carbon tubes. "Carbon" future of electronics

Under the security of an automated system, we mean the degree of adequacy of the information protection mechanisms implemented in it to the risks existing in a given operating environment associated with the implementation of threats to information security.

Information security threats are traditionally understood as the possibility of violation of such properties of information as confidentiality, integrity and availability.

The main ways to ensure information security include:

Legislative (laws (Law of July 21, 1993 N 5485-1 "On State Secrets"), GOSTs ("GOST R 50922-96 "Information Protection"), codes (Article 272 of the Criminal Code of the Russian Federation on NSD), the doctrine of information security and Constitution of the Russian Federation)

Moral and ethical

Organizational (administrative)

Technical

Software

Organizational (administrative) means of protection are organizational, technical and organizational and legal measures carried out in the process of creating and operating telecommunications equipment to ensure the protection of information. Organizational measures cover all structural elements of equipment at all stages of their life cycle

(construction of premises, system design, installation and commissioning of equipment, testing and operation).

Modern technologies for protecting corporate networks.

1) Firewalls

ME is a local or functionally distributed software (software and hardware) tool (complex) that implements control over information entering an automated system and / or leaving an automated system. ME is the main name defined in the RD of the State Technical Commission of the Russian Federation for this device. There are also common names firewall and firewall (English wall of fire). By definition, the DOE serves as a checkpoint at the border of two

networks. In the most common case, this boundary lies between an organization's internal network and an external network, usually the Internet. However, in the general case, MEs can be used to delimit the internal subnets of an organization's corporate network.

ME tasks are:

Control of all traffic ENTERING the internal corporate network

Control of all traffic OUTCOMING from the internal corporate network

The control of information flows consists in their filtering and transformation in accordance with a given set of rules. Since in modern MEs filtration can be carried out at different

levels of the reference model of interaction of open systems (EMOS, OSI), it is convenient to represent the ME in the form of a system of filters. Each filter, based on the analysis of the data passing through it, takes

An integral function of the ME is logging information exchange. Logging allows the administrator to identify suspicious activities, errors in the DOE configuration and make a decision to change the DOE rules.

2) Intrusion detection systems

A typical architecture of an intrusion detection system includes the following components:

1. Sensor (means of collecting information);

2. Analyzer (information analysis tool);

3. Means of response;

4. Controls.

Network sensors intercept network traffic, host sensors use OS, DBMS and application event logs as sources of information. Information about events can also be received by the host sensor directly from the OS kernel, firewall or application. The analyzer, located on the security server, centrally collects and analyzes information received from sensors.

Response tools can be placed on network monitoring stations, ME, servers and LAN workstations. A typical attack response set includes alerting

security administrator (by means of e-mail, displaying a message on the console or sending it to a pager), blocking network sessions and user registration records in order to immediately stop attacks, as well as logging the actions of the attacking side.

Secure virtual network VPN called the union of local networks and individual computers through an open external information transmission medium into a single virtual corporate network that ensures the security of circulating data.

When you connect a corporate LAN to an open network, you experience security threats two main types:

Unauthorized access to corporate data in the process of their transmission over an open network;

Unauthorized access to the internal resources of a corporate local network, obtained by an attacker as a result of unauthorized entry into this network.

The protection of information in the process of transmission over open communication channels is based on the performance of the following main functions:

Authentication of interacting parties;

Cryptographic closing (encryption) of transmitted data;

Checking the authenticity and integrity of the delivered information.

Ways to protect information in an enterprise, as well as ways to extract it, are constantly changing. New offers from companies providing information security services appear regularly. Of course, there is no panacea, but there are several basic steps in building the protection of an enterprise information system that you definitely need to pay attention to.

Many of you are probably familiar with the concept of deep protection against hacking an information network. Its main idea is to use several levels of defense. This will at least minimize the damage associated with a possible violation of the security perimeter of your information system.
Next, we will consider the general aspects of computer security, and also create a checklist that serves as the basis for building the basic protection of an enterprise information system.

1. Firewall (firewall, firewall)

A firewall or firewall is the first line of defense that meets intruders.
By the level of access control, the following types of firewall are distinguished:

• In the simplest case, network packets are filtered according to established rules, i.e. based on source and destination addresses of network packets, network port numbers;
• A firewall operating at the session level (stateful). It monitors active connections and drops fake packets that violate TCP/IP specifications;
• Firewall operating at the application layer. Performs filtering based on parsing the application data passed within the package.

Increased attention to network security and the development of e-commerce has led to the fact that all more users use encryption of connections (SSL, VPN) for their protection. This greatly complicates the analysis of traffic passing through firewalls. As you might guess, malware developers use the same technologies. Viruses that use traffic encryption have become almost indistinguishable from legitimate user traffic.

2. Virtual Private Networks (VPNs)

Situations when an employee needs access to company resources from public places(Wi-Fi at the airport or hotel) or from home (the home network of employees is not controlled by your administrators), are especially dangerous for corporate information. To protect them, you just need to use encrypted VPN tunnels. Any access to remote desktop (RDP) directly without encryption is out of the question. The same applies to the use of third-party software: Teamviewer, Aammy Admin, etc. to access the work network. Traffic through these programs is encrypted, but passes through the servers of the developers of this software that are not under your control.

The disadvantages of VPNs include the relative complexity of deployment, additional costs for authentication keys, and an increase in the bandwidth of the Internet channel. Authentication keys can also be compromised. Stolen mobile devices of the company or employees (laptops, tablets, smartphones) with pre-configured VPN connection settings can become a potential hole for unauthorized access to company resources.

3. Intrusion detection and prevention systems (IDS, IPS)

Intrusion detection system (IDS - English: Intrusion Detection System) is a software or hardware tool designed to detect the facts of unauthorized access to a computer system (network), or unauthorized control of such a system. In the simplest case, such a system helps detect network port scans of your system or attempts to enter the server. In the first case, this indicates the attacker's initial reconnaissance, and in the second case, attempts to hack into your server. You can also detect attacks aimed at escalation of privileges in the system, unauthorized access to important files, as well as the actions of malicious software. Advanced network switches allow you to connect an intrusion detection system using port mirroring or through traffic taps.

Intrusion Prevention System (IPS) is a software or hardware security system that actively blocks intrusions as they are detected. If an intrusion is detected, suspicious network traffic can be automatically blocked, and a notification about this is immediately sent to the administrator.

4. Antivirus protection

Antivirus software is the primary line of defense for most businesses today. According to research company Gartner, the size of the anti-virus software market in 2012 amounted to $19.14 billion. The main consumers are the segment of medium and small businesses.

First of all, anti-virus protection is aimed at client devices and workstations. Business versions of antiviruses include centralized management functions for transferring antivirus database updates to client devices, as well as the ability to centrally configure security policies. The range of antivirus companies includes specialized solutions for servers.
Given that most malware infections result from user actions, antivirus packages offer comprehensive protection options. For example, protection of e-mail programs, chats, checking sites visited by users. In addition, antivirus packages increasingly include a software firewall, proactive defense mechanisms, and spam filtering mechanisms.

5. Whitelisting

What are "white lists"? There are two main approaches to information security. The first approach assumes that by default the operating system is allowed to run any applications, if they are not previously blacklisted. The second approach, on the contrary, assumes that only those programs that were previously included in the "white list" are allowed to run, and all other programs are blocked by default. The second approach to security is of course more preferable in the corporate world. Whitelists can be created both using the built-in tools of the operating system, and using third-party software. Antivirus software often offers this feature as part of its package. Most antivirus applications that offer whitelisting filtering allow for a very quick initial setup with minimal user attention.

However, there may be situations in which the dependencies of the whitelisted program files were not correctly identified by you or the antivirus software. This will cause the app to crash or install incorrectly. In addition, whitelists are powerless against attacks that exploit document processing vulnerabilities by whitelisted programs. You should also pay attention to the weakest link in any defense: the employees themselves, in a hurry, can ignore the warning of antivirus software and whitelist malware.

6. Spam filtering

Spam mailings are often used to carry out phishing attacks that are used to introduce a Trojan or other malware into a corporate network. Users who process a large amount of email on a daily basis are more susceptible to phishing emails. Therefore, the task of the company's IT department is to filter out the maximum amount of spam from the general email flow.

The main ways to filter spam:

• Specialized Spam Filtering Service Providers;
• Spam filtering software on own mail servers;
• Specialized hardware solutions deployed in a corporate data center.

7. Software support up to date

Timely software updates and application of current security patches - important element protection of the corporate network from unauthorized access. Software vendors usually do not provide complete information about a newly found security hole. However, attackers have enough general description vulnerabilities in order to write software to exploit this vulnerability just a couple of hours after the publication of a description of a new hole and a patch to it.
Actually it's enough a big problem for small and medium-sized businesses, since a wide range of software products from different manufacturers is usually used. Often, updates to the entire software fleet are not given due attention, and this is practically an open window in the enterprise security system. Currently, a large number of software updates itself from the manufacturer's servers and this removes part of the problem. Why a part? Because the manufacturer's servers can be hacked and, under the guise of legal updates, you will receive fresh malware. And also the manufacturers themselves sometimes release updates that disrupt the normal operation of their software. This is unacceptable in critical areas of the business. To prevent such incidents, all received updates, firstly, must be applied immediately after their release, and secondly, they must be thoroughly tested before application.

8. Physical security

The physical security of a corporate network is one of the critical factors which is difficult to overestimate. Having physical access to a network device, an attacker, in most cases, will easily gain access to your network. For example, if there is physical access to the switch and the network does not filter MAC addresses. Although MAC filtering will not save you in this case. Another problem is the theft or neglect of hard drives after being replaced in a server or other device. Considering that the passwords found there can be decrypted, server cabinets and rooms or boxes with equipment must always be securely protected from intruders.

We have only touched on some of the most common aspects of security. It is also important to pay attention to user training, periodic independent information security audits, and the creation and enforcement of a sound information security policy.
Please note that corporate network protection is sufficient difficult topic, which is constantly changing. You must be sure that the company does not depend on just one or two lines of defense. Always try to follow up-to-date information and fresh solutions in the information security market.

Take advantage of the reliable protection of the corporate network as part of the service "maintenance of computers for organizations" in Novosibirsk.

This is the result of a survey of more than 1,000 heads of IT departments of large and medium-sized European companies, commissioned by Intel. The purpose of the survey was to identify a problem that is of greater concern to industry professionals. The answer was quite expected, more than half of the respondents called the problem of network security, a problem that needs to be addressed immediately. Other results of the survey can also be called quite expected. For example, the network security factor is leading among other problems in the field of information technologies; its importance has increased by 15% compared to the situation that existed five years ago.
According to the survey, over 30% of their time is spent by highly qualified IT specialists on security issues. The situation in large companies (those with more than 500 employees) is even more worrisome - about a quarter of respondents spend half their time on these issues.

Balance of threats and protection

Alas, the issue of network security is inextricably linked with the fundamental technologies used in modern telecommunications. It just so happened that when developing a family of IP protocols, priority was given to the reliability of the network as a whole. At the time of the emergence of these protocols, network security was provided in completely different ways, which are simply unrealistic to use in the conditions of the Global Network. You can loudly complain about the shortsightedness of the developers, but it is almost impossible to radically change the situation. Now you just need to be able to protect yourself from potential threats.
The main principle in this skill should be balance between potential threats to network security and the level of protection needed. A commensurability should be ensured between the cost of security and the cost of possible damage from realized threats.
For a modern large and medium-sized enterprise, information and telecommunication technologies have become the basis of doing business. Therefore, they turned out to be the most sensitive to the impact of threats. The larger and more complex the network, the more effort it requires to protect it. At the same time, the cost of creating threats is orders of magnitude less than the cost of neutralizing them. This state of affairs forces companies to carefully weigh the consequences of possible risks from various threats and choose the appropriate ways to protect against the most dangerous ones.
Currently, the greatest threats to corporate infrastructure are actions associated with unauthorized access to internal resources and blocking the normal operation of the network. There are a fairly large number of such threats, but each of them is based on a combination of technical and human factors. For example, the penetration of a malicious program into a corporate network can occur not only as a result of the network administrator's neglect of security rules, but also due to excessive curiosity of a company employee who decides to use a tempting link from email spam. Therefore, one should not hope that even the best technical solutions in the field of security will become a panacea for all ills.

UTM class solutions

Security is always relative concept. If there is too much of it, then the use of the system itself, which we are going to protect, becomes noticeably more complicated. Therefore, a reasonable compromise becomes the first choice in ensuring network security. For medium-sized enterprises, by Russian standards, such a choice may well help to make class-leading solutions. UTM (Unified Threat Management or United Threat Management), positioned as multifunctional network and information security devices. At their core, these solutions are software and hardware systems that combine the functions different devices: firewall (firewall), network intrusion detection and prevention systems (IPS), as well as anti-virus gateway (AV) functions. Often, these complexes are assigned to solve additional tasks, such as routing, switching, or supporting VPN networks.
Often, UTM solution providers offer to use them in small businesses. Perhaps this approach is partly justified. But still, it is easier and cheaper for small businesses in our country to use the security service from their Internet provider.
Like any universal solution, UTM equipment has its pros and cons.. The former include cost savings and implementation time compared to organizing protection of a similar level from separate security devices. Also, UTM is a pre-balanced and tested solution that can solve a wide range of security problems. Finally, solutions of this class are not so demanding on the level of qualification of technical personnel. Any specialist can easily handle their configuration, management and maintenance.
The main disadvantage of UTM is the fact that any functionality of a universal solution is often less efficient than the same functionality of a specialized solution. That is why when high performance or a high degree of security is required, security specialists prefer to use solutions based on the integration of individual products.
However, despite this minus, UTM solutions are becoming in demand by many organizations that differ greatly in scale and type of activity. According to Rainbow Technologies, such solutions were successfully implemented, for example, to protect the server of one of the Internet stores of household appliances, which was subjected to regular DDoS attacks. Also, the UTM solution made it possible to significantly reduce the volume of spam in postal system one of the automotive holdings. In addition to solving local problems, I have experience in building security systems based on UTM solutions for a distributed network covering the central office of a brewing company and its branches.

UTM manufacturers and their products

The Russian market for UTM class equipment is formed only by offers from foreign manufacturers. Unfortunately, none of the domestic manufacturers has yet been able to offer own decisions in this class of equipment. The exception is software solution Eset NOD32 Firewall, which, according to the company, was created by Russian developers.
As already noted, in the Russian market, UTM solutions may be of interest mainly to medium-sized companies with up to 100-150 workplaces in their corporate network. When selecting UTM equipment for presentation in the review, the main selection criterion was its performance in various operating modes, which could provide a comfortable user experience. Often manufacturers list performance specifications for Firewall, IPS Intrusion Prevention, and AV Antivirus modes.

Decision Check Point is called UTM-1 Edge and is a unified security appliance that combines a firewall, an intrusion prevention system, an anti-virus gateway, as well as VPN and remote access building tools. The firewall included in the solution controls work with a large number of applications, protocols and services, and also has a mechanism for blocking traffic that clearly does not fit into the category of business applications. For example, instant messaging (IM) and peer-to-peer (P2P) traffic. The antivirus gateway allows you to monitor malicious code in email messages, FTP and HTTP traffic. At the same time, there are no restrictions on the size of files and decompression of archive files is carried out "on the fly".
The UTM-1 Edge solution has advanced VPN capabilities. OSPF dynamic routing and VPN client connectivity are supported. The UTM-1 Edge W comes with a built-in IEEE 802.11b/g WiFi hotspot.
For large deployments, UTM-1 Edge seamlessly integrates with Check Point SMART to simplify security management.

Cisco traditionally pays increased attention to network security issues and offers a wide range of necessary devices. For the review, we decided to choose a model Cisco ASA 5510, which is focused on ensuring the security of the corporate network perimeter. This equipment is part of the ASA 5500 series, which includes modular protection systems of the UTM class. This approach allows you to adapt the security system to the specifics of the functioning of the network of a particular enterprise.
Cisco ASA 5510 comes in four main kits - firewall, VPN building tools, intrusion prevention system, as well as virus and spam protection tools. The solution includes additional components such as the Security Manager system to form a management infrastructure for an extensive corporate network, and the Cisco MARS system, designed to monitor the network environment and respond to security breaches in real time.

Slovak Eset company supplies software package Eset NOD32 Firewall class UTM, which includes, in addition to the functions of a corporate firewall, the Eset NOD32 anti-virus protection system, mail (antispam) and web traffic filtering tools, IDS and IPS network attack detection and prevention systems. The solution supports the creation of VPN networks. This complex is based on a server platform running Linux. The software part of the device was developed domestic company Leta IT, controlled by the Russian representative office of Eset.
This solution allows you to control network traffic in real time, filtering content by categories of web resources is supported. Provides protection against DDoS attacks and blocks port scanning attempts. The Eset NOD32 Firewall solution includes support for DNS, DHCP servers and bandwidth change control. Traffic of mail protocols SMTP, POP3 is controlled.
This solution also includes the ability to create distributed corporate networks using VPN connections. At the same time, it supports various modes networking, authentication and encryption algorithms.

Fortinet offers a whole family of devices FortiGate class UTM, positioning its solutions as capable of providing network protection while maintaining a high level of performance, as well as reliable and transparent operation of enterprise information systems in real time. For review, we have chosen model FortiGate-224B, which is designed to protect the perimeter of a corporate network with 150 - 200 users.
FortiGate-224B hardware includes firewall functionality, VPN server, web traffic filtering, intrusion prevention systems, as well as anti-virus and anti-spam protection. This model has built-in Layer 2 LAN switch interfaces and WAN interfaces, eliminating the need for external routing and switching devices. For this, routing via RIP, OSPF and BGP protocols is supported, as well as user authentication protocols before providing network services.

SonicWALL Company offers a wide range of UTM devices, from which the solution is included in this review NSA 240. This equipment is the youngest model in the line, focused on the use as a system for protecting the corporate network of a medium-sized enterprise and branches of large companies.
The basis of this line is the use of all means of protection against potential threats. These are firewall, intrusion protection system, virus protection gateways and spyware. There is a filtering of web-traffic by 56 categories of sites.
As one of the highlights of its solution, SonicWALL notes the technology of deep scanning and analysis of incoming traffic. To eliminate performance degradation, this technology uses parallel data processing on a multiprocessor core.
This equipment supports VPN, has advanced routing capabilities and supports various network protocols. Also, the solution from SonicWALL is able to provide high level security when servicing VoIP traffic over SIP and H.323 protocols.

From the product line watch guard company solution was selected for review Firebox X550e, which is positioned as a system with advanced functionality to ensure network security and is focused on use in networks of small and medium enterprises.
The UTM class solutions of this manufacturer are based on the use of the principle of protection against mixed network attacks. To do this, the equipment supports a firewall, an attack prevention system, anti-virus and anti-spam gateways, web resource filtering, as well as a system to counter spyware.
This equipment uses the principle of joint protection, according to which network traffic checked by a certain criterion at one protection level will not be checked by the same criterion at another level. This approach ensures high performance of the equipment.
Another advantage of its solution, the manufacturer calls support for Zero Day technology, which ensures the independence of security from the presence of signatures. This feature is important when new types of threats appear, for which effective countermeasures have not yet been found. Typically, the "window of vulnerability" lasts from several hours to several days. When using Zero Day technology, the probability of negative consequences of the vulnerability window is significantly reduced.

ZyXEL Company offers its own UTM-class firewall solution for corporate networks with up to 500 users. This is ZyWALL 1050 solution is designed to build a network security system that includes full-fledged virus protection, intrusion prevention and support for virtual private networks. The device has five Gigabit Ethernet ports that can be configured for use as WAN, LAN, DMZ, and WLAN interfaces depending on the network configuration.
The device supports the transmission of VoIP application traffic over SIP and H.323 protocols at the firewall and NAT levels, as well as the transmission of packet telephony traffic in VPN tunnels. This ensures the functioning of mechanisms to prevent attacks and threats for all types of traffic, including VoIP traffic, the operation of an anti-virus system with a complete database of signatures, content filtering by 60 categories of sites and spam protection.
The ZyWALL 1050 solution supports a variety of private network topologies, VPN concentrator mode, and the consolidation of virtual networks into zones with uniform security policies.

Main characteristics of UTM

Expert opinion

Dmitry Kostrov, Project Director of the Directorate for Technological Protection of the Corporate Center of MTS OJSC

The scope of UTM solutions mainly extends to companies belonging to small and medium-sized businesses. The very concept of Unified Threat Management (UTM), as a separate class of equipment for protecting network resources, was introduced by the international agency IDC, according to which UTM solutions are multifunctional software and hardware systems that combine the functions of different devices. This is typically a firewall, VPN, intrusion detection and prevention systems, as well as anti-virus and anti-spam gateway and URL filtering functions.
In order to achieve truly effective protection, the device must be multi-layered, active and integrated. At the same time, many manufacturers of protective equipment already have a fairly wide range of products related to UTM. Sufficient ease of deployment of systems, as well as obtaining an all-in-one system, makes the market for these devices quite attractive. The total cost of ownership and return on investment for these devices seem to be very attractive.
But this UTM solution is like a "Swiss knife" - there is a tool for every occasion, but you need a real drill to punch a hole in the wall. There is also a possibility that the appearance of protection against new attacks, signature updates, etc. will not be as fast, in contrast to the support of individual devices that are in the "classic" scheme for protecting corporate networks. There is also the problem of a single point of failure.

Information systems in which data transmission facilities belong to one company are used only for the needs of this company, it is customary to call an enterprise-wide network a corporate computer network (CN). CS is an internal private network of an organization that combines the computing, communication and information resources of this organization and is designed to transfer electronic data, which can be any information. Thus, based on the above, we can say that a special policy is defined inside the CS that describes the hardware and software tools, rules for getting users to network resources, rules for managing the network, controlling the use of resources and further developing the network. An enterprise network is a network of an individual organization.

A somewhat similar definition can be formulated based on the concept of a corporate network given in the work of Olifer V.G. and Olifer N.D. “Computer networks: principles, technologies, protocols”: any organization is a set of interacting elements (subdivisions), each of which can have its own structure. The elements are interconnected functionally, i.e. they perform certain types of work within the framework of a single business process, as well as information, exchanging documents, faxes, written and oral orders, etc. In addition, these elements interact with external systems, and their interaction can also be both informational and functional. And this situation is true for almost all organizations, no matter what type of activity they are engaged in - for a government agency, a bank, an industrial enterprise, a commercial firm, etc.

This general view of the organization allows us to formulate some general principles building corporate information systems, i.e. information systems throughout the organization.

Corporate network - a system that provides information transfer between various applications used in a corporate system. A corporate network is any network that operates over the TCP/IP protocol and uses Internet communication standards, as well as service applications that provide data delivery to network users. For example, a business may create a Web server to publish announcements, production schedules, and other business documents. Employees access the necessary documents using Web browsers.

Corporate Web servers can provide users with services similar to those of the Internet, such as working with hypertext pages (containing text, hyperlinks, graphics and sounds), providing the necessary resources for Web clients, and accessing databases. In this guide, all publishing services are referred to as "Internet services" regardless of where they are used (on the Internet or on a corporate network).

The corporate network, as a rule, is geographically distributed, i.e. uniting offices, divisions and other structures located at a considerable distance from each other. The principles by which a corporate network is built are quite different from those used to create a local network. This limitation is fundamental, and when designing a corporate network, all measures should be taken to minimize the amount of transmitted data. Otherwise, the corporate network should not impose restrictions on which applications and how they process the information transferred over it. A characteristic feature of such a network is that it operates equipment of various manufacturers and generations, as well as heterogeneous software that is not initially focused on joint data processing.

To connect remote users to the corporate network, the simplest and most affordable option is to use a telephone connection. Where possible, ISDN networks may be used. To unite network nodes, in most cases, global data networks are used. Even where it is possible to lay leased lines (for example, within one city), the use of packet switching technologies makes it possible to reduce the number of required communication channels and, which is important, ensure system compatibility with existing global networks.

Connecting your corporate network to the Internet is justified if you need access to the appropriate services. In many works, there is an opinion about connecting to the Internet: It is worth using the Internet as a data transmission medium only when other methods are not available and financial considerations outweigh the requirements of reliability and security. If you will use the Internet only as a source of information, it is better to use the technology "connection on demand" (dial-on-demand), ie. in such a way of connection, when the connection with the Internet node is established only on your initiative and for the time you need. This dramatically reduces the risk of unauthorized entry into your network from outside.

To transfer data within a corporate network, it is also worth using virtual channels of packet switching networks. The main advantages of this approach are versatility, flexibility, security.

As a result of studying the structure of information networks (IS) and data processing technology, the concept of information security of IS is being developed. The concept reflects the following main points:

• 1) Networking organization
• 2) existing threats to the security of information, the possibility of their implementation and the expected damage from this implementation;
• 3) organization of information storage in IS;
• 4) organization of information processing;
• 5) regulation of personnel access to this or that information;
• 6) the responsibility of personnel for ensuring safety.

Developing this topic, based on the concept of IS information security given above, a security scheme is proposed, the structure of which must satisfy the following conditions:

Protection against unauthorized penetration into the corporate network and the possibility of information leakage through communication channels.

Differentiation of information flows between network segments.

Protection of critical network resources.

Cryptographic protection information resources.

For a detailed consideration of the above security conditions, it is advisable to give an opinion: to protect against unauthorized entry and information leakage, it is proposed to use firewalls or firewalls. In fact, a firewall is a gateway that performs the functions of protecting the network from unauthorized access from outside (for example, from another network).

There are three types of firewalls:

Application layer gateway Application layer gateway is often called a proxy server (proxy server) - performs the functions of a data relay for a limited number of user applications. That is, if the gateway does not support one or another application, then the corresponding service is not provided, and data of the corresponding type cannot pass through the firewall.

filtering router. filter router. More specifically, it is a router additional functions which includes packet filtering (packet-filtering router). Used on packet-switched networks in datagram mode. That is, in those technologies for transmitting information on communication networks in which there is no signaling plane (pre-establishment of a connection between UI and UE) (for example, IP V 4). In this case, the decision to transfer an incoming data packet over the network is based on the values ​​of its transport header fields. Therefore, firewalls of this type are usually implemented as a list of rules applied to the values ​​of the transport header fields.

Switch layer gateway. Switching level gateway - protection is implemented in the control plane (at the signaling level) by allowing or denying certain connections.

A special place is given to the cryptographic protection of information resources in corporate networks. Since encryption is one of the most reliable ways to protect data from unauthorized access. A feature of the use of cryptographic means is strict legislative regulation. Currently, in corporate networks, they are installed only at those workplaces where information of a very high degree of importance is stored.

So, according to the classification of means of cryptographic protection of information resources in corporate networks, they are divided into:

Single-key cryptosystems, often referred to as traditional, symmetric, or single-key cryptosystems. The user creates an open message, the elements of which are the characters of the final alphabet. An encryption key is generated to encrypt the open message. Using the encryption algorithm, an encrypted message is generated

The above model assumes that the encryption key is generated in the same place as the message itself. However, another key generation solution is also possible - the encryption key is generated by a third party (key distribution center) trusted by both users. In this case, a third party is responsible for delivering the key to both users. Generally speaking, this decision contradicts the very essence of cryptography - ensuring the secrecy of transmitted user information.

Cryptosystems with one key use the principles of substitution (replacement), permutation (transposition) and composition. Substitution replaces individual characters in the open message with other characters. Permutation encryption involves changing the order of characters in an open message. In order to increase the strength of encryption, an encrypted message received using a certain cipher can be encrypted again using another cipher. They say that in this case a compositional approach is applied. Therefore, symmetric cryptosystems (with one key) can be classified into systems that use substitution, permutation, and composition ciphers.

Public key cryptosystem. It takes place only if users use different keys KO and K3 when encrypting and decrypting. This cryptosystem is called asymmetric, with two keys or with a public key.

The recipient of the message (user 2) generates an associated key pair:

KO - public key, which is publicly available and, thus, is available to the sender of the message (user 1);

KS is a secret, private key that remains known only to the recipient of the message (user 1).

User 1, having the encryption key KO, generates a cipher text using a certain encryption algorithm.

User 2, having the secret key Kc, has the opportunity to perform the opposite action.

In this case, user 1 prepares a message for user 2 and encrypts this message with the private key KS before sending. User 2 can decrypt this message using the public key KO. Since the message was encrypted with the sender's private key, it can act as a digital signature. In addition, in this case it is impossible to change the message without access to the private key of user 1, so the message also solves the problems of sender identification and data integrity.

Finally, I would like to say that by installing cryptographic means of protection, it is possible to reliably protect the workplace of an employee of an organization who directly works with information that has special meaning for the existence of this organization, from unauthorized access.

Ministry of Education and Science of the Russian Federation

Federal State Institution of Higher vocational education

Russian University of Chemical Technology D. I. Mendeleev

Faculty of Petroleum Chemistry and Polymeric Materials

Department of Chemical Technology of Carbon Materials

PRACTICE REPORT

on the topic CARBON NANOTUBES AND NANOVOLKS

Completed by: Marinin S. D.

Checked by: Doctor of Chemical Sciences, Bukharkina T.V.

Moscow, 2013

Introduction

The field of nanotechnology is considered worldwide key theme for 21st century technologies. The possibilities of their versatile application in such areas of the economy as the production of semiconductors, medicine, sensor technology, ecology, automotive, building materials, biotechnology, chemistry, aviation and aerospace, mechanical engineering and the textile industry, carry a huge potential for growth. The use of nanotechnology products will save on raw materials and energy consumption, reduce emissions into the atmosphere and thus contribute to the sustainable development of the economy.

Developments in the field of nanotechnologies are carried out by a new interdisciplinary field - nanoscience, one of the areas of which is nanochemistry. Nanochemistry arose at the turn of the century, when it seemed that everything in chemistry was already open, everything was clear, and all that remained was to use the acquired knowledge for the benefit of society.

Chemists have always known and well understood the importance of atoms and molecules as the basic building blocks of a huge chemical foundation. At the same time, the development of new research methods, such as electron microscopy, highly selective mass spectroscopy, in combination with special sample preparation methods, made it possible to obtain information on particles containing a small, less than a hundred, number of atoms.

These particles, about 1 nm in size (10-9 m is just a millimeter divided by a million), have unusual, hard-to-predict chemical properties.

The most famous and understandable for most people are the following nanostructures such as fullerenes, graphene, carbon nanotubes and nanofibers. They all consist of carbon atoms bonded to each other, but their shape varies significantly. Graphene is a plane, monolayer, "veil" of carbon atoms in SP 2 hybridization. Fullerenes are closed polygons, somewhat reminiscent of a soccer ball. Nanotubes are cylindrical hollow volumetric bodies. Nanofibers can be cones, cylinders, bowls. In my work, I will try to highlight exactly nanotubes and nanofibers.

Structure of nanotubes and nanofibers

What are carbon nanotubes? Carbon nanotubes are a carbon material, which is a cylindrical structure with a diameter of several nanometers, consisting of graphite planes rolled into a tube. The graphite plane is a continuous hexagonal grid with carbon atoms at the vertices of the hexagons. Carbon nanotubes can vary in length, diameter, chirality (symmetries of the rolled graphite plane), and number of layers. Chirality<#"280" src="doc_zip1.jpg" />

Single-walled nanotubes. Single-walled carbon nanotubes (SWCNTs) are a subspecies of carbon nanofibers with a structure formed by folding graphene into a cylinder with its sides joined without a seam. Rolling graphene into a cylinder without a seam is only possible in a finite number of ways, differing in the direction of the two-dimensional vector that connects two equivalent points on graphene that coincide when it is rolled into a cylinder. This vector is called the chirality vector single-layer carbon nanotube. Thus, single-walled carbon nanotubes differ in diameter and chirality. The diameter of single-walled nanotubes, according to experimental data, varies from ~ 0.7 nm to ~ 3-4 nm. The length of a single-walled nanotube can reach 4 cm. There are three forms of SWCNTs: achiral "chair" type (two sides of each hexagon are oriented perpendicular to the CNT axis), achiral "zigzag" type (two sides of each hexagon are oriented parallel to the CNT axis), and chiral or helical (each the side of the hexagon is located to the CNT axis at an angle other than 0 and 90 º ). Thus, achiral CNTs of the “armchair” type are characterized by indices (n, n), of the “zigzag” type - (n, 0), chiral - (n, m).

Multiwalled nanotubes. Multilayer carbon nanotubes (MWCNTs) are a subspecies of carbon nanofibers with a structure formed by several nested single-layer carbon nanotubes (see Fig. 2). The outer diameter of multiwalled nanotubes varies over a wide range from a few nanometers to tens of nanometers.

The number of layers in an MWCNT is most often no more than 10, but in individual cases reaches several tens.

Sometimes, among multilayer nanotubes, two-layer nanotubes are singled out as a special type. The “Russian dolls” type structure is a set of coaxially nested cylindrical tubes. Another type of this structure is a set of nested coaxial prisms. Finally, the last of these structures resembles a scroll (scroll). For all structures in Fig. characteristic value of the distance between adjacent graphene layers, close to the value of 0.34 nm, inherent in the distance between adjacent planes of crystalline graphite<#"128" src="doc_zip3.jpg" />

Russian Matryoshka Roll Papier-mache

Carbon nanofibers (CNFs) are a class of materials in which curved graphene layers or nanocones are folded into a one-dimensional filament whose internal structure can be characterized by an angle? between the graphene layers and the fiber axis. One common distinction is between the two main fiber types: Herringbone, with densely packed conical graphene layers and large α, and Bamboo, with cylindrical cup-like graphene layers and small α, which are more like multiwalled carbon nanotubes.<#"228" src="doc_zip4.jpg" />

a - nanofiber "coin column";

b - "Christmas tree structure" nanofiber (stack of cones, "fish bone");

c - nanofiber "stack of cups" ("lamp shades");

d - nanotube "Russian matryoshka";

e - bamboo-shaped nanofiber;

e - nanofiber with spherical sections;

g - nanofiber with polyhedral sections

The isolation of carbon nanotubes as a separate subspecies is due to the fact that their properties differ markedly in better side from the properties of other types of carbon nanofibers. This is explained by the fact that the graphene layer, which forms the nanotube wall along its entire length, has high tensile strength, thermal and electrical conductivity. In contrast to this, transitions from one graphene layer to another occur in carbon nanofibers moving along the wall. The presence of interlayer contacts and high defectiveness of the structure of nanofibers significantly impairs their physical characteristics.

Story

It is difficult to talk about the history of nanotubes and nanofibers separately, because these products often accompany each other during synthesis. One of the first data on the production of carbon nanofibers is probably an 1889 patent for the production of tubular forms of carbon formed during the pyrolysis of a mixture of CH4 and H2 in an iron crucible by Hughes and Chambers. They used a mixture of methane and hydrogen to grow carbon filaments by pyrolysis of the gas, followed by carbon precipitation. It became possible to talk about obtaining these fibers for sure much later, when it became possible to study their structure using an electron microscope. The first observation of carbon nanofibers using electron microscopy was made in the early 1950s by Soviet scientists Radushkevich and Lukyanovich, who published an article in the Soviet Journal physical chemistry, which showed hollow graphitic fibers of carbon that were 50 nanometers in diameter. In the early 1970s, Japanese researchers Koyama and Endo succeeded in producing carbon fibers by vapor deposition (VGCF) with a diameter of 1 µm and a length of more than 1 mm. Later, in the early 1980s, Tibbets in the USA and Benissad in France continued to improve the carbon fiber (VGCF) process. In the USA, more in-depth research into the synthesis and properties of these materials for practical applications was carried out by R. Terry K. Baker and was motivated by the need to suppress the growth of carbon nanofibers due to persistent problems caused by material accumulation in various commercial processes, especially in the field of oil refining. . The first attempt to commercialize carbon fibers grown from the gas phase was made by the Japanese company Nikosso in 1991 under the brand name Grasker, in the same year Ijima published his famous article reporting the discovery of carbon nanotubes.<#"justify">Receipt

Currently, syntheses based on pyrolysis of hydrocarbons and sublimation and desublimation of graphite are mainly used.

Sublimation-desublimation of graphitecan be implemented in several ways:

• arc method,
• radiant heating (use of solar concentrators or laser radiation),
• laser-thermal,
• heating with an electron or ion beam,
• plasma sublimation,
• resistive heating.

Many of these options have their own variations. The hierarchy of some variants of the electric arc method is shown in the diagram:

At present, the method of thermal spraying of graphite electrodes in plasma is the most common. arc discharge. The synthesis process is carried out in a chamber filled with helium at a pressure of about 500 mm Hg. Art. During plasma combustion, intense thermal evaporation of the anode occurs, while a deposit is formed on the end surface of the cathode, in which carbon nanotubes are formed. Maximum amount nanotubes are formed when the plasma current is minimal and its density is about 100 A/cm2. In experimental setups, the voltage between the electrodes is about 15–25 V, the discharge current is several tens of amperes, and the distance between the ends of the graphite electrodes is 1–2 mm. During the synthesis process, about 90% of the mass of the anode is deposited on the cathode. The resulting numerous nanotubes have a length of about 40 μm. They grow perpendicular to the cathode flat surface its end face and are collected into cylindrical bundles with a diameter of about 50 μm.

Nanotube bundles regularly coat the cathode surface, forming a honeycomb structure. The content of nanotubes in the carbon deposit is about 60%. To separate the components, the resulting precipitate is placed in methanol and sonicated. The result is a suspension which, after the addition of water, is subjected to separation in a centrifuge. Large particles adhere to the walls of the centrifuge, while the nanotubes remain floating in suspension. Then the nanotubes are washed in nitric acid and dried in a gaseous flow of oxygen and hydrogen in a ratio of 1:4 at a temperature of 750 0C for 5 minutes. As a result of such processing, a light porous material is obtained, consisting of numerous nanotubes with an average diameter of 20 nm and a length of 10 μm. So far, the maximum nanofiber length achieved is 1 cm.

Pyrolysis of hydrocarbons

In terms of the choice of initial reagents and methods of conducting processes, this group has a significantly larger number of options than the methods of sublimation and desublimation of graphite. It provides more precise control over the process of CNT formation, is more suitable for large-scale production and allows the production of not only carbon nanomaterials themselves, but also certain structures on substrates, macroscopic fibers consisting of nanotubes, as well as composite materials, in particular, modified with carbon CNTs. carbon fibers and carbon paper, ceramic composites. Using the recently developed nanospheric lithography, it was possible to obtain photonic crystals from CNTs. In this way, it is possible to isolate CNTs of a certain diameter and length.

The advantages of the pyrolytic method, in addition, include the possibility of its implementation for matrix synthesis, for example, using porous alumina membranes or molecular sieves. Using aluminum oxide, it is possible to obtain branched CNTs and CNT membranes. The main disadvantages matrix method are high price many matrices, their small size and the need to use active reagents and harsh conditions for the dissolution of matrices.

The pyrolysis of three hydrocarbons, methane, acetylene, and benzene, as well as the thermal decomposition (disproportionation) of CO are most often used for the synthesis of CNTs and CNFs. Methane, like carbon monoxide, is not prone to decomposition at low temperatures (non-catalytic decomposition of methane begins at ~900 about C), which makes it possible to synthesize SWCNTs with a relatively small amount of amorphous carbon impurities. Carbon monoxide does not decompose at low temperatures for another reason: kinetic. The difference in the behavior of various substances is visible in Fig. 94.

The advantages of methane over other hydrocarbons and carbon monoxide include the fact that its pyrolysis with the formation of CNTs or CNFs is combined with the release of H 2and can be used in existing H2 production .

Catalysts

The catalysts for the formation of CNTs and CNFs are Fe, Co, and Ni; promoters, which are introduced in smaller amounts, are mainly Mo, W or Cr (less often - V, Mn, Pt and Pd), catalyst carriers are non-volatile oxides and hydroxides of metals (Mg, Ca, Al, La, Si, Ti, Zr) , solid solutions, some salts and minerals (carbonates, spinels, perovskites, hydrotalcite, natural clays, diatomites), molecular sieves (in particular, zeolites), silica gel, airgel, aluminum gel, porous Si and amorphous C. At the same time, V, Cr, Mo, W, Mn and, probably, some other metals under pyrolysis conditions are in the form of compounds - oxides, carbides, metallates, etc.

Noble metals (Pd, Ru, PdSe), alloys (mischmetal, permalloy, nichrome, monel, stainless steel, Co-V, Fe-Cr, Fe-Sn, Fe-Ni-Cr, Fe-Ni- C, Co-Fe-Ni, hard alloy Co-WC, etc.), CoSi 2and CoGe 2, LaNi 5, MmNi 5(Mm - mischmetal), alloys of Zr and other hydride-forming metals. On the contrary, Au and Ag inhibit the formation of CNTs.

Catalysts can be deposited on silicon coated with a thin oxide film, on germanium, some types of glass, and substrates made of other materials.

Porous silicon obtained by electrochemical etching of single-crystal silicon in a solution of a certain composition is considered to be an ideal catalyst carrier. Porous silicon may contain micropores (< 2 нм), мезопоры и макропоры (>100 nm). To obtain catalysts, traditional methods are used:

• mixing (rarely sintering) of powders;
• deposition or electrochemical deposition of metals on a substrate, followed by the transformation of a continuous thin film into islands of nanosize (layer-by-layer deposition of several metals is also used;
• chemical vapor deposition;
• dipping the substrate into the solution;
• applying a suspension of catalyst particles to a substrate;
• applying the solution to a rotating substrate;
• impregnation of inert powders with salts;
• coprecipitation of oxides or hydroxides;
• ion exchange;
• colloidal methods (sol-gel process, reverse micelles method);
• thermal decomposition of salts;
• combustion of metal nitrates.

In addition to the two groups described above, a large number of other methods for obtaining CNTs have been developed. They can be classified according to the carbon sources used. The starting compounds are: graphite and other forms of solid carbon, organic compounds, inorganic compounds, organometallic compounds. Graphite can be converted into CNTs in several ways: by intense ball milling followed by high-temperature annealing; electrolysis of molten salts; splitting into separate graphene sheets and subsequent spontaneous twisting of these sheets. Amorphous carbon can be converted into CNTs when processed under hydrothermal conditions. CNTs were obtained from carbon black (soot) by high-temperature transformation with or without catalysts, as well as by interaction with water vapor under pressure. Nanotubular structures are contained in products of vacuum annealing (1000 about C) films of diamond-like carbon in the presence of a catalyst. Finally, the catalytic high-temperature transformation of fullerite C 60or its treatment under hydrothermal conditions also leads to the formation of CNTs.

Carbon nanotubes exist in nature. A group of Mexican researchers found them in oil samples taken from a depth of 5.6 km (Velasco-Santos, 2003). The CNT diameter ranged from several nanometers to tens of nanometers, and the length reached 2 μm. Some of them were filled with various nanoparticles.

Purification of carbon nanotubes

None of the common methods for obtaining CNTs allows them to be isolated in their pure form. Impurities to NT can be fullerenes, amorphous carbon, graphitized particles, catalyst particles.

There are three groups of CNT cleaning methods:

1. destructive,
2. non-destructive,
3. combined.

Destructive methods use chemical reactions, which can be oxidative or reductive and are based on differences in reactivity various carbon molds. For oxidation, either solutions of oxidizing agents or gaseous reagents are used; for reduction, hydrogen is used. The methods make it possible to isolate high-purity CNTs, but are associated with the loss of tubes.

Non-destructive methods include extraction, flocculation and selective precipitation, cross-flow microfiltration, exclusion chromatography, electrophoresis, selective reaction with organic polymers. As a rule, these methods are inefficient and inefficient.

Properties of carbon nanotubes

Mechanical. Nanotubes, as was said, are an extremely strong material, both in tension and in bending. Moreover, under the action of mechanical stresses exceeding the critical ones, nanotubes do not "break", but are rearranged. Based on such a property of nanotubes as high strength, it can be argued that they are the best material for a space elevator cable on this moment. As the results of experiments and numerical simulation show, the Young's modulus of a single-layer nanotube reaches values ​​of the order of 1-5 TPa, which is an order of magnitude greater than that of steel. The graph below shows a comparison between a single-walled nanotube and high-strength steel.

The cable of the space elevator is estimated to withstand a mechanical stress of 62.5 GPa

Tensile diagram (dependence of mechanical stress ? from relative elongation?)

To demonstrate the significant difference between the most durable on this moment materials and carbon nanotubes, let's do the following thought experiment. Imagine that, as it was assumed earlier, a certain wedge-shaped homogeneous structure consisting of the most durable materials to date will serve as a cable for a space elevator, then the diameter of the cable at GEO (geostationary Earth orbit) will be about 2 km and will narrow to 1 mm at the surface Earth. In this case, the total mass will be 60 * 1010 tons. If carbon nanotubes were used as the material, then the diameter of the cable at GEO was 0.26 mm and 0.15 mm at the Earth's surface, and therefore the total mass was 9.2 tons. As can be seen from the above facts, carbon nanofiber is exactly the material that is needed to build a cable, the actual diameter of which will be about 0.75 m, in order to withstand also the electromagnetic system used to propel the space elevator car.

Electrical. Due to the small size of carbon nanotubes, only in 1996 was it possible to directly measure their specific electrical resistance four way method.

Gold stripes were deposited on a polished silicon oxide surface in a vacuum. Nanotubes 2–3 µm long were deposited between them. Then, four tungsten conductors 80 nm thick were deposited on one of the nanotubes chosen for measurement. Each of the tungsten conductors had contact with one of the gold strips. The distance between contacts on the nanotube was from 0.3 to 1 μm. Direct measurements showed that resistivity nanotubes can vary significantly - from 5.1 * 10 -6up to 0.8 ohm/cm. The minimum resistivity is an order of magnitude lower than that of graphite. Most of nanotubes have metallic conductivity, and the smaller one exhibits the properties of a semiconductor with a band gap of 0.1 to 0.3 eV.

French and Russian researchers (from IPTM RAS, Chernogolovka) discovered another property of nanotubes, which is superconductivity. They measured the current-voltage characteristics of an individual single-walled nanotube with a diameter of ~1 nm, rolled into a bundle of a large number of single-walled nanotubes, as well as individual multilayer nanotubes. A superconducting current at a temperature close to 4K was observed between two superconducting metal contacts. The features of charge transfer in a nanotube essentially differ from those that are inherent in ordinary, three-dimensional conductors and, apparently, are explained by the one-dimensional nature of the transfer.

Also, de Girom from the University of Lausanne (Switzerland) discovered an interesting property: a sharp (about two orders of magnitude) change in conductivity with a small, by 5-10o, bending of a single-layer nanotube. This property can expand the scope of nanotubes. On the one hand, the nanotube turns out to be a ready-made highly sensitive transducer mechanical vibrations into an electrical signal and back (in fact, it is a telephone receiver a few microns long and about a nanometer in diameter), and, on the other hand, it is an almost ready-made sensor of the smallest deformations. Such a sensor could be used in devices that monitor the state of mechanical components and parts on which the safety of people depends, for example, passengers of trains and aircraft, personnel of nuclear and thermal power plants, etc.

Capillary. Experiments have shown that an open nanotube has capillary properties. To open a nanotube, one must remove upper part- a cap. One way to remove is to anneal nanotubes at a temperature of 850 0C for several hours in a stream of carbon dioxide. As a result of oxidation, about 10% of all nanotubes are open. Another way to destroy the closed ends of nanotubes is exposure to concentrated nitric acid for 4.5 hours at a temperature of 2400 C. As a result of this treatment, 80% of the nanotubes become open.

The first studies of capillary phenomena showed that a liquid penetrates into the nanotube channel if its surface tension is not higher than 200 mN/m. Therefore, to introduce any substances into nanotubes, solvents with a low surface tension are used. For example, concentrated nitric acid, the surface tension of which is low (43 mN/m), is used to introduce certain metals into the nanotube channel. Then annealing is carried out at 4000 C for 4 hours in a hydrogen atmosphere, which leads to the reduction of the metal. In this way, nanotubes containing nickel, cobalt, and iron were obtained.

Along with metals, carbon nanotubes can be filled gaseous substances, such as hydrogen in molecular form. This ability is of practical importance, because it opens up the possibility of safe storage of hydrogen, which can be used as an environmentally friendly fuel in engines. internal combustion. Also, scientists were able to place a whole chain of fullerenes with gadolinium atoms already embedded in them (see Fig. 5).

Rice. 5. Inside C60 inside a single-walled nanotube

Capillary effects and filling of nanotubes

nanotube carbon pyrolysis electric arc

Soon after the discovery of carbon nanotubes, the attention of researchers was attracted by the possibility of filling nanotubes with various substances, which is not only of scientific interest, but also of great importance for applied problems, since a nanotube filled with a conducting, semiconducting, or superconducting material can be considered as the smallest of all known nanotubes. present time elements of microelectronics. Scientific interest in this problem is associated with the possibility of obtaining an experimentally substantiated answer to the question: at what minimum sizes do capillary phenomena retain their features inherent in macroscopic objects? For the first time, this problem was considered in the problem of the retraction of an HP molecule inside nanotubes under the action of polarization forces. It was shown that the capillary phenomena leading to the drawing of liquids that wet the inner surface of the tube into the capillary retain their nature upon transition to nanometer-diameter tubes.

Capillary phenomena in carbon nanotubes were first experimentally carried out in a work where the effect of capillary retraction of molten lead into nanotubes was observed. In this experiment, an electric arc intended for the synthesis of nanotubes was ignited between electrodes with a diameter of 0.8 and a length of 15 cm at a voltage of 30 V and a current of 180–200 A. A layer of material 3–4 cm high formed on the cathode surface as a result of thermal destruction of the anode surface was removed from the chamber and kept for 5 h at T = 850°C in a flow of carbon dioxide. This operation, as a result of which the sample lost about 10% of the mass, contributed to the purification of the sample from particles of amorphous graphite and the discovery of nanotubes in the precipitate. The central part of the precipitate containing nanotubes was placed in ethanol and sonicated. The oxidation product dispersed in chloroform was applied to a carbon tape with holes for observation with an electron microscope. As observations showed, the tubes that were not subjected to processing had a seamless structure, heads of the correct shape and a diameter of 0.8 to 10 nm. As a result of oxidation, about 10% of the nanotubes turned out to have damaged caps, and some of the layers near the top were torn off. A sample containing nanotubes intended for observation was filled in vacuum with drops of molten lead, which were obtained by irradiating a metal surface with an electron beam. In this case, lead droplets 1 to 15 nm in size were observed on the outer surface of the nanotubes. The nanotubes were annealed in air at Т = 400°С (above the melting point of lead) for 30 min. According to the results of observations made with an electron microscope, after annealing, some of the nanotubes turned out to be filled with a solid material. A similar effect of filling nanotubes was observed when the heads of the tubes opened as a result of annealing were irradiated with a powerful electron beam. With a sufficiently strong irradiation, the material near the open end of the tube melts and penetrates inside. The presence of lead inside the tubes was established by X-ray diffraction and electron spectroscopy. The diameter of the thinnest lead wire was 1.5 nm. According to the results of observations, the number of filled nanotubes did not exceed 1%.

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