33results about How to "Improved size distribution" patented technology

A large number of properties of nanostructures depend on their size, shape and many other parameters. As the size of a nanostructure decreases, there is a rapid change in many properties. When the nanostructure is completely destroyed, those properties essentially disappear. Systems based on changes in properties of nanostructures due to the destruction of nanostructures are proposed. The systems can be used for monitoring the total exposure to organic, inorganic, organometallic and biological compounds and agents using analytical methods.

The invention provides an active carbon-supported ruthenium ammonia synthesis catalyst and a preparation method thereof. The catalyst takes active carbon as a carrier and takes ruthenium as an active component; the components of the catalyst are (CA+Ru)-Ba-K / AC and CA-Ru-Ba-K / AC, wherein, CA represents citric acid and AC represents the active carbon; in preparation of the catalyst, the citric acid is selected to carry out the pretreatment of the active carbon and ruthenium chloride; one or more of barium nitrate, potassium hydroxide or potassium nitrate is or are selected as an assistant; the equivalent-volumetric impregnation method is adopted in the preparation method for preparing the catalyst. Compared with the sol-gel method or the oxidation method in the prior art, the invention adopts the citric acid method and has the advantages of simple technique, high preparation efficiency, little energy consumption, cheap raw material and less material consumption, thus being beneficial to greatly lowering the production cost. The devices required by the invention are simple, are easy to be operated, do not need to change the original devices and are easy to realize mass production. The catalyst prepared by the invention has good performance and strong catalytic activity.

The invention belongs to energy chemical technical field, especially relates to a fluidized bed reactor and a method for preparation of polyoxymethylene dimethyl ethers from dimethoxymethane and paraformaldehyde. The fluidized bed reactor comprises a gas inlet, a gas distributor, a catalyst inlet, a gas outlet, a fluid inlet, a catalyst outlet, a bottom component and an interstage component, a bottom component related gas upward channel, an interstage component related gas upward channel, a fluid outlet, a bottom downcomer and an interstage downcomer. A process for preparation of polyoxymethylene dimethyl ethers comprises the steps of: fluidizing gas is introduced into a bottom bed from the gas inlet via the bottom component related gas upward channel through the gas distributor; the fluidizing gas goes upwards and flows out of the reactor via the gas outlet; paraformaldehyde and dimethoxymethane are introduced into a bed through the fluid inlet; the fluid goes downwards and leaves the reactor via the fluid outlet. Compared with a conventional cannula reactor, the fluidized bed reactor improves the dispersion uniformity of catalyst and conversion of formaldehyde.

The invention provides a preparation method of polyimide foam plastic. The method comprises the steps as follows: firstly, after dianhydride is mixed with low-level aliphatic alcohol, an esterification reaction is performed, and a diacid diester solution is obtained; then the obtained diacid diester solution is mixed with polymerized monomer amine and polyamic acid powder to obtain a mixed solution; and finally, the obtained mixed solution is sequentially subjected to foaming and thermal imidization after concentration to obtain the polyimide foam plastic. The invention further provides the polyimide foam plastic and the preparation method thereof, and the method comprises the step that polyamic acid powder is added when dianhydride and isocyanate are used for preparing the polyimide foam plastic. According to the invention, the polyamide acid powder serves as a nucleating agent, so that a cell of an objected formed by foaming of polyimide is fine and smooth, that is, the size distribution of the cell is improved, the cell uniformity is better, then the flexibility performance and the like of the polyimide foam plastic are improved; meanwhile, the heat resistance is not influenced; and besides, the preparation method of the polyimide foam plastic is concise in processing, and low in energy consumption and production cost.

A method of processing a powdered feedstock to form a fabricated component is provided. The fabricated component includes a plurality of grains having a nominal grain size. The method includes providing the powdered feedstock material having a population of phase particulates with a first nominal size distribution disposed within a host matrix material. The method includes building a consolidated component from the powdered feedstock material in an additive manufacturing process, and fabricating the fabricated component from the consolidated component. The first nominal size distribution of the population of phase particulates is sized such that at least a portion of the population of phase particulates persists throughout the additive manufacturing process and is present as a processed population of phase particulates in the consolidated component. In addition, the processed population of phase particulates has a second nominal size distribution effective to produce the nominal grain size of the fabricated component.

The invention discloses a method for controlling PbS or PbSe quantum dot size distribution. The method comprises the following steps that: (1) first, CdSe (or CdS) quantum dots with larger sizes are injected into a precursor of lead, and PbSe (or PbS) quantum dots with larger sizes are obtained through a cation exchange reaction at the moment; (2) then, CdSe (or CdS) quantum dots with smaller sizes are continuously injected, and the PbSe (or PbS) quantum dots with smaller sizes are obtained through the cation exchange reaction at the moment; (3) finally, the size distribution of the PbSe (or PbS) quantum dots becomes narrower and narrower under the action of Ostwald ripening effect, so that the size distribution of the PbSe (or PbS) quantum dots is controlled. Through the method, various sizes of the PbSe (or PbS) quantum dots with extremely good size distribution can be obtained; moreover, the PbSe (or PbS) quantum dots are specifically stable in air; the method is low in cost, easy to operate, and not strict in environment requirement.