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1.
Rev Med Suisse ; 19(814): 319-323, 2023 Feb 15.
Artigo em Francês | MEDLINE | ID: mdl-36790154

RESUMO

The hospital management of patients experiencing a suicidal crisis and suffering from a personality disorder is complex for caregivers. The care model must be adapted and applied by a multidisciplinary team. The emotional charge of these crisis situations makes it difficult for caregivers to maintain their ability to treat mental states with curiosity and without necessarily experiencing them as they appear to them. In other words, it could be difficult to mentalize. For example, an expressed desire to die may be much more complex in reality. Mentalizing abilities are challenged differently depending on our role with the patient. In this article we explore the specifics of interdisciplinary crisis work through the lens of mentalization-based therapy.


La prise en charge hospitalière de patients traversant une crise suicidaire et souffrant d'un trouble de personnalité est complexe pour les soignants. Le modèle de soin doit être adapté et applicable par une équipe pluridisciplinaire. La charge émotionnelle de ces situations de crise rend difficile aux soignants de préserver leur capacité à traiter les états mentaux avec curiosité et sans les vivre nécessairement tels qu'ils leur apparaissent, c'est-à-dire de pouvoir mentaliser. Ainsi, un désir exprimé de mourir peut s'avérer beaucoup plus complexe en réalité. Les capacités de mentalisation sont mises à mal différemment selon notre rôle auprès du patient. Nous explorons dans cet article les spécificités du travail interdisciplinaire de crise au travers du prisme de la thérapie basée sur la mentalisation.


Assuntos
Transtorno da Personalidade Borderline , Mentalização , Humanos , Ideação Suicida , Emoções , Transtornos da Personalidade , Transtorno da Personalidade Borderline/psicologia
2.
Sci Technol Adv Mater ; 23(1): 692-706, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36337083

RESUMO

Phase separation into an A2+B2 two-phase microstructure in refractory compositionally complex alloys (RCCA) has been speculated as being spinodal in nature with continuous chemical distribution during the separation. However, these reactions might instead occur as precipitation by nucleation and growth. In order to unequivocally elucidate the distinct nature of phase separation sequence in RCCA from the system Ta-Mo-Ti-Cr-Al, atom probe tomography and electron microscopy techniques were utilized on samples that were annealed over multiple orders of magnitude in time. The composition 82(TaMoTi)-8Cr-10Al (at.%) was chosen, as it exhibits a two-phase microstructure, with a desired A2 matrix and embedded B2 phase. Quenching the samples from 1200°C resulted in a microstructure consisting of ordered clusters (2 nm) of distinct chemical composition. Subsequent annealing at 800°C to 1000°C leads to an increase in the volume fraction of the precipitating phase, which saturates after 10 h. Further annealing leads to the ripening of the microstructure; however, the absolute size of the precipitates stays <100 nm even after 1000 h. For the investigated conditions, the interface between matrix and precipitate can be considered sharp within the resolution of the applied techniques and no significant change in the transition of chemical composition across the interface is observed. Therefore, the phase separation mechanism is confirmed to be phase nucleation and growth in contrast to the possible spinodal decomposition, as hypothesized for other RCCA systems. The impact of precipitation and coarsening on the hardness of the alloy is discussed.

3.
Rev Med Suisse ; 18(796): 1744-1748, 2022 Sep 21.
Artigo em Francês | MEDLINE | ID: mdl-36134628

RESUMO

This article presents basic notions of "Good Psychiatric Management" (GPM) for Borderline Personality Disorder (BPD). There have been several evidence-based psychotherapeutic treatments for BPD for several decades. Nevertheless, high requirements and motivation required sometimes have a discouraging effect for trainees. GPM aims at offering «good enough¼ and less difficult to implement care. This article presents the notion of Interpersonnal Hypersensitivity and its different attachment states (attached, threatened, abandoned, and desperate) describing internal coherence of BPD and founding therapeutic interventions. GPM is principle based, thus is highly adaptable, as can be seen in integration with other intervention models or implementation of stepped care.


Cet article présente les bases du «Good Psychiatric Management¼ (GPM) pour le trouble de la personnalité borderline. Il existe pour ce trouble différents traitements psychothérapeutiques fondés sur les preuves. Les exigences importantes que ceux-ci représentent en termes de formation et de motivation ont parfois comme effet de décourager les thérapeutes en formation. Le GPM décrit des soins «suffisamment bons¼, accessibles et moins difficiles à implanter. Cet article présente le concept d'hypersensibilité interpersonnelle qui décrit la cohérence interne du trouble et fonde les interventions thérapeutiques. Le GPM est basé sur l'application de principes, ce qui lui donne une adaptabilité importante, par exemple pour l'intégration avec d'autres modèles d'intervention ou des soins par paliers.


Assuntos
Transtorno da Personalidade Borderline , Transtorno da Personalidade Borderline/psicologia , Transtorno da Personalidade Borderline/terapia , Humanos , Motivação , Psicoterapia
4.
J Mater Res ; 36(4): 970-981, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34083869

RESUMO

The microstructure of the materials constituting a metallic frictional contact strongly influence tribological performance. Being able to tailor friction and wear is challenging due to the complex microstructure evolution associated with tribological loading. Here, we investigate the effect of the strain distribution on these processes. High-purity copper plates were morphologically surface textured with two parallel rectangles - referred to as membranes - over the entire sample length by micro-milling. By keeping the width of these membranes constant and only varying their height, reciprocating tribological loading against sapphire discs resulted in different elastic and plastic strains. Finite element simulations were carried out to evaluate the strain distribution in the membranes. It was found that the maximum elastic strain increases with decreasing membrane stiffness. The coefficient of friction decreases with increasing membrane aspect ratio. By analyzing the microstructure and local crystallographic orientation, we found that both show less change with decreasing membrane stiffness.

5.
Rev Med Suisse ; 16(694): 1057-1059, 2020 May 20.
Artigo em Francês | MEDLINE | ID: mdl-32432424

RESUMO

The psychotherapeutic management of a suicidal crisis makes it possible to think of the health crisis linked to COVID-19 from a particular angle. In this article, we show the parallels but also the differences between these two types of crises. The sequential course of the crisis, the viral agent which acts as a triggering factor and the host of reactions which follow can thus evoke a suicidal crisis during which a subject often perceives an external event as a precipitating factor. However, unlike confinement in the case of the virus, it is the relationship, in particular the therapeutic relationship, which makes it possible to get through the crisis. This relationship should allow us to get to know our specific vulnerabilities, those on which the triggering factor has specifically acted.


La prise en charge psychothérapeutique d'une crise suicidaire permet de penser la crise sanitaire liée au COVID-19 sous un angle particulier. Dans cet article, nous montrons les parallèles mais également les différences entre ces deux types de crises. Le déroulement séquentiel de la crise, l'agent viral qui agit comme un facteur déclenchant et la foule de réactions qui s'ensuivent peuvent ainsi évoquer une crise suicidaire durant laquelle un sujet perçoit souvent un événement externe comme facteur précipitant. Toutefois, contrairement au confinement dans le cas du virus, c'est bien la relation, notamment la relation thérapeutique, qui permet de traverser la crise. Cette relation doit nous permettre de faire connaissance avec nos vulnérabilités spécifiques, celles sur lesquelles le facteur déclenchant a précisément agi.


Assuntos
Infecções por Coronavirus/epidemiologia , Pneumonia Viral/epidemiologia , Estresse Psicológico , Suicídio/estatística & dados numéricos , Adaptação Psicológica , COVID-19 , Humanos , Pandemias
6.
Rev Med Suisse ; 16(681): 314-317, 2020 Feb 12.
Artigo em Francês | MEDLINE | ID: mdl-32049453

RESUMO

Suicide is a common cause of death in Switzerland. It often occurs during a period of crisis marked by a disruption of the subject's intrapsychic, interpersonal or social balance. The management of this crisis is crucial and essentially psychotherapeutic. Drug therapy may be necessary for the management of acute symptoms or for the prevention of long-term suicidal risk. Benzodiazepines and atypical antipsychotics are often used for acute symptoms such as anxiety or sleep disorders while other molecules are recognized in reducing long-term suicidal risk. Some disorders, such as borderline personality disorder, account for more frequent suicidal behaviors. The pharmacological management of these specific situations is discussed.


Le suicide est une cause de mortalité fréquente en Suisse. Il survient souvent durant une période de crise marquée par une perturbation de l'équilibre intrapsychique, interpersonnel ou social du sujet. La prise en charge de cette crise est cruciale et essentiellement psychothérapeutique. Un traitement médicamenteux peut s'avérer nécessaire pour la gestion des symptômes aigus ou la prévention du risque suicidaire à long terme. Les benzodiazépines et les antipsychotiques atypiques sont souvent utilisés pour les symptômes aigus comme l'anxiété ou les troubles du sommeil. D'autres molécules sont reconnues dans la diminution du risque suicidaire à long terme. Certains troubles, comme le trouble borderline, rendent compte de comportements suicidaires plus fréquents. La prise en charge pharmacologique de ces situations spécifiques est discutée.


Assuntos
Antipsicóticos/farmacologia , Prevenção do Suicídio , Suicídio/psicologia , Benzodiazepinas/farmacologia , Transtorno da Personalidade Borderline/psicologia , Humanos , Fatores de Risco , Ideação Suicida , Suíça
7.
Small ; 15(7): e1803944, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30624016

RESUMO

The locally defined growth of carbon nanofibers with lambda shape in an open flame process is demonstrated. Via the growth time, the geometry of the structures can be tailored to a Λ- or λ-type shape. Microchannel cantilever spotting and dip-pen nanolithography are utilized for the deposition of catalytic salt NiCl2 · 6H2 O for locally controlled growth of lambda-shaped carbon nanofibers. Rigorous downscaling reveals a critical catalytic salt volume of 0.033 µm³, resulting in exactly one lambda-shaped carbon nanofiber at a highly predefined position. An empirical model explains the observed growth process.

8.
Rev Med Suisse ; 15(637): 333-336, 2019 Feb 06.
Artigo em Francês | MEDLINE | ID: mdl-30724534

RESUMO

Borderline personality disorder is a common and severe disorder that confronts health professionals with some of their limitations. Relational difficulties with these patients lead to discontinuation of follow-up or unnecessary or even deleterious care. We present here simple answers to the questions that will inevitably arise in the management of your borderline patients. They are applicable by both general practitioners and specialists, to better meet the challenge that these patients ask us. We insist on properly recognizing and detecting the disorder. We propose to disclose the diagnosis to the patient and provide the necessary explanations. This is the better way to anticipate the repeating crises. Finally, interacting with other caregivers is important to ensure an effective and sustainable care system for these patients.


Le trouble de la personnalité borderline est un trouble fréquent, sévère et qui confronte les professionnels de la santé à certaines de leurs limites. Les difficultés relationnelles avec ces patients entraînent des ruptures de suivi, des soins inutiles ou délétères. Nous proposons des réponses simples aux questions qui surgiront immanquablement dans la prise en charge des patients borderline. Elles sont applicables par les généralistes et les spécialistes, afin de relever au mieux le défi que ces patients nous posent. Nous insistons sur l'importance de reconnaître et dépister le trouble. Nous proposons d'en parler avec le patient et de fournir les explications nécessaires. Cela permet de se préparer aux crises. Enfin, interagir avec les autres soignants est important pour garantir un dispositif de soins efficace et durable pour ces patients.


Assuntos
Transtorno da Personalidade Borderline , Clínicos Gerais , Humanos , Relações Interpessoais
9.
Langmuir ; 30(14): 4033-9, 2014 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-24673164

RESUMO

We study the equilibrium wetting behavior of immiscible multiphase systems on a flat, solid substrate. We present numerical computations which are based on a vector-valued multiphase-field model of Allen-Cahn type, with a new boundary condition, based on appropriately designed surface energy contributions in order to ensure the right contact angles at multiphase junctions. Experimental investigations are carried out to validate the method and to support the numerical results.

10.
J Psychiatr Pract ; 30(3): 220-226, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38819246

RESUMO

Interpersonal hypersensitivity (IHS) is a core organizing concept of Good Psychiatric Management, a generalist treatment for borderline personality disorder (BPD) that relies on basic tools most clinicians already employ yet is informed by an organized and evidence-based framework, developed for dissemination in various mental health care settings. We work in an inpatient psychiatric unit that specializes in the management of suicidal crises at the University Hospitals of Geneva, Switzerland. Because we see numerous patients with previously undiagnosed BPD during their first hospitalization, we have developed techniques and instruments to promote efficient and easy-to-implement psychoeducation. In this article, we propose a practical and user-friendly measure of IHS that is well-suited for use by multidisciplinary inpatient staff or outpatient nursing-based staff, the IHS Ruler, which is based on a visual analog scale. It is a pragmatic tool for preliminary psychoeducation for patients with BPD and their caregivers. Its ease of use and structured way of presenting the inner experience of these patients in relation to their current interpersonal environment allows caregivers to establish a framework for internal reflection and sharing, discuss the causes of current transactions, and illuminate larger patterns in the causes of the patient's crises. Ultimately, this process can help patients and the clinical staff supporting them anticipate future problems.


Assuntos
Transtorno da Personalidade Borderline , Humanos , Transtorno da Personalidade Borderline/terapia , Educação de Pacientes como Assunto/métodos , Relações Interpessoais , Adulto , Suíça
11.
Sci Bull (Beijing) ; 69(2): 227-236, 2024 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-38072707

RESUMO

Traditional high strength engineering alloys suffer from serious surface brittleness and inferior wear performance when servicing under sliding contact at cryogenic temperature. Here, we report that the recently emerging CoCrNi multi-principal element alloy defies this trend and presents dramatically enhanced wear resistance when temperature decreases from 273 to 153 K, surpassing those of cryogenic austenitic steels. The temperature-dependent structure characteristics and deformation mechanisms influencing the cryogenic wear resistance of CoCrNi are clarified through microscopic observation and atomistic simulation. It is found that sliding-induced subsurface structures show distinct scenarios at different deformation temperatures. At cryogenic condition, significant grain refinement and a deep plastic zone give rise to an extended microstructural gradient below the surface, which can accommodate massive sliding deformation, in direct contrast to the strain localization and delamination at 273 K. Meanwhile, the temperature-dependent cryogenic deformation mechanisms (stacking fault networks and phase transformation) also provide additional strengthening and toughening of the subsurface material. These features make the CoCrNi alloy particularly wear resistant at cryogenic conditions and an excellent candidate for safety-critical applications.

12.
Personal Disord ; 14(3): 321-333, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-36757989

RESUMO

People with personality disorders (PDs) are often admitted to psychiatric emergency services due to the frequent repetition of acute crises. This study drew on the ICD diagnostic records of 2,634 individuals with PDs who were admitted to a specialized inpatient psychiatric crisis unit over a 6-year period. Multiple logistic regressions and survival regressions were performed to examine whether PD categories, gender, and other individual, interpersonal, and precipitating factors were associated with readmission and time-to-readmission. The results showed a 16.1% readmission rate. Of these, 99.5% of readmissions occurred within 4 years following the first admission. Gender was the main factor associated with both readmission and time-to-readmission: while men were readmitted faster, more women in total were readmitted for a second psychiatric emergency hospitalization. Findings also indicated that readmission rate and time-to-readmission differed following the category of PD: readmission rate in a ratio of 1-2 (from 8% to 10% for dissocial and paranoid PD up to 19%-21% for impulsive and borderline PD), and time-to-readmission in a ratio of 1-5 (from 1 month for anankastic and dependent, to 5 months for impulsive, histrionic and anxious-avoidant PD). Limitations of this naturalistic study include a lack of self-reported measures and generalizability to less specialized emergency settings. Future research should include a prospective longitudinal design using standardized scalable measurement tools to improve the completeness and accuracy of the data concerning the psychological processes involved in risk and time-to-readmission after brief hospitalizations in emergency psychiatry. (PsycInfo Database Record (c) 2023 APA, all rights reserved).


Assuntos
Serviços de Emergência Psiquiátrica , Readmissão do Paciente , Masculino , Humanos , Feminino , Estudos Retrospectivos , Estudos Prospectivos , Transtornos da Personalidade/terapia , Transtornos da Personalidade/diagnóstico
13.
Front Psychiatry ; 14: 1186524, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37564248

RESUMO

Good Psychiatric Management (GPM) is a generalist clinical management approach for borderline personality disorder that incorporates common ingredients of good standard care for any psychiatric diagnosis with what works from prevailing specialist psychotherapies. Similar to all validated therapies for BPD, it relies on a specified formulation of the disorder' symptoms as arising from interpersonal hypersensitivity, to dynamically describe typical patterns of daily self- and interpersonal issues that drive the instability that defines the general personality dysfunction characteristic of the disorder. Recent adaptations of GPM have been proposed for narcissistic personality disorder and obsessive-compulsive personality disorder, with development of similar dynamic models for both (intrapsychic coherence model and model of overcontrol). New dimensional models of personality disorder diagnosis have been developed to address limitations of categorical approach, but the incorporation of these models into usage in the delivery of clinical services (where categorical approach remains the most used) is limited. This paper describes an adaptation of GPM to two cases of personality disorder that illustrate the usefulness of GPM models for dynamic representation of complex daily fluctuations in internal psychic coherence and interpersonal functioning. Specialist psychotherapies will never meet the demands of public health needs to treat personality dysfunction, and incorporation of new dimensional models of diagnosis are needed for treatments that can provide a minimal standard of care for providers and patients.

14.
Sante Ment Que ; 47(2): 221-233, 2022.
Artigo em Francês | MEDLINE | ID: mdl-37279323

RESUMO

Context Our team works in a psychiatric hospital unit at the University Hospitals of Geneva (Switzerland). We welcome there for 7 days people in crisis situations who have either suicidal thoughts or suicidal behavior. As factors precipitating the suicidal crisis, these people go through life events that are accompanied by intense interpersonal difficulties or that threaten the image they have of themselves. In our clinical population, approximately 35% of patients suffer from borderline personality disorder (BPD). In these patients, repeated crises and suicidal behavior lead to frequent and damaging relational and therapeutic ruptures. Our objective is to develop a specific approach to this clinical problem. Intervention We have developed a brief psychological intervention informed by mentalization-based treatment (MBT) in 4 stages: welcoming of the patient, affective mentalization of the crisis elements, formulation of the problem, work on discharge and the continuation of outpatient care. This intervention is suitable for a medical-nursing team. From a MBT point of view, the welcoming phase is mainly devoted to mirroring and affective regulation in order to reduce the intensity of psychic disorganization. It is then a question of activating the capacity to mentalize, namely curiosity about mental states, through work on the crisis narrative with an affective focus. We then work with people to construct a formulation of their problem in which they can assume a role. It is about making them "agents" of their crises. Then we can end the intervention by working on both the separation and a projection into the immediate future. The goal is then to extend the psychological work started in our unit at the level of an ambulatory network. The termination phase sees the attachment system reactivated and the reappearance of the difficulties hitherto outside the therapeutic space. Clinical implications MBT is effective for BPD, particularly in reducing suicidal gestures and the number of hospitalizations. We have adjusted its theoretical and clinical device for individuals hospitalized due to a suicidal crisis and who present various and comorbid psychopathological profiles. MBT allows the adaptation and evaluation of empirically based psychotherapeutic tools to different clinical settings but also to different clinical populations.


Assuntos
Transtorno da Personalidade Borderline , Mentalização , Humanos , Intervenção em Crise , Hospitalização , Assistência Ambulatorial , Ideação Suicida , Transtorno da Personalidade Borderline/terapia , Transtorno da Personalidade Borderline/psicologia
15.
Nat Commun ; 13(1): 5048, 2022 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-36030264

RESUMO

Tool based manufacturing processes like injection moulding allow fast and high-quality mass-market production, but for optical polymer components the production of the necessary tools is time-consuming and expensive. In this paper a process to fabricate metal-inserts for tool based manufacturing with smooth surfaces via a casting and replication process from fused silica templates is presented. Bronze, brass and cobalt-chromium could be successfully replicated from shaped fused silica replications achieving a surface roughnesses of Rq 8 nm and microstructures in the range of 5 µm. Injection moulding was successfully performed, using a commercially available injection moulding system, with thousands of replicas generated from the same tool. In addition, three-dimensional bodies in metal could be realised with 3D-Printing of fused silica casting moulds. This work thus represents an approach to high-quality moulding tools via a scalable facile and cost-effective route surpassing the currently employed cost-, labour- and equipment-intensive machining techniques.

16.
Nanomaterials (Basel) ; 12(14)2022 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-35889635

RESUMO

The high-power impulse magnetron sputtering (HiPIMS) technique was applied to deposit multilayer-like (Cr, Y)Nx coatings on AISI 304L stainless steel, using pendular substrate oscillation and a Cr-Y target and varying the nitrogen flow rate from 10 to 50 sccm. The microstructure, mechanical and tribological properties were investigated by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, instrumented nano-hardness, and wear tests. The columnar grain structure became highly segmented and nanosized due to pendular substrate oscillation and the addition of yttrium. The deposition rate increased continuously with the growing nitrogen flow rate. The increase in nitrogen flow from 10 to 50 sccm increased the hardness of the coatings (Cr, Y)Nx, with a maximum hardness value of 32.7 GPa for the coating (Cr, Y)Nx with a nitrogen flow of 50 sccm, which greatly surpasses the hardness of CrN films with multilayer-like (Cr, Y)Nx coatings architecture. The best mechanical and tribological performance was achieved for a nitrogen flow rate of 50 sccm. This was enabled by more elevated compressive stresses and impact energies of the impinging ions during film growth, owing to an increase of HiPIMS peak voltage with a rising N2/Ar ratio.

17.
ACS Appl Mater Interfaces ; 14(42): 48091-48105, 2022 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-36222465

RESUMO

Due to their excellent biocompatibility, outstanding mechanical properties, high strength-to-weight ratio, and good corrosion resistance, titanium (Ti) alloys are extensively used as implant materials in artificial joints. However, Ti alloys suffer from poor wear resistance, resulting in a considerably short lifetime. In this study, we demonstrate that the chemical self-assembly of novel two-dimensional (2D) diamond nanosheet coatings on Ti alloys combined with natural silk fibroin used as a novel lubricating fluid synergistically results in excellent friction and wear performance. Linear-reciprocating sliding tests verify that the coefficient of friction and the wear rate of the diamond nanosheet coating under silk fibroin lubrication are reduced by 54 and 98%, respectively, compared to those of the uncoated Ti alloy under water lubrication. The lubricating mechanism of the newly designed system was revealed by a detailed analysis of the involved microstructural and chemical changes. The outstanding tribological behavior was attributed to the establishment of artificial joint lubrication induced by the cross binding between the diamond nanosheets and silk fibroin. Additionally, excellent biocompatibility of the lubricating system was verified by cell viability, which altogether paves the way for the application of diamond coatings in artificial Ti joint implants.


Assuntos
Fibroínas , Fibroínas/química , Diamante , Titânio/química , Teste de Materiais , Ligas/química , Corrosão , Água , Propriedades de Superfície
18.
Adv Sci (Weinh) ; 9(31): e2204385, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36057994

RESUMO

Transparent ceramics like magnesium aluminate spinel (MAS) are considered the next step in material evolution showing unmatched mechanical, chemical and physical resistance combined with high optical transparency. Unfortunately, transparent ceramics are notoriously difficult to shape, especially on the microscale. Therefore, a thermoplastic MAS nanocomposite is developed that can be shaped by polymer injection molding at high speed and precision. The nanocomposite is converted to dense MAS by debinding, pre-sintering, and hot isostatic pressing yielding transparent ceramics with high optical transmission up to 84 % and high mechanical strength. A transparent macroscopic MAS components with wall thicknesses up to 4 mm as well as microstructured components with single micrometer resolution are shown. This work makes transparent MAS ceramics accessible to modern high-throughput polymer processing techniques for fast and cost-efficient manufacturing of macroscopic and microstructured components enabling a plethora of potential applications from optics and photonics, medicine to scratch and break-resistant transparent windows for consumer electronics.


Assuntos
Cerâmica , Nanocompostos , Polímeros
19.
Nanomaterials (Basel) ; 12(14)2022 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-35889689

RESUMO

The mechanical and wear behavior of CrN/CrAlN multilayers were improved by tailoring the experimental conditions of a hybrid magnetron sputtering process based on a high-power impulse (HiPIMS) and two direct current magnetron sputtering (dcMS) power supplies. To this end, the influence of the base layer and of the combination of Cr and CrAl targets, which were switched to the dcMS and HiPIMS power supplies in different configurations, were investigated with respect to the growth of ceramic CrN/CrAlN multilayers onto commercial gas-nitrided diesel piston rings. The microstructure, grain morphology, and mechanical properties were evaluated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and instrumented nanoindentation. Bench wear tests simulating the operation of a combustion engine were conducted against a gray cast iron cylinder liner under reciprocating conditions using 0W20 oil as a lubricating agent enriched with Al2O3 particles. The results revealed a significant increase in hardness, resistance to plastic strain, and wear resistance when two CrAl targets were switched to a HiPIMS and a dcMS power supply, and a Cr target was powered by another dcMS power supply. The compressive coating stresses were slightly reduced due to the soft Cr base layer that enabled stress relief within the multilayer. The proposed concept of hybrid magnetron sputtering outperformed the commercial PVD coatings of CrN for diesel piston rings manufactured by cathodic arc evaporation.

20.
Nano Lett ; 10(11): 4640-5, 2010 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-20929204

RESUMO

We demonstrate measurement and control of single-asperity friction by using cantilever probes featuring an in situ solid-state heater. The heater temperature was varied between 25 and 650 °C (tip temperatures from 25 ± 2 to 120 ± 20 °C). Heating caused friction to increase by a factor of 4 in air at ∼ 30% relative humidity, but in dry nitrogen friction decreased by ∼ 40%. Higher velocity reduced friction in ambient with no effect in dry nitrogen. These trends are attributed to thermally assisted formation of capillary bridges between the tip and substrate in air, and thermally assisted sliding in dry nitrogen. Real-time friction measurements while modulating the tip temperature revealed an energy barrier for capillary condensation of 0.40 ± 0.04 eV but with slower kinetics compared to isothermal measurements that we attribute to the distinct thermal environment that occurs when heating in real time. Controlling the presence of this nanoscale capillary and the associated control of friction and adhesion offers new opportunities for tip-based nanomanufacturing.


Assuntos
Nanoestruturas/química , Nanoestruturas/ultraestrutura , Fricção , Calefação/métodos , Teste de Materiais , Tamanho da Partícula
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