Materials Science Forum Vols. 544-545

Abstract: The nano-size PbTiO3 particles were prepared by sol-gel method and the effects of processing variables such as concentration of sol solution, catalyst, concentration of catalyst, calcination temperature and calcination process on particle size of PbTiO3 were analyzed. The condition for preparation of sol solution from the precursor is very critical to the size of PbTiO3 particle. At certain experimental conditions, the particles of 129nm, 213nm and 343nm were obtained. However, the particle size of commercialized PbTiO3 powder was 5㎛(5,000nm). The prepared nano-size PbTiO3 powder adsorbed more acetic acid and formic acid than the commercialized one; 1.5 times for acetic acid and 1.2 times for formic acid. Formic acid was preferentially adsorbed than acetic acid.

Abstract: For the synthesis of the nano-sized Ag metal particle, the sodium borohydride for the reducing agent was added into the aqueous solution of the AgNO3 with 3-mercapto-propionic acid as protective agent. Because the surface of nano-sized Ag metal particle was protected by the adsorbed 3-mercapto-propionic acid, the synthesis of the aqueous colloid system with high density became possible. The negative charge of carboxylate anion protect the aggregation of metal particles in the solution of high pH value (pH > 5), but the aggregation was occurred in the solution of low pH value (pH < 2). By changing the quantity of the agent of propionic acid and the pH value of solution, the particle size can be controlled optionally in the range of 50~200 nm.

Abstract: Biodegradable chitosan/clay nanocomposite membranes were prepared by solution casting method for the application of dehumidification. The cationic biopolymer, chitosan was intercalated into clay through cationic exchange and hydrogen bonding process. Diluted acetic acid was used as a solvent for dissolving and dispersing chitosan into clays. Chitosan was successfully intercalated into clay and it was confirmed by X-ray diffraction method. Thermal stability and the mechanical properties of the nanocomposites are characterized by TGA and Universal Testing Machine. Thermal stability and mechanical properties were enhanced by increasing clay contents in chitosan/clay nanocomposites. Gas permeation and water vapor permeation properties of the nanocomposites were measured by time-lag methods. Permeability of N2 gas and water vapor through chitosan/clay nanocomposite membranes decreased when the content of clay in the nanocomposite increased.

Abstract: Organic/inorganic hybrid materials synthesized from acrylic resin and silane-terminated colloidal silica(CS). The silane-terminated CS was prepared in variation with the kind of silane to CS. The CS treated with methyltrimethoxysilane(MTMS) and then treated with vinyl trimethoxysilane(VTMS), 3-glycidoxypropyltrimethoxysilane(ATMS) or 3-methacyloxypropyl trimethoxysialne(ETMS) by sol-gel method, respectively. The variation of silane-terminated CS and acrylic resin were hybridized by thermal-polymerization. Thin films of organic/inorganic hybrid materials were prepared using spin coater on the glass and aluminum sheets. Their contact angle, surface electric resistivity and thermal resistance improved with the amount of silaneterminated CS. The contact angle and surface electric resistivity of hybrid thin film with VTMS were enhanced. The surface of hybrid thin film with VTMS was homogeneous through FE-SEM.

Abstract: Two kinds of colloidal silica(CS)/silane sol solutions were prepared. Two sol solutions are involved with the kinds of silane such as methyltrimethoxysilane(MTMS) and
-Glycidoxypropyl trimethoxysilane(ETMS) using LS CS. MTMS was added to two sol solutions. Whether ETMS was added or not, two kinds of sol solutions were synthesized. Using two kinds of sol solutions, sol-gel coating films were formed on glass substrates via dip-coating process. Here, seasoning effect of for enhancing properties of sol-gel coating layer on glass was investigated while such sol-gel solutions were left for 7days. Also, their properties such as surface free energy, roughness, thermal property, potential hardness and elastic portion were characterized in order to understand the effect of addition of ETMS. In this case of LS/MTMS sol, the coating film had low surface free energy and more enhanced flat surface than that of the case of LS/MTMS/ETMS sol. ETMS forms hydrophilic hydroxyl group in sol solution, then surface free energy of LS/MTMS/ETMS coating film increased. In the beginning of reaction sol solution seemed to be unstable, but 4days later their coating film properties such as surface free energy and roughness enhanced. The elastic portion of coating films obtained from LS/MTMS/ETMS sol increased with addition of ETMS, but thermal stability decreased.

Abstract: Color sol was fabricated and coated it on glass substrate using sol-gel method. Silicate sol prepared by the use of commercially available tetraethoxysilane(TEOS), tetramethoxysilane (TMOS), methoxysilane(MTSO), phenytrimethoxysilane(PTMS) as a raw material of alkoxysilane family, and C.I. solvent red 122 and C.I. solvent yellow 82 as a organic dye, and C.I. pigment blue 28 and C.I. pigment red 26 as a pigment. Colored thin films were fabricated with changing the withdrawal speed by dip coating method, and heat treatment at 100~400°C. The visible light transmittance of colored thin film was measured with UV/VIS spectrophotometer, the surface hardness measured by pencil test, the surface turbidity measured by haze meter, and the film thickness was measureded by Alpha-step surface profiler.

Abstract: This work examined the mechanical properties of alumina that can directly be enhanced by ratio of nano sized alumina powders additives to micro size alumina powders (n/m ratio). These new materials have mechanical properties that are strongly grain size dependent and often significantly different from those of their coarser grained counter parts. The mechanical characteristics of samples were observed by using the indentation test system. This data shows that the relative density for the sample is increased with increasing Meyer hardness.

Abstract: TiC-based cermets attract much attention because of their excellent wear-resistance, high hardness at high temperature, good chemical stability, superior thermal deformation resistance. Therefore, titanium carbide is mainly used for cutting tools, grinding wheels, coated cutting tips and coated steel tools. In this research, Fe-TiC composite materials were fabricated by spark plasma sintering (SPS) after mechanical alloying. TiH2 and graphite powders were used to synthesize TiC phase. In order to compare the properties of sintered materials using mixture powder (D’AE+TiH2+graphite), commercial TiC powder was mixed with Distaloy AE (D’AE) powder as a same mechanical alloying method. Then, the shape of each mixture powder (D’AE+TiH2+graphite, D’AE+TiC (commercial)) and sintering properties were compared. TiC phase was synthesized by self-propagating high-temperature synthesis (SHS) reaction during spark plasma sintering. It was confirmed by using X-ray diffraction (XRD). Energy dispersive spectrometry (EDS) and Scanning electron microscopy (SEM) were used to observe shape of mixture powders and also sintering properties were examined such as hardness, relative density. In case of sintered material for 10min holding time at 1373K after mechanical alloying for 1 hour with D’AE, TiH2 and graphite, it indicated higher hardness value 49HR-C than a case using D’AE and TiC powder.

Abstract: Recently, the micro-column has been intensively studied as a potential candidate for next-generation lithography with high-throughput capability. The micro-column has a simple structure with an electron emitter, micro-lenses, a double octupole deflector, and an Einzel lens. The structure and performance of the micro-column are dependent on the characteristics of the electron emitter. The electron emitter should have several prerequisites such as stable emission of electrons, high brightness and long lifetime. It is also necessary for the emitted electrons to have sufficiently low kinetic energy, which can be achieved by using a very sharp emission tip. In this work, we made an extremely sharp tip by electro-chemically etching the tungsten wire in 10 % KOH solution. From the Fowler-Nordheim plot, the effective radius of the tip was found to be as small as ~12 nm, which is consistent with the value measured by SEM. We also discovered that the stability of emission can be enhanced very much through thermal treatment of the tip end by irradiating the Nd:YAG laser pulse

Abstract: Indium Tin Oxide (ITO) films were deposited on nonalkali glass substrate by dc magnetron sputtering using high density ITO targets with different conductivitis. Depositions were carried out at total gas pressure (Ptot) of 0.6 Pa, substrate temperature (Ts) of RT, oxygen flow ratio [O2/(O2+Ar)] of 0 ~ 3.0 % and dc power of 100W. High conductivity target showed relatively high stability in electrical property with increasing target erosion ratio. Optimum O2 addition ratio to obtain the lowest resistivity was decreased with increasing target erosion ratio. High conductivity ITO target could lead to decrease in micro-nodule formation on the target surface because of high cooling. The decrease in resistivity was observed for the film annealed at H2 introduction or without O2 addition in vacuum, where could be attributed to increase in carrier density.