Showing papers by "National Chemical Laboratory published in 1977"
TL;DR: In this article, a new technique for the preparation of CdS thin films by chemical bath deposition is described, which has many of the advantages of those made by the spray deposition method, such as the ease of coating large areas and simplicity of the process.
Abstract: A new technique for the preparation of CdS thin films by chemical bath deposition is described. The CdS films prepared by this method have many of the advantages of those made by the spray deposition method, such as the ease of coating large areas and simplicity of the process. The stoichiometry is easy to maintain in both these methods. The films are formed on rotating substrates from a bath containing cadmium salt in a complex form. Electrical, photoconducting, and optical properties such as I--V characteristics, decay of photoconductivity, spectral response of photoconductivity, and optical absorption were studied. Addition of cations like Ag, Cu. In, and Zn to the deposition bath makes the films amorphous. Such amorphous layers have a density of state of the order of 10/sup 19/--10/sup 20//cm/sup 3//eV near the Fermi level, as determined by photodecay and field effect measurements. The films produced are strong, adhering tightly to the substrates, show little or no degradation, and are photosensitive as deposited.
190 citations
TL;DR: In this paper, the copolymerization behavior of the systems (a) acrylic acid (AA)-acrylamide (AM) and (b) methacrylic acid (MA)-ACrylamides was studied in aqueous solution at 30°C as a function of pH.
Abstract: The copolymerization behaviour of the systems (a) acrylic acid (AA)-acrylamide (AM) and (b) methacrylic acid (MA)-acrylamide was studied in aqueous solution at 30°C as a function of pH. The copolymerization was carried out to high conversion (>10%) and the monomer reactivity ratios r1 for (AA or MA) and r2 (for AM) were computed using the Mayo-Lewis integrated equation. For the system (a), r1 reached its maximum value of 0,92 at pH 2, and its minimum of 0,33 at pH 6, thereafter increasing again. No systematic variation was found for r2. In system (b), r1 decreased sharply from a maximum of 2,8 at pH 4 to 0,19 at pH 6, then increasing to 0,39 as the pH was raised to 10. The r2 value showed a gradual increase from 0,2 at pH 4 to 0,57 at pH 9. Addition of NaCl (conc.: 1 mol/l) partially restored the value of r1 for both AA and MA to those at low pH. The variation of r1 of AA and MA nearly parallelled the homopolymerization rates of the respective monomers, with respect to pH. These variations were traced to the electrostatic repulsive interactions between the reactive species—ionized monomer and ionized polymeric radical—and hydrophobic interactions. Certain discrepancies in the trends of r1 and r2 were also noted.
66 citations
TL;DR: A redox reaction-driven transference system in which picrate anion, a lipophilic anions, moves not only against its concentration gradient but also against its electrochemical potential gradient through bulk organic solvent.
Abstract: SEVERAL studies1–3 have examined the concentrative transport4 of ions through bulk liquid membranes. The energy for the transport in these systems is the pH difference—the chemical potential difference of protons across the membrane. We describe here a redox reaction-driven transference system in which picrate anion, a lipophilic anion, moves not only against its concentration gradient but also against its electrochemical potential gradient through bulk organic solvent.
38 citations
TL;DR: In this article, the collision induced dissociation spectra of ions generated by ionization or fragmentation of various samples reveal at least five nondecomposing structures and carbon monoxide loss from the metastable ions are in agreement with the occurrence of a common reactive species.
Abstract: The collision induced dissociation spectra of ions generated by ionization or fragmentation of various samples reveal at least five non-decomposing structures. In contrast, the kinetic energy release measurements for the loss of carbon monoxide from the metastable ions are in agreement with the occurrence of a common reactive species. Isomerization into an ‘α,β-unsaturated aldehyde-like’ structure prior to fragmentation is proposed to accommodate these collision induced dissociation and mass analysed ion kinetic energy data. Some resuts suggest also that carbon monoxide loss from the phenol molecular ion may not occur via the cyclohexadienone tautomer.
31 citations
TL;DR: A phase diagram of the lanthanum-bismuth system, which includes five intermetallic compounds, is proposed in this article, and the powder pattern of LaBi 2 has been indexed as an orthorhombic system with unit cell parameters a = 4.737, b = 17.51 and c =4.564 A. The body-centred cubic cell of the γ phase of Lanthanum was found to be tetragonally deformed on forming a solid solution with bismuth.
Abstract: A phase diagram of the lanthanum-bismuth system, which includes five intermetallic compounds, is proposed. Only La 4 Bi 3 melts congruently at 1670 ± 30 ° C ; the other compounds La 2 Bi, La 5 Bi 3 , LaBi and LaBi 2 decompose at 1252 ± 10, 1350 ± 20, 1615 ± 15 and 932 ± 10 ° C , respectively. The structures of La 5 Bi 3 , La 4 Bi 3 and LaBi are already known to be of the Mn 5 Si 3 , anti-Th 3 P 4 and NaCl types, respectively. La 2 Bi has a structure of the La 2 Sb type with I 4 mmm symmetry. The powder pattern of LaBi 2 has been indexed as an orthorhombic system with unit cell parameters a = 4.737, b = 17.51 and c = 4.564 A . The body-centred cubic cell of the γ phase of lanthanum was found to be tetragonally deformed on forming a solid solution with bismuth.
26 citations
23 citations
TL;DR: In this article, the photoreversible reactions of 1,4-butanediol dicinnamylideneacetate (BCA) and its photocyclized compound (BCD) were studied.
Abstract: Photoreversible reactions of 1,4-butanediol dicinnamylideneacetate(BCA) and its photocyclized compound (BCD), the model compounds for poly(vinyl cinnamylideneacetate), were studied. They exhibited an excellent photoreversibility in a rigid medium at 77°K. The quantum yield of dimerization in the rigid medium is much larger than that in the solution and approximately equal to that in polymer film. Poly(vinyl esters) of substituted cinnamylideneacetic acids also showed photoreversibility to various extents, depending on the substituent. Poly(vinyl α-cyanocinnamylideneacetate) showed the best photoreversibility among the series, reflecting the least amount of side reaction upon the photodimerization.
23 citations
TL;DR: In this article, a crystallographic study has been made of solid solutions of the tetragonal defect chalcopyrites (14), CdGa2S4 and Cdga2Se4 and a complete solid solubility was observed between these two compounds.
Abstract: A crystallographic study has been made of solid solutions of the tetragonal defect chalcopyrites (14), CdGa2S4 and CdGa2Se4. The compositions may be represented by CdGa2S4(1−x)Se4x
wherex = 0.0, 0.25, 0.50, 0.75 and 1.0. A complete solid solubility was observed between these two compounds. Thea-axis values varied linearly with composition, whilstc-axis values initially showed a slower rise forx<0.5 and then a marked rapid rise with increasing selenium content. Single crystals were grown of these compositions by the chemical transport method. Optimum conditions required for the growth of the crystals have been established. The crystals of CdGa2S4 and CdGa2S3Se had the biggest face parallel to (001) plane whereas crystals of compounds CdGa2S2Se2, CdGa2SSe3 and CdGa2Se4 were triangular prisms with a face parallel to (112) plane and 〈110〉 as the growth axis. The parametersx, y andz for selenium position in CdGa2Se4 were obtained by comparing the calculated values ofF
2 factors with those obtained from observed intensities. The best match was found forx=y=0.25 andz=0.15.
22 citations
TL;DR: In this article, the authors studied the dielectric properties of In-O and oxidised In2O3 films at different temperatures and at various film thicknesses in the audio frequency region.
Abstract: Vacuum deposited blackish indium oxide films (In-O) as well as the oxidised films (In2O3) were studied for their a.c. behaviour at different temperatures and at various film thicknesses in the audio frequency region. e of In-O films was thickness dependent and also showed dielectric relaxation at lower frequencies due to the dipolar orientation arising from their non-stoichiometric nature. However at liquid nitrogen temperature region e was thickness independent similar to the oxidised films which neither showed any relaxation effect nor any thickness dependent e. The results have been discussed from the classical theory of dielectric polarisation.
22 citations
TL;DR: In this article, the stereospecific synthesis of chrysanthemic acid methyl ester from α-pinene via Favorskii ring contraction of an appropriately substituted α-bromocyclobutanone intermediate was described.
21 citations
TL;DR: In this paper, a series of compounds CdGa2S4(1−xSe4x) has been prepared and their single crystals grown by the chemical transport reaction method and optical absorption, spectral response, electrical conductivity and thermoelectric power measurements have been made.
Abstract: The compounds CdGa2S4 and CdGa2Se4 belong to the defect chalcopyrite (space group 1 ¯4) family. A series of compounds CdGa2S4(1−xSe4x has been prepared and their single crystals grown by the chemical transport reaction method. Optical absorption, spectral response, electrical conductivity and thermoelectric power measurements have been made. The optical absorption spectra revealed that the fundamental absorption edge varies with composition, from 2.2 to 3.25 eV. The plots (αħw)2 versus ħw revealed that these compounds are direct band gap materials, but plots of (αħw)1/2 versus ħw did not give convincing support to the presence of indirect transitions. The values of energy gaps were also deduced from spectral response (λmax) measurements and found to be in agreement with those deduced from optical absorption measurements. D.c. resistivity versus temperature studies revealed that, in spite of their large band gaps, these compounds exhibit intrinsic semiconduction above 250° C. The energy gap values matched with those obtained from other measurements. All samples were n-type and had a constant thermoelectric power ≈ 300 μV° C−1 in the temperature range 250 to 350° C. However, the thermal dependence of electrical conductivity and thermoelectric power indicated strong irreversibility with the thermal heating and cooling cycle. Such behaviour has been attributed to the diffusion of contact materials such Ga and In.
TL;DR: The effect of modifying the Al 2 O 3 with various bases or salts has been studied in this article, where the carbonium ion-rearrangements are significantly suppressed, and rearrangement to the allylic alcohols becomes the major pathway.
TL;DR: In this paper, a bisabolane-based tetrahydroγ-pyrone from the essential oil from the wood of Cedrus deodara Loud is described, which has been named deodarone, has been chemically correlated with the sesquiterpene ketone, atlantone.
TL;DR: In this paper, the authors investigated the effects of immersion time of the catalyst in tartaric acid solution for modification on the asymmetric activity of the modified catalyst in the hydrogenation of methyl acetoacetate.
Abstract: Effects of immersion time of the catalyst in tartaric acid solution for modification on the asymmetric activity of the modified catalyst were investigated in the hydrogenation of methyl acetoacetate. It was found that, in order to prepare highly asymmetrically active catalyst, the immersion of the catalyst for 69 hours on a hot water bath was necessary. Thus, when the catalyst immersed for 6 hours was used, the greatest asymmetric selectivity (optical yield=99%) was obtained in the hydrogenation in tetrahydrofuran and a small amount of formic acid.
TL;DR: In this article, a probable Langmuir-Hinshelwood (Hougen-Watson) model in the temperature range 605.5-636.5 °K has been proposed based on adsorption of n-butene controlling (single site).
TL;DR: In this article, the effects of additives on the asymmetric yield of methyl 3-hydroxybutyrate were examined in the hydrogenation of methyl acetoacetate using Ni-Pd-Kieselguhr catalyst modified with tartaric acid.
Abstract: Effects of additives on the asymmetric yield of methyl 3-hydroxybutyrate were examined in the hydrogenation of methyl acetoacetate using Ni-Pd-Kieselguhr catalyst modified with tartaric acid. Addition of unsaturated compounds such as dehydroacetic acid and diethyl maleate showed almost no effect on the asymmetric yield. Only when carboxylic acids having pKa values higher than that of tartaric acid such as formic acid, acetic acid, benzoic acid, and succinic acid were used as additives, great increase in asymmetric yield was observed.
TL;DR: In this article, the ring opening of cyclohexane and methylcyclopentane (MCP) catalyzed by a nickel-alumina catalyst was investigated at a hydrogen pressure of 10 atm, in the temperature range from 230 to 320 °C.
TL;DR: Isotope effect studies for the diffusion of Cd in silver single crystals are made using the isotope pair Cd 115m and Cd 109 in the temperature region 730 to 906 ° C.
Abstract: Isotope effect studies for the diffusion of Cd in silver single crystals are made using the isotope pair
Cd 115m and Cd 109 in the temperature region 730 to 906 ° C. The enhancement factor 'b' is
measured in dilute Ag-Cd alloy upto ≈ 3 at% cadmium at 860 and 924 ° C. The data from the isotope effect and
enhancement factor are combined to calculate the jump frequency ratios, using Howard and Manning's calculations. The correlation
factor measured from the isotope effect experiment varies from 0.781 ± 0.087 to 0.623 ± 0.051 between temperatures of
735 to 906 ° C. Values of 'b' at 860 and 924 ° C are found to be 9.19 and 13.69, respectively. These values are
consistent with the vacancy migration mechanism. Isotopieuntersuchungen fur die Diffusion von Cd in Silbereinkristallen werden unter
Verwendung des Isotopenpaares Cd 115m und Cd 109 im Temperaturbereich von 730 bis 906°
C durchgefuhrt. Der Verstarkungsfaktor " b" wird in verdunnten Ag-Cd-Legierungen bis zu
≈ 3 At% Kadmium bei 860 und 924 ° C gemessen. Die Ergebnisse des Isotopieeffekts und des
Versturkungsfaktors werden gemeinsam zur Berechnung der Sprungfrequenzverhaltnisse mittels des
Howard-Manning-Verfahrens benutzt. Der aus dem Isotopieeffekt gefundene Korrelationsfaktor andert sich im
Temperaturbereich 735 bis 906 ° C von 0,781 ± ; 0,087 auf 0,623 ± ; 0.051. Die Werte von " b"
betragen 9,19 und 13,69 bei 860 bzw. 924 ° C. Diese Werte stimmen mit der Vorstellung der Diffusion uber Einfachleerstellen
uberein.
TL;DR: In this paper, a classification of the adsorption integral equation in finite and infinite limit problems is made and a method of solution based on the theory of finite Hilbert transforms is proposed.
TL;DR: In this article, the diffusion coefficient of 59 Fe in silver single crystals is investigated in the temperature region 780 to 940 ° C. The diffusion coefficient, D=1.90 exp (−49.36/RT) cm 2 /s, agrees with the earlier work of Mullen.
Abstract: In the temperature region 780 to 940 ° C the diffusion of 59 Fe in silver single crystals is investigated. The diffusion coefficient, D=1.90 exp (−49.36/RT) cm 2 /s, agrees with the earlier work of Mullen. The calculations of the correlation factor fi for the Ag[BOND]Fe system using Mullen's results and from the model of LeClaire and the T m -model, further support the vacancy mechanism to be operative in this system. Die Diffusion von 59Fe in Silber-Einkristallen wird im Temperaturbereich von 780 bis 940° C untersucht. Der Diffusionskoeffizient, D=1,90 exp (−49,36/RT) cm 2 /s, stimmt mit dem in der fruheren Arbeit von Mullen uberein. Berechnungen des Korrelationsfaktors f i fur das Ag[BOND]Fe-System mit den Mullenschen Ergebnissen sowie den Modellen von LeClaire und dem T m -Modell bestatigen den Leerstellenmechanismus als in diesem System wirkenden Mechanismus.
TL;DR: In this article, the phase equilibria of some organic materials which are less soluble in water (such as phthalates and higher alcohols) were greatly affected by the salting-out effect of salinity, which is probably due to the effect of pH on the degree of dissociation of electrolytes and on the hydrolysis of esters.
TL;DR: In this article, the optical absorption spectra of the ternary thiogallate compounds CdGa2Se4 and Cdga2S4 were studied in the visible range of radiation.
TL;DR: In this article, the authors derived the polarographic current-voltage curves for electrode reactions with three parallel charge transfer processes coupled by two chemical reactions on the basis of the staeady-state assumption in the reaction layer.
TL;DR: In this article, a bicyclic sesquiterpene of a carbo-skeleton, derived from the essential oil from the wood of Credrus deodara loud, is reported.
TL;DR: A series of compounds with formula trans-(Ph3P)2Pt(CF:CF2)X were synthesized to study the effect of a trans group on the 19F resonance spectra of perfluorovinyl group as discussed by the authors.
TL;DR: In this paper, the quantitative estimation of ferulates in rice bran oil by high performance liquid chromatography (HPLC) was investigated, and it was found that operating conditions shown in Table-2, were optimum for the separation of ferulate from other components.
Abstract: An ultraviolet absorption spectroscopic method has been used generally for the determination of ferulate content in rice bran oil. However, the analytical accurate results are not obtainable, because of the presence of some substances interfering the above method. Moreover, another method using both TLC and ultraviolet spectroscopy takes a long time for the analysis. In this work, the quantitative estimation of ferulates in rice bran oil by high performance liquid chromatography (HPLC) was investigated. It was found that operating conditions shown in Table-2, were optimum for the separation of ferulate from other components in rice bran oil. The peak of separated ferulate in the chromatogram was measured, and the calibration curve of the relation between the weight of ferulate and peak area was used to calculate the f erulate content. In this case, β-sitosteryl ferulate was used as the external standard sample. Since the interfering substances for the ultraviolet spectroscopy were removed and the ferulates were separated by HPLC the results acquired by the method mentioned above are more accurate as compared with that were determined directly by ultraviolet spectroscopy. In addition, the analytical procedure takes less than 15 minutes in almost cases. It is apparent that the time needed for the analysis per one sample by HPLC is shorter than that by the method using both TLC and ultraviolet spectroscopy.
TL;DR: In this article, a new four-step thermochemical cycle based on calcium and iodine is proposed for the decomposition of water, and an evaluation of the thermal efficiency of the process based on the material and energy balances for a proposed flow sheet is also presented.