Fabrication, thermal stability and mechanical properties of novel composite hardmetals obtained by solid-state reaction and hot-pressing sintering

A novel cemented carbides (W0.7Al0.3)C-0.65-Co with different cobalt contents were prepared by solid-state reaction and hot-pressing technique. Hot-pressing technique as a novel technique was performed to fabricate the bulk bodies of the hard alloys. The novel cemented carbides have superior mechanical properties compared with WC-Co. The density, operate cost of the novel material were lower than WC-Co system. The novel materials were easy to process nanoscale sintering and get the rounded particles in the bulk materials. There is almost no eta-phase in the (W0.7Al0.3)C-0.65-Co cemented carbides system although the carbon deficient get the astonished 35% value.

Alternating Copolymerization of Cyclohexene Oxide and Carbon Dioxide Catalyzed by Noncyclopentadienyl Rare-Earth Metal Bis(alkyl) Complexes

The syntheses of several dialkyl complexes based on rare-earth metal were described. Three beta-diimine compounds with varying N-aryl substituents (HL1 = (2-CH3O(C6H4))N=C(CH3)CH=C(CH3)NH(2-CH3O(C6H4)), HL2 = (2,4,6-(CH3)(3) (C6H2))N=C(CH3)CH=C(CH3)NH(2,4,6-(CH3)(3)(C6H2)), HL3 = PhN=C(CH3)CH(CH3) NHPh) were treated with Ln(CH2SiMe3)(3)(THF)(2) to give dialkyl complexes L(1)Ln (CH2SiMe3)(2) (Ln = Y (1a), Lu (1b), Sc (1c)), L(2)Ln(CH2SiMe3)(2)(THF) (Ln = Y (2a), Lu (2b)), and (LLu)-Lu-3(CH2SiMe3)(2)(THF) (3). All these complexes were applied to the copolymerization of cyclohexene oxide (CHO) and carbon dioxide as single-component catalysts.

Isoprene polymerization with indolide-imine supported rare-earth metal alkyl and amidinate complexes

Reaction of 7-{(N-2,6-R)iminomethyl)}lindole (HL1, R = dimethylphenyl; HL2, R = diisopropylphenyl) and rare-earth metal tris(alkyl)s, Ln(CH2SiMe3)(3)(THF)(2), generated new rare-earth metal bis(alkyl) complexes LLn(CH2SiMe3)(2)(THF) [L = L-1: Ln = Lu. (1a), Sc (1b); L = L-2 : Ln = Lu (3a), Se (3b)] and mono(alkyl) complexes L-2 Lu-2(CH2SiMe3) (4a). Treatment of alkyl complexes 1a and 4a with N,N'-diisopropylcarbodiimide afforded the corresponding amidinates (LLu)-Lu-1{iPr(2)NC(CH2SiMe3) NiPr2}(2) (2a) and L-2 Lu-2{iPr(2)NC(CH2SiMe3)NiPr2} (5a), respectively.

Density functional study on the reaction mechanism of palladium-catalyzed addition of cyanoboranes to Alkynes

The B3LYP hybrid density functional method has been carried Out to Study theoretically the mechanisin of Pd(0)-catalyzed alkyne cyanoboration reaction. Both the intermolecular and intramolecular alkyne cyanoboration reactions were studied. For each reaction, three paths were proposed. In path A of each reaction, the first step is B-CN bond oxidative addition to bisphosphine complex Pd(PH3)(2), in path B of each reaction, the first step is alkyne coordination to bisphosphine complex Pd(PH3)2, and in path C of each reaction, the first step is the PH3 dissociation front Pd(PH3)2 to form monophosphine complex Pd(PH3) For both reactions, path B is favored.

Theoretical studies on the reaction mechanism of palladium(0)-catalyzed addition of thiocyanates to alkynes

The reaction mechanism of the Pd(0)-catalyzed alkyne cyanothiolation reaction is investigated by MP2, CCSD(T) and the density functional method B3LYP. The overall reaction mechanism is examined. The B3LYP results are consistent with the results of CCSD(T) and MP2 methods for the isomerization, acetylene insertion and reductive elimination steps, but not for the oxidative addition step. For the oxidative addition, the bisphosphine and monophosphine pathways are competitive in B3LYP, while the bisphosphine one is preferred for CCSD(T) and MP2 methods.

Theoretical Studies on the Reaction Mechanism of Platinum-Catalyzed Diboration of Allenes

The reaction mechanism of Pt(0)-catalyzed diboration reaction of allenes is investigated by the density functional method B3LYP. The overall reaction mechanism is examined. The electronic mechanisms of the allene insertion into the Pt-B bond are discussed in terms of the electron donation, back-donation, and d-pi interaction. During allene insertion into the Pt-B bond, the internal carbon atom of allene is preferred over the terminal one due to the stronger electron back-donation and stronger charge transfer in the former case than that in the latter one.

Carbon-supported Pd nanocatalyst modified by non-metal phosphorus for the oxygen reduction reaction

A carbon-supported palladium catalyst modified by non-metal phosphorus(PdP/C) has been developed as an oxygen reduction catalyst for direct methanol fuel cells.The PdP/C catalyst was prepared by the sodium hypophosphite reduction method. The as-prepared Pd nanoparticles have a narrow size distribution with an average diameter of 2 nm. Energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) results indicate that P enters into the crystal lattice of Pd and forms an alloy.

Grown-like macrocycle zinc complex derived from beta-diketone ligand for the polymerization of rac-lactide

Enolic Schiff base zinc (II) complex 1 was synthesized. XRD revealed 1 was a novel crown-like macrocycle structure consisted of hexanuclear units of (LZnEt)(6) via the coordination chelation between the Zn atom and adjacent amine nitrogen atom. Further reaction of 1 with one equivalent 2-propanol at RT produced Zn-alkoxide 2 by in situ alcoholysis. Complex 2 was used as an initiator to polymerize rac-lactide in a controlled manner to give heterotactic enriched polylactide. Factors that influenced the polymerization such as the polymerization time and the temperature as well as the monomer concentration were discussed in detail in this paper.

Palladium within ionic liquid functionalized mesoporous silica SBA-15 and its catalytic application in room-temperature Suzuki coupling reaction

Initially, pore walls of mesoporous silica SBA-15 with template were modified with chlorotrimethylsilane. Then imidazolium salts were similarly incorporated covalently in the inner pore walls of mesoporous silica SBA-15 albeit without the template. Finally, palladium salts were introduced into the pore channels of the previously processed mesoporous silica via electrostatic interaction. The resulting palladium catalysts demonstrated exceptional activity for the room-temperature Suzuki Coupling reaction in aqueous-organic mixed solvents and good recycling ability for at least 4-6 times.

One-pot synthesis and characterization of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids and multihydroxyl secondary Amines

A convenient and cost-effective strategy for synthesis of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids (A(2)) and multihydroxyl secondary amine (CB2) has been developed. By optimizing the conditions of model reactions, the AB(2)-type intermediates were formed dominantly during the initial reaction stage. Without any purification, the AB(2) intermediate was subjected to thermal polycondensation in the absence of any catalyst to prepare the aliphatic and semiaromatic hyperbranched poly(ester-amide)s bearing multi-hydroxyl end-groups.

Pd nanoparticles supported on WO3/C hybrid material as catalyst for oxygen reduction reaction

Pd nanoparticles supported on WO3/C hybrid material have been developed as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells. The resultant Pd-WO3/C catalyst has an ORR activity comparable to the commercial Pt/C catalyst and a higher activity than the Pd/C catalyst prepared with the same method. Based on the physical and electrochemical characterizations, the improvement in the catalytic performance may be attributed to the small particle sizes and uniform dispersion of Pd on the WO3/C, the strong interaction between Pd and WO3 and the formation of hydrogen tungsten bronze which effectively promote the direct 4-electron pathway of the ORR at Pd.

Synthesis of magnetite core-shell nanoparticles by surface-initiated ring-opening polymerization of L-lactide

Fe3O4-polylactide (PLA) core-shell nanoparticles were perpared by surface functionalization of Fe3O4 nanoparticles and subsequent surface-initiated ring-opening polymerization of L-lactide. PLA was directly connected onto the magnetic nanoparticles surface through a chemical linkage. Fourier transform infrared (FT-IR) spectra directly provided evidence of the PLA on the surface of the magnetic nanoparticles. Transmission electron microscopy images (TEM) showed that the magnetic nanoparticles were coated by PLA with a 3-nm-thick shell.

Synthesis and identification of Heterocyclic derivatives of fullerene C-60: Unexpected reaction of anionic C-60 with benzonitrile

During the reaction of reduced C-60 with benzyl bromide in benzonitrile, a novel cis-1 C-60 adduct, 1,4-dibenzyl-2,3-cyclic phenylimidate C-60 (1), Was obtained rather than the expected product of 1,4-dibenzyl C-60. The structure of compound 1 was analyzed by X-ray single-crystal diffraction, identifying the presence of a five-membered heterocycle at a [5,6] bond of C-60. One of the heteroatoms is assigned as a nitrogen atom; however, the identity of the other heteroatom cannot be determined unambiguously by crystallography due to similarity between the nitrogen and oxygen atoms.

Glass wafers bonding via Diels-Alder reaction at mild temperature

In this paper, we introduced a novel bonding method of glass wafers by Diels-Alder reaction at mild temperature. After standard hydroxylization and aminosilylation, two wafers were modified by 2-furaldehyde and maleic anhydride, respectively. Then they were brought into close contact and tightly held with a clamping fixture. A strong bonding could be achieved by annealing for 5 h at 200 degrees C. Bonding strength is as high as 1.78 MPa and sufficient for most application of microfluidic chips.

Combined Effects of Hot Curing Conditions and Reaction Heat on Rubber Vulcanization Efficiency and Vulcanizate Uniformity

A mathematical model of the chemical kinetics of silicone rubber Vulcanization is developed, with the thermal effects being computed using the increment method, and the hot Vulcanization process estimated with the finite element method. The results show that the reaction heat of rubber vulcanization is important for energy saving, and that a proper curing medium temperature is important when considering both vulcanization efficiency and vulcanizate uniformity. The results also indicate that increases in the forced convective heat transfer coefficient have no significant effect above a certain level. The validity of the numerical model is indirectly proven by comparison with existing data.