Showing papers by "DECHEMA published in 1996"
TL;DR: In this paper, the early stages of TiAl oxidation at 900°C and 1000°C in air have been investigated by transmission electron microscopy (TEM) and it revealed that at the beginning of oxidation, i.e., after 4 min, TiO2 and Al2O3 grow in a preferential orientation on the γ-TiAl substrate.
Abstract: The early stages of TiAl oxidation at 900°C and 1000°C in air have been investigated by transmission electron microscopy (TEM). The investigations revealed that at the beginning of oxidation, i.e., after 4 min, TiO2 and Al2O3 grow in a preferential orientation on the γ-TiAl substrate. After 4 h of oxidation an oxide scale structure can already be found similar to that known from long-term oxidation. In addition, besides α-Al2O3, the formation of a second aluminum oxide phase and of titanium nitrides is observed. The processes at the metal-oxide interface of oxidation in the early stages, consisting of a repeated cycle of Al2O3 formation, Al2O3 dissolution, outward migration of Al through the scale, and reprecipitation of Al2O3 in the outer scale, are described by a model. The four stages observed in the kinetics of TiAl oxidation are explained on the basis of the results obtained and the structure of the oxide scale.
109 citations
TL;DR: In this paper, an electrolytic cell separated into two compartments by placing a cation or anion exchange membrane between the cathode (carbon cloth and metal-modified carbon cloth) and the anode (Pt net), was used.
84 citations
TL;DR: In this article, the ion conductivity and permselectivity of conducting polymer polypyrrole in dependence of the oxidation state were investigated. But the results were limited to a two-compartment measurement cell.
79 citations
TL;DR: Ion conductivity and permselectivity measurements were carried out on free-standing membranes of the conducting polymer polypyrrole as mentioned in this paper, which was prepared by electropolymerization on a microporous gold sputtered polycarbonate foil and stabilized by a Teflon frame.
64 citations
TL;DR: There are a number of mechanisms of the conjoint action of flow and corrosion that result in four types of flow-induced corrosion: mass transport controlled corrosion, phase transport controlled, erosion corrosion, and cavitation corrosion as mentioned in this paper.
48 citations
TL;DR: A low-energy dechlorination technique has been applied to the detoxification of chlorinated hydrocarbons (CHCs) in aqueous solution as discussed by the authors, which achieves reduction by means of metal particles or copper-activated metal particles (Mg, Fe, Al, Zn).
Abstract: A low-energy dechlorination technique has been applied to the detoxification of chlorinated hydrocarbons (CHCs) in aqueous solution. This alternative to biological or physico-chemical decomposition methods achieves reduction by means of metal particles or copper-activated metal particles (Mg, Fe, Al, Zn). The paper presents data from two pilot studies, covering fundamental process design aspects. Experimental investigations of pilot study 1 were conducted in a laboratory-scale fixed bed reactor. In weak acidic or neutral medium (pH-range 4-7) proper process application resulted in very rapid removal of hexachlorocyclohexane concentration ({gamma}-BHC, lindane) from model wastewaters with up to 99.3% efficiency. During the course of reaction the main products formed are chloride and benzene, the by-product being small amounts of chlorobenzene. After employing different metals in the dechlorination reaction zinc proved to be the optimum reducing agent since it achieved the best space-time yield. Pilot study 2 dealt with a couple of screening reactions of various CHCs with zinc as the reducing agent, which were performed in the batch mode. Even volatile CHCs (chloroform, 1,1,1-trichloroethane) could be completely dechlorinated by forming the corresponding hydrocarbons (methane, ethane and ethene respectively). Pseudo-first order rate constants (k,s{sup {minus}1}) were determined to assess substrate reactivity with respect to possiblemore » process applications. Process design aspects, advantages and limitations are discussed. 27 refs., 9 figs., 4 tabs.« less
34 citations
TL;DR: In this paper, the authors describe reaction engineering fundamentals of the separation of organic air pollutants (volatile organic compounds) from waste gases using fixed-bacteria monocultures (biocatalysts) in a trickle-bed reactor.
Abstract: The paper describes some reaction engineering fundamentals of the separation of organic air pollutants (volatile organic compounds) from waste gases using fixed-bacteria monocultures (biocatalysts) in a trickle-bed reactor. In particular the influence of pollutant concentration and oxygen concentration are investigated. The separation efficiency of certain substances such as acetone and isopropanol depends strongly on the oxygen concentration. The results obtained can be described by a mathematical model based on the diffusion of oxygen into the biofilm (diffusion regime of the catalyst). The non-stationary operation of the reactor – interruption of the oxygen stream and strong fluctuation in the exhaust gas stream – showed that other components such as propionaldehyde and n-propanol could be eliminated for a certain time without oxygen. Propionic acid is formed.
31 citations
TL;DR: In this paper, a characterization of MCM-41 with respect to acidity and molecular sieve properties, with a view to using this mesoporous material in catalysis, is presented.
23 citations
Patent•
09 Jul 1996TL;DR: In this paper, a method of increasing the corrosion resistance of TiAl alloys involves transferring halogens or halogen-contg. from the gas or liquid phase at least onto the alloy surface.
Abstract: A method of increasing the corrosion resistance of TiAl alloys involves transferring halogens or halogen-contg. cpds. from the gas or liquid phase at least onto the alloy surface. Pref. transfer is effected by (a) PVD or CVD; (b) gas or liquid phase halogenation of one or more starting or alloying powders or mixing solid chlorine-contg. phases with the starting or alloying powder, when the alloy is produced by a powder metallurgical process; or (c) ion implantation of halogens into the alloy surface.
9 citations
Patent•
12 Oct 1996TL;DR: In this article, a method of increasing the corrosion resistance of TiAl alloys involves transferring halogens or halogen-contg. from the gas or liquid phase at least onto the alloy surface.
Abstract: A method of increasing the corrosion resistance of TiAl alloys involves transferring halogens or halogen-contg. cpds. from the gas or liquid phase at least onto the alloy surface. Pref. transfer is effected by (a) PVD or CVD; (b) gas or liquid phase halogenation of one or more starting or alloying powders or mixing solid chlorine-contg. phases with the starting or alloying powder, when the alloy is produced by a powder metallurgical process; or (c) ion implantation of halogens into the alloy surface.
9 citations
TL;DR: The use of electromembrane technology for aluminium plant waste water treatment and for a new type of acidic catalyst synthesis has been studied in this paper, where the four-compartment electrodialyzer with one cation exchange and two anion exchange membranes was used.
TL;DR: In this paper, historical trends in the fields of corrosion and corrosion protection in various institutions are analyzed. And the authors show that compared with large-scale industries, small and medium-sized industries have the greatest recourse to service organizations.
Abstract: Die Losung von Werkstoff- und Korrosionsproblemen der Klein-und Mittelstandischen Industrie ist eine vordringliche Aufgabe der Gesellschaft fur Korrosionsschutz (GfKORR). Hierzu werden die historischen Trends aufgezeigt und vorhandene Aktivitaten auf den Gebieten Korrosion und Korrosionsschutz in verschiedenen Institutionen analysiert. Es zeigt sich, das verglichen mit der Gros-industrie bei der Klein- und Mittelindustrie der groste Dienstleistungsbedarf existiert. Aus der Tatigkeit des Karl-Winnacker-Instituts der DECHEMA e.V. und der Bundesanstalt fur Materialforschung und -prufung werden Zahlen uber Art und Verteilung von Korrosionsprojekten angegeben. Hieraus ergeben sich Konsequenzen fur die zukunftige Arbeit der Gesellschaft, die insbesondere darin bestehen, einen produktions- und produktintegrierten Korrosionsschutz aufzubauen, der schon bei der Konzeption von Verfahren und Produkten vorgesehen wird. Diese Vorgehensweise sollte den additiven Korrosionsschutz, der erst wirksam wird, wenn das Schadensereignis eingetreten ist, ersetzen.
Corrosion problems in small and medium-sized companies - a challenge for Gesellschaft fur Korrosionsschutz
The Gesellschaft fur Korrosionsschutz (GfKORR) attaches high priority to solving problems related to materials and corrosion encountered in small and medium-sized firms. In this connection historical trends are presented and existing activity in the fields of corrosion and corrosion protection in various institutions is analysed. It is demonstrated that, compared with large-scale industries, small and medium-sized industries have the greatest recourse to service organizations. Statistics, derived from the work of the Karl-Winnacker-Institut and the Bundesanstalt fur Materialforschung und -prufung, indicate the types and the distribution of corrosion projects. Implications for the future work of the society are given. In particular this entails the promotion of production and product-integrated corrosion protection which is applicable during the developmental stage of processes and products. It is intended that this approach to problems should replace additive corrosion protection which only takes effect when the damage has occurred.
Patent•
21 Mar 1996TL;DR: Pillar-structured, porous transition metal cpds with suitable properties for use as an absorbent and as a redox catalyst are obtd. by intercalating transition metal CPds.
Abstract: Pillar-structured, porous transition metal cpds. with suitable properties for use as an absorbent and as a redox catalyst are obtd. by intercalating transition metal cpds. at 273-373 deg K with a neutral layer lattice using organic mols. and neutral inorganic polymers.
Patent•
27 Jun 1996TL;DR: In this paper, the suitability of an erionite-containing catalyst for the reforming process is demonstrated, and it is characterized by high values of octane numbers and low content of carinogenic benzene.
Abstract: Use of bifunctional Pt/Al2O3 catalysts in catalytic reforming units significantly improved production. During the past four decades the power of such catalyst systems has been continuously increased by the introduction of various catalyst modifications. Use of reforming catalysts containing zeolites permits combination of shape selectivity with the conventional reforming reaction. Here, the suitability of an erionite containing catalyst for the reforming processes is demonstrated. Gasolines produced with zeolite catalysts are characterised by high values of octane numbers and low content of carinogenic benzene.
Patent•
22 Feb 1996TL;DR: In this article, a cyanide free electrolyte containing a small amount of heavy metal salt such as Pb, Th, In, Cd, and/or Sn salts is used for zinc electrolytic recovery.
Abstract: Zinc electrolytic recovery is effected using a cyanide free electrolyte containing a small amount of heavy metal salt such as Pb, Th, In, Cd, and/or Sn salts.
01 Jan 1996
TL;DR: The VDI-Kolloquium „Biologische abluftreinigung“ in Heidelberg and the Tagung „Abluft-reinigenung in Innsbruck" in 1994 as discussed by the authors have also been held.
Abstract: Die biologische Abluftreinigung findet immer breitere Anwendung in verschiedenen Industriezweigen. Dieses zeigten das VDI-Kolloquium “Biologische Abluftreinigung“ in Heidelberg und die Tagung “Abluftreinigung“ in Innsbruck sowie die VDI-Richtlinien Biofilter (1991) und Biowascher (1994). Wesentliche Apparate sind das Biofilter und der Biorieselbettreaktor, die mit fixierten Bakterien arbeiten, und Biowascher, die mit suspendierten Bakterien arbeiten. Die genannten Veranstaltungen ergaben, das der Biorieselbettreaktor zunehmend an Interesse gewinnt.