Addition Of Tetramethylammonium Hydroxide Research Articles

Effect of Chemicals and Slurry Particles on Chemical Mechamical Polishing of Polyimide

The purpose of this study was to investigate the effect of chemicals and particles on chemical mechanical polishing (CMP) of polyimide (PI). The effect of particle size and its surface area on both the removal rates and the surface roughness was investigated as a function of the slurry content upon the addition of various chemicals. The optimal particle content was measured for silica, ceria and alumina slurries in terms of the removal rate and surface roughness. The removal rate was highest when deionized (DI)-water-based alumina slurry was used. However, the greatest surface roughness was measured when ceria slurry was used rather than alumina. Alkaline chemicals were added to the slurry to enhance the removal rates of PI during CMP. The addition of Tetramethyl Ammonium Hydroxide (TMAH) and Potassium Hydroxide (KOH) to ceria slurry but not to alumina and silica slurries increased the removal rate significantly at higher pH values. The addition of ethylenediamine and the presoaking of PI in hot DI water did not increase the removal rate in alkaline-chemical-based slurries. The addition of surfactant resulted in a decrease of the removal rate to half of that determined without the addition of surfactant.

Elimination of the carbon build-up effect in the ETAAS analysis of low diluted serum samples using an in situ wet digestion with tetramethylammonium hydroxide. Application to aluminium determination

A simple and effective procedure to minimise the accumulation of carbonaceous residues inside the graphite tube during the electrothermal atomic absorption spectrometric (ETAAS) determination of aluminium in human serum is described. The procedure involves the addition of tetramethylammonium hydroxide (TMAH) to the injected samples to effect an in situ wet digestion of the serum proteins. Results obtained showed that the addition of 5 µl of 1 mol l−1 TMAH to each 15 µl sample injection allows the repeated analysis of over 200 serum samples (diluted 1 + 1 with a diluting solution containing 1 g l−1 K2Cr2O7, 0.5% v/v Triton X-100 and 0.2% v/v HNO3) with no evidence of a carbon build-up effect. Compared with the same ETAAS procedure without the addition of TMAH, a good improvement in repeatability, long-term precision and accuracy was achieved.

Influence of the addition of alkanolamines and tetramethylammonium hydroxide on the shape and size of zeolite-A particles

Influences of the addition of alkanolamines and alkylammonium hydroxide into the starting suspensions on the shape and the size of zeolite-A (NaAlSiO4·xH2O) particles were investigated by optical microscopy and liquid-state NMR measurements. Zeolite-A was prepared from a mixture of NaAlO2, Na2SiO3·9H2O, alkanolamine or alkylammonium hydroxide, and H2O by hydrothermal treatment. The addition of triethanolamine (TEA) into the starting suspension led to the enlargement of the particle size of the prepared zeolite-A, whereas the addition of tetramethylammonium hydroxide (TMAOH) decreased it. TEA was confirmed to coordinate to Al to form [N(C2H4O)3Al(OH)]− complex, decreasing the degree of supersaturation of free [Al(OH)4]− and inhibiting the excess nucleation of zeolite. On the other hand, the addition of TMAOH facilitated the dissolution of silica gel in the starting suspension, very probably due to its higher basic property, and increased the degree of supersaturation of Si species, which resulted in the decreases in the particle size.

The magnetic and structural properties of a series of lanthanum based transition metal perovskites

Fe-doped lanthanum–nickel perovskite was prepared using several methods based on co-precipitation and sol–gel technologies. A simple complexing-precipitation reaction, involving the addition of tetramethyl ammonium hydroxide to aqueous nitrate solutions, gave an oxy-hydroxide gel. On ageing this produced a single-phase perovskite product at low temperatures (about 1073 K) for LaNiO 3. However, the formation of the Fe-doped materials yielded a far more complex oxide system with three different perovskite phases being identified. This material was shown to exhibit super-paramagnetism. Mössbauer spectroscopy performed on Fe- and Eu-doped samples showed that all metal cations are trivalent. In agreement with previous work [A. Reller, T. Williams, Chem. in Britain (1989) 1227] it was found that the structure was a rhombohedrally distorted perovskite. Lattice parameters were determined accurately by Rietveld analysis. Mössbauer spectroscopy was used to monitor changes in the magnetic properties of these materials on addition of iron (between 5 and 100 metal mol%). Up to iron loadings of 30% the system exhibits only super-paramagnetic properties. Above this level there is a complex mixture of super-ferromagnetic and ferromagnetic components. Above 90% only ferromagnetic properties are displayed. These observations are not due to the precipitation of spinel-type phases but, rather, have been rationalised in terms of the precipitation of new distorted perovskite phases and electronic modifications dominated by local interactions and long range co-operative effects between these local centres.

Characterization of impurities in pulp and paper products using pyrolysis—gas chromatography/mass spectrometry, including direct methylation

The organic impurities found in pulps and paper products and as deposits on equipment in pulp and paper mills can be rapidly characterized using pyrolysis—gas chromatography/ mass spectrometry (Py—GC/MS). Frequent problems arise from resin and sizing agents, which contain polar compounds. These products, which have difficulty in passing through the Py—GC system, can be methylated directly on the pyrolysis filament by the addition of tetramethylammonium hydroxide. The possibility of distinguishing between wood resin and different sizing agents including rosin, fortified rosin and alkylketene dimers, is demonstrated. Some examples in which the described technique is used for characterizing impurities are also given.