solvent uptake in equilibrium of a highly cross-linked epoxy o-cresol novolac resin in water, isopropanol and heptane was experimentally measured and modeled with the PC-SAFT equation of state. As suggested in literature, PC-SAFT was combined with a network term which takes additional elastic forces into account. The model parameters of the epo...
Solubility of gases in polymers plays a crucial role in several industrial sectors. This spans from chemical, pharmaceutical to polymer industry. While, in last years thermodynamic models have been successfully developed to predict the solubility of fluids in polymers, which are above the melting temperature or in a glassy state, thermodynamic mode...
Impact of Polymer Characteristics On Thermodynamic Properties
Polymers play an essential role in drug formulation and production of medical devices, implants, and diagnostics. Following drug discovery, an appropriate formulation is selected to enable drug delivery. This task can be exceedingly challenging owing to the large number of potential delivery methods and formulation and process variables that can in...
While the use of active thermography for non-destructive testing supplies valuable information on component quality, the measurement results are still very often evaluated manually. Ottronic now presents a method that automatically classifies and interprets measured data. Active thermography is thus paving the way for intelligent, self-optimised pr...
In the field of rehabilitation and neuroscience shape memory alloys play a crucial role as lightweight actuators. Devices are exploiting the shape memory effect by transforming heat into mechanical work. In rehabilitation applications, dynamic loading of the respective device occurs, which in turn influences the mechanical consequences of the phase...
Thermoplastic polymer matrix composites with continuous carbon fibre reinforcements are of crucial relevance in automotive industry. The mix of high performance and cost effective manufacturing makes them attractive for high volume production. However, it could be shown that production integrated end of line quality control is of strong importance...
Analytical polymer separation techniques, like CRYSTAF (crystallization analysis fractionation) and TREF (temperature rising elution fractionation), play a crucial role in gaining insight into the interrelation between molecular architecture and properties. Often polymer samples are semicrystalline, as it consists of amorphous regions which exhibit...
Shear behaviour of a glass fibre/polypropylene composite is characterized over a wide range of strain rates and forming temperatures using the bias extension test. A temperature- and rate-dependent material model is here introduced to describe the observed behaviour. The model is based on a continuous approach and formulated considering a stress ob...
Recently, Lattice Cluster Theory has been applied to predict liquid–liquid equilibria and solid–liquid equilibria of low and high molecular weight mixtures taking into account the molecular architecture and the nature of crystallinity of the respective component. Herein, an LCT-based theory is applied to calculate solid–liquid–liquid equilibrium of...
The solid–liquid equilibrium (SLE) of hydrocarbon mixtures is highly relevant in petroleum and chemical industry. The formulation of thermodynamic models with a high accuracy in predicting solid–liquid phase behavior is an essential and also a challenging topic. In this publication, the authors applied Lattice Cluster Theory for predicting the SLE...
A methodology to calculate surface strains from a rectangular grid placed on a forming blank is introduced. This method consists of treating the grid points as nodes of a finite element (FE) model and assigning elements to the grid. The strains are then computed following FE analysis. If higher order elements are used, also more information within...
The influence of fiber orientation and mold geometry variations on the reactive polymerization of ϵ-caprolactam during the mold filling phase in reactive processing is depicted in this work with the help of Computational Fluid Dynamics (CFD). Therefore the established Malkin kinetics is employed to describe the polymerization process combined with...
Chain architecture and degree of crystallinity of polymers strongly influence the solid–liquid equilibrium of binary polymer solvent systems. Especially, for explaining the principle of common polymer separation techniques a fair prediction of solid–liquid equilibria of polymer solvent systems is of crucial importance. Herein, based on the framewor...
Failure of single-lap joints of carbon fibre tapes manufactured by thermoforming
was characterized, with special regard of the effect of forming pressure and overlap geometry
on the ultimate tensile strength. Introducing forming pressure dependent strength parameters,
the impact of the structural alterations induced by the forming stage on the asse...
In this work, an old theory for the melting of linear, semi-crystalline polymers, developed by Flory in 1949, is rediscovered and extended to branched polymers. The extension is realised by the incorporation of the lattice cluster theory, which is able to model polymers with an arbitrary architecture. The final working equation describing the melti...
Unidirectional tape-placement technologies appeared as a promising alternative due to their potential in large-scale component production. While the optimization strategies used to define the tape lay-out can be of different nature, the utilization of tape-to-tape joints is inevitable. Whereas several studies have focussed their efforts on the proc...
In order to describe the influence of a flowing system on the anionic polymerization of ϵ-Caprolactam, a model comprising of classical Malkin kinetics which is embedded in the framework of computational fluid dynamics (CFD) is established and validated with results from different experimental setups, which cover different polymerization temperature...
In this work, the activity coefficients and the solubility of amino acids in water were calculated using the lattice cluster theory (LCT) combined with the extended chemical association lattice model allowing self-association as well as cross-association. This permits the study of the influence of the amino acids structure on the thermodynamic prop...
Anisotropic composite material properties require special designing capabilities to fully exploit the remarkable properties in longitudinal fibre direction for stiffness and strength improvement. Therefore an optimisation scheme with hierarchical structuring of an optimality criterion based orientation optimisation and a gradient based technique fo...
The infrared radiator meets the requirements for heating organic sheet and other semi-finished products with thermoplastic matrix systems economically, gently and flexibly. In combination with a tailored control system, a large bandwidth of materials and semi-finished product thicknesses can additionally be covered. Where there are limits on the he...
In the present study a new phase fraction based transformation hardening and further a stress and temperature dependent transformation kinetics following the postulates in internal variable thermodynamics is presented. The generally formulated kinetics equation is applied to describe the progress of phase transformation in a Cr-Ni-Mo-Al-Ti maraging...
To study martensitic phase transformation we use a micromechanical model based on statistical mechanics. Employing lattice Monte-Carlo simulations with realistic material properties for shape-memory alloys (SMA), we investigate the combined influence of the external stress, temperature, and interface energy between the austenitic and martensitic ph...
A continuum mechanical visualisation for the formation of a wedge to explain plasticity-induced crack closure under plain strain conditions is based on a material transport from the crack wake to the crack tip. A 2-dimensional finite element analysis is used to confirm this explanation of plasticity-induced crack closure under plain strain conditio...
A viable model for the phenomenon of transformation induced plasticity must be able to predict the strain response to arbitrary, also non-proportional loading paths. The constitutive model presented in this paper is interfacing between the macro- and the mesoscale by stress partitioning in the parent and product phase, using a nonlinear scale trans...
Modeling martensitic phase transformation in SMAs has become a key to understand the transformation behavior in terms of their temperature and stress response. In the present work a new method based on a statistical physics concept has been developed for the description of transformation kinetics, total strain and their rates in polycrystalline sol...
Hysteretic behaviour of shape memory alloys (SMAs) is highly important for design and applicability of these materials in active structural elements like rods. Especially the damping performance of SMAs depend strongly on their hysteretic characteristics. Experimental investigations show the influences of stress on the hysteretic cycle. The current...
A novel theoretical approach modeling martensitic phase transformation is demonstrated in the present study. The generally formulated model is based on the block-spin-approach and on renormalization in statistical mechanics and is applied to a representative volume element which is assumed to be in a local thermodynamic equilibrium. Using fundament...
The interaction between martensitic phase transformation (MPT) and plasticity is highly relevant for describing the thermomechanical behavior of maraging steels. Contrary to materials undergoing coherent phase transformations the challenge of modeling maraging steels is the generation of plastic strains through high internal stresses triggered by M...
Understanding martensitic phase transformation (MPT) is of crucial importance for many engineering applications. Especially in polycrystalline
shape memory
alloys and steels one can observe phase transformations on several length and time scales. Those are firstly the atomistic length scale (nano scale, nm) and the scale of the crystallites (micr...
Martensitic phase transformation can be classified as displacive solid -solid phase transformations, where the symmetry of the high temperature phase (austenite) breaks when phase transformation occurs. The martensitic phase (low temperature phase ) and its variants are products of symmetry breaking in solids. Based on a quasiparticle statistical m...
The importance of smart materials e.g. shape memory alloys (SMAs) for technological applications has been growing during the last 20 years. Especially modeling SMAs behavior has become of high interest in materials science for the prediction of macroscopic effects like pseudoelasticity. The key for their behavior is a displacive solid - solid phase...
Current strategies in modeling shape memory alloy (SMA) behavior follow either the concept of classical irreversible thermodynamics or the methodology of phenomenological approaches at the micro as well as at the macro space scale. The objective of the present study is to show a new approach in modeling SMA's by using a statistical physics concept...
Blends of a random poly(propylene) copolymer with different types of polyethylene were used to develop a sample independent statistic mathematical model which describes the quality of phase separation of polymer blends obtained by CRYSTAF. By coupling the abstract model with experimental data, process parameters influencing the non‐equilibrium CRYS...