Electron Microscopy
11 articles
Aperture Materials and Cleaning
Aperture Materials Whether an aperture can be cleaned and reused depends partially on the material. Platinum Apertures Platinum apertures are easily cleaned by either an aperture flamer or over a bunsen burner in the open air. The platinum aperture should be handled with a pair of tweezers reserved solely for this purpose. Platinum apertures can also be cleaned chemically, however neither method will reliably remove all contaminants. Even an aperture that appears clean may produce astigmatism when reused in the microscope. The platinum aperture therefore has a limited work life. Molybdenum Apertures Molybdenum apertures can be cleaned 5 to 10 times more than a platinum aperture, however they must be cleaned under high vacuum, using a vacuum evaporator. Gold Foil Disc Apertures Conventional mechanical cleaning involving costly down-time is no longer necessary with gold foil “self-cleaning” apertures. Advanced techniques of thin metal film application permits the apertures to retain a clean hole edge during prolonged beam exposure. Ultra-thin, half-micron design discourages contaminant accumulation and stabilises astigmatic conditions to provide longer life. Because the foil is ultra thin, care must be taken when handling the gold foil apertures. Cleaning Aperture Cleaning using Flamer The following method is for cleaning platinum apertures; clean tungsten and molybdenum apertures by heating in vacuum. Pre-clean apertures by storing them for a while in a strong solvent such as chloroform. Place aperture disc in cup or hang strip from hook on cup. Turn Bunsen burner to low (small blue flame). Hold apertures on flamer 12mm - 20mm above aperture. Adjust heat if required to turn aperture bright red. No more than 5 seconds. Greater heat and long (more than a few seconds) flaming times increase crystalinity of the disk or strip and eventually ruin the apertures. Inspect aperture on a microslide with a microscope. Repeat heating if required. Note: the force of the heat, rather than the flame itself, cleans the aperture. Cleaning MAP Apertures When mounting Pt or Mo apertures, please note: Very small and loose particles may contaminate new and well made apertures. Inspect aperture, after placing it flat side up on a clean watch glass. Use a light microscope with a 10x to 40x objective. If required, ultra-sonicate aperture in absolute alcohol and blot, flat side up on filter paper. Work with aperture container and electron microscope holder above lint free material, such as aluminium foil or a large filter paper. Use tweezers, exerting little pressure, and lift aperture straight into aperture holder.
Cleaning and Care for MiTeGen MicroTools
Cleaning The best and easiest way to clean MiTeGen’s tools is to soak them in a bath of a detergent-containing solution. When mounted in MiTeGen base holders, large quantities of mounts can be cleaned at one time. To remove protein residues, we recommend an enzyme-containing detergent such as Alconox’s Tergazyme or Decon’s Contrex EZ; otherwise, a standard laboratory glassware/plasticware cleaner like Alconox is adequate. We recommend an initial 10 to 15 minute soak, followed by a quick rinse in a bath of water to remove the detergent. The optimal length of the soak needed will be determined by what residual materials are left on the mount or tool (protein, etc.) and how long it has been since they were last used. The sooner you clean them after use the easier it will be. MiTeGen’s Base Holder makes cleaning easy Load your loop-containing bases into the holder. Then place the holder into a plastic or glass tub or dish. Mix your detergent-containing solution according to the instructions on the detergent box. Then pour the detergent into the tub until the level rises to the Fill Line on the base holder.This will ensure that the loop tips are soaked, while keeping the stainless steel part of the bases out of the solution and preventing corrosion. In the rare case when soaking doesn’t remove deposits, you can use a Medium (M) or Fine (F) paper wick. For easiest handling, cut back from the widest end using a razor blade so that the diameter fits into a 0.7 mm mechanical pencil. Then dip the other end in water, a detergent solution or in isopropanol, and gently stroke the polymer from base to tip. Handling Do's and Don'ts The microfabricated tips of MiTeGen’s MicroMounts™, MicroLoops™ and other tools are made from the most durable unoriented polymer available, for ultra-low background X-ray scatter. Compared with an oriented fibre like nylon, unoriented polymers can be more easily torn or cut if used improperly. Follow the instructions below to get the maximum life out of our products. Never touch the tips with your hands. Always use our heavy-duty tweezers along the pin shaft, not the tip. Never push the bevelled steel pin into the tip against a hard surface. DO : Clean the tips by soaking in detergent while held in a MiTeGen Base Holder. DO NOT : sonicate for extended times. Sonication for a few minute or so is ok, but sonication for long periods can damage some tips. Using an enzyme-containing detergent, sonication should be unnecessary. DO : Remove stubborn residues using a MiTeGen paper wick. DO NOT : use cotton or foam-tipped swabs. Swabs can catch and tear the polymer. To dry the tips after cleaning, let them air dry. You can briefly dip in isopropanol for faster drying. Avoid blow drying. If the nozzle is placed too close to the tip, the resulting turbulent drag force can damage the tip. Keep the nozzle at least 20 cm away from the tip.
Compound, Pure Metal, NBS, and BAS Standards
All compound, BAS standards, Austenitic Steels, and NBS standards are available as single standards or grains. Compound Standards Formulae Name Formulae Name AgCl Silver (I) Chloride LuF 3 Lutetium Fluoride Ag 2 S Silver Sulphide LuSi 2 Lutetium Silicide Ag 2 Te 3 Silver Telluride Mg, Al, Mn, Zn Magnesium Alloy Al,Cu,Mg Dural Mg 2 Sn Magnesium Tin Alloy Al,Mg,Si Aluminium Alloy MgAl 2 O 4 Spinel AlSb Aluminium Antimodide MgF 2 Magnesium Fluoride Al,Si Aluminium Alloy MgO Periclase Al 2 O 3 Aluminium Oxide MnF 2 Manganese Fluoride AlF 3 Aluminium Fluoride MnTiO 3 Manganese Titanate AlF 3 Aluminium Fluoride anhydrous MoO 3 Molybdenum (V1) Oxide AlN Aluminium Nitride MoS 2 Molybdenum (IV) Sulfide B 2 O 3 Boron Trioxide Na 3 AlF 6 Cryolite B 4 C Boron Carbide NaCl Sodium Chloride Ba Barium REE Glass NaF Sodium Fluoride BaF 2 Barium Fluoride Nb 2 O 5 Niobium Oxide BaTiO 3 Barium Titanate Nd 2 O 3 Neodymium Oxide Bi 2 Se 3 Bismuth Selenide Nd Neodymium 12mm pcs 99.9% Bi 2 Te 3 Bismuth Telluride NdF 3 Neodymium Fluoride BN Boron Nitride NiAs Nickel Arsenide CaMoO 4 Calcium Molybdate NiO Nickel Oxide CaWO 4 Calcium Tungstate Ni 2 Si Nickel Silicide CdS Cadmium Sulphide NiSO 4 Nickel Sulphate CdSe Cadmium Selenide NiP Nickel Phosphide CdTe Cadmium Telluride PbF 2 Lead Fluoride CeAl 2 Cerium Alumate PbO Lead Oxide CeF 2 Cerium (III) Fluoride PbS Lead Sulphide CeO 2 Cerium (IV) Oxide PbS Galena Co 3 O 4 Cobalt (II,III) Oxide PbSe Lead Selenide COSi 2 Cobalt Silicide PbTe Lead Telluride Cr 3 C Chromium Carbide Pr Praseodymium REE Glass CrN Chromium (III) Nitride PrF 3 Praseodymium Fluoride Cr 2 O 3 Chromium Oxide Rb Rubidium REE Glass Cs Caesium REE Glass RbBr Rubidium Bromide CsBr Caesium Bromide RbI Rubidium Iodide CsI Caesium Iodide Sb 2 S 3 Antimony (III) Sulfide CsNO Caesium Si 3 N 4 Silicon Nitride CuI Copper Iodide(Powder) SiC Silicon Carbide CuO Copper Oxide SiO 2 Silicon Oxide CuS Copper Sulphide Sm 2 O 3 Samarium Oxide CuSO 4 Copper Sulphate SmF 3 Samarium Fluoride DyF 3 Dysprosium Fluoride SnO 2 Tin Oxide Er Erbium REE Glass Sr Strontium REE Glass ErF 3 Erbium Fluoride SrF 2 Strontium Fluoride Eu 2 O 3 Europium (III) Oxide SrTiO 3 Strontium Titanate EuF 3 Europium Fluoride Ta 2 O 5 Tantalum Oxide Fe 2 O 3 Hematite TaN Tantalum Nitride Fe 2 P Iron Phosphide TaSi 2 Tantalum Silicide Fe 3 C Iron Carbide TbF 3 Terbium Fluoride FeO Ferrous Oxide TbSi 2 Terbium Silicate FeS Synthetic Trolite TeO 2 Tellurite FeSi 2 Iron Silicide Th Thorium Ree-Glass Ga 2 Se 3 Gallium Selenide ThO 2 Thorium Oxide GaAs Gallium Arsenide TiC (325 mesh) 98% Titanium Carbide GaN Gallium (III) Nitride TiC (solid) 99.5% Titanium Carbide GaP Gallium Phosphide TiN Titanium Nitride 99.5% GaS Gallium Sulphide TiO Titanium Monoxide GaSb Gallium Antimonide TiO 2 Titanium (IV) Oxide Gd 2 O 3 Gadolinium (III) Oxide TiSi 2 Titanium (IV) Sulfide Gd 3 Ga 5 O 12 Gadolinium Gallium Garnet TlBr Thallium Bromide GdF 3 Gadolinium Fluoride TlI Thallium Iodide HfO 2 Hafnium Oxide Tm Thulium Ingot 99.9% HgS Mercury Sulphide (black) TmSi 2 Thulium Silicide HgS Mercury Sulphide (Red) U Uranium REE-Glass HgTe Mercury Telluride UO 2 Uranium Oxide HoF 3 Holmium Fluoride VC Vanadium Carbide In 2 Se 3 Indium Selenide V 2 O 5 Vanadium (V) Oxide In 2 Te 3 Indium Telluride WC Tungsten Carbide InAs Indium Arsenide WSi 2 Tungsten Silicide InP Indium Phosphide WTi W 95%; Ti 5%; InS Indium Sulphide Y 2 O 3 Yttrium Oxide InSb Indium Antimonide Y 3 Al 5 O 12 Yttrium Aluminium Garnet K Potassium REE Glass YbF 3 Ytterbium Fluoride KBr Potassium Bromide ZnS Zinc Sulphide KCl Potassium Chloride ZnSe Zinc Selenide La Lanthanum REE Glass ZnTe Zinc Telluride La 2 O 3 Lanthanum (III) Oxide Zrb 2 Zirconium Boride LaB 6 Lanthanum Hexaboride ZrC Zirconium Carbide (Powder) LaF 3 Lanthanum Fluoride ZrN Zirconium Nitride Li 2 Nb 2 O 6 Lithium Niobate ZrO 2 Zirconium Oxide Li 2 Ta 2 O 6 Lithium Tantalate ZrO 2 Zirconium Oxide Yttria Slab 99.5% LiF Lithium Fluoride ZrO 2 Zirconium Oxide Tablets 99.995% REE Free Glass Blank Compounds which are marked * are natural, and the remainder are synthetic. Pure Standards Formulae Name Formulae Name Ag Silver Mo Molybdenum Al Aluminium Nb Niobium As Arsenic Ni Nickel Au Gold Os Osmium B Boron Pb Lead (Very soft material) Be Beryllium Pd Palladium Bi Bismuth Pt Platinum C Carbon Re Rhenium Cd Cadmium Rh Rhodium Co Cobalt Ru Ruthenium Cr Chromium Sb Antimony Cu Copper Sc Scandium Fe Iron Se Selenium Gd Gadolinium Si Silicon Ge Germanium Sn Tin Hf Hafnium Ta Tantalum In Indium (Very soft material) Te Tellurium Ir Iridium Ti Titanium La Lanthanum Tl Thallium (Very soft material) Mg Magnesium Tm Thulium Mn Manganese V Vanadium W Tungsten Natural Mineral Standards Formulae Name Formulae Name NaAlSi 3 O8 Albite Ca(Mg,Fe)Si 2 O 6 Diopside Fe 3 Al 2 Si 3 O 12 Almandine Garnet CaMg(CO 3 ) 2 Dolomite Ca 3 Fe 2 (SiO 4 ) 3 Andradite CaF 2 Fluorite CaSO 4 Anhydrite Mg 2 SiO 4 Forsterite Ca 5 (PO 4 ) 3 (F,Cl,OH) Apatite Mn 3 Al 2 Si 3 O 12 Garnet Spessartine (Ca,Mg,Fe) 2 (SiAl) 2 O 6 Augite NaAlSi 2 O 6 Jadeite Cu 3 (CO 3 ) 2 (OH) 2 Azurite Formulae Name BaSO 4 Baryte (Cumbria) Al 2 SiO 5 Kyanite BaSO 4 Baryte (Shropshire) Fe 3 O 4 Magnetite BaTiS 3 O9 Benitoite Cu 2 CO 3 (OH) 2 Malachite Be 3 Al 2 Si 6 O18 Beryl (Mg.Fe) 2 SiO 4 Olivine CaCO 3 Calcite KAlSi 3 O8 Orthoclase Formulae Name FeS 2 Pyrite SrSO 4 Celestine MnSiO 3 Rhodonite BaAl 2 Si 2 O8 Celsian CaTiSiO 5 Sphene FeCr 2 O 4 Chromite Zn 2 SiO 4 Willemite Cu 2 O Cuprite CaSiO 3 Wollastonite Cu 2 S Chalcocite ZrSiO 4 Zircon CuFeS 2 Chalcopyrite Natural Minerals Formulae Name CaAl 2 Si 2 O8 Anorthite Powder K(Mg,Fe) 3 AlSi 3 O10(OH) 2 Biotite Powder PbCrO 4 Crocoite Powder PbS Galena Ca 2 ,(Mg,Fe,Al) 5 (Al,Si)8O 22 (OH) 2 Hornblende (Amphibole) FeTiO 3 Ilmenite Powder SiTiAlFeMgCaNaKO Kaersutite (KK1-15 AlSi 2 O 6 Pollucite Natural Minerals (No Certificate of Analysis) Formulae Name Formulae Name CaAl 2 Si 2 O8 Anorthite NiS Millerite (Nickle Sulphide) (Mn,Ca)SiO 3 Bustamite (Ce,La,Th NdY)PO 4 Monazite SnO 2 Cassiterite (Tin Oxide) (Ce,La,Th)PO 4 Monazite Powder SrSO 4 Celestine KAl 2 (AlSi 3 O10) Muscovite CuFeS 2 Chalcopyrite SiO 2 Obsidian FeCr 2 O 4 Chromite ZnS Sphalerite CoAsS Cobaltite LiAlSi 2 O 6 Spodumene (Lithium Aluminium Silicate) Chrome Diopside Na 4 AlBe(Si 4 O 12 )Cl Tugtupite FeTiO 3 Ilmenite Sb 2 O 3 Valentinite (Antimony Oxide) KalSi 3 O 6 Microcline NBS Standards Formulae Name Notes SRM 101g Cr 18%; Ni 10% AISI 304L Stainless Steel SRM C1287 High Alloy Steel AISI 310 Mod. ACI HK SRM 160b Cr 19%; Ni 12%; Mo 3% AISI 316 Stainless Steel SRM 121d Cr 17%; Ni 11%; Ti 0.3% AISI 321 Stainless Steel SRM 343a Cr 16%; Ni 2% AISI 431 Stainless Steel SRM 361 - AISI 4340 Steel SRM 132b - AISI M-2 Tool Steel SRM 478 Cu 73%; Zn 27% Cartridge Brass SRM 481 Au/Ag Set of 6 Gold-Silver wires SRM 482 Au/Cu Set of 6 Gold-Copper wires SRM 710 Soda-Lime-Silica glass - SRM 1872 Set of three glasses K-453; K-491; K-968 SRM 1134 High Silicon Steel - SRM 1160 Ni-80% Mo-4% Fe-14% Electronic & Magnetic alloy SRM 1276a Cu 67.5%; Ni 30.8% CDA 715 SRM C2400 High Alloy Steel ACI 17/4 PH SRM 872 Phosphor Bronze B2 CDA 544 SRM 179 High Silicon Steel - SRM 480 W 78.5% Mo 21.5% Tungsten 20% Molybdenum Alloy BAS EURO Standards Formulae Name Notes 481-1 Cast Iron - 281-1 Cr 18.7%; Ni 9.3% Highly alloyed steel 553-1 High Carbon Fe-Cr B.C.S. No. 204/4 B.C.S. Stainless Steel Spectroscopic Standards Formulae Name Notes S.S. No. 62 Austenitic B.S. 970 En 58D S.S. No. 63 Austenitic B.S. 970 En 58A & 58E S.S. No. 72 Ferritic - S.S. No. 461 Austenitic - S.S. No. 464 Austenitic - S.S. No. 465 Austenitic - S.S. No. 466 Austenitic - S.S.-CRM No. 474 - B.S. 970, type 317 S.S. No. 495/1 13% Manganese steel Containing Ni & Cr B.C.S. No. 204/4 High Carbon Ferro-Chromium BCS No. 179/2 High-Tensile Brass - BCS/SS-CRM No 470 Ferritic Stainless Steel - BCS/SS-CRM No 355 Tin Ore Sn 31.42% MBH#206A355 Assorted Standards Formulae Name Notes ISO 3585 Borosilicate 3.3 glass Duran glass AISI 316 Stainless Steel EN58J Wire. AISI 304L Stainless Steel From Advent (1mm wire) Glass No 1360-3 B.S.153 AISI Grade 430 F Stainless Steel B.S. 154 Stainless Steel 430FR (High Silicon) M.B.H. Standards Formulae Name Notes 27X14386 Ni; Cr; Co; Mo Cast. 11X S/1-CR1 Corr.Resist Cast Iron Chill cast. 210X11775 Ni; Co; Cr; Al; Ti Cast. 212NN50.01 Ni Rem; Cu 30%; Sn 10%; Fe 4%. BNF. 31XWSB1 Silicon Brass Cast. 59XG77J1 Al; Zn; Mg; Cu Cast. 81XPA12.5 Sb 12.6%; Pb 87.4% 111X12670 Cr 19.31%; W 10.1% Cobalt/Tungsten Cast. 204JC Fluorspar Swedish Inst for Metals Res. 206ABL5 Uranium Ore. U 7.09% Canada Centre for Mineral and Energy Technology 206A355 Tin Ore. Sn 31.42% BCS-CRM No. 355 13MBS89 Martensitic Stainless Steel AISI 410 13MBS91E Martensitic Stainless Steel AISI 430 13MBS186A High Alloy Stainless Steel INVAR 36 14XHS1 High Speed Steel Tool steel T-1 (37MBS314B) (37MBS360A) (37MBS630 Copper Alloy CDA 314, CDA 360, CDA 630 14HYT2/2 Steel Ref 0683 Bronze (85c,5Sn,5Pb,5Zn) C13X170020 Austentic Stainless Steel C55XG02D60 Aluminium/Silicon/Copper Chippings (55XG900J5) (55XG26H5) (55XG04H8) (55XG04H6) Aluminium/Silicon/Copper Cast 43XZ2 Zinc/Aluminium/Copper Cast 55XG900JB Aluminium/Silicon/Copper Cast 58XG40H9 Aluminium/Zinc Cast FCr-3-1 14M B.S. 190 High Manganese Stainless Steel 13X 18001 Austenitic Stainless Steel Cast (65XMGA5) (65X MGA1) (65XMGA3) Manganese/Aluminium/Zinc Cast 54X G231 H4
Graphene Synthesis & Applications
Graphene Synthesis & Applications Graphene is a single atomic layer of carbon atoms tightly packed in a two-dimensional honeycomb lattice. This novel material is atomically thin, chemically inert, consists of light atoms, and possesses a highly ordered structure. Graphene is electrically and thermally conductive, and is the strongest material ever measured. These remarkable properties make graphene the ideal support film for electron microscopy. Synthesis: the substrate-free gas-phase method Graphene is a single atomic layer of carbon atoms tightly packed in a two-dimensional honeycomb lattice. The novel material has generated great interest throughout the scientific and technological community because of its remarkable properties and numerous potential applications. However, obtaining pure and highly ordered graphene has been a challenge. Small quantities of ultrahigh-quality graphene have been isolated through an unwieldy and time-consuming process involving the mechanical exfoliation of highly oriented pyrolytic graphite. Alternative methods require substrates or graphite to create atomically-thin sheets, and these techniques involve multiple steps, expensive substrates, or non-ambient conditions. Furthermore, the sheets produced by these alternative methods exhibit defects, disorder, and oxygen functionalities that have a detrimental effect on the properties of graphene. The substrate-free gas-phase method is the first and only process that can synthesise ultrahigh-quality graphene in a single step, without the use of substrates or graphite. Graphene sheets are created through the delivery of liquid alcohol droplets directly into atmospheric-pressure microwave-generated plasmas. Extensive characterisation of the synthesised graphene has proven that the sheets are oxygen-free and exhibit a highly ordered structure. The graphene produced by this unique method can immediately be utilised for graphene applications. Application: direct imaging of soft and hard nanomaterials The interfaces between soft and hard nanomaterials have been the subject of extensive research. Nanoparticles coated with molecular layers have been shown to self-assemble into novel structures that could potentially be used in electronics, sensors, and photonics. Self-assembly is influenced by the nature of molecular coatings and thus more detailed characterisation of these soft materials is needed. However, imaging surface molecules and their interfaces with nanoparticles at the atomic scale is a significant challenge. The transmission electron microscope (TEM) imaging of functionalised nanoparticles has been attempted. It has not been possible to observe molecular surface layers and their interfaces with nanoparticles at the atomic level. Modern aberration-corrected TEMs can produce atomic-resolution images of soft and hard nanomaterials. However, conventional TEM support films (e.g. ultrathin amorphous carbon) limit the capabilities of these advanced microscopes because they contribute to overall electron scattering and diminish the contrast of low-atomic number specimens. The TEM imaging of the interfaces between soft and hard nanomaterials therefore requires better support films that have a lower dynamical interference with an imaging object. Graphene is the ideal TEM support film. The material possesses a highly ordered structure and is atomically thin, chemically inert, structurally stable, and electrically and thermally conductive. The ultrahigh-quality graphene produced by the substrate-free gas-phase method has enabled the unsurpassed TEM imaging of organic molecules and the interfaces between soft and hard nanomaterials. The pure and highly-ordered sheets were used as a near-invisible support film to directly image the atoms in a gold nanoparticle and its surrounding citrate coating. The results showed that the synthesised graphene can be used to directly observe nanoparticles functionalised with a diverse range of molecular coatings, such as proteins and DNA.
Guide to TEM Grids, Handling and Preparation
Selecting Grids There are a range of plain grids, support grids and more available for use, see our TEM gride selection guide . Large continuous structures: an open mesh, 200 (lines/inch) or less is best. However, the support may have flaws or is damaged, therefore an elastic and strong film is required. Formvar with a thin coating of carbon provides these features. At the other extreme, resolution and high contrast are major consideration. So if the final published magnification is higher than x600k, ideally no support is used under the specimen, since any support lowers contrast and resolution, however little that may be. Fibrous structures: or other material that may stretch across a small hole in a support film can provide that opportunity. Lacy or holey films and plain, very fine mesh grids (>1000 mesh) could also be used. Without a support immediately under the object of interest, dark field electron microscopy is also possible. Many applications fall between the above two extremes. Small particles : finer 300 mesh grids give better support; this results in less film breaking, and less specimen movement is likely. Many users would find the common Formvar with thin carbon adequate, but thin (or no) Formvar and a thicker (self supporting) carbon film will be stronger, but less elastic. For a given electron density a Formvar film shows slightly more intrinsic structure and is weaker than a carbon film. Pure carbon films, if evaporated onto mica and transferred to grids, do not adhere well and will float off on any solution. The preferred method for producing carbon films is through evaporation onto Formvar and a thicker layer of carbon, ~60nm. Then the user can dissolve the Formvar in the laboratory - retaining a little Formvar on the grid bars which anchor the carbon film. Many failures using the negative staining method and support films relate to too much or too little retention of the negative stain on the grid. A large black area is not likely to reveal any fine structures and heats up quickly under the beam, destroying that square of material. Even distribution is achieved by repeated applications and blotting of the specimen grid and the negative stain. For the final blotting it is important not to remove too little or too much of the staining solution. Support Film There are various support films available for coating of plain grids, they have different procedures for use. The steps for preparation of adhesive coated grids to make carbon coated grids is below: Submerge about 5cm of Scotch clear tape (3M) into 10ml of Dichloroethane (Ethylene Dichloride); shake and discard the tape. The solution now becomes “grid-glue” Place the grids (dull side up) on a piece of filter paper (dust-free room). Take a pipette and place a drop of“grid-glue” on top of each grid. Let the grids dry. The grids are now ready to pick up the carbon foil and make the carbon coated grids. Reaction of Ni and Cu Grids How do Nickel and Copper Grids React with Periodic Acid? Periodic Acid + Ni Ni-Periodate + H2 Periodic Acid + Cu Cu-Periodate + H2 In this case you should use Gold Grids. Grid & Storage Life TEM grids should be stored in a dry, dust-free environment. Which is essential to prevent contamination and mechanical damage. For long-term storage or to prevent the oxidation of copper and degradation of the coating, grids should be stored in a vacuum desiccator. While copper grids themselves can last for years, the Formvar/carbon film has a shorter shelf life. Unused coated grids can typically last for several months to a year if kept in a clean, dry environment. Always note: The Formvar film can degrade over time, leading to broken films. High humidity accelerates the degradation of the film and oxidation of the copper grid. Quality storage boxes, such as the TEM Grid Boxes , allow for the safe storage of up to 96 grids and include indexed, secure storage for easy identification. Ideal storage conditions: Dry conditions – ideally in a desiccator or sealed container with silica gel In the original grid box to avoid dust Room temperature, avoiding heat or large temperature changes Some labs also glow discharge the grids before use to remove surface contamination. Sample Preparation Cleaning grids is vital before sample preparation should begin. Using glow discharge or plasma cleaners is ideal for this purpose. See here for Glow Discharge cleaners See here for Plasmsa Decontaminators Using the right process for you sample preparation will ensure quality imaging. Thin samples are required, >100µm to allow electrons to move through the sample, which also means the nanoparticles used to prepare the sample should be >100µm and also only be in a single layer. Equipment and Materials: Sample TEM grid coated with carbon film Pipette for 20µl Sonicator/agitator Grid tweezers (self-closing) Drying light (optional) Step 1: Prepare the sample by dilution with water, add nanoparticles. Step 2: Sonicate the sample/nanoparticles to remove any clumps or aggregation of sample. Step 3: Draw 20µl of the sample and nanoparticle mixture and drop cast onto TEM grid coated with carbon film. Evaporate the liquid from the grid for ~1hr. The grid is then ready to be analysed in the TEM. Here is a video showing the steps of sample preparation for drop cast samples followed by a demonstration of the capabilities of the JEOL F200 by the Microscopy Australia network at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney.
Heavy Carbon Film
Formvar with "heavier" 15‐25nm carbon coating These grids have a layer of carbon on a thin Formvar film. The carbon layer is thicker than that applied to other support films, making this an extremely strong and resilient specimen support for most applications. Films are mounted on the darker side of the grid. They are extremely stable under the electron beam. For high resolution applications the Formvar may be removed. This results in less electron density, increased contrast and almost no granularity at high magnifications. To remove the Formvar film: (use a fume hood) Note, dipping grids in a solvent to remove Formvar causes the carbon film to float off. It is more effective to only partially remove the Formvar. This method leaves some Formvar under the grid support bars. Place two pieces of filter paper in a glass Petri dish and raise one side of the dish slightly. Saturate filter paper with chloroform; a little liquid should be visible in the lower end of the dish. Using tweezers hold a grid with the carbon side up and touch the grid several times against the filter paper. Briefly touch the grid to the free chloroform (do not immerse). Then blot on dry filter paper. Thickness of support films The thickness of our support films tends to be towards the lower end of each indicated range. Formvar Films: While floating on water during processing these have a colourless to pale grey appearance in reflected light. The films have been measured using a Tencor Alpha‐Step 200 profilometer. The thickness across the film ranges from 35 ‐ 70nm. Carbon layer (measured by a film thickness monitor during the carbon evaporation process): 20 to 30nm. Handling and care of support films Grids should be gripped by the outside rim to avoid rupturing the support film. When removing grids from the storage box it is advisable to do so under a dissecting microscope. If a grid must be laid on a flat surface, use a fibre‐free tissue. When specimen preparation involves dipping a grid into liquid, always immerse edge first. When using double‐sided adhesive tape to hold a grid during specimen preparation, allow only the extreme outer edge of grid to contact the adhesive and remove grid by pulling horizontally away from adhesive to avoid support film damage.
Life Expectancy of Filaments (New and Refurbished)
Life expectancy is defined as the number of hours of operation until 50% of them fail. This means that it is possible for some lamps to fail after a short amount of time and for some to last significantly longer than the rated lamp life. This is an average (median) life expectancy. The life expectancy of filaments, new or refurbished, from any reasonable manufacturer is identical. Two factors influence filament life expectancy ‐ degree of vacuum and heating voltage. The heating voltage required for saturation is dependent on the bias current selected, so in a SEM/ microprobe a high bias current may be run to achieve something like 40µm emission ‐ but the price paid may be only 40 hours of filament life. A poor vacuum would shorten filament life, as under those conditions the filament succumbs due to evaporation and not etching. In a TEM the emission may be only 10µm (low bias setting, therefore low heating voltage), and then a filament may last 100 hours and more ‐ if there is a good vacuum. A vacuum of less than 10‐5 mbar will result in etching reducing filament life. Dead filaments with the wire burned out away from the centre emission tip may have suffered from poor vacuum, and they are 'etched'. Filaments which show an excessive metal deposit on the insulator's base may have been operated at an excessive heating current. Using an excessive bias setting and over‐saturating the filament voltage (particularly early in the life of a filament) are the main reasons for early filament failure. Without extensive tests it is impossible for an individual to determine minor filament variations. Operator control affects filaments much more than would another batch of thoriated tungsten wire. The degree of vacuum measured in the gun chamber is important in regard to filament life. All filaments are annealed. They are heated under vacuum prior to adjusting the centre.
Micro Sieve Conversion Table
Micro-sieve set mesh to micron conversions for the following size mesh 25, 35, 45, 60, 80, 120, 170, and 320. U.S. MESH INCHES MICRONS MILLIMETRES 3 0.2650" 6730µm 6.730mm 4 0.1870" 4760µm 4.760mm 5 0.1570" 4000µm 4.000mm 6 0.1320" 3360µm 3.360mm 7 0.1110" 2830µm 2.830mm 8 0.0937" 2380µm 2.380mm 10 0.0787" 2000µm 2.000mm 12 0.0661" 1680µm 1.680mm 14 0.0555" 1410µm 1.410mm 16 0.0469" 1190µm 1.190mm 18 0.0394" 1000µm 1.000mm 20 0.0331" 841µm 0.841mm 25 0.0280" 707µm 0.707mm 30 0.0232" 595µm 0.595mm 35 0.0197" 500µm 0.500mm 40 0.0165" 400µm 0.400mm 45 0.0138" 354µm 0.354mm 50 0.0117" 297µm 0.297mm 60 0.0098" 250µm 0.250mm 70 0.0083" 210µm 0.210mm 80 0.0070" 177µm 0.177mm 100 0.0059" 149µm 0.149mm 120 0.0049" 125µm 0.125mm 140 0.0041" 105µm 0.105mm 170 0.0035" 88µm 0.088mm 200 0.0029" 74µm 0.074mm 230 0.0024" 63µm 0.063mm 270 0.0021" 53µm 0.053mm 325 0.0017" 44µm 0.044mm 400 0.0015" 37µm 0.037mm
SEM Calibration Specimen Mount Types
There are mounts available for most SEMs on the market which are listed below from Type A to Type R. The test specimen of calibration standard is mounted on the selected SEM specimen mounts with conductive cement. All test specimens and calibration standards are normally mounted in the centre of the specimen mount. If a specific location other than the centre is needed, Mount G should be ordered along with a clear drawing for the custom mounting required. Example of specimen position Mounts Type Product Dimensions (D = Head diameter; P = Pin diameter; PL = Pin length Compatible SEM A Pin Mount: D=12.7mm; P=3.2mm; PL= 7.9mm FEI/Philips, Cambridge, Leica, TESCAN, CAMSCAN, ASPEX, Phenom B Pin Mount: D=12.7mm; P=3.2mm; PL=14.3mm AMRAY C Cylinder mount: 9.5mm dia. x 9.5mm Cylinder, JEOL D Cylinder mount: 15mm dia. x 15mm Cylinder, JEOL, ISI/ABT/TOPCON E Cylinder mount: 15mm dia. x 10mm Cylinder, JEOL, ISI/ABT/TOPCON F Pin Mount: 12.7mm x 3.2mm pin. PL=6mm ZEISS/LEO SEMS FESEMs/FIBS G You Supply Mount or Mount of Your Choice, not listed here (contact customer service) K Cylinder mount: 15mm dia. x 6mm Cylinder, M4 Hitachi, Agilent / Keysight L Cylinder mount: 25mm dia. x 6mm Cylinder, M4 Hitachi, Agilent / Keysight M Cylinder mount: 12.2mm dia. x 10mm Cylinder, JEOL O Platform mount: 31.7mm dia. x 6.47mm Cambridge S4 Mount P Pin Mount: 12.7mm dia. x 15.7mm height AMRAY special slotted head Q Cylinder mount: 25mm dia. x 10mm Cylinder, JEOL R Pin mount: D=25.4mm; pin=3.2mm FEI/Philips, Cambridge, Leica, TESCAN, CAMSCAN, ASPEX, Phenom
SEM Sample Mounting
Methods for clean and effective mounting of various types of samples for SEM 1) Mounting Samples Using Conductive Adhesives It is important that the sample is securely fixed to the mount for imaging and analysis. The conductive adhesive surrounding the sample allows a pathway for the negative charge of the electron beam to move away from the specimen to the conductive base of the mount. Ideal for: Focused ion beam (FIB) Electron backscatter diffraction (EBSD) Atomic force microscopy (AFM) High resolution imaging or high tilt angles Equipment and Materials: Conductive adhesives , also see EM - Silver-loaded Epoxy Procedure SEM mount , there are many styles of mounts available for all SEMs and types of imaging required SEM sample preparation stands SEM mount grippers PELCO replaceable tip wafer tweezers, style 7 SEM mount storage box, 12 mounts Permanent markers Gloves Vortex mixer See more details in the video below by the Microscopy Australia network at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney. 2) Mounting Bulk Samples Bulk samples are a solid piece of material that can be manipulated by hand or by tweezers including resin blocks, petrographic thin sections, wafers, glass, insects parts, metals and composites. It is important that the sample is securely fixed to the mount for imaging and analysis and that there is a pathway for the negative charge of the electron beam to move away from the specimen to the conductive base of the mount. Equipment and Materials: Sample piece (the smallest piece possible that contains the necessary structures) SEM mount , there are many styles of mounts available for all SEMs and types of imaging required Conductive tape or tabs SEM sample preparation stands SEM mount grippers SEM mount storage box Permanent markers Gloves See more details in the video below by the Microscopy Australia network at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney. 3) Mounting Powdered Samples Powdered samples include substances like pollen, sand and starch. It is important that the sample is securely fixed to the mount for imaging and analysis. The sample also needs to be spread thinly and evenly across the adhesive on the mount to maximise the conductivity of the sample and to ensure there is a pathway for the negative charge of the electron beam to move away from the specimen to the conductive base of the mount. Equipment and Materials: Sample (very small amount required ~0.1g) SEM mount , there are many styles of mounts available for all SEMs and types of imaging required Conductive tape or tabs Spatula Foil SEM sample preparation stands SEM mount grippers SEM mount storage box Permanent markers Gloves See more details in the video below by the Microscopy Australia network at the Electron Microscope Unit (EMU) within the Mark Wainwright Analytical Centre (MWAC) at UNSW Sydney. 4) Mounting Nanoparticles or Particles in Suspension This is for particulate nanomaterials that are 1-100nm in at least one dimension this includes nanospheres, nanocubes, branch nanoparticles, nantubes, nanorods and nanosheets. The sample needs to be spread thinly and evenly across the adhesive on the mount to maximise the conductivity of the sample and to ensure there is a pathway for the negative charge of the electron beam to move away from the specimen to the conductive base of the mount. Equipment and Materials: Sample (very small amount required for dry samples ~0.1g) Solvent (if using dry sample) SEM mount , there are many styles of mounts available for all SEMs and types of imaging required Sonicator/agitator Pipette Conductive tape or tabs Scissors Wafers or substrate Spatula SEM sample preparation stands SEM mount grippers SEM mount storage box Permanent markers Gloves
Silver-loaded Epoxy Procedure
Using Silver Powder to make silver loaded epoxy Very fine, high purity silver powder may be used to produce electrically highly conducting paints and especially epoxy resins. Usually, the mixture is one half by volume of powder and a quarter each of epoxy components A + B. These materials mix very easily, but conductivity does not gradually change; rather if a little less silver is used, suddenly conductivity may be completely lost. Unlike prepared silver epoxies, the powder has an unlimited shelf life and the mixture ratio can be varied to suit. Also, fast-curing or super-strong epoxy may be used as required and silver powder is rather more economical than prepared epoxies. Note that because of the small particle size the powder and any solutions made are a little yellowish and darker than silver. This relates to particle size and refractive index and not purity.