Metal oxide can be prepared by mineralization process of biopolymers like cellulose, starch, alginate, chitosan, chitin, carrageenan, dextran, DNA, pectin, collagen, gelatin, silk, lignin and white-egg. The formation of corresponding hybrid composite [metal oxide@biopolymer] allows mastering the morphology, porosity, composition and structure of metal oxide and also gives access to [metal oxide@carbon] composite upon carbonization of the biopolymer We briefly review the recent advances in this fields in order to show the diversity of the approaches and their adaptations to produce material with potential applications in catalysis, energy and environment.
The preparation by sol–gel like methods of organic–inorganic hybrid materials based on phosphonate coupling molecules is briefly reviewed, focussing on porous materials. The structure of the materials, the reactions involved and the variety of precursors and templates that have been used are discussed. The potential applications of porous phosphonate-based hybrid materials are also presented.
Conventionally, commercialized spherical silicone powders, such as silicone resin powder [INCI: POLYMETHYLSILSESQUIOXANE (PMSQ beads)] and silicone rubber powder [INCI: DIMETHICONE/VINYL DIMETHICONE CROSSPOLYMER (DVDC beads)], have been formulated into cosmetics for soft and smooth feeling. Due to the low crosslink density, silicone rubber powder shows soft touch and high oil absorption. However, it is too agglomerative to be formulated into powder foundation. In this work, we have developed the novel soft touch spherical silicone beads made from methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS), using a surfactant, cetyltrimethylammonium chloride (CTAC). The preparation procedure of the novel silicone beads requires only homogeneous mixing and includes no other complicated operations. The 29Si NMR and TG measurements indicate that DMDMS is randomly incorporated into the methylsiloxane network. The particle size of the beads can be controlled by the concentration of urea as well as by the stirring speed in the sol–gel reaction. By carefully adjusting these parameters, the size of the beads has been optimized for the use in make-up cosmetics. It was revealed by various evaluation measurements that the novel silicone beads exhibit unique characteristics, such as softness, low oil absorption, high transparency and light diffusion effects.
Multicarboxy (8, 16) functionalized cage silsesquioxanes were synthesized through the photochemical thiol-ene reaction of octavinylsilsesquioxane with 3-mercaptopropionic acid and mercaptosuccinic acid, respectively. These two cage precursors acted as ligands to coordinate with terbium ion (Tb3+) to obtain two novel hybrid luminescent materials, which exhibited fine luminescent properties and good thermal stabilities. Their morphologies were investigated by XRD, SAXS, SEM, TEM and DLS. And the results showed that self-assembly particle size of the hybrid complex with octacarboxyl cage was larger size than that of cage with 16 carboxyl groups.
A series of thioether-functionalized silsesquioxanes (SQs) was synthesized by radically initiated thiol-ene reactions of vinyl T10/T12 SQ cages with a variety of commercially available thiols. The objectives of this study were to develop model reactions as the basis for using the vinyl T10/12 compounds as novel crosslinking agents in the synthesis of new types of thiol-ene crosslinked polymers. A second motivation was to develop model compounds with controlled refractive indices and Abbe numbers as possibly modifiers of polymers used for a wide variety of optical and photonic applications. The reactions proceed under mild conditions over 24 h to give thioether SQs in high yields (>90%) and high purity without complex workup. The ease of synthesis coupled with the wide variety and availability of functionalized thiols provides a simple route to elaborating and functionalizing vinyl SQ cages. In addition, the resulting compounds exhibit refractive indices to 1.52 coupled with Abbe numbers to 51 due to the uniquely high electron density provided by the incorporated sulfur atoms, making them ideal compounds for use with optically transparent materials. In addition, cured forms of these compounds provide methods of raising the Abbe number of epoxy resins designed to index match fiberglass with the intent of making transparent fiberglass reinforced composites.
Alkoxy group-functionalized amorphous silica-based inorganic–organic hybrid materials were designed through polymer precursor route, in order to develop a novel route for the fabrication of microporous amorphous silica-based materials. Commercial perhydropolysilazane (PHPS) was chemically modified with alcohols (R-OH, R = n-C5H11OH, n-C10H21OH) at a PHPS (Si basis) to ROH molar ratio of 4/1, and subsequently oxidized to afford alkoxy group-functionalized amorphous silica by exposure to aqueous ammonia vapours at room temperature. Then, the oxidized materials were heat-treated at 600°C in air. Nitrogen sorption analysis revealed that micropore volume of the amorphous silica increased upon alkoxy group-functionalization prior to the heat treatment. As a result, higher micropore volume of 0.204 cm3/g was achieved, with a specific surface area of 387 m2/g for the PHPS-derived amorphous silica chemically modified with n-C10H21OH at the Si/n-C10H21OH molar ratio of 2/1. The micropores evaluated by the SF method were in the size range of 0.43 to 1.6 nm, and the resulting micropore size distribution plot exhibited a peak at 0.43 nm. The in-situ formation of the microporosity was further studied by the simultaneous thermogravimetry-mass spectrometry analysis. The relationship between the number of carbon atoms in the alkoxy group, the evolution of gaseous species during the heat treatment and the resulting microporosity is discussed.
POSS derivatives were synthesized by the dehydrogenative reaction of octahydrosilsesquioxane with alcohols. The reaction with 2-methacryloyloxyethanol, 1-methacryloyloxy-2-propanol, and diphenyl methanol provided corresponding octaalkoxylated POSS derivatives. The reaction with ethylene glycol provided silica gel, while the reaction with 2,3-butanediol or pinacol provided polymers and oligomers, respectively. The product by the reaction of POSS with 2,2-butanediol was spin-coated on a silicon wafer and heated to provide a silica coating film with a pencil-hardness of 2H.
The use of polymer/inorganic material composites as controlled drug delivery carriers can be promising in the future for the reason of their excellent mechanical properties, drug loading efficiency and controlled release behavior. To develop a controlled drug release carrier, mineralized self-assembled polymeric nanocomposites (POCA nanocomposites) containing caffeic acid (CA) were prepared simply in the presence of Pluronic F-68 and β-cyclodextrin (β-CD) at different pH. The solution pH value greatly affected the morphological structure of nanocomposites. POCA7, POCA8 and POCA9 exhibited plate-shaped morphology, however, POCA10 showed only the sphere-like structure. The size of nanocomposites significantly decreased with increasing the solution pH value from 238 ± 19 nm (POCA7) to 61 ± 4 nm (POCA10). The amount of CA loaded on the nanocomposites was also considerably affected by the solution pH value. In addition, these nanocomposites exhibited slow, long-term and controlled release rate in DPBS, and the release rate of CA from the nanocomposites could be adjusted by varying the pH value of the release medium, implying that the POCA nanocomposites might be potentially applicable in controlled drug release systems.
A novel picolinate-iron(III) compound, Fe(C6H4NO2)2(OH) (1), was synthesized from an aqueous solution of a picolinate-iron(II) complex. Compound 1 was obtained by a thermal treatment of the picolinate-iron complex aqueous solution, whose pH was adjusted to 3–7, containing more than twice molar picolinic acid (Hpa) to Fe at 353 K for 72 h. When the iron aqueous solution in the presence of more than six times molar Hpa to Fe at pH 2–5 was heated, Fe(C6H4NO2)3·H2O (2) appeared. Millimeter-sized yellow-green single crystals of 2 could be obtained by the heat treatment of the picolinate-iron aqueous solution, whose pH was adjusted to 3, with Fe2+:Hpa = 1:10 at 373 K for 72 h. Formation mechanism of 1 and 2 was also discussed through investigations of relationship between synthesis conditions and products. Our approach opens a promising new route for preparation of precursors for synthesis of high functional ceramics and development of new organic–inorganic hybrids.
The B(C6F5)3 catalyzed Piers-Rubinsztajn (oxysilylation) reaction of the cubic symmetry Q-cage [(HMe2SiOSiO1.5)8] with ethoxysilanes in hexane forms microporous 3-D networks coincident with ethane evolution. Slow drying provides monoliths whereas fast drying provides powders. The reaction is most efficient if initiated at 60°C for 5 min and then allowed to progress at ambient. The products offer high specific surface areas [SSAs > 700 m2/g, e.g. with Si(OEt)4], with micropores of 0.6–2.0 nm, mesopores of 2–40 nm, total pore volumes ≈ 0.5 cc/g, and thermal stabilities to 320°C. Changes in reaction conditions (times, solvent volumes, catalyst concentrations) do not significantly change product properties pointing to rapid and complete reaction as evidenced by the near absence of residual Si–H under all conditions for 1:1: Si–H:Si–OEt ratios. RSi(OEt)3 gives similar 3-D microporous gels. Smaller R groups give higher SSAs than those with large R groups; however, R = n-octyl is not porous. Rigid, bridged compounds [(EtO)3Si–R–Si(OEt)3] (R = phenyl, biphenyl) offer high SSAs whereas flexible bridges [R = (CH2)2 or 8] give reduced SSAs. All materials were characterized by FTIR, TGA, XRD and BET. XRD studies show periodicities suggesting some long range ordering as might be expected for reactions with cubic symmetry Q8 cages. However, the fast reaction rates likely generate kinetic rather than thermodynamic products that cannot be expected to exhibit high degrees of ordering. Gel affinities for specific organics were studied showing some preferential ability to absorb specific solvents for example the 1:1 OHS:vinylSi(OEt)3 gels were more selective for toluene than the 1:1 OHS:TEOS gels.
Azido-group functionalized, hierarchically organized meso-/macroporous silica gels have been prepared through co-condensation of tetrakis(2-hydroxyethyl)orthosilicate with chloromethyltrimethoxysilane or 3-(chloropropyl)-triethoxysilane and subsequent conversion of the chloro groups. Azido functionalities have been obtained by nucleophilic substitution of the surface-bound chloro moieties with NaN3 in N,N-dimethylformamide. A strong dependence of the later azide density (N3 groups nm−2) in the final material on the reaction conditions, such as temperature and time, but also on the spacer length (methylene versus propyl) of the organofunctional silane has been observed. In principle, the nucleophilic substitution benefits from higher reaction temperatures and times. However, while γ-azido groups seem to be stable over a wide range of reaction temperatures and longer reaction times, α-azido moieties tend to decompose at temperatures above 60°C. The structural features of the monolithic gels and the azide functionalities on the surface were determined by IR-ATR-spectroscopy, elemental analyses, N2-sorption analyses, small angle X-ray scattering and transmission electron microscopy.
Sol–gel synthesis of macroporous polymethylsilsesquioxane (PMSQ) monoliths has been successful over the past decade, and applications to separation media have been investigated. However, the control of mesopores to tailor hierarchical porosity, which is promising for improvement of the separation efficiency, remains challenging. In particular, an independent control of meso- and macropores has not been achieved in PMSQ. Herein we present a method to synthesize PMSQ monoliths with well-defined macropores and controlled mesostructure (pore size ranging from 10 to 60 nm, total pore volume from 0.2 to 0.6 cm3 g−1) via sol–gel accompanied by phase separation. Different Pluronic-type nonionic surfactants were used to control phase separation of the hydrophobic PMSQ network in aqueous media. Due to different packing density of the colloidal PMSQ constituents in the continuous skeletons in the micrometer-scale (termed as macropore skeletons) and their rearrangements through the hydrothermal post-treatment under basic conditions, mesopore characteristics have been successfully controlled independently of the preformed macropore structure. Separation columns for high-performance liquid chromatography (HPLC) have been fabricated using the PMSQ monoliths, and acceptable separation performances in both the reversed-phase and normal-phase modes have been demonstrated due to the presence of both hydrophilic silanol groups and hydrophobic methyl groups.
Amorphous silica-based organoamine-functionalized hybrid materials were designed through polymer-derived ceramics (PDCs) route, in order to selectively transport CO2. Silicon-based perhydropolysilazane (PHPS) polymer was chemically modified with an alkylamino silane derivative, and subsequently oxidized in air at room temperature to afford organoamine-functionalized silica. The effect of the organoamine functionalization in the powdered sample as well as for the membrane is discussed with regard to the pure PHPS-derived amorphous silica.
Hybrid organic–inorganic materials provide the opportunity for combining organic chromophores into inorganic networks. The resulting hybrids can be used for numerous optical, biomedical and nanotechnology applications. Hybrid organic–inorganic particles that absorb and fluoresce in visible or ultraviolet light are particularly useful for bio-imaging, sensors, and as a safe sun-screen. The organic component can be incorporated through physical entrapment or through covalent incorporation through siloxane linkages. By containment in the hybrid material, the performance lifetime of the chromophore can be extended significantly and environmental contamination by its leaching out can be reduced. In this study, silica particles containing 1 mol % dimethylaminonathyl-sulfonamide (dansyl) dyes were prepared by three different methods: 1) physical encapsulation inside a hollow silica particle, 2) covalent attachment of pendant chromophores through a single silyl group and 3) covalent attachment through two silyl groups. The influence of the mode of entrapment on the particles’ spectroscopic properties, the propensity of the chromophores to leach from the particles, and photochemical degradation of chromophores were determined for the three classes of hybrid materials.
Photosensitive TiO2 gel films containing β-diketones and monomers with unsaturated hydrocarbons exhibit photosensitivity and can be patterned by photolithography. Photosensitive TiO2 gel films containing dibenzoylmethane (DBM) and methacrylic acid (MA) were prepared by the sol–gel method. The photoreactions of the gel films under ultraviolet (UV) light were investigated by UV–Vis, infrared, Raman, nuclear magnetic resonance, and X-ray absorption fine structure spectroscopic measurements. UV irradiation causes the chelate rings between titanium alkoxide and DBM or MA to decompose without drastic changes in the coordination number of Ti and in Ti–O distances, and it causes the formation of Ti–O–Ti networks. MA is photopolymerized by radicals resulting from the decomposition of DBM. These structural changes induced by UV irradiation cause the alcohol solubility of the materials to differ, and they allow fine patterns to be formed by etching.
Progress on two design approaches to patternable, low k dielectrics is described. These formulations are both print in negative tone and are based on polyhedral silsesquioxanes bearing benzocyclobutene moieties. The patternability was demonstrated and both materials have dielectric constants between 2.00–2.22 at optical frequencies. Coefficients of thermal expansion in the plane were found to be 6.0–13 ppm/K, and the materials have reduced moduli between 4–4.6 GPa.
Two kinds of Si–O–C(–H) particles having intrinsic photoluminescence (PL) spectra were prepared from silicone resin microspheres by heat treatment in a hydrogen atmosphere at 800 or 1100°C. The obtained particles were painted on a Si substrate using a binder, and ion-beam-luminescence spectra were observed under proton beam irradiation with an acceleration energy in the range of 1–3 MeV. Observed spectra had peaks at wavelength of 520–540 nm. These peak wavelengths were larger than those observed under UV light irradiation. The luminescence of H2 1100 (sample decarbonized at 1100°C) was bright, and that of H2 800 (sample decarbonized at 800°C) was faint. However, the intensity of luminescence decreased rapidly at an early stage of the beam irradiation. In air, a sharp luminescence band with a peak at 300 nm appeared together with the main emission with a peak in the range of 520–540 nm. The existence of the sharp band at 300 nm was apparent in the H2 800 spectra, whereas it appeared as a minor peak in the H2 1100 spectra in air.
Colloidally dispersed niobate nanosheets prepared by exfoliation of layered hexaniobate was modified by Ag nanoparticles by photodeposition, and the Ag-loaded colloidal niobate nanosheets showed photochromic response upon alternating irradiation of UV and visible light. Ag nanoparticles were successfully deposited onto the photocatalytically active niobate nanosheets in colloidal state through UV irradiation in the presence of Ag+ ions and ethanol. The deposited Ag nanoparticles exhibit a characteristic absorption band of the localized surface plasmon resonance (LSPR), which was also supported by TEM observations. Visible-light irradiation of the Ag-deposited niobate nanosheets caused reduction of the LSPR band intensity, which was recovered by subsequent UV irradiation. Band position also varied corresponding to the alternate visible and UV light irradiations. The reversible spectroscopic change was ascribed to the oxidative dissolution of the Ag nanoparticles located on the niobate nanosheets with visible-light irradiation and re-deposion of metallic Ag with the UV irradiation, as previously reported for the photochromic system of the composite of Ag nanoparticles and TiO2.
Polyoxometalate imides represent an area of materials chemistry research that recently has seen exciting exploration. Consisting of polyhedral metal-oxide clusters covalently coupled to organic ligands, they possess a combination of electrochemical activity and poly-anionic character hint. These characteristics suggest significant opportunities in the area solid-electrolytes, particularly if the typically good film forming characteristics of hybrid polymers can be accessed. The incorporation of a styryl group allows for hybrid polymers to be synthesized through free radical methods, producing hybrid materials that offer that an enormous number of opportunities to both materials scientists and engineers. This Note will document a concise route to quickly produce the readily polymerizable, styrylimido-hexamolybdate monomer from low cost precursor materials by leveraging recent advances and address some of the synthetic challenges found.
Photonic crystals with periodic variations in dielectric constants can theoretically exhibit forbidden gaps as a result of Bragg diffraction, thus prohibiting electromagnetic wave transmissions. The diffraction wavelengths are comparable to the lattice constants. In this study, diamond-type dielectric lattices with isotropic periodicities were identified as the perfect structure to open photonic band gaps for all crystal directions, and were then successfully processed. Stereolithographic additive manufacturing was customized to create photonic crystals with micro-sized diamond-like lattices. Photosensitive acrylic resin containing alumina nanoparticles was spread on a glass substrate with a mechanical knife edge. Cross-sectional layers, photo-polymerized by micro-pattern exposures, were laminated to create composite precursors. Next, dense components were obtained by dewaxing the precursors and subjecting them to sintering heat treatments. Structural defects consisting of point- and plane-cavities were introduced into the diamond photonic crystals by using computer-aided design, manufacture, and evaluation in order to study the characteristic resonance modes. These lattice misfits localize the electromagnetic waves strongly through multiple reflections, and wave amplifications enable transmission peak formations in the photonic band gaps according to the defect size. These photonic crystal resonators with micro-lattice patterns can be applied as wavelength filters in the terahertz frequency range. Terahertz waves in the far infrared range can be used in various types of novel sensors to detect dust on electric circuits, defects on material surfaces, cancer cells in human skin, and bacteria in vegetables.
Various kinds of optical responsive ceramic nanomaterials and films were successfully synthesized by environmental friendly green processes, such as hydrothermal/solvothermal process, mechanochemical doping process, oxygen plasma treatment process and a water molecular controlled-release solvothermal process (WCRSP). The composites combined the high-sensitive anion doped photocatalysts with up-conversion or long afterglow phosphors showed excellent deNOx photocatalytic activity under UV/ visible/NIR light irradiation, or even after turning off light irradiation. The mixed valence state tungsten based homogeneous nanomaterials possessed excellent IR light responsive properties, implied their potential applications as smart window materials and photothermal ablation cancer therapy materials. Significant contributions are expected for the development of optical responsive functional materials by green processes.
Molecules indicate a particular property by obeying a special characteristic in small space in some cases. It was discovered for a liquid phase such as decreasing the melting point in a nano-sized pore. A special phenomenon may also occur in the gas phase in a small space. To demonstrate this prediction, I have begun trying to fabricate a small space. A nano-sized hollow structure is very attractive for obtaining a small space. An inorganic template using inorganic particles is a facile technique to obtain hollow particles with various shapes, sizes, from nano to micron, and also different shell microstructures. This paper describes the sol–gel synthesis that is useful to form the shell structure of hollow particles and then how to control the particle structure using various templating routes. The hollow particles are used for the fabrication of air/solid composites with a controlled small space. These structure controls provide wide applications such as superior thermal insulation films, anti-corrosion films, and unexpected “easy-to-grip” volleyball coatings, etc. In addition to our achievements using hollow silica nanoparticles, the development of applications such as the lithium ion battery, biomedical products, catalysts, etc., will be outlined.
The solid state chemistry of mixed-metal oxides containing rare earths (4f elements) and 4d or 5d transition elements has attracted a great deal of interest, because these materials adopt a diverse range of structures and show a wide range of electronic properties due to 4f and 4d (or 5d) electrons. We have focused our attention on the structural chemistry and magnetic properties of perovskite-type oxides with the general formula AnLnMn−1O3n (A = Ca, Sr, Ba; Ln = rare earths; M = Ru, Ir; n = 1–4). Their structures are controlled by changing the ratio of the Ln and M ions, and peculiar magnetic properties and magnetic structures have been investigated by magnetic susceptibility, specific heat and neutron diffraction measurements.
Hierarchically porous materials are useful materials because characteristics of pores in various length scales (e.g., micro-, meso-, and macropores) can synergistically be integrated in a material. In this review, preparation of hierarchically porous materials by templating methods is summarized from the viewpoint of flexibilities of colloidal particles and colloidal assemblies as building blocks and templates, respectively. Low-dimensional colloidal particles, such as nanosheets and nanotubes, are used as flexible building blocks to form three-dimensional networks on templates with few defects. Because such colloidal particles can have inter- and intraparticle pores, their assembly on templates is effective to form pores in various length scales. Colloidal crystals, assemblies of uniform colloidal particles, have been used as templates of macroporous and hierarchically porous materials. Recently, the use of colloidal crystals as flexible templates is reported and attracts much attention. A stress due to confined growth of gold within the interstices of the colloidal crystals causes their structural changes, retaining their periodic structure, which direct one- or two-dimensional growth of gold. It is regarded as a novel concept for the preparation of hierarchical nanostructured materials with high crystallinity. The utilization of flexibilities of colloidal particles and colloidal assemblies is promising for the creation of hierarchically porous materials with unique nanostructures.
Unique photo-functionalities of luminescent Eu, Dy: SrAl2O4 glass ceramics with high transparency prepared by using the frozen sorbet technique are briefly reviewed. The crystal–glass composites have remarkable light-storage ability (e.g., charge-carrier trapping) based on the properties of SrAl2O4 crystals, and these provide characteristic photo-functionalities such as long-persistent luminescence and mechanoluminescence. In this review, the specific preparation of transparent SrAl2O4 glass composites using the frozen sorbet technique and their optical properties are described as novel light-storage materials for energy applications.
The article deals with the design of appropriate properties for a brick raw material in the production of frost resistant product. Additives based on bentonite and zeolite were added to the brick clay at doses ranging from 1 to 10%. The test samples were fired at 1055 C. The achieved results indicate that the initial material should not contain a high proportion of substances that increase the pore volume. Increased pore volume can cause not only the presence of organic matter and carbonates, but also an inappropriate particle size distribution of this initial material. When assessing the frost resistance a well known empirical relationship by Maage has been used. Authors conclude that this empirical relationship is only suitable for a limited number of brick products. In this case plays an important role the particle size distribution of the input raw materials material and the firing temperature. At the same time these products would need to be exposed to freeze-thaw cycles for long time periods before determining of the pore structure.
Brick clay from a locality Radobica, Central Slovakia, which was exploited for brick manufacturing in the past, was investigated for its possible reuse in the brick industry. The crystalline phases of the green sample were 48% of quartz, 37% of illite, 13%, of Na-feldspar and 2% of calcite. The measurements of Young's modulus of clay samples were performed during heating up to 1100°C and also at room temperature on samples preheated at temperatures from 100 to 1100°C. It was found during firing that 1) the physically bound water is released in 3 steps (up to 300°C) and reaches ∼2.5 wt %. The thermal expansion is decelerated by setting the crystal closer at low temperatures. Young's modulus increases in its values (∼36%) which is a result of the closer structure that is created via release of the physically bound water. 2) The mass loss during dehydroxylation (450–750°C) is ∼3 wt %. The superposition of dehydroxylation and α → β transformation of quartz creates a step ∼3% of the relative thermal expansion. Young's modulus slightly decreases in its values, the dehydroxylation does not influence this trend. 3) Above 900°C, the intensive contraction due to sintering is observed and a steep increase (250%) of Young's modulus takes place in this temperature interval. The irreversible changes of the Young's modulus measured at room temperature after firings at the temperatures from the interval 100–1100°C give a different picture. Dehydroxylation affects Young's modulus very significantly decreasing its values from 7.8 GPa (at 400°C) to 4.3 GPa (at 700°C). After dehydroxylation, the sintering increases Young's modulus. Since the porosity remains relatively high (∼30%) and a part of the glassy phase in the sample fired at 1100°C is relatively low (25%), the Young's modulus is low even after firing at 1100°C (9.3 GPa).
Blue-light excitable, green-light emitting Ba3(Sc1−xHox)4O9 phosphors were successfully synthesized in the single-phase form by a melt synthesis method for the first time. These phosphors show sharp green light emission under blue light (455 nm) excitation. The principal green light emission peak observed at 555 nm corresponds to the transition from 5F4 and 5S2 to the 5I8 energy level of Ho3+.
Boron, carbon and sulfur conjugated heteropoly tungsic-acid (BW-HPA, CW-HPA and SW-HPA) was synthesized using peroxo-iso-poly tungstic acid (W-IPA) and B2O3, CO2 and H2SO4 solutions, and the photochromic composite films were fabricated using these W-IPA, BW-HPA, CW-HPA and SW-HPA as filler and transparent urethane resin as matrix. All the composite films showed reversible photochromic properties (coloring and bleaching), and the spectra of all the composite films showed two broad absorptions with the peaks at 650 and 900 nm. The composite film using SW-HPA showed a high coloring speed and a low bleaching speed, and the composite films using BW-HPA and CW-HPA showed a slight high coloring speed and a high bleaching speed.
We have synthesized Mn4+-doped mixed tetragermanate phases in the Li2Ge4O9–LiNaGe4O9 system, i.e., Li(Li,Na)Ge4O9, by a glass-ceramic technique using stoichiometric precursor glasses, and have examined the effect of substitution of Na on their photoluminescence properties. The tetragermanate phases indicated clear red emission based on a 2E→4A2 transition, and the entire substitution resulting in an LiNaGe4O9 phase provided an improvement of quenching temperature for the emission. Furthermore, the LiNaGe4O9 phase synthesized by solid-state reaction showed a high internal quantum yield and red color purity, demonstrating it to be a possible candidate as a rare-earth-free red phosphor.
Waste foundry sand (WFS) collected from lost foam casting (LFC) is adopted to prepare low cost mullite-zirconia composites with the addition of alumina by reaction sintering. The mixture samples of WFS and alumina as well as samples containing only WFS are sintered from 1200 to 1600°C. Thermal shock behaviors are evaluated by cool water quenching test with temperature differentials (ΔT) between 200–1000°C and 1–4 repeated cycles for ΔT = 1000°C. The degree of damage with thermal shock severity is measured through dynamic elastic modulus E using the impulse excitation method. The result shows that mullite-zirconia composites can be successfully manufactured at 1500 and 1600°C, but the thermal shock (TS) resistance for composites sintered at 1600°C is not satisfied. The critical temperature gradient (ΔTc) is below 200°C, and after three TS cycles with ΔT = 1000°C, the E/E0 reduced to a nearly constant.
Porous corundum-mullite ceramics were prepared from Al(OH)3 and kaolinite gangue with different CaCO3 amount through an in-situ decomposition pore-forming technique. The effect of the amount of CaCO3 added (ACA) on the phase compositions and pore characteristics was investigated through X-ray diffractometer (XRD), scanning electron microscopy (SEM), and mercury porosimetry measurements, etc. It’s interesting that the granular mullite crystals are in the Al(OH)3 pseudomorphs but the needle-like mullite crystals are in the gangue pseudomorphs, and found that the ACA slightly affects the apparent porosity (AP), but strongly affects the formation of liquid phase, and then affects the secondary mullitization, microstructure, pore size distribution and crystal morphology. With an increase in ACA from 0 to 2.36 wt %, the increasing liquid phase make the rate of secondary mullitization increase markedly; when the ACA is 2.36 wt %, the secondary mullitization reaches the maximum; with a further increase of ACA to 3.54 wt %, the secondary mullitization decreases due to the formation of anorthite. With an increase in ACA from 0 to 3.54 wt %, the APs are in the range of 40.7–42.3%, whereas, the average pore size increases from 0.326 to 2.750 µm, and the crystal sizes of mullite in both pseudomorphs increase evidently.
Titanium plates covered with anodic oxide films with thicknesses of approximately 10 µm were embedded in a mixture of iron, graphite, and alumina powders, and then heated in the temperature range of 1073–1373 K for 3.6 ks in a nitrogen flow. We refer to this heat treatment method as “iron-powder pack (IPP) treatment”, and its ability to reduce the anodic oxide film was examined inclusive of a diffusion phenomenon of carbon and nitrogen into the film. From X-ray diffraction results, the film consisting of rutile and anosovite was gradually converted to titanium nitride with increasing heating temperature. The diffusion of carbon was also confirmed in the film after the IPP treatment. However, such a remarkable change was not achieved by heating without the powder mixture. This indicates that the powder mixture has an important role in reducing and carbonitriding the anodic oxide film. A porous structure in the film formed by anodic oxidation was retained regardless of the heating temperature in the IPP treatment. On the other hand, the peeling of the film from the titanium plate occurred through the IPP treatment at 1373 K. This would be caused by the accumulation of carbon monoxide gas, which was generated by the reduction of the oxide film.
Thermal conductive ceramic/resin composites are necessary for thermal management in order to improve the reliability of high-performance products in various industrial fields. The present study created composites consisting of silicon nitride (Si3N4) particles and epoxy resin by imbedding the particles into the resin matrix. Two common types of Si3N4 were applied in this work. α phase (α-Si3N4) and β phase (β-Si3N4) silicon nitride were loaded with epoxy resin. The effect of Si3N4 type on the thermal conductivity of composites was investigated by varying the Si3N4 particle content. For composites below 50 vol.% Si3N4, there was almost no difference in thermal conductivity between equivalently loaded α-Si3N4 or β-Si3N4/epoxy composites. However, for Si3N4 contents exceeding 50 vol.%, the β-Si3N4/epoxy composites showed higher thermal conductivities relative to the α-Si3N4/epoxy composite. The relative difference in thermal conductivities between the β-Si3N4 and α-Si3N4 epoxy composites (β-Si3N4/α-Si3N4) increased to 1.6 times at 68 vol.% of Si3N4 content.
The crystallographic features of the ferroelectric rhombohedral (FR) state in Ba(Ti1−xZrx)O3 (BTZ) have been investigated between 300 and 450 K mainly by transmission electron microscopy, with the help of the failure of Friedel’s law in electron diffraction. It was found that regions having 〈001〉PC- and 〈110〉PC-polarization components in the FR state were separately observed in dark field images, where the subscript PC denotes the paraelectric state. Based on the positional correspondence between regions with 〈001〉PC and 〈110〉PC components, the ferroelectric state for 0.11 ≤ x ≤ 0.17 could be explained as the nanometer-scale coexistence state consisting of fine FR and ferroelectric-tetragonal (FT) stripes, instead of the single FR state. In-situ observation also revealed that, when the temperature was lowered from the PC state, nanometer-scale polar (NP) regions with 〈001〉PC and 〈110〉PC components in the PC state were, respectively, coalesced into a banded structure with an average size of about 200 nm, and into fine stripes with that of about 30 nm. It is thus understood that the difference between the behaviors of the coalescences of NP regions with 〈001〉PC and 〈110〉PC components is directly associated with the appearances of both a complicated domain structure for x = 0.09 and the nanometer-scale coexistence state for 0.11 ≤ x ≤ 0.17.
The W-type barium hexagonal ferrites BaMg2−xCuxFe16O27, 0 ≤ x ≤ 1.4, were prepared by the ceramics process at 1270°C for 3 h, respectively. The X-ray diffraction (XRD) results revealed that the ferrites were single W-phase as Cu content (x) ≤0.6, while the second phase (α-Fe2O3) began to occur when Cu content (x) ≥0.8. Permanent magnetic properties of the magnets were measured by a B–H hysteresis curve measurements. The effects of the Cu content (x) on the permenant magnetic properties of the magnets were studied systematically. As a result, the remanence (Br) first increased with the increase of Cu content (x) and reached the maximum value of 402.4 mT at x = 0.6, then decreased when x continued to increase. Morever, the intrinsic coercivity (Hcj), magnetic induction coercivity (Hcb) and maximum energy product [(BH)max] decreased obviously with the x increased.
Optically transparent and stable sols of copper ion doped zinc sulfide (ZnS:Cu) nanoparticles were obtained by heating a mixture of ethylene glycol aqueous solution and sulfide precipitate at 348 K for 24 h. The sulfide precipitates containing zinc ions, copper ions and citrate ions were peptized in an aqueous solution of ethylene glycol having a 0.5 molar fraction of [Ethylene glycol]/([H2O]+[Ethylene glycol]). Photoluminescence characteristics and stability of the sols depended on the amount of citrate ions in the aqueous solution which was used for preparing sulfide precipitates. The citrate ions strongly affected the characteristics of the obtained sols with dispersion of the copper ion doped-ZnS nanoparticles. According to TG–DTA curves and N2 adsorption isotherms of the precipitated sulfides, the citrate ions in the aqueous solution containing zinc ions, copper ions coprecipitated in the sulfide precipitates formed by adding the sodium sulfide aq. The citrate ions played an important role for the peptization and the formation of stable sols.
This paper reports a microscopic electro-optic (EO) effect measurement system that is based on the Senarmont method and enables measurement of the EO coefficients (Kerr coefficients) of submillimeter-sized crystalline materials. In this study, an estimation of the electric field applied to the crystalline sample was performed with a finite-element method because the parallel plate electrodes were required to be on the same side of the sample surface. Reproducible values of the EO coefficients of submillimeter-sized (Pb,La)(Zr,Ti)O3 transparent ceramics were obtained only if this estimation was taken into account. This system will effectively increase the speed of searches for new EO materials.