A.C. is grateful to KoreaTech for financial support.

1. Instrumental Set-up und Kalibrierung <ol><li> Instrumental Set-up <ol><li> Verwenden Sie einen steifen diamantbeschichteten Ausleger des Typs DT-NCLR oder CDT-NCLR mit einer ersten Frequenz frei Resonanz f 0,1 ≥ 180 kHz, einen Gütefaktor Q ≥ 300 und einer Biegesteifigkeit k ≥ 40 N / m. </li><li> Montieren Sie den ausgewählten Ausleger auf einem Klemmhalter von der AFM-Herstellers. Besondere Vorsicht den Cantilever zu platzieren, so dass seine Längsachse zu der schnellen Abtastrichtung des AFM senkrecht. Alternativ kleben Sie den Ausleger auf einen Halter Ausleger von der AFM-Herstellers Zweikomponenten-Epoxid-Kleber verwendet wird. </li><li> Montieren Sie den Cantileverhalters auf die AFM Kopf und verwenden Sie den optischen Mikroskop normalerweise verfügbar mit dem AFM-System auf der AFM Cantilever zu konzentrieren. Überprüfen Sie, dass die Längsachse des Auslegers senkrecht zur Schnellscanrichtung ist. Wenn nicht, gehen Sie zurück zuAbschnitt 1.1.2. </li><li> Richten des Laserstrahls, so dass er am Ende des Auslegers reflektiert wird. Überwachen Sie die Spannungssumme an der Photodiode und führen Sie eine Feineinstellung des Summensignals zu maximieren. Typische Summensignal-Werte liegen im Bereich von 2 V. </li><li> Einstellen der horizontalen und vertikalen Neigungswinkel des Spiegels, um das reflektierte Laserfleck in der Mitte der Photodiode zu bringen, wo die Spannungen, die an die vertikale und seitliche Verschiebung entspricht nahezu Null. </li></ol></li><li> Kalibrierung <ol><li> Führen Sie einen Frequenz - Sweep die erste freie Biegeresonanz f 0,1 des Auslegers zu bestimmen. </li><li> Bestimmung der Biegesteifigkeit des Auslegers k, berechnet nach 19 (1) <img alt="Gleichung 1" src="/files/ftp_upload/54706/54706eq1.jpg" /> wobei E der Elastizitätsmodul ist, L die Länge des Auslegers, w die Breite des cantil istje, und t ist die Dicke. Dazu messen die Länge und Breite des Auslegers durch optische Mikroskopie oder Rasterelektronenmikroskopie für eine bessere Genauigkeit. Berechnen der Dicke des Auslegers aus seiner ersten Frequenz freie Biegeresonanz f 0,1, entsprechend (2) <img alt="Gleichung 2" src="/files/ftp_upload/54706/54706eq2.jpg" /> wobei ρ die Massendichte. </li><li> Wählen Sie den Standardwert der Photodiode Empfindlichkeit für den jeweiligen Auslegertyp werden für das Experiment im Setup-Menü des AFM verwendet. Bringen Sie die Cantileverspitze in Kontakt mit der Referenzprobe bei einer Last F n = 10 nN durch den Ansatz Knopf klicken. </li><li> Öffnen Sie die Kraftspektroskopie-Menü in der AFM-Software und stellen Sie die relative Ein- und Ausfahren der z-Scanner bis 50 nm und die z-Scanner Rückzug / Erweiterung auf 0,3 &amp; mgr; m / sec. Dadurch könnte die Aufzeichnung der Kraft-Weg-Kurve, die Verteiler,bestehen zunächst aus einem Zurückziehen der z-Scanner 50 nm von der Probenoberfläche entfernt und dann aus einer Reihe von Ansätzen und Einziehungen der gleichen Entfernung. </li><li> Nehmen Sie eine Kraftabstandskurve mit den eingestellten Parametern vorgeschlagen in 1.2.4 auf einer glatten und nicht-konforme Oberfläche, wie nanokristalline Diamant oder Saphir, um Probenverformungseffekte zu vermeiden. Dazu klicken Sie auf die Schaltfläche Acquire in der Kraftspektroskopie - Menü der AFM - Software. </li><li> Den abstoßend Teil der Kraft-Weg-Kurve mit einer linearen Funktion, im Kalibrierungsmenü der AFM-Software. Die inverse Steigung der Fittinglinie entspricht der Photodiode Empfindlichkeit S. Ersetzen Sie den ermittelten Wert auf den Standardwert der Gerätesoftware im Kalibrierungsmenü der AFM - Software durch die Kalibrierungstaste ausführen klicken. </li></ol></li></ol> 2. Probenvorbereitung HINWEIS: Die Probe wird in thi gemessens Experiment besteht aus einer 100 nm dicken, atomar glatten Au (111) dünnen Film auf Mica gewachsen durch physikalische Dampfabscheidung. <ol><li> Montieren Sie die Probe auf einem magnetischen Probenhalter zur Verfügung gestellt vom Hersteller des Instruments mittels eines doppelseitigen Kohlenstoffband. Um Drift der Probe während der Messungen zu vermeiden, montieren Sie die Probe einen Tag vor den Messungen, um die Kohlenstoffband entspannen zu lassen. Alternativ montieren Sie die Probe auf den Halter mit Silberfarbe, die in der Regel innerhalb von wenigen Minuten trocknet. </li><li> Montieren Sie den Magnetprobenhalter auf die x / y-Scanner. </li></ol> 3. Messverfahren <ol><li> Stellen Sie die Schwingungsfrequenz leicht off-resonance (in diesem Experiment f = 190,67 kHz) und der Schwingungsamplitude bei A = 20 nm zu beachten , dass diese Werte automatisch durch die Gerätesoftware für diese bestimmte Cantilevers eingestellt. Stellen Sie den Schwingungssollwert manuell auf einem Soll = 5 nm. </li><li> Zeichnender Ausleger in Richtung auf die Probenoberfläche den Schritt-Motor des AFM verwendet. Stellen Sie sicher, dass der Kraftsensor nicht mit der Probenoberfläche kollidiert. Halten Sie den Ausleger im Fokus während der groben Annäherung und die grobe Annäherung zu stoppen, bevor die Probenoberfläche in perfekter Bildschärfe ist. </li><li> Ansatz automatisch den Kraftsensor durch auf dem Ansatz Knopf klicken. Sobald die Schwingungsamplitude ihren Sollwert erreicht hat, ist die Spitze bereit, um die Topographie der Probenoberfläche abzutasten. </li><li> Nehmen Sie eine Reihe von Topographie Bilder auf Flächen im Bereich von 5 x 5 bis 1 x 1 um² (falls vorhanden, stellen Sie die Neigung des Topographie-Signal durch das Kippen x / y-Scanner). Stellen Sie sicher, dass aufeinanderfolgende Bilder des gleichen Bereichs zeigen keine Zeichen von Drift und dass die z-Scannerposition bleibt nahezu konstant. Ist dies nicht der Fall ist, weiterhin Abbildungs ​​bis das System stabilisiert hat. </li><li> Sobald sich das System stabilisiert hat und eine glatte 1 x 1 um² Bereich gefunden wurde, ziehen sich die force Sensor wenige Mikrometer von der Oberfläche der Probe auf der Rückzugs - Taste anklicken. </li><li> Wählen Sie die Kraftspektroskopie-Modus im Gerätemenü und bewegen Sie den Kraftsensor auf der Mitte des vorgewählten 1 x 1 um² Bereich, mit einer Kraft-Sollwert von 10 nm. Überwachen der Position des z-Abtaster, bis sie konstant bleibt. </li><li> Wählen Sie die 2 x 2 Punktraster, dessen Mittelpunkt entspricht dem Zentrum der vorgewählten 1 x 1 um² Fläche. Die Entfernung zwischen zwei benachbarten Punkten nächsten bei 500 nm. </li><li> Stellen Sie den relativen Abstand scanner 0-150 nm zu variieren bei einer Geschwindigkeit von 300 nm / sec und dann zurückziehen über den gleichen Abstand und mit der gleichen Geschwindigkeit. Gegeben gelten den Neigungswinkel des Auslegers in Bezug auf die Probenoberfläche, eine Neigungskorrektur durch den seitlichen Scanner durch Z × tan φ Bewegen während eines vertikalen Scanners Verlängerungs Z, wobei φ der Neigungswinkel 20. HINWEIS: Ein paar instruments Konto für den Ausleger Neigung in ihrer Kraftspektroskopie oder Einrückungsmodus; dies ist der Fall für die AFM in dieser Arbeit verwendet. </li><li> Drücken Sie die Start-Taste in der Gerätesoftware den Erwerb der AFM Einzug von Daten zu beginnen. </li><li> Sobald die AFM Indentationsmessungen abgeschlossen haben, fahren Sie das Kraftsensor wenige Mikrometer von der Probenoberfläche entfernt. </li><li> Wählen Sie den berührungslosen AFM-Modus-Bildgebung in der Gerätesoftware-Menü und wiederholen Sie den beschriebenen Verfahren in den Abschnitten 3.1 und 3.2. </li><li> Führen Sie einen Scan über den gleichen 1 x 1 um² Oberfläche, wie in Abschnitt 3.3, um die genaue Position der Einzüge zu lokalisieren. Weitere Oberflächenscans über einen 500 x 500 nm² Oberfläche kann die verbleibenden Einzüge mit näher Bild durchgeführt werden. </li></ol> 4. Datenanalyse <ol><li> Bildverarbeitung <ol><li> Verarbeiten Sie die aufgezeichneten Bilder Topographie, um die Linien in der Schnellscan dir ausrichtenEIL basierend auf mittlere Differenz. Verwenden Sie die integrierte Funktion von Gwyddion. </li></ol></li><li> Berechnen Sie die projizierte Fläche A p von Einrückungen die Vertiefung Analysefunktion von Gwyddion verwenden. </li><li> Schätzen Sie die AFM - Spitze Form der Topographiebilder von Einrückungen durch die Spitze Analysefunktion von Gwyddion verwenden. Dann Mittelwert der Spitzenform Bilder und messen Sie die Halböffnungswinkel α der gemittelten Spitzenform. </li><li> Konvertieren Sie die Kraft-Weg - Kurven in Kraft- Weg -Kurven , die durch die Spitze Verschiebung Berechnung δ gemäß 13 (3) <img alt="Gleichung 3" src="/files/ftp_upload/54706/54706eq3.jpg" /> wobei Z die relative Scannerposition. </li><li> Nun zeichnen Sie die Kraft gegenüber der Spitze Verschiebung. Die resultierende Kurve zeigt in der Regel so genannte Pop-Ins, mit Längen im Bereich von mehreren 100 pm, die auf atomistischen Plastizität Ereignisse entsprechen. Verwenden Sie die erste von these Pop-Ins die Spitze Verschiebung an der Elastizitätsgrenze δ el 4 zu bestimmen. </li><li> Den elastischen Teil der Kraft- Weg -Kurve mit der Hertzian Funktion 21. (4) <img alt="Gleichung 4" src="/files/ftp_upload/54706/54706eq4.jpg" /> wobei R der Spitzenradius und E &#39;* der reduzierte Elastizitätsmodul, gegeben durch <img alt="Gleichung 5" src="/files/ftp_upload/54706/54706eq5.jpg" /> Mit M s, t die Einbuchtung Modul der Probe und der Spitze ist, respectively. In diesem Fall ist die Fitparameter <img alt="Gleichung 6" src="/files/ftp_upload/54706/54706eq6.jpg" /> . </li><li> Verlängern Sie die Anpassungsfunktion in die Plastizität Regime , um die Arbeit der Plastizität W Plastizität von der Flächendifferenz zwischen der Anpassungsfunktion und der experimentellen Kurve 21 zu berechnen. </li><li> Berechne die Härte der Probe nach 1, 2 (5) <img alt="Gleichung 7" src="/files/ftp_upload/54706/54706eq7.jpg" /> und (6) <img alt="Gleichung 8" src="/files/ftp_upload/54706/54706eq8.jpg" /> wobei F n, die maximale max Last angelegt ist, ist A p die projizierte Fläche des in Abschnitt berechnet Gedankenstrich 4.2, α der halbe Öffnungswinkel der Spitze in Abschnitt 4.3, δ el ist die Spitze Verschiebung bei der ersten Plastizität berechnet ist Ereignis und δ max ist die maximale Spitze Verschiebung (siehe Abschnitt 4.4). </li></ol>

<ol>
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The authors have nothing to disclose.

Es wurde ein Verfahren zum Durchführen einer Reihe von Vertiefungen auf einer Au (111) Dünnfilmoberfläche mit einem Diamantbeschichtetes AFM-Spitze dargestellt. Berührungslos AFM-Bildgebung und AFM Vertiefung wurden mit dem gleichen Kraftsensor ausgeführt. Die Anforderungen für die berührungslose Bildgebung eine hohe erste freie Resonanzfrequenz f 0,1 ≥ 180 kHz und einem hohen Qualitätsfaktor Q ≥ 300. In AFM Vertiefung sind, die vertikale Kraft im Bereich von mehreren Mikronewton...

For the last 150 years, hardness values have been used to characterize the mechanical behavior of materials and to predict their performance under various loading conditions. The hardness of a material describes the resistance of its surface to the penetration of a harder indenter. For metallic materials, the hardness relates to resistance to plastic flow.
Although the implementation of hardness testing has proven to be relatively easy, the yielded results have long been rather empirical, making them unable to describe the intrinsic properties of the investigated material. The empirical nature of hardness testing results has been a consequence of the use of various indenter geometries, each of which has a different established hardness scale. However, all empirical hardness scales, such as the Brinell hardness (HB) test for spherical indenters and the Vickers (HV) and Knoop (HK) hardness tests for different types of four-sided pyramids, have one thing in common: the hardness number is determined from the ratio of the applied load to the developed area of the remaining indent. In an attempt to relate the hardness of metals to their fundamental mechanical properties, the hardness measured with a spherical indenter has been defined as the ratio of the applied load to the projected area of the remaining indent. This hardness value, also known as the Meyer's hardness (H), is equal to the mean contact pressure and directly relates to the yield strength of non-work-hardening metals1. 
Hardness testing has long been limited to the macro-scale, in which case the sizes of indents have been measured by optical means. The development of instrumented indentation, where force-displacement curves are recorded, has been recognized as a valuable alternative for determining the hardness of a material, although the size of the remaining indent may be too small to be accurately imaged. In this case, the projected area of the indent is calculated from the tip displacement according to a so-called indenter-area function2. Due to this development, the analysis of the curvature of force-displacement curves and of the occurrence of distinct plasticity events in the shape of pop-ins is now widely used to study the mechanisms of plastic deformation at the micrometer scale, such as by means of nanoindentation3.
It is well accepted that the carriers of plastic deformation in metals, i.e., dislocations, operate at the nanometer scale. To understand their modes of operation at the atomic level, new experimental techniques with atomic resolution are needed. Initial investigations of atomistic plasticity events at the interfaces between nanometer-sized single asperities and single crystalline Au surfaces of different orientations have been carried out by interfacial force microscopy (IFM)4, 5. Atomic force microscopy (AFM) indentation has been applied to observe the nucleation and gliding of single dislocations in KBr(100) single crystals6, Cu(100)7, and Au(111)8, 9. There, atomistic plasticity events were observed in the shape of pop-ins, with lengths in the range of 1 &#197;. AFM indentation has also been used to measure the nano-hardness and -elasticity of gold nano-island grown on mica10. In this work, the nano-hardness was found to be smaller than the bulk value and was observed to depend linearly on the indentation area. Also, a detailed measurement protocol has been proposed to determine the hardness of hard surfaces, such as fused quartz and silicon, by AFM indentation with a diamond-tipped sapphire cantilever11. In particular, this method takes into account the non-linearity of the photo-sensitive deflection detectors for large cantilever deflection12. More recently, AFM indentation and non-contact AFM imaging have been combined to quantitatively determine the hardness and the fundamental mechanisms of plastic deformation of a Pt(111) single crystalline surface and Pt-based metallic glass13. For Pt(111), plastic deformation mechanisms at the nanometer scale were found to be consistent with the discrete mechanisms established for larger scales. Further, the nanometer-scale plastic deformation of the metallic glass was found to be not discrete, but rather continuous and highly localized around the indenting tip. These results revealed a lower size limit for metallic glasses, below which shear transformation mechanisms are not activated by indentation. AFM indentation has also been used to determine the hardness values of biological samples (such as collagen fibrils)14, polymers15, and colloidal crystals16.
In the present work, a careful experimental procedure is described that includes the force sensor selection, its calibration, the calibration of the cantilever deflection detection system, and the minimization of instrumental drift for accurate and reproducible force-distance measurements. Also, a method for the data analysis is presented that allows the extraction of force-penetration curves from recorded force-distance curves. Further representative results are shown and discussed in the light of recent findings in the field of plastic deformation of small volumes.
For this experiment, an atomic force microscope (AFM) was used. The cornerstone of an AFM is its micro-fabricated force sensor (usually a cantilever beam), with a sharp tip at the end whose radius is in the range of several nanometers. In the particular configuration of the instrument used for this experiment, the cantilever is mounted onto a piezo-electric z-scanner, while the sample to be investigated is mounted onto a piezo-electric x/y-scanner. During AFM imaging, the force sensor tip is scanned over a sample to register interaction forces with the sample surface that result in a deflection of the cantilever according to Hooke's law. The static or dynamic deflection of the cantilever can be measured with an optical beam deflection detector, consisting of a laser diode, a set of mirrors, and a photodiode that converts the cantilever deflection into a voltage. During imaging, the signal at the photodiode is controlled by a feedback loop so as to keep the interaction forces at the sample surface; this results in adjustments of the z-scanner position, which are recorded and displayed as a topography image.
Prerequisites for the experiment described below are that the piezo-electric scanners of the atomic force microscope are well-calibrated and that the instrument stays in the laboratory at a constant temperature and humidity level. The reader should be aware that, depending on the atomic force microscope model, some of the experimental procedure steps may have to be modified. In particular, all measurements are performed after setting the scanners' ranges to "small"; this function allows for the reduction of the x/y-scanner range to 5 x 5 &#181;m&#178; and the z-scanner range to 4 &#181;m, which ensures a resolution at small scales. This function is not available on all commercial AFM and is not mentioned in the remainder of the text.
For data analysis, the use of the free SPM data analysis software Gwyddion17 and the Matlab software package18 are recommended.
This protocol gives a description of the experimental procedure to be followed in order to perform instrumented hardness measurements by AFM. Since the handling of different commercial AFMs may differ from one model to the other, the reader should refer to the manual provided by the AFM manufacturer for detailed setting procedures and software information. In the following text, in order to reproduce the described experiment, it is assumed that the reader is familiar with the handling of the particular AFM used here.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">AFM XE-100</td>
			<td style="width:71px;">Park Instruments</td>
			<td style="width:119px;">discontinued</td>
			<td style="width:167px;">Atomic force microscope</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">CDT-NCLR</td>
			<td style="width:71px;">NanoSensors</td>
			<td style="width:119px;">CDT-NCLR</td>
			<td>Conductive diamond coated non-contact lever</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">100 nm thick Au(111) thin film on Mica</td>
			<td style="width:71px;">Phasis</td>
			<td align="right">20020011</td>
			<td>atomically smooth gold thin film</td>
		</tr>
	</tbody>
</table>

quantitative hardness measurement by instrumented afm-indentation

In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness measurements on an Au(111) surface with atomistic resolution of single plasticity events. A careful experimental procedure is described that includes the force sensor selection, its calibration, the calibration of the cantilever deflection detection system, and the minimization of instrumental drift for accurate and reproducible force-distance measurements. Also, a method for the data analysis is presented that allows the extraction of force-penetration curves from recorded force-distance curves. A typical curve displays a clear elastic deformation regime up to the first plasticity event, or pop-in, with a length in the range of one to two Burger's vectors. Later plasticity events exhibit the same magnitude. The work of plasticity is further extracted from the measurements. Finally, the hardness is determined in combination with the indentation curve using non-contact atomic force microscopy images of the remaining indents.

In dieser Arbeit wurde die Biegesteifigkeit des Auslegers k berechnet sich nach der geometrischen Balkentheorie 19. Für die spezielle diamantbeschichteten Ausleger in dieser Arbeit verwendeten, fanden wir k = 55,69 N / m. Beachten Sie, dass wir die Diamantbeschichtung vernachlässigt; die Dicke der Diamantschicht beträgt ein bis zwei Größenordnungen kleiner als der Auslegerdicke und damit nicht signifikant seine Biegesteifigkeit nicht erhöht (obwohl sein...

Watch this Scientific Journal Video about Quantitative Hardness Measurement by Instrumented AFM-indentation at JoVE.com

Quantitative Hardness Measurement by Instrumented AFM-indentation

This experimental protocol describes how atomic force microscopy can be used to measure hardness at the true nanometer scale and to detect single atomistic plasticity events.

Quantitative Härtemessung durch Instrumented AFM-Einzug

In this work, a combination of amplitude-modulated non-contact atomic force microscopy and atomic force spectroscopy is applied for instrumented hardness ...

quantitative-hardness-measurement-by-instrumented-afm-indentation

Research

JoVE Journal

Engineering

9.6K Aufrufe.  KoreaTech, Korea University of Technology and Education. This experimental protocol describes how atomic force microscopy can be used to measure hardness at the true nanometer scale and to detect single atomistic plasticity events. 

Serie: Quantitative Hardness Measurement by Instrumented AFM-indentation

Optical Trap Loading of Dielectric Microparticles In Air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

Optische Trap-Laden von Dielectric Mikroteilchen in der Luft

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

Forschung

Ingenieurwesen

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

Standardisierte Methode für Collection Efficiency Messung von Wipe-sampling of Trace Explosiven

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

Micro/Nano-scale Strain Distribution Measurement from Sampling Moir&#233; Fringes

This work describes the measurement procedure and principles of a sampling moir&#233; technique for full-field micro/nano-scale deformation measurements. The developed technique can be performed in two ways: using the reconstructed multiplication moir&#233; method or the spatial phase-shifting sampling moir&#233; method. When the specimen grid pitch is around 2 pixels, 2-pixel sampling moir&#233; fringes are generated to reconstruct a multiplication moir&#233; pattern for a deformation measurement. Both the displacement and strain sensitivities are twice as high as in the traditional scanning moir&#233; method in the same wide field of view. When the specimen grid pitch is around or greater than 3 pixels, multi-pixel sampling moir&#233; fringes are generated, and a spatial phase-shifting technique is combined for a full-field deformation measurement. The strain measurement accuracy is significantly improved, and automatic batch measurement is easily achievable. Both methods can measure the two-dimensional (2D) strain distributions from a single-shot grid image without rotating the specimen or scanning lines, as in traditional moir&#233; techniques. As examples, the 2D displacement and strain distributions, including the shear strains of two carbon fiber-reinforced plastic specimens, were measured in three-point bending tests. The proposed technique is expected to play an important role in the non-destructive quantitative evaluations of mechanical properties, crack occurrences, and residual stresses of a variety of materials.

A sampling moir&#233; technique featuring 2-pixel and multi-pixel sampling methods for high-accuracy strain distribution measurements at the micro/nano-scale is presented here.

Mikro- / Nanometer-Dehnungsverteilungsmessung von Sampling Moiré Fringes

This work describes the measurement procedure and principles of a sampling moir&#233; technique for full-field micro/nano-scale deformation measurements. ...

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. This paper proposes a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation. The polydimethylsiloxane (PDMS) chip was fabricated using the multi-layer soft lithography method. Hexadecane containing surfactant was used as the continuous phase, and PEGDA with the ultraviolet (UV) photo-initiator was the dispersed phase. Surfactants allowed the local surface tension to drop and formed a more cusped tip which promoted breaking into tiny micro-droplets. As the pressure of dispersed phase was constant, the size of droplets became smaller with increasing continuous phase pressure before dispersed phase flow was broken off. As a result, droplets with size variation from 1 &#181;m to 80 &#181;m in diameter could be selectively achieved by changing the pressure ratio in two inlet channels, and the average coefficient of variation was estimated to be below 7%. Furthermore, droplets could turn into micro-beads by UV exposure for photo-polymerization. Conjugating biomolecules on such micro-beads surface have many potential applications in the fields of biology and chemistry.

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Here, we present a protocol to illustrate the fabrication processes and verifying experiments of a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation.

Größe-gesteuerte Poly (Ethylenglycol) Diacrylate Tröpfchen über Semi-3-dimensionale fließen mit Schwerpunkt mikrofluidischen Geräte-Generation

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...

Quantitative Analysis of Vacuum Induction Melting by Laser-induced Breakdown Spectroscopy

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves several steps, include drawing samples, cooling, cutting, transport to the laboratory, and analysis. The whole analysis process requires more than 30 minutes, which hinders on-line process control. Laser-induced breakdown spectroscopy is an excellent on-line analysis method that can satisfy the requirements of vacuum induction melting because it is fast and noncontact and does not require sample preparation. The experimental facility uses a lamp-pumped Q-switched laser to ablate melted liquid steel with an output energy of 80 mJ, a frequency of 5 Hz, a FWHM pulse width of 20 ns, and a working wavelength of 1,064 nm. A multi-channel linear charge coupled device (CCD) spectrometer is used to measure the emission spectrum in real time, with a spectral range from 190 to 600 nm and a resolution of 0.06 nm at a wavelength of 200 nm. The protocol includes several steps: standard alloy sample preparation and an ingredient test, smelting of standard samples and determination of the laser breakdown spectrum, and construction of the elements concentration quantitative analysis curve of each element. To realize the concentration analysis of unknown samples, the spectrum of a sample also needs to be measured and disposed with the same process. The composition of all main elements in the melted alloy can be quantitatively analyzed with an internal standard method. The calibration curve shows that the limit of detection of most metal elements ranges from 20-250 ppm. The concentration of elements, such as Ti, Mo, Nb, V, and Cu, can be lower than 100 ppm, and the concentrations of Cr, Al, Co, Fe, Mn, C, and Si range from 100-200 ppm. The R2 of some calibration curves can exceed 0.94.

During vacuum induction melting, laser-induced breakdown spectroscopy is used to perform real-time quantitative analysis of the main-ingredient elements of a molten alloy.

Quantitative Analyse der Vakuum-Induktionsschmelze durch Laser-induzierte Spectroskopie

Vacuum induction melting is a popular method for refining high purity metal and alloys. Traditionally, standard process control in metallurgy involves ...

A Random-displacement Measurement by Combining a Magnetic Scale and Two Fiber Bragg Gratings

Long-distance displacement measurements using optical fibers have always been a challenge in both basic research and industrial production. We developed and characterized a temperature-independent fiber Bragg grating (FBG)-based random-displacement sensor that adopts a magnetic scale as a novel transferring mechanism. By detecting shifts of two FBG center wavelengths, a full-range measurement can be obtained with a magnetic scale. For identification of the clockwise and counterclockwise rotation direction of the motor (in fact, the direction of movement of the object to be tested), there is a sinusoidal relationship between the displacement and the center wavelength shift of the FBG; as the anticlockwise rotation alternates, the center wavelength shift of the second FBG detector shows a leading phase difference of around 90&#176; (+90&#176;). As the clockwise rotation alternates, the center wavelength shift of the second FBG displays a lagging phase difference of around 90&#176; (-90&#176;). At the same time, the two FBG-based sensors are temperature independent. If there is some need for a remote monitor without any electromagnetic interference, this striking approach makes them a useful tool for determining the random displacement. This methodology is appropriate for industrial production. As the structure of the whole system is relatively simple, this displacement sensor can be used in commercial production. In addition to it being a displacement sensor, it can be used to measure other parameters, such as velocity and acceleration.

A protocol to create a full-range linear displacement sensor, combining two packaged fiber Bragg grating detectors with a magnetic scale, is presented.

Eine Zufällige Verschiebungsmessung durch Kombination einer magnetischen Skala und zwei Faser-Bragg-Gitter

Long-distance displacement measurements using optical fibers have always been a challenge in both basic research and industrial production. We developed ...

Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, with its peak locomotion speed reaching 150 cm/s. First of all, we observed the microstructure and hierarchy of water strider legs using the scanning electron microscope. On the basis of the observed morphology of the legs, a theoretical model of the detachment from water surface was established, which explained water striders' capability to slide on water surface effortlessly in terms of energy reduction. Secondly, a dynamic force measurement system was devised using the PVDF film sensor with excellent sensitivity, which could detect the whole interaction process. Subsequently, a single leg in contact with water was pulled upward at different speeds, and the adhesion force was measured at the same time. The results of the departing experiment suggested a deep understanding of the fast jumping of water striders.

The protocol here is dedicated to investigating the free and quick maneuvering of water strider on water surface. The protocol includes observing the microstructure of legs and measuring the adhesion force when departing from water surface at different speeds.

Messung der dynamischen Kraft gehandelt auf Wasser Strider Bein nach oben springen, indem Sie die PVDF Film Sensor

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, ...

Quantitative Analysis by Thermogravimetry-Mass Spectrum Analysis for Reactions with Evolved Gases

During energy conversion, material production, and metallurgy processes, reactions often have the features of unsteadiness, multistep, and multi-intermediates. Thermogravimetry-mass spectrum (TG-MS) is seen as a powerful tool to study reaction features. However, reaction details and reaction mechanics have not been effectively obtained directly from the ion current of TG-MS. Here, we provide a method of an equivalent characteristic spectrum analysis (ECSA) for analyzing the mass spectrum and giving the mass flow rate of reaction gases as precise as possible. The ECSA can effectively separate overlapping ion peaks and then eliminate the mass discrimination and temperature-dependent effect. Two example experiments are presented: (1) the decomposition of CaCO3 with evolved gas of CO2 and the decomposition of hydromagnesite with evolved gas of CO2 and H2O, to evaluate the ECSA on single-component system measurement and (2) the thermal pyrolysis of Zhundong coal with evolved gases of inorganic gases CO, H2, and CO2, and organic gases C2H4, C2H6, C3H8, C6H14, etc., to evaluate the ECSA on multi-component system measurement. Based on the successful calibration of the characteristic spectrum and relative sensitivity of specific gas and the ECSA on mass spectrum, we demonstrate that the ECSA accurately gives the mass flow rates of each evolved gas, including organic or inorganic gases, for not only single but multi-component reactions, which cannot be implemented by the traditional measurements.

Precise determination of the evolved gases&#39; flow rate is key to study the details of reactions. We provide a novel quantitative analysis method of equivalent characteristic spectrum analysis for thermogravimetry-mass spectrum analysis by establishing the calibration system of the characteristic spectrum and relative sensitivity, for obtaining the flow rate.

Quantitative Analyse von Thermogravimetrie-Masse-Spektrumanalyse für Reaktionen mit weiterentwickelten Gasen

During energy conversion, material production, and metallurgy processes, reactions often have the features of unsteadiness, multistep, and ...

Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (&#60;0.05 mm) layers of high-performance yarns, where the yarns in each layer are oriented parallel to each other and held in place using binder resins and thin polymer films. The armor is constructed by stacking the unidirectional layers in different orientations. To date, only very preliminary work has been performed to characterize the ageing of the binder resins used in unidirectional laminates and the effects on their performance. For example, during the development of the conditioning protocol used in the National Institute of Justice Standard-0101.06, UD laminates showed visual signs of delamination and reductions in V50, which is the velocity at which half of the projectiles are expected to perforate the armor, after ageing. A better understanding of the material property changes in UD laminates is necessary to comprehend the long-term performance of armors constructed from these materials. There are no current standards recommended for mechanically interrogating unidirectional (UD) laminate materials. This study explores methods and best practices for accurately testing the mechanical properties of these materials and proposes a new test methodology for these materials. Best practices for ageing these materials are also described.

The goal of the study was to develop protocols to prepare consistent specimens for accurate mechanical testing of high-strength aramid or ultra-high-molar-mass polyethylene-based flexible unidirectional composite laminate materials and to describe protocols for performing artificial ageing on these materials.

Schneidverfahren, Zugprüfung und Alterung flexibler unidirektionaler Verbundlaminate

Many body armor designs incorporate unidirectional (UD) laminates. UD laminates are constructed of thin (&#60;0.05 mm) layers of high-performance yarns, ...

Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of data that can be obtained from an individual sample and renders it difficult to produce statistically relevant data for unique and rare materials. Resonant cavity dielectric spectroscopy is a non-destructive, contactless technique which can simultaneously interrogate both sides of a sheeted material and provide measurements which are suitable for statistical interpretations. This offers analysts the ability to quickly discriminate between sheeted materials based on composition and storage history. In this methodology article, we demonstrate how contactless resonant cavity dielectric spectroscopy may be used to differentiate between paper analytes of varying fiber species compositions, to determine the relative age of the paper, and to detect and quantify the amount of post-consumer waste (PCW) recycled fiber content in manufactured office paper.

A protocol for the non-destructive analysis of the fiber content and relative age of paper.

Methodenentwicklung für kontaktlose Resonanzhöhlen dielektrische spektroskopische Studien von Cellulosic Paper

The current analytical techniques for characterizing printing and graphic arts substrates are largely ex situ and destructive. This limits the amount of ...