@article{63800, abstract = {{In this contribution, we address the estimation of the frequency-dependent elastic parameters of polymers in the ultrasound range, which is formulated as an inverse problem. This inverse problem is implemented as a nonlinear regression-type optimization problem, in which the simulation signals are fitted to the measurement signals. These signals consist of displacement responses in waveguides, focusing on hollow cylindrical geometries to enhance the simulation efficiency. To accelerate the optimization and reduce the number of model evaluations and wait times, we propose two novel methods. First, we introduce an adaptation of the Levenberg–Marquardt method derived from a geometrical interpretation of the least-squares optimization problem. Second, we introduce an improved objective function based on the autocorrelated envelopes of the measurement and simulation signals. Given that this study primarily relies on simulation data to quantify optimization convergence, we aggregate the expected ranges of realistic material parameters and derive their distributions to ensure the reproducibility of optimizations with proper measurements. We demonstrate the effectiveness of our objective function modification and step adaptation for various materials with isotropic material symmetry by comparing them with the Broyden–Fletcher–Goldfarb–Shanno method. In all cases, our method reduces the total number of model evaluations, thereby shortening the time to identify the material parameters.}}, author = {{Itner, Dominik and Dreiling, Dmitrij and Gravenkamp, Hauke and Henning, Bernd and Birk, Carolin}}, issn = {{0888-3270}}, journal = {{Mechanical Systems and Signal Processing}}, keywords = {{Material parameter estimation, Waveguide, Nonlinear optimization, Inverse problem, Least squares}}, pages = {{113904}}, title = {{{A modified Levenberg–Marquardt method for estimating the elastic material parameters of polymer waveguides using residuals between autocorrelated frequency responses}}}, doi = {{https://doi.org/10.1016/j.ymssp.2026.113904}}, volume = {{247}}, year = {{2026}}, } @article{64916, abstract = {{The joining of dissimilar materials, such as steel and aluminum, entails significant challenges during thermal curing processes due to differing coefficients of thermal expansion. This study addresses the formation of “viscous fingering” instabilities in structural adhesive joints, which are induced by thermally driven relative displacements during the liquid phase of the adhesive. Using a component-like specimen “bridge specimen,” the dependency of this phenomenon on process temperature and structural stiffness (rivet distance) was characterized. Experimental results reveal that while the relative displacement scales cubically with the free buckling length, the resulting adhesive area reduction follows an exponential trend, leading to a loss of effective bond area of up to 79%, which significantly compromises the joint strength in automotive applications. To predict these process-induced defects, a thermo-chemo-viscoelastic-viscoplastic adhesive model implemented in LS-DYNA was applied. The model combines curing kinetics, viscoelastic relaxation, and pressure-dependent plasticity and features a geometric damage parameter (D) that captures the adhesive area reduction caused by viscous fingering as an exponential function of the accumulated normal strain in the liquid phase. This damage parameter, calibrated on base-specimen level, was transferred to the component geometry. The simulation demonstrated high predictive accuracy with a maximum deviation of the adhesive area reduction of 3.1% compared to experimental data. This validates the model’s capability to predict manufacturing-induced damage in complex hybrid structures solely based on thermal boundary conditions.}}, author = {{Al Trjman, Mohamad and Beule, Felix and Teutenberg, Dominik and Meschut, Gerson and Riese, Julia}}, issn = {{0021-8464}}, journal = {{The Journal of Adhesion}}, keywords = {{Adhesive area reduction, CED coating process, delta alpha problem, epoxy structural adhesive, influence of manufacture, multi-material design, numerical simulation (FEM), relative displacements, viscous fingering (saffman-taylor-instability).}}, pages = {{1--24}}, publisher = {{Informa UK Limited}}, title = {{{Experimental characterization and numerical analysis of the influence of the CED coating process on viscous fingering formation in hybrid-jointed mixed structures}}}, doi = {{10.1080/00218464.2026.2644394}}, year = {{2026}}, } @article{43464, abstract = {{Lightweight design is a common approach to reduce energy demand in the use stage of vehicles. The production of lightweight materials is usually associated with an increase in energy demand, so the environmental impacts of lightweight structures need to be assessed holistically using a life cycle assessment. To estimate the life cycle environmental impacts of a product in its developmental stage, for example, by life cycle engineering, future changes in relevant influencing factors must be considered. Prospective life cycle assessment provides methods for integrating future scenarios into life cycle assessment studies. However, approaches for integrating prospective life cycle assessment into product development are limited. The objective of this work is to provide the methodological foundation for integrating future scenarios of relevant influencing factors in the development of lightweight structures. The applicability of the novel methodology is demonstrated by a case study of a structural component in a steel, aluminium, and hybrid design. The results show that appropriate decarbonisation measures can reduce the life cycle greenhouse gas emissions by up to 95 percent until 2050. We also found that shifts in the environmentally optimal design are possible in future scenarios. Therefore, the methodology and data provided contribute to improved decision-making in product development.}}, author = {{Ostermann, Moritz and Grenz, Julian and Triebus, Marcel and Cerdas, Felipe and Marten, Thorsten and Tröster, Thomas and Herrmann, Christoph}}, issn = {{1996-1073}}, journal = {{Energies}}, keywords = {{Life Cycle Engineering, Life Cycle Assessment, Lightweight Design, Prospective LCA, Future-oriented LCA, Energy System, Material production, Sustainable production}}, number = {{8}}, publisher = {{MDPI AG}}, title = {{{Integrating Prospective Scenarios in Life Cycle Engineering: Case Study of Lightweight Structures}}}, doi = {{10.3390/en16083371}}, volume = {{16}}, year = {{2023}}, } @article{43046, abstract = {{In the laser sintering technology, the semi-crystalline polymer material is exposed to elevated temperatures during processing, which leads to serious material ageing for most materials. This has already been investigated intensively by various authors. However, the ageing of the material at ambient temperatures during shelf life has not been the focus so far. The need to analyse the shelf life can be derived from an ecological and economic point of view. This work is focusing on the shelf life of PA2200 (PA12). To reduce the potential influences of powder production fluctuations, two different powder batches stored for 5.5 years and 6.5 years are investigated and compared to a reference powder produced 0.5 years before these investigations. Multiple powder analyses and part characterisations have been performed. A significant yellowing and molecular chain length reduction can be derived from the measurement results. Whereas the influence on mechanical part performance was minor, the parts built with the stored powders are more yellowish. As it is most likely that this is due to the consumption of polyamide stabilisers, it can be assumed that these parts will be subject to significantly faster ageing. Therefore, it is still not recommended to use the stored powders for critical parts or light intense and humid environments.}}, author = {{Klippstein, Sven Helge and Kletetzka, Ivo and Sural, Ilknur and Schmid, Hans-Joachim}}, journal = {{The International Journal of Advanced Manufacturing Technology }}, keywords = {{Selective laser sintering, Shelf life, Polyamide 12, powder, PA2200, material ageing}}, publisher = {{Springer}}, title = {{{Influence of a prolonged shelf time on PA12 laser sintering powder and resulting part properties}}}, doi = {{https://doi.org/10.1007/s00170-023-11243-1}}, year = {{2023}}, } @inbook{34211, abstract = {{Nowadays, clinching is a widely used joining technique, where sheets are joined by pure deformation to create an interlock without the need for auxiliary parts. This leads to advantages such as reduced joining time and manufacturing costs. On the other hand, the joint strength solely relies on directed material deformation, which renders an accurate material modelling essential to reliably predict the joint forming. The formation of the joint locally involves large plastic strains and possibly complex non-proportional loading paths, as typical of many metal forming applications. Consequently, a finite plasticity formulation is utilised incorporating a Chaboche–Rousselier kinematic hardening law to capture the Bauschinger effect. Material parameters are identified from tension–compression tests on miniature spec- imens for the dual-phase steel HCT590X. The resulting material model is implemented in LS-Dyna to study the locally diverse loading paths and give a quantitative statement on the importance of kinematic hardening for clinching. It turns out that the Bauschinger effect mainly affects the springback of the sheets and has a smaller effect on the joint forming itself.}}, author = {{Friedlein, Johannes and Mergheim, Julia and Steinmann, Paul}}, booktitle = {{The Minerals, Metals & Materials Series}}, isbn = {{9783031062117}}, issn = {{2367-1181}}, keywords = {{Clinching, Material modelling, Kinematic hardening, Parameter identification, Bauschinger effect}}, publisher = {{Springer International Publishing}}, title = {{{Influence of Kinematic Hardening on Clinch Joining of Dual-Phase Steel HCT590X Sheet Metal}}}, doi = {{10.1007/978-3-031-06212-4_31}}, year = {{2022}}, } @article{33988, author = {{Moritzer, Elmar and Driediger, Christine}}, issn = {{1022-1360}}, journal = {{Macromolecular Symposia}}, keywords = {{digital light processing, material combination, reactive direct bonding, vat photopolymerization}}, number = {{1}}, publisher = {{Wiley}}, title = {{{Reactive Direct Bonding of Digital Light Process Components}}}, doi = {{10.1002/masy.202100396}}, volume = {{404}}, year = {{2022}}, } @inproceedings{22274, abstract = {{The use of high-strength steel and aluminium is rising due to the intensified efforts being made in lightweight design, and self-piercing riveting is becoming increasingly important. Conventional rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and the coating. To shorten the manufacturing process, the use of stainless steel with high strain hardening as the rivet material represents a promising approach. This allows the coating of the rivets to be omitted due to the corrosion resistance of the material and, since the strength of the stainless steel is achieved by cold forming, heat treatment is no longer required. In addition, it is possible to adjust the local strength within the rivet. Because of that, the authors have elaborated a concept for using high nitrogen steel 1.3815 as the rivet material. The present investigation focusses on the joint strength in order to evaluate the capability of rivets in high nitrogen steel by comparison to conventional rivets made of treatable steel. Due to certain challenges in the forming process of the high nitrogen steel rivets, deviations result from the targeted rivet geometry. Mainly these deviations cause a lower joint strength with these rivets, which is, however, adequate. All in all, the capability of the new rivet is proven by the results of this investigation. }}, author = {{Uhe, Benedikt and Kuball, Clara-Maria and Merklein, Marion and Meschut, Gerson}}, keywords = {{Self-piercing Riveting, Joining Technology, Rivet Geometry, Rivet Material, High Nitrogen Steel, Joint Strength}}, location = {{Liège, Belgien}}, title = {{{Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel}}}, doi = {{10.25518/esaform21.1911}}, year = {{2021}}, } @article{19973, abstract = {{As a result of lightweight design, increased use is being made of high-strength steel and aluminium in car bodies. Self-piercing riveting is an established technique for joining these materials. The dissimilar properties of the two materials have led to a number of different rivet geometries in the past. Each rivet geometry fulfils the requirements of the materials within a limited range. In the present investigation, an improved rivet geometry is developed, which permits the reliable joining of two material combinations that could only be joined by two different rivet geometries up until now. Material combination 1 consists of high-strength steel on both sides, while material combination 2 comprises aluminium on the punch side and high-strength steel on the die side. The material flow and the stress and strain conditions prevailing during the joining process are analysed by means of numerical simulation. The rivet geometry is then improved step-by-step on the basis of this analysis. Finally, the improved rivet geometry is manufactured and the findings of the investigation are verified in experimental joining tests.}}, author = {{Uhe, Benedikt and Kuball, Clara-Maria and Merklein, Marion and Meschut, Gerson}}, journal = {{Production Engineering}}, keywords = {{Self-piercing riveting, Joining technology, Rivet geometry, Multi-material design, High-strength steel, Aluminium}}, pages = {{417--423}}, title = {{{Improvement of a rivet geometry for the self-piercing riveting of high-strength steel and multi-material joints}}}, doi = {{10.1007/s11740-020-00973-w}}, volume = {{14}}, year = {{2020}}, } @inproceedings{15332, abstract = {{Artificial intelligence (AI) has the potential for far-reaching – in our opinion – irreversible changes. They range from effects on the individual and society to new societal and social issues. The question arises as to how students can learn the basic functioning of AI systems, what areas of life and society are affected by these and – most important – how their own lives are affected by these changes. Therefore, we are developing and evaluating school materials for the German ”Science Year AI”. It can be used for students of all school types from the seventh grade upwards and will be distributed to about 2000 schools in autumn with the support of the Federal Ministry of Education and Research. The material deals with the following aspects of AI: Discussing everyday experiences with AI, how does machine learning work, historical development of AI concepts, difference between man and machine, future distribution of roles between man and machine, in which AI world do we want to live and how much AI would we like to have in our lives. Through an accompanying evaluation, high quality of the technical content and didactic preparation is achieved in order to guarantee the long-term applicability in the teaching context in the different age groups and school types. In this paper, we describe the current state of the material development, the challenges arising, and the results of tests with different classes to date. We also present first ideas for evaluating the results.}}, author = {{Schlichtig, Michael and Opel, Simone Anna and Budde, Lea and Schulte, Carsten}}, booktitle = {{ISSEP 2019 - 12th International conference on informatics in schools: Situation, evaluation and perspectives, Local Proceedings}}, editor = {{Jasutė, Eglė and Pozdniakov, Sergei}}, isbn = {{978-9925-553-27-3}}, keywords = {{Artificial Intelligence, Machine Learning, Teaching Material, Societal Aspects, Ethics. Social Aspects, Science Year, Simulation Game}}, location = {{Lanarca}}, pages = {{65 -- 73}}, title = {{{Understanding Artificial Intelligence – A Project for the Development of Comprehensive Teaching Material}}}, volume = {{12}}, year = {{2019}}, } @inproceedings{12952, author = {{Dreiling, Dmitrij and Feldmann, Nadine and Henning, Bernd}}, keywords = {{piezoelectric materials, piezoelectric properties, DC bias field, non-linear material parameters}}, location = {{Nürnberg}}, publisher = {{AMA Service GmbH}}, title = {{{A DC bias approach to the characterisation of non-linear material parameters of piezoelectric ceramics}}}, doi = {{10.5162/sensoren2019/5.1.2}}, year = {{2019}}, } @article{6567, author = {{Johannesmann, Sarah and Düchting, Julia and Webersen, Manuel and Claes, Leander and Henning, Bernd}}, issn = {{0171-8096}}, journal = {{tm - Technisches Messen}}, keywords = {{Continous-fibre reinforced plastics, material parameters, orthotropy, ultrasonics}}, number = {{85}}, pages = {{478--486}}, title = {{{An acoustic waveguide-based approach to the complete characterisation of linear elastic, orthotropic material behaviour}}}, doi = {{10.1515/teme-2017-0132}}, volume = {{2018}}, year = {{2018}}, } @article{6551, author = {{Bause, Fabian and Rautenberg, Jens and Feldmann, Nadine and Webersen, Manuel and Claes, Leander and Gravenkamp, Hauke and Henning, Bernd}}, journal = {{Measurement Science and Technology}}, keywords = {{material characterization, material parameters, acoustic waveguide, daming, ultrasonic transducer}}, number = {{10}}, title = {{{Ultrasonic transmission measurements in the characterization of viscoelasticity utilizing polymeric waveguides}}}, doi = {{10.1088/0957-0233/27/10/105601}}, volume = {{27}}, year = {{2016}}, } @phdthesis{24751, abstract = {{Das Thema der vorliegenden Dissertation ist die "Prozessqualifizierung zur verlässlichen Herstellung von Produkten im Polymer Lasersinterverfahren". Über eine definierte Qualitätsprozesskette werden sämtliche, auf die Produktqualität relevanten Einflussparameter, bestimmt und berücksichtigt. Unterschiedliche Methoden zur Materialcharakterisierung des pulverförmigen Ausgangsmaterials werden analysiert und bewertet. Rheologische sowie chemische Eigenschaften, aber auch die Partikelgrößenverteilung oder die Schüttdichte werden hinsichtlich Relevanz, Einfluss und Anwenderfreundlichkeit untersucht. Das Ziel ist eine sinnvolle Bestimmung des Ausgangszustandes des Pulvers anhand definierter, relevanter Materialeigenschaften, um reproduzierbare technische Bauteileigenschaften zu gewährleisten. Dazu werden mechanische, dynamisch-mechanische, physikalische, elektrische, thermische sowie chemische Untersuchungen durchgeführt und hinsichtlich wichtiger Einflussparameter evaluiert. Die Bestimmung erfolgt über entwickelte Referenzjobs, in denen die hauptsächlichen Einflussfaktoren auf das Polymer-Lasersinterverfahren entlang der Qualitätsprozesskette berücksichtigt werden. Die charakterisierten Daten dienen zur Auslegung eines fiktiven Produktes aus der Luftfahrtindustrie. Mit Hilfe dieser Methoden lassen sich Materialkennwerte für diverse Simulationstools eindeutig bestimmen um eine realitätsnahe Berechnung zu gewährleisten. }}, author = {{Rüsenberg, Stefan}}, keywords = {{Additive Fertigung, Polymere, Lasersintern, Methode, Qualität, Konstruktion, Eigenschaften, Material, Charakterisierung, Qualifizierung}}, pages = {{242}}, publisher = {{Shaker Verlag GmbH}}, title = {{{Prozessqualifizierung zur verlässlichen Herstellung von Produkten im Polymer Lasersinterverfahren}}}, volume = {{Band, 2}}, year = {{2015}}, } @inproceedings{9952, abstract = {{The contact between viscoelastic materials e.g. elastomers and a rough surface leads to a special friction characteristic, which differs greatly in its properties comparing to other materials like metals. In practice, this friction combination occurs for example in the tire-road contact, or in the use of rubber gaskets. Due to the frictional forces a system is significantly influenced in its vibrational properties. The friction force is composed of two main components adhesion and hysteresis. The adhesion results from molecular bounds between the contact partners, while the deformation of the viscoelastic material by the roughness of the counter body leads to power loss. This internal friction results in an additional frictional force, which is described by the hysteresis. To simulate the frictional behaviour of elastomers on rough surfaces and thus to determine the energy dissipation in contact, it is necessary to develop a mechanical model which considers the roughness of the contact partners, as well as dynamic effects and the dependence on normal pressure and sliding speed. The viscoelastic material behaviour must also be considered. The contact between two rough surfaces is modelled as a rough rigid layer contacting a rough elas- tic layer. The elastic layer is modelled by point masses connected by Maxwell-elements. This allows the viscoelastic properties of the elastomer to be considered. The behaviour of whole system can be described by equations of motion with integrated constraints. The degrees of freedom of the model depends on the varying contact conditions. A point mass not in contact has two degrees of freedom. A point mass in contact moving along the roughness path can be described by only one degree of freedom. For each Maxwell-Element also an inner coordinate and thus a further degree of freedom is needed. Because of varying contact conditions dur- ing the simulation, the simulation interrupts in case the contact conditions change. Then the equations of motions are adapted with respect to the contact constraints. As a result of the simulation one obtain the energy dissipation and thus the friction char- acteristic during the friction process. It is possible to use these results in three dimensional point-contact elements in order to model contact surfaces on lager length scales.}}, author = {{Schulte, Frank and Neuhaus, Jan and Sextro, Walter}}, booktitle = {{Proceedings of ICoEV 2015 International Conference on Engineering Vibration}}, keywords = {{Contact Mechanics, Viscoelastic Material, Adhesive Friction, Hysteresis Friction, Energy Dissipation, Vibration}}, pages = {{1109--1117}}, title = {{{A Mechanical Model for the Dynamical Contact of Elastic Rough Bodies with Viscoelastic Properties}}}, year = {{2015}}, } @inproceedings{13892, abstract = {{Several ultrasonic approaches for material determination are formulated in terms of an (nonlinear) inverse problem, e.g. immersion technique (Castaings et al. (2000)) or plate-waveguide techniques (Marzani et al. (2012)). In this contribution we focus on cylindrical waveguides for ultrasonic material determination and especially on the sensitivity of recorded transmission signals to the material properties. We utilize composite scaled sensitivities to determine the information content that can be achieved by the setup to certain parameters and discuss the limitations of the approach.}}, author = {{Bause, Fabian and Gravenkamp, Hauke and Rautenberg, Jens and Henning, Bernd}}, keywords = {{Sensitivity inverse problem ultrasonic material determination}}, pages = {{204--207}}, title = {{{Model based sensitivity analysis in the determination of viscoelastic material properties using transmission measurements through circular waveguides}}}, year = {{2015}}, } @article{9866, abstract = {{The hydrothermal method utilizes a solution-based chemical reaction to synthesize piezoelectric thin films and powders. This method has a number of advantages, such as low-temperature synthesis, and high purity and high quality of the product. In order to promote hydrothermal reactions, we developed an ultrasonic assisted hydrothermal method and confirmed that it produces dense and thick lead--zirconate--titanate (PZT) films. In the hydrothermal method, a crystal growth process follows the nucleation process. In this study, we verified that ultrasonic irradiation is effective for the nucleation process, and there is an optimum irradiation period to obtain thicker PZT films. With this optimization, a 9.2-$\mu$ m-thick PZT polycrystalline film was obtained in a single deposition process. For this film, ultrasonic irradiation was carried out from the beginning of the reaction for 18 h, followed by a 6 h deposition without ultrasonic irradiation. These results indicate that the ultrasonic irradiation mainly promotes the nucleation process.}}, author = {{Ohta, Kanako and Isobe, Gaku and Bornmann, Peter and Hemsel, Tobias and Morita, Takeshi}}, issn = {{0041-624X}}, journal = {{Ultrasonics}}, keywords = {{Piezoelectric material}}, number = {{4}}, pages = {{837 -- 841}}, title = {{{Study on optimizing ultrasonic irradiation period for thick polycrystalline PZT film by hydrothermal method}}}, doi = {{10.1016/j.ultras.2012.12.003}}, volume = {{53}}, year = {{2013}}, } @article{9758, abstract = {{As a lead-free piezoelectric ceramics, (K,Na)NbO$_{3}$ is a promising material because of its good piezoelectric properties. In this study, (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics were synthesized from a KNbO$_{3}$ and NaNbO$_{3}$ mixture powder prepared by the hydrothermal reaction. The hydrothermal reaction enables the production of high quality powder for the ceramics fabrication process. To obtain (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics, these two powders KNbO$_{3}$ and NaNbO$_{3}$ were mixed and then sintered together. X-Ray diffraction analysis revealed that the solid solution ceramics (K$_{1-x}$Na$_{x}$)NbO$_{3}$ was produced by the sintering process. The K/Na ratio in (K$_{1-x}$Na$_{x}$)NbO$_{3}$ ceramics was optimized for the best piezoelectric properties. The optimized forms was (K$_{0.48}$Na$_{0.52}$)NbO$_{3}$, which showed the following piezoelectric properties; k$_{33}$=0.56, d$_{33}$=114pC/N. In addition, the ferroelectric properties, P$_{r}$=7.72mC/cm$^{2}$, E$_{c}$=857V/mm, and the Curie temperature T$_{c}$=420$_{o}$C were also measured.}}, author = {{Maeda, Takafumi and Takiguchi, Norihito and Morita, Takeshi and Ishikawa, Mutsuo and Hemsel, Tobias}}, issn = {{1948-5719}}, journal = {{Journal of Korean Physical Society}}, keywords = {{Lead-free piezoelectric material, KNN, Hydrothermal method}}, number = {{4}}, pages = {{924--928}}, title = {{{Hydrothermal (K1-xNax)NbO3 Lead-free Piezoelectric Ceramics}}}, doi = {{10.3938/jkps.57.924}}, volume = {{57}}, year = {{2010}}, } @article{9759, abstract = {{Among various lead-free piezoelectric materials, (K,Na)NbO$_{3}$ is a very promising candidate. In this study, (K,Na)NbO$_{3}$ ceramics were sintered from mixed (K,Na)NbO$_{3}$ and NaNbO$_{3}$ powders prepared by hydrothermal reaction. These two powders were mixed with distilled water in a KNbO$_{3}$/NaNbO$_{3}$ molar ratio of 1. After sintering the mixed powder, the solid solution of (Na,K)NbO$_{3}$ ceramics was obtained. The electrical properties such as the electromechanical coupling factors k$_{p}$ and k$_{33}$, the mechanical quality factor, Q$_{m}$, and the piezoelectric constant d$_{33}$ of the sintered (K,Na)NbO$_{3}$ ceramics were 0.32, 0.48, 71 (radial mode), 118 ((33)mode), and 107 pC/N, respectively.}}, author = {{Maeda, Takafumi and Takiguchi, Norihito and Morita, Takeshi and Ishikawa, Mutsuo and Hemsel, Tobias}}, issn = {{1948-5719}}, journal = {{Materials Letters}}, keywords = {{Lead-free piezoelectric material, (K, Na)NbO$_{3}$ ceramics, Sintering solid solution, Piezoelectric properties}}, number = {{2}}, pages = {{125--128}}, title = {{{(K,Na)NbO3 lead-free piezoelectric ceramics synthesized from hydrothermal powders}}}, doi = {{10.1016/j.matlet.2009.10.012}}, volume = {{64}}, year = {{2010}}, }