This study received support from the Research Initiation Grant (RIG) of the Vice President for Research and Economic Development at the University of North Texas (UNT). The authors also thank KCIS Co. Ltd for partially supporting this study. The support from PACCAR Technology Institute at UNT to the success of this publication is greatly appreciated.

1. Planning of Experiment
<ol>
	<li>Draw a sacrificial pattern (an octet truss structure with a sprue system) using computer aided design (CAD) software as shown in Figure 1 and save the CAD model as an STL file format. 
	Note: The sacrificial pattern is an integrated pattern of the octet truss structure with a sprue system that will be eventually melted for casting. Because the sacrificial pattern includes both the octet truss structure and the sprue system, it does not exactly represent the octet truss itself. A STL file of the sacrificial pattern is provided. Record the volume of the sacrificial pattern provided by CAD software, which will be used for calculating metals&#39; mass.</li>
	<li>Open the CAD drawing of the sacrificial pattern on the 3D printing software connected to a 3D printer for printing the pattern.</li>
	<li>Ensure that the 3D printer has enough UV curable/castable acrylic plastic and a support material made of a wax in the printer cartridges.</li>
</ol>
2. Fabrication of Sacrificial Pattern
<ol>
	<li>Manufacture the sacrificial pattern consisting of the octet truss structure and the sprue system using a 3D printer (Figure 2A - C). 
	Note: Processes in 2.1.3 - 2.1.7 are not required if a 3D printer which does not generate supporting materials is used.
	<ol>
		<li>Send an STL file of the sacrificial pattern to the 3D printer to print a sacrificial pattern (Figure 2A).</li>
		<li>Melt out a support material of the sacrificial pattern in an oven at above the melting temperature of the support material (60 -&#160;70 &#778;C) for 2 hr (Figure 2B). 
		Note: The temperature to remove the support material should not be too high. Otherwise, it may cause damage to the sacrificial pattern. The sacrificial pattern starts getting damaged at around 80 &#778;C &#160;in this study. 
		Note: The melting temperature of support materials varies with 3D printers where different support materials may be used.</li>
		<li>Fill out a digital ultrasonic cleaner with baby oil up to 2.5 L, the maximum volume that the cleaner can contain (Figure 2C). 
		Note: It was recommended by the supplier of the 3D printer to use baby oil for dissolving residue of the wax-like support material.</li>
		<li>Put the sacrificial pattern into the digital ultrasonic cleaner and turn on the power of the cleaner (Figure 2C). Make sure that the sacrificial pattern is fully submerged in the oil.</li>
		<li>Remove residue of the support material by dipping the sacrificial pattern into the oil at 65 &#778;C &#160;for 40 min (Figure 2C).</li>
		<li>Take out the sacrificial pattern from the cleaner if the support material is completely removed.</li>
		<li>Have the sacrificial pattern dry with a fan at RT (~20 &#778;C) &#160;(Figure 2C). 
		Note: It takes about 2 hr until the oil on the surface of the sacrificial pattern is fully dried. Consider the sacrificial pattern to be fully dried if the surface is not sticky.</li>
	</ol>
	</li>
</ol>
3. Fabrication of Mold
<ol>
	<li>Pattern Assembly
	<ol>
		<li>Attach a rubber gasket to the sacrificial pattern (the octet truss with the sprue system) and place them on the bottom of a cylinder-shaped flask with a height of 6.35 cm and a diameter of 6.35 cm (Figure 2D). 
		Note: Prepare two flasks for casting each metal; Al and Cu alloys.</li>
		<li>Double check the rubber gasket with the sacrificial pattern is completely attached to the bottom of the flask.</li>
		<li>Wrap the flask with a duct tape so that investment powder-water mixture, whose procedure will be described in the next section, may not leak from the flask.</li>
	</ol>
	</li>
	<li>Preparation of Investment Mold
	<ol>
		<li>Prepare investment powder (CaSO4, &#961; = 1019 kg/m3) of 89 g, which is 87.16 ml. Use a scale for weighing the investment powder. 
		Note: The physical properties of the investment powder are shown in Table 1.</li>
		<li>Pour the investment powder into a mixing bowl (1 L).</li>
		<li>Pour water (114 ml) into the mixing bowl. Use a beaker to measure the volume of water.</li>
		<li>Mix the investment powder with water in the bowl for 3 min. Mix well until there are no lumps in the investment powder-water mixture. Otherwise, it may cause poor surface quality of investment mold. Follow the work-flow, as shown in Figure 3.</li>
		<li>In order to remove air bubbles in the mixture, place the bowl in a vacuum chamber for 90 sec until the air bubbles cannot be seen in the mixture with bare eyes (Figure 3).</li>
		<li>Pour the mixture into a flask embedding the sacrificial pattern and the rubber gasket (Figure 2E).</li>
		<li>Place the flask in the vacuum chamber again for 90 sec to remove the residue of air bubbles inside the mixture (Figure 3).</li>
		<li>Dry the mixture inside the flask until it is hardened at RT (Figure 3). 
		Note: Usually, it takes about 10 - 15 min for the mixture to be hardened at RT.</li>
		<li>Remove the flask and the rubber gasket at the bottom of the mixture in the flask once the mixture is hardened (Figure 3). This product may be called a plaster mold.</li>
	</ol>
	</li>
	<li>Burn-out
	<ol>
		<li>Set up a burn-out time in a furnace while following the heating and cooling schedule (Figure 4) heating from 23 to 150 &#176;C at 2.1 &#778;C/min; &#160;150 to 370 &#778;C &#160;at 3.7 &#778;C/min; &#160;370 to 480 &#778;C &#160;at 1.85 &#778;C/min; &#160;480 to 730 &#778;C at 4.17 &#778;C /min; 730 &#778;C for 1 hr; cooling 730 to 480 &#778;C &#160;at -4.17 &#778;C /min. 
		Note: The time for burn-out varies with size of a flask. In this study, set the burn-out time to 6 hr.</li>
		<li>Place the plaster mold in a furnace (Figure 2F).</li>
		<li>Turn on the furnace and increase temperature in the furnace to remove the sacrificial pattern inside the plaster mold. Follow the temperature condition in Figure 4. 
		Note: Because the UV curable/castable acrylic plastic, the materials of the sacrificial pattern, is a thermosetting acrylic-polymer plastic, it does not flow but is dissociated to a gas phase in the furnace.</li>
	</ol>
	</li>
	<li>Centrifugal Casting (Figure 2G)
	<ol>
		<li>Check that the centrifugal casting machine&#39;s arm spins with an angular velocity of 425 rpm using a tachometer after turning on the power of a centrifugal casting machine.</li>
		<li>Prepare two ceramic crucibles that can hold a 150 g alloy to melt. Use separate crucibles for Al and Cu alloys to keep them from being contaminated with each other.</li>
		<li>Turn on the power of the centrifugal casting machine.</li>
		<li>Using a metal cutter, chop the alloys into pieces with 10 - 20 mm in length. Prepare them enough to fully fill the mold cavity whose volume should be the same as the sacrificial pattern. 
		Note: The mass of metals necessary to fill out the same volume of the mold cavity varies considering varying density for each metal.</li>
		<li>Wear flame retardant cloths and gloves, and goggles. Prepare a bucket of water (30&#160;L) at RT.</li>
		<li>Take the plaster mold temporarily out from the furnace in Section 3.3, install it in the flask cradle and balance the arm of the centrifugal casting machine (Figure 5).</li>
		<li>Place the plaster mold back to the furnace and pre-heat up to 482 &#176;C&#160;before casting.</li>
		<li>Place the crucible in the crucible holder (Figure 5).</li>
		<li>Put the chopped alloy into the crucible.</li>
		<li>Open the valve of an oxygen tank connected with an oxygen-acetylene torch and maintain a pressure level in the tank of 96.5 kPa (14 psi).</li>
		<li>Ignite the oxygen-acetylene torch with a lighter and control the intensity of the flame by adjusting the mix of gases. 
		Note: Caution is needed when using the oxygen-acetylene torch. Its maximum temperature of the torch is around 1,200 &#176;C.</li>
		<li>Melt chopped alloy (Al alloy or Cu alloy) with the torch in the crucible until the alloy completely becomes liquid.</li>
		<li>Stir the alloy in the crucible with a carbon rod until the chopped alloy is completely melted.</li>
		<li>Place the plaster mold in the flask cradle back next to the crucible containing molten alloy (Figure 5).</li>
		<li>Close the cover of the centrifugal casting machine, let the centrifugal arm rotate and wait at least for 3 min. 
		Note: The centrifugal casting machine starts operating as soon as the cover of the casting machine is closed. The centrifugal arm rotates at a speed of 425 rpm which corresponds to the inlet velocity at the mold cavity of the sacrificial pattern, vr = 8.03 m/sec28, 29 in Figure 5 where the inlet-velocity is calculated using the macroscopic particle dynamics from an angular velocity of the centrifugal casting arm28, 29.</li>
		<li>Turn off the power of the centrifugal casting machine after the 3 min rotation of the arm.</li>
		<li>Open the cover of the casting machine.</li>
		<li>Take the plaster mold out of the flask cradle using tongs.</li>
		<li>Keep the mold at RT for 15 - 20 min until the color of molten alloy turns to its original one in the solid phase.</li>
		<li>Using tongs, quench the plaster mold in water placed in a bucket (30 L) at RT for about 5 min. Make sure that the temperature of the plaster mold is close to RT after quenching.</li>
		<li>In order to obtain the lattice metal inside the mold, dissolve the mold in water. The mold made of gypsum dissolves easily in water.</li>
	</ol>
	</li>
</ol>
4. Post Processing for Final Products of Octet Truss Metals
<ol>
	<li>Turn on the power of a sandblaster.</li>
	<li>Place the octet truss metals on the platform inside the sandblaster and close the door of the machine.</li>
	<li>Put on gloves and grab the sandblaster pistol.</li>
	<li>Grab the sprue part of the metal product and blow out the residual plaster from the lattice metal with the sandblaster for 2 hr. 
	Note: The intensity of the sandblaster is automatically fixed approximately at 550 kPa. Once the sandblaster is operated, then the air comes out automatically from the pistol.</li>
	<li>Keep the sandblaster running until the investment plaster residue inside the octet truss metal is completely removed while checking with the naked eye. 
	Note: There is not a microscopic criterion on removal of plaster residue. This is beyond the scope of this study. The removal of the plaster residue is easily determined with the naked eye. Because the octet truss is an open cell structure, it is possible to see through and check if whether or not the plaster residue is completely removed. 
	Note: Caution is needed for the sandblaster to not damage the octet truss metal with a thin wall thickness (0.5 mm) at the high pressure (550 kPa).</li>
	<li>If the investment plaster residue inside the octet truss metal is not fully removed with the sandblaster, use additional post processing methods; e.g., an ultrasonic cleaning or leaving the product in water for a day.</li>
	<li>In case of using an ultrasonic cleaner, fill 0.7 L water into the ultrasonic cleaner and place the octet truss metal with plaster residue in the ultrasonic cleaner.
	<ol>
		<li>Turn on the power of the ultrasonic cleaner.</li>
		<li>Set an operation condition; e.g., 3 hr at 70 &#176;C.</li>
		<li>Take the octet truss metal out of the ultrasonic cleaner once the operation ends.</li>
		<li>Dry the octet truss metal at RT until water on the metal surface is completely removed.</li>
	</ol>
	</li>
	<li>As an alternative post processing method, leave the octet truss metal in water. This causes the plaster residue to be dissolved in water.
	<ol>
		<li>Place the octet truss metal with the plaster residue in water and leave it for one day so that the bonding force between the investment plaster and the metal surface becomes weaken in water.</li>
		<li>Take the octet truss metal out of water.</li>
		<li>Dry the octet truss metal at RT until water on the metal surface is completely removed.</li>
	</ol>
	</li>
	<li>Using a saw or other proper tools, cut the metal filled the cavity of the sprue system part out of the metal product and obtain the final octet truss metal with a size of 25 mm x 25 mm x 25 mm, as shown in Figure 1B.&#160;</li>
</ol>

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The authors have nothing to disclose.

For conventional metal casting, it is important to keep the molten metal&#39;s flow smooth and streamlined in &#39;laminar&#39; in the mold cavity and rather avoid irregular and agitated flow generally observed in turbulent flow27. Accordingly, it is important to properly design the inlet of the sprue system associated with the rotating speed of a centrifugal arm to maintain the flow of molten metal inside the lattice mold cavity &#39;laminar&#39;.
In this study, the critical steps of the protocol are the mixing of investment powder with water, the burn-out of sacrificial pattern, and the centrifugal casting process. The mixing process of investment powder with water is important because quality of the plaster mold is mainly controlled by this process, subsequently influencing the degree of completion of the final products of octet truss metals. For instance, if the investment-water mixture is too coarse, the surface roughness becomes high, resulting in poor surface finish of final products. The burn-out process of the sacrificial pattern is also essential to determine the quality of final products because residue of the sacrificial pattern causes a casting defect such as misrun or metal penetration if the sacrificial pattern is not completely burned out. The last key step is the centrifugal casting process. Proper setup for casting is required to fully fill liquid metal out in the investment mold cavity with a complex network shaped octet truss structure.
As can be seen in Figure 6, under the same processing conditions, e.g., the inlet velocity, the inlet temperature of molten metal, pre-heat temperature of mold, Cu alloy shows a premature solidification in a lattice mold cavity with a wall thickness of 0.5 mm (Figure 6 (b)). This is thought be caused by the high surface tension (1,500 N/mm) and high viscosity (0.00038 Pa&#183;s) of Cu alloy through the micro-channel in the lattice mold cavity. On the other hand, it appears that a relatively low surface tension coefficient (900 N/mm) and viscosity (0.00087 Pa&#183;s) of the molten Al alloy enables it to fully fill the octet truss lattice mold cavity. It is recommended to find an optimum inlet velocity of molten metal for casting 3D network lattice structures with a thin wall thickness in order to overcome the sudden change in flow-direction of molten metal and the effect of surface tension in the micro-channel of the lattice structural mold cavity.
The surface tension effect of molten metal is known to be dominant at a thin channel where this lattice cavity mold geometry in this study can be applied. It may be possible to manufacture a lattice Cu alloy with a thicker wall thickness and higher injection velocity of centrifugal casting as demonstrated in our previous work 28-29.
Direct AM methods such as SLM and EBM have been considered for possible manufacturing methods for lightweight 3D lattice metals. However, direct AM methods appear to be limited in selecting materials. For example, current EBM technology is limited to Ti-6Al-4V and Inconel31. In spite of its extensive use in aerospace and bio-implant applications, aluminum, for example, is not being produced using this technology. Theoretically, it could be possible to extend the direct AM to other powder metals through close control of process parameters. However, practically, the direct AM has been reported to have difficulty in fabricating parts with metal powders with high optical reflectance and high thermal conductivity, e.g., Al. Moreover, evaporation and possible explosion inside the build chamber have been issued for aluminum powder31.
The proposed indirect AM technique is significant because this enables to manufacture lattice structures with metals where direct AM methods experience difficulty, resulting in empowering overall manufacturing capability of 3D lattice metals with both direct and indirect AMs by expanding the range of selection of metals. In addition, centrifugal casting, a step in this study, is known to provide an isotropic property of metal parts due to relatively equal spread of molten metal into the mold cavity. This may resolve the current issue of direct AM on anisotropy caused by both layered manufacturing and anisotropic formation of grains20-21.
Exploring other metals for indirect AM together with studies on the effect of process parameters on lattice geometries will be left to our future work.

Cellular metals are the metals made up of an interconnected network of solid struts or plates and have complex micro-architectures with voids1. Examples include both i) randomly structured stochastic foams and ii) periodically ordered two-dimensional (2D) honeycombs and three-dimensional (3D) lattice truss structures. They have received attention due to their high specific stiffness and strength1-3and high specific resilience4-5, excellent energy absorption for impact loading6, acoustic insulation7, possible design of heat dissipaters and heat exchangers8. Especially, periodically ordered lattice structures have the potential to engineer the properties superior with a capability to control the internal porous network geometry.
Due to their complex internal porous network geometry, it is difficult to manufacture cellular metals using the conventional subtractive machining. As such, researchers have started looking for alternative methods to fabricate cellular metals: forming gas in liquid metal or mixing metal powder with blowing agents were explored for manufacturing stochastic metal forms9. Due to the lack of control over cell topology, it is hard to tailor mechanical properties. Alternatively, manufacturing methods for periodically ordered cellular metals were explored: stamping thin sheets of metal into a corrugated shape followed by joining them to create periodic structures10, bonding slotted metal sheets11, extrusion12, weaving and blazing metal filaments to fabricate textiles13. Even though these manufacturing methods offer repeatable patterns, the patterns are still limited in the planar direction. In an effort to generate 3D pattern repetition, researchers started using additive manufacturing (AM); e.g., Selective Laser Melting (SLM)14, Electron Beam Melting (EBM)15, and Direct-Metal Laser Sintering (DMLS)16. Despite their capability to fabricate 3D ordered complex lattice geometries, there still exist some limitations: difficulty using metals with high thermal conductivity and high optical reflectivity17, high thermal residual stress18, poor surface finish with the &#39;balling&#39; phenomenon during laser or electron melting 19, anisotropic properties20-21 of parts caused by a combined effect of the layered manufacturing, anisotropic formation of grains, powder size, power and scanning speed of laser or electron beam15, high energy consumption, etc.
Combining polymer based AM with metal casting may provide an alternative method to manufacture lattice metals. One may call this &#34;indirect AM&#34;. Indirect AM may provide a solution to overcome the technical problems of direct AM of metals mentioned above. Several efforts have been made to manufacture lattice metals using indirect AM combining 3D printing of polymers with gravity based casting22-25; e.g., an investment casting combined with fused deposition modeling (FDM) to fabricate a lattice alloy22-25 or sand casting combined with a sand powder based AM23. The gravity based casting appears to remain a technical challenge to overcome - misrun and porosity caused by sudden solidification of molten metals when they meet network structures with sharp corners of lattice structural molds25-26. Relatively large surface area of lattice structural molds also appears to contribute to sudden cooling, resulting in premature solidification25-26.
In this study, we propose an alternative indirect AM that may overcome the misrun during manufacturing of lattice metals - centrifugal casting to a lattice mold cavity made by a 3D printed lattice sacrificial polymer pattern. We use a digital light processing (DLP) based 3D printing method to build a lattice structural sacrificial pattern followed by centrifugal casting of Al and Cu alloys. The objective of this study is to provide a detailed protocol on fabrication of 3D lattice metals having a complex shape and a thin wall thickness. The main contribution of this process is to provide an opportunity to extend the selection of materials with low manufacturing cost for manufacturing lattice metals.

<table><tbody><tr><td>Motorized centrifugal casting machine</td><td>Rey Motorized Centrifugal Casting Machine, Rey Industries Inc.</td><td></td><td>Made in U.S.A. by Rey industries, Inc. Dallas, TX 75220</td></tr><tr><td>Gypsum powder</td><td>Satin Cast 20, FindingKing Kerr</td><td>7960</td><td>Gypsum powder is used to make the investment mixture</td></tr><tr><td>Ployjet 3D printer</td><td>Projet HD3500 Plus, 3D Systems</td><td></td><td>This polymer based 3D printer to print out sacrificial pattern for casting.</td></tr><tr><td>Cartridge materials - UV curable and castable acrylic plastic</td><td>VisiJet Procast, 3D Systems</td><td></td><td>This is castable material that is going to be burn out before casting</td></tr><tr><td>Cartridge materials- support material</td><td>VijiJet S300, 3D Systems</td><td></td><td>This is support material that is going to be removed before pattern assemble</td></tr><tr><td>Ancient Bronze Casting Grain</td><td>Rio Grande</td><td>706051</td><td>This true bronze grain contains no zinc. Highly fluid, it melts quickly, casts cleanly and provides a good balance between strength and durability. The warm, deep-bronze color has rich red undertones, and the alloy takes a good patina.&lt;br/&gt; Composition is 90% copper with an amount of tin; fits into the CDA#90700 category. This grain is sold in 1 lb. packages.</td></tr><tr><td>Aluminum Round Wire, 1/8&quot;, 1-Lb. Spool, Dead Soft</td><td>Rio Grande</td><td>134700</td><td>Lightweight and strong, aluminum wire is an economical and versatile choice. Not as bright-white as silver, aluminum offers a warmer tone much like that of platinum. Solder ONLY with low-temp solders such as Stay-Brite; suitable for both pulse-arc and laser welding. This quality aluminum wire is packaged on 1 lb. spools.</td></tr><tr><td>Computer aided design software (Pro-e)</td><td></td><td></td><td>This software can be replaced with the others such as Auto CAD, Catia, and so on.</td></tr><tr><td>ProJet Finisher 1-A</td><td>3D Systems</td><td></td><td>This machine is used to melt the support material.</td></tr><tr><td>160 Watt 2.5 Liters Digital Ultrasonic Cleaner with Timer Heater Rings Tools</td><td>Chicago, Electric, Power Tools</td><td></td><td>85 oz. capacity, Five cleaning cycles: 90, 180, 280, 380 and 480 seconds, Clean with or without heat, Easy-to-read LED digital timer, Clear-view window</td></tr><tr><td>Fan&amp;nbsp;</td><td>Honeywell Inc.&amp;nbsp;</td><td>HT-800</td><td>120 V A.C., 60 Hz., 0.85 A. TP</td></tr><tr><td>Paraffin wax for wax sheet - Modeler&#039;s Pink Wax Sheet, 3&quot; by 6&quot;, 24-Ga.</td><td>Rio Grande</td><td>700075</td><td>Sheet wax is flexible and can be cut or formed into any shape. It&amp;rsquo;s ideal for designing since you can draw or trace directly onto the sheet; choose green or pink depending on which will best show your designs. High manufacturing standards ensure exceptional consistency and significant price savings. Value is enhanced by larger package quantities at the same price as the smaller packages available elsewhere. Each 8-oz. package contains approximately 30 sheets.</td></tr><tr><td>Paraffin wax for wax stick - Modeler&#039;s Medium Red Sprue Wax, 8-Ga</td><td>Rio Grande</td><td>700741</td><td>A pliable, softer sprue wax than the firm blue. Good for forming gates and sprues and burns out cleanly with no residue.</td></tr><tr><td>Alcohol Lamp</td><td>Rio Grande</td><td>700008</td><td>Use this lamp to heat wax-working tools or as a flame polisher. The heavy glass reservoir has faceted sides to allow it to be tipped for angling the flame. A screw adjustment for the 7&quot; x 3/16&quot; wick controls the height of the flame. A safety cap snuffs the flame and prevents fuel evaporation. For the best flame, use methyl alcohol fuel. Replacement wicks available. Reservoir holds 5 oz. (150 ml) of fuel.</td></tr><tr><td>Wax carving tool set - Soft Grip Wax Carvers, Set of 10</td><td>Rio Grande</td><td>700329</td><td>This boxed set offers the best in cutting and shaping technology. Each of these ten high-quality steel wax-carving tools features a 5/16&quot; PVC covered handle that ensures a sure, comfortable grip through hours of work and all have sharp edges for shaping and fine detailing. Sharpen or custom-shape each tool to fit your needs. These tools provide exceptional tool strength and deliver excellent results. This set comes in a hinged, foam-lined wood box.</td></tr><tr><td>Rubber Mixing Bowl, 1 - 1/2 Qt.</td><td>Rio Grande</td><td>702131</td><td>This highly-flexible vulcanized rubber bowl is easy to grip, will not be marred by a spatula and cleans with ease.</td></tr><tr><td>Pyrex Beaker, 1,000ml</td><td>Rio Grande</td><td>335040</td><td>Ideal for holding and heating bath plating solutions, this genuine Pyrex glass beaker is sturdy and durable.</td></tr><tr><td>Rio Premium Stainless Steel Flask, 2 - 1/2&quot; dia.</td><td>Rio Grande</td><td>70201514</td><td>This solid, #304-quality stainless steel flask is corrosion-resistant, durable for a long service life and performs under extreme temperature without distortion.</td></tr><tr><td>CAST/T Ceramic Casting Crucible, 450 g</td><td>Rio Grande</td><td>705047</td><td>Made exclusively for the CAST/T centrifugal casting machine, this crucible is designed with an angled base that slides into the hinged bracket on top of the casting machine. This brings the crucible into perfect alignment with the center of the flask ring to ensure an error-free pour.</td></tr><tr><td>MyWeigh iBalance 300 Digital Scale</td><td>Rio Grande</td><td>116850</td><td>This scale is used to measure the weight of the sacrificial and sprue system for metal which is going to be used for centrifugal casting.</td></tr><tr><td>Rubber bottom - CAST/T Flask Ring Base</td><td>Rio Grande</td><td>705025</td><td>Specially made for the CAST/T centrifugal casting machine, this rubber base accommodates all Table King flask ring styles, creating a secure, airtight seal throughout the investment process. The center post fits either of the wax disc styles for complete versatility.</td></tr><tr><td>Scotch&amp;reg; Colored Duct Tape, 1 7/8&quot; x 20 Yd., Blue</td><td>OfficeMax&amp;nbsp;</td><td>22353766</td><td>This scotch tape is used to make sure that the gypsum-water mixture fully covers the assembled sacrificial pattern inside the flask by allowing for extra material above the flask height</td></tr><tr><td>Vacuum casting machine - V.I.C. 12 Tabletop Solid- and Perforated-Flask Casting Machine with The Rio Assistant, 110-Volt</td><td>Rio Grande</td><td>70511814</td><td>The V.I.C. 12 casting machine offers all the latest technical innovations for efficient, productive vacuum investing and casting. Designed to meet the demands of medium-sized casting operations, this machine includes a powerful 1/2 hp, 5cfm vacuum pump for effective vacuuming and outstanding casting results. The V.I.C. 12 casts small or large flasks. Includes an adapter table that accepts standard solid flasks up to 5&quot; x 7&quot; high and is mounted on rubber feet for stability.</td></tr><tr><td>Furnace for burn out sacrificial pattern -Rio Model 1000 Enameling Kiln with Nine Program Controller</td><td>Rio Grande</td><td>703121</td><td>The Rio enameling kiln features three pre-set firing temperatures for enamels and six that you can define. Use the exclusive Rio controller to set and maintain firing temperatures. Perfect for all types of enameling, including tall pieces. Includes ample space for firing and an easy-latch door that will not jar your enamels when opening and closing. Also suitable for metal clay, glass and ceramics. Galvanized steel case with high-temperature insulating firebrick keeps them cool. Element protected in recessed groove. Includes user instructions.</td></tr><tr><td>Smith Complete Little Torch Acetylene and Oxygen System</td><td>Rio Grande</td><td>500030</td><td>Get everything you need to equip your shop for soldering and brazing. Use Little Torch systems for gold&lt;br/&gt; or silver soldering, brazing and casting applications. Complete every soldering and melting job with confidence and ease! This system accepts all Little Torch accessory tips for melting, brazing and large soldering jobs and is a staple for every jeweler.</td></tr><tr><td>Heat-Resistant Safety Apron</td><td>Rio Grande</td><td>750160</td><td>The specially designed apron has an 800 &amp;deg;F (427 &amp;deg;C) temperature resistance. Its reflective finish repels hot metal splashes and helps insulate the wearer from heat.</td></tr><tr><td>Radnor Heat-Resistant Gloves</td><td>Rio Grande</td><td>350050</td><td>These flexible, heat-resistant gloves are ideal for enameling projects, allowing you to grip even small tongs securely. Blue, shoulder-split leather gloves are made of tough cowhide and lined with cotton and foam, and have reinforced thumb wings.</td></tr><tr><td>Platinum Soldering Glasses, #7</td><td>Rio Grande</td><td>113914</td><td>Protect yourself and your employees when soldering platinum. Comfortable glasses feature adjustable earpieces and 52mm IR green polycarbonate #7 lenses. The #7 lens is approved by The Platinum Guild.</td></tr><tr><td>Economy Light-Duty Flask Tongs</td><td>Rio Grande</td><td>704026</td><td>Constructed of bent steel, these tongs are designed to handle flasks 3-1/2&quot; or less in diameter. The small-angle notches grip smaller flask sizes and the larger, rounded contour area securely holds larger flasks.</td></tr><tr><td>Separating Screen Bucket</td><td>Rio Grande</td><td>201360</td><td>15&quot;-diameter, 11-1/2&quot;-deep</td></tr><tr><td>Sand blaster - Econoline - 101701CB-A - Free-Standing Cabinets Workspace Width (Inch): 60 Workspace Depth (Inch): 48</td><td>MSC industrial supply Co.&amp;nbsp;</td><td>223818</td><td>Ree-Standing Cabinets; Workspace Width (Inch): 60; Workspace Depth (Inch): 48; Workspace Height (Inch): 40; Air Requirement: 12 CFM @ 80 psi; Overall Cabinet Width (Inch): 65; Maximum Cabinet Depth (Inch): 86</td></tr><tr><td>Johnson&#039;s Baby Oil Shea &amp;amp; Cocoa Butter&amp;nbsp;</td><td>Wal-Mart</td><td>260074132</td><td>This baby&amp;nbsp; oil is used for removing the residue of the support material for the castable sacrificial pattern using Digital Ultrasonic Cleaner.</td></tr><tr><td>German 4&quot; Saw Frame and Saw Blade Kit</td><td>Rio Grande</td><td>110112</td><td>Quality, German-made frames are our most popular saw frames, and this frame includes a sampler pack of Rio German saw blades! The adjustable saw frame allows you to achieve the blade tension you want. Throat depth is 102mm (4&quot;). Saw blades have rounded backs that make cutting curves and corners easy and are made from hardened, tempered steel.</td></tr></tbody></table>

indirect fabrication of lattice metals with thin sections using centrifugal casting

One of the typical methods to manufacture 3D lattice metals is the direct-metal additive manufacturing (AM) process such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In spite of its potential processing capability, the direct AM method has several disadvantages such as high cost, poor surface finish of final products, limitation in material selection, high thermal stress, and anisotropic properties of parts. We propose a cost-effective method to manufacture 3D lattice metals. The objective of this study is to provide a detailed protocol on fabrication of 3D lattice metals having a complex shape and a thin wall thickness; e.g., octet truss made of Al and Cu alloys having a unit cell length of 5 mm and a cell wall thickness of 0.5 mm. An overall experimental procedure is divided into eight sections: (a) 3D printing of sacrificial patterns (b) melt-out of support materials (c) removal of residue of support materials (d) pattern assembly (e) investment (f) burn-out of sacrificial patterns (g) centrifugal casting (h) post-processing for final products. The suggested indirect AM technique provides the potential to manufacture ultra-lightweight lattice metals; e.g., lattice structures with Al alloys. It appears that the process parameters should be properly controlled depending on materials and lattice geometry, observing the final products of octet truss metals by the indirect AM technique.

Using the indirect additive manufacturing described in the protocol section, Al and Cu alloys were used for manufacturing octet truss metals, as shown in Figure 1. The whole casting procedure is summarized in Figure 2. The procedure consists of eight sections: (a) sacrificial pattern printing (b) melting-out of support material (c) removal of residue of support material (d) pattern assembly (e) investment (f) burn-out of sacrificial patterns (g) centrifugal casting, and (h) post-processing. The investment mixing process was performed in order to make sure that there were no lumps in the investment-water mixture, as shown in Figure 3. The burn-out process was carried out for 6 hr to melt out the sacrificial pattern as shown in Figure 4, followed by the centrifugal casting process (Figure 2G and Figure 5). Figure 6 shows the final products of octet truss metals with Al and Cu alloys. It shows that the molten Al alloy fully fills the entire lattice mold cavity without misrun. On the other hand, the molten Cu alloy appears to have a casting defect with premature solidification at the early stage of injection of molten metal at the inlet.
<img alt="Figure 1" src="/files/ftp_upload/53605/53605fig1.jpg" /> 
Figure 1. A Schematic of Octet Truss Structure with a Sprue System. Figure 1 shows a schematic of a sacrificial pattern of octet truss structure with a sprue system used in this study. The sprue system consists of a sheet of a 1 mm thickness, a 25 mm width, and a pillar having 10 mm in height and 6 mm in diameter. The sprue system can be modified using CAD software, if needed, for design of better fluidity of liquid metal. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53605/53605fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/53605/53605fig2.jpg" /> 
Figure 2. An Overview of the Indirect AM with Centrifugal Casting Procedure: (A) pattern printing (B) melt-out of support material (C) removal of residue of support material (D) pattern assembly (E) investment (F) burn-out of sacrificial pattern (G) centrifugal casting, and (H) post processing. This figure shows the whole procedure on fabricating octet truss metals using indirect AM with centrifugal casting. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53605/53605fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/53605/53605fig3.jpg" /> 
Figure 3. Work Schedule on Preparation of the Plaster Mold. Figure 3 shows the preparation of the plaster mold and the procedure to harden it in the flask. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53605/53605fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/53605/53605fig4.jpg" /> 
Figure 4. Burn-out Schedule of Sacrificial Pattern Inside the Plaster Mold. Figure 4 shows the burn-out process of the sacrificial pattern inside the hardened mixture. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53605/53605fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" src="/files/ftp_upload/53605/53605fig5.jpg" /> 
Figure 5. A Schematic of a Centrifugal Casting Machine. The centrifugal casting machine consists of eight components: main shaft, base, casting arm, weights, flask cradles, flask cradles holding arms, crucible holder, and crucible holding arms. The casing arm is balanced with moving weights along the casting arm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53605/53605fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" src="/files/ftp_upload/53605/53605fig6.jpg" /> 
Figure 6. Final Product of Octet Truss Metals: Octet truss structures with (A) Al and (B) Cu alloys. It shows a fairly good degree of completion on the octet truss Al alloy. On the other hand, a poor degree of completion is observed with the octet truss Cu alloy. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53605/53605fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Property</td>
			<td>Value [unit]</td>
		</tr>
		<tr>
			<td>Density at 20&#160;&#176;C</td>
			<td>1,019 [kg/m^3]&#160;</td>
		</tr>
		<tr>
			<td>Thermal conductivity at 20&#160;&#176;C</td>
			<td>&#160;0.47 [W/(m*K)]</td>
		</tr>
		<tr>
			<td>Thermal expansion coefficient at 20&#160;&#176;C</td>
			<td>7.22E-6 [/&#176;C]</td>
		</tr>
		<tr>
			<td>Roughness</td>
			<td>2.72E-6 [m]</td>
		</tr>
	</tbody>
</table>
Table 1. Properties of the Investment Powder. This table shows the physical properties of the investment powder used in this study.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td colspan="8">40 ml water to 100 g powder</td>
		</tr>
		<tr>
			<td rowspan="2">Flask diameter</td>
			<td colspan="7">Height</td>
		</tr>
		<tr>
			<td>5.08 cm</td>
			<td>6.35 cm</td>
			<td>7.62 cm</td>
			<td>8.89 cm</td>
			<td>10.16 cm</td>
			<td>12.7 cm</td>
			<td>15.24 cm</td>
		</tr>
		<tr>
			<td>6.35 cm</td>
			<td>226.8 g 91 ml</td>
			<td>283.5 g 114 ml</td>
			<td>340.19 g 136 ml</td>
			<td>396.89 g 160 ml</td>
			<td>453.59 g 183 ml</td>
			<td>566.99 g 228 ml</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="8">(Top figure - Investment powder (g), Bottom figure - Water (ml))</td>
		</tr>
		<tr>
			<td colspan="8">Note: In this study, a flask with a height of 6.35 cm&#160; and a diameter of 6.35 cm is used.</td>
		</tr>
	</tbody>
</table>
Table 2. Mixing Conditions of Investment Powder with Water for a Varying Flask Size: This table shows the mixing conditions of the investment powder and water for a varying flask size recommended by manufacturer. In this study, a flask with a height of 6.35 cm and a diameter of 6.35 cm is used.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td colspan="4">(a) Chemical composition of Al alloy</td>
		</tr>
		<tr>
			<td>Material&#160;</td>
			<td colspan="3">Unit</td>
		</tr>
		<tr>
			<td rowspan="3">Aluminum alloy</td>
			<td colspan="3">Chemical composition</td>
		</tr>
		<tr>
			<td></td>
			<td>Al</td>
			<td>Cr</td>
		</tr>
		<tr>
			<td>Min./Max.</td>
			<td>&#62;99</td>
			<td>&#60;0.05</td>
		</tr>
		<tr>
			<td colspan="4">&#160;(b) Physical properties of Al alloy</td>
		</tr>
		<tr>
			<td colspan="2">Property</td>
			<td colspan="2">Unit</td>
		</tr>
		<tr>
			<td colspan="2">Liquidus temperature</td>
			<td colspan="2">660&#160;&#176;C&#160;</td>
		</tr>
		<tr>
			<td colspan="2">Solidus temperature</td>
			<td colspan="2">660&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="2">Density</td>
			<td colspan="2">2,340[kg/m^3] @850&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="2">Specific heat</td>
			<td colspan="2">1,090 J/kg&#8729;&#176;C</td>
		</tr>
		<tr>
			<td colspan="2">Thermal conductivity</td>
			<td colspan="2">0.9428 [W/(cm*&#176;C)] @850&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="2">Viscosity</td>
			<td colspan="2">0.00087 [Pa&#8729;s] @850&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="2">Surface tension coefficient</td>
			<td colspan="2">900 [N/mm]</td>
		</tr>
	</tbody>
</table>
Table 3. Chemical Composition and Physical Properties of Al Alloy30: (a) Chemical composition of Al alloy and (b) Physical properties of Al alloy.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td colspan="7">(a) Chemical composition of Cu alloy</td>
		</tr>
		<tr>
			<td>Material</td>
			<td colspan="6">Unit</td>
		</tr>
		<tr>
			<td rowspan="3">Copper alloy (Jewelry bronze)</td>
			<td colspan="6">Chemical Composition (%Max, unless shown as range of mean)</td>
		</tr>
		<tr>
			<td></td>
			<td>Cu</td>
			<td>Si</td>
			<td>Zn</td>
			<td>Mg</td>
			<td>Pb</td>
		</tr>
		<tr>
			<td>Min./Max.</td>
			<td>91.9</td>
			<td>4</td>
			<td>4</td>
			<td>0.25 Max</td>
			<td>0.25 Max</td>
		</tr>
		<tr>
			<td colspan="6">(b) Physical properties of Cu alloy</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="3">Property</td>
			<td colspan="4">Unit</td>
		</tr>
		<tr>
			<td colspan="3">Liquidus temperature</td>
			<td colspan="4">1,035 &#176;C</td>
		</tr>
		<tr>
			<td colspan="3">Solidus temperature</td>
			<td colspan="4">1,005 &#176;C</td>
		</tr>
		<tr>
			<td colspan="3">Density</td>
			<td colspan="4">7,200 [kg/m^3] @1200&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="3">Specific heat</td>
			<td colspan="4">380 J/kg&#8729;&#176;C</td>
		</tr>
		<tr>
			<td colspan="3">Thermal conductivity</td>
			<td colspan="4">1.44 [W/(cm*&#8451;)] @1200&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="3">Viscosity</td>
			<td colspan="4">0.0038[Pa&#8729;s] @1200&#160;&#176;C</td>
		</tr>
		<tr>
			<td colspan="3">Surface tension coefficient</td>
			<td colspan="4">1,500 [N/mm]</td>
		</tr>
	</tbody>
</table>
Table 4. Chemical Composition and Physical Properties of Cu Alloy30: (a) Chemical composition of Cu alloy and (b) Physical properties of Cu alloy.

Watch this Scientific Journal Video about Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting at JoVE.com

Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting

An indirect additive manufacturing method combining a 3D printing of polymers with a centrifugal casting is outlined for manufacturing 3D octet truss metals (Al and Cu alloys) having a unit cell length of 5 mm with a wall thickness of 0.5 mm.

One of the typical methods to manufacture 3D lattice metals is the direct-metal additive manufacturing (AM) process such as Selective Laser Melting (SLM) ...

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12.4K 조회수.  University of North Texas. An indirect additive manufacturing method combining a 3D printing of polymers with a centrifugal casting is outlined for manufacturing 3D octet truss metals (Al and Cu alloys) having a unit cell length of 5 mm with a wall thickness of 0.5 mm.

비디오: Indirect Fabrication of Lattice Metals with Thin Sections Using Centrifugal Casting

A Method to Fabricate Disconnected Silver Nanostructures in 3D

The standard nanofabrication toolkit includes techniques primarily aimed at creating 2D patterns in dielectric media. Creating metal patterns on a submicron scale requires a combination of nanofabrication tools and several material processing steps. For example, steps to create planar metal structures using ultraviolet photolithography and electron-beam lithography can include sample exposure, sample development, metal deposition, and metal liftoff. To create 3D metal structures, the sequence is repeated multiple times. The complexity and difficulty of stacking and aligning multiple layers limits practical implementations of 3D metal structuring using standard nanofabrication tools. Femtosecond-laser direct-writing has emerged as a pre-eminent technique for 3D nanofabrication.1,2 Femtosecond lasers are frequently used to create 3D patterns in polymers and glasses.3-7 However, 3D metal direct-writing remains a challenge. Here, we describe a method to fabricate silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm. The method enables the fabrication of patterns not feasible using other techniques, such as 3D arrays of disconnected silver voxels.8 Disconnected 3D metal patterns are useful for metamaterials where unit cells are not in contact with each other,9 such as coupled metal dot10,11or coupled metal rod12,13 resonators. Potential applications include negative index metamaterials, invisibility cloaks, and perfect lenses.
In femtosecond-laser direct-writing, the laser wavelength is chosen such that photons are not linearly absorbed in the target medium. When the laser pulse duration is compressed to the femtosecond time scale and the radiation is tightly focused inside the target, the extremely high intensity induces nonlinear absorption. Multiple photons are absorbed simultaneously to cause electronic transitions that lead to material modification within the focused region. Using this approach, one can form structures in the bulk of a material rather than on its surface.
Most work on 3D direct metal writing has focused on creating self-supported metal structures.14-16 The method described here yields sub-micrometer silver structures that do not need to be self-supported because they are embedded inside a matrix. A doped polymer matrix is prepared using a mixture of silver nitrate (AgNO3), polyvinylpyrrolidone (PVP) and water (H2O). Samples are then patterned by irradiation with an 11-MHz femtosecond laser producing 50-fs pulses. During irradiation, photoreduction of silver ions is induced through nonlinear absorption, creating an aggregate of silver nanoparticles in the focal region. Using this approach we create silver patterns embedded in a doped PVP matrix. Adding 3D translation of the sample extends the patterning to three dimensions.

Femtosecond-laser direct-writing is frequently used to create three-dimensional (3D) patterns in polymers and glasses. However, patterning metals in 3D remains a challenge. We describe a method for fabricating silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm.

3D로 연결이 끊긴 실버 Nanostructures를 조작하는 방법

The standard nanofabrication toolkit includes  techniques primarily aimed at creating 2D patterns in dielectric media. Creating  metal patterns on a ...

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Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

The Vaporization of a Sacrificial Component (VaSC) process is used to fabricate microvascular structures. This procedure uses sacrificial poly(lactic) acid fibers to form hollow microchannels with precise 3D geometric positioning provided by laser micromachined guide plates.

희생 구성 요소의 증발을 사용하여 세 가지 차원 미세 만들기의 과정

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material ...

Fabrication of Spatially Confined Complex Oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

공간적으로 밀폐 복합 산화물의 제조

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

실리콘 다이렉트 웨이퍼 본딩을 통한 균일한 나노스케일 캐비티 제조

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Preparation of Liquid-exfoliated Transition Metal Dichalcogenide Nanosheets with Controlled Size and Thickness: A State of the Art Protocol

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. Layered crystals of molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are exfoliated in aqueous surfactant solution by sonication. This yields highly polydisperse mixtures containing nanosheets with broad size and thickness distributions. However, for most purposes, specific sizes (in terms of both lateral dimension and thickness) are required. For example, large and thin nanosheets are desired for (opto) electronic applications, while laterally small nanosheets are interesting for catalytic applications. Therefore, post-exfoliation size selection is an important step that we address here. We provide a detailed protocol on the efficient size selection in large quantities by liquid cascade centrifugation and the size and thickness quantification by statistical microscopic analysis (atomic force microscopy and transmission electron microscopy). The comparison of MoS2 and WS2 shows that both materials are size-selected in a similar way by the same procedure. Importantly, the dispersions of size-selected nanosheets show systematic changes in their optical extinction spectra with size due to edge and confinement effects. We show how these optical changes are related quantitatively to the nanosheets dimensions and describe how mean nanosheets length and layer number can be extracted reliably from the extinction spectra. The exfoliation and size selection protocol can be applied to a broad range of layered crystals as we have previously demonstrated for graphene, gallium sulphide (GaS) and black phosphorus.

A protocol for the liquid exfoliation of layered materials to nanosheets, their size selection and size measurement by microscopic and spectroscopic techniques is presented.

액체 박리 전이 금속 Dichalcogenide 제어 된 크기와 나노 시트와 두께의 준비 : 예술 프로토콜의 주

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

콜 로이드 리소 그래피를 사용 하 여 정기적 금 Nanocup 배열의 제작

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Processing of Bulk Nanocrystalline Metals at the US Army Research Laboratory

Given their potential for significant property improvements relative to their large grained counterparts, much work has been devoted to the continued development of nanocrystalline metals. Despite these efforts, the transition of these materials from the lab bench to actual applications has been blocked by the inability to produce large scale parts that retain the desired nanocrystalline microstructures. Following the development of a method proven to stabilize the nanosized grain structure to temperatures approaching that of the melting point for the given metal, the US Army Research Laboratory (ARL) has progressed to the next stage in the development of these materials - namely the production of large scale parts suitable for testing and evaluation in a range of relevant test environments. This report provides a broad overview of the ongoing efforts in the processing, characterization, and consolidation of these materials at ARL. In particular, focus is placed on the methodology used for producing the nanocrystalline metal powders, in both small and large-scale amounts, that are at the center of ongoing research efforts.

This paper provides a brief overview of the ongoing efforts at the Army Research Laboratory on the processing of bulk nanocrystalline metals with an emphasis on the methodologies used for the production of the novel metal powders.

미국 육군 연구소에서 대량 Nanocrystalline 금속 처리

Given their potential for significant property improvements relative to their large grained counterparts, much work has been devoted to the continued ...

Fused Filament Fabrication (FFF) of Metal-Ceramic Components

Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with diverse customization options and favorable production methods is increasing continuously. With fused filament fabrication (FFF), it is possible to produce large and complex components quickly with high material efficiency. In FFF, a continuous thermoplastic filament is melted in a heated nozzle and deposited below. The computer-controlled print head is moved in order to build up the desired shape layer by layer. Investigations regarding printing of metals or ceramics are increasing more and more in research and industry. This study focuses on additive manufacturing (AM) with a multi-material approach to combine a metal (stainless steel) with a technical ceramic (zirconia: ZrO2). Combining these materials offers a broad variety of applications due to their different electrical and mechanical properties. The paper shows the main issues in preparation of the material and feedstock, device development, and printing of these composites.

Fused Filament Fabrication FFF of Metal-Ceramic Components

This study shows multi-material additive manufacturing (AM) using fused filament fabrication (FFF) of stainless steel and zirconia.

금속-세라믹 부품의 융합된 필 라 멘 트 제조 (FFF)

Technical ceramics are widely used for industrial and research applications, as well as for consumer goods. Today, the demand for complex geometries with ...

Fabrication of Magnetic Nanostructures on Silicon Nitride Membranes for Magnetic Vortex Studies Using Transmission Microscopy Techniques

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared on transparent membranes which are very fragile and difficult to manipulate. We present processes for the fabrication of samples with magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for Lorentz transmission electron microscopy and magnetic transmission x-ray microscopy studies. The samples are prepared on silicon nitride membranes and the fabrication consists of a spin coating, UV and electron-beam lithography, the chemical development of the resist, and the evaporation of the magnetic material followed by a lift-off process forming the final magnetic structures. The samples for the Lorentz transmission electron microscopy consist of magnetic nanodiscs prepared in a single lithography step. The samples for the magnetic x-ray transmission microscopy are used for time-resolved magnetization dynamic experiments, and magnetic nanodiscs are placed on a waveguide which is used for the generation of repeatable magnetic field pulses by passing an electric current through the waveguide. The waveguide is created in an extra lithography step.

A protocol for the fabrication of magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for transmission electron microscopy (TEM) and magnetic transmission x-ray microscopy (MTXM) studies is presented.

자기 소용돌이 연구 전송 현미경 검사 법 기술을 사용 하 여 실리콘 질 화 막에 자석 Nanostructures의 제조

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared ...

Fabricating van der Waals Heterostructures with Precise Rotational Alignment

In this work we describe a technique for creating new crystals (van der Waals heterostructures) by stacking distinct ultrathin layered 2D materials. We demonstrate not only lateral control but, importantly, also control over the angular alignment of adjacent layers. The core of the technique is represented by a home-built transfer setup which allows the user to control the position of the individual crystals involved in the transfer. This is achieved with sub-micrometer (translational) and sub-degree (angular) precision. Prior to stacking them together, the isolated crystals are individually manipulated by custom-designed moving stages that are controlled by a programmed software interface. Moreover, since the entire transfer setup is computer controlled, the user can remotely create precise heterostructures without coming into direct contact with the transfer setup, labeling this technique as &#8220;hands-free&#8221;. In addition to presenting the transfer set-up, we also describe two techniques for preparing the crystals that are subsequently stacked.

In this work we describe a technique that is used to create new crystals (van der Waals heterostructures) by stacking ultrathin layered 2D materials with precise control over position and relative orientation.

In this work we describe a technique for creating new crystals (van der Waals heterostructures) by stacking distinct ultrathin layered 2D materials. We ...