Base deposition

Where carbonate, phosphate, or sulfate scale-based deposits have been found in boiler systems, analyses show that they almost always contain some silica or silicate as well. Typically, this is less than 8 to 10% unless there is a specific underlying silica-related problem (under such circumstances, the deposit may contain more than 20-30% Si02). 

Steam blanketing results in a departure from nucleate boiling (DNB) and typically dryout (localized total evaporation) conditions. It also may result in the formation of secondary (silicate-based) deposits that cannot be rinsed or resolublized, overheating problems, and eventual boiler tube or furnace shell rupture. 

The tube failures resulted from the development of corrosion pits that eventually perforated. The pits contained phosphate-based deposits and were a consequence of this high localized concentration of phosphate (plus the presence of some iron, which acted as a reactant) causing acid attack. The corrosive attack was, in turn, traced back to a combination of causative problems, including ... 

Novel oxygen scavengers and polymer-based deposit control programs hardly figure in the operation of these large boilers because the treatment regimen is often simply hydrazine and ammonia. 

Halogen-Based Deposition. Diamond growth also occurs in several halogen-based reactions such as ... 

Ammonium bifluoride, when used at 0.5%, is also useful in assisting the removal of magnetite-based deposits. Add 2 to 3% thiourea where copper is present. The use of excess thiourea [CS(NH2>2] complexes dissolved copper and prevents it from plating out on steel surfaces and causing an equivalent amount of iron to dissolve. The heat exchanger must be thoroughly flushed out to remove all traces of copper and also inspected. 

The most common type of fouling is the precipitation of solid deposits in a fluid on the heat transfer surfaces. A layer of calcium-based deposits forms after prolonged use on the surfaces at which boiling occurs, similar to what can be observed on the inner surface of a kettle. To avoid this potential problem, water in process plants is treated to remove its solid content. 

Inkjet printing is a drop-by-drop technique. Patterns are built on the substrate through the assembly of individual drops. This has very important implications on printed electronics, and indeed, all the major concerns preventing successful commercialization of inkjet printing in printed electronics are related to the influence of the drop-based deposition. The major concerns with printed electronics based on inkjet are summarized below. 

Rumynskaya, I. G.. Study of intramolecular hydrogen bonding in phenolic Mannich bases. Deposited doc., 1981, VINITI 4213 81, 2.34 Chem. Ahsir.. 98,. 34145, 1983. 

E., and Maksumova, K. G Fungicidal activity of. some Mannich bases. Deposited doc,. 1975 VINITI 2082-75 Chem. Ahsir.. 87. 112830, 1977. 

Triaminopyrimidin-2-ol sulfate (2.84 g, 12 mmol), formamide (35 mL) and 98% formic acid (0.85 mL, 22 mmol) were heated in a bomb tube at 160 °C for 3 h. Upon cooling the crystalline free base deposited yield 1.67g (93%). 

Many deposits, including those of the Kalahari, contain manganese carbonates, and most other land-based deposits are thought to have originally had a large proportion of the manganese in carbonates. These phases are usually described as rhodochrosite, but microprobe analyses show the presence of considerable calcium. 

A Ni cathode that has become deactivated by impurity deposition or supposed H sorption under conditions of cathodic polarization can be activated (177) by electrodeposition of Mo species from added molybdate in solution, as found in a similar way with Co. The in situ activation is ascribed to formation of a spongy Mo-base deposit ( MoO) on the Ni during the first day of continuous water electrolysis. 

Cepak, V.M. and Martin, C.R. Preparation of polymeric micro- and nanostmctures using a template-based deposition method. Chem. Mater. 11, 1363-1367, 1999. 

Secondary-ion mass spectrometry (SIMS) of a thin layer of nucleic acid bases deposited on a silver foil under bombardment with Ar ions at 3 kV gives intense pseudomolecular ions [M H] but practically no simple bond cleavage fragments. Another new technique is that of (pulsed) laser induced desorption (LD). When applied to nucleotide bases such as cytosine or adenine (266 nm, quadruplet neodymium laser or 347 nm, ruby laser) the technique has good detection limits, particularly for ions with a short lifetime (up to 100 nsec). The technique makes use of a time-of-flight instrument and is utilized in both modes, positive (PI) and negative ions (NI). Both bases exhibit an intense [BH]" ion. These results are similar to those obtained by Cf plasma desorption (PD). 

At present it is felt that in this context, a fundamentally important recent advance in the silicon-based semiconductor industry is the development of copper interconnects on chips. Tliis new technology replaces aluminum or aluminum alloy (e.g., Al-Cu) conductors produced via vacuum-based deposition techniques with copper conductors themselves produced through electroless and/or electrodeposition. Specifically, vacuum-based deposition techniques include physical vapor deposition (PVD) and chemical vapor deposition (CVD). 

High-energy charged particles, inherent to plasma-based deposition tech-niqnes (e.g., spnttering) and detrimental for the organic surfaces, are avoided. 

---