Most of the humidity sensors practically used are based on the change in electrical properties of polymers or ceramics with humidity. They are either resistive-type or capacitive-type sensors. Various chemical modifications of polymeric materials have been utilized to improve the properties of sensors such as sensitivity, hysteresis, long-term stability, durability in unfavorable atmospheres such as dewdrops or vapors of volatile organic compounds (VOC), etc. This paper overviews the novel methods of chemical modification which have been proposed by the authors.

For the purpose of improving the Li charge/discharge cycle performance of less graphitezed carbon for the anode of Li-ion secondary batteries, the active material was made into C/C composite. A carbon fiber felt prepared at lower temperatures were impregnated with epoxy resin and pyrolyzed at a desired temperature. The SEM picture of the C/C composite thus obtained showed that each individual fiber was bound together by the carbon formed by pyrolysis. The charge/discharge cycle test was performed in propylene carbonate containing 1 M (M=mol dm⁻³) LiClO₄. It was found that the cycleability was improved remarkably for the C/C composite.

The anodic dissolution mechanism of Fe-Ni alloy was investigated by an electrochemical impedance spectroscopy (EIS). The Fe (II) and Ni(II) dissolved from Fe-Ni alloy electrode were detected simultaneously during the polarization curve measurement by a channel flow electrode system. The preferential dissolution of Fe (II) was observed at low anodic potentials, and the dissolution rate of Fe(II) was controlled by Ni content significantly. Nyquist plot of electrochemical impedance of Fe-Ni alloy electrode shows an inductive semicircle and negative resistance. These unique loci were explained by the formation of adsorbed intermediates Fe(I)_ad and Ni(I)_ad. The numerical simulation was performed for the experimental results of polarization curves, dissolution currents of Fe (II) and Ni(II) and electrochemical impedance responses. The dissolution mechanism was discussed on the basis of the kinetic parameters obtained by the simulation.

Deposition behavior of electroless Co-B and Co-Fe-B were investigated with respect to the structural and magnetic properties of deposits, using the amorphous ribbon substrates. The catalytic activity sequence of amorphous ribbon electrode for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath without containing the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of substrates. The linearly step of the deposition rate was obtained against the deposition time. And also, the initial deposition potential may determine the structural and magnetic properties of the deposit with thickness of μm order.

Lambda-manganese dioxide (λ-MnO₂), a spinel-type oxide, has lattice vacancies with a size equal to that of lithium ions, and incorporates lithium ions selectively from aqueous solutions. Oxide surfaces in water are hydroxylated by hydration, and the surface hydroxyl groups adsorb ions non-selectively by ion exchange, interfering with the selective incorporation of lithium ions. In this investigation, the surface hydroxyl groups on λ- MnO₂ were determined by the Grignard method as a measure of ion-exchange capacity. The surface hydroxyl site densities obtained were compared with the calculated value for the closest packing of hydroxyl groups, and the formation of hydroxyl groups was explained by neutralization of surface oxide ions by water.

Cell voltage shifts with change in partial pressure of oxygen gas in a cathode chamber of a phosphoric acid fuel cell being operated at 197°C and ambient conditions were investigated. An experimental equation on influence of the average oxygen partial pressure on the cell voltage was obtained as shown, ΔV =(0.09+ bi) log(P(O₂)/P(O₂)*), whereΔV represents the amounts of shifted cell voltage by unit of (V), i is the generating current density (A/cm²), P(O₂) is partial pressure (atm) of reacting oxygen gas, P(O₂)* is standard partial pressure (atm) of reacting oxygen gas, and b is a constant for the cell. Validity of the equation was confirmed for pressurized operated cell, such as the pressure range up to 7 atm of the air. Also, an experimental equation on influence of gas utilization on the cell voltage shifts was derived as, ΔV=(0.09+bi) log {(P(O₂)_(ent)/P(O₂)*)[2−(s/100)(1−P(O₂)_(ent)/P] /[2(1 + sP(O₂)_(ent)/100P] }, where ΔV represents an amount of the cell voltage change, P(O₂)_(ent) P) is a partial pressure (atm) of oxygen at the entrance of the cathode, s is a rate (%) of gas utilization at the cathode reaction, and P is the operating pressure (atm). Then, description of gas utilization rate is proved very important for presentation of cell performances.

Perovskite solid solutions of Pb(Zr_xTi_1−x)_1−y (Mg_1/3Nb_2/3)_yO₃ (PZTMN) without additives were prepared by wet-dry combination method in which the wet process was applied to the B-site cations (Zr⁴⁺, Ti⁴⁺, Mg²⁺, and Nb⁵⁺). Their mechanical quality factor (Q_M) was evaluated and compared with that of PZTMN prepared by the conventional dry method. Their values of Q_M are much higher than those for PZTMN prepared by the dry method. The improvement of Q_M is attributed to the improvement of sintered density. The wet-dry combination method is useful for the preparation of the solid solution having the high value of Q_M.