H-cell

Fig. 19. Self-discharge at ambient temperatures for a 35 A-h cell, NTS-2 prototype Sanyo Electric Co. cell.

Standard two-compartment H cell. The catholyte consisted of 3.25 M nitric acid and was separated by a medium-porosity sintered glass frit. Experiments were also carried out to determine if surface oxidation of hydrocarbon polymers could be obtained in an electrolyte consisting only of nitric acid. 

The standard voltage for a given cell is that measured when the current flow is essentially zero, all ions and molecules in solution are at a concentration of 1M, and all gases are at a pressure of 1 atm. To illustrate, consider the Zn-H+ cell. Let us suppose that the half-cells are set up in such a way that the concentrations of Zn2+ and H+ are both 1 M and the pressure of H2(g) is 1 atm. Under these conditions, the cell voltage at very low current flow is +0.762 V. This quantity is referred to as the standard voltage and is given die symbol fi°. 

Media flow rate, ml/h Retention time, t, h Cell Density, gd Substrate concentration (S), gd 1/5, 1/g - rA, Rate of substrate uptake, g/l.h l/-rA Ethanol concentration, gd... 

Operating near the washout point maximizes the production rate of cells. A feedback control system is needed to ensure that the limit is not exceeded. The easiest approach is to measure cell mass—e.g., by measuring turbidity— and to use the signal to control the flow rate. Figure 12.5 shows how cell mass varies as a function of t for the system of Examples 12.7 and 12.8. The minimum value for t is 2.05 h. Cell production is maximized at F=2.37h. 

Bacterium PHAs carbon source Culture time (h) Cell cone. (gH) PHAs cone. (gl-i) PHAs content (%) Productivity (gl-i h-i)... 

SXS measurements. (A) Single-crystal disk electrode, (B) Pt counter electrode, (C) Ag/AgCl reference electrode, (D) Mylar window, (E) electrolyte solution, (F) inlet for electrolyte solution, (G) outlet for electrolyte solution, (H) cell body, (1) micrometer, (J) electrode holder, (K) outer chamber, (b) Cell configuration for electrochemical measurement, (c) Cell configuration for SXRD measurement. (From Kondo et al., 2002, with permission from Elsevier.)... 

The cell doubling times go from less than 8 h to more than 18 h. Cells are also accumulating in G2. This is coincident with the gradual transition of String from a ubiquitously expressed product to a periodically expressed product. This transition can be largely attributed to regulation of String. 

Untreated BALB/c 3T3 cells and solvent-treated cells were used as negative controls. Positive controls were represented by cells treated with the well-known carcinogen 3-MCA (2.5 pg/mL). After 48 h, cells were replenished with fresh normal culture medium and maintained in culture for 4-6 weeks, with biweekly medium changes. Cells were then fixed with methanol, stained with 10% aqueous Giemsa, and scored for foci formation. In order to calculate the number of cells... 

Strain PHA Fermentation strategy Substrate Time (h) Cell concen- tration (g/D PHA concen- tration (g/D PHA content (%) Produc- tivity (g/l/h) Reference... 

Projected a prism spectrum across a trough containing cells. After 30 min cells had accumulated in the region between 410-515 nm after 3 h cells were found between 458 and 506 nm. 

A standard H-cell design was used next (Figure 3B), where the substrate was hung in about 5-10 mL of solution, and solutions were exchanged by draining and filling the cell [111, 112]. A major drawback was the large volumes of solution used, 10 mL/rinse, compared to the 0.1 mL/rinse presently used. In addition, potential... 

Fig. 3. Diagrams of electrochemical cells used in flow systems for thin film deposition by EC-ALE. A) First small thin layer flow cell (modeled after electrochemical liquid chromatography detectors). A gasket defined the area where the deposition was performed, and solutions were pumped in and out though the top plate. Reproduced by permission from ref. [ 110]. B) H-cell design where the samples were suspended in the solutions, and solutions were filled and drained from below. Reproduced by permission from ref. [111]. C) Larger thin layer flow cell. This is very similar to that shown in 3A, except that the deposition area is larger and laminar flow is easier to develop because of the solution inlet and outlet designs. In addition, the opposite wall of the cell is a piece of ITO, used as the auxiliary electrode. It is transparent so the deposit can be monitored visually, and it provides an excellent current distribution. The reference electrode is incorporated right in the cell, as well. Adapted from ref. [113],...

There were some major problems with the H-cells, however, such as the need for 50-gallon drums to hold the resulting chemical waste, as 100 mL of solution was used each cycle. In addition, potential control was lost for the deposits each time the solution was drained to rinse the cell or exchange solutions, which can result in some deposit loss. 

At that time, the cycle program was also changed, so that cathodic UPD was used for deposition of both elements. Use of a pH 10 tellurite solution, TcO) instead of pH 2, shifted Te UPD to better coincide with that for Cd UPD. A program similar to that presently used for depositing CdTe with the thin-layer flow-cell is compared with the older program used with the H-cell, in Figure 17. 

As noted above, the deposits made with the H-cell design were thin, only about 0.4 ML/cycle. For a 200 cycle deposit, they appeared deep blue, the result of interference effects in the 30 nm thick film. With the new cycle program and large thin-layer flow-cell, the best deposits appeared gold in color, and ellipsometric measurement indicate they correspond to the deposition of very close to 1 ML/cycle. A study of the thickness as a function of the number of cycles is shown in Figure 18, where... 

Films of CdSe have been grown with the automated flow-cell systems, both using the H-cell [111] (Figure 3B), and recently with the large thin-layer cell (Figure 3C) [164], Comparisons of X-ray diffraction patterns (XRD) have suggested that in both cases,... 

The amorphous silicon tandem solar cells consisted of three n-i-p a-Si H cells grown by plasma-enhanced chemical vapor deposition (PECVD) [126]. The a-Si H cell area was 0.5 cm2. 

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