Enhanced thermal stability and fracture toughness of TiAlN coatings by Cr, Nb and V-alloying

The effect of metal alloying on mechanical properties including hardness and fracture toughness were investigated in three alloys, Ti~0.33Al0.50(Me)~0.17N (Me¿=¿Cr, Nb and V), and compared to Ti0.50Al0.50N, in the as-deposited state and after annealing. All studied alloys display similar as-deposited hardness while the hardness evolution during annealing is found to be connected to phase transformations, related to the alloy's thermal stability. The most pronounced hardening was observed in Ti0.50Al0.50N, while all the coatings with additional metal elements sustain their hardness better and they are harder than Ti0.50Al0.50N after annealing at 1100¿°C. Fracture toughness properties were extracted from scratch tests. In all tested conditions, as-deposited and annealed at 900 and 1100¿°C, Ti0.33Al0.50Nb0.17N show the least surface and sub-surface damage when scratched despite the differences in decomposition behavior and h-AlN formation. Theoretically estimated ductility of phases existing in the coatings correlates well with their crack resistance. In summary, Ti0.33Al0.50Nb0.17N is the toughest alloy in both as-deposited and post-annealed states.Peer ReviewedPostprint (author's final draft

Mechanical strength of ground WC-Co cemented carbides after coating deposition

Manufacturing of hardmetal tools often involves surface grinding, ion etching and final coating. Each stage throughout the manufacturing chain introduces surface integrity changes which may be critical for defining the final mechanical behavior of the coated tools. Within this context, an experimental test program has been developed to assess the influence of a coating (TiN) deposition on surface integrity and transverse rupture strength of a previously ground fine-grained WC-Co grade substrate. Four different substrate surface finish conditions (prior to ion etching and coating) were evaluated: as sintered (AS), ground (G), polished (P), and ground plus high temperature annealing (GTT). Surface integrity and fracture resistance characterization, complemented with a detailed fractographic analysis, were performed on both uncoated and coated samples. Results show that the surface integrity after grinding has been partly modified during the ion etching and film deposition processes, particularly in terms of a reduced compressive residual stress state at the substrate surface level. Consequently, the grinding induced strength enhancement in hardmetals is reduced for coated specimens. Main reason behind it is the change of nature, location and stress state acting on critical flaw: from processing defects existing at the subsurface (uncoated G specimens) to grinding-induced microcracks located close to the interface between coating and substrate, but within the subsurface of the latter (coated G specimens). This is not the case for AS and P conditions, where flexural strength does not change as a result of ion etching and coating. Finally, fracture resistance increases slightly for GTT specimens after coating process, possibly caused by a beneficial effect of the deposited film on the residual stress state at the surfac

Grinding-induced metallurgical alterations in the binder phase of WC-Co cemented carbides

The metallic binder phase dictates the toughening behavior of WC-Co cemented carbides (hardmetals), even though it occupies a relative small fraction of the composite. Studies on deformation and phase transformation of the binder constituent are scarce. Grinding represents a key manufacturing step in machining of hardmetal tools, and is well-recognized to induce surface integrity alterations. In this work, metallurgical alterations of the binder phase in ground WC-Co cemented carbides have been assessed by a combination of electron back scattered diffraction and transmission electron microscopy techniques. The Co-base binder experiences a martensitic phase transformation from fcc to hcp crystal structure, predominantly in the first 5 µm below the surface. The hcp fraction decreases gradually along a depth of 10 µm. Surface Co displays severe plastic deformation under the highest strain, resulting in formation of nanocrystalline grains in the first micrometer below the surface. Microstructural refinement within the binder phase is observed even at greater depth. Stacking faults were detected in most of the refined grains. The metallurgical alterations of the binder phase modify the local stress distribution during grinding, which affects the discerned subsurface microcracking. The resulting residual stress profile is the sum of multiple subsurface changes, such as phase transformation, severe plastic deformation and grain refinement, where it is discerned that the depth profile of the transformed hcp-Co fraction coincides with the grinding-induced residual stress profile.Peer ReviewedPostprint (author's final draft

Orthogonal Light-Dependent Membrane Adhesion Induces Social Self-Sorting and Member-Specific DNA Communication in Synthetic Cell Communities

Developing orthogonal chemical communication pathways in diverse synthetic cell communities is a considerable challenge due to the increased crosstalk and interference associated with large numbers of different types of sender-receiver pairs. Herein, the authors control which sender-receiver pairs communicate in a three-membered community of synthetic cells through red and blue light illumination. Semipermeable protein-polymer-based synthetic cells (proteinosomes) with complementary membrane-attached protein adhesion communicate through single-stranded DNA oligomers and synergistically process biochemical information within a community consisting of one sender and two different receiver populations. Different pairs of red and blue light-responsive protein-protein interactions act as membrane adhesion mediators between the sender and receivers such that they self-assemble and socially self-sort into different multicellular structures under red and blue light. Consequently, distinct sender-receiver pairs come into the signaling range depending on the light illumination and are able to communicate specifically without activation of the other receiver population. Overall, this work shows how photoswitchable membrane adhesion gives rise to different self-sorting protocell patterns that mediate member-specific DNA-based communication in ternary populations of synthetic cells and provides a step towards the design of orthogonal chemical communication networks in diverse communities of synthetic cells

A versatile data acquisition system for capturing electromagnetic emissions in VHF band

This research investigates the occurrence of EM emissions from compressed rock and assesses their value as precursors to earthquakes. It is understood that electromagnetic emissions are accompanied by crack generation in the Earth's crust, and effort has been targeted on the analysis of electromagnetic signals preceding seismic events. There is a need for a robust Data Acquisition System for the reliable collection of such signals. The design and deployment of a novel system form part of this research. The EM data collected by the Data Acquisition System is subsequently analysed and correlations are made with natural phenomena. The design of the Data Acquisition System is presented and meets a specification which includes accuracy, robustness, power consumption, remote configurability achieved by the development of a novel architecture for flash memories which significantly increases the live span of these devices. The measuring of electromagnetic emissions should be performed by reliable systems, using devices that fully correspond to the specifications set by the needs of this research. This type of systems is not fully covered by existing commercial devices. These prototype VHF field stations (ground base - electromagnetic variation monitors in VHF band) are located around the Hellenic Are. This region is one of the most seismically active regions in western Eurasia due to subduction of the oceanic African lithosphere beneath the Eurasian plate. After approximately two years of electromagnetic VHF data collection, the final stage of this project took place. In this stage, possible correlation between naturally occurring electromagnetic emissions in VHF band and seismic events within a predefined radius around the observation location is investigated. Supplementary, effects of alternative electromagnetic sources, such as solar activity, is considered. Whilst EM emissions from compressed rocks can be demonstrated in the laboratory, it was found from a two-year evaluation that no reliable correlation with earthquake events could be established. However, significant patterns of activity were detected in EM spectrum and it was shown that these correlate strongly with other naturally occurring phenomena such as solar flares. The Data Acquisition System as developed in this thesis has related applications in long term and remote sensing operations including meteorology, environmental analysis and surveillance.EThOS - Electronic Theses Online ServiceNational Foundation of Scholarships (I.K.Y.)European Social Fund and National Resources - (EPEAEK II) ARXIMIDISGBUnited Kingdo

DNA-based communication in populations of synthetic protocells

Developing molecular communication platforms based on orthogonal communication channels is a crucial step towards engineering artificial multicellular systems. Here, we present a general and scalable platform entitled ‘biomolecular implementation of protocellular communication’ (BIO-PC) to engineer distributed multichannel molecular communication between populations of non-lipid semipermeable microcapsules. Our method leverages the modularity and scalability of enzyme-free DNA strand-displacement circuits to develop protocellular consortia that can sense, process and respond to DNA-based messages. We engineer a rich variety of biochemical communication devices capable of cascaded amplification, bidirectional communication and distributed computational operations. Encapsulating DNA strand-displacement circuits further allows their use in concentrated serum where non-compartmentalized DNA circuits cannot operate. BIO-PC enables reliable execution of distributed DNA-based molecular programs in biologically relevant environments and opens new directions in DNA computing and minimal cell technology

Contact damage resistance of TiN-coated hardmetals: Beneficial effects associated with substrate grinding

Contact loading is a common service condition for coated hardmetal tools and components. Substrate grinding represents a key step within the manufacturing chain of these coated systems. Within this context, the influence of surface integrity changes caused by abrasive grinding of the hardmetal substrate, prior to coating, is evaluated with respect to contact damage resistance. Three different substrate surface finish conditions are studied: ground (G), mirror-like polished (P) and ground plus heat-treated (GTT). Tests are conducted by means of spherical indentation under increasing monotonic load and the contact damage resistance is assessed. Substrate grinding enhances resistance against both crack nucleation at the coating surface and subsequent propagation into the hardmetal substrate. Hence, crack emergence and damage evolution is effectively delayed for the coated G condition, as compared to the reference P one. The observed system response is discussed on the basis of the beneficial effects associated with compressive residual stresses remnant at the subsurface level after grinding, ion-etching and coating. The influence of the stress state is further corroborated by the lower contact damage resistance exhibited by the coated GTT specimens. Finally, differences observed on the interaction between indentation-induced damage and failure mode under flexural testing points in the direction that substrate grinding also enhances damage tolerance of the coated system when exposed to contact loadsPeer ReviewedPostprint (author's final draft

DNA storage in thermoresponsive microcapsules for repeated random multiplexed data access

In support of the publication "DNA storage in thermoresponsive microcapsules for repeated random multiplexed data access" we share the following datasets and code: AutoCAD drawing of the microfluidic trapping device. Sequences of the DNA used to encode the 25 files used in the current study. FASTQ-files of the sequencing experiments of Figures 5b and d. Python scripts that allow for the reproduction of our sequencing data analysis. The code has been tested on MacOS 13.0.1, Python 3.7.13, samtools 1.16.1 and BWA 0.7.17

The F-box protein MAX2 contributes to resistance to bacterial phytopathogens in Arabidopsis thaliana

Peer reviewe

Bottom-up construction of complex biomolecular systems with cell-free synthetic biology

Cell-free systems offer a promising approach to engineer biology since their open nature allows for well-controlled and characterized reaction conditions. In this review, we discuss the history and recent developments in engineering recombinant and crude extract systems, as well as breakthroughs in enabling technologies, that have facilitated increased throughput, compartmentalization, and spatial control of cell-free protein synthesis reactions. Combined with a deeper understanding of the cell-free systems themselves, these advances improve our ability to address a range of scientific questions. By mastering control of the cell-free platform, we will be in a position to construct increasingly complex biomolecular systems, and approach natural biological complexity in a bottom-up manner