Subject: Technology
Class: 2A.
Program: " Primary School XXI century "author Lutseva E.A.
Topic. Different materials - different properties
Didactic goal: Create conditions for studying properties different materialswho surround a person
Tasks:
personal
educate love and careful attitude towards nature
contribute to the establishment of the experience of joint creative activity of students
metaPermet
develop research skills and skills, skills to work in pairs; Creative thinking of students
subject
find out the experienced way, which properties have known learning materials: paper, fabric, wood, metal;
Means of education:
multimedia projector, presentation for lesson
Lutseva. And. Technology 2 class. Tutorial. - M., Ventana-Count, 2008
Lutseva. And. Workbook "Learning Mastery" -m., Ventana Graf, 2008
material samples: pieces of paper, fabric; Plates of metal. tree
plastic cups with water
Training Methods: Research
Forms of cognitive activity:
frontal;
group;
individual.
Stage
Teacher's activities
Activities teaching
Wood
Self-determination to activities
Guys, in the past lesson, we made a doll from different materials. Tell me, could you play with a doll toy that is made of snow? Chocolate? Why?
What did not come to us in these materials?
Tell me, what does the choice of material for the product depends?
Today at the lesson we will conduct research and find out what you need to know about the materials not to make a mistake in the choice. We will work in groups (5 + 5 + 4)
Children answer that the snow doll melts in warm, sheds from chocolate, can also be deformed.
Can I make a nail from ice? No
Sugar boat? No
Children express guesses, assumptions.
Personal:
Self-determination (Motivation of the teaching);
regulatory:
goaling; communicative:planning training cooperation with teacher and peers
Actualization of knowledge
slide number 2.
slide number 3.
slide number 4.
Frontal work is invited to answer questions:
What is called material?
What do they call the product?
The correctness of the answer can be checked by clicking on the link to Slide No. 3
working with a textbook Read the text on from 21 and answer questions
Is the natural reserves endless?
Material is something that do something
The product is the creation of a man's hands.
Children read the text on page 21
The statement of children about the careful attitude to natural reserves
communicative:planning educational cooperation with teacher and peers;
cognitive:logical - analysis of objects in order to highlight features,
semantic reading.
Staging learning activities
slide number 5.
slides number 6, 7.8
slide number 9.
You have the same images on the table various items. Consider images of objects. What groups can they divide them? Why? Discuss in pairs. Children's responses are heard.
Check the correctness of your actions. Name which products are made from the same material?
Explain why these materials are used for these products. What features? What depends on the choice of material for the product?
Children perform practical work on the division of objects into groups:
From wood: Chair, books, board, notebook, wooden gate., dresser
From the fabric: curtains, shirt, shorts.
Metal: cutlery, drills, iron gates.
The clothes should make it easier to warm up, absorb.
Metal products are durable.
Children express assumptions that you need to know any features, characteristics of materials.
cognitive:logical - analysis of objects in order to highlight features and classification; communicative:
initiative cooperation in finding a solution to the problem;
cognitive:general educationalindependent allocation - the formulation of a cognitive goal; brain teaser -formulation of the problem for which we will explore
Building a way out of difficulty
slide number 10.
slide number 11.
slide number 14.
slide number 15.
Let's show curiosity and Read more.
We carry out research. Work in groups.
1. Put samples of different materials: paper, fabric, wood, metal. Carefully consider them. Tell me what you see.
Take each material in your hands, remember, bend. Let's knock What do you feel?
What you see and feel is the properties of materials.
In order to understand the features (properties) of materials, we will conduct their practical research, that is, we will study in detail.
2. Practical study of the properties of various materials. Spend a study of the properties of materials. Everything necessary for the study is on your tables. The results of the study brought to the table.
Check out the correctness of your sample work. Do your answers match the sample. If not, let's discuss.
Task: Study P.22
1. Acquisition and Integration of Knowledge - 4
2. Cooperation - 4
3. Communication - 2
4. Solving problems - 3
5. Using ICT - 1
6. Self-organization and self-regulation - 2
Oral speech priming:
The properties of the material are what you see, feel.
Children conduct research with materials. Educational task on page 22 of the textbook and fill the table
Self-test according to the sample.
regulatory:planning, prediction; cognitive:
analysis of objects in order to highlight features, symbolic-symbolic action (work with the table)
communicativeinitiative cooperation in the search and selection of information,
planning and distribute duties;
regulatory:control, assessment, correction;
perform a learning task with itself "and mutual test;
cognitive:general educational -skill structuring knowledge communicative:partner behavior management - control, correction, assessment of partner actions, skill
adequately interact within the framework of the training dialogue;
- represent the result of the Group's activities.
Primary fixing
Read the question on page 22
Analyze the table:
Are there similar properties from different materials?
Name the same properties of different materials. What material is elastic? And what material with this property do you know?
How does the knowledge of the properties of different materials help each wizard in his work?
Children work on the table.
Yes, there are.
Change during deformation: paper, fabric
Do not break: wood, metal.
It is not deformed: wood, metal.
Fabric, rubber.
regulatory:control, assessment, correction; cognitive: The ability to consciously and arbitrarily build speech statement, reflection of methods and conditions of action; communicative:ability to express your thoughts
Mastering new knowledge
Creative task in the group
Materials are given to you. A task to imagine that of them may turn out? Think, check with a table how to use the properties of the material.
Prove, the correctness of the choice of material.
Work in groups. Children fill in cards.
Paper -
Wood -
Metal -
The cloth -
regulatory:control, correction, allocation and awareness of what is absorbed and what is still subject to assimilation, awareness of the quality and level of assimilation;
personal:self-determination
Communicative:ability with sufficient completeness and accuracy to express your thoughts
Reflection activities
Guys, now you can answer the question: Do similar properties come from different, externally similar materials?
What new have you recognized? What did you learn? Where in life can this knowledge come in handy?
Which of you was difficult? Who coped with difficulties? Who helped comrades?
Rate it personal work In the group and work of the whole group.
Express an opinion about the lesson
Continue the sentences: I did not know ..., I learned .... I didn't know how., I learned ...
Responses of children.
Communicative:ability with sufficient completeness and accuracy to express their thoughts; cognitive:reflection; personal:measiacy
Application. Tables.
Properties of materials
What explore
paper
wood
the cloth
metal
smooth
rough
rough
smooth
loose
dense
loose
dense
yes
no
yes
no
Is it stretches (elasticity)
no
no
yes
no
yes
no
yes
no
yes
Yes but not sink
yes
No, sink
yes
no
yes
no
Properties of materials
What explore
paper
wood
the cloth
metal
What a surface (smooth, rough)
What density (dense, loose)
Whether changes in crime (deformation)
Is it stretches (elasticity)
What transparency (shines or not)
What is the relationship to moisture (wet or not)
What strength (rushing or not)
Home\u003e Lecture
General about building materials.
In the process of construction, operation and repair of buildings and structures, construction products and structures of which they erected are subjected to various physical and mechanical, physical and technological impacts. From the engineer-hydraulic engineering required with knowledge of the right to choose the material, products or design that has sufficient resistance, reliability and durability for specific conditions.
Lecture №1
General information about building materials and their basic properties.
Building materials and products used in the construction, reconstruction and repair of various buildings and structures are divided into natural and artificial, which in turn are divided into two main categories: the first category includes: brick, concrete, cement, timber, etc. When erecting various elements of buildings (walls, overlaps, coatings, floors). To the second category - special purpose: waterproofing, thermal insulation, acoustic and other sources of building materials and products are: Stone natural building materials of them; binding materials inorganic and organic; forest materials and products of them; hardware. Depending on the purpose, the conditions for the construction and operation of buildings and structures, appropriate building materials are selected, which have certain qualities and protective properties From the impact on them of different external environment. Given these features, any building material must have certain construction and technical properties. For example, the material for the outer walls of the buildings should have the smallest thermal conductivity with sufficient strength to protect the room from the outer cold; Material of the structure of hydrochromelic purposes - waterproof and resistance to alternate humidification and drying; The material for the coating is expensive (asphalt, concrete) must have sufficient strength and low abrasability to withstand the load from transport. Classifying materials and products, it must be remembered that they must have good properties and qualities.Property - The characteristic of the material manifested in the process of its processing, application or operation. Quality - A set of material properties that determine its ability to meet certain requirements in accordance with its appointment. Succession of building materials and products is classified into three main groups: physical, mechanical, chemical, technologicaland etc . TO chemical The ability of materials to resist the action of a chemically aggressive medium, which causes metabolic reactions leading to the destruction of materials, changes in its initial properties: solubility, corrosion resistance, resistance to rotting, hardening. Physical properties : medium, bulk, true and relative density; Porosity, humidity, moisture production, thermal conductivity. Mechanical properties: limits of strength in compression, stretching, bending, shift, elasticity, plasticity, rigidity, hardness. Technological properties: Convertibility, heat resistance, melting, hardening and drying rate.
Physical I. chemical properties Materials.
Average densityρ 0 Mass M units V. 1 absolutely dry material in a natural state; It is expressed in g / cm 3, kg / l, kg / m 3. Bulk density bulk materials ρ n. Mass M units V. n. dried freely fused material; It is expressed in g / cm 3, kg / l, kg / m 3. True densityρ Mass M units V. material in absolutely dense state; It is expressed in g / cm 3, kg / l, kg / m 3. Relative densityρ(%) - degree of filling material of the material of the solid substance; It is characterized by the ratio of the total volume of solid V. In the material to the entire volume of the material V. 1 or ratio of medium density of material ρ 0 to its true density ρ:, or
. PorosityP
- degree of filling material of the material by pores, voids, gas-air inclusions: for solid materials: 
For bulk: 
Gigroscopic - The ability of the material to absorb moisture from the environment and thicken it in the mass of the material. HumidityW.
(%)
- the ratio of the mass of water in the material m. at =
m. 1
-
m.
to the mass of it in absolutely dry condition m.: 
Water absorptionAT
- characterizes the ability of the material when contacting with water to absorb and hold it in its mass. Distinguish between mass AT m. and volume AT about Water absorption. Mass water absorption(%)
- the ratio of mass absorbed water material m. at to the mass of the material in a completely dry condition m.: 
Volume water absorption(%)
- The ratio of volume by absorbed water material m. at /
ρ
at
to his volume in a water-saturated state V. 2
: 
Moisture report - The ability of the material to give moisture. Mechanical properties of materials.
Compressive strengthR. - the ratio of the destructive load P (H) To the sample cross section F. (see 2). It depends on the sample size, the speed of the load application, the shape of the sample, humidity. Tensile strengthR. r - the ratio of the destructive load R to the initial area of \u200b\u200bthe sample cross section F.. Bending StrengthR. and - Determine on specially manufactured beams. Rigidity - The property of the material to give small elastic deformations. Hardness - The ability of the material (metal, concrete, wood) to resist penetration into it under constant load of the steel ball.Lecture №2.
Natural stone materials.
Classification and main types mountain breeds.
Mountain breeds are used as natural stone materials in construction, which have the necessary construction properties. By geological classification, rock rocks are divided into three types: 1) overhead (primary), 2) sediment (secondary) and 3) metamorphic (modified). 1) Overhead (primary) rocks Formed when cooled of a molten magma rising from the depths of the earth. The structures and properties of the erupted rocks largely depend on the cooling condition of the magma, and therefore these breeds are divided into depth and poland. Deep rocks formed with a slow cooling of the magma in the depths earth crust At high pressures of the overlying layers of the Earth, which contributed to the formation of rocks with a dense grain-crystalline structure, large and medium density, a high limit of compressive strength. These breeds have low water absorption and high frost resistance. These breeds include granite, sheniet, diorit, gabbro, etc. Poland breed formed during the release of magma on ground surface with relatively fast and uneven cooling. The most common reputable rocks are porphyr, diabases, basalt, volcanic loose rocks. 2) Sediment (secondary) rocks were formed from primary (erupted) rocks under the influence of temperature differences, solar radiation, water action, atmospheric gases, etc. In this regard, sedimentary rocks are divided into cute (loose), chemicaland organogenic. To chip Liquid rocks include gravel, crushed stone, sand, clay. Chemical sedimentary rocks : Limestone, Dolomite, Gypsum. Organogenic rock breeds: Limestone-shelter, diatomit, chalk. 3) Metamorphic (modified) rocks Formed from the erupted and sedimentary rocks under the influence of high temperatures and pressures in the process of raising and lowering the earth's crust. These include clay slate, marble, quartzite.
Classification and main types of natural stone materials.
Natural stone materials and products are obtained by treating rocks. By method of obtaining Stone materials are divided into a torn stone (boot) - mined by an explosive way; Rough-grained stone - get a splitting without processing; crushed - get crushing (crushed stone, artificial sand); Assorted stone (cobblestone, gravel). Camera materials in shape divide on stones incorrect form (crushed stone, gravel) and piece products that have the right shape (plates, blocks). Crusheden - Acreditated slices of rocks with a size of 5 to 70 mm, obtained by mechanical or natural crushing of boot (ripped stone) or natural stones. It is used as a large aggregate for the preparation of concrete mixes, base devices. Gravel - Poed slices of rocks in size from 5 to 120 mm are also used to prepare artificial gravel-rubble mixtures. - The mixture of grain of rocks in size from 0.14 to 5 mm. It is usually formed as a result of weathering rocks, but can be obtained and artificial by crushing gravel, rubble, and rocks of rocks.Lecture number 3.
Hydrotational (inorganic) binders.
- Aerial binders. Hydraulic binders.
Hydraulic lime is a slowly grabbing and slower substance. It is used for the preparation of mortars, low-quality concrete, light concrete, upon receipt of mixed concrete. Portland cement - hydraulic binder, obtained by a joint, thin grinding grinding and two-wheel gypsum. Clinker - Product firing to sintering (at T\u003e 1480 ° C) of a homogeneous, a certain composition of the natural or raw mixture of limestone or gypsum. The raw material is burned in rotating furnaces. Portland cement as a binder is used in the preparation of cement solutions and concrete. SlagoporTland cement - In its composition, has a hydraulic additive in the form of a granular, domain or electrothermophosphorus slag., cooled by a special mode. It is obtained by a co-grip of a portland cement clinker (up to 3.5%), slag (20 ... 80%), and a gypsum stone (up to 3.5%). Slagoportland cement has a slow rise in strength in the initial period of hardening, but in the future the rate of increases of strength increases. It is sensitive to the surrounding temperature, racks when exposed to soft sulphate waterhas a reduced frost resistance. Carbonate portland cement They are obtained by a co-grinding of cement clinker with 30% limestone. It has reduced heat dissipation when hardening, increased resistance.
Lecture number 4.
Construction solutions.
General.
Construction solutions It is carefully dispensed fine-grained mixtures consisting of an inorganic binder (cement, lime, gypsum, clay), small aggregate (sand, crushed slag), water and in the necessary cases of additives (inorganic or organic). In freshly prepared state, they can be laid on the basis thin layer, Filling all his irregularities. They do not resolve, collapse, harden and gain strength, turning into a creamy material. Building solutions are used with stone wketches, finishing, repair and other works. They are classified by medium density: heavy with medium ρ \u003d 1500kg / m 3, lungs with medium ρ <1500кг/м 3 . По назначению: гидроизоляционные, талтопогенные, инъекционные, кладочные, отделочные и др. Растворы приготовленные на одном виде вяжущего вещества, называют простыми, из нескольких вяжущих веществ смешанными (цементно-известковый). Строительные растворы приготовленные на воздушных вяжущих, называют воздушными (глиняные, известковые, гипсовые). Состав растворов выражают двумя (простые 1:4) или тремя (смешанные 1:0,5:4) числами, показывающие объёмное соотношение количества вяжущего и мелкого заполнителя. В смешанных растворах первое число выражает объёмную часть основного вяжущего вещества, второе – объёмную часть дополнительного вяжущего вещества по отношению к основному. В зависимости от количества вяжущего вещества и мелкого заполнителя растворные смеси подразделяют на fatty - with a large amount of binder. Normal - with the usual binder content. Skinny - containing a relatively small amount of binder (low plastic). For the preparation of mortars, it is better to use sand with grains having a rough surface. The sand protects the solution from cracking when hardening, reduces its cost. Waterproofing solutions (waterproof) - cement solutions of composition 1: 1 - 1: 3.5 (usually fat), in which Cerezite, sodium amazect, calcium nitrate, iron chloride, bitumen emulsion. Cerepes - represents a mass of white or yellow color, obtained from aniline acid, lime, ammonia. Cerezite fills fine pores, increases the density of the solution, making it waterproof. For the manufacture of waterproofing solutions, portland cement, sulphate-resistant portland cement are used. Sand is used as a fine aggregate in waterproofing solutions. Masonry mortar - Used when laying stone walls, underground structures. They are cement-lime, cement-clay, limestone and cement. Finishing (plaster) solutions - divided into appointment to external and internal, in plaster on the preparatory and finishing. Acoustic solutions - Light solutions possessing good sound insulation. Prepared these solutions from Portland cement, Slagoportland cement, lime, gypsum, etc. binders using light porous materials (pumice, perlite, ceramisit, slag).Lecture number 5.
Conventional concrete on hydrotation binders.
- Materials for conventional (warm) concrete. Design composition concrete mix.
In addition to private residues, full remnants are found. BUTwhich are defined as the sum of all private residues in% on the overlying sines + private residue on this sieve:
According to the results of sand sifting, its size module is determined:
where BUT - Full balances on sints,%. The sand module distinguishes the sand is large ( M. to >2,5
), middle ( M. to =2,5…2,0
), small ( M. to =2,0…1,5
), very small ( M. to =1,5…1,0
). By applying sand sifting curve on a graph of a permitted grain composition, sand fitness is determined for the manufacture of concrete mix. 1- Laboratory sifting curve, respectively, for sand and large aggregate. Large meanings In the selection of sand for the concrete mix, it has its intercolored voidness V. p (%)
which is determined by the formula: ρ
n.P. - bulk density of sand, g / cm 3; ρ
- True sand density, g / cm 3; AT good sands Intergranarized void is 30 ... 38%, in ridiculated - 40 ... 42%. Large aggregate. A natural or artificial crushed stone or gravel with gravel with greens from 5 to 70mm is used as a major filler of the concrete mix. To ensure the optimal grain composition, a large aggregate is divided into fractions depending on the greatest greasing D. naib ; For D. naib \u003d 20mm large aggregate has two fractions: from 5 to 10 mm and from 10 to 20 mm; For D. naib \u003d 40mm - three fractions: from 5 to 10 mm; from 10 to 20 mm and from 20 to 40 mm; For D. naib \u003d 70mm - four fractions: from 5 to 10 mm; from 10 to 20 mm; from 20 to 40 mm; from 40 to 70 mm. A large influence on the consumption of cement in the preparation of a concrete mixture has an indicator of the inter-rigid emptiness of large aggregate V. p.KR (%),
which is determined with an accuracy of 0.01% by the formula: ρ
n.Kr. - average bulk density of large aggregate. ρ
k.KUK - The average density of large aggregate in the piece. An indicator of inter-rigid idle must be minimal. A smaller value can be obtained by selecting the optimal grain composition of large aggregate. The grain composition of the major aggregate is set as a result of sieving the dried large filler with a set of sieves with holes of 70; 40; twenty; ten; 5 mm taking into account its maximum D. naib and minimal D. naim Health. Crusheden - Usually an artificial loose material with unicreated rough grains, obtained by crushing rocks, large natural Gravel or artificial stones. To determine the suitability of rubble, you need to know: the true density of rock, the average density of rubble, the average bulk density of the rubble, relative interzernal voidness and humidity of rubble Gravel - loose natural material with retreal, smooth grains, formed in the process of physical weathelation of rocks. To gravel, the same requirements are imposed as a critic. Additives. The introduction of additives in cement, the solution or concrete mixture is simple and in a convenient way improve the quality of cement, mortar stone and concrete. Allowing to significantly improve not only their properties but also technical, performance indicators. Supplements are used in the production of binders, preparation of mortars and concrete mixtures. They allow you to change the quality of the concrete mix and the concrete itself; Impacting workability, mechanical strength, frost resistance, crack resistance, water resistance, waterproof, thermal conductivity, resistance to the environment. The main properties of the concrete mix are connected (the ability to maintain its homogeneity, not resolving during transportation, unloading), uniformity, water-holding ability (a significant role is played in the formation of a concrete structure, acquiring strength, waterproof and frost resistance), workability (the ability to quickly with minimum cost Energy acquire the necessary configuration and density, providing a high density concrete). The freshly prepared concrete mixture should be well mixed (homogeneous), suitable for transportation to the place of installation, taking into account weather conditions, while resisting water collection and stratification. The problem of designing and selecting the composition of the concrete mix includes the choice of necessary materials (binder and other components) and the establishment of their optimal quantity. On the basis of this, a concrete mixture with specified technological properties is obtained, as well as the most economical and durable concrete, which meets the design and operational requirements with the minimum possible consumption of cement. Consequently, the concrete mixture of the projected composition should have the non-lassity of the necessary convenientness, connectedness, and a concrete made from this mixture - the required properties: density, strength, frost resistance, water resistance. The easiest way to design the composition of the concrete mix is \u200b\u200bthe calculation of absolute volumes, which is based on that the prepared, laid and the compacted concrete mixture should not have emptiness. The design of the composition is performed using the current recommendations and regulatory documents In such a sequence: And the coefficient of the release of concrete:
Coefficient of the release of concrete β must be within 0.55 ... 0.75. The designed composition of the concrete mix is \u200b\u200bclarified on trials. They also check the mobility of the concrete mix. If the mobility of the concrete mixture is more required, then water and cement add to small portions, while maintaining a constant attitude C / C As long as the mobility of the concrete mix becomes equal to the specified one. If the mobility is greater than the sand and large aggregate (portions of 5% of the initial number), keeping the selected attitude to it. C / C. According to the results of test, adjustments are made by adjustments to the designed composition of the concrete mix, given that under production conditions, the sand and large aggregate are in a wet state, and a large aggregator has some water supply, consumption ( l. Document
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Abstract of dissertation.Introduction
Dear students we proceed to the study of the "General Materials" course. Lectures that will be read during this semester will help you understand the physicochemical essence of the structure and properties of various materials. You will learn why natural and artificially created materials have different thermal conductivity, mechanical and operational properties, as these properties are connected with each other, as in what limits you can change. Simultaneously with the study of these issues, you will more deeply get acquainted with the physical and chemical properties of elements, information about which is laid in the periodic system D.I. Mendeleeva. It is particularly note that the structure of atoms of chemical elements determines the structure and energy of the chemical bonds formed by them, which, in turn, underlie the entire complex of the properties of substances and materials. Only relying on the understanding of the chemical interaction of atoms, you can control the processes occurring in substances, and get given performance.
However, more important than the study of individual problems set out in lectures is the opportunity to combine the main provisions of physics, chemistry and applied scientific areas (thermophysics, mechanics) for a comprehensive understanding of the interaction of substances and their properties.
In lectures, the main attention is paid to the fundamental basics of materials science due to the fact that modern materials are aimed at obtaining materials with specified characteristics and serves as a basis for high-tech technologies of the XXI century.
Material called a substance having necessaryproperties complex for the specified function separatelyor in conjunction with other substances.
Modern materials are fully developed as a science in the second half of the 20th century, which was associated with a rapid increase in the role of materials in the development of technology, technology and construction. The creation of fundamentally new materials with specified properties, and on the basis of the most complex structures allowed humanity to achieve unprecedented success in atomic and space technology, electronics, information technologies, construction, etc. in a short time. We can assume that materials Science -this section scientific knowledgededicated to the properties of substances and their directional change in order to obtain materials with predetermined performance. It relies on the fundamental base of all sections of physics, chemistry, mechanics and related disciplines and includes the theoretical foundations of modern high-tech technologies for the preparation, processing and use of materials. The basis of materials science is knowledge about the processes occurring in materials under the influence of various factors, on their influence on the complex properties of the material, about the methods of control and management of them. Therefore, the material science and technology of materials are interrelated sections of knowledge.
The course of materials science and technology of building materials is served goalknowledge of the nature and properties of materials, methods for obtaining materials with specified characteristics for the most efficient use in construction.
Main goalsstudying courses:
Give an understanding of the physicochemical essence of phenomena taking place in the materials when exposed to various factors in the conditions of production and operation, and their influence on the properties of materials;
Establish the relationship between the chemical composition, structure and properties of materials;
Explore theoretical foundations and practice of implementing various methods for obtaining and processing materials providing high reliability and durability of building structures;
Give knowledge of basic groups of non-metallic materials, their properties and applications.
The lectures are revealed:
The bases of the interaction of atoms and molecules, which further explain the effect on the properties of the material of its chemical composition and processes of directional treatment;
The structure of the solid, defects of the crystal structure and their role in the formation of the properties of materials;
Heat transfer, mass and charge phenomena, constituting the essence of any technological process;
Theoretical foundations of obtaining amorphous structures of materials;
Elements of mechanics of elastic and plastic deformation and destruction of the material underlying the formation of the strength and reliability of modern building materials and structures, as well as methods of their tests;
So, the task of modern materials science is to obtain materials with predetermined properties.The properties of materials are determined by the chemical composition and structure that are the result of obtaining the material and its further processing. To develop materials and technologies, knowledge of physical and chemical phenomena and processes occurring in the material at various stages of its production, processing and operation, their prediction, description and management of them are necessary. Thus, knowledge of the theory is necessary to create managed technological processes, the result of which will be the material with well-defined values \u200b\u200bof the working properties.
The physicochemical properties of the substance are determined by the electronic structure of its atoms. The interactions of atoms are bound, first of all, with the interaction of their electronic shells. Therefore, when developing materials and processes of their preparation, it is necessary to clearly represent how different chemical elements give and receive electrons, as a change in the electronic state affects the properties of the elements.
Let's remember electronic structure atom.
Electronic structure atom
About two and a half thousand years, the ancient Greek philosopher Democritis expressed the idea that all the bodies around us consist of the smallest invisible and indivisible particles - atoms.
From the atoms, molecules are harvested from peculiar bricks: from the same atoms - molecules simple,substances, from atoms of various types - Molecules sophisticatedsubstances.
Already at the end of the nineteenth century, science found that atoms - particles are far from "indivisible", as the ancient philosophy represented, and, in turn, consist of even smaller and, if so we can express, even more simple particles. Currently, about three hundred elementary particles that are part of atoms have been proved with greater or less reliability.
To study chemical transformations in most cases, we sufficiently indicate three particles included in the atom: proton, electron andneutron.
The proton is a particle of mass conditionally adopted per unit (1/12 mass of carbon atom) and a single positive charge. Proton weight - 1,67252 x 10 -27 kg
The electron is a particle with a practically zero mass (1836 times less than a proton) and a single negative charge. Electron mass - 9,1091x10 -31 kg.
Neutron, is a particle with a mass of almost equal mass of the proton, but not having a charge (neutral). Neutron mass - 1.67474 x 10 -27 kg.
Contemporary science represents an atom arranged approximately as our triplers solar system: in the center of the atom is located nucleus(Sun), around which electrons rotate at a relatively large distance (as the planets around the sun). This "planetary" model of the atom, proposed in 1911 by Ernest Rutherford and in 1913, clarified by the postulates of Bora, has kept its value to the present.
In the kernel consisting of protons and neutrons and occupying a very small part of the volume of the atom, the main mass of the atom (the mass of electrons in the chemical calculations of atomic and molecular masses is usually not taken into account).
The number of protons in the kernel determines viewatom. In total, more than a hundred species of atoms are now open, which are presented in the table of elements below the numbers corresponding to the number of protons in the kernel.
The simplest atom contains only one proton in the core: it is a hydrogen atom. A more complex atom of helium has two protons in the core, the third (lithium) - three, etc. A certain kind of atom is called an element.
2. Building and properties of finishing materials
The inner structure of Motherpalov
Depending on the aggregate state and stability, solids may have a strictly ordered structure - crystalline, or unordered, chaotic structure - amorphous.
The nature of the particles in the nodes of the crystal lattice, and the prevailing forces of the interaction (chemical bonds) determine the nature of the crystal lattice: atomic with covalent bonds, molecular with van der Wales and hydrogen bonds, ion with ionic bonds, metallic with metal connections.
Atomic grille It consists of neutral atoms related to the covalent bonds. Substances with covalent bonds are distinguished by high hardness, refractory, irritability in water and in most other solvents. An example of atomic lattices are diamond and graphite. The energy of covalent bonds ranges from 600 to 1000 kJ / mol
Molecular grille Their molecules (I 2, CL 2, CO 2, etc.) are constructed, connected with each other with intermolecular or hydrogen bonds. Intermolecular bonds have a small amount of energy, no more than 10 × / mol; There are a slightly large amount of hydrogen bonds (20-80 kJ / mol), therefore substances with a molecular grille have low strength, low melting point, high volatility. Such substances do not conduct a current. Molecular lattice substances include organic materials, noble gases, some inorganic substances.
Ion grid.it is formed by atoms that are highly different from electronegativity. It is characteristic of alkaline and alkaline earth metal compounds with halogens. Ionic crystals may consist of polyatomic ions (for example, phosphates, sulfates, etc.). In such a lattice, each ion is surrounded by a certain number of its counterions. For example, in the crystal lattice NACL, each sodium ion is surrounded by six chlorine ions, and each chlorine ion is six sodium ions. Due to the non-directional and unsaturation of ionic communication, the crystal can be considered as a giant molecule, and the usual concept of the molecule loses its meaning. The substances with the ion lattice are characterized by a high melting point, low volatility, high strength and significant energy of the crystal lattice. These properties bring ionic crystals with atomic. The binding energy of the ion lattice is approximately equal to some sources less, the energy of a covalent lattice.
Metal latticesmetals form. In the nodes of the lattices there are metal ions, and valence electrons are delocalized throughout the crystal. Such crystals can be considered as one huge molecule with a single system of multicenter molecular orbitals. Electrons are located on the binding orbitals of the system, and the tearful orbital form form the conduction zone. Since the binding energy of binding and baking orbitals is close, electrons easily pass into the conductivity zone and move within the crystal, forming as an electronic gas. In tab. 3.1 As an example, the binding energies for crystals with different type Communication.
The ordered arrangement of particles in the crystal is maintained at large distances, and in the case of perfectly formed crystals - throughout the material. Such an order of structure of solid bodies is called far order.
Classification of materials
Solid materials are usually divided into three main groups. These are metals, ceramics and polymers. This division is based, first of all, on the peculiarities of the chemical structure and the atomic structure of the substance. Most materials can be quite unambiguously attributed to a particular group, although intermediate cases are also possible. In addition, it should be noted the existence of composites in which materials belonging to two or three of the listed groups are combined. The following will be given a brief description of various types of materials and their comparative characteristics are given.
Another type of materials are modern special (advanced) materials intended for use in high-tech (High-Tech) areas, such as semiconductors, bioferous materials, "smart" (smart) materials and substances used in nanotechnology.
Metals.
Materials belonging to this group include one or more metals (such as iron, aluminum, copper, titanium, gold, nickel), as well as certain non-metallic elements (for example, carbon, nitrogen or oxygen) in relatively small quantities.
Atoms in metals and alloys are located in a very perfect order. In addition, compared with ceramics and polymeric materials, the density of metals is relatively high.
As for mechanical properties, all these materials are relatively tough and durable. In addition, they have a certain plasticity (i.e., the ability to large deformations without destruction), and the resistance to the destruction, which ensured their widespread use in a variety of structures.
AT metal materials There are many delocalized electrons, i.e. electrons not related to certain atoms. It is the presence of such electrons that many properties of metals are directly explained. For example, metals are exceptionally good conductors for electric current and heat. They are impenetrable for visible light. Polished metal surfaces glitter. In addition, some metals (for example, iron, cobalt and nickel) have desirable to use magnetic properties.
CERAMICS
Ceramics is a group of materials that occupy an intermediate position between metals and non-metallic elements. how general ruleThe ceramics class includes oxides, nitrides and carbides. For example, some of the most popular ceramics species consist of aluminum oxide (Al2O3), silicon dioxide (SiO2), silicon nitride (Si3N4). In addition, among those substances that many are called traditional ceramic materials include various clays (in particular those that go to the manufacture of porcelain), as well as concrete and glass. As for mechanical properties, ceramics are relatively tough and durable materialscomparable to these characteristics with metals. In addition, typical types of ceramics are very solid. However, ceramics exclusively fragile material (almost complete absence of plasticity) and badly resist damage. All typical types of ceramics do not conduct heat and electric current (that is, their electrical conductivity is very low).
Ceramics are characterized by higher resistance to high temperatures and harmful environmental impacts. As for their optical properties, ceramics can be transparent, translucent or completely opaque material, and some oxides, for example, iron oxide (Fe2O3) have magnetic properties.
Composites
Composites are a combination of two (or more) of individual materials belonging to various classes of substances listed above, i.e. Metals, ceramics and polymers. The purpose of creating composites was the desire to achieve such a combination of properties of various materials that cannot be obtained for individual components, as well as ensure the optimal combination of their characteristics. There is a large number of different composites that are obtained by combining metals, ceramics and polymers. Moreover, some natural materials Also are composites, for example, this tree and bone. However, most composites that are considered in the present book are materials derived from synthetic materials.
One of the most popular and acquaintances of all composite materials is fiberglass. This material is short glass fibers placed in a polymer matrix, usually in epoxy or polyester resin. Glass fibers have high strength and rigidity, but they are fragile. At the same time, the polymer matrix is \u200b\u200bplastic, but its strength is low. The combination of these substances leads to a relatively rigid and high-strength material, which, nevertheless, has sufficient plasticity and flexibility.
Another example of a technologically important composite is carbon fiber - polymers reinforced by carbon fibers (CFRP). In these materials, carbon fibers are placed in the polymer matrix. Materials of this type are tougher and more durable compared to fiberglass, but at the same time more expensive. Crawlestics are used in aerospace technology, as well as in the manufacture of high-quality sports equipment, such as bicycles, golf clubs, tennis rackets, skis and snowboards.
Progressive materials
Materials that are intended for use in high-tech products (High-tech) sometimes conditionally determine the term "progressive" materials. Under high technologies are usually due to the device or product, the work of which is based on the use of complex modern principles. Such products include various electronic equipment, in particular digital video audio cameras, CD / DVD players, computers, optical fiber systems, as well as space satellites, aerospace products and rocket technologies.
Progressive materials are essentially usually typical substance discussed above, but with improved properties, but also new materials with outstanding characteristics. These materials can be metals, ceramics or polymers, but their cost is usually very high. The progressive materials also include semiconductors, biomaterials and substances that we call "the materials of the future". These are the so-called "smart" materials and products of nanotechnologies, which are intended, for example, for the manufacture of lasers, integrated circuits, magnetic information custodians, displays on liquid crystals and optical fibers.
Semiconductors
Semiconductors for electrical properties occupy an intermediate position between electrically conductive materials (metals and metal alloys) and insulators (ceramics and polymers). In addition, the electrical characteristics of semiconductors are extremely sensitive to the presence of minimum amounts of foreign atoms, the concentration of which needs to be monitored up to the level of very small regions. The creation of semiconductor materials made it possible to develop integrated systems that produced a revolution in electronics and computer technician (even if not mentioning changes in our life) for the past three decades.
Biomaterials
Biomaterials are used to create implants for human body, which are designed to replace patients or destroyed organs or tissues. Materials of this type should not be isolated toxic substances and must be compatible with human tissues (i.e. should not cause reaction reactions). All listed types of substances are metals, ceramics, polymers and semiconductors - can be used as biomaterials. As an example, some biomaterials can be brought to the manufacture of artificial hip joints.
Materials of the Future
"Smart" (or intellectual) materials are called a group of new artificially developed substances that have a significant impact on many modern technologies. The definition of "smart" means that these materials are able to feel changes in the environment and respond to these changes in advance in a certain way - the quality inherent in living organisms. The concept of "smart" materials was also distributed to complex systems, built from both "smart" and traditional substances.
Some types of sensors (recognizing incoming signals) can be used as components of smart materials (or systems), as well as actuators (activators) that play the role of responding and adaptive devices. The latter can be used to change the form, position, own frequencies or mechanical characteristics as an answer to the change in temperature, illumination intensity, electrical or magnetic fields.
Four types are usually used as activators: these are alloys with memory change, piezoelectric types of ceramics, magnetostriction materials and electromagnetic / electromagnetic liquids.
Alloys "with memory" are metals that, after deformation, return to the original form, if the temperature has changed.
Piezoelectric types of ceramics are expanding and compressed in response to a change in the electric field (or voltage); If their dimensions change, it leads to the excitation of the electrical signal. The behavior of magnetostriction materials is similar to the reaction of piezoelectrics, but only as a reaction to the change magnetic field. As for electro-and magnetoreological fluids, these are such environments that undergo huge viscosity changes in response to a change in the electrical or magnetic field, respectively.
Materials / devices used as sensors may be optical fibers, piezoelectrics (they include some polymers) and microelectromechanical devices, MEMS abbreviation.
As an example of "smart" devices, you can bring a system used in helicopters in order to reduce the noise in the cabin, created when the blades are rotated. Piezoelectric sensors built into the blades track voltages and deformations; The signal is transmitted from these sensors to the actuator, which, using a computer, generates "antishe", quenching the sound from the operation of the helicopter screws.
Nanotechnology materials
Up until recently, the generally accepted procedure for work in the field of chemistry and physics of materials was that very large and complex structures were first studied, and then the studies were studied to analyze smaller fundamental blocks that constitute these structures. This approach was sometimes called "top-down". However, with the development of scanning microscopy technology, which allowed to observe individual atoms and molecules, it turned out to be possible to manipulate atoms and molecules in order to create new structures, and thereby getting new materials that are based on the elements of the atomic level of sizes (the so-called "material design "). These opportunities carefully collect atoms discovered the prospects to create materials with mechanical, electrical, magnetic and other properties that would be unattainable when using other methods. We will call this approach "bottom-up", and the study of the properties of such new materials is engaged in nanotechnology, where the prefix "Nano" means that the size of the structural elements is the magnitude of the nanometer order (ie 10-9 m). Usually, we are talking On the structural elements with dimensions less than 100 nm, which is equivalent to approximately 500 diameters of the atom.
One example of the materials of the type under consideration is carbon nanotubes. In the future, undoubtedly, we will be able to find more and more areas in which the advantages of nanotechnology materials will be shown.
The need to create new materials
Despite the fact that over the past few years, huge progress has been made in the field of materials science and technology for the use of materials, there is still a need to create even more advanced and specialized materials, as well as in assessing the relationship between the production of such materials and its influence on the environment. On this issue, it is necessary to give some comments to outline possible prospects in this area.
The creation of nuclear power offers certain promises of the future, but there are numerous problems related to the development of new materials that are necessary at all stages - from the fuel accommodation system in the reactor to storing radioactive waste.
Large energy costs are associated with transportation. Reducing the weight of transporting devices (cars, airplanes, trains, etc.), as well as an increase in temperature at which engines work will contribute to more efficient energy consumption. This requires to create high-strength light engineering materials, as well as materials that can operate in elevated temperatures.
Further, there is a generally accepted need for new economically reasonable sources of energy, as well as in more efficient use of existing sources. There is no doubt that materials with the necessary characteristics play a huge role in the development of this direction. For example, the possibility of direct transformation of solar energy into electric current was demonstrated. Currently, solar panels are quite complex and expensive devices. There is no doubt that new relatively cheap technological materials should be created, which should be more effective in the implementation of solar energy.
Another very attractive and quite real example in energy conversion technology is hydrogen fuel cells, which also possess the advantage that they do not pollute the environment. Currently, the use of this technology in electronic devices is only beginning; In the future, such elements can be used as power plants in cars. To create more efficient fuel cells, new materials are needed, and new catalysts are needed for hydrogen production.
To maintain the quality of the environment at the required level, we need to control the composition of air and water. Different materials are used to control pollution. In addition, it is necessary to improve the methods of processing and cleaning materials in order to reduce environmental pollution, i.e. There is a challenge to create less waste and less harming us around us during mining. It should also be taken into account that in the production of some materials toxic substances are formed, so it should be taken into account possible damage to ecology from resetting such waste.
Many materials we use receive from irrepustible resources, i.e. Sources that cannot be regenerated. This applies, for example, to polymers, primary raw materials for which oil is oil, and to some metals. These irreplaceable resources are gradually exhausted. From here there is a need to: 1) the detection of new sources of these resources; 2) the creation of new materials with properties similar to existing, but less damage to environmental; 3) strengthening the role of recycling processes and, in particular, the development of new technologies that allow recycling. As a result, all this is needed. economic Evaluation Not only production, but also the accounting of environmental factors, so it turns out to be necessary to analyze the entire life cycle of the material - "from the cradle to the grave" - \u200b\u200band the production process as a whole.
Casting- This is a way to manufacture a workpiece or product by filling the cavity of a given configuration with a liquid metal, followed by its solidification. Preparation or product obtained by casting, is called casting.
Foundry- the main procurement base of all the directions of mechanical engineering. In many cases, casting is the only reasonable way to obtain billets of complex form:. Cast blanks are the cheapest, and often have a minimum allowance for mechanical processing.
Casting B. shell forms.
The foundry here is a shell of a thickness of 6-10 mm, made of a refractory base material (filler) and a synthetic resin as a binder. The principle of obtaining shells is laid in the properties of a binder, capable of irreversibly cured when heated. As a refractory foundation widely used quartz sand. The binding material is phenol formaldehyde synthetic thermosetting resins. The casting in the shell forms receive castings of increased accuracy, better surface quality than when casting into sandy forms. The process is extremely productive and easy to mechanize.
List of used literature
Bartashevich A.A. Materials Science. - Rostov N / D: Phoenix, 2008.
Vishnevetsky Yu.T. Materials science for technical colleges: textbook. - M.: Dashkov and Ko, 2008.
Patchin V.N. Reference manual for materials science (metalworking): studies. Manual for NGOs. - M.: Academy, 2007.
Materials Science: Textbook for universities. / Ed. Arzamasova B.N. - M.: MSTU them. Bauman, 2008.
Materials Science: Textbook for SPO. / Adakin A.M. and others. Ed. Solomentseva Yu.M. - M.: Higher. Shk., 2006.
Materials Science: Textbook for SPO. / Ed. Baitienko V.T. - M.: Infra-M, 2006.
Sailors O.S. Materials Science: Textbook for SPO. - M.: Academy, 2008.
Basics of materials science (metalworking): studies. Manual for NGOs. / Patchin V.N. - M.: Academy, 2008.