Mechanical Properties and Mineralogical Composition of Potash Ore as a Factor in Selecting the Processing Method

The correct selection of technology for processing potash ore depends on its mineralogical composition, the natural size and shape of grains, as well as on the amount and size of halite grains located in the intergranular space of sylvinites. The study of seams and mineralogical and petrographic studies of potash ore were carried out in order to determine the natural size of sylvinite grains, their shape, and the content of halite in the intergranular space.Moreover, the influence of these parameters on the beneficiation ability of the ore using dry cleaning process was determined. In addition, the data on laboratory studies using electric separation is provided in the paper. The results of the provided studies can be used by specialists of the mining industry when considering the influence of the mineral composition, size and shape of grains of potash ore in order to select the separation method at the early stages of development of potash deposits. The study of core material and mechanical properties, mineralogical and petrographic studies together with studies on beneficiation ability of ore presented in the article can be used, for example, in the preparation of a feasibility report.

Effect of carbon on the electrical resistivity of Ni – Al intermetallic alloy synthesized by an electrothermal explosion under pressure

In this paper, we studied the effect of carbon (3 wt. %) on the electrical resistivity of materials based on Ni − Al and Ni – Al − C synthesized by the electrothermal explosion in the temperature range 300 – 1300 K in a vacuum of 2·10–3 Pa. During an electrothermal explosion, a Ni – Al-based melt is formed in a powder reactive medium, in which carbon is dissolved. It is shown that during the crystallization of the final product, due to its low solubility in NiAl, carbon is located on the surface of intermetallic NiAl grains in the form of multilayer graphite nanofilms 50 – 80 nm thick, filling the intergranular space. It is shown that the synthesized materials have a metallic conductivity, and the electrical resistivity in the measured temperature range of 300 – 1300 K increases monotonically for the Ni – Al-based alloy from 16 to 40 mW·cm and for the carbon-containing Ni – Al – C material from 22 to 60 mW·cm. The temperature coefficient of resistance (TCS) also increases from 1.45·10–3 K–1 for NiAl to 1.77·10–3 K–1 for NiAl/C. The slope of the resistivity curves in the studied temperature range of 300 – 1300 K remains constant and is well described by a linear function.

Features of the internal structure of high-pressure metal-diamond composites

In the present work, composites were obtained by sintering a metal-diamond charge at a pressure of 4 GPa and a temperature of 1300°C. the experiments were carried out on a high-pressure apparatus of the split sphere “bars” type. Synthetic microcrystals of industrial synthesis were used as a diamond. The initial metal component for the experiments was copper and iron. it was shown that when sintering at high pressure, diamond crystals are tightly packed in the composite, while the metal phase completely fills the intergranular space, acting as a matrix. chemical analysis of the metal component of the samples revealed the presence of the following phases: copper-iron alloy, iron oxide and iron carbide. the results obtained indicate that several processes occur simultaneously in the diamond-copper-iron-oxygen system at high pressures and temperatures, which can significantly affect the characteristics of the resulting composite as a whole.

A Plethora of Epigenetic Minerals Reveals a Multistage Metasomatic Overprint of a Mantle Orthopyroxenite from the Udachnaya Kimberlite

More than forty mineral species of epigenetic origin have been identified in an orthopyroxenite from the Udachnaya-East kimberlite pipe, Daldyn kimberlite field, Siberian platform. Epigenetic phases occur as: (1) Mineral inclusions in the rock-forming enstatite, (2) daughter minerals within large (up to 2 mm) crystallized melt inclusions (CMI) in the rock-forming enstatite, and (3) individual grains and intergrowths in the intergranular space of the xenolith. The studied minerals include silicates (olivine, clinopyroxene, phlogopite, tetraferriphlogopite, amphibole-supergroup minerals, serpentine-group minerals, talc), oxides (several generations of ilmenite and spinel, rutile, perovskite, rare titanates of the crichtonite, magnetoplumbite and hollandite groups), carbonates (calcite, dolomite), sulfides (pentlandite, djerfisherite, pyrrhotite), sulfate (barite), phosphates (apatite and phosphate with a suggested crystal-chemical formula Na2BaMg[PO4]2), oxyhydroxide (goethite), and hydroxyhalides (kuliginite, iowaite). The examined epigenetic minerals are interpreted to have crystallized at different time spans after the formation of the host rock. The genesis of minerals is ascribed to a series of processes metasomatically superimposed onto the orthopyroxenite, i.e., deep-seated mantle metasomatism, infiltration of a kimberlite-related melt and late post-emplacement hydrothermal alterations. The reaction of orthopyroxene with the kimberlite-related melt has led to orthopyroxene dissolution and formation of the CMI, the latter being surrounded by complex reaction zones and containing zoned olivine grains with extremely high-Mg# (up to 99) cores. This report highlights the utility of minerals present in minor volume proportions in deciphering the evolution and modification of mantle fragments sampled by kimberlitic and other deep-sourced magmas. The obtained results further imply that the whole-rock geochemical analyses of mantle-derived samples should be treated with care due to possible drastic contaminations from “hiding” minor phases of epigenetic origin.

Influence Of Composition Of A Liquid Phase At Hardening Of Cements

The processes of structure formation of cement stone are considered. The change in the composition of the liquid phase and change in the hydration of polymineral cement over time are studied; the change in the concentration of ions of calcium in the course of cement hydration is determined. The effect of calcium chloride and sodium nitrite additives on the composition of the liquid phase during hydration of polymineral cements was investigated. It is shown that these additives significantly increase the metastable concentrations of calcium ions in the liquid phase of hydrating cements, differently affect the amount of supersaturation of the liquid phase and create different conditions for hydrate formation. The determining role of tricalcium silicate in the character of changes in the composition of the liquid phase and the conditions of subsequent hydrate formation during hardening of polymineral cements has been established. High concentrations of calcium ions in the liquid phase cause the removal of the hydrate formation zone from the surface of the initial cement grains into the volume of the intergranular space, which increases the uniformity of the distribution of the solid component in the volume of the cement stone.

Encapsulating soluble active species into hollow crystalline porous capsules beyond integration of homogeneous and heterogeneous catalysis

Homogeneous molecular catalysts and heterogeneous catalysts possess complementary strengths, and are of great importance in laboratory/commercial procedures. While various porous hosts, such as polymers, carbons, silica, metal oxides and zeolites, have been used in an attempt to heterogenize homogeneous catalysts, realizing the integration of both functions at the expense of discounting their respective advantages, it remains a significant challenge to truly combine their intrinsic strengths in a single catalyst without compromise. Here, we describe a general template-assisted approach to incorporating soluble molecular catalysts into the hollow porous capsule, which prevents their leaching due to the absence of large intergranular space. In the resultant yolk (soluble)–shell (crystalline) capsules, the soluble yolks can perform their intrinsic activity in a mimetic homogeneous environment, and the crystalline porous shells endow the former with selective permeability, substrate enrichment, size-selective and heterogeneous cascade catalysis, beyond the integration of the respective advantages of homogeneous and heterogeneous catalysts.

Effect of self-heating on the processing quality of rapeseed

The paper concerns the effect of adverse thermal phenomena on the processing quality of rapeseed. A measurement station was developed for the study, composed of a model cylindrical silo with a capacity of 3.85 m3, which was filled with seeds of winter rape cv. Suzy (2.5 t). In the conducted experiment, the silo was filled with three layers of seeds, the bottom layer witha moisture content of 7%, the middle layer with a moisture content of 12.7%, and the top layer with a moisture content of 7%. The experiment was carried out with temperature and humidity sensors in the vertical and horizontal axes, placed in a distance of 0.15 m from one another. The increase in temperature in the intergranular space measured during the self-heating pheno-menon can be divided into two stages: I – slow (up to approx. 150 h)and II – significant (from 150 h, 2-3ºC per day). As a result of the development of the self-heating phenomenon, the processing quality of rapeseed deteriorated. Indeed, under increased temperature the quality changes were so significant that they rendered the seeds unfit for any kind of consumption purposes.

Scoping of intergranular space of the grinding tool when processing wood and wood materials.

Актуальность проблемы получения необходимого качества обработанной поверхности древесины в настоящее время становится все более значимой в связи с повышением требований к качеству продукции деревообработки и получения наибольшего экономического эффекта для предприятия. Вопросом математического моделирования поверхности шлифовального инструмента с целью объективного описания его рельефа занимались многие исследователи. Так, при решении задачи установления взаимосвязи рельефа инструмента с шероховатостью поверхности обрабатываемой детали использовались методы представления его в виде набора профилей: в виде «резьбовой гребенки», в виде реализации случайной стационарной функции, в виде элементарных эффективных профилей. Второй путь моделирования поверхности инструмента, использовавшийся при установлении связи между характеристиками рельефа и его режущей способностью, заключается в представлении абразивных зерен в виде тел различной формы: шара, эллипсоида. Достаточно популярна статистическая многогранная модель абразивного зерна. По современным представлениям, основной причиной снижения работоспособности и износостойкости шлифовальных шкурок при обработке древесины является засаливание, которое происходит вследствие защемления сошлифованных частиц древесины в межзерновом пространстве, прилипания частиц шлифовальной пыли к поверхности шкурки, что обусловлено липкостью смазки и выделением смолистых веществ древесины при нагреве, накоплением на шкурке электростатического заряда, недостаточным объемом свободного межзернового пространства. Последовательное повышение давления прижима позволяет более полно использовать режущую способность шлифовальной ленты. Анализ показывает, что длительность каждого последующего этапа увеличения прижима будет больше, чем предыдущего, в связи с уменьшением доли застрявшей древесины, в то время как производительность процесса шлифования остается на прежнем уровне. Для увеличения износостойкости шлифовальных лент необходимо увеличивать объем межзернового пространства и уменьшать объем застревающей в этом пространстве стружки. Relevance of a problem of obtaining necessary quality of the processed surface of wood becomes more and more significant in connection with increase in requirements to quality of production of a woodworking and obtaining the greatest economic effect for the enterprise now. Many researchers dealt with an issue of mathematical model operation of a surface of the grinding tool for the purpose of the objective description of its relief. So, at the solution of a problem of establishment of interrelation of a relief of the tool with a roughness of a surface of the processed detail methods of its representation in the form of a set of profiles were used: in the form of "a carving comb", in the form of realization of random stationary function, in the form of the partial efficient profiles. The second path of model operation of a surface of the tool used at establishment of communication between characteristics of a relief and its cutting ability consists in representation of abrasive grains in the form of bodies of various forms: sphere, ellipsoid. The statistical polyhedral model of abrasive grain is rather popular. On the modern representations, the main reason for decrease in serviceability and wear resistance of abrasive papers when processing wood is the balling which occurs owing to jamming the unbound particles of wood in intergranular space, sticking of particles of grinding dust to a skin surface that is caused by stickiness of lubricant and selection of resinous substances of wood when heating, accumulation on a skin of an electrostatic charge, the poor volume of the free intergranular space. Serial build-up of pressure of a clip allows to use the cutting ability of an abrasive belt more fully. The analysis shows that duration of each subsequent stage of increase in a clip will be more, than previous, in connection with decrease of a share of the got stuck wood while efficiency of process of grinding remains at the previous level. For increase in wear resistance of abrasive belts it is necessary to increase the volume of intergranular space and to reduce the volume of the shaving which is getting stuck in this space.

In-situ formation and densification of MgAl2O4-Y3Al5O12 and MgAl2O4-MgNb2O6 ceramics via a single-stage SRS process

MgAl2O4 (MA)-Y3Al5O12 (YAG) and MA-MgNb2O6 (MN) ceramics with high density were successfully fabricated via a single-stage solid-state reaction sintering (SRS) process at 1580?C for 4 h. The effect of Y2O3 or Nb2O5 additions from 2.5 wt% to 7.5 wt% on the phase compositions, microstructures, shrinkage ratio, apparent porosity, bulk density and cold compressive strength of MA-YAG and MA-MN ceramics has been investigated. It was found that MgO and Y2O3 reacted with Al2O3 to form MA and YAG during sintering while Nb2O5 reacted with MgO to form MN. YAG and MA grains in the MA-YAG ceramics exist as granular shape, and their average grain size is about 1 ?m and 5 ?m, respectively. YAG grains distribute on the intergranular space of MA particles. Polygonal MA particles can be observed in the MA-MN ceramics, and MN grains distribute on the intergranular space of MA particles as well as on MA particles. Rod-like MN grains can be formed in the MA-MN ceramics by addition of 7.5 wt% Nb2O5. The diameter shrinkage ratio, volume shrinkage ratio, bulk density and cold compressive strength of MA-YAG and MA-MN ceramics are greatly improved by doping Y2O3 and Nb2O5, respectively.

Tin and Nickel Influence on the Structure and Properties of the Leaded Bronze Obtained by Means of the Centrifugal Casting

The effect of tin and nickel on the structure and properties of the leaded bronze obtained by means of the centrifugal casting has been studied. Regularities of change of strength properties and ductility explain the features of the structure formation under the influence of nickel and tin. The paper demonstrates that introduction of nickel promotes a uniform distribution of the plate-shaped lead in the interdendritic space. Introduction of tin sufficient for the formation of eutectoid results in a uniform and compact arrangement of lead in the intergranular space. Complex alloying with nickel and tin contributes to strength characteristics increase.