This work is supported by the National Institute of Standards and Technology of the United States Department of Commerce.

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The authors declare no competing financial interests. Commercial materials, instruments and equipment are identified in this paper to specify the experimental procedure as completely as possible. In no case does such identification imply a recommendation or endorsement by the National Institute of Standards.

לאחר הרכישה של דגימות בתפזורת באיכות גבוהה, המתאפיינות על מנת להבטיח הרכב ומבנה מתאימים, דגימות בדוגמת לגיאומטריה מתוארת על ידי פילינג פתיתים של מדגם על סנטימטר 1 × 1 חתיכות של מצע סנטימטר. מצעים מורכבים של Si כבדות מסומם עמ &#39;מכוסים על ידי כ -300 ננומטר של SiO 2 הם הע...

המרדף של פלטפורמות חומרים לטכנולוגית אלקטרוניקה מתקדמת דורש שיטות לסינתזת חומרי תפוקה גבוהה ואפיון שלאחר מכן. חומרים חדשים של עניין במרדף זה יכול להיות מיוצרים בכמויות גדולות על ידי סינתזה ישירה תגובת 1,2, 3,4 צמיחה אלקטרוכימיים, ושיטות אחרות 5 באופנה מהירה יותר מאשר טכניקות מעורבות יותר גביש יחיד דקות בתצהיר סרט כגון epitaxy קרן מולקולרי או שיקוע כימי. השיטה המקובלת למדידת תכונות הובלת דגימות גביש בתפזורת היא לדבוק שבר בצורת מנסרה מלבני עם ממדים של כ 1 מ&quot;מ x 1 מ&quot;מ x 6 מ&quot;מ ולצרף חוט מוביל למדגם בתצורת בר הול 6. חומרים מסוימים מהווים אתגר בי שיטת התפזורת המסורתית בר אולם ייצור מכשיר אינה מספיקה כדי לייצר מכשיר למדידה למדידת תחבורת מדגם. זה יכול להיות להיותלגרום לגבישים מיוצרים הם קטנים מדי כדי לצרף חוטים להוביל ל, אפילו תחת מיקרוסקופ אופטי רב עוצמה, משום שעובי המדגם הרצוי הוא בסדר הגודל של אחד לרק כמה monolayers, או משום שאחד נועד למדוד ערימה של דו-ממדי שכבתיים חומרים בעובי של כמעט או תת-ננומטר. הקטגוריה הראשונה כוללת, לדוגמא nanowires והכנות מסוימות של תחמוצת מוליבדן ארד 7. הקטגוריה השנייה כוללת למאוד-כמה שכבות בודדות של חומרים דו-ממדיים כגון גרפן 8, TMDS (MOS 2, WTe 2, וכו &#39;), ומבודדי טופולוגי (Bi 2 Se 3, Bi x Sb 1-x טה 3 , וכו &#39;). הקטגוריה השלישית מורכבת מheterostructures שהוכן על ידי לערום שכבות בודדות של חומרים דו-ממדיים על ידי הרכבה ידנית באמצעות העברת שכבה, בעיקר ערימה התלה-שכבתית של hBN-גרפן-hBN 9. מחקר גישוש של דואר רומןחומרי lectronic דורשים שיטות נאותות לייצור מכשירים בדגימות קשה-מידה. לעתים קרובות, את המנה הראשונה של חומר חדש מסונתז על ידי תגובה ישירה או צמיחה אלקטרוכימיים מניבה גבישים יחידים קטנים מאוד עם ממדים על סדר הגודל של מיקרון. דגימות כאלה הוכיחו היסטוריים קשות מאוד לצרף מגעים מתכת ל, המחייב שיפור של פרמטרים צמיחת מדגם כדי להשיג גבישים גדולים יותר לייצור מכשיר תחבורה קל יותר, המציגים מכשול במחקר התפוקה גבוהה של חומרים חדשים. על מנת לאפשר אפיון מהיר של חומרים, שיטה של ​​ייצור מכשיר למדגמים קטנים מאוד כבר המציאה כדי לאפשר האפיון של חומרים חדשים בהקדם אצווה ראשוני הופק. וריאציה קלה של מתודולוגיה זו חלה על ייצור מכשירים באמצעות דגימות מודבק של חומרים דו-ממדיים כגון גרפן, hBN, וTMDS, כמו גם heterostructures רב-השכבתי של ma כזהterials. התקנים הם דבקו וחוט-ערובה לחבילה להכנסה לתוך מגנט מוליך מסחרי, מערכת הליום יבשה קרוב מחזור magnetotransport cryostat. מדידות תחבורה נלקחות בטמפרטורות עד 0.300 K ושדות מגנטיים עד 12 ט

<table border="0" cellpadding="0" cellspacing="0" width="840">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Cryogenic Limited 12T CFMS</td>
			<td style="width:89px;">Cryogen Limited</td>
			<td style="width:135px;">CFM-12T-H3- IVTI-25</td>
			<td style="width:417px;">Magnetotransport system customized with modulated field magnet (step 4)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">7270 DSP Lock-in amplifier</td>
			<td style="width:89px;">Signal Recovery</td>
			<td style="width:135px;">7270</td>
			<td style="width:417px;">lock-in amplifier for source/drain and voltage measurements (step 4)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">GS200 DC Voltage/Current Source</td>
			<td style="width:89px;">Yokogawa</td>
			<td style="width:135px;">GS200</td>
			<td style="width:417px;">Voltage source for gate voltage application (step 4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">2636B System Sourcemeter</td>
			<td style="width:89px;">Keithley</td>
			<td style="width:135px;">2636B</td>
			<td style="width:417px;">Sourcemeter for source/drain and voltage measurements</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">DWL 2000 Laser Pattern Generator</td>
			<td style="width:89px;">Heidelberg Instruments</td>
			<td style="width:135px;">DWL 2000</td>
			<td style="width:417px;">Generate chrome mask for lithography of substrate location/alignment feature pattern (step 1.3)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Suss MicroTec MA6/BA6 Contact Aligner</td>
			<td style="width:89px;">Suss</td>
			<td style="width:135px;">MA6</td>
			<td style="width:417px;">Used for the lithography of substrate location/alignment feature pattern (step 1.4.12)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">JEOL Direct Write Electron Beam Lithography System</td>
			<td style="width:89px;">JEOL</td>
			<td style="width:135px;">JBX 6300-FS&#160;</td>
			<td style="width:417px;">Perform high-resolution lithography of devices</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Discovery 550 Sputtering System</td>
			<td style="width:89px;">Denton Vacuum</td>
			<td style="width:135px;">Discovery 550</td>
			<td style="width:417px;">Perform SiO2 sputtering (step 2.5)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Infinity 22 Electron Beam Evaporator</td>
			<td style="width:89px;">Denton Vacuum</td>
			<td style="width:135px;">Infinty 22</td>
			<td style="width:417px;">Perform Cr/Au deposition (steps 1.5 and 3.7)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Unaxis 790 Reactive Ion Etcher</td>
			<td style="width:89px;">Unaxis</td>
			<td style="width:135px;">Unaxis 790</td>
			<td style="width:417px;">Etch sample into Hall bar structure (step 3.4)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">Name</td>
			<td style="width:89px;">Company</td>
			<td style="width:135px;">Catalog Number</td>
			<td style="width:417px;">Comments</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">PMMA 495 A4</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">PMMA 495 A4</td>
			<td style="width:417px;">Polymer coating/electron beam mask for lithography (step 3.5.1)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">PMMA 950 A4</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">PMMA 950 A4</td>
			<td style="width:417px;">Polymer coating/electron beam mask for sample dicing and lithography (steps 1.7.3, 3.3.1, and 3.5.2)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">S1813 positive photoresist</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">S1813 G2</td>
			<td style="width:417px;">Positive photoresist (step 1.4.8)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:200px;">LOR resist</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">LOR 3A</td>
			<td style="width:417px;">Lift off resist (step 1.4.3)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1:3 MIBK:IPA PMMA developer</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">1:3 MIBK:IPA</td>
			<td style="width:417px;">PMMA developer</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">MF-321 Developer</td>
			<td style="width:89px;">MicroChem</td>
			<td style="width:135px;">MF-321</td>
			<td style="width:417px;">Novolac positive photoresist-compatible developer solution (step 1.4.15)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Diglycidiyl ether-terminated polydimethylsiloxane</td>
			<td style="width:89px;">Sigma Aldrich</td>
			<td style="width:135px;">SA 480282</td>
			<td style="width:417px;">For layered material stacking (step 2.6.1)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:200px;">Polypropylene carbonate</td>
			<td style="width:89px;">Sigma Aldrich</td>
			<td style="width:135px;">SA 389021</td>
			<td style="width:417px;">For layered material stacking (step 2.6.2)</td>
		</tr>
	</tbody>
</table>

advanced experimental methods for low-temperature magnetotransport measurement of novel materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

איור 3 מראה מכשיר בר אולם אופייני דוגמת לצורך ניסוי magnetotransport הטמפרטורה נמוך. התמונה האופטית בדמות העליונה מציגה סרגל גראפן / hBN הול מפוברק-בהצלחה; התמונה התחתונה מראה סכמטי מכשיר עם מדינות הקצה לנדאואר-Büttiker שנובעות מהרמות (LLS) לנדאו, מנגנון ?...

Watch this Scientific Journal Video about Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials at JoVE.com

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

שיטות ניסיוניות מתקדמות לטמפרטורה נמוכה Magnetotransport מדידה של חומרים חדשים

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

advanced-experimental-methods-for-low-temperature-magnetotransport

Research

JoVE Journal

Engineering

10.5K Views.  National Institute of Standards and Technology. We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Video: Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel 3D/VR Interactive Environment for MD Simulations, Visualization and Analysis

The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials science, biology, chemistry and physics among many others. A new computational system for the accurate and fast simulation and 3D/VR visualization of nanostructures is presented here, using the open-source molecular dynamics (MD) computer program LAMMPS. This alternative computational method uses modern graphics processors, NVIDIA CUDA technology and specialized scientific codes to overcome processing speed barriers common to traditional computing methods. In conjunction with a virtual reality system used to model materials, this enhancement allows the addition of accelerated MD simulation capability. The motivation is to provide a novel research environment which simultaneously allows visualization, simulation, modeling and analysis. The research goal is to investigate the structure and properties of inorganic nanostructures (e.g., silica glass nanosprings) under different conditions using this innovative computational system. The work presented outlines a description of the 3D/VR Visualization System and basic components, an overview of important considerations such as the physical environment, details on the setup and use of the novel system, a general procedure for the accelerated MD enhancement, technical information, and relevant remarks. The impact of this work is the creation of a unique computational system combining nanoscale materials simulation, visualization and interactivity in a virtual environment, which is both a research and teaching instrument at UC Merced.

A new computational system featuring GPU-accelerated molecular dynamics simulation and 3D/VR visualization, analysis and manipulation of nanostructures has been implemented, representing a novel approach to advance materials research and promote innovative investigation and alternative methods to learn about material structures with dimensions invisible to the human eye.

רומן 3D / VR הסביבה אינטראקטיבית לMD סימולציות, ויזואליזציה וניתוח

The increasing development of computing (hardware and software) in the last decades has impacted scientific research in many fields including materials ...

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

כתיבה ואפיון טמפרטורה הנמוכה של ננו Oxide

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

איתור והשחזור של פלדיום, מתכות זהב וקובלט ממכרה העירונית באמצעות חיישנים / Adsorbents רומן יעודיים עם נקבוביות-בצורת גלגל עגלה ננומטריים

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

המצאה של טמפרטורה נמוכה חיבורים אנכיים-צינורות פחמן תואם עם סמיקונדקטור טכנולוגיה

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

שיטות ניסיוניות לחקירות זיכרון צורה Elastocaloric בהתבסס תהליכי קירור ותיקוף דגם

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Measurement of Outgassing Rates of Steels

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of steels meet the criterion of low outgassing required for high or ultrahigh vacuum applications. However, a given material can present different outgassing rates depending on its manufacturing process or the various pretreatment processes involved during the fabrication. Thus, the measurement of outgassing rates is highly desirable for a specific vacuum application. For this reason, the rate-of-pressure rise (RoR) method is often used to measure the outgassing of hydrogen after bakeout. In this article, a detailed description of the design and execution of the experimental protocol involved in the RoR method is provided. The RoR method uses a spinning rotor gauge to minimize errors that stem from outgassing or the pumping action of a vacuum gauge. The outgassing rates of two ordinary steels (stainless steel and mild steel) were measured. The measurements were made before and after the heat pretreatment of the steels. The heat pretreatment of steels was performed to reduce the outgassing. Extremely low rates of outgassing (on the order of 10&#8722;11 Pa m3 sec&#8722;1 m&#8722;2) can be routinely measured using relatively small samples.

A protocol for the measurement of outgassing rates of hydrogen from ordinary steel vacuum chambers using the rate-of-pressure rise method is presented.

מדידת שיעורי Outgassing של פלדות

Steels are commonly used materials in the fabrication of vacuum systems because of their good mechanical, corrosion, and vacuum properties. A variety of ...

Experimental Procedure for Warm Spinning of Cast Aluminum Components

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to improve material properties. With a wide array of processing parameters which can affect both the shape attained and resulting material properties, this type of processing is notoriously difficult to commission. A simplified, light-duty version of the process has been designed and implemented for full-size automotive wheels. The apparatus is intended to assist in understanding the deformation mechanisms and the material response to this type of processing. An experimental protocol has been developed to prepare for, and subsequently perform forming trials and is described for as-cast A356 wheel blanks. The thermal profile attained, along with instrumentation details are provided. Similitude with full-scale forming operations which impart significantly more deformation at faster rates is discussed.

An experimental protocol for instrumented warm rotary forming of cast aluminum alloys employing a bespoke industrially scaled apparatus is presented. Experimental considerations including thermal and mechanical effects are discussed, as well as similitude with full-scale processing of automotive wheels.

נוהל ניסיוני עבור ספינינג חם של רכיבי אלומיניום יצוקים

High performance, cast aluminum automotive wheels are increasingly being incrementally formed via flow forming/metal spinning at elevated temperatures to ...

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.

שיטה סטנדרטית למדידת יעילות גבייה נגב-דגימה של חומרי נפץ Trace

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 ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

שיטה חדשה עבור<em&gt; באתרו</em&gt; אפיון אלקטרומכני של דגימות ננומטריות

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

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.

מיקרו / ננו בקנה מידה זן הפצה מדידה מדגימה Moiré שוליים

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