Celani, F

Di Gioacchino, D

Di Stefano, V

Mancini, A

Marini, P

Pace, S

Selvaggi, G A

Spallone, A

Tripodi, P

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L A B O R A T O R I  N A Z I O N A L I  D I  F R A S C A T I SIS – Pubblicazioni   LNF–98/007 (P)16 Marzo 1998A preliminary D/Pd loading study:anomalous resistivity transition effectF.Celani, A.Spallone, P.Tripodi, D. Di Gioacchino, G.A. Selvaggi (1), P.Marini,V. Di Stefano (2), S.Pace (3), A.Mancini (4)(1) Istituto Nazionale di Fisica Nucleare – L.N.F., via E.Fermi 40, 00044 Frascati.(2) EURESYS, via Lero 40, 00144 Roma(3) INFM – Dipartimento di Fisica, Università di Salerno, 84081 Salerno, Italy.(4) ORIM S.r.L., via Concordia 65, 62100 Macerata, ItalyAbstractSeveral tests has been performed trying to over–load (D/Pd> 0.8) a Pd wire withDeuterium by mean of electrolytic procedures.A proper elicoidal electrodes geometry has been adopted to provide opportune electricfields during the electrolysis and several picks up has been located along the wires to obtain aprofile of wire Deuterium concentration by mean the resistivity.Tests operated with high electric current (up to 1 A) flowing along the wire and lowelectrolytic voltage showed a D/Pd loading of 0.75 at maximum.Tests operated with high voltage (from 50 to 100 V) have showed in some cases anovercoming of D/Pd= 0.95. In these cases an anomalous effect of cyclical loading/deloadinghas been newly observed by this group.No average anomalous heat in excess (more than 15%) has been observed during thesetests.PACS.: 72.15.–v;   82.30.NrKey words: Deuterium, Palladium, Resistivity TransitionPresented at theIII Workshop on Cold Fusion, November 27–29, (1987), Asti, Italy— 2 —1 – INTRODUCTIONIt is common opinion, according many Researchers working on "Cold Fusion"experiments, that to observe heat in excess or anomalous nuclear products it is necessary tosaturate a metal matrix (as Pd) by Hydrogen isotopes (as Deuterium) 1).A peculiar study is in progress to determinate a reproducible procedure to reach this goal,trying to produce high D/Pd loading values using long thin Pd wires by mean of electrolysis.It is possible to determinate the D/Pd concentration of a sample from the known resistivityvs concentration curve (R/Ro vs D/Pd) 2,3) and observing the loading or deloading process trendon the time. Looking at this curve, the peak value (D/Pd=0.75 at R/Ro=2) must be largelyovercome if we wish to observe "Cold Fusion" phenomena. In addition, if we want to know(from the resistance measurement), in which side it is the peak of the sample concentration, weneed to leave the electrode deloading and observe its resistivity derivative on the time.Because in normal condition (NTP) a Pd sample absorbs D up to a D/Pd=0.67, it isnecessary to force the loading or operating at very high pressure (millions of Pa) or applying onthe electrode surface an electric field density as strong as to avoid deuterons to be outgoing.An other effect, well known as Coehn effect 4), to achieve extra high loading is to apply ahigh voltage gradient along the Pd electrode, moving most inner deuterons to cumulate on themost cathodic (MC) point of the wire (electromigration effect). Some Researchers 5) claim that,as peculiar issue of this effect, high electric currents inducted through the wire, should be ableto increase the loading value at the MC point as well as producing a wall effect to the desorbingdeuterons (confinement effect).This ideas are been the motivation of the following tests performed.2 – APPARATUS SET–UPA peculiar version of a electrolytic cooling flow calorimeter was projected and mountedby the group at Frascati Laboratory (named Twin project: similar devices are working at INFNFrascati Lab, made since 1996 and NHE Sapporo Lab made since 1997).A schematically view of the experimental apparatus is drawn in fig.1 and fig. 2; it isessentially composed by an electrolytic cell immersed in a vessel filled by water cooled by anexternal water constant flow circuit. The vessel is thermally insulated. The electrolytic cell iscomposed by a glass beaker filled of electrolytic solution (diluted LiOD+D2O 0.25 mM/lsolution) in which is immersed a teflon cylinder and around it two wires (Pd of 160 cm and Ptof 200 cm, diameter of both of 100 mm) are, in parallel way (2 cm separated), elicoidallyturned; a further Pt wire is turned between the anode and cathode wires and used as referenceelectrode and for thermal and electrolytic calibrations. Each wire is partitioned in several sectors(4 sectors into the solution and 1 in air) by 6 picks up read by a multimeter for resistancemeasurement. Temperature sensors (8 sensors of which 2 at the input/output vessel coolingflow) are located inside and outside the vessel for calorimetric measurement.The calorimetry efficiency is ranging from 79 to 92 % depending by the cooling flow(from 1.2 to 6.8 ml/s). The calorimetry sensitivity is better of 0.5 W (at low flow).— 3 —3 – LOADING TESTSAll the following tests have been performed operating at high cooling flow (6.5 ml/s) inorder to get loading measurements at about the same isothermal conditions (cell bath and roomtemperature are included between 18 and 22 ° C).After each test, the Pd wire is left to desorb spontaneously up to return to the initialresistance value (of R/Ro=1 at room temperature): this process is completed roughly in a week.3.1 – Electromigration testsTo check the effectively of the electromigration effect (EM) we performed some testsapplying a direct current generator to the bottom edges of the electrodes and connecting the topedges with a 10 Ohm resistor (initial Pd wire and Pt wire are both about 20 Ohm). In such away, most of the input current is flowing through the electrodes, producing a consistent voltagedrop along the wires, while the current flowing between the electrodes (electrolytic current) is asmall part of it. We operated in these conditions:– electromigration current of 250 mA;– electrolytic current of 20 mA;– input voltage of about 12 V (voltage drop along the wires roughly about 5 V);– cooling flow of 6.5 ml/s (cell temperature quite similar to the room temperature).In this test the cathode absorbed D up to D/Pd=0.75 in a few hours but this value had notovercome even after some days (fig. 3–A,B). The initial absorption speed of the MC sector(Pd_bottom–down) is quite higher than the less cathodic sector (LC: Pd_down–up), but bothsectors reach the same maximum concentration (D/Pd=0.8) showing similar shapes. Looking atthe fig. 3, the peak value of R/Ro=2.05 seems to be higher than that one expected (R/Ro=2),because at this current the wire temperature is increased roughly of a tenth of centigradedegrees.During this electrolysis the input current was increases up to 1 A but, after operatingtemperature correction (temperature increases because joule effect), the absorption value seemedto be not changed.We repeated this test several times (starting each time with the same fully deloaded Pdwire) reproducing the same values.3.2 – High voltage testsIn this case, the electrodes at the top edges, are electrically disconnected and a voltagegenerator is applied to the bottom edges points (ordinary electrolysis).We operated in these conditions:– input voltage of 50 V (voltage drop along the wires roughly about 2 V);– electrolytic current of about 100 mA;– cooling flow of 6.5 ml/s (cell temperature quite similar to the room temperature).In a few hours the loading peak is reached by both MC and LC (Less Cathodic) sectorsand after long time (many hours) the loading process, even if not in a stable way, produces highloading (up to D/Pd> 0.95). In fig. 4.A, it is possible to see the loading trend as the normalisedPd wire resistance in the time: during the loading the wire (MC and LC sectors have verysimilar behaviours) can load up to D/Pd>0.9 and deload down to D/Pd=0.75 in an autonomyway.— 4 —4 – LOADING ANOMALOUS RESULTSIf we study in more detail the plot of fig. 4.A, during one of some over–loading (fig.4.B), we can see a fast deloading effect occurring when the D/Pd concentration roughlyachieves the value of 0.95 (returning, in short time, about less than a few seconds, to 0.85value and slowly loading, tenth of minutes, again to 0.95 value). This effect (named "rampeffect") seems to occur several times in a cyclic way before disappearing after a strongdeloading.If we observe D/Pd loading along several days, we can record this effect several times. Infig. 5.A (as well as better in fig. 5.B where the time scale is enlarged), it is possible to observeagain this effect occurring in a very similar way.During the same test the input voltage was increased from 50 V to 100 V and this effectwas again observed after several hours (fig. 6).An interpretation of this effect can be related to an anomalous new phase transitionoccurring to the Pd–D lattice when the wire is over–saturated by absorbed Deuterium (we cancall this "gamma" phase to distinguish it by the known alpha and beta phase of Pd–H system).In example, Deuterons are cumulated into the Pd (increasing potential energy as well as anelastic mechanical strain) until the gamma phase is achieved and then suddenly over–saturatedDeuterons are released.An other explanation of this effect can be possible if we congetture that an anomalous heat(because nuclear reactions) occurs into the wire when the value D/Pd= 0.95 is achieved, in sucha way to highly increased the wire temperature bringing to a wire deloading (D/Pd= 0.85). Thiseffect seems to be in agreement with the considerations reported by Dr McKubre after studyingthe heat in excess correlated to resistance–concentration curve by several experiments [ref. 6and fig. 7]. Because this effect occurs in very short time, we have no way to record a relevant(average) heat in excess.In order to check this interpretation, similar tests with Hydrogen are in progress.This effect is reproducible even if the reproducibility is still quite low because it is noteasy to load the wire up to D/Pd> 0.9 (it seems to occur after long time of loading and almost ina spontaneous way).Finally, this effect has been already observed and reported by the Group 7) using adifferent experimental set–up and during a different motivated experiment.5 – CONCLUSIONSThese measurements give a strong indications about the procedure to achieve high D/Pdloading in Pd wire.It seems that a high electric field must be applied between electrodes (at least 50 V ofpotential must be applied) and the electrolytic current must be as low as possible (tenth of mA,at least after having achieved the resistance–loading peak).Electromigration effect, by alone, does not help to overcome the resistance–loading peak;may be it is useful to be applied after getting a high loading (a proper study is in progress).When the loading overcomes D/Pd=0.9 a "ramp effect" occurs preventing to increasefurtherly the loading. Perhaps, this "phase transition" is due to a local highly warming of the Pd— 5 —wire that can be in agreement with a sudden and short production of heat of the wire (the originof this heat could be nuclear instead of lattice mechanical forces and so Hydrogen comparingtests are required).In conclusion, if we do not discover a proper procedure to mantain steady the high D/Pdvalue and for long time the "eventual" heat produced, it will be very difficult to measure andmake useful this heat.REFERENCES(1) M. Fleishmann and S. Pons. J.Electroan.Chem. 261 (1989) 301.(2) B. Baranowski et al. Journal Less Common Metal 158 (1990) 347.(3) M. McKubre et al. In proc. Symp. on Hydrogen storage materials, batteries andelectrochemistry. Eds. D.A. Corrigan and S.Srinivasan, Electrochem Soc. Inc. (1992) p.269.(4) A. Coehn. Elektrochem. 35 (1929) 676.(5) G. Preparata. In proc.of 2nd Workshop on The loading of hydrogen/deuterium in metals,characterisation of materials and related phenomena. October 1995, Asti, Italy.(6) M. McKubre et al. "Loading, Calorimetric, and Nuclear Investigation of the D/PdSystem." In proceedings: Fourth International Conference on Cold Fusion, December 6–9, 1993, Lahaina, Maui, Hawaii. EPRI TR–104188–V1, Proceedings July 1994– 3412Hillview Avenue, Palo Alto, 94304 California (USA)(7) F.Celani, A.Spallone, P.Tripodi et al. "Deuterium overloading of palladium wires bymeans of high power ms pulsed electrolysis and electromigration: suggestions of a "phasetransition" and related excess heat." Physics Letters A, 214 (1996) 1–13.— 6 —FIG. 1 – Apparatus set–up:A) Inner vessel; the electrolytic cell is immersed in a cooling bath.B) Cooling system outside the vessel: the thermal bath is at room temperature.— 7 —FIG. 2 – Electrodes set–up (Pd cathode, Pt anode and Pt reference):A)  Electrode wires are turned around a teflon cylinder.B)  Cathode–anode electric scheme with voltage picks up.R/RoFIG. 3 – Electromigration tests:A)  Most cathodic sector (Pd bottom–down);B)  Less cathodic sector (Pd down–up).— 8 —(s)FIG. 4 – Electrodes high voltage test (50 V):A)  Most cathodic normalised resistance shows high loading;B)  A region time enlarged of previous plot shows details of high loading values achieved(D/Pd > 0.9).— 9 —FIG. 5 – Ramp effect occurs several times during the run:A)  Most cathodic sector shows the effect during a high loading;B)  Enlarged time region of previous plot: ramps for R/Ro between 1.6–>1.8.— 10 —(MC)(s)FIG. 6 – Ramp effect occurring about one day later after increasing electrolysis voltage from50 to 100 V. The effect is similar to the previous ones and it is ranging from 0.85 to0.95 D/Pd value.FIG. 7 – Experimental data of Pd–D normalised resistivity vs D/Pd at high loading (D/Pd>0.75) related to the heat in excess occurrence [as reported in ref. 5].

A preliminary D/Pd loading study : anomalous resistivity transition effect

A preliminary D/Pd loading study : anomalous resistivity transition effect

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