3D Additive Technologies Research Articles

Experimental Studies of Microwave Tubes with Components of Electron–Optical and Electrodynamic Systems Implemented Using Novel 3D Additive Technology

Novel additive technology of the Chemical Metallization of Photopolymer-based Structures (CMPS) is under active elaboration currently at the IAP RAS (Nizhny Novgorod). The use of this technology has made it possible to implement components of electron–optical and electrodynamic systems for high-power microwave vacuum tubes, such as a gyrotron and a relativistic Cherenkov maser, the design and experimental studies of which are described in this paper. Within the framework of the gyrotron developments, we carried out a simulation of the distribution of the heat load on the collector of high-power technological gyrotron taking into account secondary emission. The prospect of a significant reduction in the maximum power density of the deposited electron beam was shown. The experimental study of the gyrotron collector module manufactured using CMPS technology demonstrated high potential for its further implementation. Recent results of theoretical and experimental studies of a spatially extended Ka-band Cherenkov maser are presented. In this oscillator, the 2D-periodical slow-wave structure made by the proposed technology was applied and a narrow-band generation regime was observed with a sub-GW power level. The design and simulations of a novel selective electrodynamic system for a high-harmonic gyrotron with the planned application of the CMPS technology are discussed.

Improving the Performances of a Mortar for 3D Printing by Mineral Modifiers

Erection of buildings using 3D printing has great potential. However, its mass use for high-rise buildings is hampered by the lack of cement mortars with the required technical characteristics, the most important of which is high plastic strength (in the first minutes after pouring). The significance of the work (novelty) lies in the creation of a composite binder using a mineral modifier obtained by joint grinding up to 500 m2/kg of bentonite clay, chalk, and sand. A comprehensive study of the developed mortars was carried out from the standpoint of the necessary characteristics for volumetric concreting of high-rise thin-walled buildings. A composite binder for high-strength composites (compressive strength up to 70 MPa) has been obtained, which can provide effective mortars for 3D-additive high-rise construction technologies. The influence of the genetic characteristics of the modifier components on the properties of the composite binder has been established. The hydration process in this system of hardening concrete of the optimal composition proceeds more intensively due to the significantly larger specific surface of the mineral modifier components, which act as an active additive and activators of the crystallization of new growths. It has been proven that the features of mortars of high-strength fine-grained composites for 3D-additive technologies of high-rise buildings must meet special properties, such the rheotechnological index and the bearing capacity of the freshly formed layer (plastic strength or dimensional stability). Compared with a conventional mortar, the plastic strength of the developed one increases much faster (in 15 min, it is 762.2 kPa, in contrast to 133.0 kPa for the control composition). Thus, the strength remains sufficient for 3D printing of high-rise buildings and structures.

ИССЛЕДОВАНИЕ ФИЗИКО-МЕХАНИЧЕСКИХ СВОЙСТВ КРУПНОПОРИСТОГО КЕРАМЗИТОБЕТОНА ДЛЯ ТРЕХСЛОЙНОГО 3D-АДДИТИВНОГО СТРОИТЕЛЬСТВА

The article considers the solution of the urgent problem of the development of 3D additive technologies in Russia by creating a new model of the forming device and the development of composite materials. The purpose of this work is to study the physical, technological and thermal properties of coarse-pored expanded clay concrete. The required characteristics are determined by standard methods and requirements of regulatory documents, including modern physico-chemical methods of analysis and a wide range of modern and original research methods corresponding to modern scientific knowledge. Results. Compositions of coarse-porous expanded clay concrete with compressive strength up to 9.2 MPa, water absorption up to 25% by weight and shrinkage deformations in the range of 0.1...0.3 mm/m were obtained. To simulate the behavior of the studied systems, a two-factor three-level experiment was conducted for each type of mixture of coarse-pored expanded clay concrete, which allowed us to obtain regression equations characterizing the relationship of variable parameters with certain properties of the system. It was revealed that the value of the average density is most affected by the specific consumption of the binder. While the strength depends most on the I/O ratio. Moreover, in this case, the amount of water is less related to the porosity of the cement stone itself, and more to the consistency and stickiness of the resulting glue, its ability to evenly cover the filler particles. It is established that rationally selected compositions of structural and thermal insulation KPKB for the internal filling of a three-layer "printed" wall, homologation and thermal insulation will ensure the formation of the required technical and operational indicators.

Сomposite binders for 3d additive technologies

Introduction. In recent years, there has been an active development of 3D additive technologies. This trend could not but affect the construction industry. However, printing using plastics and other organic compounds differs significantly in its technological features from printing with building compounds. Concrete and mortars used in layer-by-layer printing must have a number of technological properties, such as sufficient viscosity for extrusion by an extruder, low mobility to maintain geometry after laying, high setting speed and strength after hardening. Currently, there are a number of compositions that meet these requirements, however, they, as a rule, are not distinguished by high strength and require a wide raw material base, which may not be available in field printing conditions. As a result, it is necessary to expand the range of building materials for 3D printing, suitable for the above criteria, as well as satisfying economic indicators.Materials and methods. Research has been carried out using physical and mechanical tests, X-ray phase analysis and electron microscopy on the effect of finely ground mineral additives on the microstructure and hardening processes of composite binders with various dosages of functional additives.Results. The results of studies on the production of composite binders for 3D additive technologies using Portland cement and man-made waste - waste of wet magnetic separation of the Stary Oskol electrometallurgical plant, modified with additives accelerators (Technonikol Master) and plasticizers (Polyplast PK-R) using mathematical planning and construction of mathematical models for composite binders with different hardening times are pesented.Conclusion. The efficiency of using the obtained composite binder has been proven, the use of which provides an increase in rheological properties, and also makes it possible to save expensive portland cement.

3D-АДДИТИВНЫЕ СТРОИТЕЛЬНЫЕ ТЕХНОЛОГИИ. ТЕОРИЯ И ПРАКТИКА

The results of the study of the theoretical foundations of the manufacture of building materials using 3D printing based on composite binders with various molding methods and their practical testing on prototypes of fine-grained concrete are presented. The principles of regulating the structure and properties of composites through the use of a mineral modifier for the construction of high-rise building objects using 3D-additive technology are considered. The influence of the characteristics of the raw material components on the properties of the obtained composite is shown. The structure formation of the hardening cement-containing system in the presence of a mineral modifier proceeds more intensively due to the high specific surface area and energy capacity of the components, which is an active mineral additive and the basis for the crystal formation of new hydrate compounds. The difference in the strength characteristics of the printed wall is due to the direction of the sample cut. Applying a breaking load along the direction of forming of a 3D printer gives a slightly higher strength than perpendicular to the direction of forming. This phenomenon can be explained by the shape of the layer after solidification of the mixture, which is an ellipse in cross section

Effective Application of 3D Additive Technologies for Creation of Construction Compositions Using Technogenic Raw Materials

Nowadays the great attention of scientists and engineers is attracted by applying 3D-additive technologies for obtaining high-strength fine-grain concrete by using technogenic raw materials. It is distinguished from the conventional concrete by the increased content of cement stone, lower grain size, multicomponent composition and the increased specific surface of the aggregate [1-3]. The performance characteristics of such concrete mostly depend on its aggregate’s properties and water content.The paper considers the problem of improving fine-grain concretes production technologies. For this purpose the opportunities of 3D-additive technologies, which improve the efficiency of fine-grain concretes production technology due to using concrete compositions with natural and technogenic raw materials of various chemical and mineral formulas, were studied. The opportunity of increasing the economic feasibility of high-strength fine-grain concretes, produced by means of 3D-additive technology, with preserving their performance characteristics, has been demonstrated