A special version of slim hole drilling currently emerging as a viable alternative is co//ed tubing drilling (CTD). Whilst standard drilling operations are carried out using joints of drill pipe, coiled tubing drilling employs a seamless tubular made of high-grade steel. The diameter varies between 1 3/4" and 3 1/2". Rather than being segmented the drill string is reeled onto a large diameter drum.  [c.53]

All pipelines will be circulated clean and those that are buried, or on the seabed, left filled with water or cement. Surface piping will normally be cut up and removed. Flexible subsea pipelines may be reeled-in onto a lay barge and disposed of onshore.  [c.370]

Throughout this section we have focused attention on the thermodynamic considerations which help explain the lowering and broadening of polymer melting points. The same thermodynamic arguments can be applied to the raising and sharpening of this transition temperature through annealing. When a crystal is maintained at a temperature between the crystallization temperature and the equilibrium melting point, an increase in T j is observed. This may be understood in terms of the melting of smaller, less-perfect crystals and the redeposition of the polymer into larger, more stable crystals. This is analogous to the procedure of digesting a precipitate prior to filtration. There is more to the story than this, however. The digestion analogy suggests that those crystals which are enlarged simply add more folded chains around their perimeter. In fact, x-ray diffraction studies reveal progressive thickening of lamellae as T increases. This means large-scale molecular reorganization within the crystal. Such rearrangements apparently require the molecule to snake along the chain axis, with segments being reeled in and out across the crystal surface. The process of annealing, therefore, not only involves crystal thickening, but also provides the opportunity to work out kinks and defects.  [c.218]

Industrial yam uses a continuous washing and drying process based on self-advancing reels. Whereas the processing of cake yam can take many days to complete, the continuous process is over in minutes. The process is less labor intensive and more productive than the cake system, but the engineering and maintenance requirements are easily underestimated. It is most used for industrial yams, still the reinforcement of choice for radial tire carcasses. For these appHcations the strain built in by fast drying is no disadvantage because the yams are expected to be at their best when bone dry. Dyeing is not required and an off-white color is tolerable. The main objective of the washing system is to remove acid and sulfur compounds that would affect the strength of the yam duting prolonged operation at high temperature.  [c.349]

The Fourdrinier wire is mounted over the breast roU at the intake end and at the couch roU at the discharge end. Between the two roUs, it is supported for the most part by foils and suction boxes. Foils (Fig. 5) are wing-shaped elements that support the wire and induce a vacuum at the downstream nip. Foil geometry can be varied to provide optimum conditions. After passing over the foils, the wire and sheet pass over suction boxes where more water is removed. Most machines also include a suction couch roU for additional water removal. Machine speeds vary chiefly because of limitations imposed by the various products but also because of differences in production equipment. Heavy paperboards require a long drying time, and machine speeds are 50—250 m /min. Very dense papers, eg, glassine and greaseproof and condenser tissue, are difficult to dewater in the forming and press sections speeds range from 20 to 300 m /min, depending on the product. Brown grades, eg, paper bags and linerboard, are produced at 200—1000 m /min, depending on basis weight and the site of the paper machine. With the advent of the suction pickup, which closes the draw between the forming and press sections, speeds of newsprint machines increased from 400 to 800 m /min. Closing the transfer of the sheet through the entire press section and increasing the dryness at the first open draw into the dryer section from 35—38% to 41—44% combined with careful designs of the web path through the dryer section has increased newsprint machine speeds to ca 1500 m /min. The majority of machines operate at 800—1200 m /min. Drying capacity restraints and difficulties in reeling the product limit modem tissue machine speeds to 1500—1800 m /min. Most tissue machines operate at lower speeds. Novel designs for web handling, reeling, and roU change will permit tissue machine speeds of up to ca 2000 m /min in continuous operation.  [c.6]

Aside from dipping, the other main products produced from natural mbber latex are elastic thread and foam products. Latex thread is produced by extmding a suitable latex compound under gravity through a tube of the appropriate diameter into an acid bath. On coming into contact with the acid, the latex gels. It is then taken through washing baths and a drying/vulcanization oven in a continuous process that results in reels of thread. This thread is used primarily in the garment industry. Latex foam is produced by mechanically incorporating air into a stabilized latex compound until the required density is achieved. The foam is gelled by either a delayed action chemical or by a heat gelation process before vulcanization and drying. The main appHcations of latex foam are in molded products such as mattresses and cushions, and spread foam for carpet backings. Unlike the dipped products industry, the latex foam industry has suffered from competition from synthetic styrene—butadiene mbber (SBR) latex. Many foam products can be made from either NR, SBR, or blends of the two.  [c.274]

However, this is a more expensive arrangement. A more economical method is to use a full-wave, diode bridge converter and an IGBT inverter unit combination as shown in Figure 6.50 in place of an additional thyristor or IGBT feedback circuit. The d.c. link bus is now made a common bus for all the drives operating on the process. During a regenerative mode, such as during uncoiling the pay-off reels, the voltage of the d.c. bus will rise and will be utilized to feed the other drives. This process will draw less power from the source. The regenerative energy is now utilized in feeding the process system itself rather than feeding back to the source of supply. There is now only one converter of a higher rating, reducing the cost of all converters for individual drives and conserving regenerative energy again at a much lower cost.  [c.143]

Reeling-unreeling operations such as  [c.533]

Reflected Electron Energy-Loss Spectroscopy (REELS)  [c.25]

EELS is used in a transmission mode in conjunction with TEMs and STEMs. Samples must be very thin (hundreds of angstroms) and beam energies must be high (100 keV and up) to prevent the single scattered EELS signal from being swamped by a multiple scattering background. A direct consequence of this requirement is that the spatial resolution of transmission EELS is not much worse than the beam size, since a 100-kV electron passing through a sample and scattered only once does not deviate much in direction. Thus, in a STEM with a 2-A beam size the spatial resolution of EELS for a sample 100 A thick might be only 3—4 Al Although the main use of transmission EELS is to provide elemental composition like EDS/WDS it can also provide much information about chemical states and about electronic structure from the line shapes and exact positions of the energy loss peaks. EELS is also used in a reflection mode (REELS) in Auger spectrometers for surface analysis (see Chapter 5).  [c.119]


Reflected Electron Energy-Loss Spectroscopy, REELS  [c.279]

Reflected Electron Energy-Loss Spectroscopy (REELS) has elemental sensitivities on the order of a few tenths of a percent, phase discrimination at the few-percent level, operator controllable depth resolution from several nm to 0.07 nm, and a lateral resolution as low as 100 nm.  [c.324]

Figure 1 Representation of a typical density of eiectron states for a metal having X K and Z core levels (top) and REELS spectrum expected from metal shown in top panel (bottom). Figure 1 Representation of a typical density of eiectron states for a metal having X K and Z core levels (top) and REELS spectrum expected from metal shown in top panel (bottom).
Suppose a solid with an energy level scheme as in Figure 1 is bombarded by an electron beam of energy Eq where 1. 1 < < 1 1 and E is the binding energy of the core level X(Y). Most of the incident electrons are reflected from the sample surface without energy loss and produce a large peak at Eq called the elastic peak. The incident electrons that scatter from the various occupied states form the REELS spectra shown in Figure lb. Peaks at energy EQ-Ey and Eq-E are due to CEELS excitation, their line shapes reflect the conduction-band density of states. Since the transitions occur in the presence of the empty core level, the line shape in reality reflects the conduction-band density of states in the presence of the core hole. Such a density of states may not be the same as the ground-state density of states that controls the chemical properties of the material, but changes in chemical environment will still result in changes in the excited states. Since the interband and plasmon region involves valence electrons, it is called the valence EELS (VEELS), which with CEELS constitutes a REELS spectrum.  [c.327]

Perhaps the most common use for REELS is to monitor gas—solid reactions that produce surface films at a total coverage of less than a few monolayers. When Eq is a few hundred eV, the surface sensitivity of REELS is such that over 90% of the signal originates in the topmost monolayer of the sample. A particularly powerfiil application in this case involves the determination of whether a single phase of variable composition occurs on the top layer or whether islands occur that is, whether  [c.327]

The degree of surface cleanliness or even ordering can be determined by REELS, especially from the intense VEELS signals. The relative intensity of the surface and bulk plasmon peaks is often more sensitive to surface contamination than AES, especially for elements like Al, which have intense plasmon peaks. Semiconductor surfaces often have surface states due to dangling bonds that are unique to each crystal orientation, which have been used in the case of Si and GaAs to follow in situ the formation of metal contacts and to resolve such issues as Fermi-level pinning and its role in Schottky barrier heights.  [c.328]

Fine structure extending several hundred eV in kinetic energy below a CEELS peak, analogous to EXAFS, have been observed in REELS. Bond lengths of adsorbed species can be determined from Surface Electron Energy-Loss Fine Structure (SEELFS) using a modified EXAFS formalism.  [c.328]

REELS spectrometers are in fact Auger spectrometers, so that elemental identifications can be made easily.  [c.330]

REELS data are commonly displayed as N ), dN/dE or second derivatives of N E). The N E) mode has the advant< e that the background is not lost, as it is for either of the derivative modes, but the relatively weak CEELS signals are usually dwarfed by the background and so require some level of differentiation to enhance the weak, but sharp, CEELS features. However, the signal-to-noise ratio is degraded by successive differentiations so that the ultimate detectability is worsened. REELS spectra acquired by lock-in detectors can namrally produce either the first- or second-derivative spectra, while those with N E) outputs usually have provisions to mathematically produce the derivative format. For the strong VEELS signals, the second derivative has the advantage that the peaks occur at the same energy as they do in the N[E) spectra, while those from the first derivative do not. However, a closely spaced, intense pair of N(E) excitations vnll appear as three peaks in the second-derivative mode. It is the author s judgment that the best overall display mode is the first derivative.  [c.330]

Figure 3 First-derivative electron emission spectra from pure lanthanum taken with primary electron beams having energies of 250 and 235 eV showing the unshifted Auger peaks and the shifted REELS peaks. Figure 3 First-derivative electron emission spectra from pure lanthanum taken with primary electron beams having energies of 250 and 235 eV showing the unshifted Auger peaks and the shifted REELS peaks.
Vibrational spectroscopy of atoms and molecules near or on the surface of a solid has become an essential tool for the microscopic description of surface processes such as catalysis and corrosion. The effect of a surface on bonding is sensitively reflected by the frequencies of vibrational motions. Furdiennore, since vibrational selection rules are detemiined by molecular synnnetry that in turn is profoundly modified by the presence of a surface, it is frequently possible to describe with great accuracy the orientation of molecular adsorbates and the synnnetry of absorption sites from a comparison of spectral intensities for surface-bound molecules to those for free molecules [13]. Electron spectroscopy has an advantage over optical methods for studying surfaces since electrons with energies up to several hundred electron volts penetrate only one or two atomic layers in a solid before being reflected, while the dimension probed by photons is of tire order of the wavelengdi. Reflected-electron energy-loss spectroscopy (REELS) applied to the study of vibrational motion on surfaces represents the most highly developed teclmology of electron spectroscopy [14]. Incident electron energies are typically between 1 and 10 eV and sensitivity as low as a few per cent of a monolayer is routinely achieved (figure B 1.6.10).  [c.1325]

Filler Metals. EHer metals ate added to a weld by melting a consumable electrode or a separate wire fed into the weld pool. In the first category, the filler metal is part of the welding electrical circuit and may be in the form of short lengths of covered wire, as in shielded-metal arc welding, or in the form of continuous reels of wire used in semiautomatic, mechanized, and automatic welding processes. SoHd wire is used in the gas—metal and submerged-arc welding processes, whereas a hoUow, flux-fiUed wire is used in flux-cored arc welding. More filler metal in the form of iron powder is sometimes added to the electrode coating or flux. In the second category, the filler metal maybe in the form of short lengths of bate soHd wire, as used in gas welding or manual gas—tungsten arc welding, or in continuous reel form, used in automatic gas—tungsten arc welding.  [c.347]

The Support. For most practical appHcations, the sensitized emulsions must be coated on a base or support to permit convenient handling. There are three basic classes of supports glass, plastic, and paper. Supports are chosen on the basis of dimensional stabiUty, low water permeabiUty, flexibihty, freedom from surface irregularities, compactness, cost, and safety. The relative importance of these requirements depends on the particular apphcation (253). For example, dimensionally stable glass plates are one of the oldest base materials and are excellent supports for the precision photography required in astronomy, telemetry, and microelectronics. However, weight, bulkiness, and fragiUty make glass inappropriate and inconvenient for amateur photography. Clear plastic film supports are the most commonly used bases in modem photography. These materials are designed and selected based on safety, environmental concerns, and how they are to be used, eg, their abiUty to be unwound and rewound on reels and cassettes or rigidity in sheet film formats. The original plastic film supports were prepared from chemically unstable and highly flammable cellulose nitrate. Cellulose nitrate supports have been replaced by solvent-cast materials, eg, cellulose triacetate [9012-09-3] and extmded materials, eg, poly(ethylene terephthalate) [25038-59-9] (PET). These materials are not only safe but also strong and dimensionally and chemically stable. Paper supports are commonly used in products that are viewed in the reflection mode, such as color or black-and-white print materials. Before the silver haUde emulsion layers are coated, some paper products are first undercoated with barium sulfate in a gelatin matrix to improve surface smoothness and visual whiteness in the highlight areas of the prints. Modem paper products are often waterproofed with impervious resin coatings of polyethylene whitened with titanium dioxide (254). Because of the water repeUency of resin-coated materials, fewer chemicals are carried over from one treatment bath to another during processing. Subsequently, chemical replenishment rates can be reduced, an economical and environmental advantage (see WATERPROOFING AND WATER/OILREPELLENCy).  [c.451]

Constmction of underwater (submatine) pipelines does not take place under water. Pipelines are welded onshore and dragged iato position by powerful wiaches on ships floating on the water surface (for short lines), welded on a specially constmcted lay barge, and lowered to the ocean floor by a stinger from one end of the barge or welded onshore, floated on pontoons, and towed to the offshore area where they are lowered iato position. For smaller size pipelines, the lines can be welded onshore and spooled onto large reels, placed on special ships, and spooled iato the offshore trench. In shallow water, or where endangered by anchors or wave action, submatine pipelines are laid ia trenches ia the sea bottom (35). Underwater pipelines are concrete-coated or weighted to overcome the buoyancy effect concrete coatings appHed over the primary coating provide additional protection against damage duting laying and against corrosion. Submatine pipelines are being used regularly to transport oil, natural gas, and other commodities to shore from offshore locations, such as the Gulf of Mexico, the North Sea, and the Arabian Gulf One of the longest and technically challenging submatine pipeline systems is a 2599-km, 1200-mm dia pipeline for transporting natural gas across the Mediterranean Sea and the Strait of Messiaa from gas fields ia Algeria to Italy pipes are laid ia water depths to 610 m. Offshore and onshore pipelines require different design factors (36).  [c.50]

Commercial and Artificial Processing. Commercially, silkworm cocoons are extracted in hot soapy water to remove the sticky sericin protein. The remaining fibroin or stmctural sdk is reeled onto spools, yielding approximately 300—1200 m of usable thread per cocoon. These threads can be dyed or modified for textile appUcations. Production levels of sdk textiles in 1992 were 67,000 metric tons worldwide. The highest levels were in China, at 30,000 t, foUowed byJapan, at 17,000 t, and other Asian and Oceanian countries, at 14,000 t (24). Less than 3000 metric tons are produced annually in each of eastern Europe, western Europe, and Latin America almost no production exists in North America, the Middle East, or Africa. 1993 projections were for a continued worldwide increase in sdk textile production to 75,000 metric tons by 1997 and 90,000 metric tons by 2002 (24).  [c.77]

With excellent specific stiffness and strength, carbon fibers are ideally suited to apphcations where weight reduction results in significant performance and cost advantages. Initially militaty aerospace, space, and recreation were primary markets. The relatively high cost of the fiber prevented penetration into mote cost-sensitive apphcations. Current 1992 prices of standard and intermediate modulus PAN-based carbon fibers such as BASF G30-500 and G40-800, range from 20—60/kg depending on filament count and order volume. Higher modulus products are even more expensive with ultrahigh modulus pitch-based fibers such as Amoco s P-100 exceeding 2000/kg. More recendy carbon fiber composite apphcations have diversified into automotive, ie, brake linings, drive shafts, springs, wheels, and stmctural components for racing cars aircraft engines recreation, ie, fishing rods and reels, termis and racquetball racquets, golf club shafts, baseball bats, hockey sticks, oars, paddles, sailing masts, skis, etc electrical shielding and radar absorption medical, ie, x-ray tables and prosthetic devices and music apphcations, ie, speaker cones and musical instmment components.  [c.8]

Wire. In electroplating wire is uncoded from spools or reels, passed through the processing and plating steps as individual strands, and then recoded. Several spools can be plated simultaneously through multistrand machines. More flexible wires can be handled by a multipass arrangement where the plated wire is directed back and forth through the plating tank. Wire has also been plated in loose cods without uncoiling, but the plating quaUty is less. Wire is plated commercially with several metals. Among these are copper and copper alloys, 2inc, iron and iron alloys, nickel and nickel alloys, gold, and sdver. Special machines are avadable to plate wire, and come in many si2es from desk top to shop si2e models.  [c.145]

In Reflected Electron Energy-Loss Spectroscopy (REELS) a solid specimen, placed in a vacuum, is irradiated with a narrow beam of electrons that are sufficiently energetic to induce electron excitations with atoms or clusters of atoms. Some of the incident electrons reemerge from the sample havii lost a specific amount of energy relative to the well-defined energy Eq of the incident electron. The number, direction k, and energy of the emitted electrons can be measured by an electron energy analyzer. Composition, crystal structure, and chemical bonding information can be obtained about the sample s surface fi om the intensity and line shape of the emitted electron energy-loss spectra by comparison to standards.  [c.25]

Reflected Electron Energy-Loss Spectroscopy, REELS, is a specialized adjunct to AES, just as UPS is to XPS. A small fraction of the primary incident beam in AES is reflected from the sample surface after suffering discrete energy losses by exciting core or valence electrons in the sample. This fraction comprises the electron energy-loss electrons, and the values of the losses provide elemental and chemical state information (the Core Electron Energy-Loss Spectra, CEELS) and valence band information (the Valence Electron Energy-Loss Spectra, VEELS). The process is identical to the transmission EELS discussed in Chapter 3, except that here it is used in reflection, (hence REELS, reflection EELS), and it is most useftil at very low beam energy (e.g., 100 eV) where the probing depth is at a very short minimum (as in UPS). Using the rather high-intensity VEELS signals, a spatial resolution of a few microns can be obtained in mapping mode at 100-eVbeam energy. This can be improved to 100 nm at 2-keVbeam energy, but the probing depth is now the same as for XPS and AES. Like UPS, VEELS suffers in that there is no direct elemental analysis using valence region transitions, and that peaks are often overlapped. The technique is free on any AES instrument and has been used to map metal hydride phases in metals and oxides at grain boundaries at the 100-nm spatial resolution level.  [c.281]

REELS can detect any element from hydrogen to uranium and can discriminate between various phases, such as SnO and Sn02, or diamond and graphite. By varying the primary electron beam energy Eq, the probing depth can be varied from a minimum of about 0.07 nm to a maximum of 10 nm, where these limits are somewhat sample dependent. The best probing depth is at least twice as good as any other surface technique except ISS, to which it compares favorably with the added advanti e of a spatial resolution of a few microns. The lateral resolution is limited only by technological factors that involve producing small electron beam spot sizes at energies below 3 keV, rather than fundamental beam—solid interac-  [c.324]

The principal applications of REELS are thin-film growth studies and gas-surface reactions in the few-monolayer regime when chemical state information is required. In its high spatial resolution mode it has been used to detect submicron metal hydride phases and to characterize surface segregation and difRision as a function of grain boundary orientation. REELS is not nearly as commonly used as AES orXPS.  [c.325]

EELS is an electron-in-electron-out technique that has two forms The emitted electrons can be analyzed after transmission through very thin (< 100 nm) specimens or they can be analyzed after reflection from thick specimens. For samples thinned to 100 nm the transmission mode of EELS yields a lateral resolution of a few nm, but for specimens used in the reflected mode the best lateral resolution (as of this writing) is 100 nm. Transmission electron energy-loss spectra are obtained on STEM or TEM instruments and are covered in Chapter 3. Within the reflected mode there are two major versions distinguished by their energy resolution. The high-energy resolution EELS (HREELS) has a resolution in the meV range, suitable for molecular vibrational excitations and is covered in Chapter 8. The low-energy resolution reflected EELS (REELS) has a tj pical resolution of 1 eV, sufficient to resolve electronic excitations like plasmons, interband transitions, or corelevel excitations. REELS currendy has a lateral resolution of 100 nm, while HREELS has a resolution in the mm range. HREELS and REELS, because of their high surface sensitivity, require ultrahigh vacuum, while transmission EELS requires only high vacuum. Only REELS and transmission EELS exhibit extended fine structure suitable for atom position determinations. This article considers only REELS.  [c.325]

With the advent of SAM instruments it soon was shown that they could be operated as REELS-mapping microprobes using a technique called Reflected Electron Energy-Loss Microscopy (REELM). The strong VEELS signals can compensate for the reduced currents required to maintain Eq below the pass energy of a CMA, e.g., 3 keV. As a result, maps of very high contrast can be produced in just a few minutes, or maps with a lateral resolution of 100 nm can be produced by further reducing the electron current. If Eq is set to a few hundred eV, to optimize the surface sensitivity, modern SAM instruments can produce spot sizes of a few microns sufficient to generate good REELM ims es.  [c.328]

Samples used in REELS must be ultrabigb-vacuum compatible solids or liquids, but they may be metals, semiconductors or insulators. Because REELS detects a reflected primary electron, rather than a secondary electron like an Auger electron, surface charging will not affect the electron s detected kinetic energy. As a result, insulating surfaces, even if charged, will generate good REELS signals. To avoid severe charging from the much larger number of secondary electrons it is sufficient to make the flat areas of an insulator about the same size as the incident beam spot size. By adjusting the primary beam energy and angle of incidence, zero absorbed current can be obtained.  [c.329]

An Auger spectrometer or scanning Auger microprobe can be operated as a REELS spectrometer or Reflected EELS Microprobe (REELM) instrument at no additional cost in hardware or software. In contrast to AES, REELS requires that the incident electron beam energy Eq be less than the pass energy of the analyzer, usually less than 3 keV. Also, to achieve a reasonable energy resolution, REELS must have Eq less than about 500—1000 eV for the Cylindrical Mirror Analyzers (CMA) typical of most AES instruments. Incident electron beams with Eq in this range have considerably larger spot sizes or lower currents than those of the 5—20 keV beams used in AES. Electronic processes such as core-level excitations, plasmons, and interband transitions have energy widths of the order of 1 eV. Because deviations from Eq produce chromatic aberrations in the focusing of fine-spot electron  [c.330]

See pages that mention the term REELS : [c.27]    [c.83]    [c.198]    [c.198]    [c.173]    [c.10]    [c.533]    [c.5]    [c.136]    [c.324]    [c.325]    [c.326]    [c.327]    [c.329]    [c.331]   
Encyclopedia of materials characterization (1992) -- [ c.25 , c.324 ]